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Ann Thorac Surg 2003;75:620-632
© 2003 The Society of Thoracic Surgeons

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Review

Obstructive hypertrophic cardiomyopathy: echocardiography, pathophysiology, and the continuing evolution of surgery for obstruction

^a Division of Cardiology, St. Luke’s-Roosevelt Hospital Center, Columbia University, College of Physicians and Surgeons, New York, NY, USA
^b Division of Cardiovascular and Thoracic Surgery, St. Luke’s-Roosevelt Hospital Center, Columbia University, College of Physicians and Surgeons, New York, New York, USA

* Address reprint requests to Dr Sherrid, Division of Cardiology, 3B-30, 1000 Tenth Avenue, New York, NY 10019, USA
e-mail: msherrid{at}slrhc.org

	Abstract

Top Abstract Introduction Dynamic outflow tract... Systolic anterior motion and... Flow drag, the pushing... Surgical approach Review of HCM diversity,... References

 
Our understanding of the pathophysiology of obstruction in hypertrophic cardiomyopathy has evolved since initial descriptions in the late 1950s. This review addresses the cause of obstruction, from early ideas that a muscular outflow tract sphincter was the cause, through the discovery of systolic anterior motion (SAM) of the mitral valve, to current understanding that flow drag, the pushing force of flow, is the dominant hydrodynamic mechanism for SAM. The continuing redesign and modification of surgical procedures to relieve outflow obstruction have corresponded to ideas about the cause of this condition. In this review we discuss the evolution of surgical procedures to relieve obstruction and review modern surgical approaches. Medical and nonsurgical methods for reducing obstruction are reviewed, as well as efforts to prevent sudden arrhythmic cardiac death. Echocardiography has become central to understanding this complex phenomenon, and for clinical diagnosis, operative planning and intraoperative management.

	Introduction

Top Abstract Introduction Dynamic outflow tract... Systolic anterior motion and... Flow drag, the pushing... Surgical approach Review of HCM diversity,... References

 

. . . but also relieves the obstructive component of the mitral valve, which is rarely due to the often cited and never proved Venturi effect but has its origin rather in pathologic insertion and position of the subvalvular mitral apparatus and papillary muscles, respectively [1].

Surgery to relieve obstruction in hypertrophic cardiomyopathy (HCM) can be among the more technically challenging of cardiac operations for acquired disease [2–18]. The conventional procedure, septal myectomy can be difficult for several reasons. First, exposure to the septal bulge is limited because access is commonly through the aortotomy. Part of the septal bulge cannot be easily seen by the surgeon, and yet, it is precisely here that one is called upon to cut. Doctor Andrew Morrow, a pioneer of the myectomy wrote "the incisions are made quite close to the seat of the soul" [2]. This problem with exposure may lead to imprecision in the extent of myectomy that may lead to either an inadequate small resection with persistent obstruction [19], or too large, and a ventricular septal defect or complete heart block. Ventricular septal defect has been reported in 0% to 2% of reports from 1987 to 1996 [5–18], and higher in operations performed on the elderly, 6%, or with simultaneous coronary bypass grafting, 8% [20, 21]. Perhaps as a consequence, surgery for HCM has become concentrated in a few centers with superior results, which have accumulated a large experience, while the operation is avoided at centers with limited experience.

A second difficulty of operations for obstructive HCM has perhaps been due to misunderstanding the pathophysiology of obstruction. Appreciation of the mechanism of obstruction in HCM has evolved with improvement in real time cardiac imaging, specifically echocardiography.

This review discusses the progress of our understanding about the cause of obstruction and the concurrent surgical procedures that have been devised to correspond with ideas about this complex phenomenon. We review the modern surgical approaches for this condition. The long-term benefit of surgery, and also the nonsurgical septal reduction to which it is being compared, will depend on the extent that they rectify abnormal pathophysiology [22].

	Dynamic outflow tract obstruction due to a muscular sphincter: myotomy and limited myectomy

Top Abstract Introduction Dynamic outflow tract... Systolic anterior motion and... Flow drag, the pushing... Surgical approach Review of HCM diversity,... References

 
Brock’s initial reports [23] of muscular hypertrophy of the left ventricular outflow tract (LVOT) led to the idea that a myotomy would interrupt the septal muscle bundles of a sphincterlike contraction ring surrounding the outflow tract, and relieve obstruction. Brock’s notion was that dynamic LVOT obstruction was similar in mechanism to right ventricular infundibular narrowing. Hence, in many early reports the condition was named muscular subaortic stenosis [24, 25]. Cleland [26] and others [24, 25, 27] began the surgical treatment of obstructive HCM with myotomy or limited excision myectomy through the transaortic approach as early as 1958. Though remarkable reductions in gradient were observed in the majority of myotomy patients, in-hospital mortality was high and in some patients obstruction persisted. Morrow’s modification of the initial procedures, the wider more extensive trough myectomy, consistently decreased obstruction and has remained the standard operation [28] (see Fig 1).

View larger version (40K): [in this window] [in a new window]   Fig 1. The trough myectomy of Morrow Flat, narrow, malleable retractors are placed over the mitral valve to protect leaflet and chordae. External pressure is placed on the right ventricle, and thus the septum, to push the septal bulge into view. A knife with a bent handle is used to facilitate exposure of the septal bulge. (Reprinted from Morrow AG, et al, Circulation; 1975;52:88–102, with permission.)

	Systolic anterior motion and mitral-septal contact: trough myectomy of morrow

Top Abstract Introduction Dynamic outflow tract... Systolic anterior motion and... Flow drag, the pushing... Surgical approach Review of HCM diversity,... References

For many years SAM was thought to be due to the subaortic septal bulge narrowing the outflow tract with consequent high velocity flow resulting in a Venturi effect, a local underpressure. This low pressure was thought to suck the mitral valve anteriorly into the septum. With this model in mind, surgical resection focused on the subaortic septum to increase the size of the outflow tract to reduce the Venturi forces. This sort of resection may still be inadequate to abolish SAM [19] because the magnitude and importance of the Venturi forces are much less than previously thought [33–40].

	Flow drag, the pushing force of flow: procedures address the problem of the mitral valve and separate the inflow and outflow portions of the left ventricle

Top Abstract Introduction Dynamic outflow tract... Systolic anterior motion and... Flow drag, the pushing... Surgical approach Review of HCM diversity,... References

 
Recent echocardiographic evidence, including data from our laboratory, indicates that drag, the pushing force of flow, is the dominant hydrodynamic force on the mitral leaflets [33–39]. The dominance of drag, the pushing force, is supported by echocardiographic geometric, temporal, and velocity evidence. Geometric evidence–in obstructive HCM demonstrates the mitral leaflets are often large and anteriorly positioned in the LV cavity [40–44]. Jiang, Levine, and coworkers [33] observed anterior position of the papillary muscles in the left ventricular cavity. The importance of this anterior position was recognized in the operating room as early as 1974 [40]. At surgery the hypertrophied papillary muscles are "agglutinated" onto the LV walls and are often fused to each other [1, 16]. Anterior position of the papillary muscles leads to an anteriorly positioned coaptation plane of the mitral valve [1, 16, 33, 36–41]. The midseptal bulge protrudes posteriorly and laterally and aggravates the malposition of the valve relative to outflow (see Fig 2). The midseptal bulge redirects outflow direction so that it comes from a lateral and posterior direction [34, 37, 40]. The abnormally directed outflow gets behind and lateral to the enlarged mitral valve, catches it, and pushes it into the septum [33–39]. There is a crucial overlap between the inflow and outflow portions of the left ventricle [38].

View larger version (64K): [in this window] [in a new window]   Fig 2. The pushing force of flow. (A) Early systolic ejection flow relative to the mitral valve in the apical 5-chamber view. In obstructive hypertrophic cardiomyopathy (HCM) the mitral leaflet coaptation point is closer to the septum than normal [41]. The protruding leaflets extend into the edge of the flowstream and are swept by the pushing force of flow toward the septum. Flow pushes the underside of the leaflets (arrow) [33–40]. Note that the midseptal bulge redirects flow so that it comes from a relatively lateral and posterior direction; on the 5-chamber view, flow comes from "right field" or "one o’clock" direction [37, 40]. This contributes to the high angle of attack relative to the protruding leaflets. Also note that the posterior leaflet is shielded and separated from outflow tract flow by the cowl of the anterior leaflet. Venturi flow in the outflow tract cannot be lifting the posterior leaflet because there is little or no area of this leaflet exposed to outflow tract flow. Venturi forces cannot be causing the anterior motion of the posterior leaflet. (B and C) Two apical 5-chamber echocardiographic views of one patient with obstructive HCM are illustrated; resting gradient = 54 mm Hg. (B) Two-dimensional illustration reveals the protruding mitral leaflet on the first frame in systole that demonstrated mitral coaptation. White arrowhead points to the mitral valve. On the next sequential frame there was fully developed systolic anterior motion. (C) Illustration of the same view of the first systolic frame with color flow. Color flow is seen lateral to the leaflet tips (arrow). Color flow velocity is quite low. On the next frame there was aliased high velocity flow. These images demonstrate the event graphically drawn in the left panel. Early in systole, flow pushes the underside of the mitral leaflets and pushes them into the septum. (MV = mitral valve; OT = outflow tract; SB = septal bulge.) (Reprinted with permission from the American College of Cardiology Foundation Journal of the American College of Cardiology, 2000, 36, 1344 [37].)

Temporal evidence–SAM begins before systolic ejection in two-thirds of patients, before high velocity occurs [33, 37]. Velocity evidence–SAM onset is a low velocity phenomenon. It begins at a velocity no different from velocities measured in normals [37]. Hence, the Venturi force cannot be the main force that initiates SAM. A summary of evidence for the current altered understanding of the hydrodynamic cause for SAM is presented in Figure 3. SAM has been described as anteriorly directed mitral valve prolapse [37]. This analogy has merit; in both conditions the mitral valve is often large and is pushed by flow from its normal systolic position, resulting in mitral regurgitation.

View larger version (28K): [in this window] [in a new window]   Fig 3. Evidence in the debate between Venturi (lift) and drag (pushing) force as the dynamic cause for systolic anterior motion (SAM) [33–41, 45]. (ASH = asymmetric septal hypertrophy; LV = left ventricular.) (Reprinted with permission from the American College of Cardiology Foundation Journal of the American College of Cardiology, 2000, 36, 1344 [37].)

	Surgical approach

Top Abstract Introduction Dynamic outflow tract... Systolic anterior motion and... Flow drag, the pushing... Surgical approach Review of HCM diversity,... References

 
An operation focused on widening the outflow tract and lowering Venturi forces is illustrated in the second panel of Figure 4. With this resection the residual midseptal bulge still redirects flow posteriorly: SAM persists because flow still gets behind the mitral valve. In fact, as described above, resection of the subaortic bar plays a small role in relieving the obstruction and may cause a higher risk of creating a ventricular septal defect because the septum here tends to be relatively thin, even in patients with HCM. With the heart arrested, and the ventricles collapsed, the weight of the right ventricle on the septum gives the appearance of a septal bulge, just under the annulus of the aortic valve. Unfortunately, this easily accessible septum is not the area that creates the obstructive physiology. It is only when the deeper portion of the septal bulge is resected that flow is redirected medially and anteriorly away from the mitral valve, abolishing SAM [45]. With this in mind, a modification of the Morrow myectomy termed extended myectomy, mobilization, and partial excision of the papillary muscles has been performed in Aachen since the 1980s, and at St. Luke’s–Roosevelt since 1998 [1, 16]. Others have performed extensive myectomy [5, 8, 11, 15]. The way this modification helps relieve SAM pathophysiology is important.

View larger version (32K): [in this window] [in a new window]   Fig 4. Surgical separation of ventricular inflow from outflow in obstructive hypertrophic cardiomyopathy, and extended myectomy and papillary muscle mobilization. (A) Illustration of outflow relative to the mitral valve in early systole. Note the anterior position of the mitral valve coaptation. The prominent midseptal bulge redirects outflow so that it comes from a relatively posterior direction, catching the anteriorly positioned mitral valve and pushing it into the septum. (B) After subaortic septal resection. The subaortic septum has been resected, but only down to the tips of the mitral leaflets. Flow is still redirected by the remaining septal bulge so that it comes from a posterior direction. It still catches the mitral valve; systolic anterior motion persists, as does obstruction. (C) The septal bulge below the mitral leaflet tips has been resected, an extended myectomy. Now, flow tracks more anteriorly and medially, away from the mitral leaflets [45]. (D) Mobilization and partial excision of the papillary muscles is added to extended myectomy. The mitral coaptation plane is now more posterior, explicitly out of the flow stream [1, 16].

Technique
The patient is placed on cardiopulmonary bypass in the usual manner, with a single two-stage venous cannula and a coronary sinus cannula for retrograde cardioplegia. The left ventricle is vented with a 28F catheter that is introduced at the right superior pulmonary vein-left atrial junction. This provides both excellent venting and a bloodless field during the subsequent myectomy stage of the procedure. The cross-clamp is applied and antegrade and retrograde cardioplegia are delivered. We routinely measure septal temperature to assure adequate cooling of the marked hypertrophy.

We divide the surgical approach for the relief of HCM obstruction into the following three components:

Extended septal myectomy
After the aortotomy is done, stay sutures of 4–0 polypropyline are placed along the proximal edge of the aortotomy for retraction. As long as the aortic leaflets are normal, we do not place any retraction sutures on the leaflets themselves since this may lead to damage. Instead, small, flat-bladed leaflet retractors are used to displace the leaflets towards the aortic wall and out of the way. As described by Messmer [1] and Schoendube and coworkers [16], a trefoil hook retractor with a long handle is then introduced deeply into the ventricular cavity and imbedded into the farthest portion of the septal bulge with an orientation between the right coronary ostium and the right and left coronary commissure (see Fig 5). When drawn forward, a larger bulge in the septal muscle is created which lends itself to resection. The trefoil hook serves two purposes. First, it defines, in the anterior-posterior direction, the point towards which the #15 scalpel blade is pushed, and second, it stabilizes the muscle to be resected and prevents it from being pushed out and away from the blade and surgeon. Two parallel incisions are made into the bulge with the knife directed toward the prongs of the hook; the first is below the right coronary ostium and the second below the left and right coronary commissure. The two incisions are then connected by an incision between the two made roughly 3-mm below the aortic annulus. The muscle mass is then removed by extending the trough gradually into the LV lumen. We find it most important to remove as much as possible in the first attempt. Secondary resections are difficult because the muscle tissue tends to shred and the surface becomes irregular.

View larger version (68K): [in this window] [in a new window]   Fig 5. Trefoil hook to grasp the apical portion of the septal bulge. Stabilizing the position of the septal bulge with a trefoil hook retractor makes myectomy results more predictable and lessens the chance of ventricular septal defect [1, 16]. The trefoil hook retractor with a long handle is introduced deeply into the ventricular cavity and embedded into the farthest portion of the septal bulge with an orientation between the right coronary ostium and the right and left coronary commissure. When drawn forward, a larger bulge in the septal muscle is created which lends itself to resection. The trefoil hook serves two purposes. It defines, in the anterior-posterior direction, the point toward which the #15 scalpel blade is pushed, it stabilizes the muscle to be resected, and prevents it from being pushed out and away from the blade and surgeon. Two parallel incisions are made into the bulge with the knife directed toward the prongs of the hook; the first is below the right coronary ostium and the second below the left and right coronary commissure. (Arrow = direction of traction; L = left coronary ostia; RC = right coronary ostia.) (Reprinted with permission from The Society of Thoracic Surgeons [Ann Thorac Surg 1994;58:575 (1)].)

Mobilization and partial excision of the papillary muscles
This approach severs the abnormal connections that bind the papillary muscles to the anterior wall. This allows the mitral valve to assume its more normal posterior position, explicitly out of the outflow tract and its drag forces [1, 16]. Extended septal myectomy is necessary to gain exposure to the base of the papillary muscles that are otherwise obscured by the septal bulge. After the septum is resected, it becomes much easier to visualize structures within the ventricular cavity; it is now possible to see the abnormal connections that bind the papillary muscles to the anterior wall. The leaflet retractors that were earlier positioned just under the aortic valve are now pushed deeper into the ventricular cavity and the anterior papillary muscle is gently grasped with long, broad toothed forceps and pushed medially. A #15 blade is again used to divide the abnormal attachments between the papillary muscle and the anterolateral ventricular wall and a portion of the junction of the papillary muscle and lateral wall is also resected either with the #15 blade or with long Potts scissors. The same is done for the posterior papillary muscle. Often the papillary muscles are so thick that grasping them is difficult and retraction medially impossible. Messmer [1, 16] describes retraction medially of the chordae involved with a nerve hook [1] to improve visualization of the papillary muscle–lateral wall junction. We have alternatively found it simple in these instances to resect this area with a long, double action bone rongeur [13]. In these patients, the muscles involved are so thick that, with a medium sized rongeur, it is unlikely one will resect too much. Similarly, all connections that bind the papillary muscles together are resected.

When this resection is completed, the papillary muscles, with their diameters reduced, are separated from the wall and from each other and "stay like slim columns inside the ventricle" [1] (Fig 4, fourth panel). This allows the papillary muscles to assume a more posterior position in the left ventricle. This resection does not appear to compromise papillary muscle function in respect to mitral valve closure [16]. We believe that this complete mobilization is a most essential step in the relief of SAM.

Anterior mitral leaflet plication
After the two procedures above, attention is then directed to the anterior leaflet of the mitral valve [18, 48]. The mitral valve is often enlarged both in area and length in obstructive HCM, especially in its relationship to the small left ventricular cavity [42–44]. We believe this disparity is best evaluated on the preoperative transesophogeal echocardiogram (TEE) because it is difficult to completely assess this after cardiopulmonary bypass is initiated. In selected patients with large floppy valves we plicate the anterior mitral leaflet with a modification of the technique described by McIntosh and colleagues [18] and by Cooley [48]. Plication of the native anterior mitral leaflet decreases the size of the leaflet and attendant drag forces and reduces chordal and leaflet slack (see Fig 6). Plication is applied using the criteria of McIntosh when patients are judged to be at increased risk for a suboptimal hemodynamic result due to residual SAM because of increased mobility, size or length of the anterior mitral leaflet.

View larger version (38K): [in this window] [in a new window]   Fig 6. Longitudinal plication of the anterior mitral leaflet. (A and B) Anterior leaflet plication viewed from the aortotomy. Interrupted sutures are placed in the anterior leaflet starting at the distal portion of the leaflet, near its attachment with the chordae, with additional sutures placed longitudinally toward the annulus depending on changes in mobility. (Reprinted from McIntosh CL, et al, Circulation; 1992;86:II60 [18], with permission.) (C) Another depiction of longitudinal anterior leaflet plication. Here sutures are placed more centrally in the leaflet, still in a longitudinal orientation. (Reprinted from Cooley DA, J Cardiac Surg; 1991;6:29 [48], with permission.)

We prefer to perform plication by placing three to four fine mattress sutures of 5-0 polypropylene in a horizontal rather than longitudinal orientation using the fibrotic area on the leaflet for the location of the horizontal line (Fig 7). The width of the mattress sutures is dictated by the degree of redundancy of the leaflet and mobility when assessed by the nerve hook. This modification more directly reduces leaflet-chordal slack and excess length than a suture line in the longitudinal orientation. We have performed this technique in 4 of our last 11 patients. There has been no incidence of significant mitral insufficiency and we believe this adjunctive procedure has significantly contributed to obliterating SAM and postoperative outflow tract gradient in these patients.

View larger version (26K): [in this window] [in a new window]   Fig 7. Horizontal plication of the anterior mitral leaflet to reduce leaflet length and leaflet/chordal slack. The fibrotic area on the anterior leaflet that is the contact point between the leaflet and the septum is identified. Plication is performed by placing three to four fine mattress sutures of 5–0 polypropylene in a horizontal rather than longitudinal orientation through the fibrotic area of the leaflet. The width of the mattress sutures is dictated by the degree of redundancy of the leaflet and mobility when assessed by the nerve hook. This modification more directly reduces leaflet-chordal slack and excess length than a suture line in the longitudinal orientation. (Ao = aortic root; AML = anterior mitral leaflet; LCO = left main coronary ostium; NCL = noncoronary aortic leaflet.)

In its outcome, papillary muscle remodeling is analogous to the sliding leaflet modification of mitral anuloplasty procedures: both modifications result in a posterior mitral coaptation plane that prevents SAM [49]. Indeed the sliding leaflet mitral valve repair added to myectomy has been reported in rare cases of obstructive HCM [50, 51]. Placement of an annuloplasty ring could prove problematic since rings may displace the mitral valve anteriorly.

McIntosh and coworkers [18] reported on 36 selected patients with anterior leaflet plication added to myectomy because they were judged morphologically at operation to be at risk for residual SAM and obstruction. In this select group of sicker patients, postoperative gradient was reduced to mean 16 mm Hg and overall mitral regurgitation was reduced. Echocardiographic studies revealed that plication appeared to limit anterior leaflet motion and SAM.

Mitral valve replacement
Cooley [52] and others [53–55] have reported on mitral valve replacement to abolish SAM. Although this is hemodynamically successful, the patient is burdened with a prosthetic valve and its life-long risks of valve failure, embolism, infection, and warfarin-induced hemorrhage. In these series there was a significant cumulative incidence of prosthetic thrombosis and valve failure though few of these patients had the benefit of the newer mechanical mitral valves [53–55]. Sparing the native mitral valve is the preferred route [55, 56].

Mitral valve replacement is sometimes necessary. Structural abnormalities of the mitral valve may be identified with echocardiography, like prolapse or valvular calcification with immobility, which would cause significant mitral regurgitation postoperatively and thus require mitral replacement. A central or anteriorly directed mitral regurgitation jet is a clue to the presence of structural mitral regurgitation. In the absence of structural mitral regurgitation, septal myectomy with abolition of SAM markedly decreases mitral regurgitation [3, 57].

The measurement of anterior septal thickness is a particular focus of the preoperative echocardiogram. McIntosh and Maron [3] recommended that patients with septal thickness less then 18 mm be given mitral valve replacement. Of 156 patients operated on at National Institutes of Health from 1982 to 1986, 48 had mitral replacement. However, others perform myectomy on these patients without septal perforation and with abolition of SAM [6, 14, 16, 44]. In these patients, papillary muscle mobilization displaces the mitral valve posteriorly and is an important adjunct to the myectomy, which by necessity, is less extensive [16]. A rare patient will have SAM, mitral-septal contact and high gradient in the absence of significant hypertrophy. In such cases malposition and enlargement of the valve are implicated; medical therapy is tried first with mitral replacement for refractory symptoms.

	Review of HCM diversity, medical treatment, and sudden death prevention

Top Abstract Introduction Dynamic outflow tract... Systolic anterior motion and... Flow drag, the pushing... Surgical approach Review of HCM diversity,... References

 
Stepping back, it has long been recognized that the majority of HCM patients are not obstructed yet may have symptoms and be at risk for sudden cardiac death [58–61]. Symptoms in nonobstructive patients are caused by LV diastolic dysfunction and myocardial ischemia in the absence of epicardial coronary narrowings [61–65]. Ischemia, with decreased flow reserve, is thought to be due to narrowing of the intramural small coronary arteries and arterioles and inadequate capillary density for the degree of hypertrophy [61, 64, 65].

Treatment of symptoms in nonobstructive HCM is medical. Verapamil has been reported to reverse perfusion defects [66]. Alternately ß-blockers may be given with the rationale of prolonging diastole to prolong filling time. Dual chamber pacing has been applied in a distinct subgroup with hyperdynamic LV function and complete systolic cavity obliteration/emptying [67].

In recent years a most important treatment focus for HCM patients, regardless of the presence of obstruction, has been an attempt to prevent sudden arrhythmic cardiac death. Though the annual risk of sudden death in unselected HCM patients is 1%, there are subgroups of patients with higher annual risk of dying suddenly. Risk factors can be identified that predispose young patients to sudden arrhythmic death [61, 68]. The presence of one or more of these risk factors may prompt referral for a prophylactic implantable cardioverter-defibrillator. A registry of implanted patients demonstrated appropriate potentially lifesaving shocks delivered at an annual rate of 4.5% per year to patients treated with such a prophylactic strategy [69].

Obstructed patients have more severe symptoms and their systolic murmurs often bring them to medical attention [70]. Obstruction adds to the previously described HCM substrate the additional burdens of higher left ventricular systolic pressure, lower coronary perfusion pressure, contraction-load impairment of relaxation, and mitral regurgitation. Maron and colleagues [60] have reported an increase in deaths in obstructed patients due to congestive failure. Most patients with obstruction will respond to medical therapy and only a minority will require intervention for refractory obstruction [58–61]. ß-blocker is tried first. Though these agents blunt exercise-related increase in gradient they do not reduce high resting gradients [71]. Disopyramide is considered by many to be the single most efficacious agent in reducing obstruction; it reduces gradient, improve symptoms, and prolong exercise time [59, 72, 73]. It is most often used in combination with ß-blockade. Negative inotropic agents decrease gradient by decreasing left ventricular ejection acceleration and the hydrodynamic force on the mitral leaflet. This delays mitral-septal contact and the duration that the amplifying feedback loop cycles in systole, reducing the final gradient [47]. Verapamil is also used for obstruction [74]; however, it is less predictable and may be associated with cardiac side effects because of vasodilation [75].

Surgical indications and results
Patients with symptoms refractory to medication, and obstruction either at rest or with provocation, are generally referred for surgery, which is considered the gold standard for intervention because of its long successful track record [3, 22, 61]. In publications of results of myectomy from 1987 to 1999, mortality within 1 month of operation ranged from 0% to 6% [3, 5–18]. Survival of patients operated in the last 10 years have improved. In a series with 519 patients, reported by Schulte and coworkers [10], early mortality was 1.9% in patients operated on within 10 years of publication; other centers report no early mortality. Survival at 5 years has ranged from 85% to 93%, and survival at 10 years from 70% to 88% [3, 5–18]. In the large series reported by Schulte, 10-year cumulative survival was 88% [10]. Survival, both short- and long-term is better in patients who just have myectomy compared with those who also require coronary artery bypass graft or valve replacement. Postoperative resting gradient ranged from 4.5 to 16 mm Hg, excellent relief of obstruction, with parallel improvement in symptoms and NYHA classification [3, 5–18]. Need for permanent pacemaker for heart block was low, ranging from 0% to 10%. Ventricular septal defect ranged from 0% to 2%. After surgical relief of obstruction the great majority of patients have striking, prolonged relief of symptoms and improvement in quality of life. These relatively safe and efficacious results from surgery form the standard against which newer interventions to relieve obstruction are judged.

Nonsurgical interventions to relieve obstruction
In recent years two alternatives to surgery have been advanced. The main benefit of these interventions over surgery is avoidance of sternotomy and cardiopulmonary bypass. The first, DDD pacing with short atrioventricular delay to assure complete ventricular paced activation has been reported to reduce resting gradients by approximately 50% [76–79]. However, patients are left with residual gradients of 30 to 48 mm Hg on average, generally higher than that found after successful surgery. There have been two randomized crossover trials of DDD pacing that have confirmed the beneficial effect on gradient, but could not demonstrate quantifiable improvement in exercise capacity [78, 80]. In the PIC trial there was no overall prolongation of exercise time except in a subgroup of more impaired patients [78]. In the M-Pathy trial there was no overall increase in exercise time or maximal oxygen consumption [80]. Only in the subgroup of patients more than 65 years old did a higher proportion accrue a benefit of both reduction in symptoms and increase in exercise capacity. Both studies reported that, in addition to gradient reduction, pacing had a placebo effect as well [80, 81]. Thus, pacing cannot be considered a primary treatment for obstructive HCM [80]. Nevertheless, DDD pacing is still applied in patients refractory to medication who are elderly, have contraindications, or do not want surgery. A minority have individual, and currently, unpredictable substantial clinical benefit [79]. An additional benefit of pacing is the opportunity (especially in the elderly) to give more negatively inotropic medication to patients now protected against bradycardia.

Alcohol ablation of the septum
Alcohol ablation, a percutaneous catheter-based method to decrease septal thickness by therapeutic infarction, was introduced by Sigwart [82]. After a small balloon catheter is placed into a proximal septal artery, it is inflated and a small amount of echocardiographic contrast is injected into the target septal perforator to assure that the septal site of mitral-septal contact is supplied by the selected vessel [83–85]. Faber reported that 7% of initially selected vessels are abandoned because contrast is seen in nonseptal structures, such as the papillary muscles, LV free wall or right ventricle [83]. After occlusion of a septal perforator by a small balloon to prevent back leakage, 1 to 4 mL of absolute alcohol in injected into the distal perforator. The balloon is left inflated for 5 to 10 minutes to prevent back leakage of alcohol. Patients experience chest pain and modest myocardial infarction with CK elevations.

Cohort studies have reported sustained reduction in LV outflow gradients, and improvement in symptoms and exercise capacity [83–88]. Myocardial contrast echocardiography has resulted in more effective gradient reduction and a lower permanent pacemaker rate [83]. There have been two comparisons of septal ablation and surgical myectomy [89, 90]. Both of these studies were nonrandomized comparisons. The study of Nagueh and coworkers [89] matched age and gradient in an attempt to make groups comparable. Gradient reduction and symptom relief was similar with the two treatment modalities. Requirement for permanent pacemaker was higher in the ablation group, 22% versus 2% [89]. In the report of Qin and coworkers [90], study patients were selected for alcohol ablation if they were older or had other comorbid conditions. Follow-up pressure gradients were lower in the surgically treated patients and need for permanent pacing was again greater in the ablated group [90].

Mechanism of ablation benefit
Ablation appears to work in a biphasic manner. Immediately after the procedure, the pressure gradient is reduced, despite absence of alteration of the position of the mitral valve relative to the septum. This highlights the importance of the observed dynamic change in ejection acceleration [91]. The immediate postprocedure reduction in gradient is caused by an immediate reduction in LV ejection acceleration, caused the direct negative inotropic effect of the septal infarct and perhaps by LV dysynergy from RBBB [91, 92]. Immediately after alcohol ablation peak LV ejection acceleration decreased 39%; reduced acceleration was still present 6 months later, 33%. This is very similar to the 36% reduction in acceleration seen after medication that abolishes gradient [47]. The mechanism of early gradient reduction after ablation is similar to that of medication: reduced LV ejection acceleration.

Six weeks and 6 months later, decreased acceleration persists, but now in addition, septal thinning and increase in the LV outflow tract diameter is seen, very similar to surgical results; flow is directed anteriorly and medially away from the mitral valve [91]. Anatomic and dynamic effects are synergistic in reducing SAM.

Complications of ablation include death in 0% to 4%, LAD dissection, leakage of alcohol back into the LAD with LAD occlusion and large infarction, and complete heart block in 9% to 38% [82, 85–88]. There is concern about the possible late development of an arrhythmogenic scar at the site of the infarction in patients already prone to arrhythmia [61]. In this regard there has been relatively short follow-up of ablated patients (3 to 5 years) compared with surgically treated patients; and, there have been few pathologic examinations of the site of alcohol ablated septa [86, 93]. In light of the short follow-up intervals and uncertain long-term results compared with surgery, alcohol ablation should be done under protocol. Expertise not only with percutaneous catheter techniques but with the pathophysiology and medical management of patients with hypertrophic cardiomyopathy is requisite [61].

From encouraging results it appears likely that alcohol ablation will have a role in the management of selected patients with refractory symptoms and refractory gradients. There are drawbacks and benefits of both procedures [22, 90]. A randomized trial of surgery versus alcohol ablation would answer questions about the relative merits of the two techniques and perhaps identify factors such as age, anatomy, and associated conditions that would sway referral one way or the other.

From the above discussions there are three therapeutic approaches that have reduced SAM and gradient: decreasing left ventricular ejection acceleration, redirecting ejection flow anteriorly and medially away from the valve to decrease angle of attack of flow onto the valve, and reducing chordal slack [18, 33–38, 40, 45, 47, 91].

After relief of obstruction from either surgery or septal ablation medications are reduced and in many cases eliminated. Some patients require continued antiarrhythmic medication or negative inotropic agents for residual, though decreased, gradients.

Midventricular obstruction
The level of LV obstruction must be specified: SAM with LVOT obstruction is most common. Midventricular obstruction due to systolic apposition of left ventricular walls is a less common variant, which can occur as an isolated cause of obstruction, but can also coexist with SAM [94–96]. Midcavity obstruction is a potential cause of morbidity or mortality after successful surgical relief of SAM. Midcavity obstruction may trap blood in the LV apex, which may only escape in diastole. Infrequently high systolic apical cavity pressures may lead to apical infarction in the absence of epicardial coronary disease, apical aneurysm, apical thrombus, and potential for emboli and arrhythmia [94–96]. Initially, symptomatic midcavity obstruction is managed with negative inotropic medication, often to good effect. However, when symptoms and obstruction persist, surgical relief of obstruction is indicated. The transaortic approach is made more difficult by the greater distance of the obstruction from the aortotomy, but has been successful in relieving obstruction and is the preferred route [9, 11, 12, 14, 16]. Other approaches have been reported. The mid and apical septum may be approached through the left atrium after temporary detachment of the anterior mitral leaflet [97] or by modifying the Konno procedure [7], or through ventriculotomy [7]. Seggewiss [98] has reported using alcohol ablation to relieve midventricular obstruction.

It is vital to identify, before surgery, obstruction due to anomalous insertion of the papillary muscle directly into the base of the anterior mitral leaflet without intervening chordae. When missed before surgery, this uncommon, but not rare, anomaly can lead to persistent postoperative obstruction and death [99, 100]. There are case reports of palliating this lesion through extensive septal resection [100].

Apical hypertrophic cardiomyopathy can lead to systolic cavity obliteration and increased Doppler velocities in the apex. However, the ventricle is essentially empty when these high velocities are created. Apical HCM is managed medically.

Echocardiography before surgery
Transthoracic echocardiography (TTE) is now the most frequent source of diagnosis. Doppler echocardiography provides reliable and reproducible quantification of the pressure gradient. Presence or absence of regional wall motion abnormalities are assessed, as well as ejection fraction. The mitral valve is assessed for structural abnormalities that require valve replacement as described above.

In our patients we use TTE to plan the length of surgical resection. In the apical long-axis view we routinely measure the distance from the aortic root to that portion of the left ventricular septum well past the midseptal bulge. This defines the minimum extent of the length of resection. On occasion, transthoracic imaging is inadequate due to technical reasons. When this occurs, preoperative TEE before the day of surgery may be indicated [90]. This is especially true if questions about anomalous papillary muscle or extent of septal thickness are present. With this TEE, the patient can be appraised beforehand of planned procedure and its long-term implications.

Intraoperative echocardiography is useful to assure adequate repair after cardiopulmonary bypass and myectomy [44, 101–103]. Initially, an epicardial probe was used [101, 102]. TEE offers excellent imaging and has the advantage of having the probe out of the operative field and has generally supplanted epicardial imaging [44, 90]. Persistent early SAM, with resting outflow gradient more than 50 mm Hg, or more than moderate mitral regurgitation should prompt immediate revision. Using these criteria Marwick and coworkers [102] reported that 20% of patients were placed back on heart-lung bypass and revised using TEE to guide the location of additional resection. After the patient is taken off bypass some centers give intravenous inotropic agents to exclude provocable obstruction [102]. Others provoke with premature ventricular beats [12]. Because patients are already vasodilated due to rewarming and are hypovolemic, at this time we follow the latter approach: patients with resting gradients more than 30 mm Hg or with post-PVC provoked gradients more than 50 mm Hg are placed back on heart-lung bypass [12].

Even with refinements to the myectomy, challenges persist. There is currently no method to monitor the extent of resection while the patient is on cardiopulmonary bypass. The surgeon tries to resect as much of the septal bulge as possible, all the time aware of the risks of too much resection. This is a particular problem in the patient with septal thickness less than 18 mm. Echocardiography offers the best promise to allow real time monitoring of the progress of resection. But at present, such monitoring is precluded because septal borders cannot be defined when the cardiac chambers are drained of blood.

There has been progress in our understanding of the nature of obstruction in HCM. The concept of a muscular sphincter gave way to the model of SAM caused by Venturi, and now to SAM caused by flow drag. Innovations will be successful if they are tailored to address the true nature of dynamic obstruction.

	References

Top Abstract Introduction Dynamic outflow tract... Systolic anterior motion and... Flow drag, the pushing... Surgical approach Review of HCM diversity,... References

 

1. Messmer B.J. Extended myectomy for hypertrophic obstructive cardiomyopathy. Ann Thorac Surg 1994;58:575-577.[Abstract/Free Full Text]
2. Morrow A.G. Hypertrophic subaortic stenosis. Operative methods utilized to relieve left ventricular outflow obstruction. J Thorac Cardiovasc Surg 1978;76:423-430.[Abstract]
3. McIntosh C., Maron B. Current operative treatment of obstructive hypertrophic cardiomyopathy. Circulation 1988;78:487-495.[Free Full Text]
4. Maron B.J., Merrill W.H., Freier P.A., Kent K.M., Epstein S.E., Morrow A.G. Long-term clinical course and symptomatic status of patients after operation for hypertrophic subaortic stenosis. Circulation 1978;57:1205-1213.[Abstract/Free Full Text]
5. Williams W.G., Wigle E.D., Rakowski H., Smallhorn J., LeBlanc J., Trusler G.A. Results of surgery for hypertrophic obstructive cardiomyopathy. Circulation 1987;76:V104-108.
6. Ten Berg J.M., Suttorp M.J., Knaepen P.J., Ernst S.M., Vermeulen F.E., Jaarsma W. Hypertrophic obstructive cardiomyopathy: initial results and long-term follow-up after Morrow septal myectomy. Circulation 1994;90:1781-1785.[Abstract/Free Full Text]
7. Kirklin J, Barratt-Boyes B. Hypertrophic obstructive cardiomyopathy. In: Cardiac Surgery, 2^nd edition. New York: Churchill-Livingston 1992:1239–62
8. McCully R.B., Nishimura R.A., Tajik A.J., Schaff H.V., Danielson G.K. Extent of clinical improvement after surgical treatment of hypertrophic obstructive cardiomyopathy. Circulation 1996;94:467-471.[Abstract/Free Full Text]
9. Schulte H.D., Bircks W.H., Loesse B., Godehardt E.A.J., Schwartzkopff B. Prognosis of patients with hypertrophic obstructive cardiomyopathy after transaortic myectomy. J Thorac Cardiovasc Surg 1993;106:709-717.[Abstract]
10. Schulte H.D., Borisov K., Gams E., Gramsch-Zabel H., Losse B., Scwhartzkopff B. Management of symptomatic hypertrophic obstructive cardiomyopathy – long term results after surgical therapy. Thorac Cardiovasc Surg 1999;47:213-218.[Medline]
11. Schulte H.D., Bircks W., Losse B. Techniques and complications of transaortic subvalvular myectomy in patients with hypertrophic obstructive cardiomyopathy (HOCM). Z Kardiol 1987;76(Suppl 3):145-151.
12. Schulte H.D., Bircks W., Korfer R., Kuhn H. Surgical aspects of typical subaortic and atypical midventricular hypertrophic cardiomyopathy (HOCM). Thorac Cardiovasc Surg 1981;29:375-380.[Medline]
13. Cohn L.H., Trehan H., Collins J.J., Jr Long-term follow-up of patients undergoing myotomy/myectomy for obstructive hypertrophic cardiomyopathy. Am J Cardiol 1992;70:657-660.[Medline]
14. Robbins R.C., Stinson E.B. Long-term results of left ventricular myotomy and myectomy for obstructive hypertrophic cardiomyopathy. J Thorac Cardiovasc Surg 1996;111:586-594.[Abstract/Free Full Text]
15. Heric B., Lytle B.W., Miller D.P., Rosenkranz E.R., Lever H.M., Cosgrove D.M. Surgical management of hypertrophic obstructive cardiomyopathy: early and late results. J Thorac Cardiovasc Surg 1995;110:195-208.[Abstract/Free Full Text]
16. Schoendube FA, Klues HG, Reith S, Flachskampf FA, Hanrath P, Messmer BJ. Long-term clinical and echocardiographic follow-up after surgical correction of hypertrophic obstructive cardiomyopathy with extended myectomy and reconstruction of the subvalvular mitral apparatus. Circulation1995;92:II-122–7
17. Kofflard M.J., VanHerwerden L.A., Waldstein D.J., et al. Initial results of combined anterior mitral leaflet extension and myectomy in patients with obstructive hypertrophic cardiomyopathy. J Am Coll Cardiol 1996;28:197-202.[Abstract]
18. McIntosh CL, Maron BJ, Cannon RO, Klues H. Initial results of combined anterior mitral valve plication and ventricular septal myotomy-myectomy for relief of left ventricular outflow obstruction in patients with hypertrophic cardiomyopathy. Circulation1992;86:II-60–7
19. Roberts C.S., McIntosh C.L., Brown P.S., Cannon R.O., III, Gertz S.D., Clark R.E. Reoperation for persistent outflow obstruction in hypertrophic cardiomyopathy. Ann Thorac Surg 1991;51:455-460.[Abstract/Free Full Text]
20. Cooper M.M., McIntosh C.L., Tucker E., Clark R. Operation for hypertrophic subaortic stenosis in the aged. Ann Thorac Surg 1987;44:370-378.[Abstract/Free Full Text]
21. Siegman I., Maron B.J., Permut L., McIntosh C., Clark R. Results of operation for coexistent obstructive hypertrophic cardiomyopathy and coronary artery disease. J Am Coll Cardiol 1989;13:1527-1533.[Abstract]
22. Wigle E.D., Schwartz L., Woo A., Rakowski H. To ablate or operate? That is the question!. J Am Coll Cardiol 2001;38:1708-1710.
23. Brock R. Functional obstruction of the left ventricle (acquired aortic subvalvular stenosis). Guy’s Hospital Report 1957;106:221-238.
24. Bigelow W.G., Trimble A.S., Auger P., Marquis Y., Wigle E.D. The ventriculomyotomy operation for muscular subaortic stenosis. J Thorac Cardiovasc Surg 1966;52:514.[Medline]
25. Kirklin J.W., Ellis F.H., Jr Surgical relief of diffuse subvalvular aortic stenosis. Circulation 1961;24:739-742.[Abstract/Free Full Text]
26. Cleland W.P. The surgical management of obstructive cardiomyopathy. J Cardiov Surg 1963;4:489-491.
27. Morrow A.G., Brockenbrough E.C. Surgical treatment of idiopathic hypertrophic subaortic stenosis. Technic and hemodynamic results of subaortic ventriculomyotomy. Ann Surg 1961;154:181.[Medline]
28. Morrow A.G., Fogarty T.J., Hannah H., III, Braunwald E. Operative treatment in idiopathic hypertrophic subaortic stenosis. Techniques and results of postoperative clinical and hemodynamic assessments. Circulation 1968;37:589-596.[Abstract/Free Full Text]
29. Fix P., Moberg A., Soderberg H., Karnell J. Muscular subvalvular aortic stenosis. Abnormal anterior mitral leaflet possibly the primary factor. Acta Radiologica Diagnosis 1964;2:177-193.
30. Adelman A.G., McCoughlin M.J., Marquis Y., Auger P., Wigle E.D. Left ventricular cineangiographic observations in muscular subaortic stenosis. Am J Cardiol 1969;24:689-697.[Medline]
31. Shah P.M., Graniak R., Kramer D.H. Ultrasound localization of left ventricular outflow tract obstruction in hypertrophic cardiomyopathy. Circulation 1969;40:3-11.[Abstract/Free Full Text]
32. Popp R.L., Harrison D.C. Ultrasound in the diagnosis and evaluation of therapy of idiopathic hypertrophic subaortic stenosis. Circulation 1969;40:905-914.
33. Jiang L., Levine R.A., King M.E., Weyman A.E. An integrated mechanism for systolic anterior motion of the mitral valve in hypertrophic cardiomyopathy based on echocardiographic observations. Am Heart J 1987;113:633-644.[Medline]
34. Sherrid M.V., Chu C.k, DeLia E., Mogtader A., Dwyer E.M., Jr An echocardiographic study of the fluid mechanics of obstruction in hypertrophic cardiomyopathy. J Am Coll Cardiol 1993;22:816-825.[Abstract]
35. Cape E.G., Simons D., Jimoh A., Weyman A.E., Yognathan A.P., Levine R.A. Chordal geometry determines the shape and extent of systolic anterior motion: in vitro studies. J Am Coll Cardiol 1989;13:1438-1448.[Abstract]
36. Levine R.A., Vlahakes G.J., Lefebvre X., et al. Papillary muscle displacement causes systolic anterior motion of the mitral valve. Circulation 1995;91:1189-1195.[Abstract/Free Full Text]
37. Sherrid M.V., Gunsburg D.Z., Moldenhauer S., Pearle G. Systolic anterior motion begins at low left ventricular outflow tract velocity in obstructive hypertrophic cardiomyopathy. J Am Coll Cardiol 2000;36:1344-1354.[Abstract/Free Full Text]
38. Schwammenthal E., Levine R.A. Dynamic subaortic obstruction: a disease of the mitral valve suitable for surgical repair?. J Am Coll Cardiol 1996;28:203-206.[Medline]
39. Lefebre X.P., Yoganathan A.P., Levine R.A. Insights from in vitro flow visualization into the mechanism of systolic anterior motion of the mitral valve in hypertrophic cardiomyopathy under steady flow conditions. J Biomed Eng 1992;114:406-413.
40. Reis R, Bolton MR, King JF, Pugh DM, Dunn MI, Mason DT. Anterior-superior displacement of papillary muscles producing obstruction and mitral regurgitation in idiopathic hypertrophic subaortic stenosis. Circulation 1974;50:II-181–8
41. Henry W.L., Clark C.E., Griffith J.M., Epstein S.E. Mechanism of left ventricular outflow obstruction in patients with obstructive asymmetric septal hypertrophy (idiopathic hypertrophic subaortic stenosis). Am J Cardiol 1975;35:337-345.[Medline]
42. Shah P.M., Taylor R.D., Wong M. Abnormal mitral valve coaptation in hypertrophic obstructive cardiomyopathy: proposed role in systolic anterior motion in mitral valve. Am J Cardiol 1981;48:258-262.[Medline]
43. Klues H.G., Maron B.J., Dollar A.L., Roberts W.C. Diversity of structural mitral valve alterations in hypertrophic cardiomyopathy. Circulation 1992;85:1651-1660.[Abstract/Free Full Text]
44. Grigg L.E., Wigle E.D., Williams W.G. Transesophageal echocardiography in obstructive hypertrophic cardiomyopathy. Clarification of pathophysiology and importance of intraoperative decision making. J Am Coll Cardiol 1992;20:42-52.[Abstract]
45. Nakatani S., Schwammenthal E., Lever H.M., Levine R.A., Lytle B.W., Thomas J.D. New insights into the reduction of mitral valve systolic anterior motion after ventricular septal myectomy in hypertrophic obstructive cardiomyopathy. Am Heart J 1996;131:294-300.[Medline]
46. Sherrid M.V., Gunsburg D.Z., Pearle G. Mid-systolic drop in left ventricular ejection velocity in obstructive hypertrophic cardiomyopathy – the lobster claw abnormality. J Am Soc Echocardiogr 1997;10:707-712.[Medline]
47. Sherrid M.V., Pearle G., Gunsburg D.Z. Mechanism of benefit of negative inotropes in obstructive hypertrophic cardiomyopathy. Circulation 1998;97:41-47.[Abstract/Free Full Text]
48. Cooley D.A. Surgical techniques for hypertrophic left ventricular obstructive myopathy including mitral valve plication. J Cardiac Surg 1991;6:29-33.[Medline]
49. Grossi EA, Steinberg BM, LeBoutillier M, et al. Decreasing incidence of systolic anterior motion after mitral valve reconstruction. Circulation1994;90:II-195–7
50. Joyce F., Lever H., Cosgrove D. Treatment of hypertrophic cardiomyopathy by mitral valve repair and septal myectomy. Ann Thorac Surg 1994;54:1025-1027.[Abstract/Free Full Text]
51. Matsui Y., Shiiya N., Murashita T., Sasaki S., Yasuda K. Mitral valve repair and septal myectomy for hypertrophic obstructive cardiomyopathy. J Cardiovasc Surg 2000;41:53-56.[Medline]
52. Cooley D.A., Leachman R.D., Wukasch D.C. Mitral valve replacement for idiopathic hypertrophic cardiomyopathy. J Cardiovasc Surg 1976;17:380-387.[Medline]
53. Krajcer Z., Leachman R.D., Cooley D.A., Ostojic M., Coronado R. Mitral valve replacement and septal myomectomy in hypertrophic cardiomyopathy. Ten-year follow-up in 80 patients. Circulation 1988;78:I35-43.
54. Walker W.S., Reid K.G., Cameron E.W., Walbaum P.R., Kitchin A.H. Comparison of ventricular septal surgery and mitral valve replacement for hypertrophic obstructive cardiomyopathy. Ann Thorac Surg 1989;48:528-535.[Abstract/Free Full Text]
55. McIntosh C.L., Greenberg G.J., Maron B.J., Leon M.B., Cannon R.O., Clark R.E. Clinical and hemodynamic results following mitral valve placement in patients with obstructive hypertrophic cardiomyopathy. Ann Thorac Surg 1989;47:236-246.[Abstract/Free Full Text]
56. Roberts W.C. Operative treatment of hypertrophic obstructive cardiomyopathy. The case against mitral valve replacement. Am J Cardiol 1973;32:377.[Medline]
57. Yu E., Omran A., Wigle E.D., Williams W.G., Siu S., Rakowski H. Mitral regurgitation in hypertrophic obstructive cardiomyopathy: relationship to obstruction and relief with myectomy. J Am Coll Cardiol 2000;36:2219-2225.[Abstract/Free Full Text]
58. Spirito P., Seidman C.E., McKenna W.J., Maron B.J. The management of hypertrophic cardiomyopathy. N Engl J Med 1997;336:775-785.[Medline]
59. Wigle E.D., Rakowski H., Kimball B.P., Williams W.G. Hypertrophic cardiomyopathy. Clinical spectrum and treatment. Circulation 1995;92:1680-1692.[Free Full Text]
60. Maron B.J., Casey S.A., Poliac L.C., Gohman T.E., Almquist A.K., Aeppli D.M. Clinical course of hypertrophic cardiomyopathy in a regional United States cohort. JAMA 1999;281:650-655.[Abstract/Free Full Text]
61. Maron B.J. Hypertrophic cardiomyopathy: a systematic review. JAMA 2002;287:1308-1320.[Abstract/Free Full Text]
62. Matsumura Y., Elliott P.M., Virdee M.S., Sorajja P., Doi Y., McKenna W.J. Left ventricular diastolic function assessed using Doppler tissue imaging in patients with hypertrophic cardiomyopathy: relation to symptoms and exercise capacity. Heart 2002;87:247-251.[Abstract/Free Full Text]
63. Lele S.S., Thomson H.L., Seo H., Belenkie I., McKenna W.J., Frenneaux M.P. Exercise capacity in hypertrophic cardiomyopathy: role of stroke volume limitation, heart rate and diastolic filling characteristics. Circulation 1995;92:2886-2894.[Abstract/Free Full Text]
64. Cannon R.O., Rosing D.R., Maron B.J., et al. Myocardial ischemia in patients with hypertrophic cardiomyopathy: Contribution of inadequate vasodilator reserve and elevated left ventricular filling pressures. Circulation 1985;71:234-243.[Abstract/Free Full Text]
65. Dilsiziam V., Bonow R.O., Epstein S.E., Fananapazir L. Myocardial ischemia detected by thallium scintigraphy is frequently related to cardiac arrest and syncope in young patients with hypertrophic cardiomyopathy. J Am Coll Cardial 1993;22:780-796.
66. Udelson J.E., Bonow R.O., O’Gara P.T., Maron B.J., Van Lingen A., Bacharach S.L., Epstein S.E. Verapamil prevents silent myocardial perfusion abnormalities during exercise in asymptomatic patients with hypertrophic cardiomyopathy. Circulation 1995;79:1052-1060.[Abstract/Free Full Text]
67. Kass D.A., Chen C.H., Talbot M.W., Rochitte C.E., Lima J.A., Berger R.D., Calkins H. Ventricular pacing with premature excitation for treatment of hypertensive-cardiac hypertrophy with cavity-obliteration. Circulation 1999;100:807-812.[Abstract/Free Full Text]
68. Elliott P.M., Gimeno Blanes J.R., Mahon N.G., Poloniecki J.D., McKenna W.J. Relation between severity of left-ventricular hypertrophy and prognosis in patients with hypertrophic cardiomyopathy. Lancet 2001;357:420-424.[Medline]
69. Maron B.J., Shen W.K., Link M.S., et al. Efficacy of implantable cardioverter-defibrillators for the prevention of sudden death in patients with hypertrophic cardiomyopathy. N Engl J Med 2000;342:365-373.[Medline]
70. Wigle D., Sasson Z., Henderson M.A., et al. Hypertrophic cardiomyopathy. The importance of the site and the extent of hypertrophy. A review. Prog Cardiovasc Dis 1985;28:1-83.[Medline]
71. Harrison D.C., Braunwald E., Glick G., et al. Effects of beta adrenergic blockade on the circulation with particular reference to observations in patients with hypertrophic subaortic stenosis. Circulation 1964;29:84-98.[Abstract/Free Full Text]
72. Pollick C. Disopyramide in hypertrophic cardiomyopathy. Noninvasive assessment after oral administration. Am J Cardiol 1988;62:1252-1255.[Medline]
73. Sherrid M., DeLia E., Dwyer E. Oral disopyramide therapy for obstructive hypertrophic cardiomyopathy. Am J Cardiol 1988;62:1085-1088.[Medline]
74. Rosing DR, Kent KM, Maron BJ, Epstein, SE. Verapamil therapy: a new approach to the pharmacologic treatment of hypertrophic cardiomyopathy: II: Effects on exercise capacity and symptomatic status. Circulation 1979;60:1208–13
75. Epstein S.E., Rosing D.R. Verapamil: its potential for causing serious complications in patients with hypertrophic cardiomyopathy. Circulation 1979;60:437-441.
76. Jeanrenaud X., Goy J.J., Kappenberger L. Effects of dual-chamber pacing in hypertrophic obstructive cardiomyopathy. Lancet 1992;339:1318-1323.[Medline]
77. Fananapazir L., Cannon R.O., Tripodi D., Panza J.A. Impact of dual-chamber permanent pacing in patient with obstructive hypertrophic cardiomyopathy with symptoms refractory to verapamil and b-adrenergic blocker therapy. Circulation 1992;85:2149-2161.[Abstract/Free Full Text]
78. Kappenberger L., Linde C., Daubert C., McKenna W., Meisel E., Sadoul N., Chojnowska L., Guize L., Gras D., Jeanrenaud X., Ryden L. Pacing in hypertrophic obstructive cardiomyopathy. A randomized crossover study. Eur Heart J 1997;18:1249-1256.[Abstract/Free Full Text]
79. Gadler F., Linde C., Ryden L. Rapid return of left ventricular outflow tract obstruction and symptoms following cessation of long-term atrioventricular synchronous pacing for obstructive hypertrophic cardiomyopathy. Am J Cardiol 1999;83:553-557.[Medline]
80. Maron B.J., Nishimura R.A., McKenna W.J., Rakowski H., Josephson M.E., Kieval R.S. Assessment of permanent dual-chamber pacing as a treatment for drug-refractory symptomatic patients with obstructive hypertrophic cardiomyopathy. A randomized, double-blind, crossover study (M-PATHY). Circulation 1999;99:2927-2933.[Abstract/Free Full Text]
81. Linde C., Gadler F., Kappenberger L., Ryden L. Placebo effect of pacemaker implantation in obstructive hypertrophic cardiomyopathy. PIC Study Group. Am J Cardiol 1999;83:903-907.[Medline]
82. Knight C., Kurbaan A.S., Seggewiss H., Henein M., Gunning M., Harrington D., Fassbender D., Gleichmann U., Sigwart U. Nonsurgical septal reduction for hypertrophic obstructive cardiomyopathy: outcome in the first series of patients. Circulation 1997;95:2075-2081.[Abstract/Free Full Text]
83. Faber L., Ziemssen P., Seggewiss H. Targeting percutaneous transluminal septal ablation for hypertrophic obstructive cardiomyopathy by intraprocedural echocardiographic monitoring. J Am Soc Echocardiogr 2000;13:1074-1079.[Medline]
84. Nagueh S.F., Lakkis N.M., He Z.-X., et al. Role of myocardial contrast echocardiography during nonsurgical septal reduction therapy for hypertrophic obstructive cardiomyopathy. J Am Coll Cardiol 1998;32:225-229.[Abstract/Free Full Text]
85. Lakkis N.M., Nagueh S.F., Kleiman N.S., et al. Echocardiography-guided ethanol septal reduction for hypertrophic obstructive cardiomyopathy. Circulation 1998;98:1750-1755.[Abstract/Free Full Text]
86. Gietzen F.H., Leuner J., Raute-Kreinsen U., et al. Acute and long-term results after transcoronary ablation of septal hypertrophy: catheter interventional treatment for hypertrophic obstructive cardiomyopathy. Eur Heart J 1999;20:1342-1354.[Abstract/Free Full Text]
87. Seggewiss H., Gleichmann U., Faber L., Fassbender D., Schmidt H.K., Strick S. Percutaneous transluminal septal myocardial ablation in hypertrophic obstructive cardiomyopathy: acute results and 3-month follow-up in 25 patients. J Am Coll Cardiol 1998;31:252-258.[Abstract/Free Full Text]
88. Faber L., Meissner A., Ziemssen P., Seggewiss H. Percutaneous transluminal septal myocardial ablation for hypertrophic obstructive cardiomyopathy: long term follow up of the first series of 25 patients. Heart 2000;83:326-331.[Abstract/Free Full Text]
89. Nagueh S.F., Ommen S.R., Lakkis N.M., et al. Comparison of ethanol septal reduction therapy with surgical myectomy for the treatment of hypertrophic obstructive cardiomyopathy. J Am Coll Cardiol 2001;38:1701-1706.[Abstract/Free Full Text]
90. Qin J.X., Shiota T., Lever H.M., et al. Outcome of patients with hypertrophic obstructive cardiomyopathy after percutaneous transluminal septal myocardial ablation and septal myectomy surgery. J Am Coll Cardiol 2001;38:1994-2000.[Abstract/Free Full Text]
91. Flores-Ramirez R., Lakkis N.M., Middleton K.J., Killip D., Spencer W.H., 3rd, Nagueh S.F. Echocardiographic insights into the mechanisms of relief of left ventricular outflow tract obstruction after nonsurgical septal reduction therapy in patients with hypertrophic obstructive cardiomyopathy. J Am Coll Cardiol 2001;37:208-214.[Abstract/Free Full Text]
92. Henein M.Y., O’Sullivan C.A., Ramzy I.S., Sigwart U., Gibson D.G. Electromechanical left ventricular behavior after nonsurgical septal reduction in patients with hypertrophic obstructive cardiomyopathy. J Am Coll Cardiol 1999;34:1117-1122.[Abstract/Free Full Text]
93. Arrazaghi A.A., Butany J.W., Williams W.G., Wigle D.E., Rakowski H. Myectomy for hypertrophic obstructive cardiomyopathy after failed alcohol septal ablation: clinicopathological correlations. Can J Cardiol 2001;17:197-202.[Medline]
94. Falikov R.E., Resnekov L., Bharati S., Lev M. Mid-ventricular obstruction: a variant of obstructive cardiopathy. Am J Cardiol 1976;37:432-437.[Medline]
95. Zoghbi W.A., Haichin R.N., Qui-ones M.A. Mid-cavity obstruction in apical hypertrophy: Doppler evidence of diastolic intraventricular gradient with higher apical pressure. Am Heart J 1988;116:1469-1474.[Medline]
96. Nakamura T., Matsubara K., Furukawa K., et al. Diastolic paradoxic jet flow in patients with hypertrophic cardiomyopathy: evidence of concealed apical asynergy with cavity obliteration. J Am Coll Cardiol 1992;19:516-524.[Abstract]
97. Matsuda H., Nomura F., Kadoba K., Taniguchi K., Imagawa H., Kagisaki K., Sano T. Transatrial and transmitral approach for left ventricular myectomy and mitral valve plication for diffuse-type hypertrophic obstructive cardiomyopathy: a novel approach. J Thorac Cardiovasc Surg 1996;112:195-196.[Free Full Text]
98. Seggewiss H., Faber L. Percutaneous septal ablation for hypertrophic cardiomyopathy and mid-ventricular obstruction. Eur J Echocardiogr 2000;1:277-280.[Abstract/Free Full Text]
99. Klues H.G., Roberts W.C., Maron B.J. Anomalous insertion of papillary muscle directly into anterior mitral valve lealet in hypertrophic cardiomyopathy. Significance in producing left ventricular outflow obstruction. Circulation 1991;84:1188-1197.[Abstract/Free Full Text]
100. Maron B.J., Nishimura R.A., Danielson G.K. Pitfalls in clinical recognition and a novel operative approach for hypertrophic cardiomyopathy with severe outflow obstruction due to anomalous papillary muscle. Circulation 1998;98:2505-2508.[Abstract/Free Full Text]
101. Maron B.J. Utility of intraoperative echocardiography in planning surgical strategy in hypertrophic cardiomyopathy. In: Baroldi G., Camerini F., Goodwin J.F., eds. Advances in cardiomyopathies. Berlin: Springer-Verlag, 1990:136-150.
102. Marwick T.H., Stewart W.J., Lever H.M., et al. Benefits of intraoperative echocardiography in the surgical management of hypertrophic cardiomyopathy. J Am Coll Cardiol 1992;20:1066-1072.[Abstract]
103. Franke A., Schöndube F.A., Kühl H.P., et al. Quantitative assessment of the operative results after extended myectomy and surgical reconstruction of the subvalvular mitral apparatus in hypertrophic obstructive cardiomyopathy using dynamic three-dimensional transesophageal echocardiography. J Am Coll Cardiol 1998;31:1641-1649.[Abstract/Free Full Text]

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