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Ann Thorac Surg 2008;85:127-133. doi:10.1016/j.athoracsur.2007.07.063
© 2008 The Society of Thoracic Surgeons
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Original Articles: Cardiovascular

Current Effectiveness and Risks of Isolated Septal Myectomy for Hypertrophic Obstructive Cardiomyopathy

Nicholas G. Smedira, MDa,*, Bruce W. Lytle, MDa, Harry M. Lever, MDb, Jeevanantham Rajeswaran, MSc, Gita Krishnaswamy, MSc, Ryan K. Kaple, BSa, Diana O.W. Dolney, MSN, RNb, Eugene H. Blackstone, MDa,c

a Department of Thoracic and Cardiovascular Surgery, Cleveland Clinic, Cleveland, Ohio
b Department of Cardiovascular Medicine, Cleveland Clinic, Cleveland, Ohio
c Department of Quantitative Health Sciences, Cleveland Clinic, Cleveland, Ohio

Accepted for publication July 20, 2007.

* Address correspondence to Dr Smedira, Kaufman Center for Heart Failure, Department of Thoracic and Cardiovascular Surgery, Cleveland Clinic, 9500 Euclid Avenue/F24, Cleveland, OH 44195 (Email: smidern{at}ccf.org).


Adult cardiac surgery: The Annals of Thoracic Surgery CME Program is located online at http://cme.ctsnetjournals.org. To take the CME activity related to this article, you must have either an STS member or an individual non-member subscription to the journal.

 

   Abstract
Top
 Abstract
Introduction
 Patients and Methods
 Results
 Comment
 Acknowledgments
 References
 
Background: Septal myectomy is the gold-standard therapy for hypertrophic obstructive cardiomyopathy (HOCM). However, it is being challenged by a less-invasive alternative: alcohol septal ablation. This study examined the clinical effectiveness and risks of isolated septal myectomy for HOCM.

Methods: From January 1994 to January 2005, 323 patients underwent isolated septal myectomy (mean age 50 ± 14 years, 53% male). Preoperative septal thickness was 2.3 ± 0.46 cm and peak left ventricular outflow tract (LVOT) gradient 68 ± 43 mm Hg. Effectiveness of myectomy was assessed by echocardiography, sudden death, and functional limitation, early risks by intraoperative and postoperative complications, and late risks by follow-up for HOMC-related reoperation, heart block, and all-cause mortality (mean 3.6 ± 2.8 years, 1,152 patient-years, 10% followed ≥8 years).

Results: Myectomy was effective, resulting in sustained decrease in septal thickness and LVOT gradient, absence of sudden death, and improved functional status. Early in-hospital morbidity was low, with no hospital deaths; two iatrogenic ventricular septal defects were repaired uneventfully, and 22 pacemakers were required for heart block. In the intermediate term, 10 patients required HOCM-related reoperations (4 redo myectomies, 6 mitral valve procedures), with 92% freedom from reoperation at eight years. Seventy-nine percent were free of pacemakers by 8 years, and survival was 90%, equivalent to that of the general population.

Conclusions: Isolated septal myectomy is effective in eliminating LVOT obstruction and sudden death and in improving functional status, with low operative morbidity and mortality. Few reoperations are required late and outcomes are excellent. It should be considered the treatment of choice for HOCM.

For more than 30 years, septal myectomy has successfully treated symptomatic patients with hypertrophic obstructive cardiomyopathy (HOCM). We and others have demonstrated that long-term survival after myectomy is equivalent to that of the general population and better than that of patients with HOCM not undergoing surgery [1–3]. Concerns remain about the effectiveness and morbidity of this invasive procedure. These concerns have heightened relevance for patients and physicians because of the dramatic increase in the number of patients referred for therapy [4] and development of a less invasive alternative: alcohol septal ablation [4–8]. Therefore, we have reviewed our experience with septal myectomy for HOCM over the past decade to assess its effectiveness in relieving left ventricular outflow tract (LVOT) obstruction, preventing sudden cardiac death, and improving symptoms on the one hand and early and long-term morbidity on the other.


   Patients and Methods
Top
 Abstract
 Introduction
 Patients and Methods
Results
 Comment
 Acknowledgments
 References
 
Patients
From January 1994 to January 2005, 716 patients underwent septal myectomy at Cleveland Clinic; 323 were adjudicated to have HOCM and underwent myectomy as the major procedure ("isolated septal myectomy"). Included were 5 patients undergoing concomitant repair of a patent foramen ovale and 16 undergoing pulmonary vein isolation for paroxysmal atrial fibrillation. Clinical data were entered prospectively and concurrently with patient care into Cleveland Clinic’s Cardiovascular Information Registry, Echocardiographic Database, and, for some variables, a HOCM-specific database. All were approved for use in research by the Institutional Review Board (IRB), with patient consent waived.

Preoperative peak LVOT gradient was 68 ± 43 mm Hg, interventricular septal thickness 2.3 ± 0.46 cm, and LV mass 367 ± 117 g (Table 1). Ten patients (3.1%) had undergone previous alcohol ablation. Eighty-five (26%) had varying degrees of heart block, with 43 (13%) having pacemakers for complete heart block. Fifteen patients (4.6%) came to operation with implantable cardioverter-defibrillators (ICDs). Mean age was 50 ± 14 years (range, 19 to 84 years), and 172 (53%) were men.


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  		Table 1 Characteristics of Patients Undergoing Isolated Septal Myectomy
 
Septal Myectomy
All patients had resting or provocable LVOT obstruction. Indications for myectomy included drug-refractory class III-IV symptoms, intolerance to medications, episode of heart failure, syncope or near-syncope, blood pressure drop of more than 10 mm Hg or failure to increase at peak exercise, recent episode of atrial fibrillation, and very low functional capacity for age during metabolic stress echocardiography. Our septal myectomy technique evolved only slightly over the study period. Important steps in the procedure included detailed review of intraoperative transesophageal echocardiograms (TEE), beginning the myectomy well below the membranous septum to avoid injuring the bundle of His, and wide septal resection to the base of both papillary muscles and often to both fibrous trigones, as described by Yacoub and colleagues [9] and Dearani and Danielson [10] (Fig 1).


Figure 1
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  		Fig 1. Extended myectomy. Muscle resection begins well below the membranous septum (oval), removing muscle over both papillary muscles, and often extending to both trigones.

 
Follow-Up
Periodic follow-up was by IRB-approved questionnaires and telephone scripts, with patient consent required. For this study, an additional cross-sectional follow-up was performed that was 93% complete, with mean follow-up of 3.6 ± 2.8 years and longest reliable follow-up (10% of patients) to 8 years; 1,152 patient-years of information were available for analysis.

Endpoints
Effectiveness of myectomy was assessed in part by return of LVOT obstruction. This was assessed by the following: (1) LVOT peak gradient; (2) interventricular septal thickness; and (3) systolic anterior motion (SAM) of the mitral valve. All patients had at least one postoperative echocardiogram. Subsequent echocardiograms were performed at the discretion of referring physicians. A concerted effort was made to obtain at least a detailed report of these (obtained at a median of 3 months, 10% after 4.6 years). Thus, interventricular septal thickness was available from 817 echocardiograms in 288 patients, LVOT peak gradient from 519 echocardiograms in 243 patients, and SAM from 610 echocardiograms in 261 patients. Heart failure symptoms were elicited during follow-up using a grid of functional activity questions from which a New York Heart Association (NYHA) class was assigned. This assessment was available from 290 questionnaires of 251 patients. During follow-up, circumstances of any death were elicited from families to ascertain occurrence of sudden death.

Early risks of myectomy were assessed by intraoperative events, postoperative mortality and morbidity (using Society of Thoracic Surgeons’ National Database definitions; see http://www.ctsnet.org/file/rptDataSpecifications252_1_ForVendorsPGS.pdf), and need for pacemakers and early HOCM-related reinterventions. Intermediate-term mortality, additional HOCM-related reoperations, and pacemaker requirements were identified during follow-up.

Data Analysis
Categoric variables are summarized as frequencies and percentages. Continuous variables are summarized as means ± standard deviations (SDs), or as 15th, 50th (median), and 85th percentiles when distributions were skewed. Uncertainty of proportions and other point estimates are represented by asymmetric 68% confidence limits (CL) equivalent to ±1 standard error.

To assess the temporal trend of peak LVOT gradient and septal thickness, echocardiographic measurements were analyzed by longitudinal mixed model regression for repeated continuous data (SAS PROC MIXED; SAS Institute Inc, Cary, NC) [11]. Temporal trend of prevalence of SAM was estimated using longitudinal binary logistic regression (SAS PROC GENMOD; SAS Institute Inc) [11]. Temporal trend of NYHA class used longitudinal mixed model regression for repeated ordinal data (SAS PROC GENMOD; SAS Institute Inc) [11]. Survival, new pacemaker or ICD insertion, and HOCM reoperation were analyzed nonparametrically by the Kaplan-Meier method and parametrically by multiphase hazard modeling [12].


   Results
Top
 Abstract
 Introduction
 Patients and Methods
 Results
Comment
 Acknowledgments
 References
 
Effectiveness of Septal Myectomy
Interventricular thickness was reduced from 2.3 ± 0.46 cm premyectomy to 1.6 ± 0.37 cm immediately postmyectomy. Average septal thickness slightly increased, then slightly decreased across time (Fig 2A). Peak LVOT gradient fell from 68 ± 43 mm Hg premyectomy to 17 ± 11 mm Hg immediately postmyectomy, continued to fall during the first 3 months after myectomy, then slowly declined over the ensuing years (Fig 2B). Interestingly, although presence of SAM fell from 99% preoperatively to 52% postoperatively, its prevalence thereafter increased somewhat, then fell (Fig 2C).


Figure 2
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  		Fig 2. Effectiveness of septal myectomy as assessed longitudinally by echocardiography after isolated septal myectomy. Dot at vertical axis is preoperative value, and dashed line leads to intermediate postmyectomy value at time zero. Dots are grouped "independent" point estimates, and solid line enclosed within 68% confidence limits (equivalent to ±1 standard error) is average response corrected for repeated measures. (A) Thickness of interventricular septum. (B) Peak left ventricular outflow tract (LVOT) gradient. (C) Anterior motion of septal leaflet of mitral valve (SAM).

 
No instances of sudden death were reported. The NYHA class improved from less than 10% of patients being asymptomatic to more than 50% (Fig 3). At year 5, 22% experienced moderate or severe functional limitation, and this was only slowly progressive.


Figure 3
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  		Fig 3. New York Heart Association (NYHA) functional class after isolated septal myectomy. Symbols represent grouped "independent" distributions of classes and solid lines are estimated prevalence of repeated measures. Class I is represented by closed circles, class II by open circles, class III by squares, and class IV by triangles.

 
Risks of Septal Myectomy
Intraoperative
Iatrogenic ventricular septal defects (VSDs) were created in two patients. They were identified on postmyectomy TEE and repaired without sequelae.

Postoperative (in-hospital)
There were no hospital deaths (0%, CL 0% to 0.6%).

New permanent pacemakers were implanted in 22 of the 280 patients without preoperative pacemakers (7.9%, CL 6.2% to 9.8%). Of these 280, 230 (82%) had normal preoperative electrocardiograms and 50 (18%) had intraventricular conduction delay or bundle branch block (Table 1). Pacemakers were required in 7 patients (3%) with normal preoperative conduction, 15 (30%) with any conduction abnormality, and 10 (77%) with right bundle-branch block.

Two patients underwent mitral valve replacement at 8 and 11 days postmyectomy. In one, the anterolateral papillary muscle was attached to the anterior septum, limiting the extent of the myectomy. Although intraoperative postmyectomy isoproterenol provocation failed to generate an LVOT gradient, postoperative echocardiogram revealed a greater than 70-mm gradient. In the second patient, residual 1 to 2+ mitral regurgitation increased to 3 to 4+ postoperatively, possibly related to right ventricular pacing.

Other postoperative complications were uncommon, except for atrial fibrillation (Table 2). Median, 15th, and 85th percentiles for postoperative intubation time were 10 hours (7 to 20) for intensive care stay 1 day (1 to 3), for postoperative length of stay 6 days (5 to 9), and for total hospital stay 6 days (5 to 11).


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  		Table 2 In-Hospital Complications After Isolated Septal Myectomy
 
Intermediate term
The HOCM-related reoperations after 30 days were performed in 8 patients (Table 3). Including all reoperations, 99% were free of reoperation at 3 months, 99% at 1 year, 98% at 3 years, 96% at 5 years, and 92% at 8 years (Fig 4).


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  		Table 3 Hypertrophic-Obstructive Cardiomyopathy Related Reoperations Occurring After 30 Days
 

Figure 4
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  		Fig 4. Freedom from reoperation related to hypertrophic obstructive cardiomyopathy after isolated myectomy. Solid lines are estimated prevalence of repeated measures. Open circles represent individual reoperations.

 
New permanent pacemakers for heart block were implanted in 19 additional patients during follow-up. Freedom from pacemakers (excluding preoperative pacemakers) was 90% at 3 months, 89% at 1 year, 86% at 3 years, 83% at 5 years, and 79% at 8 years (Fig 5).


Figure 5
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  		Fig 5. Freedom from pacemaker insertion after isolated septal myectomy (patients with pacemakers preoperatively excluded). Solid lines are estimated prevalence of repeated measures. Open circles represent individual pacemaker insertion. (PPM = permanent pacemaker.)

 
To date, 12 patients have died, with 100% survival at 3 months, 99.7% at 1 year, 98% at 3 years, 95% at 5 years, and 90% at 8 years. No early phase of hazard was identified, and survival was equivalent to that of the age-, race-, and sex-matched U.S. population (Fig 6).


Figure 6
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  		Fig 6. Survival after isolated septal myectomy. Solid lines are estimated prevalence of repeated measures. Open circles represent individual deaths. The dash-dot-dash line is survival of an age-, race-, gender-matched U.S. population life table.

 

   Comment
Top
 Abstract
 Introduction
 Patients and Methods
 Results
 Comment
Acknowledgments
 References
 
Effectiveness of Septal Myectomy
Septal myectomy, well-accepted as a potentially curative therapy for HOCM, is still considered innovative, with frequent complications. We found to the contrary that it reliably eliminates LVOT obstruction with few complications and low (in this series, no) hospital mortality, and provides patients with survival equivalent to an age-matched population without HOCM.

Safety and efficacy of this procedure are related to tailoring the operation to septal anatomy and geometry as visualized on the intraoperative TEE. This cannot be overemphasized. Modifications compared with classic myectomy [9] include wider resections well below the membranous septum and avoiding thin areas of the septum, as seen in elderly patients with isolated proximal septal bulges. This approach results in a reliable reduction of the peak gradient to less than 20 mm Hg and substantial and durable improvement in functional status.

Risk of Septal Myectomy
Although previously published series have reported low hospital mortality, this is the first with no deaths. Improved surgical care and our focus on isolated septal myectomy, exclusive of patients undergoing more complex procedures, are likely explanations. In our previous publication [2] hospital mortality was 6% overall and 4% for isolated myectomy, increasing to 8% for patients undergoing myectomy plus a valve procedure.

Complications were uncommon. In two patients, VSDs were generated and successfully repaired. Two patients required aortic valve replacement late after myectomy. Although the exact mechanism of the new aortic regurgitation is unknown, direct injury to the valve leaflets and destabilizing the anulus by beginning the myectomy too close to the right coronary cusp must be avoided. The 3 patients needing a second myectomy had thick residual septums (2.0 to 2.7 cm) at reoperation. This suggests inadequate resection at initial operation. To avoid this, we have become more aggressive with the initial septal resection, especially in younger patients. If intraoperative TEE shows mild gradients but a septum 1.7 cm or greater, additional muscle is resected.

Requirement for new pacemakers was infrequent if the patient had normal conduction. We confirmed our previous finding that preexisting conduction abnormalities substantially increase the likelihood of postoperative heart block [13]. Most patients will have a left bundle branch block postoperatively. If right bundle branch block is present preoperatively, as seen after alcohol septal ablation, most patients will require a pacemaker; if there is normal conduction, only 3% will. This information is useful to counsel the patient, as occasionally mitral valve replacement is preferred to correct intrinsic mitral valve pathology and avoid a permanent pacemaker.

Intrinsic mitral valve pathology or anomalies affect both intraoperative decision-making and long-term success. Both patients requiring early reoperation had mitral valve abnormalities, and 5 of 8 patients undergoing late reoperation had mitral regurgitation and leaflet abnormalities.

Strengths and Limitations
This is a single-institution experience in which septal myectomy is just one aspect of the comprehensive care of patients with HOCM. In an effort to avoid multiple learning curves and improve outcomes, management of these patients has been deliberately limited to physicians (HL, NS, BWL) with a focused interest in treating HOCM. Thus, our results may not be generalizable. However, it is a large experience with reproducible results over the last decade. We chose to focus on isolated septal myectomy as the group of patients most comparable with those considered for alternative therapy, such as alcohol ablation. As such, it serves as a benchmark for these alternatives.

Conclusion
Septal myectomy is a safe, reliable, and durable method of eliminating LVOT obstruction in HOCM. It improves functional status and normalizes life expectancy. It is the benchmark for ablative therapies and is our preferred method for treating this complex and fascinating disease.


   Acknowledgments
Top
 Abstract
 Introduction
 Patients and Methods
 Results
 Comment
 Acknowledgments
References
 
The authors thank Songhua Lin, MS, for statistical programming, Maura J. Schnauffer, for data management, Michelle Miluk, RN, BSN, for research coordination, Tanya Ashinhurst, BA, for assisting with the registry and data retrieval, and Karen Mrazeck, Capri Spencer, and Kelly Polasko for collecting follow-up data. Dr Blackstone is supported in part by the Kenneth Gee and Paula Shaw, PhD, Chair in Heart Research.


   References
Top
 Abstract
 Introduction
 Patients and Methods
 Results
 Comment
 Acknowledgments
 References
 

  1. Robbins RC, Stinson EB. 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]
  2. Heric B, Lytle BW, Miller DP, Rosenkranz ER, Lever HM, Cosgrove DM. Surgical management of hypertrophic obstructive cardiomyopathyEarly and late results. J Thorac Cardiovasc Surg 1995;110:195-206discussion 208.[Abstract/Free Full Text]
  3. Ommen SR, Maron BJ, Olivotto I, et al. Long-term effects of surgical septal myectomy on survival in patients with obstructive hypertrophic cardiomyopathy J Am Coll Cardiol 2005;46:470-476.[Abstract/Free Full Text]
  4. Maron BJ, Dearani JA, Ommen SR, et al. The case for surgery in obstructive hypertrophic cardiomyopathy J Am Coll Cardiol 2004;44:2044-2053.[Abstract/Free Full Text]
  5. Hess OM, Sigwart U. New treatment strategies for hypertrophic obstructive cardiomyopathy: alcohol ablation of the septum: the new gold standard? J Am Coll Cardiol 2004;44:2054-2055.[Abstract/Free Full Text]
  6. Watkins H, McKenna WJ. The prognostic impact of septal myectomy in obstructive hypertrophic cardiomyopathy J Am Coll Cardiol 2005;46:477-479.[Free Full Text]
  7. Salberg L. Treating hypertrophic cardiomyopathy: two views J Am Coll Cardiol 2005;46:2147.[Free Full Text]
  8. Ralph-Edwards A, Woo A, McCrindle BW, et al. Hypertrophic obstructive cardiomyopathy: comparison of outcomes after myectomy or alcohol ablation adjusted by propensity score J Thorac Cardiovasc Surg 2005;129:351-358.[Abstract/Free Full Text]
  9. Yacoub M, Onuzo O, Riedel B, Radley-Smith R. Mobilization of the left and right fibrous trigones for relief of severe left ventricular outflow obstruction J Thorac Cardiovasc Surg 1999;117:126-133.[Abstract/Free Full Text]
  10. Dearani JA, Danielson GK. Septal myectomy for obstructive hypertrophic cardiomyopathy Oper Tech Thorac Cardiovasc Surg 2004;9:278-292.
  11. Diggle PJ, Heagerty PJ, Liang KY, Zeger SL. Analysis of longitudinal dataNew York: Oxford University Press; 2002.
  12. Blackstone EH, Naftel DC, Turner Jr ME. The decomposition of time-varying hazard into phases, each incorporating a separate stream of concomitant information J Am Stat Assoc 1986;81:615-624.
  13. Qin JX, Shiota T, Lever HM, et al. Conduction system abnormalities in patients with obstructive hypertrophic cardiomyopathy following septal reduction interventions Am J Cardiol 2004;93:171-175.[Medline]

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