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Ann Thorac Surg 1998;65:1207-1214
© 1998 The Society of Thoracic Surgeons
a Clinic of Cardiovascular Surgery, Department of Surgery, University Hospital, Zurich, Switzerland
b Division of Cardiology, Department of Medicine, University Hospital, Zurich, Switzerland
Address reprint requests to Dr Schönbeck, Clinic of Cardiovascular Surgery, University Hospital, Raemistrasse 100, CH-8091 Zurich, Switzerland
Presented at the Thirty-third Annual Meeting of The Society of Thoracic Surgeon, San Diego, CA, Feb 3–5, 1997.
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Abstract |
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 Top Abstract IntroductionPatients and methodsResultsCommentReferences |
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Methods. Between 1965 and 1995, 110 consecutive patients 2 to 66 years old (mean age, 37 ± 15 years) with an invasively measured left ventricular outflow tract gradient of 86 ± 39 mm Hg (81 ± 42 mm Hg by Doppler echocardiography) underwent either septal myectomy only (n = 87) or myectomy combined with additional procedures (n = 23). Mean follow-up was 11.7 ± 7.5 years. Predictors of late events were calculated using multivariate Cox regression analysis.
Results. The perioperative mortality rate was 3.6% (n = 4). The cumulative survival rate at 5, 10, and 15 years was 93%, 80%, and 72%, respectively, and symptom-free survival, 77%, 50%, and 33%, respectively. Predictors of late death were New York Heart Association class III or IV (p < 0.05), congestive heart failure (p < 0.05) and additional procedures (p < 0.05). The left ventricular outflow tract gradient was nearly eliminated in all patients, the left atrial dimension decreased significantly during the early years, and left ventricular dilatation occurred late in 17 patients.
Conclusions. Septal myectomy is associated with a low perioperative mortality and a high late survival rate (72% at 15 years’ follow-up). Septal myectomy is still an excellent modality in the treatment strategy for symptomatic patients with hypertrophic obstructive cardiomyopathy.
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Introduction |
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TopAbstractIntroductionPatients and methodsResultsCommentReferences |
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In recent years, new therapeutic modalities such as dual-chambered pacing [2–4] and catheter-induced ablation of the interventricular septum by alcohol infusions [5] have been developed. The beneficial effect of apical preexcitation, achieved by right ventricular pacing, on LVOT pressure gradient was shown as early as 1967 by Hassenstein and associates [6]. Twenty years later, the technological advances in DDD pacing made this treatment available for many patients, who responded with a drop in the systolic pressure gradient of more than 30% [2–4]. Permanent apical preexcitation is obtained by shortening the atrioventricular conduction. Occasionally, catheter ablation of the atrioventricular node is necessary to achieve this goal [2]. Nonsurgical myectomy aims at selective destruction of the hypertrophied septum by injection of alcohol in the first or second major septal coronary branch. Currently this procedure is still experimental and cannot be recommended for a large number of patients [5].
With the introduction of these methods, it has become necessary to review the risks and benefits of septal myectomy. In addition, there is a need to define which patients will benefit most from surgical intervention. Therefore, preoperative and postoperative characteristics in patients operated on between 1965 and 1995 at this institution were analyzed retrospectively.
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Patients and methods |
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TopAbstractIntroductionPatients and methodsResultsCommentReferences |
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There were 69 male and 41 female patients with a mean age of 37 ± 15 years (range, 2 to 66 years), including 12 children and 7 adults older than 60 years. Twenty-four patients (22%) had a family history of HOCM. Most patients were in New York Heart Association (NYHA) functional class III (average class, 2.54 ± 0.8). The mean duration of symptoms was 8.2 ± 6.8 years (range, 0 to 43 years). Exertional dyspnea was present in 62% of patients, angina in 37%, syncope in 24%, presyncope in 23%, congestive heart failure in 15%, and atrial fibrillation in 9%. Ten percent of the patients had experienced pulmonary edema, and 2 patients had been resuscitated from ventricular fibrillation. All adult patients had been treated with either ß-blockers or calcium-channel antagonists; none had received amiodarone hydrochloride.
Preoperative hemodynamics were assessed by heart catheterization in 109 patients and by echocardiography in 64. The LVOT pressure gradient was measured at rest in all patients (mean gradient, 86 ± 39 mm Hg) and in 39 after a premature beat or with drug provocation (mean gradient, 119 ± 38 mm Hg) during heart catheterization. Left ventricular peak systolic pressure was 220 ± 51 mm Hg (maximal value, 380 mm Hg) and LV end-diastolic pressure, 22 ± 8 mm Hg. Mitral regurgitation was present in 50% of patients; it was moderate in 8% and severe in 4%. Structural alterations of the valve were found in 5 patients after aortic (n = 2) or mitral (n = 3) endocarditis. Two aortic valves were bicuspid, and two were thickened and calcified. Two patients had ruptured chordae tendineae. One patient had an aneurysm of the ascending aorta, and another, a subvalvular muscular pulmonary stenosis. Major coronary artery disease was found in 3 patients.
Surgical technique
The surgical approach evolved during the study period. Most patients (n = 66) had operation through an aortic approach (from 1966 to 1995); 32, through a left ventricular approach (from 1965 to 1979); and 12, through a combined aortic and left ventricular approach (from 1970 to 1981).
Isolated septal myectomy was performed in 87 patients (79%). Three patients also underwent aortocoronary bypass grafting. Two mitral valve replacements were performed because of severe regurgitation resulting from bacterial endocarditis, and ten mitral valve repairs were done for severe systolic anterior motion (n = 7), ruptured chordae tendineae (n = 2), and bacterial endocarditis (n = 1). Mitral valve repair consisted of a modified Kay-Wooler valvuloplasty, reattachment of chordae tendineae, and mobilization of the papillary muscles down to the apex with resection of all hypertrophied portions and muscular trabeculae [7]. The aortic valve was replaced because of thickened and calcified aortic cusps in 2 patients, severe destruction caused by endocarditis in 1, and annuloaortic ectasia with an aneurysm of the ascending aorta (composite graft) in 1. One iatrogenic aortic cusp lesion and one caused by endocarditis had to be repaired, two commissurotomies were performed, and one muscular subvalvular pulmonary stenosis was resected. Intraoperative transesophageal echocardiography (routinely performed since 1987) revealed a major residual LVOT gradient in 1 patient who had to undergo a more extensive myectomy on a second pump run.
Cardioprotection also improved during the study period. Initially all patients had operation under whole-body hypothermia and electrically induced ventricular fibrillation. Patients operated on between 1977 and 1988 received antegrade crystalloid cardioplegic solution and later, antegrade and retrograde blood cardioplegic solution. Today, isolated septal myectomy is performed under normothermic condition. The mean cardiopulmonary bypass time was 61 ± 19 minutes and the mean aortic cross-clamping time, 33 ± 16 minutes.
Follow-up
Clinical follow-up was obtained by review of patient records or questionnaires sent to the patient or the physician. Median follow-up was 10.6 years (mean follow-up, 11.7 ± 7.5 years; range, 0 to 30 years) with a cumulative total follow-up of 1,283 patient-years. Follow-up was complete on July 31, 1996, for 95 patients (86%).
Echocardiographic evaluation
Preoperative and postoperative evaluation was performed by transthoracic echocardiography. The following echocardiographic techniques were used: since 1974, M-mode and since 1979, cross-sectional and M-mode. Doppler echocardiography was added in 1981. The systolic pressure gradient across the LVOT was assessed quantitatively by Doppler ultrasound. Currently all patients are examined before operation, early after operation, and late postoperatively, ie, with follow-up intervals of 2 to 3 years. A total of 356 echocardiographic studies were analyzed, preoperative studies from 64 patients and postoperative studies from 94.
Left ventricular dimensional measurements were performed at end-systole and end-diastole. They were carried out according to the conventions of the American Society of Echocardiography [8] and included standard-level septal wall thickness, posterior wall thickness at end-diastole, and LV and left atrial internal dimensions at end-systole and end-diastole. Maximal end-diastolic thickness of the septal wall in the LVOT was also determined.
Left ventricular chamber dilatation has been defined as an increase of more than 2% per year in end-diastolic ventricular diameter combined with a decrease of 2% per year in midventricular systolic fractional shortening [9]. Because these criteria cannot be applied in the perioperative period, the incidence of left ventricular chamber dilatation was determined only in patients with repeated measurements during the early and late follow-up studies (n = 56).
Statistical analysis
Actuarial survival and event-free survival were calculated using the Kaplan-Meier method. Predictors of death and event-free survival were calculated using multivariate Cox regression analysis. Echocardiographic results were compared by paired Student’s t test. A p value of less than or equal to 0.05 was considered significant. Calculations were performed using SPSS for Windows 6.0.
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Results |
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TopAbstractIntroductionPatients and methodsResultsCommentReferences |
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Complications and reinterventions
All cardiac reinterventions were related to the HOCM itself or to sequelae of the operation. Two patients underwent reoperation on the same day, 1 for a major LVOT gradient and 1 for an iatrogenic aortic cusp lesion. One small ventricular septal defect that had been noticed 3 days after myectomy had to be closed and a substantial residual LVOT gradient combined with persisting mitral valve regurgitation caused two reoperations, a ventricular deptal defect patch closure and a modified Konno operation with replacement of the mitral valve, respectively. One patient with a major residual LVOT gradient and mitral regurgitation and 1 with major aortic stenosis (bicuspid leaflets) were treated by more extensive muscular resection and mitral or aortic valve repair. Only 1 patient had reoperation for late aortic valve regurgitation. One bioprosthesis had to be replaced because of failure. Two patients died as a result of reoperation; a child died after the third intervention and 1 patient had development of an intractable chylothorax. The interval between initial myectomy and reoperation ranged from several days to 17 years (mean interval, 6.0 ± 5.8 years).
Five patients had development of complete heart block as a result of septal myectomy. They were treated with a dual-chambered pacemaker.
Postoperative medication
Before 1976, patients continued to receive ß-blockers after operation. Since 1978, as previously described [10], all patients have been treated medically with verapamil hydrochloride on a long-term basis. Eighteen patients seen with signs of congestive heart failure were treated with diuretics and angiotensin-converting enzyme inhibitors for 10 ± 8 years after operation. Early postoperatively, patients were given warfarin sodium as prophylaxis against thromboemboli originating from the rough surface of the myectomy site. In the absence of other indications, anticoagulation was discontinued after 3 months.
Survival
The causes of late death were either cardiac or probable cardiac in 25 (83%) of 30 patients. Overall actuarial survival rates at 1 year, 5 years, 10 years, 15 years, and 20 years were 95%, 93%, 80%, 72%, and 53%, respectively (Fig 1). Univariate regression analysis detected the following risk factors: NYHA class III or IV, congestive heart failure, need of additional procedures, moderate to severe mitral regurgitation, history of pulmonary edema, duration of symptoms, and persistence of atrial fibrillation. Multivariate analysis identified NYHA class III or IV, congestive heart failure, and need of additional procedures as independent risk factors. Table 1 summarizes the results.
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More than half of all patients (61/110, 56%) showed left bundle-branch block after septal myectomy.
Functional classification and recurrence of symptoms
Most patients showed significant and long-term improvement in functional classification. One year after operation, 91% of the patients were in NYHA class I or II, and no patient was in class IV. Ten years later, 88% were still in NYHA class I or II and none in class IV (Fig 3).
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3 years after operation), and late postoperative (
6 years postoperatively) (Table 3). Soon after operation, maximal instantaneous LVOT pressure gradient at rest decreased from a preoperative value of 81 ± 42 mm Hg to 13 ± 13 mm Hg (p < 0.001), maximal septal wall thickness in the LVOT from 21.0 ± 5.3 mm to 17.5 ± 5.7 mm (p < 0.001), and septal wall thickness, measured at the standard level, from 20.5 ± 5 mm to 19.1 ± 4 mm (p = not significant). Systolic anterior motion of the anterior mitral valve leaflet disappeared during the early postoperative period in 25 (40%) of 63 patients. There was also a significant reduction in the end-systolic left atrial diameter from 45.0 ± 8.3 mm to 41.5 ± 7.3 mm (p = 0.003). In addition, a reduction in systolic fractional shortening from 0.45 ± 0.09 to 0.40 ± 0.08 (p = 0.007) and a decrease in the posterior wall thickness from 13.1 ± 2.5 mm to 12.1 ± 2.3 mm (p = 0.008) were found.
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Aortic regurgitation was considered trivial in 6 patients and mild in 2 preoperatively. Postoperatively, 28 patients were seen with trivial, 4 with mild, and 1 with moderate aortic regurgitation. As already mentioned, 2 patients with severe regurgitation underwent reoperation, 1 in the first week after transaortic myectomy and the second 9 years after the first intervention.
Although systolic anterior motion of the mitral valve disappeared completely during long-term follow-up, mitral regurgitation was present in 43 patients but was considered to be trivial or mild in all. As mentioned, 2 patients underwent late mitral valve reoperation because of persistent regurgitation.
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Comment |
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TopAbstractIntroductionPatients and methodsResultsCommentReferences |
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The present study is compared with others [7, 11–18] in Table 4. The results show that septal myectomy eliminates LVOT gradients and diminishes symptoms and mitral valve incompetence for a long time in most patients. In addition, early postoperative mortality is very low, and long-term follow-up is good. However, some patients may have left ventricular dilatation late after myectomy [9]. Hypertrophic obstructive cardiomyopathy is a rare disorder, and therefore most series report similar long observation periods. Patients are often severely limited (65% in NYHA class III or IV) and have a high LVOT gradient (average gradient, 70 mm Hg). An increasing number of additional cardiac procedures are necessary (28%), with bypass grafting representing half of them. The role of mitral valve operations varies across different institutions, but altogether, mitral replacement represents only 5% of the total of 1,178 operations.
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Despite postoperative aortic regurgitation, which is probably due to intraoperative leaflet trauma or resection of ventricular muscle too close to the aortic annulus, the transaortic approach remains our preferred technique, as aortic regurgitation is mostly only trivial or mild [19]. Only 2 patients required reoperation because of major aortic regurgitation.
Progressive dilatation of the left ventricle has been observed repeatedly in medically as well as surgically treated patients with HOCM [9]. It was present in 17 of our patients. It can be argued that septal myectomy provokes dilatation of the left ventricle in long-term follow-up. However, the incidence in moderately to severely symptomatic patients with medical treatment of HOCM is yet unknown. Furthermore, only 18 of the 106 patients surviving the perioperative period had development of clinically overt congestive heart failure during long-term follow-up. Most of these patients were severely symptomatic before operation. Thus, dilatation of the left ventricle can possibly be prevented if patients undergo operation at a relatively early stage of disease.
The expanded cross-sectional area of the LVOT diminishes or eliminates systolic anterior motion of the anterior mitral valve leaflet and may simultaneously alleviate mitral regurgitation. In our patients, mitral regurgitation did not worsen during long-term follow-up, and only patients with moderate to severe mitral regurgitation at baseline needed additional mitral valve procedures, although a diversity of structural mitral valve alterations exists in HOCM [20]. Septal myectomy can be combined with mitral valve repair. However, the role of the latter in these patients must still be determined. It is not possible to evaluate the role of the different repair techniques used depending on the underlying lesion in our small subgroup of 10 patients. Replacement may remain a possibility for select patients with severe intrinsic disease of the mitral valve, but it appears to worsen the prognosis [12].
Long-term prognosis and predictors of survival
Because of the relative rarity of HOCM, there are currently no long-term results comparing medically and surgically treated patients in a randomized, prospective trial. Therefore, the optimal treatment of these patients is still controversial [2–5, 15, 17, 21]. The survival of our patients compares favorably with natural history studies [22]. In addition, multivariate analysis has allowed us to identify subgroups of patients with relatively low risk during long-term follow-up. On the other hand, patients with advanced disease seen with severe symptoms related to diastolic dysfunction had a worse outcome. In combination with additional surgical procedures, the risk of death was even greater. Thus, it seems advisable to operate early on patients with related disorders that require an additional surgical procedure before they become severely symptomatic. Furthermore, patients with some but not all possible symptoms of HOCM had a much better prognosis after operation. Although our data do not allow a direct comparison with the natural history, patients with progressively symptomatic HOCM should not have operation too late, as survival as well as symptom-free survival is many times higher in mildly to moderately symptomatic patients than severely symptomatic patients.
Age has been repeatedly described as an independent predictor of death in surgically [12, 14, 15] and medically [22] treated patients. However, our data did not show a relation between age and risk of a bad outcome. Although there is no easy explanation for this finding, the relatively small subgroups of patients who underwent surgical therapy either when they were very young or old make statistical comparison difficult. Therefore, differences may be observed by chance and not as a significant finding. In addition, an even slightly higher risk in some age groups does not mean that these patients do not benefit from septal myectomy. In our series, 12 patients who were seen with symptomatic HOCM in childhood had operation and a prognosis as good as that of the other patients.
Echocardiographic findings
Our echocardiographic data expand those in previous reports [7, 9, 12, 15]. This study confirms the finding that septal myectomy may lead to a regression in not only the surgically treated septum but also the posterior wall. Further, the left atrial dimension decreased in short-term and medium-term follow-up, thus indicating improvement in diastolic dysfunction after septal myectomy, although it progressed in long-term follow-up. Thus, a high pressure gradient in the LVOT seems to further impair left ventricular myocardium, even in parts without excessive hypertrophy. It is well known that patients with symptoms of aortic stenosis have a bad prognosis and that relief of the pressure gradient over the aortic valve is necessary to prolong survival. Thus, it can be hypothesized that a high pressure gradient in the LVOT is an independent risk factor for a bad outcome and that relief of the gradient improves survival. This may explain a possible benefit of septal myectomy regarding survival in patients with HOCM.
Conclusions
This relatively large series with a mean follow-up exceeding 10 years demonstrates a good outcome for patients with advanced HOCM after surgical septal myectomy. It further indicates that patients should have operation before they become severely symptomatic (eg, NYHA III or IV and overt congestive heart failure), particularly if they need additional surgical procedures. This may be of more importance given the finding that relief of the LVOT pressure gradient favorably influences remodeling of the left ventricle during midterm follow-up.
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TopAbstractIntroductionPatients and methodsResultsCommentReferences |
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