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Ann Thorac Surg 2000;69:1732-1735
© 2000 The Society of Thoracic Surgeons

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Original articles: Cardiovascular

Long-lasting improvement after septal myectomy for hypertrophic obstructive cardiomyopathy

^a Department of Cardiac and Thoracic Surgery, Vanderbilt University School of Medicine, and the Surgical Service, Department of Veterans Affairs Nashville Medical Center, Nashville, Tennessee, USA
^b Division of Adult Cardiology, Vanderbilt University School of Medicine, and the Surgical Service, Department of Veterans Affairs Nashville Medical Center, Nashville, Tennessee, USA
^c Division of Pediatric Cardiology, Vanderbilt University School of Medicine, and the Surgical Service, Department of Veterans Affairs Nashville Medical Center, Nashville, Tennessee, USA

Address reprint requests to Dr Merrill, Department of Cardiac and Thoracic Surgery, Vanderbilt Clinic, Vanderbilt University School of Medicine, Room 2986, 1301 22nd Ave S, Nashville, TN 37232–5734
e-mail: walter.merrill{at}surgery.mc.vanderbilt.edu

Presented at the Forty-sixth Annual Meeting, Southern Thoracic Surgical Association, San Juan, Puerto Rico, November 4–6, 1999.

	Abstract

Top Abstract Introduction Material and methods Results Comment References

 
Background. The most effective treatment of symptomatic patients with hypertrophic obstructive cardiomyopathy is still disputed. Treatment options include medical therapy, pacemaker insertion, percutaneous transluminal septal myocardial ablation, mitral valve replacement, and surgical resection of obstructing muscle. The long-term results of the various treatment options are not well defined. We aimed to demonstrate that septal myectomy is efficacious in reducing or abolishing left ventricular outflow tract gradient and leads to long-lasting symptomatic improvement in most patients.

Methods. Twenty-two consecutive patients had septal myectomy between 1981 and the present. Their records were reviewed to document the details of their preoperative status, hospital course, their subsequent clinical outcome, and current status.

Results. Mean age at operation was 31.3 years. Preoperatively all patients were disabled by typical symptoms despite aggressive medical treatment. Mean resting gradient was 78 mm Hg. Nine patients required simultaneous associated cardiac procedures. There were no perioperative deaths and minimal morbidity. Two patients died at 6 and 9 years postoperatively of congestive heart failure and arrhythmias. Long-term survivors have been followed up for a mean of 6.6 years. Currently all have minimal or no symptoms. The mean resting gradient was 12 mm Hg. No patient has required reoperation for residual obstruction.

Conclusions. Septal myectomy reduces or abolishes left ventricular outflow tract gradient in hypertrophic obstructive cardiomyopathy. Myectomy provides long-lasting symptomatic improvement in most patients. The clinical status of patients late postoperatively can be affected by arrhythmias and myocardial dysfunction.

	Introduction

Top Abstract Introduction Material and methods Results Comment References

 
The most effective treatment of symptomatic patients with hypertrophic obstructive cardiomyopathy is not yet determined. Medical treatment with beta blockers or calcium-channel blockers can relieve symptoms effectively in many patients, but some patients remain severely symptomatic despite optimal medical therapy. There are several treatment options for symptomatic patients who do not respond adequately to medical therapy, including pacemaker insertion, percutaneous transluminal septal myocardial ablation, mitral valve replacement, and surgical resection of obstructing outflow tract musculature. The precise indications for, and the long-term results of, the various treatment options are not completely defined and remain somewhat controversial.

In many centers septal myectomy to relieve dynamic left ventricular outflow tract obstruction has become the procedure of choice for patients whose symptoms are refractory to medical treatment. Despite the achievement of overall satisfactory results, myectomy has not been universally accepted or adopted as a first-line treatment option. Objections have been raised concerning operative mortality and complication rates, which were fairly high in early surgical series. Septal myectomy has been shown to reduce the left ventricular outflow tract gradient in most patients who have this procedure. Its effect on diastolic dysfunction, which may be an important part of this condition, has been less certain. The long-term outcome of patients also might be affected by arrhythmias or late development of congestive heart failure despite a successful myectomy.

Several studies have documented improvement in symptomatology, hemodynamics, and exercise capacity after surgical intervention for hypertrophic obstructive cardiomyopathy. Good results have been reported for patients who had transaortic subvalvular myomectomy [1, 2]. In addition, overall satisfactory results have been obtained in patients who have had mitral valve replacement [3].

In recent years dual-chamber pacing has been proposed as a treatment option for patients who remain symptomatic despite adequate medical therapy. Advocates of this procedure have pointed out its lower risk and cost compared with operative intervention, and they have noted the beneficial results that have been reported by some investigators.

Another treatment option is percutaneous transluminal septal myocardial ablation, in which absolute alcohol is injected in one or more septal branches of the left anterior descending coronary artery. Some patients have benefited from a reduction in outflow gradient accompanied by reduced symptoms and improved exercise tolerance. However, some patients have had heart block requiring pacemaker implantation or arrhythmias, or have died. The long-term consequences of this procedure are not well known [4–6].

When considering the various treatment options and comparing them to each other and to medical therapy it is important to consider that despite adequate medical treatment with beta blockers, calcium-channel antagonists, and antiarrhythmic medications the yearly mortality rate of symptomatic patients remains between 1.5% and 5%.

The aim of the current study was to demonstrate that septal myectomy effectively reduces or abolishes left ventricular outflow tract gradient and that this procedure leads to long-lasting symptomatic improvement in most patients.

	Material and methods

Top Abstract Introduction Material and methods Results Comment References

 
Twenty-two consecutive patients had transaortic septal myectomy between 1981 and 1999. All patients had hypertrophic obstructive cardiomyopathy with a left ventricular outflow tract gradient at rest or with provocation. The diagnosis of hypertrophic obstructive cardiomyopathy was established by using standard echocardiographic criteria, including marked left ventricular hypertrophy, asymmetric septal hypertrophy, systolic anterior motion of the anterior leaflet of the mitral valve, and Doppler evidence of dynamic left ventricular outlflow tract obstruction at rest or after provocation with amyl nitrite or the Valsalva maneuver. Most patients had cardiac catheterization to confirm the echocardiographic findings. All patients had symptoms of chest pain, dyspnea on exertion, syncope, or presyncope. The symptoms were of sufficient severity to limit customary daily activities despite adequate medical treatment.

All patients had operations in which the transaortic septal myectomy technique was used. Concomitant additional operative procedures were done as indicated in several patients. Standard cardiopulmonary bypass with moderate hypothermia was used. Myocardial protection was achieved with crystalloid or cold blood cardioplegia and topical cooling of the heart. After aortotomy and retraction of the aortic valve leaflets the septal resection was initiated by making an incision beneath the nadir of the right coronary leaflet of the aortic valve and extending that incision deep into the interventricular septum and distally toward the apex of the heart. A second incision was then made parallel and to the left of the original incision. The two parallel incisions were joined superiorly with an additional incision, and a bar of muscle was excised extending deep into the septum and distally toward the apex of the heart. Additional myocardium was resected with careful scissor dissection to enlarge the trough created in the outflow tract. During the myotomy, the mitral valve was protected with a wide ribbon retractor. The left ventricular outflow tract was then inspected and palpated to assess the completeness of relief of outflow tract obstruction, the aortic valve leaflets were inspected, and the aortotomy was repaired. Operative methods remained fairly consistent over the course of this study; three primary surgeons performed the procedures.

In recent years intraoperative transesophageal echocardiography has been used to assess the adequacy of septal resection, the degree to which relief of outflow tract obstruction has been accomplished, and the presence and severity of mitral valve regurgitation.

Early mortality was defined as hospital death or death within 30 days postoperatively. Patients were followed up postoperatively in the outpatient clinic by one of the authors. Particular attention was paid to persistent symptoms and overall functional status.

	Results

Top Abstract Introduction Material and methods Results Comment References

 
There were 14 men and 8 women. The age range was 2 to 74 years, with a mean age at operation of 31.3 years. Resting left ventricular outflow tract gradient, as assessed either by echocardiography or by cardiac catheterization, varied from 10 to greater than 150 mm Hg. In patients who had provocative maneuvers, all had important increases in the left ventricular outflow tract gradient. In addition to a large left ventricular outflow tract gradient, there was also a large right ventricular outflow tract gradient at rest in 1 patient.

All patients had myectomy as described. Nine of the 22 patients required concomitant operative procedures. Right ventricular outflow tract resection was done in 1 patient. Aortic valve replacement with or without coronary artery bypass was required in 4 patients because of associated aortic valve pathology. Other concomitant procedures included mitral valve replacement in 1 patient, coronary artery bypass in 1 patient, closure of an ostium primum atrial septal defect in 1 patient, and an aortic valvotomy as well as relief of supravalvar aortic stenosis in 1 patient.

No patient had a surgically induced ventricular septal defect, and no patient experienced complete heart block requiring insertion of a pacemaker. One patient required mediastinal reexploration to control bleeding, and 1 patient had a perforated duodenal ulcer. There were no other instances of major perioperative morbidity. There were no perioperative deaths.

There were 2 late deaths, one at 6 years and one at 9 years postoperatively. The patient who had had complex multilevel repair, including myectomy, aortic valvotomy, and relief of supravalvar aortic stenosis initially did well postoperatively, but subsequently congestive heart failure and episodes of ventricular arrhythmia developed. This patient required insertion of an automatic internal defibrillator and eventually died while awaiting cardiac transplantation. The other patient who died late initially did well postoperatively for approximately 6 years, but congestive heart failure and episodic atrial fibrillation developed. This patient was noncompliant with his medical regimen and died 9 years postoperatively. In both patients who died late, postoperative investigations found minimal residual outflow tract obstruction. Congestive heart failure symptoms were ascribed to diastolic dysfunction.

The 20 long-term survivors have been followed up for up to 17 years, with a mean follow-up time of 6.6 years. One patient had an episode of cardiac arrest because of ventricular fibrillation 14 years postoperatively. An echocardiogram showed no resting gradient and only minimal gradient with provocation. The patient has subsequently done well on antiarrhythmic medication. The remaining patients have done well with minimal to mild symptoms. All survivors have had left ventricular outflow tract evaluation with either cardiac catheterization or echocardiography. Gradients at rest varied from 0 to 25 mm Hg, with a mean of 12 mm Hg. Provoked gradients varied from 0 to 35 mm Hg. Symptomatic improvement in the long-term survivors has been sustained. Currently all long-term survivors have minimal or no symptoms and improved functional class compared with their preoperative status.

	Comment

Top Abstract Introduction Material and methods Results Comment References

 
The results of this study confirm that patients with hypertrophic obstructive cardiomyopathy who continue to have symptoms of sufficient severity to affect their quality of life despite optimal medical treatment can undergo transaortic septal myectomy with low risk and a good long-term outcome. This is true even when myectomy is accompanied by additional cardiac procedures. There were no perioperative deaths, and there was infrequent perioperative morbidity. Postoperative investigations have shown abolition or reduction in left ventricular outflow tract obstruction, and no patient has required reoperation for residual outflow tract obstruction.

The symptoms of most patients have improved, and most patients have maintained that improvement for several years. However, symptomatic congestive heart failure has developed late postoperatively in some patients but has been shown to be caused by diastolic dysfunction rather than residual obstruction. Arrhythmias have developed in some late survivors, which have complicated their long-term treatment and have compromised long-term success.

Many patients with hypertrophic obstructive cardiomyopathy improve with medical therapy. We have used medical therapy as the first choice of treatment in symptomatic patients, and most have improved, at least temporarily, with beta blockers, calcium-channel blockers, and sometimes with antiarrhythmic medications. We and others have noted, however, that many patients will have early clinical improvement followed by symptomatic deterioration during the course of medical treatment. Patients who remain symptomatic after an adequate trial of medical therapy are considered potential candidates for operation.

In many patients the clinical condition seems to correlate more or less well with observed left ventricular outflow tract obstruction [7]. Elevated left ventricular systolic pressure is generally associated with increased myocardial hypertrophy, gradual deterioration of diastolic function, increased myocardial oxygen consumption, and evidence of myocardial ischemia.

Some authors have argued that abolition of the left ventricular outflow tract gradient leads to relaxation of the myocardium and improvement of diastolic function accompanied by reduction of left ventricular hypertrophy and mitral regurgitation. Echocardiographic observations after myectomy have confirmed that the thickness of the ventricular septum and left ventricular posterior free wall were reduced, and the left ventricular end-diastolic diameter was increased. Therefore, the abolition of the left ventricular outflow tract obstruction seems to result in a time-related regression of left ventricular hypertrophy with functional systolic and diastolic improvement [8].

Patients in whom angina or syncope was the predominant symptom seemed to improve particularly well after myectomy. However, patients who had dyspnea as the predominant symptom frequently improved postoperatively but commonly had residual symptoms and did not have the same degree of sustained improvement [9].

One of the concerns of long-term treatment is the possible occurrence of important arrhythmias or sudden death despite adequate relief of left ventricular outflow tract obstruction and despite continued medical therapy. The patient who died late of congestive heart failure while awaiting cardiac transplantation had a history of important arrhythmias as well, and this patient had an automatic implanted cardioverter defibrillator inserted. The other patient who died of congestive heart failure also had episodic atrial fibrillation that required treatment with amiodarone. An additional patient who had an episode of ventricular fibrillatory arrest 14 years postoperatively continues to do well with amiodarone therapy. The possible occurrence of arrhythmias or sudden death late postoperatively should be kept in mind, and the most appropriate use of antiarrhythmic therapy including, in some cases, implantation of an automatic cardioverter defibrillator, remains under investigation.

Alternatives to myectomy continue to be considered, including dual-chamber pacing, with which some patients have had relief of symptoms and decreased outflow tract gradient. However, some patients have no improvement or even a worsening of symptoms. Also, symptomatic improvement can occur even in the absence of documented hemodynamic improvement. Therefore, additional investigation of dual-chamber pacing will be necessary to define the indications for this therapy and its potential benefit [10]. A recently published study suggested that this mode of treatment is most successful and beneficial in patients 65 years old or older [11].

In patients with hypertrophic obstructive cardiomyopathy the goal of operation is to enlarge the cross-sectional area of the left ventricular outflow tract. When this is accomplished there is usually a diminution or abolition of systolic anterior motion of the anterior mitral valve leaflet. Commonly this alleviates mitral valve regurgitation. Most investigators favor resection of the obstructing musculature in patients with dynamic obstruction and varying degrees of mitral regurgitation, although others have recommended replacement of the mitral valve [12].

Some authors have advocated selective mitral valve replacement in patients whose measured septal thickness is less than 18 mm [3]. The rationale for this suggestion is the presumed increased risk of septal perforation by myotomy and myectomy in patients with a thin septum. However, other authors have found no correlation between ventricular septal thickness and risk of creation of a ventricular septal defect [2]. The surgeon can use intraoperative transesophageal echocardiography to determine the appropriate depth and length of the septal incision. The patient in our series who had mitral valve replacement concomitant with myectomy had severe mitral regurgitation both before the resection and immediately after resection. In view of the continued severe mitral regurgitation, the mitral valve was replaced when it became obvious that valve repair was not feasible. If the mitral valve is intact and functioning normally we do not use mitral valve replacement for relief of left ventricular outflow tract obstruction.

Overall 8 of the 22 patients were 18 years old or younger. The preoperative clinical characteristics and hemodynamic abnormality as well as the operative procedure, hemodynamic improvement, and symptomatic improvement postoperatively were similar to those in the adult patients. Clinical improvement persisted in the younger patients to the same degree that it did in the older patients. Overall, our results with myectomy in pediatric patients are consistent with those previously reported by other investigators [13].

	References

Top Abstract Introduction Material and methods Results Comment References

 

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Walter H. Merrill Davis C. Drinkwater, Jr Harvey W. Bender, Jr Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Merrill, W. H. Articles by Bender, H. W. Search for Related Content PubMed PubMed Citation Articles by Merrill, W. H. Articles by Bender, H. W., Jr Related Collections Related Article