TREATMENT OF HYPERTROPHIC CARDIOMYOPATHY: POINT-COUNTERPOINT
New treatment strategies for hypertrophic obstructive cardiomyopathy
Alcohol ablation of the septum: the new gold standard?
Otto M. Hess, MD*,* and
Ulrich Sigwart, MD, FRCP
* Swiss Cardiovascular Center, Bern, Switzerland
Division of Cardiology, University Hospital, Geneva, Switzerland
Manuscript received June 9, 2004;
accepted August 16, 2004.
* Reprint requests and correspondence: Dr. Otto M. Hess, Professor of Cardiology, Swiss Cardiovascular Center, University Hospital, 3010 Bern, Switzerland (Email: otto.hess{at}insel.ch).
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Abstract
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Hypertrophic cardiomyopathy is a primary myocardial disorder with an autosomal pattern of inheritance characterized by inappropriate myocardial hypertrophy. Annual mortality has been reported to be 1% to 2% and sudden death represents the most common cause. Treatment strategies are 1) medical therapy in patients with mild to moderate symptoms, 2) reduction of septal hypertrophy by surgical myectomy or alcohol ablation, and 3) implantation of an automatic cardioverter-defibrillator in the presence of non-sustained ventricular tachyarrhythmias. A debate has been started on whether surgical myectomy or alcohol ablation of the septum is the appropriate treatment for hypertrophic obstructive cardiomyopathy. Surgical (transaortic) myectomy has been the gold standard in the past 20 to 30 years for treatment of symptomatic patients with significant hemodynamic outflow tract obstruction. However, modern interventional technologies allow reduction of the myocardial septum by injection of alcohol into the first or second septal branch under guidance of two-dimensional (2D)-contrast echocardiography. This percutaneous technique not only has a lower morbidity than surgical myectomy but can be guided precisely by 2D echocardiography. One potential complication is transient (<30%) or permanent (<10%) atrioventricular block III; however, this complication is relatively rare. A randomized trial comparing the two treatment modalities is lacking, and the chance is small that such a trial will be performed because alcohol ablation can be done with high success and low complication rates, leaving only complex interventions (with valvular reconstructions and so on) for surgical myectomy.
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Abbreviations and Acronyms
| | HCM = hypertrophic cardiomyopathy | | HOCM = hypertrophic obstructive cardiomyopathy |
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Hypertrophic cardiomyopathy (HCM) is characterized by asymmetric hypertrophy of the septum with or without dynamic obstruction of the outflow tract (1–3) and increased diastolic filling pressure (= diastolic dysfunction). Hypertrophic cardiomyopathy is a primary myocardial disorder with an autosomal pattern of inheritance. The prevalence of HCM in the general population has been estimated as 1:500, higher than was previously postulated. Several genetic studies have described HCM as a heterogeneous disease of the sarcomers that involves more than 150 different mutations in at least 10 different contractile proteins. This genetic complexity leads to a wide diversity in cardiac morphology, pathophysiologic features, and clinical manifestations even in a single family (3–5). Annual mortality for HCM in an unselected population has been reported to be about 1% to 2%, and sudden death represents the most common cause. Sudden death is assumed to be due to idiopathic ventricular arrhythmias, but hemodynamic factors and myocardial ischemia may be involved as well (4,5). Treatment strategies in HCM (Fig. 1) are three-fold: 1) medical therapy in patients with mild to moderate symptoms, 2) reduction of the myocardial septum by surgery or alcohol ablation in patients with severe symptoms or significant outflow tract obstruction (6–8), and 3) implantation of an automatic cardioverter-defibrillator in the presence of nonsustained ventricular tachyarrhythmias (5).
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Figure 1 Treatment strategy in hypertrophic cardiomyopathy (HCM). ICD = implantable cardioverter-defibrillator; NSVT = nonsustained ventricular tachycardia.
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Surgical myectomy has been the gold standard for symptomatic patients with significant hemodynamic outflow tract obstruction (systolic pressure gradient at rest  50 mm Hg, after provocation 100 mm Hg) for more than 20 years. Long-term follow-up studies after septal myectomy have shown excellent results with low morbidity and mortality (6). However, dilation of the left ventricle after surgical myectomy and the occurrence of aortic regurgitation after transvalvular reduction of the myocardium have been reported as potential complication of this procedure. In 1996, Sigwart (7) introduced a new catheter-based nonsurgical reduction therapy of the interventricular septum by infusion of small amounts of pure alcohol into the first or second septal branch of the left anterior decending coronary artery. After early skepticism, this percutaneous treatment strategy has led to a new treatment option without the need for opening the chest and ascending aorta for removal of the excessive myocardium in the left ventricular outflow tract (8). This technique has gained great popularity in the past few years and has led to a rapid expansion of this treatment mainly in European countries (9). Complications associated with alcohol ablation of the septum have been rare and in the range of the surgical myectomy. Transients of permanent atrioventricular block III have been reported to be somewhat higher than after surgery. However, temporary pacemaker implantation during the procedure has solved the problem of transient block, and permanent pacemaker implantations have decreased from 25% to <10% with the reduction in the amount of injected alcohol (8). The fear of higher incidence of tachyarrhythmias after ablation has never been substantiated.
Most centers with experience in nonsurgical reduction of the interventricular septum by alcohol injection (9) have adopted this technique as a first line treatment of patients with hypertrophic obstructive cardiomyopathy (HOCM). The surgical treatment of HOCM has been reserved for patients with comorbidities such as organic mitral regurgitation or severe coronary artery disease requiring coronary bypass grafting, although simultaneous treatment of coronary artery disease by percutaneous interventions with stent implantation and alcohol ablation of the septum has been performed in patients with HCM.
Catheter-based treatment for HOCM has received much attention and has become the treatment of choice. Surgery is an effective treatment strategy but is associated with considerably higher perioperative morbidity. Surgical myectomy was the treatment of choice for the past 40 years, whereas alcohol ablation of the septum is the treatment of choice for patients with HOCM in the 21st century. It is clear that answering the question whether alcohol ablation or surgical myectomy is the treatment of choice would require a randomized trial comparing these two treatment modalities in a larger population of 240 patients in each group (80% power; event rate 7% in population 1 and 15% in population 2). It would require many centers worldwide to obtain this number of patients in a reasonable time span. However, for the invasive cardiologist who is doing alcohol ablation, it is clear that the percutaneous approach is much easier and is successful in many patients who would be hard to enroll in a randomized trial. Thus, it appears obvious to us that alcohol ablation is the treatment of choice for the new century.
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