13th International Congress
THE "NEW FRONTIERS"
OF ARRHYTHMIAS 1998

January 24-31, 1998
Marilleva, Trento, Italy

RT-30

Hypertrophic cardiomyopathy.
The implantable defibrillator

Martin Borggrefe, Michael Block, Günter Breithardt.
Westfälische Wilhelms-University, Department of Cardiology and Angiology and Institute for Research in Arteriosclerosis, Münster, Germany

Management and prognosis of patients with HCM

Although beta-blockers and calcium antagonists have been shown to improve symptoms in HCM, no controlled data are available which address the prognostic aspects. Prospective, randomized trials comparing beta-blockers or calcium antagonists versus placebo are lacking. The same holds true for surgical therapy such as myectomy or myotomy which is mostly performed in highly symptomatic class III or IV patients with HCM in the presence of a gradient. Retrospective analysis of some surgical series have shown a very low annual mortality rate of approximately 1-2% per year and revealed a significant better outcome following surgery as compared to historical control groups undergoing medical therapy alone. Although the hemodynamic changes that result from operation, have consistently been associated with an improved quality of life for the patient as manifested by a reduction in symptoms of congestion, chest pain and symptoms of impaired diastolic filling, the prognostic aspects of myectomy have not been studied in a randomized trial. It is of importance that the incidence of syncope following myectomy decreases from approximately 20-30% to 4-6% after surgery despite the fact that the incidence of non-sustained ventricular tachycardia during Holter monitoring is unchanged⁴. This supports the notion that non-sustained ventricular tachycardia may be an unspecific marker for electrical instability in these patients and may not be a useful, prognostic marker. Following successful surgery, approximately 20% of patients are known to have died of causes related largely to HCM. About 5-30% of deaths following myectomy or myotomy are sudden. These data emphasize that it is most appropriate to view myotomy/myectomy as a palliative rare than a curative procedure for HOCM. Therefore, patients with successful myectomy often require further pharmacological therapy for symptoms and in some patients, aggressive diagnostic procedures and treatment may be indicated for clinically important arrhythmias. Despite these observations, there may be a subgroup of patients with cardiac arrest and HOCM who may benefit from myectomy or myotomy alone. Recently, we studied prospectively 10 patients following cardiac arrest who underwent myectomy for HOCM⁵. Eight out of 10 patients had inducible sustained ventricular tachycardia or fibrillation prior to surgery. Following myectomy, only 0 to 6 ventricular responses were inducible in all 10 patients applying a stimulation protocol including up to 3 extrastimuli. No recurrent arrhythmic event occurred during a follow-up of 4.5 years in the absence of antiarrhythmic drugs. This preliminary observation may be explained by surgical removal of an "arrhythmogenic substrate" in some patients with HOCM and life-threatening tachyarrhythmias and may support a potential mechanism for the beneficial long-term results after surgical treatment. Therefore, in patients with cardiac arrest and inducible ventricular tachyarrhythmias, myectomy may be the treatment of choice and presents a curative approach.