Clinical significance and management of ventricular arrhythmias in heart failure

Abstract

Ventricular arrythmias are a frequent finding in patients with heart failure is a major underlying condition which is correlated to sudden death. Therefore, both sudden death and death from progression of heart failure strongly overlap. Besides long-term ECG recording, newer diagnostic techniques have been developed. The prognostic significance of the signal-averaged ECG in patients with advanced left ventricular dysfunction in the presence of coronary artery disease has been demonstrated; however, in patients with dilated cardiomyopathy, signal-averaging for detection of late potentials has not yet been clearly established as a useful diagnostic tool. Furthermore, heart period variability has been shown to correlate to overall mortality but not to a specific mechanism. Finally, programmed ventricular stimulation, though useful in patients with left ventricular dysfunction and/or heart failure in the setting of coronary artery disease, is of questionable significance in patients with dilated cardiomyopathy. With increasing degrees of left ventricular dysfunction, the efficacy of antiarrythmic drugs decreases. On the other hand, with increasing degrees of heart failure, antiarrythmic drugs demonstrate a greater negative inotropic effect, more frequent proarrythmic effects, and more frequent bradyarrythmias. Currently, several ongoing amiodarone trials are assessing different approaches of antiarrythmic treatment in patients with heart failure. The European Myocardial Infarction Amiodarone Trial (EMIAT) addresses the role of amiodarone in patients after myocardial infarction with an ejection fraction of 40% or less irrespective of spontaneous ventricular arrythmias; the Canadian Amiodarone Myocardial Infarction Arrythmia Trial (CAMIAT) includes patients after myocardial infection with 10 or more VPBs per hour or one or more runs of ventricular tachycardia on 24-h ECG monitoring; and the US-Veteran's Administration Study in patients with congestive heart failure (US-VA) included patients with a history of congestive heart failure and reduced ventricular function. Additionally, the Survival with Oral d-Sotalol (SWORD) Trial included patients after myocardial infarction with a low ejection fraction irrespective of spontaneous ventricular arrythmias. Recently, the implantable cardioverter-defibrillator (ICD) has gained widespread acceptance as a first line treatment modality for patients with documented life-threatening ventricular tachyarrythmias. The ability if ICD devices to terminate ventricular tachycardia or fibrillation has been clearly demonstrated. However, whether overall cardiac mortality may also be significantly improved especially in patients with severely impaired left ventricular function is less clear. On the other hand, considering the high risk of patients with moderate to severe heart failure for sudden cardiac death, information on the impact of prophylactic implantation of ICD devices in high risk patients would be desirable. Recently, the Cardiomyopathy Trial was started, assessing the prophylactic use of ICD systems in patients with dilated cardiomyopathy, heart failure of NYHA class II or III, and absence of symptomatic ventricular arrythmias. The role of ventricular arrythmias and sudden death in patients with heart failure is still an enigma. Currently, we should treat heart failure but present data do not support antiarrythmic drug treatment of asymptomatic complex arrythmias detected on Holter monitoring. In patients with documented sustained ventricular tachycardia or fibrillation or in patients who have been resuscitated from sudden cardiac death, the subcutaneously implantable ICD will probably establish itself as a first line treatment modality in the near future. However, given the poor survival rate of out-of-hospital cardiac arrest, the most important challenge will be to clearly identify and prophylactically treat potential reversible or only transiently active arrythmogenic factors in this high risk patient population. In the light of this view, transient neurohumoral activation, transient ischaemia, and other methods have to be controlled before exerting their influence on the myocardial substrate in congestive heart failure which is potentially susceptible to ventricular tachycardia and fibrillation.