Clinical Management for Survivors of Sudden Cardiac Death

Introduction Of the many possible cardiovascular causes of sudden death— arrhythmia, trauma, intracranial vascular catastrophes, and acute thrombosis or embolism affecting the heart or lungs—the present discussion is restricted to the arrhythmic causes and primarily to ventricular fibrillation. Not all episodes of ventricular fibrillation lead to death. As with atrial fibrillation, ventricular fibrillation may be both nonsustained and self-terminating or the patient may be rescued by bystanders or medical personnel who deliver a direct-current countershock to the patient’s heart before irreversible cellular or organ damage intervenes. Nonetheless, sustained ventricular fibrillation inevitably leads to death within minutes unless the fibrillation is terminated. In contrast, monomorphic ventricular tachycardia may continue for many minutes, hours, or even days—depending on the rate of tachycardia—without development of clinically significant hemodynamic compromise. Although some cases of sudden arrhythmic death have been attributed to asystole or electromechanical dissociation, in general, these findings represent the natural evolution of untreated ventricular fibrillation and are not primary causes of sudden death. Definition and Epidemiology Many investigators have grappled with defining sudden death. TorpPedersen, et al, suggest: “Since all death is (eventually) sudden and associated with cardiac arrhythmias, the concept of sudden death is only meaningful if it is unexpected, while arrhythmic death is only meaningful if life could have continued had the arrhythmia been prevented or terminated.” The authors further state: “Any practical classification of death being sudden or arrhythmic is highly dependent on the quality of available data to ensure that the suddenness was unexpected and that life could have continued if the arrhythmia had been prevented or treated.” Roberts has defined sudden death as “death which is nonviolent or nontraumatic, which is unexpected, which is witnessed, and which is instantaneous or occurs within a few minutes of an abrupt change in previous clinical state.” For current purposes, sudden cardiac death shall be defined as death occurring within minutes from unexpected ventricular fibrillation or as ventricular tachycardia that rapidly (within seconds) accelerates to ventricular fibrillation and that if prevented or immediately terminated, would allow the patient to return to their previous level of functioning for an indefinite period. Given this definition of sudden cardiac death, the task of declaring an Sudden cardiac death is believed to affect as many as 400,000 people each year in the United States and is therefore an important public health problem. A common cause of sudden cardiac death is ventricular fibrillation. This article reviews the clinical and electrophysiologic aspects of sudden arrhythmic death and discusses current clinical management for survivors of sudden death. Particular emphasis is placed on the implantable cardioverter-defibrillator (ICD).