Mechanism of Sudden Death

The mechanism of sudden death in most individuals with coronary artery disease is the sudden onset of ventricular tachycardia, which either is sustained or, in most cases, progresses to ventricular fibrillation (approximately 80%). This has been demonstrated in individuals wearing portable cardiac monitors who collapsed and died with the terminal event's being recorded. Asystole or a bradyarrhythmia accounts for the remaining 20% of cases of sudden cardiac death.14,15

The death rate following out-of-hospital cardiac arrests is dependent on the type of arrhythmia that caused the arrest, prompt initiation of cardiop-ulmonary resuscitation (CPR), and how soon after arrest defibrillation is instituted. The public's perception of the success of CPR is based to a great degree on information communicated to them by the media — especially television. An unrealistic impression is routinely conveyed. In a television study of CPR, 75% of "patients" survived the immediate arrest, with apparently 67% surviving to discharge.16 Virtually none had neurological sequelae.

The arrest was due to trauma in the majority of cases, with the patients typically young.

In actuality, short-term success of CPR (the return of the patient's blood pressure and pulse for 1 h) is, at most, 40%, with survival until discharge from the hospital varying from 2-30 % for cardiac arrests outside the hospital.15-16 While 83% of the patients on television were non-elderly, in reality, the elderly are the most common group. On TV, 28% of the underlying diseases were primary cardiac, in reality, 75-95% are cardiac in origin. For the elderly, long-term survival after cardiac arrest outside the hospital is 5% or less. In arrests due to trauma, the long-term survival rate varies from 0-30%.16

Schneider reviewed 19,955 patients in 98 studies who had CPR after in-hospital cardiac arrest.17 Resuscitations were successful in 15% of cases. The rate of CPR success did not change over time. The nature of the cardiac rhythm affected CPR success rates with 20% success with ventricular fibrillation or tachycardia; 7% with electromechanical dissociation; 6% with asystole; and other, 10%. A small number of patients (2%) with successful resuscitation had central nervous system impairment.

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