Sudden arrhythmic cardiac death - mechanisms, resuscitation and classification: the Seattle perspective

A ventricular arrhythmia is a life-threatening event often occurring after a heart attack that is characterized by an abnormal beating of the lower chambers of the heart called the ventricles. Patients with a recent history of heart attack frequently develop a type of arrhythmia called ventricular fibrillation which may lead to sudden cardiac death (cardiac arrest). In fact, seventy-five percent of patients with a cardiac arrest have ventricular fibrillation. Sudden cardiac death is a major health problem in the United States affecting 200,000 to 600,000 persons annually with major resources being allocated to identify the causes and possible treatments of this affliction. Methods used to treat cardiac arrest include cardiopulmonary resuscitation in which a paramedic or other person physically compresses the patient's chest causing the heart to beat while intermittently breathing into the patient's mouth, and defibrillation in which the normal beat of the ventricle is restored through chemical or electrical means. The implementation of these techniques prevents the onset of brain damage and death. A recent study reported the survival rate and factors influencing this rate in 447 cardiac arrest patients from Seattle. The initial resuscitation rate was 60 percent, but only 26 percent survived in the long-run. Risk factors associated with the development of cardiac arrest include: poor function of the left ventricle; the presence of congestive heart failure; a prior history of cardiac arrest, heart attack, or smoking; disease of the blood vessels supplying the heart; advanced age; low blood pressure; and being of the male gender. In order to assess the effectiveness of therapy, cardiac deaths should be classified as either arrhythmic or non-arrhythmic in nature. Persons who died a non-arrhythmic cardiac death most likely had effective treatment of their ventricular fibrillation. It is suggested that an easier way to gauge the effectiveness of antiarrhythmic therapy is to measure the total amount of cardiac deaths. (Consumer Summary produced by Reliance Medical Information, Inc.)