Dying Suddenly - Sudden Cardiac Death
As originally observed by Macwilliam, there is an important link between SCD and arrhythmias. The vast majority of cases of SCD have been attributed to the occurrence of sudden fatal arrhythmias. There are 2 general arrhythmia mechanisms by which the heart can suddenly fail. If the heart stops beating completely, no blood flow will occur to the vital organs and death will occur after several minutes. If this were the cause of most sudden deaths, the invention of pacemakers to prevent cardiac standstill would have had a dramatic impact on sudden death rates. Unfortunately, pacemakers have had little impact on rates of SCD. As it turns out, the usual reason for sudden circulatory failure is an extremely fast rhythm, usually either ventricular tachycardia or ventricular fibrillation. When the heart beats extremely quickly, it does not have time to fill or to contract well, so that blood pressure falls. In addition, the heart itself is starved of nourishing blood flow at a time when its demand for fuel is high. Unless the rhythm is terminated and a normal rhythm is restored, death occurs after only a few minutes. Ventricular tachycardia and ventricular fibrillation have been documented in many victims of SCD at the scene and on ECG monitors. Those who survive are those who are helped early and whose rhythm is corrected as soon as possible by defibrillation.