Sudden cardiac death (SCD) is defined as death from cardiovascular causes shortly after the onset of symptoms in a person without a condition that would otherwise appear fatal.¹ Estimates as to the impact of SCD on our health care system put the total annual mortality up to 450,000, which is 63% of all deaths from cardiovascular causes.² Mechanisms of arrhythmic SCD include³,⁴:

In a series of young sudden death patients <40 years old without known heart disease, the most common etiology was still cardiac (73%). Coronary heart disease (CHD) was the most common cause in those >30 (58%), while myocarditis (22%), hypertrophic cardiomyopathy (HCM) (22%), and conduction system disease (13%) were more common in those <20 years of age.⁵ (See Table 7-1.)

SCD is associated with a high incidence of mortality, and the ability to rescue the patient probably depends most on timely interventions that restore perfusion to and protect vital organs. Unfortunately, many patients will die in the prehospital setting or early in the resuscitative effort. For out-of-hospital sudden death, 20% make it to the hospital, half of them will die in the hospital, and only about half of the survivors will have any “meaningful” survival. Hence in total only about 5% of patients who sustain an out-of-hospital sudden death in the absence of ICD therapy will have a good outcome. In contrast, the survival with early defibrillation when the initial rhythm is VT or VF is substantially higher with up to 40% of those being discharged with a good neurologic outcome and is the single factor most strongly associated with a good outcome.⁴,⁶ Those that regain a sustained perfusing rhythm are candidates for further therapy as outlined in Figure 7-1.