Objectives: We sought to evaluate the contribution of left ventricular (LV) dysfunction toward occurrence of sudden cardiac death (SCD) in the general population, and to identify distinguishing characteristics of SCD in the absence of LV dysfunction.
Background: Patients who manifest warning symptoms and signs are more likely to undergo evaluation before SCD. Although prevalence of LV dysfunction in this subgroup may overestimate the prevalence in overall SCD, this is the only means of assessment in the general population.
Methods: All cases of SCD in Multnomah County, Oregon (population 660,486; 2002 to 2004) were prospectively ascertained in the ongoing Oregon Sudden Unexpected Death Study. We retrospectively assessed LV ejection fraction (LVEF) among subjects who underwent evaluation of LV function before SCD (normal: > or =55%; mildly to moderately reduced: 36% to 54%; and severely reduced: < or =35%). Of a total of 714 SCD cases (annual incidence 54 per 100,000), LV function was assessed in 121 (17%).
Results: The LVEF was severely reduced in 36 patients (30%), mildly to moderately reduced in 27 (22%), and normal in 58 (48%). Patients with normal LVEF were distinguishable by younger age (66 +/- 15 years vs. 74 +/- 10 years; p = 0.001), higher proportion of females (47% vs. 27%; p = 0.025), higher prevalence of seizure disorder (14% vs. 0%; p = 0.002), and lower prevalence of established coronary artery disease (50% vs. 81%; p < 0.001).
Conclusions: In this community-wide study, only one-third of the evaluated SCD cases had severe LV dysfunction meeting current criteria for prophylactic cardioverter-defibrillator implantation. The SCD cases with normal LV function had several distinguishing clinical characteristics. These findings support the aggressive development of alternative screening methods to enhance identification of patients at risk.