Increased left ventricular mass and decreased left ventricular systolic function have independent pathways to ventricular arrhythmogenesis in coronary artery disease

Abstract

Background: Following myocardial infarction, individual patients can have wide variations in the extent of left ventricular systolic dysfunction (LVSD) and increased left ventricular (LV) mass. Both affect the risk for sudden cardiac death, but only LV ejection fraction is used for risk prediction.

Objective: The purpose of this study was to evaluate the independent as well as the additive contributions of increased LV mass and decreased LV ejection fraction to sudden cardiac death in the general population.

Methods: In the ongoing Oregon Sudden Unexpected Death Study, we studied consecutive SCD cases (n = 191) and coronary artery disease controls (n = 203) from the Portland, Oregon, metropolitan area (population approximately 1,000,000; 2002-2008). Comparisons of echocardiographic LV mass obtained prior and unrelated to sudden cardiac death (SCD) were conducted, and a logistic regression model was used to evaluate the relationship between SCD, severe LVSD, LV mass, and other relevant clinical variables.

Results: In a multivariate model, both severe LVSD and left ventricular hypertrophy (LVH) were associated with increased SCD risk (odds ratio [OR] 1.9, 95% confidence interval [CI] 1.1-3.2 for severe LVSD; OR 1.8, 95% CI 1.1-2.9 for LVH). In patients with coexisting severe LVSD and LVH, risk of SCD was additive (OR 3.5, 95% CI 1.7-7.2). In the same model, increased age, atrial fibrillation/flutter, elevated creatinine, and diabetes independently increased risk, and use of angiotensin receptor blockers attenuated risk.

Conclusion: Reduced LV ejection fraction and increased LV mass had independent and additive effects on risk of sudden death. Despite the significant overlap between the two conditions, these findings point toward the existence of independent mechanistic pathways for ventricular arrhythmias that occur due to LVSD and LVH.

Figure 1

Frequency of LV hypertrophy (LVH, by measurement of echocardiographic LV mass) among LV function sub-groups in cases and controls. A greater prevalence of LVH was observed in case subjects, across all categories of LV systolic function.

Figure 2

Distribution of LV mass (normalized for body surface area) in cases and controls shows a rightward shift toward higher values in the case group.

Figure 3

Distribution of severe LV systolic dysfunction (LVSD) and LV hypertrophy (LVH) in cases vs. controls. Case subjects were more likely than control subjects to have co-existing severe LVSD and LVH.