Objective: Depression is a risk factor for mortality after acute myocardial infarction (AMI), possibly as a result of altered autonomic nervous system (ANS) modulation of heart rate (HR) and rhythm. The purposes of this study were to determine: a) whether depressed patients are more likely to have an abnormal HR response (i.e., abnormal turbulence) to premature ventricular contractions (VPCs), and b) whether abnormal HR turbulence accounts for the effect of depression on increased mortality after AMI.
Methods: Ambulatory electrocardiographic data were obtained from 666 (316 depressed, 350 nondepressed) patients with a recent AMI; 498 had VPCs with measurable HR turbulence. Of these, 260 had normal, 152 had equivocal, and 86 had abnormal HR turbulence. Patients were followed for up to 30 (median = 24) months.
Results: Depressed patients were more likely to have abnormal HR turbulence (risk factor adjusted odds ratio = 1.8; 95% confidence interval [CI] = 1.0–3.0; p = .03) and have worse survival (odds ratio = 2.4; 95% CI = 1.2–4.6; p = .02) than nondepressed patients. When HR turbulence was added to the model, the adjusted hazard ratio for depression decreased to 1.9 (95% CI = 0.9–3.8; p = .08), and to 1.6 (95% CI = 0.8–3.4; p = .18) when a measure of HR variability (LnVLF) was added. The hazard was found to differ over time with depression posing little risk for mortality in year 1 but greater risk in years 2 and 3 of the follow up.
Conclusion: ANS dysregulation may partially mediate the increased risk for mortality in depressed patients with frequent VPCs after an AMI.
ANS = autonomic nervous system; HR = heart rate; VPC = premature ventricular contraction; AECG = ambulatory electrocardiography; AMI = acute myocardial infarction; LnVLF = natural log of very low frequency; LVEF = left ventricular ejection fraction; TO = turbulence onset; TS = turbulence slope.