Relation of depression to heart rate nonlinear dynamics in patients ≥60 years of age with recent unstable angina pectoris or acute myocardial infarction

Depression is common among older patients and it has been related to a worsened coronary prognosis. The basis for this association is controversial. The aim of this study was to ascertain whether patients with a recent acute coronary event show depression-related changes of heart rate variability (HRV) nonlinear dynamics. Alterations of the HRV have been recently shown to predict mortality in patients recovering from an acute myocardial infarction. In 52 patients greater than or equal to60 years (52% women) with recent (within 24 to 72 hours) unstable angina pectoris or myocardial infarction, we obtained conventional time- and frequency-domain HRV measurements, along with nonlinear HRV measurements, including SD of the instantaneous beat-to-bat variability (SDI), scaling exponent alpha1 (alpha1), and approximate entropy (ApEn) from 10-minute RR-interval recordings. We also evaluated the presence of clinical depression and measured its severity by means of a 21-item Hamilton Depression Scale. On admission to the coronary care unit, 19 patients (37%) were depressed; alpha1 was higher (1.23 +/- 0.21 vs 1.03 +/- 0.30, p < 0.05), whereas SD1 (10.4 +/- 3.7vs 14.4 +/- 7.3, p < 0.05)and ApEn (0.98 +/- 0.22 vs 1.16 +/- 0.15, p < 0.001) were lower in depressed patients. Also, alpha1 increased (r = 0.31, p < 0.05) and both SD1 (r = -0.46, p < 0.01) and ApEn (r = -0.28, p < 0.05) decreased with worsening depressive symptoms. In our sample, depression was associated with increased correlation and decreased complexity of the interbeat interval time series in older adults who had recently developed an acute coronary syndrome. (C) 2004 by Excerpta Medica, Inc.