Depression but not anxiety influences the autonomic control of heart rate after myocardial infarction

Aims It has been previously hypothesized that the adverse outcome observed in depressed patients after myocardia infarction might be due to an imbalan ce in autonomic nervous system activity. The aim of this study was to defin e the role of depressive and anxious symptoms in influencing autonomic cont rol of heart rate after myocardial infarction. Methods and Results The SD of RR intervals, baroreflex sensitivity, and dep ression and anxiety (Zung's scales) were assessed before discharge in 103 p atients with acute myocardial infarction; 32 were found to be depressed. Am ong the patients who were not taking beta -blockers, those with depression had significantly lower SDs of RR intervals and baroreflex sensitivity than did those without depression (96.3 +/- 22.2 ms vs 119.5 +/- 37.7 ms, P = . 016; 8.6 +/- 6.2 ms vs 11.8 +/- 6.5 ms/mm Hg, P = .01, respectively). No di fferences were Found when anxiety was considered or when beta -blockers wer e given. Among the patients not taking beta -blockers, there was a signific ant correlation between depression levels and both the SD of RR intervals ( r = -0.47) and baroreflex sensitivity (r = -0.40). Conclusions In patients with myocardial infarction, depression but not anxi ety negatively influences autonomic control of heart rate. beta -Blockers m odify these influences.