Nighttime heart rate and survival in depressed patients post acute myocardial infarction

To determine if: 1) depressed patients with a recent acute myocardial infarction (AMI) have higher nighttime heart rate (HR) than nondepressed patients, and 2) elevated nighttime HR is associated with decreased survival post AMI. Depression is a risk factor for mortality post AMI. It is also associated with sleep disturbances and with elevated HR, which may be more pronounced at night. Resting and 24-hour HR have been found to predict mortality in patient and community samples.

Ambulatory electrocardiographic data were obtained from 333 depressed patients and 383 nondepressed patients with recent AMI. They were followed for up to 30 months (median = 24 months).

Depressed patients had higher nighttime HR (70.7 +/- 0.7 versus 67.7 +/- 0.6 beats per minute (bpm); p = .001), and daytime HR (76.4 +/- 0.7 versus 74.2 +/- 0.6 bpm; p = .02) than nondepressed patients, even after adjusting for potential confounds. Depression (hazard ratio (Haz R) = 2.19; p = .02) and nighttime HR (Haz R = 1.03; p = .004), but not daytime HR, predicted survival after adjusting for other major predictors and for each other. The interaction between nighttime HR and depression on survival approached, but did not achieve, significance (p = .08).

Mean day and nighttime HR values are higher in depressed patients than in nondepressed patients post AMI. Depression and elevated nighttime HR, but not daytime HR, are independent predictors of survival in these patients. Although depressed patients have a higher nighttime HR than nondepressed patients, nighttime HR predicts mortality in both depressed and nondepressed patients.