Rationale and Objectives:

Depression increases risk of mortality among cardiac patients, which may be due to altered autonomic nervous system (ANS) functioning. The rate at which heart rate (HR) returns to baseline after treadmill stress testing predicts subsequent cardiac mortality. Because heart rate recovery (HRR) is controlled by the ANS, depression may predict HRR. Furthermore, exercise capacity may explain this relationship. This study examined the relationship between depression and HRR among cardiac rehabilitation patients, testing the hypothesis that exercise capacity would account for the relationship between depression and HRR.

Methodology:

The Beck Depression Inventory (BDI) was prospectively administered to 244 patients prior to beginning a phase II cardiac rehabilitation program. Participants also completed an exercise stress test yielding HRR and exercise capacity (METS).

Results:

Participants were 74% men averaging 66 years of age (Range 26-87). BDI score (Mdn = 5, range = 0-42) predicted HRR (Mdn = 26, Range = -8-80) such that patients with higher BDI scores had reduced HRR (r = -.14 P =.03). METS averaged 6.44 (range = 1-17.5) and higher BDI scores were associated with lower METS (r = -.19 P <.01). Higher METS predicted greater HRR (r =.52, P <.01). Controlling for METS eliminated the relationship between BDI scores and HRR (r = -.04, P =.44). BDI score, age, resting HR, maximum HR, and METS accounted for 63% of the variance in HRR.

Conclusion:

Higher levels of depressive symptoms predict poorer HRR, which appears to be partly accounted for by exercise capacity. Limitations include the cross-sectional design and small sample size. Although HRR is an imperfect measure of ANS control of HR, the relationship between depression and exercise capacity may help to explain the association of depression and ANS functioning.