Physiologic and Behavioral Mechanisms Linking Depression with Increased Morbidity and Mortality in Heart Failure

A major concern of acute and critical care nurses is improving outcomes in patients with heart failure (HF). Despite advances in treatment of HF, rehospitalization rates and mortality remain high. Recently, depression has been identified as an independent risk factor for poor outcomes, particularly rehospitalization and mortality. Before appropriate interventions for depression in HF can be designed, it is imperative that we understand the mechanisms whereby depression results in poor outcomes. Few investigators have examined these mechanisms, but two explanations have been proposed. Physiologically, depression might contribute to poorer outcomes by increasing sympathetic nervous system (SNS) activation. Behaviorally, depression might con~ribute to poorer outcomes by reducing adherence to the prescribed treatment regimen. The purpose of this study is to explore these mechanisms for the known association between depression, and increased morbidity and mortality. The specific aim of this study is to determine whether SNS arousal and nonadherence mediate the association between depression and poorer HF outcomes. This aim will be examined in a longitudinal correlational study. Three hundred patients with a confirmed diagnosis of HF will be followed. At baseline, depression (assessed by the Beck Depression Inventory), SNS arousal (assessed by heart rate variability), and adherence (assessed by both self-report [Medical Outcomes Study Specific Adherence Scale] and objective evidence [24-hour urine sodium and .electronic medication monitoring device] of adherence) will be measured. Six months later, the combined end-point of HF rehospitalization or cardiac mortality will be determined. Data will be analyzed using regression techniques to determine whether SNS arousal, adherence or both mediate the relationship between depression and HF outcomes. Results of this study will provide vital information about mechanisms linking depression and poor outcomes that clinicians and researchers can use in the design of effective interventions.