Frequency and clinical correlates of bipolar features in acute coronary syndrome patients

Depression and acute coronary syndrome (ACS) are both extremely prevalent diseases. Studies aimed at evaluating whether depression is an independent risk factor for cardiac events provided no definitive results. In most of these studies, depression has been broadly defined with no differentiation between unipolar (MDD) versus bipolar forms (BD). The aim of this study was to evaluate the frequency of DSM-IV BD (bipolar I and bipolar II subtypes, cyclothymia), as well as temperamental or isolated bipolar features in a sample of 171 patients hospitalized for ACS. We also explored whether these psychopathological conditions were associated with some clinical characteristics of ACS.

Patients with ACS admitted to three neighboring Cardiac Intensive Care Units (CICUs) in a 12-month continuative period of time were eligible for inclusion if they met the criteria for either acute myocardial infarct with or without ST-segment elevation or unstable angina, verified by standard ACS criteria. All patients underwent standardized cardiological and psychopathological evaluations.

Of the 171 ACS patients enrolled, 37 patients (21.7%) were found to have a DSM-IV mood disorder. Of these, 20 (11.7%) had bipolar type I or type II or cyclothymia, while 17 (10%) were the cases of MDD. Rapid mood switches ranged from 11% of ACS patients with no mood disorders, to 47% of those with MDD to 55% of those with BD. Linear regression analysis showed that a diagnosis of BD (p=.023), but not that of MDD (p=.721), was associated with a significant younger age at the index episode of ACS. A history of previous coronary events was more frequent in ACS patients with BD than in those with MDD.

Our data indicate that bipolar features and diagnosis are frequent in ACS patients. Bipolar disorder has a negative impact on cardiac symptomatology. Further research in this area is warranted.