265 The Timing of Arrhythmia Post-STEMI: A Retrospective Audit

Abstract

Background: Beta-blockers are widely used post-acute coronary syndrome (ACS). However, beta-blockade has historically been linked to side effects such as depression. Beta-blockers have a pharmacological effect on the autonomic nervous system (ANS) and ANS function has been linked to mood changes. We sought to investigate the possible association between beta-blockade and mood in post-ACS patients and examine whether it is explained by ANS function, as measured by heart rate variability (HRV). Methods: Patients recruited post-ACS had their mood indexed using the Cardiac Depression Scale (CDS) 4 weeks post ACS. A 20-minute ECG trace was analysed for HRV in AD Instruments Labchart 8. Following the exclusion of patients with missing baseline data (n=162), the final sample comprised 252 patients (n=206 males, mean age 59.14610.19). Results: 59.9% (n=151) of patients were taking betablockers, 78.8% on metoprolol. The relationship between beta-blocker use and CDS total score was significant (r=-0.124, p,0.05) but weak, indicating that patients taking a beta-blocker had lower CDS scores. A significant inverse relationship between beta-blockade and the CDS mood component was found (r=-0.131, p,0.05). Split by the presence of 'probable depression', logistic regression analysis showed that the relationship between beta-blockade and depression was fully mediated by increased Average RR (p,0.05). Conclusion: Beta-blockade in post-ACS patients has an inverse association with depressive symptoms and this relationship is mediated by reduced heart rate, suggesting a possible mechanism of action.