P1529Poor mental health is accompanied by reduced autonomic functioning in the month following acute coronary syndrome

Abstract

Background: Depression, anxiety, neuroticism and phobia are all risk factors for cardiac morbidity and mortality following Acute Coronary Syndrome (ACS). Yet to date, there is no evidence that treating clinically meaningful mental health symptoms after ACS ameliorates these risks. Understanding the key patho-physiologic drivers of poor mental health post-ACS could provide critical insights that guide treatment options. Autonomic nervous system dysfunction is a leading candidate mechanism thought to account for a substantial part of the risk associated with depression in patients with stable coronary disease. Low heart rate variability (HRV) reflects excessive sympathetic or inadequate parasympathetic modulation of heart rate, thus elevating mortality risk after ACS. As depression commonly coexists with other mental health symptoms like anxiety, neuroticism and phobia, it is plausible that specific combinations of symptoms are accompanied by unique pathophysiology that leads to increased morbidity and mortality risk after ACS. Purpose(s): To assess whether mental health clusters yield distinct autonomic dysfunction profiles after ACS. Method(s): The ADVENT study followed 416 ACS patients admitted to one of the largest cardiology hospitals in Australia. Over 12 months mental health and autonomic functioning data were collected at 2 timepoints. Mental health clusters were derived from 4 inventories (Beck Depression Inventory, State-Trait Anxiety Inventory-Trait Version, Crown Crisp Index of Phobic Anxiety, Penn State Worry Questionnaire) and analysed using latent class analysis (LCA). HRV was collected via a 20 minute Electrocardiograph with AD Instruments software for continuous beat-to-beat heart rate recording with detection of R waves at frequency of 1000Hz. Data were converted to R-R intervals for time domain measurement and power spectrum analysis. Result(s): The predominantly male (79.0%) sample comprised participants with a mean (SD) age 58.4 (10.7) years. The 4 mental health clusters recovered in LCA were characterized by distinct R-R intervals: 1) Asymptomatic: 1017.5 ms (95% CIs: 983.5,1051.5) (47%); 2) Elevated worry and trait anxiety only: 1025.5 ms (95% CIs: 976.1, 1074.7) (29%); 3) Moderate depression and anxiety only: 1036.7 ms (95% CIs: 1006.2, 1067.1) (13%); 4) High on most/all dimensions: 855.28 ms (95% CIs: 800.2, 910.3) (5%). Between group differences in Low Frequency Power (normalized units; nu) were also observed: 47.4 nu (95% CIs: 43.3, 51.6), 48.5 nu (95% CIs: 41.9, 55.2), 47.9 nu (95% CIs: 44.6, 51.3), and 62.9 nu (95% CIs: 55.1,70.7), respectively. Multivariate analysis of variance revealed these to be statistically significant at 1 month [average R-R intervals F(3,346)=6.33) (p<0.00); LF Power F(3,346)=2.96) (p=0.03)] but not 12 months. Conclusion(s): High levels of depressive, anxious, neurotic and phobic symptoms that are characterized by reduced vagal activity and high sympathetic function cluster in the weeks following ACS.