The Relationship Between Cardiorespiratory Fitness, Autonomic Nervous System And Cognition In Coronary Artery Disease Patients

INTRODUCTION: Coronary artery disease (CAD) is associated with low cardiorespiratory fitness, cognitive impairment and altered autonomic nervous system (ANS) function. The relationship between VO2max, cognition and the ANS remains poorly studied in people with CAD. PURPOSE: We investigated cognitive performances and cardiac autonomic measures in CAD patients with low, middle and high VO2max. We hypothesize that compared to lower fit CAD patients, higher fit patients will show better ANS adaptation to orthostatic stress, and that ANS response (ΔLF/HF ratio) would correlate with better cognition. METHODS: 47 individuals with CAD performed a cardiopulmonary exercise test and neuropsychological tests (MOCA, working memory, processing speed, executive functions). Responses to orthostatic stress were analyzed with heart rate variability (5 min in a supine position followed by 5 min in a standing position). Participants were divided into tertiles based on their VO2max. RESULTS: mean VO2max was 17.6 ± 1.9 vs 22.2 ± 1.8 vs 29.2 ± 4.2 mL.kg.min respectively for lower fit, medium fit and higher fit CAD patients (p < 0.001). Responses to orthostatic stress were significantly lower in lower fit compared to medium and higher fit patients for ΔLF/HF ratio (0.02 ± 1.7 vs 1.8 ± 2.9 vs 2.5 ± 3.1; p = 0.035), ΔLFn.u. (-3.4 ± 18.2 vs 16.1 ± 22.6 vs 19.9 ± 21.1; p = 0.006), ΔHFn.u. (1.76 ± 21.5 vs -18.3 ± 25.2 vs -22.3 ± 22.2; p = 0.013) and ΔParasympathetic Nervous System index (-0.75 ± 0.50 vs -1.17 ± 0.60 vs -1.10 ± 0.52; p = 0.044). Cognitive parameters were not statistically different between groups. After normalization for age, sex, and weight, patients with a VO2max ≤90% predicted values had significantly lower scores on the MOCA and verbal memory compared to those with a VO2max >90% predicted values: 25.8 ± 2.0 vs 27.5 ± 1.8 p = 0.004 and -0.27 ± 0.8 vs 0.21 ± 0.99 p = 0.048, respectively for MOCA and verbal memory. Only the Baevsky’s stress index measured in supine position was negatively correlated with verbal memory (R = -0.32, p = 0.036). CONCLUSION: In patients with CAD, lower VO2max is associated with altered autonomic responses to orthostatic stress. Lower fit patients have lower cognitive scores for MOCA and verbal memory, compared to higher fit patients. This underscores the potential impact of fitness levels on ANS and cognitive functions in CAD. Mirella and Lino Saputo Research Chair in Cardiovascular Diseases and the Prevention of Cognitive Decline from Université de Montréal at the Montreal Heart Institute. FB is financially supported by a fellowship from the Fonds de Recherche du Québec – Santé (FRQ-S).