Pathophysiology of exercise intolerance in chronic diseases: the role of diminished cardiac performance in mitochondrial and heart failure patients

McCoy, J. et al. (2017) Pathophysiology of exercise intolerance in chronic diseases: the role of diminished cardiac performance in mitochondrial and heart failure patients. Open Heart, 4(2), e000632. (doi: 10.1136/openhrt-2017-000632) (PMID:28878952) (PMCID:PMC5574430)

Abstract

Objective: Exercise intolerance is a clinical hallmark of chronic conditions. The present study determined pathophysiological mechanisms of exercise intolerance in cardiovascular, neuromuscular, and metabolic disorders. Methods: In a prospective cross-sectional observational study 152 patients (heart failure reduced ejection fraction, n=32; stroke, n=34; mitochondrial disease, n=28; type two diabetes, n=28; and healthy controls, n=30) performed cardiopulmonary exercise testing with metabolic and haemodynamic measurements. Peak exercise O2 consumption and cardiac power output were measures of exercise tolerance and cardiac performance. Results: Exercise tolerance was significantly diminished in patients compared with controls (ie, by 45% stroke, 39% mitochondria disease, and 33% diabetes and heart failure, p<0.05). Cardiac performance was only significantly reduced in heart failure (due to reduced heart rate, stroke volume, and blood pressure) and mitochondrial patients (due reduced stroke volume) compared with controls (ie, by 53% and 26%, p<0.05). Ability of skeletal muscles to extract oxygen (ie, arterial-venous O2 difference) was diminished in mitochondrial, stroke, and diabetes patients (by 24%, 22%, and 18%, p<0.05), but increased by 21% in heart failure (p<0.05) compared with controls. Cardiac output explained 65% and 51% of the variance in peak O2 consumption (p<0.01) in heart failure and mitochondrial patients, whereas arterial-venous O2 difference explained 69% (p<0.01) of variance in peak O2 consumption in diabetes, and 65% and 48% in stroke and mitochondrial patients (p<0.01). Conclusions: Different mechanisms explain exercise intolerance in patients with heart failure, mitochondrial dysfunction, stroke and diabetes. Their better understanding may improve management of patients, their stress tolerance and quality of life.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Cleland, Professor John
• Authors: McCoy, J., Bates, M., Eggett, C., Siervo, M., Cassidy, S., Newman, J., Moore, S. A., Gorman, G., Trenell, M. I., Velicki, L., Seferovic, P. M., Cleland, J. G.F., MacGowan, G. A., Turnbull, D. M., and Jakovljevic, D. G.
• College/School: College of Medical Veterinary and Life Sciences > School of Health & Wellbeing > Robertson Centre
• Journal Name: Open Heart
• Publisher: BMJ Publishing Group
• ISSN: 2053-3624
• ISSN (Online): 2053-3624
• Published Online: 28 July 2017
• Copyright Holders: Copyright © 2017 The Authors
• First Published: First published in Open Heart 4(2):e000632
• Publisher Policy: Reproduced under a Creative Commons License