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

Jodi McCoy, Matthew Bates, Christopher Eggett, Mario Siervo, Sophie Cassidy, Jane Newman, Sarah A. Moore, Grainne Gorman, Michael I. Trenell, Lazar Velicki, Petar M. Seferovic, John G.F. Cleland, Guy A. MacGowan, Doug M. Turnbull, Djordje G. Jakovljevic*

*Corresponding author for this work

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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.

Original languageEnglish
Article numbere000632
Pages (from-to)1-8
Number of pages8
JournalOpen Heart
Volume4
Issue number2
Early online date28 Jul 2017
DOIs
Publication statusPublished - Jul 2017
Externally publishedYes

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