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Permanent link (DOI): https://doi.org/10.7939/R32D0M

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Regulation of oxygen uptake and cardiac function in heart failure: effects of biventricular pacing and high-intensity interval exercise Open Access

Descriptions

Other title
Subject/Keyword
oxygen kinetics
cardiac magnetic resonance imaging
heart failure
cardiac resynchronization therapy
high-intensity interval exercise
contrast enhanced echocardiography
ventricular function
Type of item
Thesis
Degree grantor
University of Alberta
Author or creator
Tomczak, Corey
Supervisor and department
Haennel, Robert (Physical Therapy)
Examining committee member and department
Bhambhani, Yagesh (Occupational Therapy)
Thompson, Richard (Biomedical Engineering)
Goodman, Jack (Physical Education and Health)
Paterson, Ian (Cardiology)
Haykowsky, Mark (Physical Therapy)
Department
Faculty of Rehabilitation Medicine
Specialization

Date accepted
2011-11-03T21:13:21Z
Graduation date
2012-06
Degree
Doctor of Philosophy
Degree level
Doctoral
Abstract
Cardiac resynchronization therapy (CRT) and high-intensity interval training (HIT) have been shown to be effective for left ventricular (LV) reverse remodelling and increasing aerobic capacity in patients with heart failure (HF) and reduced ejection fraction (EF). The mechanisms underlying these benefits are not well understood. Accordingly, the purpose of the first study (Chapter 2) was to investigate the effects of CRT on oxygen uptake (VO2) kinetics and exercise LV function during the transition to moderate-intensity exercise. The first study showed that 1) CRT led to a significant speeding in VO2 kinetics, 2) stroke volume during steady-state exercise increased due to a decrease in submaximal exercise LV ESV independent of cardiac preload, and 3) CRT resulted in faster heart rate kinetics, suggesting that autonomic control of heart rate during exercise changed with CRT. The purpose of the second study (Chapter 3) was to examine the CRT mediated improvements in peak exercise LV function, peak VO2, and recovery from peak exercise. The second study showed that 1) CRT increased reserve and peak cardiac output, 2) CRT increased VO2 at peak exercise and this was related to an increase in cardiac output reserve that was secondary to an increase in LV end-systolic volume (ESV) reserve and preserved cardiac preload, 3) CRT decreased the time to exercise recovery as measured by a speeding in gas exchange and ventilation kinetics post-exercise, and 4) faster post-exercise VO2 kinetics were associated with greater aerobic capacity. The purpose of the third study (Chapter 4) was to assess biventricular function prior to, and immediately following acute HIT. The third study showed that biventricular ESV decreased and LV systolic annular velocity increased immediately following acute HIT. Within 30 min of exercise termination, LV EF was significantly increased compared to pre-exercise values. Diastolic function immediately following acute HIT was also preserved secondary to increased LV recoil. Collectively, the findings of these studies show that patients with HF and reduced EF are able to increase metabolic reserve (evidenced by a speeding in VO2 kinetics) following CRT, and that interventions such as CRT and HIT are effective in reducing (chronically and acutely) LV ESV during and following exercise.
Language
English
DOI
doi:10.7939/R32D0M
Rights
License granted by Corey Tomczak (corey.tomczak@ualberta.ca) on 2011-11-03T21:08:34Z (GMT): Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of the above terms. The author reserves all other publication and other rights in association with the copyright in the thesis, and except as herein provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
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