Aerobic exercise in coronary heart disease
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Physical inactivity is recognised as a risk factor for coronary heart disease (CHD). Healthy subjects who exercise have lower all-cause and CHD mortality compared to inactive. Also in subjects with already established CHD, being physically active seems to be associated with reduced mortality, but less data exist. Especially, the amount and intensity of exercise required for risk reduction in CHD patients is not yet fully resolved. With data from a population based prospective cohort study, the Nord-Trøndelag health study (HUNT-1), we investigated the association between physical activity and mortality in 2137 men and 1367 women with CHD. Compared to the reference category (no activity), one weekly exercise session was associated with reduced mortality in both genders. This inverse association became stronger with increasing exercise frequency and subjects reporting of moderate/high intensity exercise had a lower mortality risk than subjects reporting of low intensity exercise. As peak oxygen uptake (VO2peak) strongly predicts mortality in cardiac patients, it is warranted to find effective ways to increase aerobic fitness in CHD patients. We investigated the impact of exercise intensity for improvements in VO2peak in two clinical trials. Fifty-nine coronary artery bypass surgery (CABG) patients were randomised to either aerobic interval training (AIT) at 90% of maximum heart rate, or moderate continuous training (MCT) at 70% of maximum heart rate, five days/week, for four weeks at a rehabilitation centre. VO2peak increased significantly in both groups after the training period, with no difference between groups. After six months of home exercise, only the AIT group had a further increase in VO2peak. Eighty-nine myocardial infarction (MI) patients were randomised to treadmill AIT at 90% of maximum heart rate or to the group exercise programs provided by three Norwegian hospitals as usual care. VO2peak increased significantly more after treadmill AIT than after group exercise. Endothelial function, measured as flow-mediated dilatation, increased significantly in both groups. Health related quality of life increased significantly after exercise training in both CABG and MI patients. Being physically active was associated with reduced mortality in subjects with CHD. For CABG patients at a rehabilitation centre for four weeks, both AIT and MCT gave significant increase in VO2peak, while six months later only the AIT group had a further increase. We found larger increase in VO2peak after treadmill AIT than after the group exercise training provided as usual care to MI patients by three Norwegian hospitals.
PublisherNorges teknisk-naturvitenskapelige universitet, Det medisinske fakultet, Institutt for sirkulasjon og bildediagnostikk
SeriesDoktoravhandlinger ved NTNU, 1503-8181; 2010:25
Dissertations at the Faculty of Medicine, 0805-7680; 426