Abstract 15642: Physical Activity is Associated with Increased Coronary Flow Reserve while Decreasing Resting Myocardial Blood Flow
Background. Physical activity reduces the risk for coronary heart disease (CHD), but to date the mechanisms remain unclear. One potential mechanism is by improving function of the coronary microvasculature, which can be measured by coronary flow reserve (CFR). The purpose of this study was to determine the relationship between physical activity and CFR, an early indicator of CHD risk.
Methods. We examined 416 male, middle-aged twins born between 1946 and 1956 from the Vietnam Era Twin Registry. Habitual physical activity was determined using the Baecke questionnaire, a 16-item instrument that assesses physical activity including sports, work, and leisure activity. Values for each form of physical activity were summed to obtain a total physical activity score in addition to the 3 subscores. CFR was calculated as the ratio of myocardial blood flow at rest and during stress, measured with positron emission tomography [N13] ammonia. Traditional risk factors for cardiovascular disease and presence of perfusion abnormalities were also assessed. Mixed effects regression was used for overall analysis and to separate between and within twin pair effects.
Results. In the overall sample, increasing levels of total physical activity (β=0.05, p=0.02) were associated with higher CFR; this effect was entirely due to sporting activity (β=0.14, p=0.001). The positive association between physical activity and CFR was due primarily to lower resting myocardial blood flow with increasing total physical activity (β=-1.19, p=0.003) and sporting activity (β=-3.06, p<0.001). The effects of sporting activity on CFR remained significant after accounting for CHD risk factors (β=0.09, p=0.04), perfusion abnormalities (β=0.15, p<0.001) and baseline heart rate (β=0.15, p<0.002). Results were similar within pairs, showing higher CFR (β=0.13, p=0.04) and lower resting MBF (β=-2.87, p=0.01) for increasing sporting activity. There was no interaction with zygosity.
Conclusions. Physical activity is associated with better microvascular function measured by CFR. This relationship is not confounded by familial factors. Although a cause and effect relationship cannot be proven, these data support a protective role of physical activity towards CHD risk.
- © 2011 by American Heart Association, Inc.