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Effect of short-term cardiovascular conditioning and low-fat diet on myocardial blood flow and flow reserve
J Czernin1, R J Barnard, K T Sun
1Department of Molecular and Medical Pharmacology, UCLA School of Medicine 90024-1721, USA.
Insights
Cardiovascular conditioning and a low-fat diet improve heart blood flow reserve by reducing resting blood flow and enhancing coronary vasodilation. This boosts exercise capacity and may benefit coronary artery disease patients.
Area of Science:
- Cardiology
- Exercise Physiology
- Nuclear Cardiology
Background:
- Cardiovascular conditioning lowers myocardial oxygen demand by reducing blood pressure and heart rate.
- Improved myocardial oxygen demand is expected to decrease resting myocardial blood flow and increase myocardial flow reserve.
- The impact of exercise and diet on myocardial blood flow and reserve in humans remains understudied.
Purpose of the Study:
- To investigate the effects of a 6-week cardiovascular conditioning and low-fat diet program on myocardial blood flow and myocardial flow reserve in humans.
- To assess changes in exercise capacity and serum lipid profiles.
- To compare findings with a control group not undergoing the program.
Main Methods:
- 13 volunteers underwent a 6-week program of cardiovascular conditioning and a low-fat diet.
- Myocardial blood flow at rest and during dipyridamole-induced hyperemia was measured using [13N]ammonia and positron emission tomography.
- Exercise capacity (METs) and serum lipid profiles were assessed before and after the program.
Main Results:
- The conditioning program significantly reduced resting rate-pressure product, cholesterol, LDL cholesterol, and triglycerides.
- Exercise tolerance (METs) improved significantly.
- Resting myocardial blood flow decreased, while hyperemic blood flow increased, leading to a significant improvement in myocardial flow reserve.
- No significant changes were observed in the control group.
Conclusions:
- Short-term cardiovascular conditioning combined with a low-fat diet enhances myocardial flow reserve.
- These improvements are linked to reduced resting blood flow and increased coronary vasodilatory capacity.
- The observed changes correlate with improved exercise capacity and suggest a potential protective role in coronary artery disease.
Background:
Cardiovascular conditioning reduces resting myocardial oxygen demand by lowering systolic blood pressure and heart rate. Lower myocardial oxygen demand at rest would be expected to be associated with a decrease in resting myocardial blood flow and, consequently, an increase in myocardial flow reserve as the ratio of hyperemic to resting blood flow. However, the effect of controlled exercise together with a low-lipid diet on myocardial blood flow and flow reserve has not been examined in humans.
Methods And Results:
Myocardial blood flow at rest and after dipyridamole-induced hyperemia (0.56 mg/kg i.v.) was quantified with [13N]ammonia and positron emission tomography in 13 volunteers before and upon completion of a 6-week program of cardiovascular conditioning and a low-fat diet. Exercise capacity and serum lipid profiles were also assessed at the start and finish of the program. Eight normal volunteers of similar age not participating in the conditioning program served as a control group. Cardiovascular conditioning lowered the resting rate-pressure product (8859 +/- 2128 versus 7450 +/- 1496, P < .001), serum cholesterol (217 +/- 36 versus 181 +/- 26 mg/dL), LDL cholesterol (140 +/- 32 versus 114 +/- 24 mg/dL), and triglycerides (145 +/- 53 versus 116 +/- 33 mg/dL, all P < .05). Exercise tolerance (metabolic equivalent of the task, METs) improved significantly from 10.0 +/- 3.0 to 14.4 +/- 3.6 (P < .01). Resting blood flow decreased (0.78 +/- 0.18 versus 0.69 +/- 0.14 mL.g-1.min-1, P < .05), whereas hyperemic blood flow increased (2.06 +/- 0.35 versus 2.25 +/- 0.40 mL.g-1.min-1, P < .05), resulting in an improved myocardial flow reserve (2.82 +/- 1.07 versus 3.39 +/- 0.91, P < .05). Overall, the myocardial flow reserve was significantly related to exercise performance (METs). In the control group, no changes in resting rate-pressure product, serum cholesterol levels, exercise performance, resting or hyperemic myocardial blood flow, or flow reserve were observed.
Conclusions:
Short-term cardiovascular conditioning together with a low-fat diet results in an improved myocardial flow reserve by lowering resting blood flow and increasing coronary vasodilatory capacity. These changes are associated with an improved exercise capacity and may offer a protective effect in patients with coronary artery disease.
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