Czernin J, Barnard R J, Sun K T, Krivokapich J, Nitzsche E, Dorsey D, Phelps M E, Schelbert H R
Department of Molecular and Medical Pharmacology, UCLA School of Medicine 90024-1721, USA.
Circulation. 1995 Jul 15;92(2):197-204. doi: 10.1161/01.cir.92.2.197.
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.
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.
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.
心血管调节通过降低收缩压和心率来减少静息心肌需氧量。静息时较低的心肌需氧量预计与静息心肌血流量的减少相关，因此，作为充血血流量与静息血流量之比的心肌血流储备会增加。然而，在人类中尚未研究有控制的运动与低脂饮食对心肌血流量和血流储备的影响。
在13名志愿者完成为期6周的心血管调节和低脂饮食计划之前及之后，用[13N]氨和正电子发射断层扫描对静息及双嘧达莫诱发充血（静脉注射0.56mg/kg）后的心肌血流量进行定量。在该计划开始和结束时还评估了运动能力和血清脂质谱。8名年龄相仿未参与调节计划的正常志愿者作为对照组。心血管调节降低了静息心率血压乘积（8859±2128对7450±1496，P<.001）、血清胆固醇（217±36对181±26mg/dL）、低密度脂蛋白胆固醇（140±32对114±24mg/dL）和甘油三酯（145±53对116±33mg/dL，均P<.05）。运动耐量（代谢当量，METs）从10.0±3.0显著提高到14.4±3.6（P<.01）。静息血流量减少（0.78±0.18对0.69±0.14mL·g-1·min-1，P<.05），而充血血流量增加（2.06±0.35对2.25±0.40mL·g-1·min-1，P<.05），导致心肌血流储备改善（2.82±1.07对3.39±0.91，P<.05）。总体而言，心肌血流储备与运动表现（METs）显著相关。在对照组中，未观察到静息心率血压乘积、血清胆固醇水平、运动表现、静息或充血心肌血流量或血流储备有变化。
短期心血管调节与低脂饮食相结合可通过降低静息血流量和增加冠状动脉舒张能力来改善心肌血流储备。这些变化与运动能力的改善相关，可能对冠心病患者提供保护作用。
