Chronic physical training preserves coronary blood flow response to acute treadmill exercise in awake dogs with rapid cardiac pacing

Previous studies have shown that vasodilator response to exercise (EX) is reduced in heart failure (HF). The objective of this study was to determine whether coronary blood flow response to acute treadmill EX was modified by chronic physical training (PT) in dogs with rapid cardiac pacing. Dogs (n= 10) were chronically instrumented for measurement of left ventricular pressure, mean aortic pressure (MAP), coronary blood flow (CBF) and for cardiac pacing. Systemic hemodynamics and CBF during a four step treadmill EX (3, 6 and 9 km/h, S min at each speed) were examined before (control state) and after four weeks of cardiac pacing (210 b/min for 3 weeks and 240 b/min for the 4th week). CBF response to acute treadmill EX was significantly increased in control state. After 4 wks, in 4 of the dogs (Group I) that did not undergo PT there was a significant reduction in the CBF response to treadmill EX in comparison to control state; For the dogs (n=6, Group II) that underwent treadmill PT (4.4±1.2 km/h, 2 h/day) throughout the four wk pacing period, the response of CBF to acute EX was not different than in the control state. The results are summarized as the follows (*,p<0.05 vs resting value; +, p<o.05 vs control): Treadmill Speed: Resting 3 km/h 6 km/h 9 km/h Group I Control: CBF(ml/min) 29±4 48±11* 56±10* 63±11* 4 wks: CBF(ml/min) 34±8 36+7⁺ 39+8⁺ 41+8⁺ Group II Control:CBF(ml/min) 29±7 42±8* 47±11* 58±12* 4 wks: CBF(ml/min) 35±7 49±11* 55±13* 63±14* Thus, coronary vasodilator capacity is preserved by chronic PT in dogs during development of heart failure.