758-1 Vasodilator Capacity of Coronary Resistance Vessels is Maintained by Chronic Exercise Training During Development of Heart Failure in Awake Dogs

Previous studies have shown that coronary vasodilator capacity which reflects vasomotion of coronary resistance vessels is enhanced after chronic exercise (EX) training in normal dogs. The goal of this study was to determine whether EX would preserve coronary dilator capacity during development of heart failure. Dogs (n = 4) were chronically instrumented to measure systemic hemodynamics, coronary blood flow (CBF) and for chronic pacing. Dogs were cardiac paced for 4 weeks (210 b/min for 3 weeks and 240 b/min for the 4th week) and exercised on a treadmill 2 hours/day during this pacing period. The peak CBF responses following release of a brief coronary artery occlusion (Occ.) and to acetylcholine (Ach) were examined before and after this cardiac pacing and EX combined regimen. The results (Unit: ml/min) are as follows. Before pacing a ex After pacing a ex Baseline Res. Delta Baseline Res. Delta Occ. (s) 5s 19 ± 1 59 ± 5 40 ± 4 27 ± 2 66 ± 7 40 ± 5 10s 20 ± 1 6s ± 6 45 ± 5 27 ± 2 80 ± 5 53 ± 2 15s 20 ± 2 78 ± 7 57 ± 15 27 ± 3 69 ± 10 42 ± 8 20s 20 ± 1 78 ± 17 59 ± 16 27 ± 2 98 ± 8 70 ± 10 30s 21 ± 2 98 ± 16 77 ± 15 27 ± 3 105 ± 12 80 ± 14 Ach. (μg/kg) 0.25 22 ± 1 33 ± 3 11 ± 4 24 ± 5 41 ± 1 17 ± 5 0.5 21 ± 3 38 ± 4 17 ± 6 24 ± 4 41 ± 1 17 ± 5 1 21 ± 2 42 ± 1 25 ± 1 24 ± 2 50 ± 2 26 ± 1 5 22 ± 3 59 ± 3 37 ± 5 24 ± 2 56 ± 1 32 ± 2 20 22 ± 2 64 ± 6 43 ± 6 24 ± 2 53 ± 1 29 ± 2 * * p l 0.05 from before pacing and EX The peak CBF response to nitroglycerin (NTG) was not changed. In contrast, CBF responses responses to Occ, Ach and NTG were impaired in dogs with the same pacing regimen but without EX. Thus, EX might playa potential role to protect vasodilator capacity of coronary resistance vessels during development of heart failure.