Effects of Experimentally Produced Heart Failure on the Peripheral Vascular Response to Severe Exercise in Conscious Dogs

Abstract

The peripheral vascular response to severe exercise in eight dogs with heart failure produced by tricuspid avulsion and progressive pulmonary stenosis was compared to the response determined in eight control dogs. After full recovery from implantation of Doppler flow probes and miniature pressure gauges, measurements of arterial blood pressure and blood flow were telemetered from untethered dogs running behind a mobile recording vehicle at speeds of 10-25 mph over distances averaging 1 mile. Severe exercise in control dogs increased heart rate from 78 to 281 beats/min and mean arterial blood pressure from 93 to 134 mm Hg. Iliac blood flow rose from 151 to 897 ml/min, but mesenteric and renal blood flows did not change significantly. Iliac vascular resistance decreased from 0.64 to 0.15 mm Hg/ml min ^-1 , but mesenteric vascular resistance increased from 0.31 to 0.47 mm Hg/ml min ^-1 and renal vascular resistance increased from 0.49 to 0.75 mm Hg/ml min ^-1 . Severe exercise in dogs with heart failure increased heart rate from 102 to 274 beats/min, but mean arterial blood pressure only increased from 100 to 107 mm Hg. Iliac blood flow rose from 96 to 360 ml/min, whereas mesenteric blood flow decreased from 237 to 89 ml/min and renal blood flow decreased from 226 to 79 ml/min. Iliac vascular resistance decreased from 1.09 to 0.34 mm Hg/ml min ^-1 , but mesenteric vascular resistance increased from 0.49 to 1.31 mm Hg/ml min ^-1 and renal vascular resistance increased from 0.47 to 1.81 mm Hg/ml min ^-1 . Thus, in heart failure a distinctly abnormal peripheral vascular response to severe exercise occurs, characterized by a very small elevation in mean arterial blood pressure and intense visceral vasoconstriction resulting in diversion of visceral blood flows.