Comparison of arterial hemodynamics in the mongrel dog and the racing greyhound

This study was undertaken to define certain differences in cardiovascular function between mongrel (M) and greyhound (GH) dogs. In unanesthetized, trained, chronically instrumented animals mean arterial pressure was significantly higher in the GH (118 vs. 98 mmHg). This was associated with a significantly higher cardiac index in the GH (4.3 vs 3.1 liters/min per m2) and a lower calculated peripheral resistance. Central venous renin activity was significantly lower in the GH when unanesthetized (1.51 vs. 2.88 ng/ml per h). Values of vascular impedance at several selected arterial sites were lower in the GH compared to the M, suggesting differences in arterial wall mechanical properties. The hydraulic power delivered to the aorta by the left ventricle in the GH was twice that of the M (1,166 vs. 564 mol wt). Oscillatory power represented a greater fraction of total aortic power in the GH (15.7 vs. 10.8%). Differences were also observed in the hemodynamic response to acute pentobarbital anesthesia. Thus the young adult GH is hemodynamically different from its mongrel counterpart. These differences bear some resemblance to hemodynamic changes seen in various types of experimental hypertension in animals and to those observed in the early phase of essential hypertension in man.