H emodynamic Interventions and the Pressure-Diameter Loop of the Left Ventricle and the Proximal Aorta in the Conscious Dog

The dynamics of the left ventricle (LV) have been extensively investigated. However, most studies refer to steady state conditions. We addressed the beat-to-beat variations resulting from hemodynamic interventions analyzed in the chronically instrumented dog. This approach permits serial studies in the same subject under physiological conditions. In particular we investigated the end-systolic pressure-dimension relationship and characteristics of the proximal aorta. The findings obtained during basal conditions, exercise and pharmacologic intervention indicate that several universal regulatory mechanisms are involved, besides various phenomena that exhibit a substantial degree of variability.