Microvascular perfusion during atrial pacing in renal hypertension induced cardiac hypertrophy

The purpose of this study was to determine if microvascular reserve was recruited during atrial pacing in the hypertrophied myocardium. Hypertrophy was induced by one-kidney, one-clip (1K1C) renal hypertension and compared to uninephrectomized control rabbits 30 days after surgery. Coronary flow was determined by radioactive microspheres. Microvascular perfusion was determined by comparison of fluorescein isothiocyanate-dextran labeled vessels with an alkaline phosphatase stain. Heart rates were not different between groups and all animals were paced 35% above baseline. Baseline coronary flow (176 +/- 44 and 207 +/- 61 ml/min/100 g, control and 1K1C animals) was not altered by pacing in either group. The baseline percent of capillaries perfused was not different between groups (56 +/- 2 and 61 +/- 3%, sham and 1K1C) and the percent perfused increased significantly during pacing for both the non-hypertrophied and 1K1C myocardium (76 +/- 6 and 78 +/- 10%). The baseline percent of the arteriolar bed perfused, was higher in the 1K1C (86 +/- 5%) compared to non-hypertrophied (63 +/- 6%) myocardium. During pacing, the percent of the arteriolar bed perfused increased in non-hypertrophied (89 +/- 14%) but not in the 1K1C myocardium. Although the percent of arterioles perfused did not increase with pacing in the 1K1C myocardium, the capillary reserve was recruited, facilitating the transport of O2 in both the hypertrophied and non-hypertrophied myocardium.