Abnormal endothelium-mediated regulation of coronary flow and arterioles in hypertension

In dogs with renovascular hypertension (2K2C, 4 weeks, n=6, H group) and controls (n=7, C group), the authors evaluated 1) coronary reserve by rapid pacing (200 bpm), and 2) effects of intracoronary acetylcholine (ACh) and papaverine on early diastolic inflow time (EDIT) which is the time for achieving 50% of diastolic myocardial inflow relative to diastolic time, and on diameters of subepicardial and subendocardial arterioles using a needle-probe CCD videomicroscope. In H group, coronary reserve was lower (P<.01), and diastolic myocardial inflow was delayed (P<.01) compared to C group. Arteriolar dilation by ACh in H group was diminished, compared to C group (P<.01), especially in subendocardium (P<.05 vs. subepicardium), while further prolonging EDIT in H group (P<.05). Papaverine dilated myocardial arterioles to a similar extent in both groups (P=NS) and improved EDIT in H group (P<.05). Thus, in hypertension, endothelium-dependent arteriolar dilation is diminished, especially in subendocardium, in association with diminished coronary reserve and delayed diastolic myocardial inflow