REDUCING PULSE PRESSURE IN HYPERTENSION MAY NORMALIZE SMALL ARTERY STRUCTURE

To investigate the relation between the small artery structure and different blood pressure parameters, spontaneously hypertensive rats were treated from 4 to 24 weeks of age (20 weeks in total) with five different antihypertensive therapies: two angiotensin converting enzyme inhibitors (perindopril and captopril), a calcium antagonist (isradipine), a beta-blocker (metoprolol), and a vasodilator (hydralazine). At 24 weeks of age, 24-hour blood pressure was measured, and two mesenteric resistance vessels were taken from each animal. Blood pressure was 227/135 mm Hg (systolic/diastolic) and 161/106 mm Hg in untreated hypertensive and normotensive control rats, respectively. Heart rates were 376 min-1 and 295 min-1 for the two strains. All treatments reduced all blood pressure parameters except for metoprolol, which did not reduce pulse pressure. In the small arteries, the media cross-sectional area was unaffected by the treatments. When a simple correlation analysis was made, pulse pressure was found to correlate more closely (r = 0.64, p < 0.001) to the resistance vessel media/lumen ratio than any of the other pressure parameters studied: systolic (r = 0.51, p = 0.011), mean (r = 0.41, p = 0.05), or diastolic (r = 0.28, p = 0.19). When an analysis of covariance was performed that included pulse pressure, mean blood pressure, and heart rate, which also correlated significantly to the media/lumen ratio, 81% of the variation in the media/lumen ratio could be accounted for by the variation in the three covariates (p < 10(-5)), pulse pressure being the major factor. In conclusion, it is indicated that a reduction in pulse pressure and heart rate during antihypertensive treatment may be important in preventing the development of abnormal small artery structure in hypertension.