Disproportionally impaired microvascular structure in essential hypertension.

BACKGROUND: Increased microvascular resistance and small artery remodelling are key abnormalities in the pathophysiology of essential hypertension. We investigated the relation between the impairment of coronary and forearm minimum vascular resistances (C-Rmin and F-Rmin) and the degree of hypertension.
METHOD: Seventy-five never-treated essential hypertension patients with 24-h systolic blood pressure (BP) at least 130 mmHg or diastolic BP at least 80 mmHg were assigned into grade 1 (office BP 140/90-159/99 mmHg) and grade 2 (office BP 160/100-179/109 mmHg) hypertension and compared to normotensive controls (n = 25). The patients were (48 years, 60% men) without cardiovascular disease. C-Rmin and coronary flow reserve (CFR) were derived from flow measurements in the left anterior descending artery using transthoracic echocardiography. F-Rmin was measured using venous occlusion plethysmography. Resting systemic vascular resistance index (SVRI) was measured with a gas rebreathing technique.
RESULTS: Compared to normotensive controls: 24-h mean BP was raised 14% in grade 1 essential hypertension and 28% in grade 2 essential hypertension, whereas F-Rmin and C-Rmin were elevated by 58 and 87% in grade 1 essential hypertension and 72 and 125% in grade 2 essential hypertension. C-Rmin and F-Rmin were thus both increased more than expected from the BP level. SVRI and left-ventricular mass were increased proportionally to the BP. CFR was decreased by approximately 30% in both essential hypertension groups.
CONCLUSION: The results demonstrate excessive microvascular structural abnormalities in hypertension suggesting microvascular alterations occur early and not just as an adaptation to the BP level. Thus the level of BP elevation does not give an accurate indication of the microvascular involvement and impairment in essential hypertension.