MEDIA LUMEN RATIO IN HUMAN SMALL RESISTANCE ARTERIES IS RELATED TO FOREARM MINIMAL VASCULAR-RESISTANCE/

Background: For the evaluation in humans of structural alterations in resistance arteries, most studies have used an indirect index, the mea surement of minimal vascular resistance (mean blood pressure divided b y maximal postischaemic blood flow) in suitable vascular beds. A sensi tive and specific micromyographic technique was recently made availabl e for the study of human small resistance arteries. Whether a correlat ion really exists between results obtained with the two techniques has not yet been investigated. Objective: To evaluate both forearm minima l vascular resistance and media:lumen ratio of omental or subcutaneous small arteries in normotensive subjects and hypertensive patients. De sign and methods: Thirty-four individuals were included in the study ( age range 35-74 years; 24 hypertensive, 10 normotensive). Twenty-five had elective abdominal surgery and nine hypertensive patients had a gl uteal biopsy. Omental and subcutaneous small arteries were dissected a nd mounted on a wire micromyograph (Mulvany's technique), and media:lu men ratio and media thickness were measured. The dose-response curve t o noradrenaline was constructed at cumulative concentrations from 3 x 10(-9) to 3 x 10(-5) mol/l. Venous occlusion plethysmography was used to measure blood flow in the forearm, and minimal vascular resistance was calculated from mean blood pressure and postischaemic maximal bloo d flow (13 min ischaemia plus exercise). Results: A statistically sign ificant correlation was found between media:lumen ratio and minimal va scular resistance (r = 0.74, P < 0.001) as well as between media: lume n ratio and systolic (r = 0.44, P < 0.01 ) and diastolic (r = 0.38, P < 0.05) blood pressures. Similar correlations were observed between me dia thickness and systolic and diastolic blood pressures. Smalt arteri es from hypertensive patients had a significantly increased reactivity to noradrenaline (by analysis of variance) compared with those from n ormotensive subjects, in terms of wall tension but not of active media stress. Conclusions: The present study demonstrated that the media:lu men ratio of small resistance vessels is significantly related to fore arm minimal vascular resistance, suggesting that direct and indirect e valuations of vascular morphology will give similar results.