POSTISCHEMIC BLOOD-FLOW RESPONSE IN HYPERCHOLESTEROLEMIC PATIENTS

We undertook this cross-sectional study to com pare the mechanical behavior and postischemic response of the radial artery of 15 newly diagnosed hypercholesterolemic patients with those of 15 age- and sex-matched normocholesterolemic control subjects and 21 hypercholesterolemic patients treated for 2 years with an 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor (simvastatin, 10 to 20 mg/d). At the time of the study total cholesterol levels were at 7.9+/-0.2, 4.9+/-0.2, and 6.0+/-0.3 mmol/L in the three groups, respectively (mean+/-SEM, P<.001). High-resolution, noninvasive echotracking for assessment of internal arterial diameter was combined with measurements of blood flow velocity by Doppler and blood pressure by photoplethysmography. Radial cross sectional compliance and distensibility were similar in all groups. Forearm blood flow and flow-mediated dilation were measured after a 5-minute upper arm occlusion. Flow was calculated from the vessel diameter and blood flow velocity recorded simultaneously at the same site. Flow-mediated dilation after ischemia was not significantly different among the three groups. However, forearm blood flow increase was markedly blunted (P<.01) in untreated hypercholesterolemic patients (211%) compared with the normocholesterolemic control subjects (411%) and treated patients (365%). These findings suggest that the distensibility of the radial artery, a muscular conduit vessel usually devoid of atherosclerotic lesions, and its flow-mediated dilation are preserved in hyper cholesterolemic patients. In contrast, forearm resistance vessels exhibit a markedly reduced postischemic blood flow response that may be restored by prolonged lipid-lowering intervention.