PERIPHERAL-BLOOD FLOW RESPONSES TO EXERCISE AFTER SUCCESSFUL CORRECTION OF COARCTATION OF THE AORTA

Objectives. The purpose of this study was to characterize peripheral f lea kinetics in response to progressive discontinuous maximal exercise in 10 patients who underwent repair of coarctation of the aorta and 1 1 age matched healthy adolescents. Background. An impairment of leg bl ood flow has been suggested on the basis of exaggerated femoral muscle lactate accumulation in patients with successful repair of coarctatio n. Few data are available describing blood flow kinetics of the exerci sing leg in such patients. Methods. Duplex ultrasound provided transcu taneous measurements of peak systolic and end-diastolic flow velocitie s of the femoral, humeral and renal arteries at rest and immediately a fter mild, moderate and maximal exercise intensities for computation o f mean velocity, resistance index and femoral blood flow. Results. Fem oral mean velocity and femoral blood how increased linearly with exerc ise intensity in both groups, but the slope of this increase was signi ficantly lower in patients. humeral mean velocity increased significan tly less in patients than in control subjects, Femoral resistance inde x sharply decreased from that at rest (patients [mean +/- SE] 1.4 +/- 0.04; control subjects 1.4 +/- 0.03) to mild exercise intensity in bot h groups (patients 0.69 +/- 0.03; control subjects 0.72 +/- 0.03). A f urther decrease was observed at maximal exercise in patients (0.60 +/- 0.04, p = 0.08) but not in control subjects (0.69 +/- 0.02). Conclusi ons. These observations suggest that despite a greater exercise induce d femoral vasodilation, patients with successful correction of coarcta tion of the aorta demonstrate an impaired lower limb blood flow in res ponse to strenuous dynamic exercise. In the absence of stenosis at res t, this alteration could result from exaggerated flow turbulence in th e descending aorta distal to the site of correction because of loss of elasticity at the site of the resection of the coarcted segment.