Increased forearm vascular reactivity in patients with hypertension after repair of coarctation

To determine whether altered vascular reactivity could contribute to hypertension after repair of coarctation, the change in forearm and calf vascular resistances to small intra-arterial infusions of norepinephrine were measured in six patients who had undergone surgical correction of coarctation of the aorta but still had upper extremity hypertension and compared with similar measurements made in five normotensive patients with mild heart disease. Only the mean upper extremity pressure was significantly greater in the group that underwent repair of coarctation (102 +/- 11 vs 83 +/- 5 mm Hg, p less than .05, for mean arm pressures and 96 +/- 13 vs 83 +/- 7 mm Hg for mean leg pressures in patients who had coarctation vs normotensive patients, respectively). Forearm and calf blood flows were measured in the right arm and leg with a mercury-in-plastic strain-gauge plethysmograph. Forearm and calf vascular resistances were calculated by dividing mean arterial pressure of the appropriate extremity by the blood flow of that extremity. Norepinephrine was infused into the right brachial and femoral arteries of the patients at doses of 0.02, 0.05, 0.1, 0.2, 0.3, 0.5, and 0.7 microgram/min. Resting forearm and calf vascular resistances were similar in both groups of patients. The norepinephrine dose-response curves showed that control patients required more than three times the norepinephrine to produce the same percent increase in forearm vascular resistance (after 0.2 microgram/min forearm vascular resistance increased by 55% in the coarctation group, while the resistance in the control group increased by only 3%, p less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)