PATHOPHYSIOLOGY AND NATURAL HISTORY COARCTATION REPAIR 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 < .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 gig/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 ,g/min forearm vascular resistance increased by 55% in the coarctation group, while the resistance in the control group increased by only 3%, p < .05). There was no difference between the two groups with regard to the dose-response curves for calf vascular resistance. These data suggest the presence in the resistance vessels anatomically positioned above the coarctation of abnormal vascular reactivity that may have persisted despite successful repair. Circulation 71, No. 3, 495-499, 1985. AFTER successful repair of coarctation of the aorta, a significant percentage of patients will have resting hypertension.'-3 Furthermore, many patients who have undergone successful repair of coarctation and are normotensive at rest will have a hypertensive response to exercise in their right arms and may develop a residual gradient across the coarctation.4 Previous investigations have suggested that abnormalities of the vascular bed anatomically positioned before the coarctation (precoarctation vascular bed) may play a role in this hypertension. We have previously reported abnormalities of baroreceptor function in such patients5 and Samanek et al.6 have shown differences in maximal muscle blood flow between the upper and lower extremities of patients after coarctectomy, suggesting From the Section of Pediatric Cardiology, C. S. Mott Children's Hospital, Department of Pediatrics and the Department of Biostatistics, University of Michigan Medical Center, Ann Arbor. Supported by NIH grant MO 1RR00042-21. Address for correspondence: Albert P. Rocchini, M.D., C. S. Mott Children's Hospital, University of Michigan Medical School, Box 66. Ann Arbor, MI 48109. Received Sept. 14, 1984; revision accepted Dec. 6, 1984. Vol. 71, No. 3, March 1985 differences in resistance vessels in the precoarctation and postcoarctation vascular beds (those positioned after the stricture). With the use of specimens obtained at coarctectomy, Sehested et al.7 have shown in vitro and with histologic evidence that the precoarctation vessel wall is more rigid than the postcoarctation vessel wall. Because of these findings, we hypothesized that the precoarctation vascular bed has abnormal vascular reactivity to adrenergic stimuli that persists after adequate repair of coarctation.7-9 To test our hypothesis, we assessed changes in both right forearm and calf vascular resistances in response to intra-arterial infusions of norepinephrine in patients who had undergone repair of coarctation and were mildly hypertensive and compared their responses with those of patients in a control group. Materials and methods Six patients who had undergone coarctectomy and were undergoing cardiac catheterization to assess9 the hemodynamic cause of their residual mild resting hypertension and severe 495 by gest on A ril 8, 2017 http://ciajournals.org/ D ow nladed from