MR findings of collateral circulation are more accurate measures of hemodynamic significance than arm-leg blood pressure gradient after repair of coarctation of the aorta

Abstract

Purpose: To determine the relationship between percent stenosis and three indicators of hemodynamic significance - arm-leg blood pressure gradient, direct visualization of collaterals, and percent increase flow from proximal to distal descending thoracic aorta - in patients with prior repair of coarctation of the aorta (CoA). Materials and Methods: Magnetic resonance imaging (MRI) examinations of 19 patients with prior repair of CoA were retrospectively reviewed. Percent stenosis was compared to the arm-leg blood pressure gradient as obtained from chart review, the depiction of collaterals by gadolinium-enhanced magnetic resonance angiography (MRA), and the percent increased flow in the distal thoracic aorta as measured by velocity-encoded cine MRI. Some imaging series or blood-pressure values were not available in some patients. All of the data were available for 15 of the 19 patients. Results: The arm-leg blood pressure gradient showed no statistical association with percent stenosis (R2 = 0.10, P = 0.22), direct visualization of collaterals (P = 0.80), or percent increase in flow (R2 < 0.01, P = 0.85). Percent stenosis did show association with visualization of collaterals (P = 0.01) and increase flow (R2 = 0.62, P < 0.01). Conclusion: The arm-leg blood pressure gradient is not a reliable indicator of hemodynamic significance of restenosis in patients with prior repair of CoA. Direct visualization of collateral vessels by MRA and percent increase in flow from proximal to distal descending thoracic aorta are reliable indicators of hemodynamic significance.