Disparity between ratios of diameter and blood flows in central pulmonary arteries in postoperative congenital heart disease using MRI

Abstract

Purpose: To compare the relative severity of stenoses of right or left pulmonary arteries with differences in flow to each lung after repair of congenital heart disease (CHD). Materials and Methods: A total of 15 patients with post-operative congenital heart disease underwent MRI to evaluate branch pulmonary artery stenoses. Spin-echo images and MR angiography were used to assess morphology, and velocity-encoded cine (VEC) MRI was used to measure flow in the right and left pulmonary arteries. The ratios of the narrowest diameters of the right to left pulmonary arteries (R/L size) and right to left pulmonary arterial flow (R/L flow) were compared using Spearman's correlation. F test was used to assess the significance of the regression coefficients. Results: R/L size ratio varied from 0.50 to 2.66, while the R/L flow ratio varied from 0.36 to 12.02. There was an exponential relationship between R/L size and R/L flow, with r2 = 0.78 and P = 0.001. However, severity of morphologic stenoses was not clinically useful for predicting flow reduction. Prediction residuals ranged from -136% to 54% of the true R/L flow. Conclusion: Anatomical evaluation of the pulmonary arteries does not predict accurately differential blood flow in patients with pulmonary stenoses. Therefore, blood flow measurements are essential when considering the need for further surgical or interventional procedures. © 2007 Wiley-Liss, Inc.