Quantification of morphologic and hemodynamic severity of coarctation of the aorta by magnetic resonance imaging

Objective: As the morpholgic severity of coarctation of the aorta is diffic ult to assess, especially after previous repair, the value of the technique of multiplanar reconstruction of magnetic resonance imaging data to achiev e a 3-dimensional reconstruction of the aortic arch was evaluated and compa red to hemodynamic measurements. Methods and Results: We performed 30 exami nations in 27 patients aged from 6 to 54 years, with a mean of 21 years, by magnetic resonance imaging using a 1.5 Tesla scanner with a standard body coil. Measurements of flow across the coarctation were performed using phas e shift velocity mapping, and peak velocity was calculated at the site of s tenosis. Aortic cross-sectional area before, at, and beyond the stenosis wa s reconstructed 3-dimensionally to calculate a percentage degree of stenosi s. Morphologic severity of stenosis was correlated to invasively assessed h emodynamic gradients and morphologic data from biplane angiography in 23 pa tients. Among the 30 examinations, 24 patients had been previously treated by either surgery, in 17 patients, or balloon dilation, while 6 had native coarctation. 3-dimensional reconstruction was possible in all and better de lineated the anatomy concerning the hemodynamic relevance of stenoses even as compared with biplane angiography. The correlation between severity of n arrowing assessed by diameter measurements in the biplane angiography and 2 -dimensional magnetic resonance imaging was r = 0.94, and multiplanar refor mation with 2-dimensional magnetic resonance imaging was r = 0.87 with a te ndency of higher grading with the 3-dimensional technique (p = 0.0001). The correlation of 2-dimensional magnetic resonance imaging with invasively me asured hemodynamic gradients was r = 0.67 versus r = 0.74 for the areas ass essed by multiplanar reformation, indicating that the hemodynamic relevance of a morphological approach to evaluate the degree of a stenosis should be tter be assessed 3-dimensionally. Conclusions: The 3-dimensional reconstruc tion of the morphologic severity of coarctation offers additonal informatio n over conventional imaging especially in patients with kinking, complex ge ometry, or collaterals, in whom hemodynamic measurements can become unrelia ble.