Biplane transoesophageal echocardiography, transthoracic Doppler, and magnetic resonance imaging in the assessment of coarctation of the aorta

This study compared flow-sensitive magnetic resonance imaging with biplane transoesophageal echocardiography in combination with continuous wave Doppler from the suprasternal notch in patients with native coarctation or after surgical repair. Twenty patients (mean age 33 years, range 17-60) were investigated, of whom 15 had undergone surgery at mean age 13 years, range 5-43. Peak and mean flow in the ascending and descending aorta as well as coarctation peak velocity were determined with the magnetic resonance imaging phase contrast technique. Coarctation peak velocity was also measured by Doppler from the jugulum. Magnetic resonance imaging axial sections as well as biplane transoesophageal echocardiography were used to measure the smallest diameter of the constricted segment. Sixteen healthy volunteers, mean age 36 years, range 22-63, provided reference values for magnetic resonance imaging determined volume of flow in the aorta. Peak flow in the descending aorta was 9.2 +/- 3.7 l. min-1 (reference 13.0 +/- 2.5, P < 0.01) and mean flow 3.1 +/- 0.9 l. min-1 (reference 3.4 +/- 0.8, P > 0.05). The ratio of descending-to-ascending peak flow was 0.54 +/- 0.17 (reference 0.69 +/- 0.10, P < 0.01) and mean flow 0.68 +/- 0.15 (reference 0.69 +/- 0.08, P > 0.05). The coarctation velocity was slightly higher with Doppler than with magnetic resonance imaging (+0.24 +/- 0.44 m. s-1, 95% confidence interval +0.45 to +0.02 m. s-1, P = 0.05). The coarctation diameter was slightly larger with magnetic resonance imaging than with transoesophageal echocardiography (1.4 +/- 3.5 mm, 95% confidence interval +3.1 to -0.3 mm, P = 0.11). Both methods are suitable for the assessment and follow-up of coarctation of the aorta. Flow assessment with magnetic resonance imaging provides a hitherto unavailable measure with which to assess the severity of obstruction.