Color Doppler flow mapping in patients with coarctation of the aorta: New observations and improved evaluation with color flow diameter and proximal acceleration as predictors of severity

We performed color Doppler flow mapping in 15 patients, 1 week to 17 years old (mean 42 months), with coarctation of the aorta that was confirmed subsequently by angiography and/or surgery. Twelve patients had native coarctation and three had mild recoarctation after surgical repair. Color Doppler flow maps were analyzed with a digital analysis package and a Sony computer system. The diameter in the region of coarctation from the color Doppler flow map (mean = 2.0 ± 0.8 mm [SD]) correlated well with the coarctation diameter measured at angiography (mean = 1.8 ± 0.8 mm; r = .83, SEE 0.43 mm) in the 10 patients with native coarctation undergoing angiography, but the coarctation diameter measured by two-dimensional echocardiography (3.9 ± 1.5 mm) was poorly predictive of the angiographic severity (r = .23). Additionally, spatial acceleration was seen in all patients proximal to the coarctation site, with an aliased and accelerating stream narrowing progressively as it proceeded toward the coarctation site, a pattern that is not seen in healthy subjects. Computer analysis of the color Doppler images provided pseudo three-dimensional and digital velocity maps for blue, red, and green (turbulent) flow velocities to allow an enhanced appreciation of the accelerating stream, easily separating this from normal desending aortic aliasing patterns. The narrowing of the acceleration area in the proximal descending aorta (distal/proximal acceleration zone ratio) was also predictive of the angiographic severity of coarctation (r = .83). The distribution of low-level turbulence seen proximally paralleled the distribution of the proximal accelerating stream. Highly turbulent flow distal to the coarctation was identified in all patients, continuing into diastole in the seven patients with increased diastolic flow velocities on continuous-wave Doppler images. Color Doppler flow mapping allows new observations of coarctation flow diameter, spatial aortic acceleration, and turbulence in the proximal descending aorta that enhance the noninvasive assessment of patients with coarctation of the aorta.