Assessment of pulmonary artery stenosis using freehand "flock of birds" digital color three-dimensional echocardiographic reconstruction.

Pulmonary artery (PA) trunk or branch PA stenosis is commonly found in patients with congenital heart disease. The aim of the present study was to evaluate the freehand "Flock of Birds" color Doppler three-dimensional (3D) reconstruction on a modeled-segment imitating PA stenosis. First, a PA model was created from latex tubes to simulate the main PA and its main branches with baseline cross-sectional areas (CSA) of 0.7 cm2. A series of narrowed segments in the right and left PA were created. The cross-sections of the smallest area ranged from 0.13 to 0.59 cm2 and stenotic segmental length ranged from 0.17 to 1.80 cm. The dimensions of these elements mounted on to the model were verified by intravascular ultrasound (IVUS) imaging. Next, pulsatile flows at 60 beats/ min were generated through the system. A GE/VingMed System FiVe with magnetic locator system (Flock of Birds) on a 3.5 MHz transducer was used to acquire a freehand sweep for ECG gated 3D data acquisition of color Doppler flows through the model. The images were reconstructed by EchoPac 3D software and the morphology of the stenotic elements were determined. The results revealed that the narrowest CSA determined by the 3D color flow cast of the pulmonary artery were in excellent agreement with IVUS CSA (r = 0.98, p < 0.001, SEE = 0.04 cm2). The stenotic length estimated from 3D was also in good agreement with the IVUS (r = 0.98, p < 0.001, SEE = 0.03 cm). In addition, complex morphology of the stenosis was well visualized by this technique. As a result, the noninvasive free-hand digital color 3D echocardiography can be adopted for the accurate assessment of the severity and morphology of PA stenosis in patients with congenital heart diseases.