Intracardiac, intravascular, two-dimensional, high-frequency ultrasound imaging of pulmonary artery and its branches in humans and animals

Abstract

Intravascular ultrasound imaging is a promising new method for assessing vascular morphology. We evaluated the capability of intravascular ultrasound to quantify pulmonary artery (PA) morphology in vitro and explored the feasibility of in vivo PA imaging in animals and humans. In the in vitro study of 15 PA segments, we used a 20-MHz prototype ultrasound catheter. Intravascular ultrasound (y) provided crisp images of PA segments and demonstrated excellent correlations with anatomic measurements (x) in the estimation of luminal area (y=0.89x+2.95, r=0.99, p<0.001), luminal diameter (n=30, y=0.79x+0.96, r=0.92, p<0.001), and vessel wall thickness (n=60, y=0.65x+0.33, r=0.85, p<0.001). We subsequently introduced the probe into the PA of 10 dogs and were able to obtain real-time, two-dimensional images of the main PA, its major branches, and farther smaller branches as far as the wedge level. To evaluate the in vivo feasibility of PA imaging in conscious humans, we used a commercially available, 20-MHz intravascular ultrasound (IVUS) catheter in 22 subjects through a femoral or jugular venous sheath at the end of standard diagnostic cardiac catheterization. In 20 subjects, we acquired dynamic, high-resolution, cross-sectional images of the proximal and distal PA. Changes in shape and decreasing luminal area could be clearly recognized as the IVUS catheter reached branching points and as it passed more distally. There were no complications. We conclude that IVUS imaging can be safely performed in humans, that it provides dynamic, two-dimensional images of proximal and distal PAs, and that it has promise as a quantitative tool in studying pulmonary circulation.