Transvenous coronary ultrasound imaging. A novel approach to visualization of the coronary arteries.

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Abstract
BACKGROUND Catheter-based ultrasound is a new imaging modality to examine endovascular detail in the coronary circulation. This technique requires direct placement of the catheter in the arterial segment of interest. METHODS AND RESULTS We examined the feasibility of a less invasive approach by imaging the coronary arterial circulation by using a 5F (30 MHz) imaging catheter placed in the cardiac venous system. Using simultaneous fluoroscopy, we studied anesthetized closed-chest dogs (n = 6) and human subjects undergoing right heart catheterization (n = 11). After cannulation of the coronary sinus, the circumflex coronary artery (Cx) was visualized from the great cardiac vein (GCV), and on advancing the catheter into the anterior interventricular vein (AIV), the left anterior descending artery (LAD) was identified. Where artery and vein were parallel to each other, circular cross-sectional images of the coronary artery were obtained, whereas oblique and transverse orientation of artery to vein produced ellipsoid images or long-axis images. In the dogs, ultrasound-determined cross-sectional area of the coronary arteries (4.81 +/- 0.18 mm2) correlated closely with angiography (4.77 +/- 0.21 mm2) (r = 0.91, p less than 0.001). In humans, the Cx was readily visualized from the GCV in all subjects but because of anatomic variability, the LAD was seen less consistently from the AIV (73%). There was significant correlation between ultrasound-determined cross-sectional areas of the coronary arteries (8.25 +/- 0.34 mm2) with those from angiography (8.59 +/- 0.3 mm2) (r = 0.82, p = 0.001) in humans. In all subjects, the ultrasound transducer could be safely advanced into the AIV to the cardiac apex. Limitations of the technique include ultrasonic penetration problems, caused in part by the large size of human coronary veins and variability in artery-vein relations. CONCLUSIONS We conclude that transvenous imaging of coronary arteries with intravascular ultrasound is a less invasive, promising new approach to the study of structure and morphology in the coronary vasculature.