Percutaneous Intracoronary Ultrasound Imaging: Initial Applications in Patients

Abstract

This study was designed to evaluate the feasibility and potential clinical utility of intracoronary ultrasound imaging in patients using a 5.5 F synthetic aperture array, over-a-wire ultrasound catheter. Thirty patients underwent percutaneous intracoronary (n = 22) or peripheral (n = 8) ultrasound imaging at the time of cardiac catheterization. Ultrasound images were compared to simultaneous digital angiograms. Correlation between ultrasonic and angiographic estimation of coronary diameters was good (r = 0.80). Morphological analysis of ultrasound images obtained in patients revealed a pattern consistent with mild-to-minimal atherosclerosis, as defined by prior in vitro studies. In 15 patients, imaging was performed during intracoronary infusion of vasoactive medications (papaverine 15 mg, nitroglycerine 100 mugm, and acetylcholine 2 x 10 -5 or 2 x 10 -6M). These medications were also infused during continuous intracoronary Doppler catheter monitoring of velocity and pressure, thus allowing calculation of volume flow and coronary resistance indices. Serial determination of ultrasound-derived epicardial vessel cross-sectional area demonstrated no change (-1 +/- 1%) after papaverine, an 8 +/- 2% increase after nitroglycerine, and a 9 +/- 3% decrease after acetylcholine. Calculated resistance fell 53 +/- 4% after acetylcholine and 60 +/- 3% after papaverine. Preliminary in vitro studies using a combination angioplasty balloon/ultrasound catheter demonstrated the ability to visualize vessel dilation in real time. We conclude that intravascular ultrasound imaging will be useful for dimensional and morphological characterization of vascular disease, for beat-to-beat monitoring of vasomotion, and potentially as a real-time adjunct to therapeutic interventions.