Regadenoson Mycardial Contrast Echocardiography Perfusion Imaging for Detection of Allograft Coronary Vasculopathy

Abstract

<h3>Purpose</h3> Due to the often asymptomatic nature of cardiac allograft vasculopathy (CAV) serial surveillance is recommended for all cardiac transplant (OHT) recipients. Ideally, CAV surveillance should be non-invasive, not involve ionizing radiation, and discriminate diffuse CAV from focal obstructions. We hypothesized that vasodilator stress myocardial contrast echocardiography (MCE) perfusion imaging can non-invasively detect microvascular impact of diffuse or focal CAV. <h3>Methods</h3> The study was a retrospective, single center analysis of OHT recipients undergoing MCE between 1/20 and 10/20 (n=11). MCE at rest and after regadenoson was performed using a continuous infusion of lipid-shelled microbubbles. Images were analyzed by evaluating time-intensity after a destructive pulse sequence in all vascular territories. MCE data were correlated with wall motion assessment by conventional stress echocardiography and invasive coronary angiography (ICA). Grading of MCE as normal, mild, severe; and focal vs. diffuse was performed by one experienced reviewer in a blinded fashion. <h3>Results</h3> Mean age was 63 ± 3.3 years post OHT, at an average of 10.8 ± 3.3 years post OHT. Severe perfusion abnormalities during MCE were able to distinguish high grade CAV (2+) from low grade CAV (0-1) utilizing ICA as the gold standard. While stress echocardiographic wall motion assessment failed to indicate early CAV grade 1, abnormal MCE perfusion was found in 3 of 7 cases with angiographic CAV grade 1. <h3>Conclusion</h3> MCE is a practical, non-invasive perfusion imaging technique that may be useful for detecting significant CAV in OHT recipients. Perfusion deficits correlate with significant coronary artery stenosis identified by standard stress echocardiography and ICA, and may identify diffuse small vessel disease more effectively than current noninvasive techniques. Larger, prospective studies are needed to support this hypothesis and ultimately provide a rationale for routine use of MCE for CAV surveillance.