Abstract 10644: Impact of Cardiopulmonary Bypass Surgery on Myocardial Perfusion Assessed by Ultrafast Power Doppler: A Human Proof-of-Concept Study

Abstract

Introduction: Inadequate myocardial coronary perfusion is a major cause of cardiac dysfunction in several clinical settings including congenital heart disease and cardiopulmonary bypass surgery (CPB). Blood flow to the myocardium (i.e. coronary perfusion) is primarily controlled by the coronary microvasculature (vessels < 500 μm) which plays a key part in coronary perfusion autoregulation. Until recently, direct quantitative coronary perfusion assessment had been infeasible due to limitations in spatial and/or temporal resolution of clinical imaging modalities. The study objective is to assess if ultrafast ultrasound-mediated power Doppler (PD) can approximate changes in myocardial perfusion in humans. Methods: We used a 6.9 MHz linear array probe connected to a programmable ultrafast ultrasound scanner (Verasonics Vantage®). We included 7 neonates with transposition of the great arteries (TGA) and acquired epicardial ultrafast acquisitions immediately before and after CPB (arterial switch operation) via open chest. The acquisitions were acquired at 2000 fps (PRF=10000Hz, 5 sources). Tissue clutter was separated from coronary signals with a sliding spatiotemporal filter. PD was measured as a representative of blood volume that scales with hematocrit. Fractional moving blood volume (FMBV) was calculated to normalize the PD signal: mean PD divided by the PD of the ventricular blood pool, a region with 100% vascular amplitude. Results and Conclusions: The FMBV post-operatively increased by a factor of two compared to pre-operative assessment, a reflection of hyperemia. These values returned to baseline on repeat assessment prior to discharge. Our findings suggest that ultrafast PD is a reliable tool in approximating changes in myocardial perfusion in the operating room and beyond. Thus, ultrafast power Doppler can be utilized to quantitatively assess the impact of CPB on coronary perfusion in humans.