Absolute coronary blood flow and microvascular resistance: Correlation with instrumen tedcoronary artery blood flow ring measurements and coronary histology analysis in swine

Abstract

Measurement of absolute coronary blood flow (ABF) and microvascular resistance, assessed by coronary thermodilution using a dedicated infusion catheter (RayFlow, HexaCath, Paris, France) is available in clinical practice. We sought to compare ABF and resistances values obtained at different infusion rates, to coronary artery blood flow ring measurements and histological analysis of the infused vessel in animals. Domestic swine were instrumented with coronary artery blood flow (CBF) rings on the left anterior descending (LAD) and circumflex (LCx) coronary arteries. We performed ABF using saline infusion at flow rates of 5, 10, 15 and 20 mL/min. After measurement, histological analysis of the infused vessel was performed, at the level of the infusion and at least 60 mm distal to the infusion area (control). In 13 swines, we compared 72 pairs of measurements in the LAD and the LCx. The correlation between ABF and CBF at flow rates of 5 and 10 mL/min and 15 and 20 mL/min were respectively R = 0.67 (0.45–0.82) ( n = 40 pairs) and R = 0.84 (0.69–0.92) ( n = 32 pairs). The correlation between resistances assessed with ABF and CBF at flow rates of 5 and 10 mL/min and 15 and 20 mL/min were respectively R = 0.63 (0.34–0.80) ( n = 40 pairs) and R = 0.76 (0.56–0.88) ( n = 32 pairs). Histological analysis was performed in 14 coronary arteries (28 samples), and showed no coronary dissections after ABF measurement. Some endothelial injury was observed in both infusion and control samples: 62 ± 39% and 53 ± 38% ( P = 0.53), respectively. Endothelial injury in the control sample parts might be due to trauma caused by the pressure wire ( Fig. 1 ). ABF and microvascular resistance correlate well with CBF in animals at flow rates ≥ 15 mL/min. Measurement using coronary thermodilution with Rayflow infusion catheter is accurate in vivo and, in clinical practice, at flow rates of 15 to 20 mL/min, induce maximal hyperemia and may be as safe as FFR measurement.