Novel monorail infusion catheter for volumetric coronary blood flow measurement in humans: in vitro validation

Aims: The aim of this study is to validate a novel monorail infusion catheter for thermodilution-based quantitative coronary flow measurements. Methods and results: Based on the principles of thermodilution, volumetric coronary flow can be determined from the flow rate of a continuous saline infusion, the temperature of saline when it enters the coronary artery, and the temperature of the blood mixed with the saline in the distal part of the coronary artery. In an in vitro set-up of the systemic and coronary circulation at body temperature, coronary flow values were varied from 50-300 ml/min in steps of 50 ml/min. At each coronary flow value, thermodilution-based measurements were performed at infusion rates of 15, 20, and 30 ml/min. Temperatures and pressures were simultaneously measured with a pressure/temperature sensor-tipped guidewire. Agreement of the calculated flow and the measured flow as well as repeatability were assessed. A total of five catheters were tested, with a total of 180 measurements. A strong correlation (p=0.976, p<0.0001) and a difference of 6.5 +/- 15.5 ml/min were found between measured and calculated flow. The difference between two repeated measures was 0.2%+/- 8.0%. Conclusions: This novel infusion catheter used in combination with a pressure/temperature sensor-tipped guidewire allows accurate and repeatable absolute coronary flow measurements. This opens a window to a better understanding of the coronary microcirculation.