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Figure 6 Flow Measurement in the Right Coronary Artery of the Patient in Figure 5 as Displayed on the Analyzer
In the upper part of the screen, aortic and intracoronary pressures at steady-state hyperemia are shown: aortic pressure (Pa) = 68 mm Hg, distal pressure (Pd) = 59 mm Hg, and fractional flow reserve (FFR) = 0.86. The blue curve in the lower part of the screen shows intracoronary temperature. On the left side of the lower panel, blood temperature (Tb) is set to 0 when steady-state hyperemia is achieved. Approximately 30 s later, the infusion of saline at room temperature is started with an infusion rate (Qi) of 25 ml/min. Consequently, distal blood temperature decreases and quickly reaches a plateau at T = –0.97°C. Steady-state distal temperature (T) is recorded for another 30 s, after which the sensor is pulled back into the infusion catheter (*) to measure the temperature of the infused saline as it enters the coronary artery at the tip of the infusion catheter: Ti = –7.1°C. The absolute blood flow in this coronary artery can now easily be calculated by: Qb = 25 x (–7.1/–0.97) x 1.08 = 198 ml/min.