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Figure 7 Flow Measurement in a Stenotic Left Anterior Descending Artery of a 71-Year-Old Woman
In the upper part of the screen, intracoronary pressures at steady-state hyperemia are shown: aortic pressure (Pa) = 101, distal pressure (Pd) = 70 and fractional flow reserve (FFR) = 0.69. 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. Thirty seconds later, the infusion of saline at room temperature is started with an infusion rate (Qi) of 15 ml/min. Consequently, distal blood temperature decreases and reaches a plateau at T = –0.90°C, which is recorded for another 30 s. Thereafter, the sensor is pulled back into the infusion catheter (*), where the temperature of the infused saline is measured as it enters the coronary artery: Ti = –4.5°C. The absolute blood flow in this coronary artery can now be calculated by: Qb = 15 x (–4.5/–0.90) x 1.08 = 81 ml/min.
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