The diastolic flow velocity-pressure gradient relation and dp v50 to assess the hemodynamic significance of coronary stenoses

To evaluate the hemodynamic impact of coronary stenoses, the fractional (FFR) or coronary flow velocity reserve (CFVR) usually is measured. The combined measurement of instantaneous flow velocity and pressure gradient (v-dp relation) is rarely used in humans. We derived from the v-dp relation a new index, dp v50 (pressure gradient at flow velocity of 50 cm/s), and compared the diagnostic performance of dp v50 , CFVR, and FFR. Before coronary angiography was performed, patients underwent noninvasive stress testing. In all coronary vessels with an intermediate or severe stenosis, the flow velocity, aortic, and distal coronary pressure were measured simultaneously with a Doppler and pressure guidewire after induction of hyperemia. After regression analysis of all middiastolic flow velocity and pressure gradient data, the dp v50 was calculated. With the use of the results of noninvasive stress testing, the dp v50 cutoff value was established at 22.4 mmHg. In 77 patients, 124 coronary vessels with a mean 39% (SD 19) diameter stenosis were analyzed. In 43 stenoses, ischemia was detected. We found a sensitivity, specificity, and accuracy of 56%, 86%, and 76% for CFVR; 77%, 99%, and 91% for FFR; and 95%, 95%, and 95% for dp v50 . To establish that dp v50 is not dependent on maximal hyperemia, dp v50 was recalculated after omission of the highest quartile of flow velocity data, showing a difference of 3%. We found that dp v50 provided the highest sensitivity and accuracy compared with FFR and CFVR in the assessment of coronary stenoses. In contrast to CFVR and FFR, assessment of dp v50 is not dependent on maximal hyperemia.