The diastolic flow velocity-pressure gradient relation and dp_v50to assess the hemodynamic significance of coronary stenoses

Abstract

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.

Collateral Donor Artery Physiology and the Influence of a Chronic Total Occlusion on Fractional Flow Reserve

“…27 Instantaneous pressures and flow velocities were extracted from the Study Manager program and Pa timings corrected to adjust for any time delay with respect to Pd. Instantaneous flow velocities from mid-diastole (after the diastolic upstroke in coronary flow velocity) to atrial activation (identified by the beginning of the p wave on ECG) were plotted against instantaneous pressure gradient (Pa-Pd).…”

Characteristics of the flow velocity-pressure gradient relation in the assessment of stenoses: an in vitro study

“…The dp v50 remained well below the established cut-off value (22.4 mmHg) to detect haemodynamic stenoses. 6 For intermediate stenoses (stenosis B), the dp v50 with one wire was below the cut-off value; the introduction of a second wire, however, resulted in a pathological dp v50 value. These findings are in agreement with a clinical study in intermediate stenoses that showed that the presence of two wires is associated with overestimation of the haemodynamic effect of a coronary stenosis severity and had a negative influence on decision making.…”

“…Both the hyperaemic stenosis resistance (HSR) and dp v50 , which is derived from the diastolic flow velocity-pressure gradient (v-dp) relation, have been found to determine the haemodynamic significance of a coronary stenosis with a high accuracy. [3][4][5][6] Patients frequently have multiple stenoses in the same coronary artery. Compared with a single stenosis, multiple consecutive stenoses result in a greater reduction in maximal flow.…”

Integration of Quantitative Positron Emission Tomography Absolute Myocardial Blood Flow Measurements in the Clinical Management of Coronary Artery Disease

“…59 More recently, efforts to assess maximal coronary vasodilator capacity and flow reserve as indicators of coronary stenosis severity and microvascular function have focused on coronary pressure-based measurements such as FFR, 60-66 index of microvascular resistance (requires coronary flow estimate, typically thermodilution mean transit time for the Ohm law model of resistance), 67 coronary diastolic wave free interval, 68 and a hybrid measurement of instantaneous middiastolic stenosis pressure gradients (dP) versus corresponding hyperemic coronary flow velocities (dP at 50 cm/s is optimal for diagnosis of hemodynamically significant stenosis). 69 The fact that FFR is an invasive measurement and that complete evaluation of the coronary circulation may require instrumentation of >1 and even all 3 major coronary vessels notwithstanding, the mean pressure ratio (distal to stenosis/ aorta) has gained wide acceptance as a decision-making tool for coronary revascularization because it is an excellent predictor of clinical outcomes. [63][64][65][66] However, FFR has its limitations, which include potential confounding factors such as hemodynamic conditions, 70,71 diffuse atherosclerosis, and microvascular dysfunction, any or all of which may affect the ratio importantly.…”