Determination of the Optimal Measurement Point for Fractional Flow Reserve Derived From CTA Using Pressure Wire Assessment as Reference.

For clinical decision making, it was recently recommended that values of fractional flow reserve (FFR) derived from coronary CTA (FFR) be measured 1-2 cm distal to the stenosis, given the potential for overestimation of ischemia when FFR values at far distal segments are used. Supporting data are, however, lacking. The purpose of the present study was to evaluate the diagnostic performance of FFR values measured 1-2 cm distal to the stenosis and at more distal locations relative to invasive FFR values. FFR and invasive FFR values for 365 vessels in 253 patients identified from the Assessing Diagnostic Value of Noninvasive FFR in Coronary Care (ADVANCE) registry were prospectively assessed. FFR values were measured 1-2 cm distal to the stenosis and at the pressure wire position and far distal segments. The diagnostic accuracy of FFR was assessed on the basis of the ROC AUC. The AUC of FFR was calculated using FFR as an explanatory variable and an invasive FFR of 0.80 or less as the dichotomous dependent variable. The AUC of FFR values measured 1-2 cm distal to the stenosis (0.85; 95% CI, 0.80-0.88) was higher ( = .002) than that of FFR values measured at far distal segments (0.80; 95% CI, 0.76-0.84) and similar ( = .16) to that of FFR values measured at the pressure wire position (0.86; 95% CI, 0.81-0.89). FFR values measured 1-2 cm distal to the stenosis and at far distal segments had sensitivity of 87% versus 92% ( = .003), specificity of 73% versus 42% ( < .001), PPV of 75% versus 59% ( < .001), and NPV of 86% versus 85% ( = .72), respectively. Subgroup analyses of lesions of the left anterior descending coronary artery, left circumflex coronary artery, and right coronary artery all showed improved specificity and PPV (all < .005) for FFR values measured 1-2 cm distal to the stenosis compared with values measured at the pressure wire position. However, the AUC was higher for measurements obtained 1-2 cm distal to the stenosis versus those obtained at far distal segments, for left anterior descending coronary artery lesions ( < .001) but not for left circumflex coronary artery lesions ( = .27) or right coronary artery lesions ( = .91). The diagnostic performance of FFR values measured 1-2 cm distal to the stenosis was higher than that of FFR values measured at far distal segments and was similar to that of FFR values measured at the pressure wire position in evaluating ischemic status, particularly for left anterior descending coronary artery lesions. The present study supports recent recommendations from experts to use FFR measured 1-2 cm distal to the stenosis, rather than measurements obtained at far distal segments, in clinical decision making.