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

Abstract

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