Correlation of myocardial fractional flow reserve with thallium-201 SPECT imaging in intermediate-severity coronary artery lesions.

Purpose: The purpose of this study was to compare the measurements of fractional flow reserve of the myocardium (FFRmyo) with results of quantitative coronary angiography (QCA) and stress single-photon emission computed tomography thallium-201 (SPECT 201Tl) imaging in patients with intermediate-severity coronary artery disease (ISCAD).
Methods: We prospectively evaluated 40 lesions of QCA-determined ISCAD in 30 patients (age, 53.3 +/- 10.2 years; 67% male) using a 0. 014 inch pressure wire during elective coronary angiography and compared the results with those of SPECT 201Tl performed within a week of angiography.
Results: There was a moderate negative correlation between percent diameter stenosis (%DS) and FFRmyo (53.1 +/- 13.4% and 0.75 +/- 0.09, respectively; r = -0.40; p = 0.01). Twenty-two out of 40 vascular territories (55%) were found to have perfusion defects (Group 1) and 18 territories (45%) were found to be normal (Group 2). While QCA-determined stenosis severity was not different between Group 1 and Group 2 (56 +/- 12% vs. 50 +/- 16%, respectively; p = 0.3), FFRmyo was found to be significantly different between the two groups (0.68 +/- 0.05 vs. 0.83 +/- 0.05, respectively; p = 0.001). When %DS and FFRmyo results were dichotomized as abnormal by 50% and < 0.75, respectively, and SPECT 201Tl was taken as the gold standard, sensitivity, specificity, positive predictive value and negative predictive value of %DS and FFRmyo were 0.55 vs. 0.91, 0.56 vs. 1.0, 0.60 vs. 1.0 and 0.50 vs. 0. 90, respectively.
Conclusion: While FFRmyo seems to accurately predict the presence of ischemia on SPECT 201Tl in patients with ISCAD, QCA does not reliably assess the physiologic impact of the same lesions.