Introduction:
Coronary angiographic anatomical stenosis has not been well correlated with physiological fractional flow reserve (FFR), however, the mechanism of the discordance remains poorly understood. We focused on the patients who had no anatomical significant stenosis by coronary angiogram (CAG) but physiological significant stenosis by FFR (reverse mismatch) in the proximal or mid left anterior descending artery (LAD). We explored what coronary CT angiography (CCTA) findings of the target lesion of the LAD predict abnormal FFR.
Methods:
ECG-gated CCTA was performed using SOMATOM Definition AS+ (128 slice Siemens) and CAG underwent within 4 weeks. FFR was measured using a pressure guide wire (verrata, Volcano) during ATP infusion. Forty consecutive reverse mismatch (with no anatomical stenosis and FFR≦0.8) pts and 40 no mismatch (with no anatomical stenosis and FFR>0.8) pts were selected.
Results:
There were no significant differences in mean age (72±10y vs 74±8y), gender (M/F 21/19 vs 28/12), coronary risk factors (DM (9 vs 17), HT(32 vs 30), dyslipidemia (23 vs 18), Smoking (5 vs 4)), angle of LAD and LCX (70±21vs71±20 deg.), proximal reference lumen area (0.14±0.14 vs 0.14±0.11 mm2) and vessel area (0.15±0.04 vs 0.15±0.06mm2), distal reference lumen area (0.11±0.12 vs 0.10±0.04mm2) and vessel area (0.14±0.13 vs 0.12±0.04mm2), grade of plaque calcification, and presence of low density plaque (8 vs 7 pts) between no mismatch and reverse mismatch groups. However, vessel area (0.21±0.07mm2, P=0.0004) and positive remodeling area index (1.40±0.26, P<0.0001) at the minimum lumen area (MLA) in reverse mismatch group were higher than those (0.16±0.05mm2, 1.01±0.18) in no mismatch groups, respectively. AUC of remodeling area index was 0.924 for diagnosis of reverse mismatch on ROC analysis. Sensitivity was 82.5%, specificity was 84.6% when the remodeling area index was 1.13.
Conclusions:
Even if anatomical significant stenosis is not observed, FFR was depressed in patients with large vessel area and positive remodeling area index derived from CCTA at MLA. Large plaque at MLA may be one of the mechanisms of reverse mismatch.
TCT-29 Mechanism of Low Fractional Flow Reserve in Lesions without angiographic significant stenosis: Role of hidden Plaque Burden