Optical Coherence Tomography-Defined Plaque Vulnerability in Relation to Functional Stenosis Severity and Microvascular Dysfunction.

OBJECTIVES: This study sought to investigate the relationship of unstable plaque features with physiological lesion severity and microvascular dysfunction.

BACKGROUND: The functional severity of epicardial lesions and microvascular dysfunction are both related to adverse clinical outcomes.

METHODS: We investigated 382 de novo intermediate and severe coronary lesions in 340 patients who underwent optical coherence tomography, fractional flow reserve (FFR), and index of microcirculatory resistance (IMR) examinations. Lesions were divided into tertiles based on either FFR or IMR values. The optical coherence tomography findings were compared among the tertiles of FFR and IMR. Each tertile was defined as follows: FFR-T1 (FFR <0.74), FFR-T2 (0.74 ≤ FFR ≤0.81), and FFR-T3 (FFR >0.81); and IMR-T1 (IMR ≥25), IMR-T2 (15 < IMR <25), and IMR-T3 (IMR ≤15).

RESULTS: No significant relationship was observed between FFR and IMR. The prevalence of optical coherence tomography-defined thin-cap fibroatheroma (TCFA) was significantly greater in IMR-T1 than in IMR-T2 and IMR-T3. An overall significant difference in the prevalence of TCFAs was detected among FFR tertiles, although no pairwise comparison revealed statistical significance. The prevalence of ruptured plaque was significantly greater in IMR-T1 than in IMR-T2 and IMR-T3, although no significant difference was observed between FFR tertiles. Multivariate analysis showed that FFR and IMR were independent predictors of the prevalence of TCFAs (odds ratio: 0.036; 95% confidence interval: 0.004 to 0342; p = 0.004; and odds ratio: 1.034; 95% confidence interval: 1.014 to 1.054; p = 0.001, respectively).

CONCLUSIONS: Lower FFR and higher IMR values were independent predictors of the presence of a TCFA in angiographically intermediate-to-severe stable lesions or nonculprit lesions in acute coronary syndrome.