Thin-Cap Fibroatheroma Rather Than Any Lipid Plaques Increases the Risk of Cardiovascular Events in Diabetic Patients: Insights from the COMBINE OCT-FFR Trial

Background: Autopsy studies have established that thin-cap fibroatheromas (TCFAs) are the most frequent cause of fatal coronary events. In living patients, optical coherence tomography (OCT) has sufficient resolution to accurately differentiate TCFA from thick-cap fibroatheroma (ThCFA) and not lipid rich plaque (non-LRP). However, the impact of OCT-detected plaque phenotype of nonischemic lesions on future adverse events remains unknown. Therefore, we studied the natural history of OCT-detected TCFA, ThCFA, and non-LRP in patients enrolled in the prospective multicenter COMBINE FFR-OCT trial (Combined Optical Coherence Tomography Morphologic and Fractional Flow Reserve Hemodynamic Assessment of Non-Culprit Lesions to Better Predict Adverse Event Outcomes in Diabetes Mellitus Patients). Methods: In the COMBINE FFR-OCT trial, patients with diabetes and ≥1 lesion with a fractional flow reserve >0.80 underwent OCT evaluation and were clinically followed for 18 months. A composite primary end point of cardiac death, target vessel-related myocardial infarction, target-lesion revascularization, and hospitalization for unstable angina was evaluated in relation to OCT-based plaque morphology. Results: A total of 390 patients (age 67.5±9 years; 63% male) with ≥1 nonischemic lesions underwent OCT evaluation: 284 (73%) had ≥1 LRP and 106 (27%) non-LRP lesions. Among LRP patients, 98 (34.5%) had ≥1 TCFA. The primary end point occurred in 7% of LRP patients compared with 1.9% of non-LRP patients (7.0% versus 1.9%; hazard ratio [HR], 3.9 [95% CI, 0.9-16.5]; P=0.068; log rank-P=0.049). However, within LRP patients, TCFA patients had a much higher risk for primary end point compared with ThCFA (13.3% versus 3.8%; HR, 3.8 [95% CI, 1.5-9.5]; P<0.01), and to non-LRP patients (13.3% versus 1.9%; HR, 7.7 [95% CI, 1.7-33.9]; P<0.01), whereas ThCFA patients had risk similar to non-LRP patients (3.8% versus 1.9%; HR, 2.0 [95% CI, 0.42-9.7]; P=0.38). Multivariable analyses identified TCFA as the strongest independent predictor of primary end point (HR, 6.79 [95% CI, 1.50-30.72]; P=0.013). Conclusions: Among diabetes patients with fractional flow reserve-negative lesions, patients carrying TCFA lesions represent only one-third of LRP patients and are associated with a high risk of future events while patients carrying LRP-ThCFA and non-LRP lesions portend benign outcomes. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT02989740.