Abstract 4409: In vivo, Raptured Plaque Fibrous Cap Thickness Assessed by Optical Coherence Tomography
Backgrounds: Thin-cap fibroatheroma (TCFA) is the precursor of plaque rupture, which accounts for a majority of coronary thrombi and coronary death. Currently, classification as fibroatheroma (FA) and TCFA is dependent on the thickness of the fibrous cap > or < 65μm reported by the autopsy study of a morphometric series of 41 ruptured plaques, in which 95% of the fibrous cap near the rupture site measured <65μm. We sought to determine the threshold of cap thickness of FA that most likely to rupture in vivo by optical coherence tomography (OCT).
Methods and Results: OCT imaging was performed in consecutive 200 patients who underwent PCI for de novo native coronary lesions. Of these, pre-PCI OCT imaging along the culprit vessel with sufficient image quality were obtained in 153 patients (acute coronary sysndrome (ACS):73, stable angina (SAP):80) and plaque characteristics were evaluated in these patients. Two observers independently analyzed OCT images using the previously validated criteria for plaque characterization. FA including TCFA and ruptured plaque (RP) were documented, and the thinnest cap thickness was measured in FA and RP. Receiver-operator characteristic curve analysis (ROC) was performed to determine the best cut-off value to diffrenciate RP and non-ruptured FA. In total, 48 RP (26 in ACS, 22 in SAP) and 69 FA (28 in ACS, 41 in SAP) were detected. The mean thickness of the thinnest ruptured cap was 63±24μm (ACS:57±13, SAP:70±32μm p=0.08), and that of FA was 125±74μm (ACS:95±67, SAP:145±72μm p=0.005). In vivo OCT-derived value including more than 95% of the fibrous cap thickness near the rupture site was 112μm in this study. The best cut-off value to differenciate RP and FA was 65μm (sensitivity: 79.7% specificity: 77.1%, AUC:0.86, p<0.0001) by ROC analysis.
Conclusions: From in vivo OCT examination, 95% of the ruptured fibrous cap thickness measured <112μm, and best cut-off value to differentiate ruptured and non-ruptured FA was determinined. In vivo TCFA cap thickness most likely to rupture might be much greater than pathologically determined value, greater variance of RP fibrous cap thickness than expected was observed in the present study.