Abstract 17688: Computational Analysis of Criteria Combinations for VH-TCFA: A Comparison of Culprit Plaques in Stable and Unstable Coronary Syndromes
Intro: Thin cap fibroatheroma (TCFA) by Virtual Histology Intravascular Ultrasound (IVUS-VH) is arbitrarily defined as necrotic core (NC) ≧10% without overlying fibrous tissue and % plaque ≧40. We analyzed stable angina pectoris (SAP) and unstable coronary syndrome (ACS) lesions to seek an alternative TCFA definition to differentiate SAP and ACS by the incidence of VH-TCFA.
Methods: IVUS-VH with automated pullback was performed in 78 patients with ACS (52 lesions) or SAP (33 lesions). IVUS-VH data underwent blinded adjudication with VIAS software. Data was compared by t-test for morphologic features, and Fisher’s exact with correction for multiple comparisons for compositional features assessing 106 different criteria combinations for TCFA in 3-slice and lesion length (LL) (>50% plaque) analysis. Circumferential elemental analysis of VH slices for morphology/burden parameters with 72 wedges of 5º was also performed. TCFA definitions altered % NC (>5%, >10%, >15%, >20%, >25%), NC absolute and relative %, luminal distance, excluding NC behind dense calcium (DC), 2-D or 3-D connectivity of NC to lumen, and arc of NC.
Results: With plaque burden/morphology parameters, there was no difference in the 3 slice analysis except for DC(6.2 v 9.6% p= 0.045). For LL analysis ACS had a higher eccentricity index (2.0 vs. 1.8 p= 0.05) and greater CSA minimal plaque thickness (0.81 vs. 0.75 mm p=0.02). Using the Prospect TCFA definition, there was no difference between SAP and ACS (36/47 vs. 23/25 p=0.20 for 3-slice; 39/47 vs. 24/25 for LL p= 0.15). Computational Analysis of 106 alternative TCFA criteria combinations demonstrated, after correcting for multiple tests, only one defintion with significance (18.5% ACS and 4% SAP p=0.04). This 3-slice TCFA definition included 15% NC threshold, majority of NC within 0.5 mm of lumen, and elimination of fibrous tissue threshold.
Conclusion: TCFAs based on the standard IVUS-VH definition were not more frequently found in ACS. Using a computational approach to create 106 alternative TCFA definitions only 1 was able to differentiate ACS from SAP, with low sensitivity and little discrimination. IVUS-VH TCFA can predict lesions at higher risk of ACS but there is limited ability of IVUS-VH definitions to differentiate SAP and ACS lesions.
- © 2012 by American Heart Association, Inc.