he major cause of acute coronary syndrome (ACS) is disruption of an atherosclerotic plaque and the subsequent formation of a thrombus. 1 Pathological examinations have revealed that thin cap fibroatheroma (TCFA) is frequently found in patients who die of ACS, and plaque rupture usually occurs in a lesion with an abundant necrotic core and an overlying thin fibrous cap. [2][3][4] Recently, a spectrum analysis of intravascular ultrasound (IVUS)-derived radiofrequency data based on a pathological analysis has demonstrated more detailed quantitative information on plaque composition and morphology than a gray-scale analysis. 5-8 TCFA identified by Virtual Histology (VH-TCFA) are recognized more frequently in patients with ACS than in those with stable coronary artery disease. 6,8 Similarly, several coronary angioscopic studies have demonstrated that yellow plaques are commonly observed at the culprit lesion of ACS. 9-13 Furthermore, quantitative evaluation of the yellow plaque could be available with newly developed software using L*a*b* color space. [13][14][15][16] Angioscopic examination of ex vivo human tissue samples has indicated that a coronary plaque with high-intensity, yellow color regions (b*value >23) consists of lipid cores beneath a TCFA (fibrous cap thickness <100 μm). 15 However, there is no available comparison of plaque classification determined by VH-IVUS and by angioscopic findings. The present study investigated the characteristics of VH-TCFA in comparison with the angioscopic yellow color intensity as determined by quantitative colorimetry.
Methods
Patient SelectionInitially, we enrolled 67 patients who had a definable culprit plaque on pre-interventional IVUS and coronary angioscopic examinations. Ten disrupted plaques including ulceration on IVUS or massive thrombi on angioscopy (thrombus area ≥50% of visual field) in 10 patients were excluded because the VH analysis may have provided unreliable tissue characterization and no established algorithm for thrombus. Finally, 57 plaques in 57 patients were analyzed. The Medical Ethics Committee at Chiba-Hokusoh Hospital approved this study, and written informed consent was given by all patients before participation.
Clinical DemographicsThe clinical data and information about clinical presentation were based on chart reviews. Stable angina pectoris (SAP) was defined as a positive stress test and no change in the frequency, duration or intensity of chest symptoms within 4 weeks. In each patient, the culprit lesion was identified by a combination of electrocardiographic findings, (Received August 18, 2008; revised manuscript received October 5, 2008; accepted October 24, 2008; released online January 16, 2009