Virtual Histology Intravascular Ultrasound Assessment Of Coronary Atherosclerotic Plaque Characteristics

AimsTo identify the difference of plaque components between diabetic patients and non-diabetic patients and also between patients with stable angina pectoris and patients with acute coronary syndrome by using virtual histology intravascular ultrasound(VH-IVUS).To assess the potential relationship between the extent of stenosis and calcification detected by angiography and coronary plaque composition detected by VH-IVUS.Furthermore,to explore the characteristics of VH-defined 'vulnerable plaques'.MethodsBetween September 2008 and March 2009,76 consecutive patients with 'coronary heart disease' underwent baseline angiography and preintervention VH-IVUS at the 2^nd DSA room of the Cardiac Catheterization Laboratory of Zhongshan Hospital. VH-IVUS was performed in the patients whose at least one of the main coronary arteries had over 50%diameter stenosis and on the other hand,the IVUS catheter could pass the target vessel or the other main vessel(included LM,LAD,LCX and RCA).The baseline clinical characteristics were collected.Conventional gray-scale qualitative and quantitative IVUS analyses were preformed.Planar VH-IVUS analysis was performed at the minimal luminal area(MLA) and the site of the largest necrotic core(LNC).Volumetric VH-IVUS analysis was performed along a 10-mm segment centered on the minimal luminal area.Results120 vessels were collected in the 76 patients.17 of them were LM(14.2%),62 were LAD(51.7%),12 were LCX(10%) and 29 were RCA.VH-IVUS was performed on 159 lesions.70 of them(44%) were culprit and target lesions and 89 of them(56%) were not.There were 11 ruptured plaques(6.9%),77 VH-TCFA(48.4%)and 71 non VH-TCFA(44.7%).More analysis was as follow:1.A comparison of coronary plaque composition between DM patients(22 patients) and non-DM patients(48 patients) was performed.Among the baseline clinical characteristics and gray-scale IVUS data,HbAlc was significantly higher in DM group(7.3±0.2%vs 5.9±0.1%,p＜0.001).Planar VH-IVUS analysis at the MLA and LNC found no significant difference.Volumetric VH-IVUS analysis showed that the percentage of DC volume was significantly greater(55.4±2.8%vs 63.2±2.1%, p=0.038) in DM group and the percentage of FT volume was significantly smaller (15.9±1.7%vs 11.5±1.25%,p=0.047).The frequency of VH-TCFA in both groups has no significantly difference.2.The patients whose culprit/target lesions were collected were devided into two groups.One was SAP group(18 patients),the other was ACS group(52 patients).The NT-proBNP was higher but LVEF data was lower in ACS group.Gray-scale IVUS only found that the culprit lesion was more eccentrical in ACS group than in SAP group(EI 8.5±1.0 vs 5.5±0.8,p=0.022).Planar VH-IVUS analysis at the MLA and LNC found no significant difference.Volumetric VH-IVUS analysis showed that the percentage of FT volume was significantly smaller(53.5±3.2%vs 63.3±2.0%, p=0.014) in SAP group and the percentage of DC volume was significantly greater (16.7±2.0%vs 11.5±1.2%,p=0.029).The frequency of VH-TCFA in both groups has no significantly difference.3.In the 159 lesions,51(32.1%) had＜50%visual diameter stenosis(non-significant stenosis group) and 108(67.9%) had≥50%visual diameter stenosis(significant stenosis group).VH-IVUS analysis showed that the percentage of NC area was greater(16.6±0.9%vs 10.3±1.4%,p=0.021) in the non-significant group at the MLA site.Volumetric VH-IVUS analysis showed that the percentage of FF volume was significantly greater(7.9±3.9%vs 6.0±0.5%,p=0.06) and the percentage of NC volume was significantly smaller(18.2±0.9%vs 22.1±1.2%,p=0.012).No matter at the MLA site or in the volumetric analysis,the extent of angiography stenosis had positive correlation with FT and FF percentage and had negative correlation with NC and DC percentage(p＜0.05).4.In the 70 culprit and target lesions,51(72.9%) were non-significantly angiographic calcificated and 19(27.1%) were moderate to severe.More patients with moderate to severe calcification had DM history(52.6%vs 23.5%,p=0.04).The radians,length, density and mixed types of calcification detected by grey-scaled IVUS were greater in the moderate to severe calcification group(p＜0.05).Calcification radians was its independent prognosis factor(OR=3.97).VH-IVUS analysis showed larger DC area and percentage and smaller percentage of FT volume(51.2±3.1%vs 64.3±1.9%, p=0.001).VH-IVUS DC percentage was its independent prognosis factor(OR=5.3×10⁵).5.Among the total 159 lesions,the percentage of FT(52.5±1.4%vs 67.6±1.6%) and FF(6.4±0.5%vs 8.5±0.4%) volume was significantly smaller and the percentage of DC(17.6±0.9%vs 9.5±1.0%) and NC(23.5±0.9 vs 14.4±0.9) volume was significantly greater(p＜0.05).The composition between VH-TCFAs and ruptured plaques had no significantly difference.Conclusion1.Using VH-IVUS,coronay plaque characteristics in DM patients showed an increased amount of dense calcium compared with non-DM patients.It indicated that calcification might be the potential mechanism of cardiovascular complications in DM patients.2.In our study,plaque components obtained by VH-IVUS showed more fibrous tissue and less dense calcium in ACS compared to SAP lesions.The data were in contradiction with the pathological data,which indicated the uncertain relationship between angina pectoris classification and coronary plaque components.3.Non-significant(＜50%diameter stenosis by angiography) lesions had more necrotic core than significant(≥150%diameter stenosis by angiography) lesions had.It showed that different stenosis lesions had different plaque components. Plaques in early stage had low stability and could result in clinical cardiac events.4.The extent of coronary artery calcium detected by angiography was related to the radians,length,density and mixed types detected by grey-scaled IVUS.It was also related to the content of dense calcium measured by VH-IVUS.Further more, the radians and content of calcium were the independent prognosis factors of angiographic calcium extent.5.Compared with stable plaques,the 'vulnerable plaques' defined by VH-IVUS not only had more necrotic core but also more dense calcium.This indicated the unstable mechanism under these two components.