Experimental And Clinical Study Of Myocardial Perfusion By MSCT: Characterization Of Ischemic Heart Disease

PartⅠAnimal Study of Myocardial Perfusion Imaging by MSCTSection 1 Establishment of Acute Myocardial Infartction ModelObjective:Coronary artery angiography was performed with permanent medical threadocclusion,which aims for the establishment of acute myocardial infarction animal model.Materials and Methods:Five domestic dogs weighting 10 to 15 kg (mean:12.5 kg) withnumerical order from 1 to 5,were included in this study.Following intramuscularpre-medication with anaesthesia,Under fluoroscopy guidance,a guiding catheter wasplaced at the origin of the left coronary artery,and a coronary angiogram was obtained.Afterwards permanent suture segments occlusion of the left anterior descending (LAD)coronary artery was performed at mid-section.Coronary artery occlusion was controlledwith coronary angiograms before and after to assure the successful establishement of acuteinfarction.Pathological verification was done afterwards.Results:One animal died within 30min after the occlusion.Coronary artery occlusion wascontrolled with coronary angiograms adapted to vessel size and location,ranging fromproximal to distal focal occlusions.Intraluminal wash-out of the contrast agent and weakenwall motion were indicated in all animals.TTC staining confirmed extents and location ofMI,which included extensive infarct the left ventricular myocardium in No.1 animal,septalsegment infarct of the left ventricular myocardium in No.2-4 animal,and the apex segmentinfarct in No.5 animal.Further confirmation of early acute myocardium infarction wasachieved with HE staining.Conclusion:Establishment of acute myocardial infarction animal model by the occlusionof coronary artery is easily accessible,which can be used as the pre-clinical research formyocardial infarction. Section 2 Experimental Study of Myocardial Perfusion by MSCT:Characterization of Ischemic MyocardiumObejective:To assess the hemodynamic changes in ischemic cardiac segments usingretrospective ECG-gating contrastenhanced MSCT and its clinical value in the diagnosis ofmyocardial intarction.Materials and Methods:10 dogs were randomly grouped into study and control groupwith 5 each,and the animal preparation was the same in section 1.MSCT examinationswere performed with a 16-MSCT scanner (SOMATOM Sensation 16,Siemens,Germany)in the supine position.Serial CT scanning of whole cardiac was performed at 4,20 and 40seconds after bolus injection of 1.5ml/kg of non-ionic contrast material (Ultravist 370,Schering) followed by a 30-ml saline chaser bolus,at a flow rate of 3.5～4.5 ml/s,whichwere acquired applying a retrospectively ECG-gated examination protocol with12×1.5-mm collimation and a rotation time of 420 ms.Tube voltage was 120 kV with80mAs.Delayed enhancement scans were performed at 1,2,3,4 and 5 minute afterwards,7and 20 minutes were done to the No.2 and 5 dog in the study group.Pathologicalverification was obtained as stated in section 1.Results:Ⅰ) Time-density curves for MSCT in control froup demonstrated the maximumslope of consecutive measurements during the wash-in and wash-out period of the contrastmaterial calculated,and a flat-pattern phase after the peak enhancement.Signalintensity/attenuation was expressed as the percentage of increase over baseline ratio ofattenuation of myocardium and left ventricle blood pool,based on which the peakenhancement of the myocardium was 50%±6% with comparison to left ventricle cavum.The adjacent segments were almost the same as left ventricle cavum,in terms of peakenhancement,time to peak,etc.Ⅱ) Time-density curves for MSCT in infarct group demonstrated the minmum slope ofconsecutive measurements during the wash-in and wash-out period of the contrast materialcalculated,and a flat-pattern phase after the peak enhancement almost the same as normalones.Results of the semiquantitative analysis of the timedensity curves showed significantdifferences between infarcted and healthy myocardium for SImax,Tmax and slope,whichwere 1.56±0.52,1.00,1.00 (P＞0.05) for time to peak,0.26±0.04,0.45±0.08 (P=0.02)for peak enhancement.TTC staining confirmed extents and location of MI as indicated byMSCT.Conclusion:16-slice CT imaging allows for the differentiation of hypoperfused andnormal myocardium using retrospective ECG-gating method,which has the potential for visual and semiquantitative assessment of firstpass myocardial perfusion.PartⅡFirst-pass Myocardial Perfusion By Dual-source CTSection 1 First-pass Normal Myocardial Perfusion by Dual-source CTObjective:To investigate first-pass myocardial perfusion in normal segments during thecardiac cycle using contrast-enhanced dual-source CT,this can be future basis for theevaluation of ischemic heart disease.Materials and methods:25 health check-up patients(15 male,10 female,mean age60±12.5) without suspected coronary artery disease were enrolled as normal casesrandomly doe dual-source CT coronary angiography(Siemens SomatomDefinition,Germany).Reconstructed cardiac images in diastolic and systolic phases wasevaluated using raw data from coronary CT angiography.The attenuation value (inHounsfield units) in the myocardium was used as an estimate of myocardial perfusion.Wemeasured the subendocardial intensity of 17 segments according to the American HeartAssociation classi-fication.Systolic perfusion or diastolic perfusion was calculated bydividing the subendocardial intensity at systole or diastole,respectively,for each segmentby the mean value across all segments for each patient.T-test was used for the statistics.Results:Systolic perfusion was significantly lower than diastolic one for each segment.The difference between systolic perfusion and diastolic perfusion in ischemic segments wassignificantly lower than that in nonischemic segments (P(?)0.001).There was no significantdifference in diastolic perfusion betweenc segment 1,7,13;segment 4,10;and segment 17,which can be grouped together,as well as segment 2,3,5,6,8,9,11,12,14 and 16.The differencebetween systolic and diastolic perfusion varied among the regions.Systolicperfusion was lower than diastolic perfusion in the septal wall,whereas systolic perfusionwas higher than diastolic perfusion in few segments of the anterior and lateral walls.Systolic perfusion and diastolic perfusion in the inferior wall were similar (P(?)0.01).Conclusion:DSCT can be utilized as qualitativer evaluation for a pattern of subendocardialhypoperfusion at systole and normal perfusion at diastole characterizes ischemic myocardium.Section 2 First-pass Ischemic Myocardial Perfusion byDual-source CTObjective:To Assess the hemodynamic changes in ischemic cardiac segments during thecardiac circle using dual source CT,and the clinical value for differential diagnosis.Material and Methods:25 patients(21 male,4 female,mean age 61.5±l4.6) withconfirmed ischemic or infarct myocardial diaseas were enrolled for dual-source CTcoronary angiography(Siemens Somatom Definition,Germany).Reconstructed cardiacimages in diastolic and systolic phases was evaluated.We measured the subendocardialintensity of 17 segments according to the American Heart Association classi-fication.Systolic perfusion or diastolic perfusion was calculated by dividing the subendocardialintensity at systole or diastole,respectively,for each segment by the mean value across allsegments for each patient.Early perfusion Defect and its opposite segment was measured.The first-pass enhancement between the infarct patients(n=14) and ischemic ones(n=11)was compared using independent T-test for the statistics.Results:1)15 out of 18 with proven stenosis in LAD (83.3%) were indicated by DSCT forEarly perfusion defect,3 out of 5(60%) with proven CX stenosis were indicated by DSCT,and 4 out of 6(67.8%0 were for RCA.Good agreement was reached between DSCT andSPECT in this regard.2)systolic phase,the peak enhancement for infarction and i schemia were 44.82±15.63HU,72.73±18.47HU (P＜0.001) repectively;45.46±16.12HU,83.10±23.92HU (P＜0.001)respectively in the diastolic phase.No significant diference was indicated between thefirst-pass peak enhancement in the infarction group,while significant difference in theischemia group(P=0.003).The difference between the infarct myocardium and the oppositeone was-54.20±17.28HU in systolic phase,while-48.86±17.04HU in diastolic phase (P＜0.05).Those were-28.37±8.95HU和-24.09±9.92HU in dsystolic and iastolic phase forischemia (P＜0.05)Conclusion:Quantification of first-pass perfusion CT images with dual source CT allowscharacterization of intramural myocardial perfusion in patients with myocardial ischemia,and myocardial ischemia could be found in systolic phase much easy than diastole phase,which brings up DSCT as a potential for the comprehensive evaluation for the coronary,cardiac function and myocardium perfusion. PartⅢAssessment of The Global and Regional Left VentricleFunction by Dual Source CTObjective:To evaluate the agreement between DSCT and ECG to assess the global andregional left ventricle function in patients with coronary artery disease.Materials and Methods:25 cases with coronary disease underwent DSCT coronaryangiography (SOMATOM Definition,Siemens,Germany),and the same data were used toassess the ejection fraction (EF),fractional shortening (FS) and regional wall motion(Siemens MMWP,Germany).ECG served as reference.Results:There was no significant difference between DSCT and ECG to evaluate the EFand FS (p＞0.05),with good correlation (r=0.86 and 0.87,p＜0.001,respectively).Theagreement between DSCT and ECG in diagnosing regional wall motion abnormality wasgood.no matter counted as cases(Kappa=0.85,p＜0.001) or segments(Kappa=0.87,p＜0.001).The wall thickening fraction of the segments with abnormal motion diagnosed byDSCT were significant lower than its opposite segments(20.55%±24.10% vs 78.63%±30.98%,P＜0.01).Conclusion:With the breakthrough of the temporal resolution,DSCT permits accurateassessing left ventricle function even in patients with heart rate variability,and agreementwith routine ECG is good.DSCT is expected to provide more information for CADdiagnosis and prognosis.