| Background and ObjectiveCoronary angiography(CAG) has been generally accepted as the gold standard for detecting coronary artery disease (CAD).Those candidates for valve replacement who are aged over 50 years should be routinely screened with CAG before operation.The aim of this study is to compare the diagnostic value of myocardial contrast echocardiography (MCE) in CAD with CAG during the screening process,then discuss the repeatability and the probalble factors affecting the detection of MCE.MethodsPatients30 Consective patients with New York heart association (NYHA) functional classⅡ～Ⅲpresenting to hospital with years valvular heart disease were included in the study.The excluded criteria is that patients combining Diabetes Mellitus or tachyarrhythmia (＞120 beat per minute) and left bundle branch block(LBBB).All the patients have no history of drug allergy.There are 13 men and 17 women with the mean age of 60.7 years (range:38～76 years).They were all performed transthoracic echocardiography and MCE,which most of them were performed CAG or 99mTc methoxyisobutylisonitrile (MIBI) single-photon emission computed tomography (SPECT).Myocardial contrast echocardiographyTwo dimensional echocardiography (2DE) and MCE were performed with a Sonos 7500 system (Philips Ultrasound) coupled with a 1～3 MHz transducer capable of power modulation imaging. "Angio"mode and contrast settings were activated. The MI (mechanical index) was set at 0.1 and 2D gain was 70%. SonoVue (Bracco,Italy) was used as the ultrasound contrast agent.ECG was recorded during the performance.SonVue at 2.5ml was diluted with 5ml normal saline flush and intravenously injected as a slow bolus.Microbubbles were destroied when the left ventricle (LV) had same video intensity with right ventricular(RV).Contrast enhanced images were acquired from the apical 4-chamber, 2-chamber,3-chamber and parasternal midpapillary short-axis views. 10 Cardiac cycle images after flash were recorded by the tape and Magneto Optical disk.MCE images analysisUsing the method of modified Simpson's to measure and compare the indexes of the LV systolic function at 2DE and MCE images including ejection fraction (EF),end-diastolic volume (EDV),end-systolic volume (ESV) and stroke volume(SV). Semiquantitative analysis was to estimate myocardial perfusion initially. The simple visual scoring was defined one score as positive value.Therefore, we can calculate the sensitivity,specificity,and positive and negative predictive values. MCE quantitative analysis was to assess regional myocardial perfusion exactly. The American society of ehocardiography (ASE)16-segment LV model was used.The MCE images were analyzed off-line using the QLAB software (Philips Medical Systems,version 4.0) and the refilling curve was obtained automatically. MCE images with artifact and attenuation of sound were excluded. The region of interest was placed in middle of the entire thickness of the myocardium,excluding the high intensity endocardial and epicardial borders.Time versus video intensity is fitted to an exponential function:y(t)=A (l-exp-βt)+C,where "y" is the video intensity, "A" is the video intensity plateau,βis the microbubbles mean velocity and A×βis the blood flow volume.The LV segments were divided into observation group and control group based on the results of CAG or 99mTc-MIBI SPECT.The regional myocardial perfusion was also compared with the results of CAG or 99mTc-MIBI SPECT. Whether the types of valvular heart disease affect the results was also analyzed in this study.Statistical analysisAll the continuous variables were expressed as mean±SD.Paired-samples t test was used to compare continuous variables between 2DE and MCE method.One-sample t test was used to compare continuous variales between the observation group and the control group. One-way ANOVA was used to compare the MCE variables among various types of the disease. Interobserver variability was done to measure the values of A,βand A×β.For differences,a value of p＜0.05 was considered significant.ResultNo patient has symptoms of allergy to the contrast agent.By the method of modified Simpson's, only EDV was found significantly larger than at 2DE images.The sensitivity, specificity,and positive and negative predictive values of MCE semiquantitative analysis for detecting CAD were 12.9%,92.19%,44.44% and 68.60%. A×βwas significant difference between the observation group and the control group. The video intensity plateau,the microbubbles mean velocity and the blood flow volume in the observation group were lower than in the control group.The area under the curve (AUC) of receiver operating characteristic (ROC) was 0.70.For patients with valvular heart disease,A×β≤2.12 predicts CAD with the sensitivity of 71.0% and specificity of 60.9%.No significantly difference was found among different types of valvular heart diseases with normal results of CAG or 99mTc-MIBI SPECT.Excellent reproducibility of MCE quantitative analysis was found for the value of A,βand A×β(r=0.894,0.825,0.936).ConclusionsMCE is a new technique including the ability to assess blood flow perfusion at bedside in one setting,simultaneous assessment of myocardial function, shorter imaging time, immediate availability of the results, and the ability to determine the ischemic threshold.Comparing MCE with CAG and 99mTc-MIBI SPECT,quantitative analysis has a good result of sensitivity,specificity and repeatability.It can be used to detect the coronary artery disease in patients who combined with valvular heart disease.
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