| BackgroundPercutaneous coronary intervention (PCI) has been appreciated by most doctors and patients. It has been proved that there is a close relationship between prognosis of CAD and left ventricular function. The whole function of left ventricle is determined by the motion and concordant of all ventricular walls. When 10% of the whole wall contracts abnormally, left ventricular ejection fraction (LVEF) decreases. The results of earlier research show that subendocardium lacks tolerance to oxygen deficiency, and suffers from all kinds of diseases easier than subepicardium. Myocardial ischemia firstly damages endocardium. Accordingly, observing the recovery of ischemic myocardium and evaluating accurately myocardial metergasis possess clinical significance and provide objective evidence for the effect of PCI. In recent years, strain rate imaging and real time 3-dimension echocardiography have been thought as the most important echocardiographic technology. There are many problems which have not been solved. (1) How dose the severity of coronary stenosis affect the strain rate on the corresponding regional cardial muscles? After PCI, how dose the strain rate on the corresponding regional cardial muscles change? (2) How dose the severity of coronary stenosis affect the strain rate and strain rate gradient between the inner half layer and the outer half layer ? After PCI, how do the strain rate and strain rate gradient change? (3) How dose the severity of coronary stenosis affect regional cardial function of the corresponding cardial muscles and their change after PCI by real-time three-dimensional echocardiography(RT-3DE)? (4) Among the quantitative parameters, which is the most sensitive parameter in assessing the severity of coronary stenosis? The above problems constitute the objective of this topic.Aims1. To assess the effects of the severity of coronary stenosis on the strain rate ofthe corresponding regional myocardium before and after PCI;2. To explore the effects of the severity of coronary stenosis on the strain rate and strain rate gradient between the inner half layer and the outer half layer before and after PCI;3. To evaluate the effects of the severity of coronary stenosis on regional cardial function of the corresponding myocardium by real-time three-dimensional echocardiography (RT-3DE) before and after PCI.4. Among the quantitative parameters, to determine which one is the most sensitive parameter in assessing the severity of coronary stenosis.Methods1. Study populationFrom July 2006 to November 2006, 35 patients (32 men; mean age (53.2±8.8) years)with CAD according to the results of coronary arteriography (CAG) in Qilu Hospital were enrolled in this study. All the patients had not less than one coronary artery which degree of stenosis was more than 70% and accepted PCI. Among the patients, the acute myocardial infraction attacked 7 patients, old myocardial infraction invaded 3 patients and 25 patients suffered from unstability angina. All the subjects were in sinus rhythm and with NYHA grades I～III cardial function. The patients with poor image quality of the heart were excluded from the study.A 17-segment model of left ventricle recommended by the American Society of Echocardiography(ASE) was used. Then, according to the degree of blood-supply coronary artery stenosis,all the regional myocardium of 28 consecutive subjects were separated into 5 groups:(l)the control group,their coronary artery was normal;(2) the one-grade groop,the degree of their blood-supply coronary artery stenosis was less than 50%;(3)the two-grade groop, the degree of their blood-supply coronary artery stenosis was 50% to 75%;(4)the three-grade groop, the degree of blood-supply coronary artery stenosis was 76% to 99%;(5)the four-grade groop, their coronary artery was occluded.2. Echocardiographic Image Acquisition(1) All TDI echocardigraphy examinations were performed on a GE Vivid 7 ultrasound machine with a M3S transducer(1.5 to 4.0MHZ) before, 1 week and 1 month after PCI. Resting two-dimensional gray-scale echocardiography and TVI were obtained from the 4-chamber and 2-chanmber views with each subject in left-lateral recumbent position and limb leads ECG monitored. Each cine-loop include at least 3 cardiac cycles. All echocardiography were stored digitally on magnetic optical disk in raw data mode for later offline analysis.(2) Full volume -three dimensional echocardiography images were acquired using PHILIPS SONOS 7500 ultrasound scanner with a X4 transducer(2.0 to 4.0MHZ) before, 1 week and 1 month after PCI. All echocardiography were stored digitally onmagnetic optical disk in raw data mode for later offline analysis. 3. Data processing and Measurements(1)Strain rate data measurementsUsing quantitative TDI analysis software, moderate shape and size of region of interest (ROI) was selected and placed ROI in each segment to get strain rate curve. Then systolic peak strain rate (S), early diastolic strain rate (E) and late diastolic strain rate (A) were measured. Each parameter was calculated from three consecutive cardiac cycles and averaged.(2) 3D data measurementsWe used PHILIPS 7500 ultrasound scanner (Holland) online QLAB analysis software to analyze the images. First, we pressed the 3DQ advanced key, then marked the mitral valve annulus and apex in end-diastole and end-systole and manually traced left ventricular endocardial line. Finally the system automatically gave the curves of global and regional volume and ejection fraction of 17 segments.4. Diagnostic value assessment of SRI and RT-3DE parametersThe range of normal values was calculated according to the values of paraments of myocardium which coronary artery was normal. Sensitivity, specificity and Youden's index of the parameters were calculated in diagnosing myocardium of different grades. Youden's index was grester than -1 and smaller than +1. The bigger Youden's index of a method was, the better was the diagnostic value.5. Statistical analysisThe statistical package used was SPSS for Windows (version 13.0). All data were expressed as mean±standard deviation (SD). Inter- and intra-group comparisons were performed with a one-way ANOVA test and post-hoc LSD-t test respectively. Comparisons among different groups at different times performed using repeated-measures ANOVA. All tests were 2-sided and statistical significance was accepted when a value of p<0.05.Results1. Change of strain rate(1) The change of strain rate on every regional myocardium before PCIS, E and A of strain rate were lower significantly in myocardium with coronary stenosis than myocardium with normal coronay artery in grade 2 or 3 coronary artery stenosis (p<0.05). S, E and A were higher in subendocardial myocardium than those in subepicardial myocardium(p<0.05). However, S, E and A were similar in subendocardial myocardium and subepicardial with occluded coronary artery (p>0.05).(2) Change of strain rate on regional myocardium before and after PCIS, E and A were similar in every segment of myocardium with coronary artery which was normal, grade 1 or grade 2. While the disparation of S, E and A was significant before, 1 week and 1 month after PCI in myocardium with the stenotic coronary artery which was grade 3 or 4 (p<0.05). When the coronary stenosis was grade 2,the change ratio of S, E and A in subendocardium was obviously higher than subepicardium (p<0.05). When the coronary stenosis was grade 3, the change ratio of S, E and A in subendocardium was obviously higher than subepicardium 1 week or 1 month after PCI (p<0.05), whereas that in subepicardium was obviously higher than subendocardium 1 week or 1month after PCI (p<0.05), when the coronary stenosis was grade 4.(3) Measurement of strain rate gradientThe gradient of S (SG): Before PCI, the disparation of SG was obvious between the grade 4 and the grade 1, 2, 3 and normal grade (p<0.05). The change of SG of every grade was similar after PCI.The gradient of E (EG): Before PCI, the disparation of EG was obvious between the grade 4 and the grade 1, 2, 3 and normal grade (p<0.05). The EG of grade 2 incresed obviously one month after PCI (p<0.05). The EG of grade 3 increased obviously one week after PCI.The gradient of A (AG): Before PCI, the disparation of AG was obvious between the grade 4 and the grade 1, 2, 3 and normal grade (p<0.05). The AG of grade 2 incresed obviously one month after PCI (p<0.05). The AG of grade 3 increased obviously one week after PCI.(4) Measurement of post systolic shortening (PSS)On strain rate curves, PSS could be recognized by high stain rate occurring during the isovolumic relaxation period, often extending into the early filling period. Of all cardiac segments with normal coronary arteries, 40% of segments showed PSS which had a lower peak value than that of the segments with coronary stenosis. There was not a significant difference between the PSS peak values of the segments with normal and grade 1 narrow coronary arteries (P>0.05) . Compared with normal cardiac segments, the segments with larger than grade 2 coronary stenosis had a higher PSS peak value (P<0.05) . The PSS peak values of the segments with grade 2 and 3 coronary stenosis decreased 1 week after PCI (P<0.05) , while those of grade 4 1 month after PCI (P<0.05) .2. Change of cardial function by three-dimensional echocardiography(1) Global performance:Compared with baseline, the global ejection fraction (EF) and stroke volume (SV) of left ventricle significantly reduced during coronary stenosis (P<0.05), while there was significant increase 1 week and 1 month after PCI (P<0.05). the EDV and ESV cut down 1 week and 1month after PCI(P>0.05).(2) Change of regional function of left ventricle:With the aggravation of coronary stenosis, REF degraded gradually (P>0.05 ) , while REDV and RESV increased gradually( P<0.05).REF with coronary stenosis increased 1 week and lmonth after PCI (P<0.05), at the same time REDV and RESV decreased (P<0.05).The change ratio of parameters of the segments with different coronary stenosis didn't show significant difference (P>0.05) .(3) left ventricular concordant contractionBefore PCI, Tmsv-16-SD, Tmsv-16-Dif, Tmsv-12-SD, Tmsv-12-Dif, Tmsv-6-SD, Tmsv-6-Dif, Tmsv-16-SD%, Tmsv-16- Dif %, Tmsv-12-SD%, Tmsv-12-Dif%, Tmsv-6-SD% and Tmsv-6- Dif % of graoup B were all greater than group A, but only the statistical significance of Tmsv-6-SD, Tmsv-16-SD%, Tmsv-16-Dif %, Tmsv-12- Dif % and Tmsv-6- Dif % was accepted (p<0.05) . Compared with Tmsv-16-SD, Tmsv-16-Dif, Tmsv-12-SD, Tmsv-12-Dif, Tmsv-6-SD, Tmsv-6-Dif, Tmsv-16-SD%, Tmsv-16- Dif %, Tmsv-12-SD%, Tmsv-12-Dif%, Tmsv-6-SD% and Tmsv-6-Dif % before PCI, those of group B and A were similar one week after PCI (p>0.05) . One month afer PCI, Tmsv-12- Dif and Tmsv-12-SD% of group A were smaller obviously than those before PCI (p<0.05) . Tmsv-6-SD, Tmsv-12-Dif and Tmsv-16-SD% of group B decreased obviously One month afer PCI, compared with those before PCI (p<0.05) .3. Diagnostic value assessment of SRI and RT-3DE parametersAll measurements could detect the change of ischemic myocardial functoin. After studing sensitivity, specificity and Youden's index of the parameters, we discovered that in grade 2, the Youden's indexes of S and E of subendocardium were 0.56 and 0.53, while the Youden's indexes of other parameters were smaller than 0.5. In the grade 3 and 4, the Youden's indexes of A of subepicardium and the gradient of A were smaller than 0.21, while the Youden's indexes of other parameters were close to 0.50.Conclusions(1) With the aggravation of coronary stenosis, the peak strain rate of the corresponding segments decreased gradually, and then incraesed after PCI;(2) There was a significant difference between the peak strain rate of the inner layer and the outer layer in normal cardiac segments. When coronary stenosis became more severe, the difference became smaller and even disappeared. The difference was obvious after PCI;(3) With the aggravation of coronary stenosis, the regional volume of the cardiac segments with coronary stenosis became larger and EF smaller. The parameters improved obviously after PCI.(4)The evaluation of cardiac function by SRI and RT3DE suggested that timely PCI could improve the cardiac function of CAD patients obviously.
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