| Objectives: Strain rate (SR) imaging provides a quantitative segmental analysis of myocardial function and movement. It's also useful in assessing the range of myocardial ischemia or infarction. However, whether the coronary stenosis extent can be evaluated using strain rate (SR) imaging has not been studied. The purposes of the study were (1) to assess parametersεand SR of the regional left ventricular myocardial function using ultrasound-based strain rate and strain imaging. (2) to examine whether regional myocardial function parametersεand SR using ultrasound-based strain rate and strain imaging changed with increasing age in healthy people, and the feasibility and reproducibility of strain rate (SR) imaging in evaluating the overall function of left ventricular. (3) to evaluate the left anterior descending coronary stenosis extent in coronary heart disease using strain rate (SR) imaging compared with coronary arteriongraphy and establish practical cut-off value for 3 grades (<50%/50%-74% />75% occlusion).Methods: The study involved 102 healthy volunteers (15-74y, 49male) and 34(61.7±12.1y, 24male) patients with stable angina pectoris.1. In 102 healthy subjects (equally subdivided by decades), the mitral flow velocities in early diastole (E) and atrial contraction (A) and their ratios were calculated using conventional echocardiograms. Ejection fraction (EF) was measured by Simpson's method in the apical 4-chamber views. color doppler myocardial imaging (CDMI) with strain rate (SR) imaging was used to quantify regional longitudinal from apical 4, 3 and 2 views, respectively. Each wall of the ventricular was divided into base, middle and apex. All measurements were averaged from three cardiac cycles. From extractedεcurves, the systolicεvalue was calculated. From the extracted SR curves, peak values for systole (SRs), early diastole (SRe) and isovolumic relaxation period (SRivr) were calculated. The average values of SR indices were defined as SRs index and SRe index.2. Conventional echocardiograms and color doppler myocardial imaging (CDMI) with strain rate (SR) imaging were performed in 34 patients with stable angina pectoris and compared to 35 healthy volunteers. 34 patients with left anterior descending coronary artery disease were all diagnosed by coronary angiographic and divided into 3 grades(<50%/50%-74% />75% occlusion). All of the parameters(EF,ε, SRs, SRe and SRivr) in anterior wall and anterior septal were measured.3. The reproducibility of theεand SR measurements was evaluated as interobserver and intraobserver variability in 30 segments (10 in basal, mid and apical segments each) that were randomly selected by 2 independent observers in healthy subjects. Interobserver variability was assessed by analysis of longitudinal regions by 2 independent investigations. Intraobserver variability was analyzed by 1 investigator 2 times with an interval of 4 weeks.Results:1. 8.80% segments of the 102 normal studies were excluded because of poor image quality. In healthy individuals, longitudinal myocardialε, SRs and SRivr had no significant impact of the same level in different walls and theεand SR of base level segment were significantly larger than others in the same wall (P<0.001). Moreover, Age had no significant effect on the myocardial longitudinal deformation though the two parameters decreased with age. A significant positive relationship was observed between the SRs index and left ventricular ejection fraction (r=0.84, p<0.01). Also, there was a positive correlation between the SRe index and mitral flow E(r=0.88, p<0.01).2. 201 segments (<50%, 54 50%-74%, 49 >75%, 50 collateralized 48) of the 34 patients with stable angina pectoris and 182 segments in control were qualified for the study.ε(-6.4%±2.8%VS11.1%±3.2%,p=0.000 ), SRs (-0.78±0.42 VS -1.25±0.89S-1 in controls, p=0.000), SRe (1.12±0.57 VS 1.71±0.76S-1 in controls, p=0.000) were significantly lower in patients with coronary artery disease when compared with segments in control. But SRivr (-0.63±0.60 VS -0.1±0.59 S-1 in controls, p=0.000) increased with extent of stenosis. The cut-off value of SRivr was -0.42(sensitivity85%, specificity80%) for moderate LAD occlusion (50% -74%). The cut-off value of SRivr was -0.91 (sensitivity 91%, specificity90 %) for severe LAD occlusion (>75%). The cut-off value for mild LAD occlusion (<50%) was not statistically significant. 3. The interobserver variability forε, SR was 7.1±5.0% and 10.8±8.2%, respectively. The intraobserver variability forε, SR was 9.2±8.0% and 11.4±8.6%, respectively.Conclusions:1.The ultrasound-based strainεand strain rate (SR) imaging is a practical, noninvasive and reproductive clinical approach to quantifying regional myocardial function.2. In healthy individuals, longitudinal myocardialεand SR had no significant impact of the same level in different walls. Theεand SR of base level segment were significantly larger than others in the same wall (P<0.001). Age had no significant effect on the myocardial longitudinal deformation though the two parameters decreased with age.3. Isovolumic relaxation period (SRivr) can quantitatively differentiate LAD 50% -74% occlusion or LAD>75% occlusion. Strain rate imaging has a high sensitivity and specificity in detecting the coronary stenosis extent.
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