Optimization-Based Speckle Tracking Algorithm for Left Ventricle Strain Estimation: A Feasibility Study.

Speckle tracking echocardiography (STE) is a widespread method for calculating myocardial strains and estimating left ventricle function. Since echocardiographic clips are corrupted by speckle decorrelation noise, resulting in irregular, nonphysiological tissue displacement fields, smoothing is performed on the displacement data, affecting the strain results. Thus, strain results may depend on the specific implementations of 2-D STE, as well as other systems' characteristics of the various vendors. A novel algorithm (called K-SAD) is introduced, which integrates the physiological constraint of smoothness of the displacement field into an optimization process. Simulated B-mode clips, modeling healthy and abnormal cases, were processed by K-SAD. Peak global and subendocardial longitudinal strains, as well as regional strains, were calculated. In addition, 410 healthy subjects were also processed. The results of K-SAD are compared with those of one of the leading commercial product. K-SAD provides global mid-wall strain values, as well as subendocardial and regional strain values, all in good agreement with the ground-truth-simulated phantom data. K-SAD peak global longitudinal systolic strain values for 410 healthy subjects are quite similar for the different regions: - 17.02 ± 4.02%, - 19.00 ± 3.45%, and - 19.72 ± 5.06% at the basal, mid, and apical regions, respectively. Improved performance under noisy conditions was demonstrated by comparing a subgroup of 40 subjects with the best image quality with the remaining 370 cohort: K-SAD provides statistically similar global and regional results for the two cohorts. Our study indicates that the sensitivity of strain values to speckle noise, caused by the post block-matching weighted smoothing, can be significantly reduced and accuracy enhanced by employing an integrated one-stage, physiologically constrained optimization process.

Differential effects of coronary artery stenosis on myocardial function: the value of myocardial strain analysis for the detection of coronary artery disease.

BACKGROUND: Speckle-tracking imaging is a novel method for assessing left ventricular (LV) function and ischemic changes. The aim of this study was to assess the predictive value of two-dimensional longitudinal strain in the detection of longitudinal LV dysfunction and the identification of coronary artery disease (CAD) in patients hospitalized with angina. METHODS: Two-dimensional strain software was extended to allow the analysis of numerous longitudinal strain traces in the entire left ventricle and generate a histogram of peak systolic strain (PSS) values for the left ventricle and for each coronary territory. In each histogram, the value of the 10% worst strain values (PSS(10%)) was determined. Global strain, segmental PSS, and PSS(10%) were analyzed in 97 patients hospitalized with angina and had normal LV function, who underwent coronary angiography, and 51 patients with low probability of CAD. Echocardiography was performed 2.9 ± 2 days after admission. RESULTS: Sixty-nine patients had significant CAD on coronary angiography. Significant differences were observed in all strain parameters between patients with and without CAD. PSS(10%) showed the best accuracy in detecting CAD, with an area under the receiver operating characteristic curve of 0.85. The areas under the curve for global strain and segmental PSS were 0.80 and 0.76, respectively. The optimal cutoff for PSS(10%) was -13.9%, with sensitivity and specificity of 86% and 75%, respectively. PSS(10%) was better than segmental PSS in the detection of CAD in each coronary territory. CONCLUSIONS: In patients hospitalized with angina who have significant CAD on coronary angiography, longitudinal systolic function is impaired. Histogram analysis improved the accuracy of longitudinal strain analysis in detecting global and regional impaired function.

Effect of medical therapy for heart failure on segmental myocardial function in patients with ischemic cardiomyopathy.

The adjustment of medications and dosages to the needs of individual patients with heart failure is mostly intuitive, but even when their effect on global myocardial function is measured by classic indexes, their effect on segmental function is overlooked. This study was conducted to assess the feasibility of using echocardiographic myocardial strain imaging to evaluate the effect of medication on global and segmental function in 21 ambulatory patients with heart failure (mean age 65+/-11 years) who had echocardiographic studies performed before and 2 hours after ingesting their regular morning medications. The ejection fraction, global and regional strain, and time to regional peak strain were compared between the 2 examinations. Medication induced no significant changes in mean ejection fraction (28.6+/-7.8% to 27.5+/-9.9%) and mean global strain (-9.5+/-3.6% to -9.8+/-3.2%). Changes in segmental strain depended on baseline function: normal segments (peak strain more negative than -12%) deteriorated (-15.5+/-2.7% to -13.7+/-4.6%, p<0.0001), but dysfunctional segments (peak strain less negative than -8%) improved (-5.3+/-2.0% to -7.4+/-4.3%, p<0.0001). Medication also improved segmental synchronization: average time to peak strain of segments in which peak strain was attained before aortic valve closure increased (325+/-69 to 375+/-100 ms, p<0.0001), but that of segments with postsystolic shortening at baseline decreased (451+/-93 to 435+/-93 ms, p<0.006). Thus, the time interval between time to peak strain of segments with systolic and post-systolic shortening at baseline was halved after medication. In conclusion, medications for heart failure induced an increase in the echocardiographically determined peak strain of myocardial segments with impaired function at baseline but decreased the peak strain of normally contracting segments. Medications also improved the synchronization of myocardial contraction. Neither the global ejection fraction nor global strain reflected these changes. Thus, medication tended to improve the homogeneity of left ventricular contraction.