Novel Strain Rate Index of Contractility Loss Caused by Mechanical Dyssynchrony - A Predictor of Response to Cardiac Resynchronization Therapy -

Abstract

Background: Time-delay indexes are limited in predicting the response to cardiac resynchronization therapy (CRT), partly because they do not reflect the residual left ventricular (LV) contractility. We computed a novel index of LV contractility loss due to dyssynchrony (the strain rate (SR) dispersion index: SRDI) by using the speckletracking SR and compared the efficacy of the SRDI, time-delay indexes, and strain delay index (SDI), the previously reported index of wasted energy due to dyssynchrony, for predicting the acute response to CRT. Methods and Results:Echocardiography was performed in 19 heart failure patients (LV ejection fraction (EF) 25±6%) before and 2 weeks after CRT. The standard deviation of time to peak velocity, or strain, was calculated as time-delay indexes. The SRDI was calculated as the average of segmental peak systolic SR minus global peak systolic SR. Longitudinal SDI (L-SDI), longitudinal SRDI (L-SRDI), and circumferential SRDI (C-SRDI) significantly correlated with the change in global longitudinal strain (∆global LSt), whereas the time-delay indexes did not. Although the time-delay indexes were comparable between responders (∆global LSt ≥0.3%) and nonresponders, the L-SDI, L-SRDI, and C-SRDI were greater in responders. The area under the receiver operating characteristic curve of the L-SRDI, L-SDI, and C-SRDI for predicting responders was 0.89, 0.81, and 0.78, respectively. Conclusions:The SRDI correlated fairly well with an improvement in global LV systolic function after CRT. (Circ J 2011; 75: 2167 - 2175

Strain Rate Dispersion Index Can Predict Changes in Left Ventricular Volume and Adverse Cardiac Events Following Cardiac Resynchronization Therapy

“…28 Indeed, we previously reported that the SRDI strongly correlated with changes in LV global contractility immediately after CRT. 17 Moreover, the present study confirmed that the SRDI could predict LV reverse remodeling after CRT. However, although the SRDI gives an estimated increase in global LV systolic function by CRT, the estimation is based on the assumption that recoordination will be successfully achieved after CRT.…”

“…17 Briefly, we calculated it as the averaged all segmental peak systolic SRs minus global peak systolic SR (Figure 1). The time-global SR curve was extracted by averaging 6 segmental SRs at each frame for the short-axis view, and by averaging 18 segmental SRs at every 2% of the R to R interval for the 3 apical views to adjust for differences in the R to R intervals among the apical images.…”

“…Fourth, although SR could be a more suitable marker of myocardial contractility than strain, our previous report showed similar predictive values between the SRDI and strain delay index, a strain-derived index of wasted energy by dyssynchrony. 17 We thus consider that the differences in load dependency between SR and strain would not strongly affect their predictive values. Fifth, although the frame rates of 2DST were comparable to those used in the previous report of 2DST-derived SR, 37 those of TDI were considerably low, which could reduce the accuracy of TDI-SD.…”

“…17 However, the efficacy of the SRDI for predicting reductions in both LV volume in the chronic phase and cardiac ardiac resynchronization therapy (CRT) is an established therapy for patients with advanced heart failure (HF) and prolonged QRS duration. 1-3 However, a certain group of patients do not respond favorably to CRT despite having a wide QRS duration.…”

Tissue Doppler Imaging Dyssynchrony Parameter Derived From the Myocardial Active Wall Motion Improves Prediction of Responders for Cardiac Resynchronization Therapy

“…reported a novel index of LV contractility loss using STI to improve the ability to predict the effects of CRT compared with dyssynchrony parameters. 27 Novel findings with STI of the pathophysiological relation between LV contraction abnormalities and conduction disturbances may contribute to better understanding of the response mechanism for CRT and prediction of CRT's effects. 28 …”