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. 2021 Apr;11(4):1406-1420.
doi: 10.21037/qims-20-754.

The value of non-invasive myocardial work indices derived from left ventricular pressure-strain loops in predicting the response to cardiac resynchronization therapy

Mengruo Zhu  1 , Yanan Wang  1 , Yufei Cheng  1 , Yangang Su  2 , Haiyan Chen  1 , Xianhong Shu  1   2
Affiliations

The value of non-invasive myocardial work indices derived from left ventricular pressure-strain loops in predicting the response to cardiac resynchronization therapy

Mengruo Zhu et al. Quant Imaging Med Surg. 2021 Apr.

Abstract

Background: Non-invasive left ventricular (LV) pressure-strain loops (PSLs), which are generated by combining LV longitudinal strain with brachial artery blood pressure, provide a novel method of quantifying global and segmental myocardial work (MW) indices with potential advantages over conventional echocardiographic strain data, which suffers from being load-dependent. This method has been recently introduced in echocardiographic software, enhancing the efficiency of MW calculations. This study aimed to evaluate the role of non-invasive MW indices derived from LV PSLs in predicting cardiac resynchronization therapy (CRT) response.

Methods: A total of 106 heart failure (HF) patients scheduled for CRT were included in the MW analysis. Global and segmental (septal and lateral at the mid-ventricular level) MW indices were assessed before CRT and at a 6-month follow-up. Response to CRT was defined as ≥15% reduction in LV end-systolic volume and ≥1 NYHA functional class improvement at 6-month follow-up compared to baseline.

Results: CRT response was observed in 78 (74%) patients. At baseline, the global work index (GWI) and global constructive work (GCW) were significantly higher in CRT responders than in non-responders (both P<0.05). Furthermore, responders exhibited significantly higher mid lateral MW and mid lateral constructive work (CW) (both P<0.001), but significantly lower mid septal MWI and mid septal myocardial work efficiency (MWE) than non-responders (all P<0.01). Baseline mid septal MWE (OR 0.975, 95% CI: 0.959-0.990, P=0.002) and mid lateral MWI (OR 1.003, 95% CI: 1.002-1.004, P<0.001) were identified as independent predictors of CRT response in multivariate regression analysis. Mid septal MWE ≤42% combined with mid lateral MWI ≥740 mmHg% predicted CRT response, with an optimal sensitivity of 79% and specificity of 82% [area under the receiver operating characteristic curve (AUC) =0.830, P<0.001].

Conclusions: Assessment of MW indices before CRT could identify the marked imbalance in LV MW distribution and can be widely used as a reliable complementary tool for guiding patient selection for CRT in clinical practice.

Keywords: Cardiac resynchronization therapy (CRT); myocardial work; non-invasive; pressure-strain loop; segmental heterogeneity.

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Conflict of interest statement

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at http://dx.doi.org/10.21037/qims-20-754). The authors have no conflicts of interest to declare.

Figures

Figure 1
Figure 1
LV PSLs (left), MWI (middle), and MWE (right) of individual examples from CRT responders and non-responders before CRT and at 6-month follow-up after CRT. (A) A CRT responder before CRT; (B) a CRT responder at 6-month follow-up after CRT; (C) a CRT non-responder before CRT; (D) a CRT non-responder at 6-month follow-up after CRT. LV global PSL is represented in red, and segmental (mid septal and mid lateral) PSL is represented in green. LV, left ventricular; PSL, pressure-strain loop; MWE, myocardial work efficiency; MWI, myocardial work index; CRT, cardiac resynchronization therapy.
Figure 2
Figure 2
Bland-Altman analysis for intra-observer variability (A) and inter-observer variability (B) of MW indices. Solid line represents bias, and dotted lines represent 95% limits of agreement for measurements performed in 30 patients. Bias was assessed by the mean of 30 differences of 2 measurements. The 95% CI: was calculated as ±1.96 SD from the mean. CI, confidence interval; CW, constructive work; GCW, global constructive work; GWE, global work efficiency; GWI, global work index; GWW, global wasted work; MW, myocardial work; MWE, myocardial work efficiency; MWI, myocardial work index; SD, standard deviation; WW, wasted work.
Figure 3
Figure 3
Correlations between changes in global MW indices and changes in mid septal MW indices. △ indicates change; GCW, global constructive work; GWI, global work index; CW, constructive work; MW, myocardial work; MWI, myocardial work index.
Figure 4
Figure 4
ROC curves for predicting response to CRT. The area under the ROC curve (AUC) for combined mid septal MWE and mid lateral MWI was greater than that of mid septal MWE or mid lateral MWI. CRT, cardiac resynchronization therapy; ROC, receiver operating characteristic; MWE, myocardial work efficiency; MWI, myocardial work index.
See this image and copyright information in PMC

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