Background: Cardiac imaging-based indices of left ventricular (LV) mechanical dyssynchrony have limited accuracy for predicting the response to cardiac resynchronization therapy (CRT). The aim of the study was to evaluate the diagnostic performance of mechanical dyssynchrony indices in a study population of patients with severely reduced ejection fraction and no LV myocardial scar assessed by cardiovascular magnetic resonance (CMR), and either left bundle branch block (LBBB) or normal QRS duration. Methods: We retrospectively identified 80 patients from three centers, with LV ejection fraction ≤35%, no scar by CMR late gadolinium enhancement, and either normal electrocardiographic QRS duration (<120ms) and normal frontal plane electrical axis (-30 to +90 degrees) (control, n=36), or LBBB by Strauss' criteria (LBBB, n=44). The CMR image data from these subjects is made publicly available as part of this publication. CMR feature tracking was used to derive circumferential strain in a midventricular short-axis cine image. Using circumferential strain, mechanical dyssynchrony was quantified as the circumferential uniformity ratio estimate (CURE) and the systolic stretch index (SSI), respectively. Results: Both CURE and SSI resulted in measures of mechanical dyssynchrony that were more severe (lower CURE, higher SSI) in LBBB compared to controls (CURE, median [interquartile range], 0.63 [0.54-0.75] vs 0.79 [0.69-0.86], p<0.001; SSI 9.4 [7.4-12.7] vs 2.2 [1.2-3.6], p<0.001). SSI outperformed CURE in the ability to discriminate between LBBB and controls (area under the receiver operating characteristics curve [95% confidence interval] 0.98 [0.95-1.00] vs 0.77 [0.66-0.86], p<0.001; sensitivity 93 [84-100] vs 75 [61-86] %, p=0.02; specificity 97 [92-100] vs 67 [50-81] %, p=0.003). Conclusions: The ability to discriminate between LBBB and normal QRS duration among patients with severely reduced ejection fraction and no scar was fair for CURE and excellent for SSI.

EH is the founder of the company Medviso AB which develops medical image analysis software. RN has received research grants from Philips Volcano and Biotronik. RJK is a consultant for Abiomed. BDA has received research grants from Boston Scientific and Abbott, and consultation fees from Abbott, Medtronic, Biotronik, and Biosense Webster. MU is principal investigator on a research and development agreement regarding cardiovascular magnetic resonance between Siemens and Karolinska University Hospital. The remaining authors have nothing to disclose that is relevant to the contents of this paper.

This study did not receive any funding.

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IRB of Duke University Medical Center gave ethical approval for this work. IRB of University of Pittsburgh Medical Center gave ethical approval for this work Swedish Ethical Review Authority gave ethical approval for this work.

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The datasets generated and/or analyzed during the current study, as well as code needed to reproduce all aspects of the current study, are available in the Figshare repository, https://doi.org/10.6084/m9.figshare.15155596. The most recent version of the analysis code is available in the Github repository, https://github.com/dloewenstein/dillacs-study.

https://doi.org/10.6084/m9.figshare.15155596

https://github.com/dloewenstein/dillacs-study