LA Strain Remains Robust to Bundle Branch Block in Dilated Cardiomyopathy

Cardiovascular (cMRI) identified that left bundle branch block (LBBB) does not significantly alter left atrial (LA) strain parameters in patients with ischemic or nonischemic dilated cardiomyopathy (DCM), reinforcing the reliability of LA strain as a functional marker even in the presence of this common conduction abnormality.

The retrospective, single-center study is published in The International Journal of Cardiovascular Imaging.

“In this study, we investigated whether LBBB has an influence on LA strain values in patients with and without LV [left ventricular] dilatation,” wrote the researchers of the study. “We found that in patients with ischemic and nonischemic DCM, LV dilatation and dysfunction were associated with a significant impairment of LA reservoir and conduit strain as well as corresponding strain rates regardless of the presence of LBBB.”

Testing Whether Conduction Delay Confounds a Prognostic Imaging Marker

LA strain parameters derived from cMRI have emerged as sensitive predictors of adverse outcomes in patients with DCM, with reservoir and conduit strain identified as independent prognostic markers in prior research. LBBB, a conduction disorder present in up to 30% of patients with DCM, causes dyssynchronous LV contraction that some echocardiographic studies have linked to disordered atrial mechanics. Until now, no study had systematically examined whether LBBB confounds LA strain measurements in this population—a gap with direct implications for how confidently clinicians can interpret the marker.

The investigators conducted a retrospective analysis of 81 individuals undergoing cMRI between 2015 and 2024: 20 controls without DCM or LBBB, 21 patients with LBBB but no DCM, 20 patients with DCM but no LBBB, and 20 patients with both DCM and LBBB. LA and LV volumes and strain were assessed semi-automatically using Circle Cardiovascular Imaging and Segment software.

Ventricular Dilation, Not Conduction Delay, Drove Strain Impairment

LA reservoir and conduit strain, along with their corresponding strain rates, were significantly impaired in patients with DCM compared with controls (reservoir strain, P = .003; conduit strain, P = .022).

Critically, the presence of LBBB did not produce significant additional changes in LA reservoir, conduit, or booster strain, either in controls or in patients with DCM. Two-way analysis of variance confirmed that LA strain and strain rate were significantly associated with LA dilation but not with LBBB, with no significant interaction between them.

One exception emerged: LA conduit strain rate was significantly lower in patients with LBBB than in controls (P = .005) and was independently associated with LBBB in adjusted analysis, a finding the authors said warrants further investigation, potentially tied to elevated end-diastolic LV pressure in LBBB. Intra- and interobserver reliability for strain measurements was excellent, with intraclass correlation coefficients above 0.95.

These findings align with previously reported LA strain prognostic data. Earlier cMRI research found that LA reservoir strain outperformed conventional ventricular function and late gadolinium enhancement measures in predicting outcomes in DCM, independent of conduction abnormalities.²

Managed Care Implications

For health systems and payers evaluating advanced cardiac imaging protocols, these findings support continued confidence in LA strain as a reliable, reproducible risk-stratification tool for patients with DCM—including the substantial subset who also have LBBB—without requiring separate interpretive adjustments or additional testing based on conduction status. This may help justify appropriate utilization of cMRI-based strain analysis in risk stratification pathways without inflating costs tied to confounder-driven follow-up imaging.

“Taken together, in patients with ischemic and nonischemic DCM, LA strain and strain rate measures show sufficient robustness to the presence of LBBB as a common conduction abnormality in these patients, underscoring their consistent and reliable applicability as functional markers,” wrote the researchers.¹ “However, we found significantly lower LA conduit strain rates in patients with LBBB compared to controls, and further studies are needed to investigate the implications of this result.”

References

1. Petersen A, Kamieniarz P, Meteva D, et al. Influence of left bundle branch block on left atrial strain parameters in patients with ischemic and non-ischemic dilated cardiomyopathy. Int J Cardiovasc Imaging. Published online July 21, 2026. doi:10.1007/s10554-026-03773-y
2. Raafs AG, Vos JL, Henkens MTHM, et al. Left atrial strain has superior prognostic value to ventricular function and delayed-enhancement in dilated cardiomyopathy. JACC Cardiovasc Imaging. 2022;15(6):1015-1026. doi:10.1016/j.jcmg.2022.01.016