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QRS duration, left bundle branch block morphology, and outcomes among patients who undergo septal myectomy

Changpeng Song1, Jingang Cui1, Xinli Guo1

  • 1Department of Special Medical Treatment Center, State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China.

Heart Rhythm
|December 15, 2025
PubMed

Insights

New-onset left bundle branch block (LBBB) with a QRS duration of 150 milliseconds or longer after septal myectomy increases risks for mortality, pacemaker implantation, and left ventricular systolic dysfunction in hypertrophic cardiomyopathy patients.

Area of Science:

  • Cardiology
  • Cardiac Electrophysiology
  • Cardiovascular Surgery

Background:

  • The clinical significance of new-onset left bundle branch block (LBBB) and QRS duration following septal myectomy for hypertrophic cardiomyopathy (HCM) is not well-defined.
  • Understanding these post-operative changes is crucial for predicting patient outcomes.

Purpose of the Study:

  • To investigate the impact of LBBB morphology and QRS duration on long-term clinical outcomes in patients undergoing septal myectomy.
  • To identify specific electrocardiographic patterns associated with adverse events after the procedure.

Main Methods:

  • Analysis of 1655 patients with HCM who underwent septal myectomy without prior conduction abnormalities.
  • Stratification into three groups based on postoperative QRS features: no LBBB, LBBB with QRS <150 ms, and LBBB with QRS ≥150 ms.
  • Cox proportional hazards models were used to assess risks for mortality, pacemaker implantation, and left ventricular systolic dysfunction (LVSD).

Main Results:

  • Left bundle branch block (LBBB) developed in 50% of patients post-myectomy.
  • Patients with LBBB and QRS duration ≥150 ms faced significantly higher risks of all-cause mortality (aHR=2.17) and pacemaker implantation (aHR=4.36) compared to those without LBBB.
  • The risk of developing LVSD was substantially elevated in the LBBB with QRS ≥150 ms group (aHR=7.04).

Conclusions:

  • While overall survival post-myectomy is generally excellent, new-onset LBBB with a QRS duration of 150 ms or greater identifies a high-risk subgroup of HCM patients.
  • This subgroup requires closer monitoring and timely interventions to mitigate risks of LVSD and other adverse outcomes.
Abstract

Keywords:
LVSDLeft bundle branch blockOutcomesPacemakerQRS durationSeptal myectomy

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