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Spatiotemporal heterogeneity of activation alternans in cardiomyopathy: Implications for risk stratification with

Nathan C Denham1, Adrian M Suszko1, Raja J Selvaraj2

  • 1Division of Cardiology, Peter Munk Cardiac Center, University Health Network, Toronto, Canada.

Heart Rhythm O2
|April 27, 2026
PubMed

Insights

Intracardiac activation alternans (AA) in cardiomyopathy patients are linked to ventricular arrhythmias (VA). Surface microvolt QRS alternans (QRSA) reflect these intracardiac changes, explaining their predictive value for VA.

Area of Science:

  • Cardiology
  • Electrophysiology
  • Biomedical Engineering

Background:

  • Microvolt QRS alternans (QRSA) on the surface ECG predicts ventricular arrhythmia (VA) in cardiomyopathy (CM) patients.
  • The precise intracardiac origin of QRSA remains undefined.

Purpose of the Study:

  • To investigate the spatiotemporal characteristics of intracardiac activation alternans (AA).
  • To correlate intracardiac AA with surface QRSA and subsequent VA risk.

Main Methods:

  • Recorded unipolar electrograms from left ventricular epicardium and right ventricular endocardium in 10 CM patients.
  • Quantified AA and QRSA using spectral methods during atrial pacing at varying rates.
  • Utilized a heart model to simulate AA and assess its relationship with surface QRSA.
  • Followed patients for 5 years to record VA events.

Main Results:

  • AA was more prevalent in the left ventricular epicardium and late QRS complex.
  • AA prevalence and magnitude increased with heart rate, with an earlier onset than QRSA.
  • Simulated AA correlated with surface QRSA magnitude.
  • Patients with AA at 75 bpm had a significantly higher incidence of VA (100% vs. 0%).

Conclusions:

  • Intracardiac AA displays significant spatiotemporal heterogeneity and heart rate dependency in CM.
  • Surface QRSA is a noninvasive indicator of intracardiac AA.
  • This relationship likely underlies the prognostic significance of QRSA for VA.
Abstract

Keywords:
CardiomyopathyQRS alternansRisk stratificationTranslationalVentricular arrhythmia

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