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Mechanisms underlying spontaneous and induced ventricular arrhythmias in patients with idiopathic dilated

S M Pogwizd1, J P McKenzie, M E Cain

  • 1Cardiovascular Division, Washington University School of Medicine St. Louis, MO, USA.

Circulation
|December 1, 1998
PubMed

Insights

Ventricular arrhythmias in nonischemic cardiomyopathy originate from focal mechanisms in the subendocardium or subepicardium. This study used 3D mapping to reveal these electrophysiological mechanisms in patients with idiopathic dilated cardiomyopathy.

Area of Science:

  • Cardiology
  • Electrophysiology
  • Cardiac Arrhythmias

Background:

  • Nonischemic cardiomyopathy presents a significant challenge in understanding ventricular arrhythmias.
  • Idiopathic dilated cardiomyopathy often leads to life-threatening arrhythmias.
  • Electrophysiological mechanisms of these arrhythmias require precise definition.

Purpose of the Study:

  • To elucidate the electrophysiological mechanisms underlying inducible and spontaneous ventricular arrhythmias.
  • To investigate the role of conduction delay and block in arrhythmia initiation.
  • To correlate arrhythmogenic sites with myocardial fibrosis.

Main Methods:

  • Three-dimensional intraoperative mapping was conducted in 6 patients with idiopathic dilated cardiomyopathy.
  • Mapping involved 156 intramural sites to analyze ventricular tachycardia (VT) and spontaneous arrhythmias.
  • Programmed electrical stimulation was used to induce arrhythmias.

Main Results:

  • High electrode density allowed mechanism determination for most induced and spontaneous ventricular arrhythmias.
  • Extrastimuli revealed progressive conduction delay and intramural block due to slow conduction.
  • Ventricular tachycardia initiation occurred via a focal mechanism at subendocardial or subepicardial sites, distinct from areas of significant fibrosis and conduction delay.

Conclusions:

  • Both spontaneous and induced ventricular arrhythmias in end-stage idiopathic cardiomyopathy originate from focal mechanisms.
  • Arrhythmias can initiate in either the subendocardium or subepicardium.
  • Fibrosis plays a role in conduction abnormalities but is spatially separated from arrhythmia initiation sites.
Abstract

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