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Conduction of the impulse in the ischemic myocardium--implications for malignant ventricular arrhythmias

A G Kléber1

  • 1Department of Physiology, University of Bern, Switzerland.

Experientia
|October 15, 1987
PubMed

Insights

Sudden cardiac death is often caused by ventricular arrhythmias due to impaired blood flow to the heart. These arrhythmias result from altered electrical impulse propagation in ischemic heart tissue, primarily due to changes in the action potential.

Area of Science:

  • Cardiology
  • Electrophysiology
  • Cardiac Pathophysiology

Background:

  • Ventricular arrhythmias are a leading cause of sudden cardiac death.
  • These arrhythmias stem from regional disturbances in myocardial perfusion, leading to altered impulse propagation.
  • Re-entrant excitation circuits are a key mechanism in ischemic regions.

Purpose of the Study:

  • To investigate the electrophysiological mechanisms underlying conduction disturbances in acute myocardial ischemia.
  • To elucidate the role of action potential changes in the development of ventricular arrhythmias.

Main Methods:

  • Impulse mapping during ventricular tachycardia and fibrillation was employed.
  • Analysis focused on changes in impulse propagation patterns and their beat-to-beat variability.
  • Electrophysiological properties, including action potential and ionic currents, were examined.

Main Results:

  • Circus movement pathways for excitation were observed to be dynamic, changing shape and location.
  • Tissue regions exhibited variable conduction block and rapid conduction on a beat-to-beat basis.
  • Depression of the ischemic action potential, caused by sodium channel inactivation and slow recovery, was identified as the primary driver.

Conclusions:

  • Altered impulse propagation and re-entry in ischemic myocardium are driven by changes in the cardiac action potential.
  • Partial inactivation and delayed recovery of the rapid sodium inward current significantly contribute to conduction abnormalities.
  • While acidosis may play a role, increased cell coupling or extracellular resistance are less critical factors in acute ischemia-induced conduction disturbances.

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