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Mechanisms of calcium transient and action potential alternans in cardiac cells and tissues

William T Clusin1

  • 1Stanford University School of Medicine, Stanford, CA 94305, USA. wclusin@stanford.edu

American Journal of Physiology. Heart and Circulatory Physiology
|October 24, 2007
PubMed

Insights

Beat-to-beat changes in cardiac action potential duration (APD) and calcium transient amplitude, known as alternans, are key arrhythmia mechanisms. This review traces their physiological and pathophysiological understanding, particularly during ischemia.

Area of Science:

  • Cardiology
  • Electrophysiology
  • Cardiac Physiology

Background:

  • Cardiac action potential duration (APD) alternans and calcium transient alternans are critical mechanisms underlying cardiac arrhythmias.
  • These phenomena are interconnected and can be triggered by increased heart rate or ischemia.
  • Understanding alternans is crucial for comprehending cardiac instability.

Observation:

  • The review details the historical development of knowledge regarding APD alternans, starting from the 1960s.
  • It examines the evolution of understanding calcium-activated ion currents and calcium transient alternans.
  • The 'restitution hypothesis,' focusing on potassium channel recovery and diastolic interval, is discussed.

Findings:

  • APD and calcium transient alternans are causally linked, with beat-frequency changes or ischemia as triggers.
  • The restitution hypothesis explains alternans through the time-dependent recovery of ion channels.
  • Pathophysiology of alternans during ischemia may explain early cardiac arrest in myocardial infarction.

Implications:

  • Insights into alternans provide a basis for understanding arrhythmia generation.
  • Understanding the role of ischemia in alternans can inform strategies for acute myocardial infarction.
  • This review highlights the historical progression of key concepts in cardiac electrophysiology and arrhythmia research.

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