The initiation of the heart beat

Peng Sheng Chen, Boyoung Joung, Tetsuji Shinohara, Mithilesh Das, Zhenhui Chen, Shien Fong Lin

Research output: Contribution to journalReview article

34 Scopus citations

Abstract

During a normal lifetime, the heart may beat over 2 billion times, but the mechanisms by which the heart beats are initiated remain a subject of intense investigation. Since the discovery of a pacemaker current (If ) in 1978, multiple studies have shown that rhythmic changes in membrane voltage (the "membrane voltage clock") underlie the mechanisms of automaticity. The If is a depolarization current activated during hyperpolarization. Therefore, when the cardiac cells recover, the If is activated and slowly depolarizes the cell membrane, leading to the onset of action potential. Recent studies, however, suggest that increased intracellular Ca (Cai) induced by spontaneous rhythmic sarcoplasmic reticulum Ca release (the "calcium clock") is also jointly responsible for the initiation of the heart beat. Elevated Cai activates another ionic current (the sodium-calcium exchanger current or INCX), leading to spontaneous phase 4 depolarization. Under normal conditions, both clocks are needed to initiate the heart beat. Malfunction of the clocks is associated with sinus node dysfunction in heart failure and atrial fibrillation. More studies are needed to determine how both clocks work together to initiate heart beat under normal and disease conditions.

Original languageEnglish (US)
Pages (from-to)221-225
Number of pages5
JournalCirculation Journal
Volume74
Issue number2
DOIs
StatePublished - Feb 2010

Keywords

  • Electrophysiology
  • Sick sinus syndrome
  • Sinoatrial node

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine

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