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Relative refractoriness of left ventricular contraction underlies human tachycardia-induced mechanical and electrical

Takeshi Kashimura1, Makoto Kodama, Tohru Watanabe

  • 1Department of Cardiovascular Biology and Medicine, Graduate School of Medical and Dental Sciences, Niigata University, Niigata, Japan.

Pacing and Clinical Electrophysiology : PACE
|September 13, 2013
PubMed

Insights

Mechanical alternans (MA) and electrical alternans (EA) in heart disease patients indicate contractile force fluctuations due to relative refractoriness. This study examined left ventricular contraction refractoriness in patients with MA and EA.

Area of Science:

  • Cardiology
  • Cardiac Electrophysiology
  • Heart Failure Research

Background:

  • Mechanical alternans (MA) and electrical alternans (EA) are established predictors of adverse cardiac events.
  • Experimental data suggests calcium cycling refractoriness underlies cardiac alternans.
  • Left ventricular contraction refractoriness in patients with cardiac alternans has not been previously investigated.

Purpose of the Study:

  • To investigate the relationship between left ventricular contraction refractoriness and the presence of mechanical alternans (MA) and electrical alternans (EA) in patients with heart disease.
  • To quantify mechanical alternans using alternans amplitude (AA) and assess left ventricular contraction properties like mechanical restitution and postextrasystolic potentiation (PESP).

Main Methods:

  • Fifty-one patients with diverse heart conditions underwent incremental right atrial pacing to induce MA and EA.
  • MA was quantified by alternans amplitude (AA100 and AAmax).
  • Left ventricular contraction refractoriness was assessed via mechanical restitution curve slope (Δmechanical restitution) and PESP curve slope (ΔPESP).

Main Results:

  • MA and EA were induced in a significant proportion of patients at higher heart rates.
  • Both AA100 and AAmax showed positive correlation with Δmechanical restitution and negative correlation with ΔPESP.
  • Patients exhibiting EA demonstrated significantly greater Δmechanical restitution and absolute ΔPESP values compared to those without EA.

Conclusions:

  • Patients with MA and EA exhibit left ventricular contractile force instability during tachycardia.
  • This instability is attributed to relative refractoriness of left ventricular contraction.
  • Findings suggest a link between impaired contractile reserve and the manifestation of cardiac alternans.
Abstract

Keywords:
T wave alternanspostextrasystolic potentiationpulsus alternans

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