Effect of ventricular dilatation on defibrillation threshold in the isolated perfused rabbit heart

Peter Ott, Michael J. Reiter

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


Introduction: Ventricular dilatation has important electrophysiologic effects, but its effect on ventricular defibrillation threshold (DFT) is unknown. Methods and Results: A fluid-filled, latex balloon was placed in the left ventricular cavity of 19 isolated rabbit hearts. In each experiment, an undilated volume (equivalent to a left ventricular end-diastolic pressure of approximately 0 mmHg) was compared to a dilated volume achieved by adding 1.0 mL of saline (n = 10) or 5% dextrose (n = 9) to the intracavitary balloon. Left ventricular effective refractory period (ERP) and DFT were determined at each volume. Defibrillation was attempted with a monophasic shock delivered between a patch electrode positioned over the posterior left ventricle (cathode) and a metallic aortic cannula (anode). DFT was determined using a modified 'down/up' protocol with 10-V steps. Ventricular dilatation increased the left ventricular end-diastolic pressure from 0 ± 0.5 mmHg to 35 ± 3 mmHg (P < 0.001), decreased the average left ventricular ERP 15% (from 116 ± 3 msec to 99 ± 3 msec; P < 0.001), and increased the average DFT 30% (from 96 ± 4 V to 125 ± 7 V; P < 0.001). In one third of experiments, the dilated DFT was ≤ 150% of the DFT at zero volume. The mechanism of the observed increase in DFT is unknown but may be related to the decrease in refractoriness observed with ventricular dilatation. Conclusion: Acute ventricular dilatation in this model increased DFT an average of 30%, an effect not previously described. This observation may have implications for patients with implantable cardioverter defibrillators.

Original languageEnglish (US)
Pages (from-to)1013-1019
Number of pages7
JournalJournal of cardiovascular electrophysiology
Issue number9
StatePublished - 1997
Externally publishedYes


  • Arrhythmia
  • Congestive heart failure
  • Defibrillation
  • Ventricular fibrillation

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)


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