title: Effect of acute ventricular dilatation on fibrillation thresholds in the isolated rabbit heart.
abstract: We examined the effects of ventricular dilatation on epicardial refractoriness and ventricular fibrillation threshold (VFT) in the isolated, retrograde-perfused rabbit heart. Ventricular size was modified by acutely changing the volume of a fluid-filled balloon secured within either the left or right ventricle. Left ventricular dilatation (to an end-diastolic pressure of 30-38 mmHg) significantly decreased left ventricular effective refractory period (ERP) and myocardial wavelength (calculated as ERP x conduction velocity). Left VFT (determined by scanning the vulnerable period with a train of pulses) decreased from 6.4 +/- 0.9 to 4.4 +/- 0.5 mA; P < 0.01) with left but not right ventricular dilatation. Right ventricular dilatation was associated with a decrease in the right ventricular ERP and myocardial wavelength, and right VFT decreased from 13.6 +/- 1.8 to 4.1 +/- 0.3 mA (P < 0.01). Changes in VFT correlated with the decrease in local refractoriness and shortening of local excitation wavelength.
authors.affiliation: Department of Medicine, University of Colorado Health Sciences Center, Denver 80262.
authors.forename: S
authors.initials: S
authors.lastname: Jalal
authors.forename: G R
authors.initials: GR
authors.lastname: Williams
authors.forename: D E
authors.initials: DE
authors.lastname: Mann
authors.forename: M J
authors.initials: MJ
authors.lastname: Reiter
mesh_terms: D000818:Animals; D002304:Cardiac Pacing, Artificial; D002404:Catheterization; D004056:Differential Threshold; D006321:Heart / Q000502:physiology*; D006352:Heart Ventricles; D066298:In Vitro Techniques; D011817:Rabbits; D014693:Ventricular Fibrillation / Q000503:physiopathology*