The hemodynamic and atrial electrophysiologic consequences of chronic left atrial volume overload in a controllable canine model

J Thorac Cardiovasc Surg. 2018 Nov;156(5):1871-1879.e1. doi: 10.1016/j.jtcvs.2018.05.078. Epub 2018 Jun 5.

Abstract

Objective: The purpose of this study was to determine the effects of chronic left atrial volume overload on atrial anatomy, hemodynamics, and electrophysiology using a titratable left ventriculoatrial shunt in a canine model.

Methods: Canines (n = 16) underwent implantation of a shunt between the left ventricle and the left atrium. Sham animals (n = 8) underwent a median sternotomy without a shunt. Atrial activation times and effective refractory periods were determined using 250-bipolar epicardial electrodes. Biatrial pressures, systemic pressures, left atrial and left ventricle diameters and volumes, atrial fibrillation inducibility, and durations were recorded at the initial and at 6-month terminal study.

Results: Baseline shunt fraction was 46% ± 8%. The left atrial pressure increased from 9.7 ± 3.5 mm Hg to 13.8 ± 4 mm Hg (P < .001). At the terminal study, the left atrial diameter increased from a baseline of 2.9 ± 0.05 cm to 4.1 ± 0.6 cm (P < .001) and left ventricular ejection fraction decreased from 64% ± 1.5% to 54% ± 2.7% (P < .001). Induced atrial fibrillation duration (median, range) was 95 seconds (0-7200) compared with 0 seconds (0-40) in the sham group (P = .02). The total activation time was longer in the shunt group compared with the sham group (72 ± 11 ms vs 62 ± 3 ms, P = .003). The right atrial and not left atrial effective refractory periods were shorter in the shunt compared with the sham group (right atrial effective refractory period: 156 ± 11 ms vs 141 ± 11 ms, P = .005; left atrial effective refractory period: 142 ± 23 ms vs 133 ± 11 ms, P = .35).

Conclusions: This canine model of mitral regurgitation reproduced the mechanical and electrical remodeling seen in clinical mitral regurgitation. Left atrial size increased, with a corresponding decrease in left ventricle systolic function, and an increased atrial activation times, lower effective refractory periods, and increased atrial fibrillation inducibility. This model provides a means to understand the remodeling by which mitral regurgitation causes atrial fibrillation.

Keywords: atrial fibrillation; mitral regurgitation.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.
  • Video-Audio Media

MeSH terms

  • Action Potentials*
  • Animals
  • Atrial Fibrillation / diagnostic imaging
  • Atrial Fibrillation / etiology*
  • Atrial Fibrillation / physiopathology
  • Atrial Function, Left*
  • Atrial Remodeling*
  • Chronic Disease
  • Disease Models, Animal
  • Dogs
  • Echocardiography, Doppler, Color
  • Echocardiography, Transesophageal
  • Fibrosis
  • Heart Atria / diagnostic imaging
  • Heart Atria / physiopathology*
  • Heart Rate*
  • Mitral Valve Insufficiency / complications*
  • Mitral Valve Insufficiency / diagnostic imaging
  • Mitral Valve Insufficiency / physiopathology
  • Refractory Period, Electrophysiological
  • Time Factors
  • Ventricular Function, Left