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

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

Chawannuch Ruaengsri  1 , Matthew R Schill  2 , Timothy S Lancaster  2 , Ali J Khiabani  2 , Joshua L Manghelli  2 , Daniel I Carter  2 , Jason W Greenberg  2 , Spencer J Melby  2 , Richard B Schuessler  2 , Ralph J Damiano Jr  3
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Free PMC article

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

Chawannuch Ruaengsri et al. J Thorac Cardiovasc Surg. 2018 Nov.
Free PMC article

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.

Conflict of interest statement

Conflict of Interest Statement

R.J.D. is a speaker for AtriCure, Inc, LivaNova, Inc, CryoLife, Inc, and Edwards Lifesciences, Inc, and a consultant for Medtronic, Inc. He has received research funding and educational grants from AtriCure, Inc, and Edwards Lifesciences, Inc. All other authors have nothing to disclose with regard to commercial support.

Figures

FIGURE 1.
FIGURE 1.
The final iteration of the ventriculoatrial shunt.
FIGURE 2.
FIGURE 2.
Implanted shunt with hydraulic occlude (left). At 6 months the shunt in the LV apex showing a smooth layer of endothelium (right). LAA, Left atrial appendage; LV, left ventricle.
FIGURE 3.
FIGURE 3.
Transesophageal echocardiogram before shunt implant (A) and at 6 months (B and C). In comparing (A and B), the shunt animal demonstrated marked LA dilatation. C, Doppler flow through the shunt. LA, Left atrium; LV, left ventricle.
FIGURE 4.
FIGURE 4.
LA volume and LV ejection fraction in the sham (blue) and shunt dogs (red) over 6 months. LA, Left atrium; LV, left ventricle.
FIGURE 5.
FIGURE 5.
Activation map during right atrial appendage pacing, preshunt (left) and at 6 months (right). Total atrial conduction time at 6 months is longer and more inhomogeneous. TACT, Total atrial conduction time; LAA, left atrial appendage; RAA, right atrial appendage; PV, pulmonary vein; SVC, superior vena cava.
FIGURE 6.
FIGURE 6.
Example trichrome section from the LA near the left inferior PV in sham (A) and shunt (B).
FIGURE 7.
FIGURE 7.
Schematic diagram of the atria showing percentage of fibrosis at the different regions biopsied. IVC, Inferior vena cava; SVC superior vena cava.
VIDEO 1.
VIDEO 1.
Video clip of MR shunt implantation. Video available at: https://www.jtcvs.org/article/S0022-5223(18)31508-3/fulltext
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