Division of Cardiothoracic Surgery, Department of Surgery, Washington University School of Medicine, Barnes-Jewish Hospital, St Louis, Mo; Division of Cardiothoracic Surgery, Department of Surgery, Mahidol University, Ramathibodi Hospital, Bangkok, Thailand.
Division of Cardiothoracic Surgery, Department of Surgery, Washington University School of Medicine, Barnes-Jewish Hospital, St Louis, Mo.
J Thorac Cardiovasc Surg. 2018 Nov;156(5):1871-1879.e1. doi: 10.1016/j.jtcvs.2018.05.078. Epub 2018 Jun 5.
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.
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.
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).
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.
本研究旨在通过犬模型中的可调式左房室分流器，确定慢性左心房容量超负荷对心房解剖结构、血流动力学和电生理学的影响。
16 只犬接受了左心室和左心房之间分流器的植入。假手术动物（n=8）接受了正中胸骨切开术，但未植入分流器。使用 250 个双极心外膜电极测定心房激活时间和有效不应期。在初始和 6 个月终末研究时记录双心房压力、全身压力、左心房和左心室直径和容积、心房颤动诱导率和持续时间。
基线分流分数为 46%±8%。左心房压力从 9.7±3.5mmHg 增加到 13.8±4mmHg（P<.001）。在终末研究时，左心房直径从基线的 2.9±0.05cm 增加到 4.1±0.6cm（P<.001），左心室射血分数从 64%±1.5%下降到 54%±2.7%（P<.001）。诱导的心房颤动持续时间（中位数，范围）在分流组为 95 秒（0-7200），而假手术组为 0 秒（0-40）（P=.02）。与假手术组相比，分流组的总激活时间更长（72±11ms 比 62±3ms，P=.003）。与假手术组相比，分流组右心房而不是左心房的有效不应期更短（右心房有效不应期：156±11ms 比 141±11ms，P=.005；左心房有效不应期：142±23ms 比 133±11ms，P=.35）。
本研究建立的二尖瓣反流犬模型重现了临床二尖瓣反流中的机械和电重构。左心房增大，左心室收缩功能相应下降，心房激活时间延长，有效不应期缩短，心房颤动易感性增加。该模型为理解二尖瓣反流导致心房颤动的重构提供了一种手段。
