Moore E N, Spear J F
School of Veterinary Medicine, University of Pennsylvania, Philadelphia 19104.
Heart Vessels Suppl. 1987;2:32-9.
We tested the multiple-wavelet hypothesis by studying the initiation and maintenance of atrial fibrillation in normal mules, horses, cows, calves, and goats. Persistence of atrial fibrillation in animals with a large atrial mass was compared with results in adult goats and calves having a smaller atrial mass. Atrial stimulation in clinically normal cows, mules, calves, and goats was accomplished using an intra-atrial stimulating catheter with rapid atrial pacing (30/s). Once initiated, atrial fibrillation persisted for 95,120,125 min, 3 days, and 8 weeks in five adult cows, respectively. In contrast, in five calves, atrial fibrillation failed to persist for more than a few minutes. Similar results were found in the small atria of adult goats, indicating that atrial size rather than maturity of the atrial myocardium was responsible. In addition, to demonstrate that this was not a species-dependent phenomenon, it was shown in adult mules that atrial fibrillation could persist for 24 h or more once initiated. These studies are consistent with the multiple-wavelet hypothesis for initiation and maintenance of atrial fibrillation. We also studied the ventricular response in atrial fibrillation. We found that as many as nine consecutive atrial responses can be concealed within the atrioventricular (AV) node associated with a long R-R interval during atrial fibrillation. Although concealment of rapid atrial activity normally occurred in the AV node, one case of infranodal block was observed. It has also been suggested that subsidiary AV junctional pacemakers may be the cause of the ventricular irregularity. However, our experimental studies using microelectrodes in isolated tissue and extracellular bundle of His recordings in intact animals failed to demonstrate that this mechanism was responsible for the irregularity of the ventricular response in atrial fibrillation.
我们通过研究正常骡子、马、牛、犊牛和山羊心房颤动的起始和维持情况，对多小波假说进行了验证。将心房质量大的动物心房颤动的持续情况与心房质量较小的成年山羊和犊牛的结果进行了比较。使用心房内刺激导管以快速心房起搏（30次/秒）对临床正常的牛、骡子、犊牛和山羊进行心房刺激。一旦引发心房颤动，五只成年牛的心房颤动分别持续了95、120、125分钟、3天和8周。相比之下，在五只犊牛中，心房颤动未能持续超过几分钟。在成年山羊的小心房中也发现了类似结果，表明是心房大小而非心房心肌的成熟度起了作用。此外，为证明这不是物种依赖性现象，在成年骡子中发现，心房颤动一旦引发可持续24小时或更长时间。这些研究与心房颤动起始和维持的多小波假说一致。我们还研究了心房颤动时的心室反应。我们发现，在心房颤动期间，与长R-R间期相关的房室（AV）结内可隐匿多达九个连续的心房反应。虽然快速心房活动的隐匿通常发生在房室结内，但观察到了一例结下阻滞情况。也有人提出，房室交界区辅助起搏器可能是心室节律不齐的原因。然而，我们在离体组织中使用微电极以及在完整动物中记录希氏束细胞外电活动的实验研究未能证明该机制是心房颤动时心室反应节律不齐的原因。
