Hunt G B, Ross D L
Department of Medicine, Westmead Hospital, NSW, Australia.
Pacing Clin Electrophysiol. 1988 May;11(5):550-61. doi: 10.1111/j.1540-8159.1988.tb04550.x.
The effects of isoproterenol, atropine, and metoprolol on atrioventricular (AV) and ventriculoatrial (VA) conduction were studied in 30 normal dogs under pentobarbital anesthesia using percutaneously introduced catheters. The inducibility of AV junctional reentry was also assessed before and after drug administration. Resting AV conduction was normal in all dogs, but VA conduction was present in only 57%. Isoproterenol facilitated both antegrade and retrograde conduction, with a preferential effect on retrograde conduction. VA conduction was demonstrated after isoproterenol in 91% of dogs. After testing all drugs, VA conduction was demonstrable in at least one study in 97% of dogs. Atropine had less effect than isoproterenol, suggesting that basal vagal tone was not high in this model. Dual AV nodal pathways were detectable in the antegrade direction in four (13%) dogs, and in the retrograde direction in an additional four (13%) dogs. Single AV junctional echoes were inducible with atrial stimulation in one dog with dual antegrade pathways, but were inducible with ventricular stimulation in at least one study in 83% of dogs with intact retrograde conduction. Sustained AV junctional reentry was never induced before or after drug administration. In conclusion, VA electrical continuity is almost always intact in the normal dog, but its demonstration is significantly modified by the autonomic nervous system. Isoproterenol has preferential effects on retrograde conduction and may have selective influence on distal AV nodal conduction. Twenty-six percent of normal dogs have evidence of dual AV nodal pathways. Single AV junctional echoes are inducible with ventricular stimulation in the majority of dogs and are a normal finding. Sustained AV junctional reentry is not inducible in the normal intact dog heart.
在30只戊巴比妥麻醉的正常犬中，使用经皮插入的导管研究了异丙肾上腺素、阿托品和美托洛尔对房室（AV）和室房（VA）传导的影响。在给药前后还评估了房室交界区折返的诱发情况。所有犬的静息AV传导均正常，但仅有57%存在VA传导。异丙肾上腺素促进了顺向和逆向传导，对逆向传导有优先作用。异丙肾上腺素给药后，91%的犬出现了VA传导。在测试所有药物后，97%的犬在至少一项研究中可检测到VA传导。阿托品的作用小于异丙肾上腺素，表明该模型中基础迷走神经张力不高。在4只（13%）犬中可检测到顺向双房室结径路，另外4只（13%）犬可检测到逆向双房室结径路。在一只具有顺向双径路的犬中，心房刺激可诱发单个房室交界区回波，但在83%具有完整逆向传导的犬中，至少在一项研究中，心室刺激可诱发单个房室交界区回波。给药前后均未诱发持续性房室交界区折返。总之，正常犬的VA电连续性几乎总是完整的，但其显示会受到自主神经系统的显著影响。异丙肾上腺素对逆向传导有优先作用，可能对远端房室结传导有选择性影响。26%的正常犬有双房室结径路的证据。大多数犬心室刺激可诱发单个房室交界区回波，这是正常表现。正常完整犬心脏中不能诱发持续性房室交界区折返。
