Modulation of AV nodal and Hisian conduction by changes in extracellular space

• Published in: American journal of physiology. Heart and circulatory physiology 1999-03, Vol.276 (3), p.H953-H960
• Main Authors: Lurie, Keith G, Sugiyama, Atsushi, McKnite, Scott, Coffeen, Paul, Hashimoto, Keitaro, Motomura, Shigeru
• Format: Article
• Language: English
• ISSN: 0363-6135; 1522-1539
• DOI: 10.1152/ajpheart.1999.276.3.h953

1  Cardiac Arrhythmia Center, University of Minnesota, Minneapolis, Minnesota 55455; 2  Department of Pharmacology, Yamanashi Medical Center, 409-38 Yamanashi; and 3  Department of Pharmacology, Hirosaki Medical Center, 036 Hirosaki, Japan Previous studies have demonstrated that the extracellular space (ECS) component of the atrioventricular (AV) node and His bundle region is larger than the ECS in adjacent contractile myocardium. The potential physiological significance of this observation was examined in a canine blood-perfused AV nodal preparation. Mannitol, an ECS osmotic expander, was infused directly into either the AV node or His bundle region. This resulted in a significant dose-dependent increase in the AV nodal or His-ventricular conduction time and in the AV nodal effective refractory period. Mannitol infusion eventually resulted in Wenckebach block ( n  = 6), which reversed with mannitol washout. The ratio of AV nodal to left ventricular ECS in tissue frozen immediately on the development of heart block ( n  = 8) was significantly higher in the region of block (4.53   ± 0.61) compared with that in control preparations (2.23 ± 0.35,   n  = 6,  P