Variability of AV nodal potentials recorded, in vivo: direct demonstration of dual AV nodal physiology.
OBJECTIVE
We developed a method to record extracellular A-V nodal potentials in the beating dog heart, in vivo.


METHODS
In eleven Na-pentobarbital anesthetized, open-chest dogs, an octapolar electrode catheter (2 mm rings, 2 mm spacing) was inserted through a purse-string suture in the coronary sinus (CS) distal to the ostium and positioned electrographically so that the tip electrode recorded a His bundle (Hb) potential.


RESULTS
Stable recordings of A-V nodal potentials (amplitude, 178 +/- 94 microV; duration 78 +/- 26 msec) were consistently made during sinus rhythm from the second and/or third bipolar pairs of electrodes. Programmed atrial stimulation and vagal stimulation resulted in loss of amplitude and increased duration of the A-V nodal potentials associated with A-H prolongation. In another series of experiments, crushing the sinus node in 6 dogs resulted in AV nodal rhythms with AV nodal potentials of varying amplitudes (132 to 840 microV) and durations (range 25 to 71 msec) as the earliest activation which preceded the Hb, atrial and ventricular deflections. One dog, showing dual AV nodal physiology as documented from the AV nodal function curve, had two distinctly different AV nodal potentials. The low-level, longer duration potentials were associated with longer (slow pathway) A-H intervals; whereas the shorter higher amplitude potentials (fast pathway) showed shorter A-H intervals, each occurring at a critical paced cycle length.


CONCLUSIONS
We conclude that consistent extracellular AV nodal electrograms can be recorded in vivo although the configuration of these potentials varies depending on heart rate, autonomic stimulation and different arrhythmic conditions such as AV nodal escape rhythms and dual AV nodal physiology.
Scherlag
Benjamin J
BJ
Department of Veterans Affairs Medical Center and Cardiac Arrhythmia Research Institute at the University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA. benjamin-scherlag@ouhsc.edu
Yamanashi
William S
WS
Yagi
Tetsuo
T
Patterson
Eugene
E
Lazzara
Ralph
R
Jackman
Warren M
WM
D000200:Action Potentials; D000818:Animals; D001283:Atrioventricular Node / Q000502:physiology*; D002036:Bundle of His / Q000502:physiology; D002304:Cardiac Pacing, Artificial; D004285:Dogs; D004558:Electric Stimulation; D004562:Electrocardiography; D022062:Electrophysiologic Techniques, Cardiac; D006325:Heart Atria; D014630:Vagus Nerve / Q000502:physiology