Extra- and intracellular recordings from the avjunction: discerning the mechanisms for irregular ventricular responses during supraventricular arrhythmias.
BACKGROUND
There has been a long-standing controversy regarding the mechanism(s) to explain the irregular ventricular response during atrial tachycardia (AT) or atrial fibrillation (AF) and where the site of block, if any, resides in the atrioventricular (AV) junction.


METHODS
We studied 12 Langendorff preparations perfused with modified Tyrode's solution containing 5-10 mM diacetyl monoxime which suppressed contractility but allowed the use of intracellular action potential (AP) recordings. Octapolar catheters (2-mm rings, 2-mm spacing) were secured along the tricuspid annulus from the apex to the base of the triangle of Koch and along the anterior limbus of the fossa ovalis to record extracellular, slow pathway, fast pathway, His bundle (Hb) and AV nodal (AVN) extracellular potentials as well as intracellular action potentials.


RESULTS
AT or AF induced by rapid atrial pacing showed a variety of irregular responses due to: (1) Wenckebach conduction showing decrement within the AVN and progressive diminution of extracellular AVN potentials (n = 5); (2) repetitive concealed conduction proximal to the AVN (n = 3); (3) ectopic beats arising within the AVN (n = 2); (4) ectopic beats arising at the Hb (n = 2).


CONCLUSIONS
In this experimental preparation, extracellular and intracellular recordings provided presumptive evidence for the mechanisms causing the irregularities of the ventricular response such as repetitive concealed conduction, enhanced automaticity or electrotonically triggered activity. Also more definitive determinations of the site of block in the AV junction were also obtained.
Heart Rhythm Institute, Oklahoma University Medical Center, Oklahoma City, OK 73104, USA.
Yu
Y
Liu
Benjamin J
BJ
Scherlag
Tetsuo
T
Yagi
Eugene
E
Patterson
Warren M
WM
Jackman
Ralph
R
Lazzara
Sunny S
SS
Po
D000200:Action Potentials; D000818:Animals; D001145:Arrhythmias, Cardiac / Q000503:physiopathology; D001281:Atrial Fibrillation / Q000503:physiopathology*; D001283:Atrioventricular Node / Q000503:physiopathology*; D004285:Dogs; D004594:Electrophysiology; D006329:Heart Conduction System / Q000503:physiopathology; D066298:In Vitro Techniques; D013617:Tachycardia, Supraventricular / Q000503:physiopathology*