Chronic epicardial His bundle recordings in awake nonsedated dogs: a new method.

Recording cardiac electrical potentials from the region of the bundle of His in the awake, nonsedated animal would allow a more physiologic evaluation of impulse transmission through the specialized atrioventricular conduction system than anesthetized preparations. We present a new technique to localize and record chronic His bundle potentials using standard electronic equipment which obviates the need for intravascular catheters or an atriotomy. Six mature and four immature mongrel dogs underwent a midline thoracotomy. The bundle of His electrogram was recorded from the right atrial epicardium alongside the noncoronary aortic cusp. A flexible tripolar electrode probe with 3 mm interelectrode distance attached to a standard electronic recorder was used to localize the area of greatest His bundle impulse. Silver solder electrodes were sutured to the designated area and the wires were externalized to the back. Electrophysiological measurements were made 1 to 20 weeks later to confirm the accuracy and stability of the His bundle electrogram. These recordings were comparable to the standard internal catheter measurements both before and during atrioventricular impulse interference caused by atrial pacing or pharmacologic intervention. Electrodes sutured to the designated area do not interfere with impulse conduction and allow stable His bundle recordings in all activity ranges in the chronic animal.