The effect of adenosine on impulse formation and propagation in the heart. Electrophysiologic studies and clinical implications.

The effect of adenosine on impulse formation and conduction in the heart was studied in 20 dogs by the sinus node artery perfusion technique. Electrophysiologic studies were performed by using His electrograms and epicardial electrograms of the atria and left ventricle. This action potential was recorded in the hearts of 10 dogs. After adenosine administration, there first developed bradycardia, then sinus arrest. Instead of sinus rhythm, there appeared a junctional escape rhythm. Atrial extrasystoles could be also regularly detected. Impulse conduction slowed down in the AV node. Similar changes could be observed after local administration of verapamil. Adenosine decreased the resting membrane potential and the maximum rate of depolarisation in atrial tissue preparations. Experimental data support the assumption that slow Ca++ channels are involved in the bradycardiac effect of adenosine.