[Study of monophasic action potentials of the myocardium by endocavitary approach. Methodology]

The suction electrode makes it possible to record the monophasic action potentials (MAP) of the heart in situ. The technical characteristics of the tripolar electrode which we use are described. The O phase of the MAP is more prolonged than that of the intracellular action potential, but makes it possible to demonstrate the time of arrival of the activation wave in front of the exploring electrode. The phase 1-2 and the phase 3 have their characteristic contour in the right atrium and ventricle. The duration of repolarization makes it possible to assess the refractory period of different parts of the atrial and ventricular myocardium. The relatively simple and harmless method of recording of the monophasic action potentials by the endocardial route, both in the animal and in man, widens our investigation field of electrophysiology applied to the study of arrhythmias, of the repolarization disturbances and of the drug influences on the cell activity.