Investigations of a monophasic action potential (MAP) at a cellular level in experiments provided basic findings on the course of the electric activity in cells in various cardiac compartments and tissues under physiological conditions and various pathological states and has become an indispensible part of the evaluation of electrophysiological properties of various cardiovascular drugs, in particular antiarrhythmic drugs. A record corresponding to the MAP can be obtained also from the surface of the human endocardium during catheterization by means of a Franz contact catheter. MAP is induced by pressure depolarization after applying the catheter to the endocardium of different cardiac compartments. The objective of the author's preliminary communication is to present the initial experience with the MAP record from right-sided cardiac compartments during a routine electrophysiological examination in five patients at rest, during increasing stimulation of the atria and ventricles and after administration of some antiarrhythmic drugs. The authors evaluated the duration of MAP, the duration of 10%, 50% and 90% repolarization, the MAP amplitude, the activation time, repolarization time and the incidence of spontaneous diastolic depolarization. The recording and evaluation of MAP during the routine electrophysiological examination can contribute to the understanding of the development of arrhythmias, the action of antiarrhythmic drugs and to the evaluation of ischaemic changes of the myocardium. The clinical impact of MAP records is not clear so far and its assessment will call for further experience with this method.

Keywords: Action Potentials; Adult; Cardiac Catheterization; Electrocardiography /methods/; Female; Humans; Male; Middle Aged