Monophasic action potentials from right atrial muscle recorded during heart catheterization.

Abstract

Abstract. Monophasic action potential (MAP) has been recorded in 32 patients using suction electrode technique. By repeated suctions a total of 54 recordings were obtained which were acceptable for analysis. MAP is described in SR (24 cases), CSR (3 case), AF (4 cases), AF1 (1 case) and A‐arrest (2 cases). Comparison of MAP was possible between digitalized and undigitalized patients in SR. Acute digitalis effect was studied in 2 patients and acute atropine effect in another 2. Analyses of MAP was possible with respect to the duration of total MAP in all recordings and of phases 1–2 and 3 in 7 recordings. The duration of the MAP increases with decreasing heart rate during sinus rhythm. There is no statistical evidence of differences in MAP duration between patients with and without digitalis treatment. The variability in the duration of a single MAP is associated with different relative repolarization rates of phase 3. Variations in duration of the MAP in individual patients are probably due to nonuniform vagal distribution. A short duration of the MAP in two patients with converted atrial fibrillation suggests the possibility of a short refractory period which may reflect an arrhythmia tendency.