Ectopic atrial rhythms in the primate

P-wave polarity was studied in small primates during electrical stimulation of both atria. Negative P-waves in Leads II, III, and aV_F were obtained during stimulation of the lower right atrium near the inferior vena cava, the lower anterior left atrium near the inferior pulmonary vein, and the infero-posterior left atrium. The P-R interval was affected inconsistently. These studies confirm findings originally observed in the canine and human heart, and call for caution in making the diagnosis of “coronary rhythm” and “left atrial rhythm.” The term “ectopic atrial rhythm” seems preferable.