In the clinical records from the electrocardiographic laboratory of the Massachusetts General Hospital are some examples of unusual mechanisms of the auricular pacemaker worthy of discussion.
1. AN UNUSUAL TYPE OF AURICULAR PAROXYSMAL TACHYCARDIA
Simple paroxysmal tachycardia is defined as a tachycardia of sudden onset and sudden offset, with a striking regularity of rate, and arising from an abnormal point or ectopic focus in the auricles or ventricles. Such, indeed, is the usual occurrence. Some irritable spot in the heart takes away the initiative or impulse formation from the pacemaker or sino-auricular node in the right auricle. Whipping up the heart on its own account, it carries on this dominant rhythm till exhausted when once more the normal pacemaker resumes its work after a short pause.Theoretically, an abnormal pacemaker like the ectopic focus is beyond nervous control and ceases its activity spontaneously. Sometimes, one finds clinically, however, that nervous