Case 75

Abstract

A 63-year-old woman with documented bradycardia-tachycardia syndrome but no structural heart disease was implanted with a dual chamber pacing system. The low rate limit was programmed at 70 ppm, the upper tracking rate to 100 ppm. Ventricular sensitivity was programmed to 2 mV and atrial sensitivity to 1 mV. Despite her history of paroxysmal atrial arrhythmias, automatic mode switch function had not been programmed on. The procedure was accomplished without incident, and antiarrhythmic drug therapy was begun to manage her tachyarrhythmias, which consisted primarily of paroxysmal atrial tachycardia and atrial fibrillation. The patient did well over the ensuing several months, but then began to have recurrent palpitations associated with breathlessness and chest discomfort. Because these symptoms were new after pacemaker placement, she was seen ahead of schedule in the cardiology clinic, where physical examination revealed no evidence of heart failure; subsequently performed echocardiography revealed normal left and right ventricular size and systolic function, normal pulmonary artery pressure, and only mild biatrial enlargement. A pharmacologic stress test showed no evidence of ischemia. Because of irregular heart rates observed during her workup she was referred to the pacemaker clinic, where, in the course of the evaluation, Fig. 75.1 was obtained. What does the figure illustrate? How does it explain the patient's problem? What steps could be taken to solve the problem? © Springer-Verlag London Limited 2011.