A case of prolonged atrial pacing latency

摘要

An 80-year-old woman presented to our hospital with presyncope.Holter monitoring revealed paroxysmal atrial fibrillation and asystoledue to sick sinus syndrome. Twelve years ago, she underwent surgeryfor right breast cancer and received postoperative radiotherapy; theright atrium was included in the irradiation area. She was not takingantiarrhythmic drugs. At admission, her blood pressure was 133/72 mmHg. A 12-lead electrocardiogram revealed a heart rate of 76beats/min and inverted P waves in leads II, III, and aVF, suggesting anectopic atrial rhythm. Transthoracic echocardiography revealed normalleft ventricular systolic function. Moderate mitral and tricuspidregurgitation and bilateral atrial enlargement were observed. Theelectrolyte levels were normal. At the time of pacemaker implantation,P-wave sensing could not be confirmed with the tined lead;therefore, it was replaced with a screw lead and placed in the anteriorlocation of the tricuspid annulus after trying several positions (Figures1 and Supplementary material).1 P-wave sensing was low (0.3 mV);however, the pacing parameters were acceptable. During and afterpacemaker implantation, atrial pacing latency was prolonged to approximately300 ms from atrial pacing to atrial contraction (Figure 2).There was no abnormality in the pacing threshold and lead resistanceor lead position. No significant clinical events were documented atfollow-up 10 months later.