Success in Avoiding Reoperation through Follow-up in a Case of Sick Sinus Syndrome Despite Transient Marked Elevation in Atrial Threshold

The patient was a 43-year-old male whose chief complaint was syncope. Electrocardiography at the first visit revealed escaped rhythm (38 bpm). After hospitalization he developed reverse common atrial flutter (AFL) and underwent catheter ablation. After termination of atrial flutter by ablation, sinus arrest was noted, allowing a diagnosis of bradycardia-tachycardia syndrome, for which the patient underwent pacemaker implantation. Twenty days after implantation, a marked elevation of atrial threshold was noted, despite absence of a change in lead resistance or position, and atrial capturing was not possible even at the maximum output (8 V/ 1.2 ms). The cause remained unknown and the patient was followed without active intervention. Atrial threshold normalized during the follow-up, but no change was noted in lead resistance or position even at the time of normalization.