SummaryA 68-year-old man with sick sinus syndrome (SSS) was referred to our department for pacemaker implantation. After implantation of a pacemaker with rate-responsive dual chamber (DDDR) mode and minimized ventricular pacing (MVP) functions, paroxysmal atrial fibrillation (PAF) repeatedly developed. Pacemaker memory showed that the intrinsic atrioventricular (AV) (atrial pacing-ventricular sensing [Ap-Vs]) interval was paradoxically prolonged during rate-responsive atrial single-chamber (AAIR) mode rapid pacing because of MVP. Accordingly, to eliminate the paradoxical prolongation of the AV interval during rapid atrial pacing, we changed MVP to medium AV hysteresis and conducted DDDR mode pacing with rate-dependent AV delay. PAF then sharply decreased without antiarrhythmic drugs. ( 1-7) However, there are few detailed reports concerning the effective management of atrioventricular (AV) interval for suppression of PAF which develops after implantation of a DDD pacemaker (PM) with the current standard functions of rate-response and MVP.We implanted a DDD PM in an SSS patient and subsequently implemented the functions of rate-response and MVP at the same time. PAF then repeatedly developed after discharge. To suppress the PAF, we changed MVP to medium AV hysteresis and activated rate-dependent (Dynamic ® ) AV delay, while preserving the rate-response function. Thereafter, the repeated PAF sharply decreased without antiarrhythmic drugs or any additional therapy. We describe here the detailed clinical course of PAF, including PM memory, and assess the mechanism in this patient.
Case ReportA 68-year-old man had been previously diagnosed with hypertension, sleep apnea syndrome, cardiomegaly, and sinus bradycardia. At the end of June 2010, he experienced syncope for the first time, when long pauses occurred during Holter monitoring which was performed to examine sinus bradycardia. Holter recording showed the development of PAF and consecutive pauses of 5.5, 3.5, and 3.45 seconds on its termination. In early July, he was admitted to our hospital for PMI with the diagnosis of SSS. Examination findings on admission were as follows: sinus bradycardia was 41 beats per minute (bpm) and the PQ interval was 150 milliseconds (ms) on a 12-lead electrocardiogram (ECG); the cardiothoracic ratio was 57% on chest X-ray; left atrial dimension (LAD) was 57 mm, left ventricular diastolic dimension was 59 mm, left ventricular ejection faction was 75% on echocardiogram; and the serum B-type natriuretic peptide (BNP) level was 142.9 pg/mL.In the middle of July, a DDD-mode PM (Entovis DR-T, Biotronik, Berlin, Germany) with 180 ms of AV delay on 60 bpm of lower-rate pacing was implanted (Figure 1). Leads were placed in the right atrial appendage and ventricular apex. Rate-dependent (Dynamic) AV delay was started on the date of PMI, although the function was virtually invalid because of DDD-mode back-up pacing with 180 ms of AV delay ( Figure 1).From the