br Methods The study population
Methods The study population comprised 150 patients who underwent implantations of Medtronic dual chamber pacemakers and who had maintained both atrial and ventricular sensing (either in DDD, DDI, or VDD modes) from March 2008 to October 2010. The implanted mek162 generators were either Kappa series (n=80), EnPulse series (n=17), or ADAPTA series (n=53). At the subjects\' first visit to the pacemaker clinic after enrollment in this study, the settings of the parameters for storing intracardiac EGMs were chosen; the detection rates for atrial high-rate (AHR) episodes and ventricular high-rate (VHR) episodes were set at 170bpm and 180bpm, respectively. The supraventricular tachycardia filter was set to the “on” position so that fulfillment of both AHR and VHR excluded the diagnosis of a VHR episode. AHR and VHR episodes were selected as the types of high-rate types of episodes to be saved. “Include” was chosen for refractory senses so that atrial sensing was included in tachyarrhythmia diagnosis even if that sensing was within the refractory period. “Summed” was chosen as the EGM type to be saved; this meant that the SEGM, which is the merged AEGM and VEGM, was selected as the intracardiac EGM to be saved. The time out was set at 12 weeks (that is, EGMs were saved for 12 weeks after being recorded, and after that period, the EGMs would be deleted and only the tachycardia log would be preserved). The EGM allocation was set at 4 for 4/4s; thus EGMs of 4 episodes were saved including 4-s recordings of the EGMs before and after detection of each high-rate episode. During the follow-up period, the SEGM was analyzed manually for instances in which AHR or VHR episodes were detected in stored EGMs. When the automated diagnosis was different from that obtained by manual analysis, the episodes were categorized into 4 groups. When the atrial potential was located within the PVAB period during detected tachycardia episodes, the PVAB was set to the minimum value; this prevented FFRW over-sensing while maintaining conditions for maximum atrial sensing and full capture of ventricular pacing..
Results During the follow-up period of 20±4 months (range, 9–30 months), AHR or VHR episodes were detected with saved EGMs in 115/130 patients (88%) when the SEGM channel was selected. In 43/115 patients (37%) with tachycardia detections, the automated diagnosis result (AHR or VHR episode) was doubtful or discordant with the manual analysis of the EGM. Among those 43 patients, there were 12 type 1 cases, 5 type 2 cases, 9 type 3 cases, and 9 type 4 cases. In type 1 patients, fusing of atrial and ventricular potentials became more prominent after changing to the AEGM. Atrial potentials without markers within the PVAB period also became more prominent (Fig. 1B). For the type 2 patients, AEGM selection meant that atrial potentials manifested more prominently within the PVAB and the automated tachycardia diagnosis changed from VHR to AHR in the same patient after PVAB adjustment (Fig. 2B). However, in a case of atrial tachycardia and impaired atrioventricular conduction properties, adjustment of the PVAB to the minimum possible value (110 or 130ms) still led to an incorrect automated VHR diagnosis (Fig. 5). In type 3, the atrial potentials were not discernible or were fused with the ventricular potentials in the SEGM (Fig. 3A). Selection of the AEGM channel made the atrial potentials more prominent, and the ventricular potentials were confirmed as FFRWs with a constant short cycle length resulting in the diagnosis of ventricular tachycardia (Fig. 3B). In type 4, tiny irregular atrial signals fused with the QRS complex or T wave in the SEGM were suspected; however, the details were unknown (Fig. 4A). With AEGM selection, any over-sensing of noisy signals could be clearly differentiated from atrial potentials (Fig. 4B). A follow-up with a change in EGM selection from the AEGM to the VEGM was then performed only in types 1 and 2, because follow-up with VEGM was considered to be of no use for tachycardia discrimination in type 3.