Electrocardiographic characteristics in low atrial septum pacing

Patient with sick sinus syndrome and implanted dual-chamber pacemaker with reduced P-wave duration following low interatrial septal pacing: Case report

INTRODUCTION

A dual-chamber pacemaker (DDD/R) for a sinus node disease is sometimes referred to as a physiological pacemaker as it maintains atrioventricular synchrony, however several clinical trials have proved its inferiority to a nonphysiological single-chamber ventricular back-up pacing.

PATIENT CONCERNS

A subject of the study is a 74-year-old woman with a sick sinus syndrome (SSS) and a previously implanted physiological DDD/R pacemaker. The SSS was diagnosed because of patient's very slow sinus rhythm of about 36 bpm, and due to several episodes of dizziness. After the DDD/R implantation the percentage of atrial pacing approached 100%, with almost none ventricular pacing.

DIAGNOSES

Sick sinus syndrome, complete Bachmann's bundle block, atrial fibrillation, atrial flutter.

INTERVENTIONS

The patient was previously implanted with a physiological DDD/R pacemaker. Several years after the implantation, the atrial fibrillation was diagnosed and the pulmonary vein isolation was then performed by cryoablation. During the follow-up after pulmonary vein isolation, the improvement of mitral filling parameters was assessed using echocardiography. Shortly thereafter the patient developed the persistent paroxysm of a typical atrial flutter which was successfully terminated using a radiofrequency ablation. No recurrence thereof has been observed ever since (24 months).

OUTCOMES

The atrial electrode of the pacing system was implanted within the low interatrial septal region that resulted in a reduced P-wave duration compared to native sinus rhythm P-waves. The said morphology was deformed because of the complete Bachmann bundle block. That approach, despite a nonphysiological direction of an atrial activation, yielded relatively short P-waves (paced P-wave: 179 ms vs intrinsic sinus P-wave: 237 ms). It also contributed to a significantly shorter PR interval (paced PR: 204 ms vs sinus rhythm PR: 254 ms).

CONCLUSIONS

The authors took into consideration different aspects of alternative right atrial pacing sites. This report has shown that in some patients with a sinus node disease, low interatrial septal pacing can reduce the P-wave duration but does not prevent from the development of atrial arrhythmias.

Verification of pacemaker automatic mode switching for the detection of atrial fibrillation and atrial tachycardia with Holter recording

AIMS

Verification of the accuracy of onset, offset, and duration of automatic mode switching (AMS) of pacemakers compared with onset and end of atrial fibrillation (AF) or atrial tachycardia (AT). Correct pacemaker diagnosis of atrial tachyarrhythmias (AA) is indispensable for reliable automatic prevention and intervention algorithms of AA.

METHODS AND RESULTS

Comparison was made of the AMS registration of the pacemaker-stored electrograms (EGMs) and the number and cumulative duration of these episodes with continuous 7-day Holter monitoring. Atrial sensitivity was kept at 0.5 mV and far field R-wave recognition in the atrial channel was excluded by blanking of this signal. Lead types were confined to leads with short-ring tip spacing (10-13.8 mm). During Holter monitoring, 18 of 57 included patients with standard reason for pacemaker implantation showed episodes of AF or AT. Cumulative duration of AF and AT from Holter was correctly interpreted by the pacemaker in 99.9% of the patients. All episodes of AF, as seen on the Holter recording, were recognized by the pacemaker (correlation 99.9%). During AF, multiple episodes of undersensing were detected. The number of AMS episodes was influenced by undersensing during AF. The influence of these short episodes of undersensing on the total duration of AF was trivial (cumulative duration of AF was 99.9% correct). In patients with AT without AF on Holter (n=7) and in contrast to the AF episodes, the cumulative AT duration did not correlate well (63%) with the Holter recordings. The number of AMS episodes in the setting of AT was influenced by the atrial tachycardia detection rate setting and the duration of the post-ventricular atrial blanking interval.

CONCLUSION

The total duration of AF is correctly represented by the total duration of AMS and can be considered a reliable measure of total AF duration. AT duration was poorly correlated with AMS duration. The number of mode switches does not reflect the number of episodes of AF/AT. Increased memory capacity allowing the storing of all EGMs triggered by the initiation of AF/AT would be the ideal setting with which to optimize the diagnostic performance of pacemakers.