Characterization of Bradyarrhythmias Leading to Post–Heart Transplant Pacemaker Implantation: Sinus Node Dysfunction versus Atrioventricular Block

Objectives: After orthotopic heart transplantation bradyarrhythmia with pacemaker dependency can be caused by sinus node dysfunction (SND) or atrioventricular block (AVB). We aimed to characterize the differences between patients presenting with the individual etiologies and compare risk factors within the groups.

Methods: In this single-center retrospective study we collected data from 1179 heart transplants performed in our department from 1981 until 2016. We identified patients requiring permanent pacing and furthermore collected and analyzed data regarding risk factors as well as demographics to compare the SND and AVB group.

Results: Of all of our transplant patients 11.5% (135 patients) required permanent pacing. Of these 116 had developed SND while only 17 had developed AVB. The donor age in the AVB group was significantly higher (p = 0.031). Furthermore cardiopulmonary bypass time and aortic cross clamp time was higher in the AVB group compared with the SND group. The median time to pacemaker implantation was 26.5 days after transplant in the SND group and 805 days in the AVB group with over 80% of SND patients receiving pacemakers within 3 months and less than 50% of AVB patients developing the arrhythmia and receiving a pacemaker in the initial three months after heart transplant (p = 0.001).

Conclusion: In our investigation of heart transplant patients who developed SND and those who developed AVB we found that the two populations differ completely. SND is a more frequent and early presenting rhythm complication after heart transplantation. Waiting for resolution reduces permanent pacing rates. AVB develops late and is associated with longer bypass and cross clamp times. This understanding allows an improvement of risk factors and thus also a reduction of risk of bradyarrhythmia and pacemaker dependency after orthotopic heart transplantation.