Background: Arrhythmias in elderly patients (> 65 years) are common. In this subset of patients, atrial fibrillation is by far the most frequent sustained arrhythmia but not the only one. Clinical, ECG and electrophysiological (EP) features of AV-nodal reentrant tachycardia (AVNRT) have rarely been described in the elderly, and this represents the aim of the current study.

Methods: At 2 EP-centres in Germany, data from all patients undergoing an EP-study (EPS) and diagnosed with AVNRT between January 2018 and May 2021 were collected and analysed. Patients older than 65 years constituted the study population.

Results: During the study period AVNRT was diagnosed in a total of 329 patients. 93 patients (28%) were older than 65 years and represent the study population [median age 74 (65-89) years, 48% female]. In the majority (85%), the duration of symptoms was short (< 1 year), 14 patients had symptoms of paroxysmal tachycardia for longer than 10 years. Most of the patients (n=88, 94%) had at least one ECG-documentation of the tachycardia. In sinus rhythm, the PR interval was relatively long [median 180 (120-380) ms)]. In 84% of patients, sustained AVNRT [median cycle length (CL) 400 (270-800) ms] was induced during EPS. In the remaining patients, at least 2 typical AV-nodal-echo beats were induced. Slow pathway (SP) ablation/modification was performed in all but one patient presenting with a very long baseline PR-interval, low antegrade Wenckebach-point (WP) and very slow AVNRT. In this case, the patient was treated with ß-blocker after pacemaker (PM) implantation. In 3 additional patients, PM implantation was necessary after ablation due to intermittent high-degree AV-block. In comparison to the rest of the study population, these four patients had a longer baseline PQ interval [median 275 (IQR 248- 303) ms vs. 180 (IQR 160- 192) ms], a longer baseline AH interval [median 207ms (IQR 185- 234) ms vs. 95 (IQR 80- 107) ms], a lower baseline antegrade WP CL [median 510 (IQR  435- 645) vs. 390ms (IQR 355- 470) ms], and a longer tachycardia CL [TCL 557 (IQR 454- 661) ms vs. 400 (IQR 364- 443) ms; p value <0,01 for all comparisons]. The overall complication rate (other than AV block) was low (2 patients with AV fistula treated conservatively) and comparable to the one described in younger patients. 

Discussion: Elderly patients also have AVNRT, there are a slight differences in physiology (i.e. relatively long baseline PR-interval and TCL, likely due to changes of the conduction system with aging), and as in young patients, ablation is curative treatment with similar (low) complication rate. A subset of patients, characterized by longer PR- and AH-intervals, lower WP and longer TCL may be at higher risk for AV-block after SP modification. Whether this is due to pre-existing damage or to posterior location of the fast pathway (FP) remains unknown.

Conclusion: SP ablation is safe and effective even in elderly patients. In patients presenting with EP characteristics presumptive of a baseline impairment of the conduction properties of the FP, ablation of the FP could be attempted to avoid postprocedural high degree AV block.