Slow Atrioventricular Nodal Reentrant Arrhythmias: Clinical Recognition, Electrophysiological Characteristics, and Response to Radiofrequency Ablation

BACKGROUND: Atrioventricular nodal reentrant tachycardia (AVNRT) is a common form of supraventricular tachycardia (SVT). Rarely, patients may present with an unusual form of atrioventricular nodal reentrant arrhythmia (AVNRA) with a cycle length greater than 600 ms. We describe the clinical presentation, electrophysiology characteristics, and response to radiofrequency ablation in a group of patients with AVNRA. METHODS AND RESULTS: Six patients with slow documented sustained supraventricular arrhythmias at rates <100 bpm underwent electrophysiology study. Baseline clinical and electrophysiologic characteristics were: mean age 77 +/- 5 years; left ventricular ejection fraction 51 +/- 10%; hypertension 66%; diabetes mellitus 33%; coronary artery disease 33%; sinus cycle length 874 +/- 110 ms; PR 261 +/- 54 ms; atrial to His (AH) 181 +/- 49 ms. AVNRA was diagnosed based on previously described criteria for AVNRT. Mean tachycardia cycle length (TCL) during AVNRA was 668 +/- 74 ms. The AH and His to atrial (HA) intervals during the AVNRA was 434 +/- 50 and 234 +/- 81 ms, respectively. Two patients had slow-fast AVNRA while the others had slow-slow AVNRA. Most common symptoms reported during AVNRA were shortness of breath, fullness in the throat, chest tightness, dizziness, near-syncope, and syncope. Radiofrequency catheter ablation (RFCA) of the slow pathway was performed successfully in five of six patients. Post-ablation AV nodal Wenckebach occurred at 666 +/- 49 ms compared with 521 +/- 91 ms at baseline. CONCLUSION: AVNRA may occur at rates less than 100 bpm in the elderly and may be misdiagnosed as junctional rhythm. Slow AVNRA can cause significant symptoms. Slow pathway ablation can be successfully performed in AVNRA.