Accurate Diagnosis of Atrioventricular Nodal Reentrant Tachycardia With Very Short His‐Atrial Interval and Earliest Activation in the Proximal Coronary Sinus

ABSTRACT Introduction Differential diagnoses in atrioventricular nodal reentrant tachycardia (AVNRT) with His‐atrial (HA) interval of < 70 ms and earliest atrial activation site (EAAS) in the proximal coronary sinus (pCS) include slow‐fast AVNRT with inferior deviation of the fast pathway (FP) and slow‐slow AVNRT with a lower common pathway (LCP). Therefore, we examined the electrophysiological and anatomical characteristics distinguishing slow‐fast AVNRT with inferior FP deviation from slow‐slow AVNRT with an LCP. Methods Analyzed were 32 AVNRTs with HA intervals of < 70 ms and EAAS in pCS. During ablation at the EAAS, patients with atrio‐His (AH) interval prolongation leading to abandonment ( n = 7) were classified as slow‐fast AVNRT phenotype, while those with successful ablation without AH prolongation ( n = 25) were classified as slow‐slow AVNRT phenotype. Results Triple antegrade AVN physiology, dual retrograde AVN physiology, and AH block during AVNRT were observed only in the slow‐slow AVNRT group. A ΔHA > 15 ms occurred more often in the slow‐slow AVNRT group (82% vs. 17%, p = 0.009). The AH VP ‐AH AVNRT —defined as the AH interval during right ventricular overdrive pacing minus that during AVNRT—was shorter in the slow‐slow AVNRT group (24 ± 24 vs. 1 ± 15 ms, p = 0.02). The His‐EAAS distance was shorter in the slow‐fast AVNRT group (7.3 ± 2.3 vs. 16.9 ± 4.9 mm, p < 0.001). Conclusion In cases of AVNRT with an HA interval < 70 ms and EAAS in the pCS, the slow‐slow AVNRT phenotype is more prevalent than the slow‐fast AVNRT phenotype. The shorter AH VP ‐AH AVNRT and the His‐EAAS distance may help differentiate them.