BACKGROUND: Dual atrioventricular (AV) nodal physiology is a substrate for the development of AV nodal reentrant tachycardia (AVNRT). The purpose of this study was to investigate the individual role of slow pathway (SP) and fast pathway (FP) refractoriness in AVNRT.METHODS: 1515 patients who had dual AV nodal physiology among 2732 undergoing EPS for PSVT were retrospectively reviewed. PES was performed to induce tachycardia in all patients. The patients were divided into 1) group A (N=1287), the patients with inducible AVNRT;2) group B (N=44), the patients with clinical AVNRT documented by ECG but not inducible(no accessory pathways, no atrial flutter/atrial tachycardia);3) group C (N=184), the patients with the dual AV node pathways but without clinical or inducible. In group C, any tachycardia did not develop after ablation during a follow-up 9.5 ± 6.2 years.RESULTS: Compared to group B, group A was long effective refractory period (ERP) of FP (365 ± 79 vs. 324 ± 58ms, p=0.009), increased [Delta]ERP of SP and FP (83 ± 64 vs. 45 ± 28 ms, p=0.006), and short VA block CL (369 ± 95 vs. 416 ± 107 ms, p=0.004). However, there was no difference in age, gender, heart rate, TCL, AVBCL, FP ERP, atrial and ventricular ERP, and VA dissociation between group A and B (all p >0.05). By multiple logistic regression, [Delta]ERP (OR=1.02, 95% CI 1.003-1.032, p=0.015) and VABCL (OR=0.996, 95% CI 0.992-1.000, p=0.04) were independent predictors of inducible AVNRT. Compared to group A, group C was young (38 ± 15 vs. 46 ± 16 years, p<10-6), more male (55 vs.37%, p<10-5), long SP ERP (309 ± 55 ms vs. 285 ± 45 ms, p<10-7), and decreased ΔERP (54 ± 42 vs. 83 ± 64 ms, p<10-6). By multiple logistic regression, SP ERP (OR 1.01, 95% CI 0.896-0.999, p=0.021) was an independent predictor of no AVNRT. CONCLUSIONS: This study suggests the FP refractoriness may have a direct effect to induce AVNRT by increasing the refractoriness heterogeneity of dual pathway, whereas SP refractoriness might plays a role as predisposing factor of the development of AVNRT.
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