Simultaneous dual fast and slow pathway conduction upon induction of typical atrioventricular nodal reentrant tachycardia: electrophysiologic characteristics in a series of patients.

INTRODUCTION: Simultaneous dual atrioventricular nodal conduction (SDNC) through slow (SP) and fast pathway (FP) is a rare phenomenon observed upon the induction of atrioventricular nodal reciprocating tachycardia (AVNRT). The aim of this study is to report the electrophysiological features of patients showing typical AVNRT induced through SDNC. METHODS AND RESULTS: Among 461 consecutive patients with typical AVNRT submitted to radiofrequency catheter ablation (RFCA), seven patients (1.5%) with SDNC at tachycardia onset (group I: 6 female; age 60-72 years, mean 65.2 +/- 3.8 years) and 118 age-matched controls (group II: 60 female; age 60-88 years, mean 68.4 +/- 6.8 years) were considered. Controls were further subdivided into two subgroups according to age: subgroup A (94 patients, age 60-75 years) and subgroup B (24 patients, age >75 years). The value of the following parameters was significantly higher in group I than in group II and in subgroup A: A-H interval [113 +/- 26 vs. 89 +/- 27 (P < 0.01) vs. 84 +/- 19 (P < 0.001)], ventriculoatrial conduction effective refractory period [355 +/- 85 vs. 293 +/- 87 (P < 0.05) vs. 281 +/- 82 (P < 0.05)], SP conduction time upon AVNRT induction [444 +/- 104 vs. 350 +/- 72 (P < 0.01); vs. 345 +/- 67 (P < 0.001)], AVNRT cycle length [484 +/- 103 vs. 396 +/- 71 ms (P < 0.05); vs. 384 +/- 69 (P < 0.05)], and rate of AVNRT induction from ventricle [71% vs. 10% (P = 0.001); vs. 6% (P = 0.001)]. Differences were mostly not significant between group I and subgroup B. SP location and RFCA success rate were similar in all groups. CONCLUSION: In a population of AVNRT patients, SDNC at AVNRT induction is infrequent and it prevails beyond the fifth decade of life and in females. SDNC is associated with peculiar AVN conduction features, which resemble the age-related modifications of AVN conduction.

Computerized high-density mapping of the pulmonary veins: new insights into their electrical activation in patients with atrial fibrillation.

AIM: To report the method and findings of computerized high-density mapping of pulmonary veins (PVs) in patients undergoing their electrical isolation for atrial fibrillation (AF). METHODS AND RESULTS: In 17 consecutive patients (8 M, age 55+/-11 years), a 64 electrode basket catheter was placed in the target PVs and 56 bipolar electrograms were recorded, analyzed and isochronal maps were generated. PVs were mapped during sinus rhythm, left-sided pacing and ectopic activity. The sites of earliest activation at the veno-atrial junction were defined as the atrium to vein conduction breakthroughs. PV activation pattern was classified as predominantly longitudinal or transverse, according to the direction of the impulse from the breakthroughs. The ectopic pattern was defined as multifocal, when distant areas in the PV had activation times within 10ms. Thirty-one PVs were mapped. The activation pattern was predominantly longitudinal in 13 PVs and transverse in 18 PVs. Two breakthroughs were identified in 22 PVs and three in nine. All the breakthroughs were evident simultaneously in sinus rhythm and left-sided pacing changed only the predominance of the breakthrough. Ectopies were mapped in 10 PVs: eight showed a multifocal and two a monofocal pattern; six ectopies originated from the proximal tract of the PV. CONCLUSION: High-density mapping of PV identifies a typical activation pattern. Multiple and discrete breakthroughs are simultaneously identified in sinus rhythm. The majority of the mapped ectopies has a multifocal pattern and proximal origin.