Characteristics of slow pathway conduction after successful AVNRT ablation.

BACKGROUND: AV node slow pathway conduction can persist following successful ablation for AV node reentrant tachycardia (AVNRT). We hypothesized that careful examination of AV nodal conduction curves before and after effective AVNRT ablation in patients with persistent slow pathway conduction could shed light on this apparent paradox. METHODS AND RESULTS: Thirty patients (age 40.9 +/- 14.3; 8 male) were included. AV node function curves were created based on pre- and postablation atrial extrastimulus testing. Analysis of slow pathway function curves demonstrated significant decrease in AH for any given coupling interval after ablation (mean difference -68.1 [-94.5, -41.7] P < 0.001), graphically indicated by downward displacement of the curve. In addition, mean slow pathway effective refractory period (ERP) increased from 247.9 +/- 36.1 msec to 288.6 +/- 56.0 msec (P < 0.001); mean maximum AH interval decreased from 361.3 +/- 114.2 msec to 306.9 +/- 65.2 msec (P = 0.013); mean difference in minimum and maximum AH interval during slow pathway conduction decreased (from 94.5 +/- 75.8 msec to 59.6 +/- 46.2 msec (P = 0.016). Finally, mean difference between the fast and slow pathway effective refractory periods, the span of coupling intervals over which slow pathway conduction occurred, decreased (from 113.9 +/- 61.4 msec to 63.2 +/- 41.5 msec, P = 0.001). CONCLUSIONS: Ablation, which successfully eliminates inducible and spontaneous AVNRT in the presence of persistent slow pathway conduction, is associated with significantly altered slow pathway conduction characteristics, indicating the presence of a damaged or different slow pathway after ablation, incapable of sustaining tachycardia.

Esophageal temperature monitoring during radiofrequency ablation of atrial fibrillation.

INTRODUCTION: Ablative strategies for atrial fibrillation have centered on the left atrium, in particular the pulmonary veins. An emphasis on ablating outside the ostia of the pulmonary veins appears to have reduced the risk of pulmonary vein stenosis. Unfortunately, ablation in the posterior left atrium has been reported to result in fatal atrio-esophageal fistula. METHODS AND RESULTS: We monitored esophageal temperatures in 16 consecutive patients undergoing atrial fibrillation ablation. There were 14 men and 2 women; average age 54.7 +/- 10.6 years. Eight patients had a lasso-guided pulmonary isolation procedure, eight an electroanatomically guided left-atrial circumferential approach. A commercially available esophageal temperature probe (Mallinckrodt Mon-a-therm 12F Esophageal Stethoscope with Temperature Sensor, Thermistor 400 Series) was positioned under general anesthesia. Temperature changes were noted and related to the relative location of the ablation catheter and the temperature probe during the temperature change. The esophagus was midline in three, right sided in three, and left sided in the remaining patients. Temperature rises could be recorded at the posterior aspect of any pulmonary vein. Detailed analysis of six patient maps revealed heating occurred with lesions created within 1 cm of the esophagus. CONCLUSION: The location of the esophagus relative to the back of the left atrium displays considerable variability. It is rarely midline and most often lies in close proximity to the left-sided veins. Ablation in close radiographic proximity (approximately 1 cm) to the esophagus as defined by a radio-opaque temperature probe can result in heating at the esophageal lumen.

An unusual accessory pathway: anteroseptal to ventricular outflow region connection.

Accessory pathways are typically located along the left or right atrioventricular junction. Distinct ventricular pre-excitation patterns determined by surface electrocardiography can provide reasonable pathway localization prior to invasive mapping and catheter ablation. We report an accessory pathway producing an unusual electrocardiographic appearance suggestive of ventricular outflow region pre-excitation. Pacing maneuvers and standard intracardiac recordings confirmed an atrial insertion immediately adjacent to the atrioventricular (AV) node and supported a ventricular insertion at the outflow tract region well away from the AV junction. The elimination of pathway conduction was achieved with radiofrequency (RF) energy at the atrial insertion after successful ice mapping excluded AV block at the target site. This is the second such pathway observed at our institution over a 20-year period.