Slow AV nodal pathway ablation utilizing a unique temperature controlled radiofrequency energy system

Optimal target temperature for slow pathway ablation in patients with atrioventricular nodal reentrant tachycardia

OBJECTIVE

To define optimal target temperature for the slow pathway ablation.

MATERIALS AND METHODS

In this study, 268 patients with atrioventricular nodal reentrant tachycardia (190 females; mean age, 49 +/- 14 years) who underwent slow pathway ablation using a combined electroanatomic approach were enrolled. The patients were categorized into Group 1 if target temperature was < 55 degrees C or into Group 2 if target temperature was > or = 55 degrees C. Group 2 was divided into three subgroups of 55 degrees C (Sgp-1), 60 degrees C (Sgp-2), and 65 degrees C (Sgp-3).

RESULTS

Acute success rate was similar in both groups (P = 0.83). The ablation time (26.2 +/- 20 vs. 36.5 +/- 28 min; P = 0.014), fluoroscopy time (11.6 +/- 9.7 vs. 17.8 +/- 16.6 min; P = 0.035), and number of applications (4.1 +/- 3.2 vs. 9.1 +/- 6.5; P = 0.02) were lower for Group 2 than Group 1 patients. The frequency of AV or VA block, impedance rise, and coagulum formation were comparable in two groups (all P > 0.05). During mean follow-up of 14 +/- 3 months, recurrence of the arrhythmia was seen in higher proportion of Group 1 than Group 2 patients (P = 0.036). Among the Group 2 patients, there were no significant differences between the three subgroups in terms of acute success rate, fluoroscopy time, risks of AV and VA block, pericardial effusion, and recurrence (All P > 0.05). Number of applications and RF pulse duration were lower in Sgp-2 and 3 compared to Sgp-1 (All P > 0.05). Impedance rise and coagulum formation were slightly higher in Sgp-3 compared to Sgp-1 and 2 but this difference did not reach statistical significance (All P > 0.05).

CONCLUSIONS

Compared to less than 55 degrees C, target temperatures > or = 55 degrees C during slow pathway ablation significantly reduces fluoroscopy time, RF pulse duration, number of RF applications, and recurrence of AVNRT without increase in risk of AV or VA block or coagulum formation.

Low temperature and low energy radiofrequency modification of atrioventricular nodal slow pathways in pediatric patients

OBJECTIVES

To report our experience using low temperature and energy in the modification of the slow pathway in pediatric patients with atrioventricular nodal reentrant tachycardia.

BACKGROUND

A concern in performing a slow pathway modification is the possible damage of the normal AV conduction system. Lesion size has been shown to have a linear relationship with temperature. Previous reports have used energy of 25-50 W that generate temperatures of 60 degrees C -70 degrees C for successful procedures.

METHODS

Report of results of attempted AV nodal slow pathway modification in 17 consecutive pediatric patients < 15 years of age at The Children's Hospital of Philadelphia from April 1995 to November 1997 using low temperature and energy.

RESULTS

There were 18 successful slow pathway modifications with 1 recurrence in 17 patients. The maximum energy used during successful lesions was 32.7 +/- 13.8 W (range 15-50 W) with a mean energy of 26.4 +/- 13.3 W (range 12-48 W). The peak temperature during these lesions was 55.1 degrees C +/- 4.1 degrees C (range 48 degrees C-64 degrees C) with a mean temperature of 47.9 degrees C +/- 2.7 degrees C (range 44 C-540C). The mean number of radiofrequency lesions required for a successful modification was 5.8 +/- 6.7 (median 4.0, range 1-26). Patients have been followed for 2.08 +/- 0.79 years.

CONCLUSIONS

Slow pathway modification can be performed successfully with a low incidence of recurrence in the pediatric patient using low energy and temperature. It is possible that this may lead to smaller lesions.

The response of the slow atrioventricular nodal pathway to temperature

The present study attempted to determine the lowest temperature at which the slow atrioventricular nodal pathway responds to heating and the temperature necessary for successful ablation of the slow pathway in patients with atrioventricular nodal reentrant tachycardia (AVNRT). The study group comprised 23 consecutive patients (14 women, 9 men) with symptomatic AVNRT. Radiofrequency current was delivered at the slow pathway potential recording site using a HAT 200S catheter ablation system. Successful radiofrequency ablation of the slow pathway was achieved in all 23 patients. Junctional beats, suggesting the response of the slow pathway to temperature, were detected in 62 of the total 136 applications. The temperature measured at the first junctional beat was 45.4+/-4.2 degrees C. The maximum temperature required for the successful ablation of AVNRT ranged from 45 to 88 degrees C. There were no complications except for 1 patient with transient atrioventricular (AV) block. There were no recurrences of AVNRT during follow-up. The lowest temperature at which the slow pathway was responsive to heat was quite similar to that for accessory pathways or the AV junction. However, the temperature required for the successful ablation of AVNRT differed markedly among the patients.

Comparison of power- and temperature-guided radiofrequency modification of the atrioventricular node. Polaris Investigator Group

The purpose of this study was to compare the performance and clinical outcome of radiofrequency ablation of the substrate of atrioventricular (AV) nodal reentrant tachycardia (AVNRT) when guided by power output or temperature monitoring. Two sequential multicenter studies of power-controlled and open-loop, temperature-controlled radiofrequency ablation were analyzed in 171 patients undergoing AV node modification for the treatment of AVNRT. After successful ablation of AVNRT, complete elimination of slow AV node pathway function was accomplished more often with than without temperature monitoring (92% vs 69%, p = 0.005). Greater power was delivered to each patient with than without temperature monitoring (median 47 W, range 10 to 57, vs median 35 W, range 5 to 68, p = 0.001). Acute elimination of tachycardia (100% vs 96%), 3-month recurrence (6% vs 8%), procedural times (162 vs 170 minutes), fluoroscopy times (24.6 vs 29.5 minutes), complications (6% vs 3%), and catheter removals to check for coagulum (8% vs 6%) did not differ between patients treated with and without temperature monitoring, respectively. Power- and temperature-controlled radiofrequency techniques are highly successful with low complication rates for slow pathway ablation. Temperature monitoring may allow the safe delivery of more power, and the more complete elimination of slow AV node pathway function.