Gradual power titration using radiofrequency energy: a safe method for slow-pathway ablation in the setting of atrioventricular nodal re-entrant tachycardia.

AIMS: In the setting of atrioventricular nodal re-entrant tachycardia (AVNRT), radiofrequency (RF) catheter ablation of the slow-pathway (SP) ensures excellent outcome. However, the risk of complete heart block (CHB) remains real ( approximately 1%) and detrimental. This study reports on a gradual power titration approach using RF energy, which allows a significant decrease in CHB occurrence. METHODS AND RESULTS: Slow-pathway ablation was performed in 468 patients (mean age 43.8 +/- 17.2 years, 311 women). Initial settings were 5 W, 60 degrees C, 120 s (temperature-controlled mode). The power was increased by steps of 5 W for every 5 s until slow-accelerated junctional rhythm was obtained, and then further increased to 10 W maximum above this value. The acute success rate, the mean RF pulses applied per patient, and the average power delivered per successful RF applications were 99%, 3.2 +/- 1.1, and 31.7 +/- 3.0 W, respectively. There were nine (1.9%) transient and reversible AV blocks, and one (0.2%) permanent CHB only necessitating pacemaker insertion. The recurrence rate was 3.6% and the follow-up period was 28.1 +/- 14.1 months. CONCLUSION: Atrioventricular nodal re-entrant tachycardia RF ablation using gradual power titration is an efficient technique, capable of improving safety since it can decrease CHB occurrence.

Electrocardiographic predictors of Brugada type response during Na channel blockade challenge.

AIM: To identify ECG predictors of Brugada type response during Na channel blockade challenge. METHODS: We studied prospectively 103 patients (M = 76, 45 +/- 13 years) in whom ECGs were collected during ajmaline challenge. ECG recordings included the high right precordial leads (-2V(1) and -2V(2)). A positive response was defined by a >0.2 mV J point or ST segment elevation and a down-sloping pattern of the ST segment in at least one right precordial lead. RESULTS: Ajmaline challenge was positive in 48 (47%) of the 103 cases. Baseline J wave elevation was greater in -2V(1) (0.077 +/- 0.078 mV vs. 0.038 +/- 0.046 mV, P = 0.003) and -2V(2) (0.149 +/- 0.103 mV vs. 0.043 +/- 0.088 mV, P < 0.001) in cases with a subsequent positive response. In contrast, ST segment elevation and T wave amplitudes were reduced in V(1), V(2) and V(3). Logistic regression showed that J wave elevation in -2V(2) and decreased T wave amplitude in V(3) at baseline were independent predictors of a positive response. Baseline J wave elevation >0.16 mV in -2V(2) had a specificity of 100%, a sensitivity of 40%, a positive predictive value of 100% and a negative predictive value of 28%. CONCLUSION: J wave elevation >0.16 mV in -2V(2) was the strongest predictor of a Brugada type response to Na channel blockade challenge when Brugada syndrome was suspected on a baseline ECG.

Prevalence of drug-induced electrocardiographic pattern of the Brugada syndrome in a healthy population.

To determine the prevalence of drug-induced Brugada's syndrome (BrS) electrocardiograms (ECGs) in a healthy population, a sodium channel blockade challenge was performed in previously identified subjects with BrS-compatible (BrC) ECGs. These subjects were detected in 1,000 normal patients in whom first ECGs were systematically recorded. Because of the intermittent nature of electrocardiographic modifications in BrS, second ECGs were also recorded in a representative sample of the population presenting with first ECGs with normal results. The prevalence of typical drug-induced BrS ECGs was 5 of the 1,000 patients. This value was fivefold greater than the reported prevalence of spontaneous BrS ECGs in the healthy population.