Incidence of complete atrioventricular block following attempted radiofrequency catheter modification of the atrioventricular node in 880 patients: Results of the Multicenter European Radiofrequency Survey (MERFS)

UNLABELLED: The Multicenter European Radiofrequency Survey (MERFS) retrospectively analysed the incidence of procedure-related complications in 4463 patients who had undergone radiofrequency catheter ablation in 69 European institutions between 1987 and 1992. Of these 4463 patients, 880 underwent modification of the atrioventricular node to cure atrioventricular nodal reentrant tachycardia. This report presents a detailed analysis of the incidence of complete atrioventricular block with respect to the target site and the number of patients reported per institution. The most common complication of modification of the atrioventricular node was the unintended induction of complete atrioventricular block (41 of 880 patients, 4.7%). In 684 of 880 patients (78%), detailed information about the approached target site for modification of the atrioventricular node was available. Complete atrioventricular block occurred significantly more often in patients who underwent ablation of the fast pathway (19/361, 5.3%) or in whom ablation of the slow and fast pathway was attempted after failure at the initial site (4/25, 16%) than in patients who underwent slow pathway ablation (6/298, 2.0%, P < 0.05). The overall incidence of complete atrioventricular block was significantly higher (6.3%) in centres with limited experience in radiofrequency modification of the atrioventricular node ( < or = 30 patients treated; group I: n = 526) compared to centres that had treated > 30 patients (group II: n = 354; 2.3%; P < 0.05). In addition, in those patients in whom the target site was available, the incidence of complete atrioventricular block after fast pathway ablation was significantly higher in group I (n = 168 patients) when compared to group II (n = 193 patients) (7.7% vs 3.1%, P < 0.05) and also tended to be higher after slow pathway ablation in group I (2.4% in group I vs 1.5% in group II; P = ns). CONCLUSIONS: In this analysis of collaborative data, radiofrequency catheter modification of the atrioventricular node carried a risk of approximately 5% of complete atrioventricular block. The incidence of complete atrioventricular block was significantly higher in patients who underwent fast pathway ablation or fast and slow pathway ablation after failure at the initial site compared with slow pathway ablation. In addition, the results indicate that there is a learning curve, regarding the incidence of complete atrioventricular block, which is a significant complication of the procedure, when modifying the atrioventricular node. Thus, caution is recommended when performing radiofrequency modification of the atrioventricular node using the so-called anterior approach to abolish fast pathway conduction, especially when the experience of the institution or investigator/s is limited.