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)

The Multicenter European Radiofrequency Survey (MERFS) retrospectivelyanalysed the incidence of procedurerelated complications in4463 patients who had undergone radiofrequency catheter ablationin 69 European institutions between 1987 and 1992. Of these4463 patients, 880 underwent modification of the atrioventricularnode to cure atrioventricular nodal reentrant tachycardia. Thisreport presents a detailed analysis of the incidence of completeatrioventricular block with respect to the target site and thenumber of patients reported per institution. The most common complication of modification of the atrioventricularnode was the unintended induction of complete atrioventricularblock (41 of 880 patients, 4.7%). In 684 of 880 patients (78%),detailed information about the approached target site for modificationof the atrioventricular node was available. Complete atrioventricularblock occurred significantly more often in patients who underwent ablation of the fast pathway (19/361, 5 3%)or in whom ablationof the slow and fast pathway was attempted after failure atthe initial site (4/25, 16%) than in patients who underwentslow pathway ablation (6/298, 20%, P<0.05). The overall incidenceof complete atrioventricular block was significantly higher(6.3%) in centres with limited experience in radiofrequencymodification of the atrioventricular node (30 patients treated;group I: n=526) compared to centres that had treated >30patients (group TI: n=354; 2.3% P<0.05). In addition, inthose patients in whom the target site was available, the incidenceof complete atrioventricular block after fast pathway ablationwas significantly higher in group I (n= 168 patients) when comparedto group II (n=193 patients) (7.7% vs 3.1%, P<0.05) and alsotended 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 cathetermodification of the atrioventricular node carried a risk ofapproximately 5% of complete atrioventricular block. The incidenceof complete atrioventricular block was significantly higherin patients who underwent fast pathway ablation or fast andslow pathway ablation after failure at the initial site comparedwith slow pathway ablation. In addition, the results indicatethat there is a learning curve, regarding the incidence of completeatrioventricular block, which is a significant complicationof the procedure, when modifying the atrioventricular node.Thus, caution is recommended when performing radiofrequencymodification of the atrioventricular node using the so-calledanterior approach to abolish fast pathway conduction, especiallywhen the experience of the institution or investigator/s islimited. (Eur Heart J 1996; 17: 82–88)