Effects of Radiofrequency Catheter Ablation on Patients with Permanent Pacemakers

The objective of this study was to assess the effects ofradiofrequency energy application on implanted pacemaker functions.Radiofrequency (RF) catheter ablation may cause pacemaker dysfunction dueto electromagnetic interferences. The effects of RF on pacemaker behaviorwere studied in a series of 38 pacemakers, implanted 18 ± 26 monthsprior to a RF procedure using either a right ventricular approach (AV nodeablation, n = 35) or a left ventricular approach (left concealedaccessory pathway ablation, n = 1; VT ablation, n = 2). The38 patients (mean age 65 ± 9 years) included 20 men and 18 women.Before energy applications, the 23 different pacemaker models wereprogrammed to the VVI mode at the lowest available rate. The continuoussurface ECG was recorded throughout the procedure. Thorough testing of thedevices was performed before and after each RF delivery. Unusual pacemakerresponses occurred in 20 of the 38 cases studied (53%). The impactof RF delivery was unpredictable, and variable dysfunctions were observedat different times for a given patient or could vary for a given model.Unusual pacemaker responses included pacemaker inhibition (n = 8), untoggled backup mode (n = 3), electromagnetic interference noisemode (n = 3), temporary RF-induced pacemaker tachycardia (n =2), erratic behavior (n = 1), oversensing of RF onset and offset (n= 8), and transient loss of ventricular capture, (n = 1).Postablation, most devices automatically toggled back to fullfunctionality. The three devices in the untoggled backup mode had to bereprogrammed to obtain normal operations. At the end of the procedure,pacing thresholds remained unchanged in all but one patient, in whom theincrease in ventricular threshold was due to a nicked lead. In conclusion,implanted pacemakers frequently exhibit transient, unpredictable responsesto RF energy application. Although all pacemaker functions were restored postablation, some devices had to be reset manually. The anomalies observedduring the RF application argue for the simultaneous use of an externalpacemaker in pacing-dependent patients.