Atrial fibrillation in the pacemaker clinic.

BACKGROUND Electrocardiographic (ECG) recognition of the underlying rhythm in patients with ventricular pacing can be difficult. Atrial fibrillation (AF) in particular may go unreported. OBJECTIVES To compare the underlying atrial rhythm determined in the pacemaker clinic with the 12-lead ECG interpretation of the atrial rhythm in those who were continuously paced in the ventricle. It was intended to determine whether long term anticoagulation therapy was related to whether AF was diagnosed before or after pacemaker implantation. METHODS Pacemaker clinic patients were enrolled if they had a 100% paced ventricular rhythm. The underlying rhythm was determined using pacemaker programming manoeuvres. A 12-lead ECG was recorded on all patients within 10 min of their pacemaker assessment and interpreted by one of the several geographic full-time cardiologists at the centre. All cardiologists were blinded to the results of pacemaker assessment and to the clinical history. RESULTS Fifty-six patients were enrolled. At the pacemaker clinic, 37 were determined to be in AF and three were in atrial flutter (AFL). Of these 40 patients with AF/AFL, 28 were correctly identified as such on the 12-lead ECG interpretation. Twelve of the 40 were interpreted only as having an 'electronic ventricular pacemaker' (EVP). Sixteen of the 40 patients (40.0%) with AF or AFL were not taking warfarin. Twenty-two of 25 patients with an AF/AFL diagnosis before pacemaker implantation were taking warfarin, compared with two of 15 patients with AF/AFL diagnosis after pacemaker implantation (P<0.0001). CONCLUSION These results show that the underlying rhythm in patients with ventricular pacing is frequently unrecognized by routine ECG interpretation. This may be of particular importance in the AF/AFL population as a potential contributor to the underuse of warfarin, especially when AF develops after pacemaker implantation. The pacemaker clinic may be in a position to play an important role in the identification of these patients.