Diagnostic value of stored electrograms in pacemaker patients.

OBJECTIVE: Stored electrograms (EGMs) are diagnostic tools in modern pacemakers, providing data concerning arrhythmia occurrence and device function. We sought to validate the impact of stored EGMs on diagnosis and verification of arrhythmias presented after pacemaker implantation. METHODS AND RESULTS: We enrolled 71 consecutive patients (mean age 64 +/- 8 years, 51 men) with a standard indication for pacemaker implantation. The following pacemaker devices were implanted: DDDR = 57, VDDR = 5, VVIR = 9. EGM triggers were atrial tachycardia (AT), non-sustained ventricular tachycardia (NSVT) and ventricular tachycardia (VT). We retrieved and analysed 362 EGMs at 3 and 6 months after implantation. The EGMs were triggered by AT in 260 EGMs (72%), by NSVT in 80 (22%) and by VT in 22 (6%). In total, 243 episodes (67%) confirmed the arrhythmic events, while 119 episodes (33%) were classified as false-positive. They were divided into false-positive AT in 85 EGMs (33%), false-positive NSVT in 28 (35%) and false-positive VT in 6 EGMs (27%). The false-positive AT cases were caused by ventricular far-field sensing from the atrial channel in 34 EGMs (40%) and noise or myopotentials in 51 EGMs (60%). Most of the false-positive VT and NSVT episodes were due to atrial fibrillation or atrial tachycardias in 21 EGMs (62%), while the rest were caused by noise in 11 EGMs (32%) or ventricular T wave oversensing in 2 EGMs (6%). CONCLUSIONS: Stored EGMs in pacemaker patients were diagnostic in two thirds of arrhythmic episodes. They are useful tools to diagnose arrhythmias and identify sensing problems, and they contribute to optimal device programming and patient management.

Ibutilide for the Cardioversion of Paroxysmal Atrial Fibrillation during Radiofrequency Ablation of Supraventricular Tachycardias.

Direct current electrical cardioversion (DC-ECV) is the preferred treatment for the termination of paroxysmal atrial fibrillation (AF) that occurs during radiofrequency ablation (RFA) of supraventricular tachycardias (SVT). Intravenous Ibutilide may be an alternative option in this setting. Thirty-four out of 386 patients who underwent SVT-RFA presented paroxysmal AF during the procedure and were randomized into receiving ibutilide or DC-ECV. Ibutilide infusion successfully cardioverted 16 out of 17 patients (94%) within 17.37 ± 7.87 min. DC-ECV was successful in all patients (100%) within 17.29 ± 3.04 min. Efficacy and total time to cardioversion did not differ between the study groups. No adverse events were observed. RFA was successfully performed in 16 patients (94%) in the ibutilide arm and in all patients (100%) in the DC-ECV arm, p = NS. In conclusion, ibutilide is a safe and effective alternative treatment for restoring sinus rhythm in cases of paroxysmal AF complicating SVT-RFA.

Inappropriate detection and therapy from an implantable cardioverter defibrillator due to atrial undersensing.

We present a case of inappropriate detection and therapy in a patient with an implantable cardioverter defibrillator. The device interpreted a supraventricular tachycardia as ventricular tachycardia due to unsensed P waves as a result of a relatively high level of atrial sensitivity setting. Subsequently, inappropriate therapy was delivered. The problem was resolved by decreasing the atrial sensitivity value.