Do European GSM Mobile Cellular Phones Pose a Potential Risk to Pacemaker Patients?

BARBARO, V., et al .: Do European GSM Mobile Cellular Phones Pose a Potential Risk to Pacemaker Patients? A series of in vivo trials were carried out in order to verify whether the electromagnetic field radiated by GSM (Groupe Systemes Mobiles) mobile cellular phones might affect implanted pacemakers. Two European GSM phones of 2-watt power were tested and trials conducted on 101 pacemaker implanted outpatients attending day hospital for routine check-up, who volunteered for trials. Forty-three pacemaker models from 11 manufacturers were tested in all. When the sensing threshold of the pacemakers was set at a minimum and the antenna of the phone was in direct contact with the patient's chest, interference was detected for 26 implanted pacemakers. Specifically, pulse inhibition in 10 of 101 cases, ventricular triggering in 9 of 46 DDD-VDD pacemakers, and asynchronous pacing in 4 of 52 devices. Pulse inhibition was also observed combined with asynchronous pacing in 1 of 52 cases and with ventricular triggering in 2 of 46 cases. Minimum effect duration was ca. 3 seconds but in 6 cases effects continued as long as the interfering GSM signal was on. No permanent malfunctioning or changes in the programmed parameters were detected. Whenever interference was detected, trials were repeated to determine the maximum sensing threshold at which interference persisted (with the antenna in contact with the skin over the pacemaker). Then maximum distance between antenna and pacemaker at which interference occurred was determined at pacemaker maximum and minimum sensing threshold. Under our experimental conditions electromagnetic interference effects were detected at a maximum distance of 10 cm with the pacemaker programmed at its minimum sensing threshold. When the phone antenna was in direct contact with patient's skin over the implant, electromagnetic interference effects occurred at maximum ventricular and atrial sensing thresholds of 4 mV and 2.5 mV, respectively.     

Optimization of Pacing Algorithms to Prevent and Treat Supraventricular Tachyarrhythmias

Preventive atrial pacing and antitachycardia pacing have been proposed for the treatment of atrial fibrillation and associated arrhythmias in patients with indications for device implantation. Preventive algorithms provide overdrive atrial pacing, reduction of atrial premature beats, and prevent short-long atrial cycles with good patient tolerance. However, clinical trials testing preventive algorithms have shown contradictory results, possibly because of different trial designs, end points and patient populations. Factors probably responsible for neutral results include an already high atrial pacing percentage with the conventional DDDR mode, suboptimal atrial pacing site, and the deleterious effects of high percentages of right ventricular apical pacing. Atrial antitachycardia pacing therapies are effective in treating organized atrial tachyarrhythmias (that precede atrial fibrillation), mainly when delivered early after the onset particularly if the tachycardia is relatively slow. Antitachycardia pacing therapies might influence atrial fibrillation burden, but clinical studies have shown conflicting results about this issue. Consistent monitoring of atrial and ventricular rhythm including progression to persistent forms of atrial arrhythmias, variability of atrial arrhythmia recurrence patterns and onset mechanisms as well as antitachycardia pacing efficacy should be recorded in the stored device memory and used for optimal individual programming of these new functions.     

A Short‐Term,Randomized, Double‐Blind,Parallel‐Group Study to Evaluate the Efficacy and Safety of Dronedarone versus Amiodarone in Patients with Persistent Atrial Fibrillation: The DIONYSOS Study

Dronedarone versus Amiodarone in Patients with AF. Introduction: We compared the efficacy and safety of amiodarone and dronedarone in patients with persistent atrial fibrillation (AF). Methods: Five hundred and four amiodarone‐naïve patients were randomized to receive dronedarone 400 mg bid (n = 249) or amiodarone 600 mg qd for 28 days then 200 mg qd (n = 255) for at least 6 months. Primary composite endpoint was recurrence of AF (including unsuccessful electrical cardioversion, no spontaneous conversion and no electrical cardioversion) or premature study discontinuation. Main safety endpoint (MSE) was occurrence of thyroid‐, hepatic‐, pulmonary‐, neurologic‐, skin‐, eye‐, or gastrointestinal‐specific events, or premature study drug discontinuation following an adverse event. Results: Median treatment duration was 7 months. The primary composite endpoint was 75.1 and 58.8% with dronedarone and amiodarone, respectively, at 12 months (hazard ratio [HR] 1.59; 95% confidence interval [CI] 1.28–1.98; P < 0.0001), mainly driven by AF recurrence with dronedarone compared with amiodarone (63.5 vs 42.0%). AF recurrence after successful cardioversion was 36.5 and 24.3% with dronedarone and amiodarone, respectively. Premature drug discontinuation tended to be less frequent with dronedarone (10.4 vs 13.3%). MSE was 39.3 and 44.5% with dronedarone and amiodarone, respectively, at 12 months (HR = 0.80; 95% CI 0.60–1.07; P = 0.129), and mainly driven by fewer thyroid, neurologic, skin, and ocular events in the dronedarone group. Conclusion: In this short‐term study, dronedarone was less effective than amiodarone in decreasing AF recurrence, but had a better safety profile, specifically with regard to thyroid and neurologic events and a lack of interaction with oral anticoagulants. (J Cardiovasc Electrophysiol, Vol. 21, pp. 597‐605, June 2010)     

Evaluating MRI‐Compatible Pacemakers: Patient Data Now Paves the Way to Widespread Clinical Application?

The worldwide use of both magnetic resonance imaging (MRI) and pacing devices has vastly increased in recent years and an important number of implanted patients likely will need an MRI over the course of the lifetime of their device. Although some studies have demonstrated that, given appropriate precautions, MRI can be safely performed in patients with selected implantable pacemakers, MRI in pacemaker patients is still contraindicated. Recently, new pacing systems have been specifically designed for safe use in the MRI environment and the first experience reported suggests that the technology is safe and may allow patients to undergo MRI. This review will describe the outstanding issues and controversies surrounding the safety of MRI imaging in pacemaker patients and the potential benefits of the new MRI‐conditional technology. We will also discuss how to approach the decision whether or not an MRI‐conditional system should be implanted and highlight key issues that warrant further studies.     

Home Monitoring in Patients with Implantable Cardiac Devices: Is There a Potential Reduction of Stroke Risk? Results from a Computer Model Tested Through Monte Carlo Simulations

Introduction: Patients with pacemakers and implantable defibrillators (ICD) may experience asymptomatic atrial fibrillation (AF), detected with a delay depending on the in-person follow-up schedule. Home monitoring (HM) remote control with automatic alerts for AF may drive early anticoagulation, potentially reducing stroke risk.
Methods and Results: A sample of 136 pacemaker (103) and ICD (33) patients with or without cardiac resynchronization therapy not taking anticoagulation at implant were monitored remotely with HM. Upon HM alerts for AF, patients were recalled to update therapy. Two-year data were entered in a computer Monte Carlo model, simulating 4,000 virtual subjects with the same AF and CHADS₂ stroke risk distribution of our real population. Simulations reproduced a 2-year follow-up. Two thousand subjects were supposed to be followed with HM (HM group) and 2,000 with standard in-person follow-up (SF group) at 3, 6, 9, or 12 months.
Two-year Kaplan-Meier cumulative probability of ≥24-hour AF was 15.6% (95%CI 8.5–23.3%); the AF-related symptom rate was 27% and the median CHADS₂ score was 2. As a result of simulations, stroke incidence in case of AF was 2.3 ± 1.1% in the HM group and 2.4 ± 1.1%, 2.5 ± 1.2%, 2.7 ± 1.2%, and 2.9 ± 1.3% in the SF group with 3-, 6-, 9-, and 12-month follow-up programs, with odds ratios of 0.97 (95%CI 0.93–1.01), 0.91 (0.88–0.95), 0.87 (0.84–0.90), and 0.82 (0.79–0.85) (HM better if odds ratios <1), respectively.
Conclusions: Daily HM potentially reduces the stroke risk by 9% to 18% with respect to SF with intervisit intervals of 6 to 12 months.