Remote monitoring for prevention of inappropriate implantable cardioverter defibrillator shocks: is there no place like home?

This editorial refers to ‘Potential role of home monitoring to reduce inappropriate shocks in implantable cardioverter-defibrillator patients due to lead failure’ by S. Spencker et al., on page 483 Although the implantable cardioverter defibrillator (ICD) has made a significant impact on prevention of sudden arrhythmic death, important limitations of this therapy remain. Chief among these is the risk of inappropriate shocks, which have been reported in 10‐25% of patients in randomized trials and case registries over 2‐4 years of follow-up. 1 Inappropriate shocks may cause pain, proarrhythmia, and even death in rare cases. Delivery of inappropriate shocks has also been associated with increased late mortality in several large ICD trials. Patients who experience multiple shocks may develop anxiety and other signs of psychological distress, and concern about this complication is commonly expressed by patients. The most common cause of inappropriate shocks is atrial fibrillation, followed by other supraventricular tachycardias, and leadsensing abnormalities. The latter category includes conductor fracture, insulation failure, T-wave oversensing, and myopotential oversensing. 2 A recent study examined 990 patients implanted with a variety of ICD lead models between 1992 and 2005 and found lead failure rates of 15% at 5 years and 40% at 8 years, with a pattern of accelerating annual failure rates over time. 3 One-third of ICD lead failures in this study presented with inappropriate shocks. In patients dependent upon ventricular pacing, ICD lead failure may also lead to symptoms from inhibition of pacing or failure to capture. Concern regarding ICD lead failure has increased recently with the recall of a widely used lead. 4 Manufacturers’ product performance reports suggest early annual lead failure rates of 0.5‐1% of latest generation of ICD leads, while the failure rate of the Sprint Fidelis family is approximately two- to three-fold higher. A 2007 review of the US Food and Drug Administration’s Manufacturer and User Facility Device Experience database found 679 reports of failed Sprint Fidelis leads, 33% of which were associated with inappropriate shocks. 4 Strategies to minimize the risk of inappropriate shocks include using high ventricular tachycardia/ventricular fibrillation rate cutoffs, multiple tachycardia detection zones, longer time to detection, anti-tachycardia pacing, supraventricular tachycardia discrimination algorithms, and medical therapies such as b-blockers and anti-arrhythmic drugs. 5 These strategies are less useful for the prevention of inappropriate shocks caused by ICD lead failure. For this purpose, algorithms have been devised to trigger device alert tones, device vibration, or automatic change in tachycardia detection criteria. 6 None of these algorithms, however, has been prospectively shown to reduce the risk of inappropriate shocks, and improved strategies to prevent inappropriate shocks are clearly needed. Spencker et al. report on their single-centre experience using an automatic wireless remote monitoring system for surveillance of ICD systems. 7 They retrospectively examined 54 patients who underwent ICD lead revision for the failure of the lead over a 6-year period. The 11 patients who had been undergoing daily remote wireless assessment were compared with the 43 patients who had been followed only with quarterly in-office visits. They found that fewer patients undergoing remote monitoring (27.3%) experienced ICD shocks for sensing failure prior to lead revision than those with standard in-office follow-up (46.5%). This trend reached statistical significance when symptomatic pacemaker inhibition was added to the endpoint (27.3% in remote monitoring group vs. 53.4% in the standard follow-up group, P ¼ 0.04). In addition, the authors found that in the standard follow-up patients, evidence of non-sustained oversensing was detected by the ICD a mean of 16 days prior to the onset of symptoms, suggesting that inappropriate shocks could have been avoided in most of these patients, had they been followed with remote monitoring and contacted in a timely fashion.