Downloadable Software Algorithm Reduces Inappropriate Shocks Caused by Implantable Cardioverter-Defibrillator Lead Fractures

Abstract

Background-Downloadable software upgrades are common in consumer electronics but not in implantable medical devices. Fractures of implantable cardioverter-defibrillator (ICD) leads present commonly as inappropriate shocks. A lead-integrity alert (LIA) designed to reduce inappropriate shocks is the first software download approved to enhance nominally functioning, previously implanted ICDs. Methods and Results-We performed a prospective study to determine whether an LIA could reduce inappropriate shocks.Patients were included if they had ICD lead fractures confirmed by analysis of explanted leads. The LIA group included the first 213 patients who met the inclusion criteria after the LIA was approved who had the LIA downloaded. The LIA is triggered either by high impedance or rapid oversensing. It responds by delaying detection of ventricular fibrillation and initiating a patient alert every 4 hours. The control group included the first 213 patients who did not have the LIA downloaded. They were monitored by conventional daily impedance measurements that respond with a daily alert. The LIA group had a 46% relative reduction (95% confidence interval 34% to 55%) in the percentage of patients with Ն1 inappropriate shock (LIA 38% versus control 70%, PϽ0.001) and a 50% relative reduction (95% confidence interval 33% to 61%) in the percentage with Ն5 shocks (25% versus 50%, PϽ0.001). The LIA group also had a higher percentage of patients who either did not receive a shock or had Ն3 days of warning before the shock (72% versus 50%, PϽ0.001). Conclusions-A software download that upgrades previously implanted ICDs without surgical revision reduces inappropriate shocks caused by lead fractures. (Circulation.

2015 HRS/EHRA/APHRS/SOLAECE expert consensus statement on optimal implantable cardioverter-defibrillator programming and testing

“…Alerts that combine both oversensing and abrupt changes in impedance trends provide earlier warning of lead failure than a fixed impedance threshold [144,145,149]. Such alerts can be delivered via wireless remote monitoring and/or by notifying the patient via vibration or an audible tone.…”

Implantable Cardioverter-Defibrillator Leads

“…In one study, 28% of fractures presented with no or only minor oversensing. 26 Nonphysiological signals are often atypical, including only low-amplitude signals and signals that vary with the cardiac cycle, which indicates an intracardiac source ( Figure I in the online-only Data Supplement). Fracture-related signals may be precipitated by pacing, especially high-output pacing ( Figure I in the online-only Data Supplement).…”

“…Because most of the resistance is at the interface between tissue and the tip electrode, impedance is insensitive. A few fractured cable filaments may generate nonphysiological signals without measurable 26 and 15% of clinically diagnosed Riata failures. 22 Abrupt relative changes in impedance are more specific than absolute measurements, which record out-of-range values for gradual changes at the electrode-myocardial interface, 25 but a single abrupt change can be spurious.…”

“…of triggering by electromagnetic interference in integrated bipolar leads (<1/400 versus 1/80 patient-years). 11,26,32 Once an alert is triggered, the lead integrity alert sounds an audible tone, initiates an immediate remote-monitoring notification in ICDs with wireless telemetry, and reprograms the number of intervals to detect VF to 30/40, which reduces inappropriate shocks caused by transient, fracture-induced oversensing. 11 In a prospective study, the lead integrity alert reduced inappropriate shocks compared with conventional impedance monitoring (lead integrity alert 38% versus control 70%, P<0.001).…”

Ventricular Arrhythmias in Patients With Implanted Defibrillators

“…10 Those who have had VT or VF will broadly fall into 1 of 3 groups. The first are typically stable with modest heart disease and preserved functional capacity, who return to a stable state following ICD termination of an arrhythmia.…”