Implementation of Lead Safety Recommendations

Myocardial injury secondary to ICD shocks: insights from patients with lead fracture

BACKGROUND

Patients who receive appropriate implantable cardioverter defibrillator (ICD) shocks have a subsequent adverse prognosis. Most data suggest that patients with inappropriate ICD shocks also have a subsequent adverse prognosis, although this is more controversial. The shocks may be an epiphenomenon, that is, a marker of underlying disease progression; however, it cannot be excluded that shocks cause direct myocardial damage. This latter question is difficult to clarify as the arrhythmia provoking the shock can also cause troponin release. Inappropriate shocks secondary to lead fracture are an ideal situation to examine this question; any troponin release in an otherwise well and hemodynamically stable patient, is likely due directly to the shocks.

METHODS

All patients with Fidelis lead fracture admitted to our institution with inappropriate shocks were included in this study. Troponin (I or T) was considered positive if the level was above the 99th percentile reference cutoff.

RESULTS

Elevated troponin levels were recorded in 16 of 22 patients (73%). Patients with elevated troponin received a higher number of shocks (20.3 ± 30.1 vs 5.3 ± 4.8, P = 0.07) compared with patients with normal troponin. Very elevated troponin levels (>0.8 mcg/L) were seen in five of 22 (22%) patients. The mean peak troponin level for these five patients was 7.06 ± 8.56 mcg/L; two patients had troponin levels that would be expected from a medium-sized myocardial infarction or severe myocarditis.

CONCLUSION

Troponin elevation occurred in the majority of our patients after inappropriate ICD discharges secondary to lead fracture. This indicates that ICD shocks can cause myocardial injury.

Clinical outcomes in patients with implantable cardioverter defibrillators and Sprint Fidelis leads

OBJECTIVE

The performances of implantable cardioverter defibrillators and leads are important issues for healthcare providers and patients. In 2007 Sprint Fidelis leads were found to be associated with an increased failure rate and so the purpose of the study was to evaluate long-term mortality and clinical outcomes in patients implanted with Sprint Fidelis leads compared with Sprint Quattro leads.

DESIGN, SETTING, PATIENTS

508 patients with Sprint Fidelis leads and 468 with Sprint Quattro leads were prospectively followed in 12 Italian cardiology centres.

MAIN OUTCOME MEASURES

Information on hospitalisations and other clinical events were collected during scheduled and unscheduled hospital visits. Deaths were identified from medical records or via phone contacts with patients' family members or through the National Office of Vital Statistics.

RESULTS

Over a mean follow-up of 27±18 months 141 deaths occurred in the overall population. No death was observed in patients with diagnosed failing lead. Kaplan-Meier patient survival differed between the two lead groups (80±2% in Fidelis leads vs 70±4% in the Sprint Quattro leads at 4 years, p=0.002). Multivariate analyses showed that mortality was neither associated with lead type nor with diagnosed failed lead. The annual rate of lead failure was 1.8% patient-year for Fidelis leads and 0.2% for the Sprint Quattro leads.

CONCLUSIONS

In our multicentre research, the clinical outcomes of patients with Fidelis leads differed from those of patients with Sprint Quattro leads. Nevertheless, neither mortality nor the combined endpoint of mortality and heart failure hospitalisations was associated with the lead type. http://clinicaltrials.gov/ct2/show/NCT01007474.

Spectral methods to distinguish ventricular fibrillation from artefact in implantable cardioverter-defibrillators

BACKGROUND

Despite the proven benefit of implantable cardioverter-defibrillators (ICDs), inappropriate shocks remain a significant problem. Recent trends have shown an increased incidence of lead failure and an increased exposure of devices to extreme electromagnetic interference environments.

AIMS

The goal of the current study is to evaluate the spectral characteristics of ventricular fibrillation (VF) detected in an ICD at time of defibrillation threshold testing and use of the findings to predict event types from a population of clinical VF and artefact events.

METHODS AND RESULTS

A modelling group was created from induced VF and artefact events at time of ICD implantation and DFT testing. Power spectral density evaluation was performed on each event and used to calculate an energy ratio (ER; the ratio of energy under the first three harmonics to the entire spectrum). The model was then applied to a database of clinical VF and artefact events to determine its sensitivity and specificity. The far-field ER of the modelling group was significantly larger for VF (0.888 ± 0.110) than artefact (0.265 ± 0.156, P < 0.0001). In the test group, the far-field ER of VF (0.882 ± 0.088) was also significantly larger than artefact (0.344 ± 0.128, P < 0.0001). At a cut-off of >0.526, the far-field ER had a sensitivity of 100% [confidence interval (CI) 100-100%] and a specificity of 92.4% (CI 84.9-98.5%) to distinguish clinical VF from clinical artefact.

CONCLUSION

Far-field signal during VF detected by an ICD has a distinct spectral pattern that can distinguish VF from artefact.

[Sprint fidelis defibrillation lead: a nine-center experience in Spain]

INTRODUCTION AND OBJECTIVES

Sprint Fidelis defibrillation leads are prone to early failure. Most of the reported series come from a single institution. This paper describes the clinical experience in nine Spanish hospitals.

METHODS

Clinical, implant, and follow-up data of all patients with a Sprint Fidelis lead were analyzed. All cases of lead failure were identified, medium-term lead survival was calculated, and possible predictors for lead failure were determined.

RESULTS

In total, 378 leads in 376 patients were studied. The mean age (male 85.7%) was 64.9 ± 13.6 years. The majority of patients (59.8%) had ischemic heart disease. Mean left ventricular ejection fraction was 33.4% ± 14.5%. Left subclavian vein puncture was used in 74.8%. During a mean follow-up of 30.9 ± 14 months, 16 lead failures have occurred, with a lead survival of 96.1% at 36 months after implantation. Eleven of 16 lead failures were caused by failure of pace/sense conductors, 3 by defects in the high-voltage conductor, and 2 by defects in both types of conductors. A less depressed left ventricular ejection fraction was associated with an increased probability of lead failure (42.4% ± 16% vs. 33% ± 14.3%; P =.011). Three hospitals presented a rate of lead failure higher than 10%; the rate was less than 5% in the remaining 6 hospitals.

CONCLUSIONS

In this multicenter series of 378 leads, the 3-year estimated survival was higher than that reported in prior series. Clinical presentation of lead failures was similar to that reported previously. Left ventricular ejection fraction and hospital of implantation were variables associated to lead failure.