Implantable cardioverter-defibrillator lead failure: how weak is the link?

Evaluation of the in vivo chemical reactivity of a novel copolymer insulation on cardiac leads in a single-center study

BACKGROUND

Human in vivo data on the chemical stability of different transvenous lead materials, particularly OptimTM leads, are lacking.

OBJECTIVES

The purpose of this study was to determine the chemical reactivity of insulation materials by analyzing the molar mass of extracted pacing and defibrillator leads METHODS: We collected extracted leads at Emory University Hospitals and sent the leads with thermoplastic outer insulation material for molar mass analysis, a material characteristic that informs biostability. Leads were separated based on the chemical identity of the outer insulation material, and the molar mass was measured by an independent party. The extent of chemical reaction was compared across leads having different materials: poly(ether)urethane 55D, poly(ether)urethane 80A, and Optim.

RESULTS

A total of 70 leads were extracted. The subset of extracted leads having outer insulation materials composed of PEU or Optim were analyzed for molar mass, where implant times ranged from 0.12 to 16.26 years. The rate of chemical degradation was compared by plotting the extent of reaction [Mn(t = 0)/Mn(t)] as a function of implant time. The Optim molar mass decreased to 40% of its initial value at 10 years of implant. No change in the molar mass of the PEU insulations could be resolved over the same 10-year implant time.

CONCLUSION

Because the molar mass of a polymer is directly related to its mechanical integrity, the observed decrease in molar mass of Optim likely translates into premature insulation defects and is consistent with the observed increased rate of electrical malfunction/noise in this subset of cardiac leads.

Long-term performance of single-connector (DF4) implantable defibrillator leads

AIMS

Single-connector (DF4) defibrillator leads have become the predominantly implanted transvenous implantable cardioverter-defibrillator lead. However, data on their long-term performance are derived predominantly from manufacturer product performance reports.

METHODS AND RESULTS

We reviewed medical records in 5289 patients with DF4 leads between 2011 and 2023 to determine the frequency of lead-related abnormalities. We defined malfunction as any single or combination of electrical abnormalities requiring revision including a sudden increase (≥2×) in stimulation threshold, a discrete jump in high-voltage impedance, or sensing of non-physiologic intervals or noise. We documented time to failure, predictors of failure, and management strategies. Mean follow-up after implant was 4.15 ± 3.6 years (median = 3.63), with 37% of leads followed for >5 years. A total of 80 (1.5%) leads demonstrated electrical abnormalities requiring revision with an average time to failure of 4 ± 2.8 years (median = 3.5). Of the leads that malfunctioned, 62/80 (78%) were extracted and replaced with a new lead and in the other 18 cases, malfunctioned DF4 leads were abandoned, and a new lead implanted. In multivariable models, younger age at implant (OR 1.03 per year; P < 0.001) and the presence of Abbott/St. Jude leads increased the risk of malfunction.

CONCLUSION

DF4 defibrillator leads demonstrate excellent longevity with >98.3% of leads followed for at least 5 years still functioning normally. Younger age at implant and lead manufacturer are associated with an increased risk of DF4 lead malfunction. The differences in lead survival between manufacturers require further investigation.

Complications of Cardiac Resynchronization Therapy: Comparison of Safety Outcomes from Real-world Studies and Clinical Trials

Cardiac resynchronization therapy (CRT) is an important intervention in heart failure. Whether real-world complication rates mirror those reported in randomized clinical trials (RCTs) is unknown. We sought to compare rates of procedural complications between major RCTs of CRT with “real-world” complication rates reported in registries and administrative claims database studies. We conducted a PubMed search to identify all relevant publications on CRT and classified them into RCTs and registry studies. Pooled procedural complication rates were analyzed. Differences between groups were compared using the chi-squared test. We identified a total of 6 RCTs, 2 administrative claims database studies, and 4 CRT registry studies. RCTs included a total of 4,442 patients and “real-world” studies included a total of 72,554 patients. The overall rates of procedural complications with CRT were significantly higher in RCTs compared to the real world (8.1% vs. 6.9%, P = .002). Lead-related complications were higher in the real-world studies compared to RCTs (11.3% vs. 6.5%, P = .0001). This could represent a follow-up bias with patients in registries being followed up for longer durations that would compound lead complication rates. Interestingly, RCTs had a higher incidence of pocket hematomas (2.1% vs. 0.4%, P = .001). In conclusion, real-world procedural complication rates of CRT appear to be significantly lower than those reported in RCTs.

Disease Severity and Exercise Testing Reduce Subcutaneous Implantable Cardioverter-Defibrillator Left Sternal ECG Screening Success in Hypertrophic Cardiomyopathy

Background—

The features of the hypertrophic cardiomyopathy (HCM) ECG make it a challenge for subcutaneous implantable cardioverter-defibrillator (S-ICD) screening. We aimed to investigate the causes of screening failure at rest and on exercise to inform optimal S-ICD ECG vector development.

Methods and Results—

One hundred and thirty-one HCM patients (age, 50±16 years; 92 males and 39 females) with ≥1 HCM risk factor for sudden death underwent S-ICD ECG screening at rest and on exercise. Fifty patients (38%) were ineligible for S-ICD because of screening failure in every lead vector: 33 (66%) failed in the supine position, 12 (24%) failed in the standing position, and 5 (10%) failed on exercise. In patients who could exercise and passed screening at rest, 31 (44%) had 1 vector safety, 16 (23%) had 2 vector safety, and 24 (33%) had 3 vector safety. Increased R:T wave ratio in the S-ICD screening ECG (odds ratio, 4.0; confidence interval, 3.0–5.3; P <0.001) was associated with screening failure, while R/T ratio <3 in aVF (odds ratio, 0.3; confidence interval, 0.12–0.69; P =0.006) and increasing age (odds ratio, 0.97; confidence interval, 0.95–0.99; P =0.03) was associated with reduced screening failure. European Society of Cardiology risk score was higher in those failing screening (risk score 5.5% [interquartile range, 3.2–8.7] in failed versus 4.5% [interquartile range, 2.9–7.4] in passed; P =0.04).

Conclusions—

HCM patients have a significant incidence of screening failure, which is determined primarily by the increased R:T ratio on the screening ECG and lead aVF. High-risk patients have an increased screening failure rate. Optimization of sensing algorithms is required to ensure that the highest risk HCM patients can benefit from S-ICD implantation.

A systematic review of ICD complications in randomised controlled trials versus registries: is our 'real-world' data an underestimation?

Implantable cardioverter defibrillator (ICD) implantation carries a significant risk of complications, however published estimates appear inconsistent. We aimed to present a contemporary systematic review using meta-analysis methods of ICD complications in randomised controlled trials (RCTs) and compare it to recent data from the largest international ICD registry, the US National Cardiovascular Data Registry (NCDR).

PubMed was searched for any RCTs involving ICD implantation published 1999–2013; 18 were identified for analysis including 6433 patients, mean follow-up 3 months–5.6 years. Exclusion criteria were studies of children, hypertrophic cardiomyopathy, congenital heart disease, resynchronisation therapy and generator changes.

Total pooled complication rate from the RCTs (excluding inappropriate shocks) was 9.1%, including displacement 3.1%, pneumothorax 1.1% and haematoma 1.2%. Infection rate was 1.5%.There were no predictors of complications but longer follow-up showed a trend to higher complication rates (p=0.07). In contrast, data from the NCDR ICD, reporting on 356 515 implants (2006–2010) showed a statistically significant threefold lower total major complication rate of 3.08% with lead displacement 1.02%, haematoma 0.86% and pneumothorax 0.44%.

The overall ICD complication rate in our meta-analysis is 9.1% over 16 months. The ICD complication reported in the NCDR ICD registry is significantly lower despite a similar population. This may reflect under-reporting of complications in registries. Reporting of ICD complications in RCTs and registries is very variable and there is a need to standardise classification of complications internationally.