Editorial
Implantable Cardioverter-Defibrillator Lead Performance
William H. Maisel, MD, MPH; Daniel B. Kramer, MD
I
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mplantable cardioverter-defibrillators (ICDs) have revolutionized the treatment of patients at risk for sudden cardiac
death. In the nearly 3 decades since the first human ICD
implant,1 millions of devices have been implanted worldwide
and innumerable lives have been saved. Successful resuscitation of a potentially lethal ventricular arrhythmia by an ICD
system depends on successful arrhythmia detection and
timely delivery of therapy. Both the ICD generator and the
ICD lead are critical components of this system. The lead, in
particular, is literally a lifeline whose purpose is to convey
critical information about the heart’s rhythm to the ICD
generator and, in turn, to deliver life-sustaining therapy when
needed. Failure of an ICD lead may result in significant
clinical events, including failure to pace, failure to defibrillate, inappropriate shocks, and even death.
In the current issue of Circulation, Eckstein et al add to our
understanding of ICD lead performance.3 The investigators
conducted a retrospective analysis of 1317 consecutive patients who received ICD systems (including 38 different ICD
lead models) at 3 centers in Germany between 1993 and
2004. Follow-up after implantation included noninvasive
routine lead evaluation every 3 to 6 months. Lead failure was
defined as a lead-related problem requiring surgical revision
performed at the discretion of the treating physician. Abnormalities were classified as either structural (insulation defects
or lead fracture) or functional (far-field sensing; T-wave or
physiological oversensing, noise from contact with another
lead, unstable impedance measurements, R-wave reduction,
or loss of capture).
During a median follow-up of 6.4 years, 38 ICD leads
required surgical revision, resulting in a reported cumulative
ICD lead survival rate of 97.5% at 5 years. Compared with
previous reports on ICD lead performance, this failure rate is
low. This low rate could be due to underdetection of lead
failures, a high clinical threshold for replacing a failed lead,
a strict definition of lead failure, or the great skill of the
implanting physicians. Interestingly, patients who underwent
ICD lead revision for malfunction had an 8-fold higher
incidence of experiencing another lead failure; this higher
incidence underscores the important contribution of patient
factors to ICD lead performance. Causes of malfunction were
similar to those in prior published reports and most often
were related to insulation defects and lead fractures. Inappropriate ICD therapies occurred in 76% of those patients who
experienced a lead malfunction.
Like the Eckstein study, a number of prior published
reports inform us about the reliability and durability of ICD
leads4 –11 (Figure 1). Reported ICD lead “survival” varies
from 91% to 99% at 2 years, 85% to 98% at 5 years, and 60%
to 72% at 8 years. Several conclusions may be drawn from
review of the data:
Article p 2727
ICD leads, like many medical technologies, have undergone a remarkable transformation. Epicardial leads, which
necessitated a thoracotomy for lead placement, have given
way to transvenous leads, which are easier to implant, less
costly, and associated with decreased morbidity and mortality.2 Important advances in transvenous lead technology, such
as the development of steroid elution, smaller diameter leads,
novel insulations, and multipolar leads, have translated into
meaningful clinical benefits for patients. Although modern
ICD leads consist primarily of electrodes, conductors, insulation, and a fixation mechanism to attach the lead to the
myocardium, lead design and performance vary from model
to model. Indeed, monitoring of performance is critical not
only to identify products with increased failure rates but also
to provide physicians and patients with realistic expectations
of device performance.
The opinions expressed in this article are not necessarily those of the
editors or of the American Heart Association.
From the Medical Device Safety Institute, Department of Medicine,
Beth Israel Deaconess Medical Center (W.H.M.), and Department of
Medicine, Massachusetts General Hospital (D.B.K.), Boston, Mass.
Dr Maisel is a US Food and Drug Administration consultant, a
member of the Medicare Coverage Advisory Committee, and Cochair of
the Heart Rhythm Society Task Force on Lead Performance Policies and
Guidelines. Dr Kramer is a member of the US Food and Drug Administration Medical Device Fellowship Program. The opinions expressed in
this article are those of the authors and do not necessarily represent the
practices, policies, positions, or opinions of the Food and Drug Administration, Center for Medicare and Medicaid Services, or the Heart
Rhythm Society.
Correspondence to William H. Maisel, MD, MPH, Medical Device
Safety Institute, Beth Israel Deaconess Medical Center, 185 Pilgrim Rd,
Baker 4, Boston, MA 02215. E-mail [email protected]
(Circulation. 2008;117:2721-2723.)
© 2008 American Heart Association, Inc.
The definition of ICD lead “survival” or lead “performance”
varies from study to study. Most commonly in published
studies, lead malfunction is defined as electrical abnormalities on lead testing, a chest roentgenogram consistent with
a fracture, or evidence of oversensing unrelated to cardiac
signals. Other studies rely on physician clinical judgment
and require replacement of the ICD lead in order to
consider the lead to have malfunctioned. In most published
studies, thresholds for action are poorly defined and
ambiguous. The varying definitions make it difficult to
compare study to study and lead to lead.
ICD lead performance varies by model. Although conceptually simple, ICD leads are complicated devices with lead
designs that vary from model to model. These design
differences may include variations in insulation, cable/
conductor, length, diameter, and fixation mechanism. Pool-
Circulation is available at http://circ.ahajournals.org
DOI: 10.1161/CIRCULATIONAHA.108.776807
2721
Circulation
ICD Lead Survival (%)
2722
May 27, 2008
100
Aass (2002), n=80
Aass (2002), n=72
90
Dorwarth (2003), n=261
80
Eckstein (2008), n=1317
Ellenbogen (2003), n=76
70
Hauser (2002), n=521
60
Kitamura (2006), n=249
Kleemann (2007), n=990
50
Kron (2001), n=474
0
2
4
6
8
10
Luria (2001), n=391
Years Post Implant
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Figure 1. The results of selected studies of ICD lead performance are shown. To be included, studies had to (1) be published in a
peer-reviewed journal after 1999, (2) provide follow-up for at least 18 months after implantation, and (3) statistically account for
patients who had died or were lost to follow-up. The data point represents the point estimate of the study for ICD lead survival.
The size of the data point is proportional to the total number of patients in the study. The white data point represents the study
by Eckstein et al,3 published in the current issue of Circulation. The great variation observed in ICD lead survival is due to a variety of factors including variable study definitions of ICD lead malfunction, variable performance of different ICD lead models, and
the impact of patient characteristics and physician implantation techniques on ICD lead performance. Primary author, year of
publication, and number of patients in each study are displayed in the legend.
ing ICD lead models for analysis, therefore, is potentially
problematic, because occasionally individual ICD leads
underperform relative to the average. On the other hand,
understanding the average durability and reliability of an
ICD lead is useful as a standard to which other leads may
be compared.
Patient and physician characteristics affect ICD lead performance. Measuring lead performance is challenged by the
impact of certain patient characteristics (such as size,
activity, and anatomy) and physician characteristics (such
as implantation skill, technique, and experience) on lead
performance.
Clinical presentation of ICD lead failure varies. ICD lead
malfunction may occasionally be catastrophic and life
threatening, such as when the lead fails to deliver a needed
high-voltage therapy. More often, patients present with
inappropriate shocks or abnormal electrical parameters
detected on routine testing. Some algorithms have been
developed to detect lead abnormalities before they progress
to a clinical lead failure, but unfortunately these are
effective only in a minority of patients.
The tools available to detect impending ICD lead failure are
limited. Fluoroscopy, x-ray, electrical testing, or direct
visualization may be used to detect lead abnormalities, but
in many respects these methods are too rudimentary and
imprecise. Novel tools (eg, imaging and electrical) need
to be developed to identify lead abnormalities sooner,
both to prevent untoward clinical events and to better
monitor lead performance earlier in the lifetime of the
lead.
Given the aforementioned complexities of monitoring ICD
lead performance and the weakness of the published studies,
it is not surprising that reports of ICD lead performance have
yielded varying results (Figure 1).
Whereas ICD lead malfunction mechanisms are generally
well defined and understood, the lack of standardized ICD
lead performance definitions hinders data collection and
analysis, as well as communication about device performance. In the wake of recent high-profile ICD lead performance questions, such as those affecting the Medtronic Sprint
Fidelis and the St. Jude Medical Riata ICD leads, the Heart
Rhythm Society announced in March 2008 the formation of
the Task Force on Lead Performance Policies and Guidelines.12 The task force will make recommendations to the US
Food and Drug Administration, Congress, industry, physicians, and patients on lead performance, communication of
lead performance, surveillance, threshold for activation of
lead advisories, communication after abnormal performance
is identified, clinical management of lead performance issues,
and regulatory considerations.
A number of on-going efforts will greatly enhance our
understanding of ICD lead performance in the coming
months and years. The National Cardiovascular Data Registry
ICD Registry will incorporate ICD leads.12 The US Food and
Drug Administration is developing HeartNet, a sentinel
network of electrophysiology laboratories throughout the
United States, specially trained to report adverse events and
device malfunctions, including those affecting ICD leads.
Independent registries, such as the Multicenter Registry,13
continue to carefully monitor device performance and to
provide early warning signals for devices whose performance
expectations are not met. In addition, a number of ICD lead
manufacturers have embarked on prospective ICD lead clinical studies and registries to better monitor ICD lead performance. Wireless remote monitoring of ICD lead function also
offers enormous potential to identify performance issues
early and to provide an automated warning system to improve
patient safety (Figure 2).
ICDs are clinically proven to improve survival in select
patients at risk for sudden cardiac death. Although ICD leads
are a mature technology, monitoring of these devices remains
critical to inform physicians and patients about device per-
Maisel and Kramer
ICD Lead Performance
2723
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Figure 2. Information obtained remotely during routine follow-up from an ICD patient is shown. Right ventricular lead impedance, measured in ohms, is displayed. The lead impedance is stable in the 400 to 600 ⍀ range from January 2006 (*) until a sudden increase in
lead impedance is noted (arrow). The high impedance is consistent with a lead fracture, and this patient’s ICD lead was replaced. The
patient was asymptomatic, and the early detection afforded by the remote monitoring likely prevented an inappropriate shock or other
adverse clinical event.
formance and to identify underperforming products as early
as possible. Ongoing efforts to standardize definitions of
performance, improve timeliness of data collection, and
enhance performance reporting are underway and will benefit
the millions of patients who enjoy the benefits of these
devices.
7.
8.
Disclosures
None.
9.
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KEY WORDS: Editorials 䡵 death, sudden
tachyarrhythmias
䡲
defibrillation 䡵 registries
䡲
Implantable Cardioverter-Defibrillator Lead Performance
William H. Maisel and Daniel B. Kramer
Circulation. 2008;117:2721-2723
doi: 10.1161/CIRCULATIONAHA.108.776807
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