Europace (2013) 15, i26–i31
doi:10.1093/europace/eut116
Automatic remote home monitoring of
implantable cardioverter defibrillator lead and
generator function: a system that tests itself
everyday
Niraj Varma*
Cardiac Pacing and Electrophysiology, Department of Cardiovascular Medicine, Cleveland Clinic (NV), 9500 Euclid Avenue, Cleveland, OH 44195, USA
Received 25 March 2013; accepted after revision 29 March 2013
The implantation of cardiac electronic devices (CIEDs) has increased exponentially over the last decade in response to widening indications. Assessment of post-implant system performance is an important responsibility but challenging in view of increasing volume, device complexity, and
advisory notices. Automatic remote home monitoring (HM) may satisfy these difficult monitoring demands. When tested, HM enhanced the discovery of system issues (even when asymptomatic) and enabled prompt clinical decisions regarding conservative vs. surgical management. This
form of remote monitoring may form a device management model in which near-continuous remote surveillance of CIED performance is combined with automatic self-declaration of system problems, enabling prompt medical decisions. The ability to collect detailed device-specific data,
with component function assessed daily, sets a precedent for longitudinal evaluation of lead and generator performance. These characteristics
have significant ramifications for CIEDs in general and patient safety.
----------------------------------------------------------------------------------------------------------------------------------------------------------Keywords
Defibrillators † Monitoring † Follow-up † Remote monitoring
Introduction
The implantation of cardiac electronic devices (CIEDs) has increased
exponentially over the last decade in response to widening indications. Compromised CIED system (generator/lead) integrity
demands prompt evaluation. Its discovery requires rigorous postimplant monitoring. This is a physician responsibility expressed in
several position statements and consensus recommendations and
now also often demanded by patients.1 – 3 The task is daunting in
view of increasing volume and complexity of implantable devices,
and added burdens imposed by advisory notices. (Fortunately,
current era CIEDs are exceptionally reliable, and component
failure is infrequent. In relative terms, leads represent the weak
link). Conventionally, patients are seen regularly according to calendarbased schedules [e.g. 3 monthly for implantable cardioverter defibrillators (ICDs)/cardiac resynchronization therapies]. However, this
method will miss potentially serious problems occurring between
interrogations, which is when they are most likely to occur.
Remote monitoring of patients with implantable devices promises
resolution of some of these challenges. This rationale underlied
announcements from professional societies for ‘development and
utilization of wireless and remote monitoring technologies’, carrying
the expectation of early detection and correction of device malfunction.1,3 However, ‘early’—especially important in an era of multiple
advisories—remains undefined. Expectations are for as soon as possible, but the capability of remote monitoring to deliver this function
may extend from months to minutes, according to the system
selected.4,5 For example, inductive (wand-based) systems depend
on patient (and hospital) adherence to scheduled follow-ups (e.g. 3
monthly) which is erratic, and continue to fail to disclose asymptomatic interim problems.5 – 7 This is not acceptable as an early warning
system.
Automatic wireless transmission technologies potentially overcome several of these obstacles. Changes in device (or patient) condition can be notified almost immediately.4 This form of advanced
remote monitoring system, pioneered by Biotronik with Home MonitoringTM (HM), effectively provides near-continuous surveillance
without patient participation, enabling both detection of asymptomatic events and cataloguing performance history on remote servers.
Diagnostic ability may be aided by automatically wirelessly transmitted electrograms (e.g. Figure 1). Daily transmissions generate highresolution parameter trending and enable assessment of changes
* Corresponding author. Tel: +1 216 444 2142; fax +1 216 445 6161, Email: varman@ccf.org
Published on behalf of the European Society of Cardiology. All rights reserved. & The Author 2013. For permissions please email: journals.permissions@oup.com.
Home monitoring of ICD system function
i27
Figure 1 (Left) Event notifications suggestive of AF (top) but accompanying wirelessly transmitted intracardiac electrograms indicate that the abnormality was caused by lead noise, likely due to fracture. Lead impedance trend (not shown) was normal. The automatically transmitted accompanying electrogram of the event was very useful, permitting the diagnosis of a false-positive mode switch in this case. (Right) Non-physiological
signals due to electromagnetic interference. Event notification received for an aborted shock detected at 7:16 pm. The accompanying automatic
wirelessly transmitted electrogram shows gross artefact on both atrial and ventricular leads. The subject was asymptomatic but in response to
the notification was seen in-office within 24 h. (Compiled with permission from Varma et al.13)
that are significant. For example, with a sudden change in lead impedance of an ICD lead under Class 1 recall, absolute value remained
within specifications, but deviation from historical trend triggered
event notification (Figure 2). The combination of two or more parameter deviations, as illustrated, may improve specificity of the alert, e.g.
linking of non-sustained ventricular tachycardia (VT) events to an impedance deviation improved detection of lead failure.8 These processes, individualized in each patient, improve the value of alerts
received.
This automatic daily surveillance technology which self-declares
significant problems as and when they occur, even when the
patient is unaware of them, has obvious application to monitoring
CIED function. Several short reports support this. For example,
failure of an ICD to properly charge its capacitors and deliver appropriate therapy,9 inappropriate VT detection caused by supraventricular tachycardia, and intermittent T-wave oversensing were all
diagnosed by remote alert transmissions intracardiac electrogram
and managed by urgent non-routine follow-ups. In another assessment of lead failure (n ¼ 54 patients), 80% of patients were asymptomatic at first episode of oversensing, and symptomatic problems
were reduced with those managed with HM (27.3%) vs. without
(53.4%, P ¼ 0.04). Events were notified 54 days after the last ICD interrogation and 56 days before next scheduled visit, i.e. reaction time
was advanced by almost 2 months to avoid adverse events.10
The utility of remote device management illustrated by these
earlier reports was confirmed prospectively in the randomized
TRUST trial, which tested the hypothesis that HM would be superior
to conventional care for surveillance of system integrity and function,
and that device initiated event notifications would enable early detection of ICD dysfunction as called for in societies’ statements.11 Since
HM had demonstrated high fidelity transmission with virtually immediate notification ability in pilot studies,4 TRUST also tested whether
early detection could be achieved the ‘same day’ in real-world practice. The results were revealing. Although the number of patients
developing problems were equal in both study arms, expected in a
large well-randomized trial, the number of detections of ICD
system dysfunction were greater with HM. Conventional monitoring
grossly under-reported occurrence of ICD dysfunction, and this loss
progressively enlarged with time (Figure 3). Notably, 47% of all
detected events were asymptomatic—such clinically silent events
would have remained undiscovered with conventional care until
next in-person evaluation, possibly several months distant to time
of occurrence. The capacity for early detection with HM was examined in detail. The majority (51%) of events were detected the same
day, even when asymptomatic. Lapses (i.e. discovery .24 h) likely
resulted from delays by handling facilities, i.e. although remote monitoring provides a considerable advance over conventional in-person
evaluations, early reaction ability nevertheless demands consistent
i28
N. Varma
Figure 2 Implantable cardioverter defibrillator generator with automatic wireless remote monitoring coupled to a Fidelis (MDT 6949) lead. Two
event notifications that were transmitted immediately on occurrence of lead fracture, occurring silently during sleep at 4:43 am, 6 weeks after last
clinic follow-up on November 14. Left: Two occurrences of detection in VF zone are noted (top) and flagged (red exclamation mark on yellow background). The accompanying wirelessly transmitted electrogram demonstrated irregular sensed events (markers indicate coupling intervals as short
as 78 ms) with VF detection (marked). No therapy was delivered indicating spontaneous event termination. Right: The second event report is a separate notification in response to the same event indicating a lead impedance alert. Lead impedance trend had been stable below 600 V in prior weeks,
but then suddenly increased .500 V triggering an event notification (red dot) although this absolute value was still within specifications. Electrogram
definition was modest in first-generation device with wireless intracardiac electrogram transmission (Lumos). Current generation devices transmit
electrograms with improved resolution (1/128 s) and longer duration including post-detection sequences (e.g. Figure 1). (Compiled with permission
from Varma39.) The clinic received these notices and informed the patient who was then reviewed urgently within 24 h and treated with lead extraction and replacement. The case demonstrates the value of remote monitoring with daily automatic surveillance and rapid, automatic (i.e. without
patient participation) event notification to the clinic of fault detection which enabled prompt intervention. Without automatic wireless remote monitoring, presentation may have occurred later with inappropriate shocks or catastrophically with failure of pacing or VF sensing.
clinic workflow routine. Indeed, device clinic oversight (and not
transmission breakdown) was the major cause of lapses of remote
follow-up in TRUST. This is important, since event triggers cover
an extensive range of potentially lethal system problems (e.g. elective
replacement indicator (ERI), lead fracture, high-voltage circuitry
failure12), especially since almost one-half of these were clinically
silent. Any delay in reaction is undesirable and potentially hazardous
(Figure 4).
The clinical merits of early detection with automatic remote HM
for patient and device care are significant. These included prompt decision making and intervention, e.g. surgically for lead failure, or conservatively with reprogramming to prevent potential inappropriate
therapies (Figures 1 and 2).13 Reprogramming changes accounted
for the majority of ‘actionable’ interrogations in the TRUST trial.14
This is important since programming may directly affect mortality.15
Hence, early notification of a need to optimize programming in any
particular patient (which is likely to change during device lifetime)
may be beneficial. The non-sustained ventricular arrhythmia notification may be triggered by system issues such as lead electrical noise
artefacts caused by fracture or non-physiological electrical signals,
and direct intervention to pre-empt shock delivery and reduce
patient morbidity.13,16 Interruption of repeated charge cycles
which occur in a significant minority of ICD patients is important to
prevent early battery exhaustion.17 In the multicentre ECOST trial,
clinical reactions enabled by early detection resulted in a large
reduction in the number of actually delivered shocks (272%), the
number of charged shocks (276%), the rate of inappropriate
shocks (252%), and at the same time exerting a favourable impact
on battery longevity.18 These advantages are especially apparent in
those in whom conventional follow-up is challenging, e.g. children.19
Advisories
Automatic remote monitoring may facilitate management of advisories (Figure 2). These largely encompass disintegration of highvoltage circuitry, battery depletion, and lead failure, which are captured by currently evaluated event triggers.20,21 Intensifying surveillance with conventional detection methods, such as increasing the
frequency of office visits, e.g. monthly22 are impractical, onerous,
and inefficient since problem incidence is low and this schedule is
likely to miss dangerous interim problems. Patient alert mechanism
such as beeps, are insensitive and prone to false-positive evaluations.23,24 In contrast, HM generators trigger immediate alerts on deviation from established trends. This reduces burden both for
patients to monitor their own devices frequently and for clinics responsible for large populations with a low incidence of typically
silent problems. Identification of the small number of affected
devices may permit elective replacement of these few and avoid unnecessary large-scale elective replacement. Continuous monitoring
may aid balanced management decisions since a similar malfunction
may confer different risks in different patients. For example,
Home monitoring of ICD system function
i29
Figure 3 Event-free survival rates in HM compared with conventional care in the TRUST cohort. Protocol required event notifications were
system related (end of service, ERI, atrial impedance ,250 or .1500 V, ventricular impedance ,250 or .1500 V, daily shock impedance
,30 or .100 V, shock impedance ,25 or .110 V); arrhythmia-related events (atrial burden .10%, SVT detected, VT1 detected, VT2 detected,
VF detected), and ineffective ventricular maximum energy shock (notified on first shock of any sequence in a given episode). (Compiled with permission
from Varma et al.13)
immediate replacement of a lead under advisory may be unnecessary
in patients who are not pacemaker-dependent. Hence, remote management has the potential to diminish morbidity/mortality, and
reduce associated hospital admissions with significant implications
for cost reduction. This ability may depend on the type of problem.
For example, one-third of patients with Fidelis lead failure receive inappropriate shocks within 3 h, the time between the occurrence of
event and patient morbidity. This may be too short to permit intervention.23 The warning may be advanced by integrating automated
safety surveillance systems into remote monitoring databases.25
Future technology may incorporate an ability to adjust programming
to respond to failures detected during monitoring. Other significant
lead problems may occur without deviation of any electrical parameters.26
Databasing
Automatic warehousing of performance data retrieved daily from
large and complete patient cohorts (without errors associated with
manual data entry) permits long-term longitudinal evaluation of
system survival. This provides not only a mechanism to rapidly identify individuals who develop out-of-bounds values, but also an opportunity to define standards of performance for device components
and function.27,28 In comparison, other available techniques have significant limitations. For example, device function has been determined during sporadic conventional in-person follow-up and
symptomatic patient presentation, or analysis of voluntary return
of products which is vulnerable to reporting bias.29 These lend to inconsistent results. For example, 5-year lead malfunction rates varied
sharply from 2.5 to 15% in different studies.30,31 Even when a single
Figure 4 Days to detection of ICD problems in patients assigned
to remote HM. Overall, 22 of 43 (51%) were detected within 24 h.
(Compiled with permission from Varma et al.40)
component is being tracked (e.g. the Fidelis lead32) there is variation
in incidence of failure among different reports. Definitions of failure
themselves are inconsistent. In one study,30 problems were discovered during routine face-to-face follow-up and reprogramming
changes without surgical intervention were included in the ‘failure’
rate. In contrast, in another study 76% of lead malfunction came to
clinical attention because of inappropriate ICD therapies and the
i30
need for surgical revision defined failure.31 Both reports may underestimate the true incidence of lead failure if malfunctions are asymptomatic, occur intermittently, or result in death (only a minority of
devices are interrogated post-mortem). Hence, non-compulsory
follow-up methods generate inaccuracies and may undermine the important task of ICD component surveillance and assessment of reliability. In contrast, continuous remote monitoring, as currently
described, represents a more comprehensive evaluation mechanism,
working independently of symptoms or follow-up schedule, and permitting application of uniform definitions for out-of-range behaviour.
There are limitations. It is important to note that HM does not supplant the first post-implant in-person evaluation,33 important for assessment of wound healing, determination of chronic thresholds, and
setting of final pacing parameters. Problems such as lead perforations
or failures requiring revision and symptomatic reactions to implantation
(e.g. pacemaker syndrome, diaphragmatic pacing, and pocket infection)
cluster in this early post-implant. They occur more frequently with dualchamber or resynchronization units.34 – 36 However, subsequent to this
mandatory initial in-person evaluation, HM surveillance was demonstrated to be superior to regular office checks in the TRUST study.
These results described with HM, which has excellent transmission reliability37 may not be extrapolated readily to all proprietary technologies. Thus, in the CONNECT trial, which was structured similarly to
TRUST but used a different remote wireless technology, a large proportion of attempted transmissions simply failed.38 When alert transmissions for some conditions were successful, manual reset was
required to reactivate this notification ability, i.e. the ability for further
notification in the interim was lost until an otherwise unnecessary
in-person encounter could be arranged. This design, depending on
patient interaction and single transmissions vulnerable to failure,
limits its role as an early warning mechanism.
In summary, recent results indicate that HM is a stringent method
of post-implant ICD evaluation in which system components are
tested, reported, and databased daily. Warehousing of collected
data in his fashion will permit characterization of device behaviour,
determination of reliability, and definitions of abnormality. Certain
points require emphasis. The technology is automatic and maintains
high-intensity vigilance without the need for patient interaction, and
pre-specified ‘out-of-bounds’ conditions are flagged for attention,
enabling same day discovery (irrespective of follow-up schedule).
Asymptomatic issues are covered equally well. With regards to the
denominator, the very high reliability of implanted systems is to be
appreciated since dysfunction is infrequent, but this makes the task
of identifying these few especially challenging. However, remote
monitoring as described, directs virtually immediate attention to
patients developing problems, as and when they occur, thus effectively finding the proverbial needle in the haystack, a task beyond conventional means. In practice, this ability may be influenced by engineering
differences, transmission frequency, methods of alert notification,
and handling by receiving facilities.
In conclusion, automatic continuous remote monitoring represents an early warning system which can provide assurance to both
patients and their physicians.
Conflict of interest: N.V.: Modest—Biotronik, Boston Scientific,
Medtronic, St Jude Medical. Chair and PI of the TRUST trial;
member ALTITUDE Steering Committee.
N. Varma
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