Value of implantable loop recorders in patients with structural or electrical heart disease
Journal of Interventional Cardiac Electrophysiology
Value of implantable loop recorders in patients with structural or electrical heart disease
Rafi Sakhi 0
Dominic A. M. J. Theuns 0
Rohit E. Bhagwandien 0
Michelle Michels 0
Arend F. L. Schinkel 0
Tamas Szili-Torok 0
F. Zijlstra 0
Jolien W. Roos-Hesselink 0
Sing-Chien Yap 0
0 Department of Cardiology, Erasmus Medical Center , P.O. Box 2040, 3000 CA Rotterdam , The Netherlands
1 Sing-Chien Yap
Purpose In patients with structural heart disease (SHD) or inherited primary arrhythmia syndrome (IPAS), the occurrence of unexplained syncope or palpitations can be worrisome as they are at increased risk of sudden cardiac death. An implantable loop recorder (ILR) can be a useful diagnostic tool. Our purpose was to compare the diagnostic yield, arrhythmia mechanism, and management in patients with SHD, patients with IPAS, and those without heart disease. Methods Retrospective single-center study in consecutive patients who underwent an ILR implantation. Results Between March 2013 and December 2016, a total of 94 patients received an ILR (SHD, n = 20; IPAS, n = 14; no SHD/ IPAS, n = 60). The type of symptoms at the time of implantation was similar between groups. During a median follow-up of 10 months, 45% had an ILR-guided diagnosis. Patients with IPAS had a lower diagnostic yield (14%) in comparison to the other groups (no SHD/IPAS 47%, P = 0.03; SHD 60%, P = 0.01, respectively). Furthermore, patients with SHD had a higher incidence of nonsustained VT in comparison to patients without SHD/IPAS (30 versus 3%, P < 0.01). ILR-guided therapy was comparable between groups. In the SHD group, a high proportion (10%) received an implantable cardioverter-defibrillator; however, this was not statistically significantly higher than the other groups (no SHD/IPAS 3%, IPAS 0%, P = 0.08). Conclusions In comparison to patients without heart disease, the diagnostic yield of an ILR was lower in patients with IPAS and the prevalence of ILR-diagnosed nonsustained VT was higher in patients with SHD.
Implantable loop recorder; Bradyarrhythmias; Ventricular arrhythmias; Risk stratification; Cardiomyopathy; Channelopathy; Congenital heart disease
Implantable loop recorders (ILRs) are increasingly being
used for the detection of infrequent arrhythmia episodes.
Several studies have demonstrated the incremental value
of ILRs over intermittent monitoring strategies for the
detection of arrhythmias in patients with recurrent syncope,
undocumented palpitations, and cryptogenic stroke [
ILRs might also be used as a diagnostic tool in patients at
risk for ventricular tachyarrhythmias (VTs), such as those
with structural heart disease (SHD) or inherited primary
arrhythmia syndromes (IPAS) [
]. The occurrence of
unexplained syncope or palpitations can be worrisome in
these patients. The 2009 ESC syncope guidelines
recommend considering an ILR in nonhigh-risk patients with
SHD or IPAS . The recent J-wave expert consensus
report also suggests the use of an ILR for close monitoring of
Brugada patients with presumed non-arrhythmogenic
]. There is limited data comparing the value of an
ILR in patients with and without SHD [
the nature of the underlying disease, we hypothesized that
patients with SHD/IPAS would have a higher incidence of
ventricular arrhythmias than patients without an underlying
heart disease. The purpose of the present study was to
evaluate diagnostic yield, arrhythmia mechanism, and
subsequent arrhythmia management in patients with and without
SHD/IPAS receiving an ILR.
2.1 Study population
This observational cohort study involved consecutive
patients who received an insertable ILR (Reveal LINQ,
Medtronic Inc., Minneapolis, MN, USA) between
March 2013 and December 2016 at our institution. The
indication for the ILR was established by the treating
physician and all patients gave informed consent for the
implantation procedure. There were no patients who received
an ILR for cryptogenic stroke. Patients with SHD included
those with manifest heart disease at potential risk of
arrhythmias including patients with coronary artery disease,
inherited cardiomyopathy, infiltrative cardiomyopathy, and
congenital heart disease. Patients with IPAS included those
with long QT syndrome, Brugada syndrome, and
catecholaminergic polymorphic VT. Carriers of a pathogenic
mutation associated with cardiomyopathy or IPAS were also
considered part of either the SHD or the IPAS group.
2.2 ILR implantation and follow-up
ILR implantation was performed as recommended by the
manufacturer using the incision and insertion tool. The device
was implanted subcutaneously over the fourth intercostal
space on the left hemithorax, either 45° or parallel relative to
the sternal border. The incision was usually closed with one
braided absorbable suture. After implantation, the patient
received the remote monitoring device, as well as instructions
about its use for nightly automated transmissions. Patients
were discharged on the same day of implantation.
Programming was optimized to maintain a high specificity,
at the cost of sensitivity: detection of bradycardia (30 beats
per minute; 8 beats), pause (4.5 s), and tachycardia (176 beats
per minute; 16 beats). Atrial fibrillation (AF) detection was set
to BAF only.^ All devices were linked to the CareLink
network for remote monitoring and all episodes (automatically
recorded or patient-activated episodes) were transmitted on a
Ten days after implantation, the patients were scheduled at
the out-patient clinic to check their wound and interrogate
their device. After this visit, patients were seen at the
outpatient clinic every 6 months or earlier when necessary based
on the transmitted episodes. The diagnosis was called
ILRguided if a symptom-rhythm correlation was established and/
or if a VT was observed.
2.3 Statistical analysis
Continuous data are presented as mean ± standard
deviation if the data were normally distributed, or as median
with interquartile range (25th and 75th percentile)
otherwise. Categorical variables are presented by
frequencies and percentages. Differences of continuous variables
between groups were analyzed with the unpaired
Student’s t test or the Kruskal-Wallis test, as appropriate.
Differences between categorical variables were evaluated
using the chi-square test. In the case of a statistical
difference between groups, post hoc pairwise analysis was
performed. Event rates were estimated with the Kaplan Meier
method, and differences between event rates were
compared by log-rank test. Paired comparisons were made
using Cox regression analysis and described with hazard
ratios and 95% confidence intervals. A P value < 0.05 was
considered statistically significant. Statistical analyses
were performed using SPSS version 21.
Between March 2013 and December 2016, a total of 94
patients underwent an ILR implantation. There were 20
patients (21%) with SHD and 14 patients (15%) with
IPAS. Figure 1 provides an overview of the different
underlying diagnoses in patients with SHD/IPAS. Except a
higher proportion of PCI in the SHD group, there were
no differences in baseline characteristics between groups
(Table 1). It is also important to note that the presenting
symptoms were similar between groups.
During a median follow-up of 10 months (interquartile
range, 3–17 months), 42 patients (45%) had an ILR-guided
diagnosis. The diagnostic yield was different between groups
(Fig. 2, Table 2). When performing pairwise comparisons,
patients with IPAS had a lower diagnostic yield in comparison
to patients with SHD (P = 0.01) or patients without SHD/IPAS
(P = 0.03). Although patients with SHD and patients without
SHD/IPAS had a similar diagnostic yield, the arrhythmia
mechanism was different. Using pairwise comparison,
patients with SHD had a higher incidence of nonsustained VT
in comparison to patients without SHD/IPAS (P < 0.01).
Although there was a difference in the ILR-documented
arrhythmia mechanism, the ILR-based therapy was similar
between groups (Table 3). Most patients received
antiarrhythmic drug therapy or had their antiarrhythmic drug dose
increased. A high proportion (10%) of patients in the SHD
group received an ICD; however, this was not statistically
significantly higher than the other groups.
Four patients received an ICD; two of them had SHD.
One patient with recurrent syncope and coronary artery
disease with preserved ejection fraction received an ICD for
sustained monomorphic fast VT. Another patient with
hypertrophic obstructive cardiomyopathy received an ICD
after experiencing nonsustained VT, which increased his
estimated 5-year risk of SCD from 3.6 to 8.0%. Furthermore,
two patients without SHD/IPAS received an ICD. One
Fig. 1 Overview of patients with
structural heart disease or
inherited primary arrhythmia
syndrome. LQTS long QT
woman received an ICD for syncope and sustained
monomorphic fast VT and another woman received an ICD after
syncope and nonsustained polymorphic fast VT. No patient
died suddenly during the study period.
The present study demonstrates that ILR patients with SHD
have a higher incidence of nonsustained ventricular
arrhythmias. However, there was only a trend towards a
higher proportion of patients receiving an ICD in the SHD
group in comparison to the other groups.
Studies which evaluated the performance of the ILR
demonstrated a wide diagnostic yield ranging from 22 to 73%
depending on the primary indication of the ILR [
diagnostic yield seems lower in patients with recurrent
unexplained syncope than that in patients with undocumented
palpitations. Overall, the diagnostic yield in our study population
was 45%; however, patients with IPAS had a lower diagnostic
Fig. 2 Cumulative event rate for
yield. The diagnostic yield in patients with and without SHD
(60 versus 47%) was similar in our study. A previous Austrian
prospective ILR study in 70 patients with unexplained
syncope (including 33 patients with SHD) found a similar
diagnostic yield between patients with and without SHD (45 and 51%,
Patients with SHD in our study experienced a high
incidence of nonsustained ventricular arrhythmias, which is
not surprising considering their predisposition to
ventricular arrhythmias. A previous Italian ILR study in 103
patients with unexplained syncope (including 38 patients
with SHD) also found a difference in arrhythmia
mechanism between patients with and without SHD [
with SHD were more likely to have paroxysmal/persistent
AV block and tachyarrhythmias in comparison to patients
without SHD. The incidence of ventricular arrhythmias
was 5% in patients with SHD and 0% in patients without
]. Surprisingly, the incidence of ventricular
arrhythmias in our IPAS group was low. This may be related
to a lower threshold to implant an ILR in IPAS patients.
A l t h o u g h r e c u r r e n t u n e x p l a i n e d s y n c o p e i s a n
established indication for an ILR, a rather novel indication
is the use of an ILR for risk stratification [
]. An EHRA
survey demonstrated that 19% of centers use ILRs in
patients with borderline indications for ICD therapy .
Currently, the ILR does not play a major role in the current
AV, atrioventricular; ST, sinus tachycardia; SVT, supraventricular tachycardia; VT, ventricular tachycardia
*< 40 bpm for more than 10 s
guidelines on the prevention of SCD [
]. In the most
recent guidelines, ILRs are recommended after
comprehensive diagnostic evaluation when symptoms (e.g.,
syncope) are sporadic and suspected to be related to
]. In some patients with SHD/IPAS, individual risk
stratification can be difficult due to atypical symptoms. In
these patients, long-term monitoring by an ILR may
provide valuable information by the documentation of
ventricular arrhythmias. Furthermore, it might also provide
reassurance in these patients when they know that their
sympt o m s a r e n o t r e l a t e d t o v e n t r i c u l a r a r r h y t h m i a s .
Considering the fact that a purely diagnostic tool is
implanted in patients at risk for VTs, it is of importance to
be alerted of a potential life-threatening episode as soon as
possible. This is possible due to the availability of daily
remote transmissions lowering the delay to medical
intervention. No patient in our study died suddenly.
Several small ILR studies in patients with SHD or IPAS
demonstrated that the proportion of ILR patients that
received an ICD varies. Based on the available literature, no
ILR patient with Brugada syndrome [
], long QT
], hypertrophic cardiomyopathy , or
noncompaction cardiomyopathy [
] received an ICD
during follow-up. In contrast, ICDs were implanted, based on
the findings of the ILR, in patients with catecholaminergic
polymorphic VT (11%) [
], congenital heart disease (0–
16, 18, 19
], Fabry cardiomyopathy (25%) [
SHD (0–28%) [
9, 10, 21
]. In our study, 10% of the SHD
cohort received an ICD. Abovementioned data supports the
use of ILRs in symptomatic patients with SHD for early
detection of ventricular arrhythmias.
4.1 Study limitations
The present study is small and the patient population is
highly selected, thereby limiting the generalizability of
the data. Furthermore, the lack of a control group (close
follow-up with repeated ambulatory Holter monitoring)
hampers conclusions on the incremental benefit of an
ILR in comparison to alternative methods of monitoring.
Therefore, all conclusions of the present study must be
drawn with caution.
Compliance with ethical standards
All patients gave informed consent for the implantation procedure.
Conflict of interest The authors declare that they have no conflict of
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