The Evidence for the ILR in Inherited Arrhythmia Syndromes

Abstract and Introduction

Abstract

Risk stratification of patients with inherited arrhythmia syndromes (IASs) can be challenging. Recent guidelines acknowledge a place for considering the implantable loop recorder (ILR) to outrule malignant arrhythmia as a cause of syncope in certain inherited arrhythmia patients who are at low risk of sudden cardiac death. In this comprehensive literature review, we evaluate the available evidence for the use of the ILR in the IASs and in relatives of victims of sudden arrhythmic death syndrome.

Introduction

The inherited arrhythmia syndromes (IASs) include the long QT syndrome (LQTS), Brugada syndrome (BrS), catecholaminergic polymorphic ventricular tachycardia (CPVT), short QT syndrome (SQTS), idiopathic ventricular fibrillation (IVF), and progressive cardiac conduction system disease (PCCD). While advances have been made in the last three decades, uncertainties remain regarding the risk stratification of patients with these conditions.

Recent guidelines acknowledge a place for considering the implantable loop recorder (ILR) as a means of rhythm-symptom correlation and to outrule malignant arrhythmia as a cause of syncope.^[1] However, case reports of life-threatening arrhythmias recorded on ILRs in patients with IASs serve as a reminder of the need for careful risk analysis before their insertion.^[2,3]

Evidence on the use of the ILR in IASs is limited and comes mainly in the form of small, retrospective analyses. Such studies often consider a group of inherited arrhythmia patients, comprised of small numbers with each individual condition. This creates challenges in drawing conclusions for the conditions individually. There is an even greater paucity of published data on the role of the ILR in relatives of patients who suffer sudden arrhythmic death syndrome (SADS). Using conventional inherited cardiac condition evaluation protocols such families are found to have a potentially inherited cardiac disease in just under one-third of cases.^[4]

Our aim was to carry out a comprehensive literature review on the evidence for the use of the ILR in patients with IASs and in relatives of patients who had suffered SADS.

Table 1. Overall outcome data
Overall outcomes of implantable loop recording for the 188 patients included in the literature review
0 deaths, 196 ILR patient events
No ventricular arrhythmia	Ventricular arrhythmia
91.8% of ILR patient events	patient events	% of total	8.2% of ILR patient events	patient events	% of total
Supraventricular tachycardia	11	5.6%	Torsades de pointes/polymorphic VT	6	3%
Atrial fibrillation	3	1.5%	NSVT	7	3.5%
Symptom event/activation with reassuring rhythm	41	20.9%	Tightly coupled ventricular couplet	1	0.5%
Premature ventricular ectopics	6	3.1%	Bidirectional VT	1	0.5%
Premature atrial ectopics	2	1%	Multifocal PVCs leading to initiation or up-titration of beta blockade	1	0.5%
Sinus arrest	4	2%
Advanced AV block	3	1.5%
Reflex asystolic syncope	1	0.5%
Prolonged pause with ICD implanted in patient with BrS/LQTS	2	1%
Prolonged pause with PPM implant in patient with BrS	2	1%
Sinus bradycardia during pre-syncope or syncope	2	1%
Asymptomatic sinus node dysfunction	1	0.5%
No recurrence of index symptom	71	36.2%
Not documented if recurrence of the index symptom during the follow-up period but no device implanted and other clinical details of ILR monitoring unknown	23	11.7%
Not documented if recurrence of the index symptom during the follow-up period but no ventricular arrhythmia detected	6	3%
Not documented if recurrence of the index symptom during the follow-up period and no further clinical details available	2	1%

Table 1. Overall outcome data

Overall outcomes of implantable loop recording for the 188 patients included in the literature review

0 deaths, 196 ILR patient events

No ventricular arrhythmia

Ventricular arrhythmia

91.8% of ILR patient events

patient events

% of total

8.2% of ILR patient events

patient events

% of total

Supraventricular tachycardia

5.6%

Torsades de pointes/polymorphic VT

Atrial fibrillation

1.5%

NSVT

3.5%

Symptom event/activation with reassuring rhythm

20.9%

Tightly coupled ventricular couplet

0.5%

Premature ventricular ectopics

3.1%

Bidirectional VT

0.5%

Premature atrial ectopics

Multifocal PVCs leading to initiation or up-titration of beta blockade

0.5%

Sinus arrest

Advanced AV block

1.5%

Reflex asystolic syncope

0.5%

Prolonged pause with ICD implanted in patient with BrS/LQTS

Prolonged pause with PPM implant in patient with BrS

Sinus bradycardia during pre-syncope or syncope

Asymptomatic sinus node dysfunction

0.5%

No recurrence of index symptom

36.2%

Not documented if recurrence of the index symptom during the follow-up period but no device implanted and other clinical details of ILR monitoring unknown

11.7%

Not documented if recurrence of the index symptom during the follow-up period but no ventricular arrhythmia detected

Not documented if recurrence of the index symptom during the follow-up period and no further clinical details available