Continuous monitoring with implantable loop recorder detects arrhythmic risk in adults with systemic right ventricle following atrial switch
Authors: Kakarla J , Adhvaryu K , Crossland D S , Murray S , Jansen K , Rybicka J , Hermuzi T , Martin R , Shepherd E , Seller N , Coats L 
Published: November 2023

Abstract

Background
Patients with a systemic right ventricular circulation following atrial switch are at high risk of sudden death despite current monitoring strategies and advances in heart failure management. Arrhythmia represents a significant risk factor and early detection and intervention is of great value. The current surveillance approach with intermittent ambulatory monitoring is limited and cumbersome.

Purpose
We hypothesise that continuous rhythm monitoring with an implantable loop recorder (ILR) in the systemic right ventricle population will allow early detection of clinically significant arrhythmias.

Methods
Patients under follow up with a systemic right ventricular circulation following atrial switch were offered ILR implantation as an alternative to the standard of care (ambulatory 24-hour ECG). Patients with pre-existing intra-cardiac pacing devices or palliative were excluded. Following implantation, recordings made with symptoms or automatically following detection of significant arrhythmias. This included pauses over 3 seconds, atrioventricular block or supraventricular tachycardia. Transmission were reviewed daily and significant findings discussed in an adult congenital heart disease and electrophysiology MDT. Patients otherwise had routine clinical care.

Results
24 patients had implantation of a loop recorder (67% of eligible cohort). They were aged 29-49 years (median 35 years) and 50% had additional lesions. Right ventricular function was normal in 42% and 29% had moderate or severe tricuspid regurgitation. 75% of the cohort were NYHA classification I. All but one patient were in sinus rhythm and 8 (33%) had previous intra-atrial re-entry tachycardia (IART). No patient had previously documented significant conduction disease.
Implants were undertaken over 6 years without complications. 18 patients (75%) had automated or symptom activated recordings (52% automated) with a median of 2.8 recordings per patient (range 0 – 8 per patient) over 39.5 months (1.6 – 72.5 months). The recordings were clinically significant in 64% of the cohort (Table). This included 2 (9% of entire cohort) patients with atrioventricular block only, 11 patients (46%) with IART only and 4 patients (17%) with both IART and conduction disease (1 with atrioventricular block).
These recordings resulted in 5 pacemaker implants (3 for atrioventricular block) and 2 further patients declined a device (1 subsequent death). 4 patients underwent, or are awaiting, ablation for IART. Risk scoring for sudden death did not predict arrhythmia events or atrioventricular block (1) (Figure).

Conclusions
Empirical ILR implantation in this low-risk systemic right ventricle cohort was well tolerated and detected a high burden of significant arrhythmias requiring intervention. Arrythmias were not predicted by risk scoring. This monitoring approach is an effective alternative to intermittent ambulatory surveillance however the impact on sudden death is unclear.