Predictors of ventricular arrhythmias in arrhythmic mitral valve syndrome – a study using implantable loop recorders
Authors: Aabel E , Chivulescu M , Lie Ø H , Rootwelt-Norberg C , Ribe M , Gjertesen E , Hopp E , Edvardsen T , Helle-Valle T , Hegbom F , Dejgaard L A , Haugaa K H 
Published: October 2022

Abstract

Background
Arrhythmic mitral valve syndrome is linked to life-threatening ventricular arrhythmias, but the incidence and methods for risk stratification of ventricular arrhythmias are not well known.

Purpose
In this prospective study, we aimed to describe the incidence of ventricular arrhythmias by use of continuous rhythm monitoring and propose risk stratification in patients with arrhythmic mitral valve syndrome.

Methods
We included consecutive patients with arrhythmic mitral valve prolapse, defined as mitral valve prolapse and/or mitral annulus disjunction (MAD) with arrhythmic symptoms or documented complex premature ventricular complexes (PVC). We implanted loop recorders (ILR) in patients with arrhythmic mitral valve syndrome with no previous severe ventricular arrhythmias and all were followed by remote monitoring. We monitored for non-sustained ventricular tachycardias (NSVT) and severe ventricular arrhythmia, defined as aborted cardiac arrest, sustained ventricular tachycardia and NSVT with syncope/presyncope. At baseline, patients underwent echocardiography, 24-hour Holter monitoring, stress ECG and cardiac magnetic resonance imaging.

Results
We included 60 patients (73% female, 49 years [interquartile range [IQR] 37–60]). At baseline, median PVC burden was 232 per 24-hours (IQR 33–1329), and 8 (13%) patients had NSVT by Holter monitoring or stress ECG. During 3.0±0.5 years of follow-up, severe ventricular arrhythmia occurred in 7 (12%) patients (1 aborted cardiac arrest, 6 NSVT with syncope/pre-syncope). Annual incidence rate of severe events was 4% per person-year (95% confidence interval [CI] 2–9)). Predictors of severe ventricular arrhythmia were frequent PVCs (6683 PVCs per 24h [IQR 612–10861] vs. 154 PVCs per 24h [IQR 25–562], p=0.01), more NSVTs by ILR (4 NSVTs [IQR 2–7] vs. 0 NSVTs [0–1], p&lt;0.001), greater left ventricular diameter (57±6 mm vs. 51±6 mm, p=0.01) and greater posterolateral MAD distance (9 mm [IQR 8–12] vs. 4 mm [IQR 0–6], p=0.02). Adjustment for age and sex did not change significant risk markers (all p&lt;0.02). During follow-up 102 NSVTs were recorded in 24 (40%) patients. In multivariate Poisson regression adjusting for age, mitral regurgitation grade and bileaflet prolapse, predictors of high NSVT burden were frequent PVCs (incidence rate ratio [IRR] 1.14 [95% CI 1.04–1.27], p=0.01), PVCs from inferior left ventricle (IRR 5.19 [95% CI 2.80–9.63], p&lt;0.001) and late gadolinium enhancement (IRR 3.16 [95% CI 1.68–5.97], p&lt;0.001).

Conclusion
Yearly incidence of first severe ventricular arrhythmia was 4% in patients with arrhythmic mitral valve syndrome, emphasizing the high risk of life-threatening events in these patients. Frequent PVCs, NSVTs, greater left ventricular diameter and greater posterolateral MAD distance were predictors of first severe ventricular arrhythmia and should be used in risk stratification.

Funding Acknowledgement
Type of funding sources: Public grant(s) – National budget only. Main funding source(s): This study was supported by a public grant from the Norwegian Research Council (#288438 and #309762), Precision Health Center for optimized cardiac care (ProCardio).