Cardiac Manifestations of Myotonic Dystrophy in a Pediatric Cohort

Myotonic dystrophy type 1 (DM1) is the most prevalent inherited neuromuscular dystrophy in adults. It is a multisystem disease with cardiac manifestations. Whilst these are well-defined in adults, there are scarce published data in the pediatric population. This study aimed to investigate the yield and progression of cardiac disease in pediatric DM1 patients, focusing on congenital DM1 (cDM1).

METHODS

A retrospective observational study of all pediatric DM1 patients referred to our center (December 2000-November 2020) was conducted. Patients were classified into DM1 forms according to age of symptom onset and disease severity. Patients underwent clinical and cardiac evaluation with 12-lead ECG, transthoracic echocardiography and 24-h ECG Holter monitoring.

RESULTS

67 DM1 pediatric patients were included: 56 (83.6%) cDM1 and 11 (16.4%) non-cDM1. Median follow-up time of cDM1 patients was 8.0 [3.25-11.0] years. 49 (87.5%) cDM1 patients had baseline 12-lead ECG and 44 (78.6%) had a follow-up 12-lead-ECG, with a median follow-up time from diagnosis to baseline ECG of 2.8 [1.0-8.5] years and to follow-up ECG of 10.9 [5.7-14.2] years. Overall, 43 (87.8%) presented ECG abnormalities, most commonly in the form of asymptomatic conduction disease (n = 23, 46.9%), of which 21 (42.9%) had first degree atrioventricular block (1^st AVB). There was an increase of prevalence from baseline to follow-up ECG in low QRS voltage (16.7%), poor R wave progression (13.9%), abnormal repolarisation (11.9%) and 1^st AVB (7.6%). one patient (1.8%) underwent pacemaker implantation for syncope in the context of progressive conduction disease. No patients developed left ventricular systolic dysfunction. 4 (7.1%) cDM1 patients died during follow up, including three who died suddenly with no clear cause of death.

CONCLUSIONS

This study is the first to analyse the prevalence and progression of ECG abnormalities in cDM1 pediatric patients. The high prevalence of abnormal findings, progressive changes and number of potentially associated events (1 pacemaker implantation and 3 unexplained sudden deaths) stresses the importance of systematic and continued cardiac evaluation of these patients.

P3443Myotonic dystrophy type 1 in childhood: benign from a cardiac perspective?

Introduction/Purpose

Patients with myotonic dystrophy (DM1) have an increased risk of cardiac conduction disease and ventricular tachycardia associated with sudden cardiac death. Whilst this is well-established in adults, there is little published data on cardiac abnormalities in paediatric patients. To our knowledge this is the largest described cohort of children with DM1. The aim of this study is to better understand the prevalence and type of cardiac abnormalities in paediatric patients with DM1.

Methods

We retrospectively studied consecutive patients referred to our paediatric quaternary institution between 31 December 2000 and 31 January 2019. The electronic patient record was reviewed for the presence of cardiac manifestations, including clinical assessment in clinic, echocardiogram, 12 lead ECG and 24-hour ECG.

Results

60 children were identified with a diagnosis of DM1, 56 (93%) with the congenital form of the disease. The median age at diagnosis was 2.4 (IQR 1.2–24, n=52) months. 51 (85%) were under regular formal cardiac follow up. Cardiac symptoms (syncope, palpitations or chest pain) were present in 6 (10%). 12 lead ECGs were available in 50 (83%) and there was at least one echocardiogram performed in 57 (95%). There were 3 deaths (5%), 2 sudden and unexplained (aged 11 and 6.5 years old). 1 child (2%) underwent pacemaker implantation due to the presence of syncope and evidence of progressive conduction disease (Mobitz II AV block).

During the period of follow-up, 37 (62%) patients had evidence of conduction disease on 12 lead ECG or Holter: 1st degree or higher AV block (35%, n=21), trifascicular block (6.7%, n=4), intraventricular conduction delay (32%, n=19), prolonged QTc (15%, n=9) and junctional rhythm (5% n=3). In addition to abnormalities of conduction, 27 (45%) patients had axis deviation and 12 (20%) abnormal repolarisation.

Abnormalities were present in 8 (14%) of those with an echocardiogram. 2 (3.5%) had hypertrophic cardiomyopathy. Other abnormalities included bicuspid aortic valve, aortic root dilatation, dyskinetic septal motion, pericardial effusion, mitral valve thickening and perimembranous VSD.

24 (40%) patients had a signal averaged ECG of which 14 (58%) were positive in 1 or more vector. 3 (5%) patients had an exercise test with no arrhythmia or progression of conduction abnormalities. 1 patient had an invasive EP study showing a prolonged HV interval but no inducible ventricular tachycardia.

Conclusions

There appears to be a high incidence of cardiac involvement in children with DM1. Adverse events (death and pacemaker implantation) are represented in our cohort. More studies are required in order to establish how we might better identify those at risk of progression of conduction disease and ventricular arrhythmia. Regular and lifelong cardiac follow up is advisable but risk stratification and device implantation remains challenging.