Costello syndrome (CS) and Cardiofaciocutaneous syndrome (CFCS) are both RASopathies, a group of developmental disorders caused by a mutation in genes encoding in the RAS/MAPK pathway. RASopathies are prone to cardiac malformations and sudden cardiac death. Description of electrocardiographic findings in these patients is rare. The objective of this study was to describe electrocardiogram and correlation with echocardiographic findings in a cohort of CS and CFC.

A 12-lead electrocardiogram (ECG) and a trans-thoracic echocardiography (TTE) were performed for all patients during the same period in July 2016, and were analyzed by two different cardiologists.

Twenty-four patients were included, 14 with CFCS and 10 with CS. The mean age was 10.3±7.0 years. In 14 patients (58%), at least one abnormality was noticed on the electrocardiogram: axis deviation in 11 patients (46%); atrial hypertrophy in 5 patients (21%); left ventricular hypertrophy in 2 patients (8%); incomplete bundle-branch block in 3 patients (13%) and a significant Q-wave in 5 patients (21%). All patients with left axis deviation and/or left ventricular hypertrophy at ECG had a hypertrophic cardiomyopathy (sub-aortic septal, apical or concentric hypertrophy) on TTE. The patients with a significant Q wave (among them 2 had an extreme right axis deviation) had in fact a minimal hypertrophic cardiomyopathy (septal thickness<3 Z-score), suggesting the presence of myocardial fibrosis. Despite a normal ECG, 5 patients had a hypertrophic cardiomyopathy at TTE. Finally, 5 patients (21%) had a morphologically normal heart at TTE and all had a normal ECG.

Significant Q-wave or extreme right axis deviation on the ECG may suggest the potential presence of myocardial fibrosis. Detection of fibrosis by MRI may play an important role for the risk stratification of sudden cardiac death in these patients.