Electrocardiography in Noonan syndrome PTPN11 gene mutation--phenotype characterization

Noonan syndrome is a developmental disorder with distinctive facial features, short stature and cardiac abnormalities. In this cross-sectional study, we evaluated characteristic electrocardiographic (ECG) findings and cardiac abnormalities in 84 patients with Noonan syndrome, 56 (67%) of who were positive for a PTPN11 mutation. As reported previously, pulmonary stenosis was the most common cardiac abnormality, followed by atrial septal defect and hypertrophic cardiomyopathy. The ECG showed at least one characteristic finding in 50% of cases including left axis deviation in 38 (45%), small R waves in the left precordial leads in 20 (24%) and an abnormal Q wave in 5 (6%) patients with Noonan syndrome. A wide QRS complex was not detected in any of these patients. The characteristic ECG findings of Noonan syndrome patients were not associated with a PTPN11 gene mutation, or with a (specific) cardiac anomaly. We conclude that there are characteristic ECG findings in Noonan syndrome, but the ECG pattern is neither a useful tool for the phenotype characterization of a PTPN11 mutation, nor for the presence or type of cardiac abnormality.