Electrocardiographic Changes with Age in Japanese Patients with Noonan Syndrome

Abstract

Little information is available on age-related electrocardiographic changes in patients with Noonan syndrome. This single-center study evaluated the electrocardiograms of patients with Noonan syndrome. We divided the patients (n = 112; electrocardiograms, 256) into four groups according to age: G1 (1 month-1 year), G2 (1-6 years), G3 (6-12 years), and G4 (>12 years). Typical Noonan syndrome-related electrocardiographic features such as left-axis deviation, abnormal Q wave, wide QRS complex, and small R wave in precordial leads were detected. A high percentage of QRS axis abnormalities was found in all groups. Significant differences in right-axis deviation (RAD) were noted among the groups: 56.5% of G1 patients showed RAD compared with 33.3% of G2, 21.1% of G3, and 19.2% of G4 patients. The small R was also significantly different among the groups: 32.6% of G1 patients showed a small R wave compared with 14.9% of G2, 8.5% of G3, and 15.4% of G4 patients. Of the 53 patients with Noonan syndrome aged 1 month to 2 years, 18 had T-positive V1 with a higher prevalence of pulmonary stenosis and cardiac interventions. QRS axis abnormalities, small R in V6, and T-positive V1 could help diagnose Noonan syndrome in infants or young children.

Keywords: Noonan syndrome; T-positive V1; electrocardiogram; right-axis deviation; small R.

Figure 1

Electrocardiogram (speed 25 mm/s, voltage 0.1 mV/mm) of a 10-year-old patient with Noonan syndrome with pulmonary stenosis and atrial septal defect.

Figure 2

Percentage of electrocardiogram findings by age group. RAD, right-axis deviation; LAD, left-axis deviation; RBBB, right bundle branch block; abnormal Q, abnormal Q wave; Small R wave, small R wave in V6. * p < 0.05 was considered significant.