['Williams syndrome (WS) is a congenital, multisystem developmental disorder affecting 1 in 8000 live births. Cardiovascular abnormalities are present in 80% of WS patients. The present study sought to characterize fully the electrocardiographic findings in WS and correlate findings with anatomic pathology.', "A retrospective review was performed of the electrocardiograms (ECGs) of patients with WS evaluated at the Children's Hospital of Philadelphia from January 1, 1980 through December 31, 2007. When available, the five most recent ECGs in each patient were evaluated. Ventricular hypertrophy was diagnosed based on previously reported voltage criteria in normal populations.", 'There were 187 patients with 499 ECGs for evaluation. Median age at study ECG was 8.0 years (range 0.1-58.9); median number of ECGs per patient was 2.7 (range 1-5). Heart rate, PR interval, and QRS interval were normal for age. Right ventricular hypertrophy (RVH) was present on 44% (219/499) of ECGs. Left ventricular hypertrophy (LVH) was present on 30% (150/499) of ECGs. Fifty-seven percent (106/187) of subjects had ≥1 ECG demonstrating RVH, and 39% (72/187) had ≥1 ECG demonstrating LVH. The severity of right- and left-sided obstructive lesions correlated with the ECG presence of RVH (P < .0001, odds ratio 21.8) and LVH (P < .001, odds ratio 14.5-61), respectively.'] Does ventricular Hypertrophy on Electrocardiogram correlate with Obstructive Lesion Severity in Williams Syndrome?