Cardiac function in congenital hypothyroidism: Impairment and response to L-T4 therapy

Electrocardiograms (heart rate, QRS voltage, QRS axis in the frontal plane, Q-Tc interval), echocardiograms [left ventricular fractional shortening (LVFS); preejection period (PEP); PEP/left ventricular ejection time (PEP/LVET) ratio; end-diastolic left ventricular free wall and interventricular septum thickness; presence of pericardial effusion], and thyrotropin (TSH), thyroxine (T₄), and triiodothyronine (T₃) serum levels were evaluated before and 1 week, 1 and 2 months after the start ofl-thyroxine (L-T₄) therapy in 11 infants with congenital hypothyroidism (CH), aged 16–59 days when first seen.