What is the diagnostic significance of a harsh systolic ejection murmur with a single S2 in pediatric patients?

In pediatric patients, a harsh systolic ejection murmur accompanied by a single S2 is particularly suggestive of Tetralogy of Fallot. This condition is characterized by four key heart defects: ventricular septal defect (VSD), pulmonary stenosis, right ventricular hypertrophy, and an over-riding aorta. The harsh systolic ejection murmur is primarily due to the outflow obstruction from the right ventricle to the pulmonary artery, which is caused by pulmonary stenosis. The single S2 occurs because of decreased blood flow through the pulmonary artery, leading to diminished closure sounds of the pulmonic valve when compared to the aortic valve.

In contrast to other conditions, such as aortic stenosis or coarctation of the aorta, which have different murmur characteristics and multiple heart sounds, Tetralogy of Fallot's anatomical arrangements lead specifically to the combinations of a harsh systolic ejection murmur and a single closure sound. This unique finding helps clinicians differentiate Tetralogy of Fallot from other potential diagnoses.