Right ventricular outflow tract obstruction differential diagnosis

Associate Editor-In-Chief: ; Keri Shafer, M.D. [mailto:kshafer@bidmc.harvard.edu]

Right ventricular outflow tract obstruction must be distinguished from several other conditions.

Differential Diagnosis
1. Atrial septal defect: Also has a systolic ejection murmur, wide fixed split S2, EKG showing RVH. In ASD the split of the S2 is fixed, there is no ejection click.

2. Small Ventricular septal defect: Amyl nitrate increases venous return and increases the murmur of pulmonary stenosis, in VSD the murmur becomes softer.

3. Mild left-sided outflow obstruction: With valsalva maneuver the murmur of aortic stenosis becomes softer after about 5 beats, with pulmonary stenosis it becomes softer within 3 beats.

4. Acyanotic or pink tetralogy of Fallot: with amyl nitrate and increased venous return the murmur of PS increases, and the murmur of tetralogy decreases because of peripheraldilation and an increase in right to left shunting.