Adult Echocardiography Practice Exam

When a left ventricular outflow tract obstruction is found in patients under 30, which etiology is most likely?

1. Myxomatous valve disease

2. Unicuspid valve

3. Rheumatic valve disease

4. Bicuspid valve

The correct answer is: Unicuspid valve

In patients under 30 years of age, the most likely etiology for left ventricular outflow tract obstruction is a unicuspid valve. This congenital condition can lead to significant obstruction due to abnormal valve development, which can manifest early in life. The unicuspid aortic valve is characterized by a single functional leaflet instead of the typical three, leading to increased systolic gradient and resultant outflow tract obstruction. Other conditions such as bicuspid aortic valve can also cause left ventricular outflow tract obstruction, but they are more commonly associated with older patients, often presenting later in life with complications such as aortic stenosis. Myxomatous degeneration and rheumatic heart disease are more prevalent in an older population as well, with the latter being a result of rheumatic fever that also presents more frequently in older demographics. Thus, while they can cause left ventricular outflow tract obstruction, they are less likely to be the underlying cause in younger patients. This context surrounding the conditions helps clarify why unicuspid valve should be considered the primary etiology in this age group when assessing for left ventricular outflow tract obstruction.