Which test is helpful to detect regions of localized hypertrophy and LV outflow tract obstruction in hypertrophic cardiomyopathy that may be missed by echocardiography?

• A. Echocardiography
• B. CMR
• C. CT Angiography
• D. Nuclear Stress Test

Answer: (B)

In hypertrophic cardiomyopathy, thickening can be regional and may occur in areas not well visualized by ultrasound windows. Cardiac magnetic resonance imaging provides complete, high-resolution images of the entire left ventricle, allowing precise measurement of wall thickness in all segments and the ability to detect focal or apical hypertrophy that echocardiography can miss. It also visualizes the dynamic behavior of the LV outflow tract across the cardiac cycle and can quantify the obstruction with phase-contrast flow imaging. Additionally, MR offers tissue characterization, such as fibrosis, which adds prognostic information. CT angiography mainly maps anatomy of the coronaries and chambers and lacks the detailed tissue characterization and dynamic functional assessment, while nuclear stress testing focuses on perfusion and wall motion under stress rather than detailed structural and outflow tract evaluation. Therefore, cardiac magnetic resonance is the most helpful test for identifying localized hypertrophy and LVOT obstruction that may be missed by echo.