This clinical trial is focused on studying a heart condition called Symptomatic Obstructive Hypertrophic Cardiomyopathy, which is a disease where the heart muscle becomes abnormally thick, making it harder for the heart to pump blood. The study will evaluate a treatment called Mavacamten, which is taken as a capsule. The purpose of the study is to see how Mavacamten affects the heart’s ability to pump blood in adolescents aged 12 to under 18 years who have this condition.

Participants in the study will be randomly assigned to receive either Mavacamten or a placebo, which looks like the medication but does not contain the active ingredient. The study will last for several months, during which participants will take the capsules and have regular check-ups to monitor their heart health. The main focus will be on changes in the heart’s function, particularly in the area called the left ventricular outflow tract, which is often affected in this condition.

Throughout the study, doctors will assess various aspects of heart health, including how well the heart pumps blood and any changes in heart muscle thickness. The study will also look at how participants feel during physical activities and any side effects they might experience. The goal is to gather information on the effectiveness and safety of Mavacamten for treating Symptomatic Obstructive Hypertrophic Cardiomyopathy in young people.