Inclusion Criteria:

• 1. Willingness and ability to provide written informed consent
• 2. Willingness and ability to comply with scheduled visits and study procedures
• 3. Male or female, aged 18-85 years
• 4. Diagnosed with obstructive hypertrophic cardiomyopathy according to presence of a left ventricular wall thickness of ≥15 mm that is otherwise unexplained by abnormal loading conditions (e.g., hypertension, valvular, congenital disease) or infiltrative cardiomyopathies. Unexplained left ventricular wall thickness of ≥13 mm is sufficient for diagnosis in relatives of individuals with hypertrophic cardiomyopathy or those who are genotype positive.
• 5. Has been prescribed mavacamten consistent with US Prescribing Information
• 6. Ability and intention to adhere to oral mavacamten therapy as prescribed by treating physician for the duration of study participation
• 7. For females of reproductive potential: negative pregnancy test at screening/baseline and 12 month visits.

Exclusion Criteria:

• 1. Pregnancy or lactation
• 2. Known hypersensitivity to components of mavacamten or regadenoson
• 3. Prior treatment with mavacamten or aficamten
• 11. Over weight limit for imaging gantry. 12. To minimize the risk of participants undergoing PET/CT with inadequate image quality, participants with left ventricular systolic dysfunction or lung disease will be excluded.