Effect of Mavacamten Treatment on Coronary Flow Reserve in oHCM

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.