Inclusion Criteria:
* Participants aged ≥ 18 years (participants enrolled retrospectively: at the time of initial mavacamten prescription), irrespective of gender.
* Participants who have initiated mavacamten (for whom enrolled retrospectively) or are scheduled to initiate mavacamten (for whom enrolled prospectively) based on clinical therapeutic needs.
* Diagnosed with obstructive hypertrophic cardiomyopathy (HCM) consistent with current American College of Cardiology Foundation/American Heart Association, European Society of Cardiology, and Chinese guidelines for diagnosis and treatment of patients with hypertrophic cardiomyopathy, i.e., satisfy criteria below:
* Has a documented diagnosis of HCM prior to enrollment, and
* Peak left ventricular outflow tract (LVOT) gradient ≥ 30 mmHg at rest or with provocation in the most recent medical record within 3 months prior to enrollment as assessed by echocardiography.
* Has documented left ventricular ejection fraction (LVEF) ≥ 55%, as measured by resting transthoracic echocardiography (TTE) in the most recent medical record within 3 months prior to enrollment.
* New York Heart Association (NYHA) class II or III symptoms in the most recent medical record within 3 months prior to enrollment.
* For participants enrolled retrospectively, essential baseline information\* and critical data\*\* must be traceable and available. At least one key follow-up time points\*\*\* is required for inclusion.
Note：
\* Essential baseline information, including age, gender, resting or provoked LVOT peak gradient, LVEF, indices of cardiac structure (e.g., maximum LV wall thickness, atrial and ventricular chamber size and volumes), as well as systolic and diastolic function, NYHA functional class.
* Critical data, including resting or provoked LVOT gradient, LVEF, cardiac structure, systolic and diastolic function, dose of mavacamten.
* Key follow-up time points: including weeks 4, 8, 12, 24, 36, 48, 72 and 96.
* Voluntary sign informed consent form. Note: For participants enrolled retrospectively, the most recent medical record within 3 months as mentioned in the above requirements refer to the most recent medical record within 3 months prior to the initial mavacamten prescription.
Exclusion Criteria:
* Known HCM phenocopy disease (e.g., Fabry disease, amyloidosis).
* Participants who are expected to undergo major cardiac surgery during the study.
* Prior treatment of obstructive HCM with invasive septal reduction (surgical myectomy or percutaneous alcohol septal ablation \[ASA\] or septal radiofrequency ablation) within 6 months prior to enrollment (participants enrolled retrospectively: within 6 months prior to initial mavacamten prescription); participants with an unsuccessful myectomy or percutaneous ASA or septal radiofrequency ablation performed \>6 months prior to enrollment (participants enrolled retrospectively: within 6 months prior to initial mavacamten prescription) may be enrolled.
* Currently treated with disopyramide or ranolazine (within 14 days prior to enrollment \[participants enrolled retrospectively: within 14 days prior to initial mavacamten prescription\]) or participants who are expected to be taking disopyramide, ranolazine, verapamil in combination with β-receptor blockers, or diltiazem in combination with β-receptor blockers during the study.
* Presence of other diseases that may affect completion of 96 weeks follow-up as assessed by the investigator.
* Participants who are using or are expected to be using moderate to strong CYP2C19 inhibitors/inducers, or strong CYP3A4 inhibitors, moderate to strong CYP3A4 inducers during the study.
* Participants who are participating in other interventional clinical studies.
