Inclusion Criteria:
* Participants aged ≥ 18 years (participants enrolled retrospectively: at the time of initial mavacamten prescription), irrespective of gender.
* 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 unexplained left ventricular (LV) hypertrophy with non-dilated ventricular chambers in the absence of other cardiac (e.g., hypertension, aortic stenosis) or systemic disease and with maximal LV wall thickness ≥ 15 mm (or ≥ 13 mm with positive family history of hypertrophic cardiomyopathy) in the most recent medical record within 3 months 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.
* Participants who have initiated mavacamten (for whom enrolled retrospectively) or are scheduled to initiate mavacamten (for whom enrolled prospectively) based on clinical therapeutic needs.
* For participants enrolled retrospectively, must have traceable essential baseline information (including age, gender, resting LVOT peak gradient, Valsalva LVOT peak gradient, LVEF, indices of cardiac structure, systolic and diastolic function, cardiac biomarkers, NYHA functional class) and critical data (including resting and Valsalva LVOT gradient, LVEF, cardiac structure, systolic and diastolic function, dose of mavacamten) at key follow-up time points that have been completed.
* Voluntary sign informed consent form.
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.
