Patients with HOCM and severe LVOT obstruction can remain asymptomatic while significant cellular and structural changes of the heart (adverse remodeling) may occur preceding heart failure and rhythm disorders. Hence, preventing adverse remodeling through LVOT desobstruction may have significant impact on cardiac function and geometry in this particular population, as it is in symptomatic patients.

The investigators will assess functional and structural characteristics of the myocardium in asymptomatic vs. symptomatic patients with severe LVOT obstruction before and after PTSMA, using advanced imaging studies with LGE-CMR and echocardiography.

The trial consists of three cohorts

1. Symptomatic HOCM patients with severe LVOT obstruction undergoing PTSMA (reference group)
2. Asymptomatic HOCM patients with severe LVOT obstruction undergoing PTSMA (study group)
3. Asymptomatic HOCM patients with severe LVOT obstruction with no intervention (observation group)

Inclusion Criteria:

• Age > 40 yrs
• HOCM diagnosed by experienced cardiologists (European Society of Cardiology (ESC)-certified imaging cardiologists and/or finalized fellowship imaging)
• LVOT obstruction >30 mmHg pressure gradient in rest, or >50 mmHg during exercise by TTE and/or invasive measurement, performed experienced (imaging) cardiologists
• Symptomatic (NYHA class >2 or CCS class >2)
• Asymptomatic: free of any dyspnea/chest pain or discomfort associated with LVOT obstruction

Exclusion Criteria:

• LV wall thickness <15 mm
• Other conditions responsible for hypertrophy (e.g. hypertension, aortic valve disease)
• Moderate to severe mitral valve regurgitation
• Systolic anterior motion of the mitral valve
• Coronary artery disease requiring intervention
• Pregnancy

Technicians and/or imaging cardiologists involved in image analysis will not be informed about the procedure in order to have an unbiased analysis at baseline. At follow-up, treated patients will have akinetic/infarcted proximal septum that will be noticed during image acquisition. However, the pre-PTSMA status (symptomatic vs. asymptomatic) will be blinded for the analysis.