Primary mitral regurgitation (MR) is a frequent disease that can ultimately lead to heart failure. Primary MR represents the second most prevalent cause of cardiac valve surgery in high income countries. Progressive myocardial fibrosis due to chronic volume overload is recognized as a pathophysiological substrate of altered LV function in primary MR. As fibrosis leads to increased myocardial stiffness, ultrasound mechanical wave propagation measurements within the myocardium could provide important clinical information. Natural mechanical wave velocity (MWV) imaging, using High-frame-rate (HFR) echocardiography has emerged as a promising tool to evaluate myocardial stiffness.

The objective is study is to evaluate the correlation between the LV myocardial stiffness (as assessed by 3D ultrasound myocardial MWV mapping) and myocardial interstitial fibrosis as measured using CMR (myocardial extracellular volume measure)

After being informed about the study. All patients giving written informed consent will undergo in a routine practice:

1. echocardiography (2D/3D),
2. CMR imaging,
3. electrocardiogram 24 hours monitoring,
4. blood sampling including brain natriuretic peptide measurement,
5. symptom-limited combined exercise echocardiography and oxygen uptake measurements

Inclusion Criteria:

• Severe primary MR patients (effective regurgitation orifice area ≥ 40mm²) with class I indication for surgery (symptoms and/or altered conventional parameters of LV function) (n=10 patients)
• Severe primary MR patients (effective regurgitation orifice area ≥ 40mm²) without class I indication of surgery (n=20 patients)
• Mild to moderate primary MR patients as defined by effective regurgitation orifice area ≥ 20mm² and < 40mm² (n=10 patients)

Exclusion Criteria:

• Permanent atrial fibrillation
• Acute primary severe MR
• Secondary MR
• Previous cardiac surgery of any kind
• Other severe left sided valvular disease
• Coronary artery disease
• Congenital cardiac disorder

The study will include adult patients with chronic primary mitral regurgitation who have been referred to our tertiary cardiology center as part of their routine care. These are the typical patients with chronic primary mitral regurgitation whom we aim to better phenotype using the new 3D ultrasound mapping technology for MWV (mechanical wave velocity).