Mitral Regurgitation Diagnostic Approach

Initial Diagnostic Evaluation

The European Society of Cardiology recommends transthoracic echocardiography as the essential first diagnostic test to establish the diagnosis, classify MR as primary versus secondary, quantify severity, and assess left ventricular function and dimensions 1, 2, 3
Transthoracic echocardiography must be performed to determine whether MR is primary or secondary, quantify MR severity using multiple integrated parameters, assess left ventricular ejection fraction, left ventricular end-systolic dimension, and left ventricular end-diastolic dimension, and evaluate left atrial size and pulmonary artery pressures 1, 2, 3, 4, 5
Severity criteria for primary MR include vena contracta ≥7 mm, effective regurgitant orifice area ≥0.4 cm², regurgitant volume ≥60 mL/beat, regurgitant fraction ≥50%, and pulmonary vein systolic flow reversal 2, 3, 5, 6, 7
For secondary MR, lower thresholds define severity, including effective regurgitant orifice area ≥0.3 cm², regurgitant volume ≥45 mL/beat in low-flow conditions 2, 6

Transoesophageal echocardiography should be performed when transthoracic echocardiography is non-diagnostic or provides insufficient information, for pre-surgical planning, or for intraoperative guidance 2, 3
Cardiovascular magnetic resonance is indicated when uncertainty exists regarding LV volumes, LVEF, or MR severity on echocardiography, or when assessment of myocardial fibrosis is needed for prognostication 2, 6
Exercise stress testing or stress echocardiography should be performed in asymptomatic patients to unmask symptoms, in patients with symptoms equivocal or discordant with resting MR severity, and to assess dynamic changes in mitral gradient and pulmonary artery pressure 1, 3, 4

The European Society of Cardiology recommends specifically assessing for dyspnea on exertion and at rest, lower extremity edema and signs of fluid overload, exercise tolerance and functional capacity, and presence of arrhythmias, particularly atrial fibrillation 4, 5, 7
In asymptomatic severe primary MR, document new-onset atrial fibrillation, pulmonary artery systolic pressure >50 mmHg, LVEF ≤60% and/or LVESD ≥40 mm, and progressive LV dilatation or declining LVEF on serial imaging 3, 5, 6

For moderate MR, clinical evaluation should be performed every 6-12 months, and annual echocardiography should be performed 2, 4, 5
For severe MR, clinical evaluation should be performed every 6 months, and annual echocardiography should be performed 2, 4, 5
For asymptomatic severe MR, monitor for progressive increase in LV size or decrease in LVEF on ≥3 serial imaging studies, and consider complementary indices such as global longitudinal strain 6

Do not delay comprehensive echocardiographic assessment when MR is suspected, as severity determines urgency and type of intervention 1, 3
Avoid making intervention decisions in secondary MR before optimizing medical therapy, as severity may decrease substantially with appropriate heart failure management 4, 5, 7
Do not rely on a single echocardiographic parameter to grade severity; integrate multiple parameters for accurate assessment 2, 3
Recognize that murmur intensity does not correlate with MR severity, particularly in acute severe MR where left atrial pressure elevation may result in a low-intensity murmur 5
In patients with ischemic heart disease undergoing CABG, do not overlook concomitant moderate-to-severe MR, as combined intervention may be indicated 7