Mitral regurgitation resident survival guide
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Raviteja Guddeti, M.B.B.S. [2]
Overview
Mitral regurgitation is a disorder of the valve of the heart present between the left atrium and left ventricle. Blood from the left ventricle enters the left atrium along with aorta, because of the incompetence of the mitral valve (dual outlet left ventricle).
Classification
Mitral regurgitation can be acute or chronic. Acute mitral regurgitation causes sudden overload of the left atrium and left ventricle and can cause pulmonary congestion. Chronic regurgitation develops over months to years and in this phase the left ventricle develops eccentric hypertrophy in order to compensate for the pressure changes in the heart and if decompensated the left ventricle enters a dysfunctional phase. Long standing volume overload on the left ventricle causes left ventricle to dysfunction.
Causes
Mitral regurgitation (MR) can be caused by either the valve or the ventricle.
Valvular mitral regurgitation is caused by
- Degenerative
Ventricular cause of mitral regurgitation is otherwise called functional MR and it is caused by:
Natural History
Natural history of mitral regurgitation is dictated by the etiology.
- Papillary muscle rupture and deihisced mitral valve prosthesis - poor prognosis without surgery.
- Endocarditis - response to antibiotics decides the natural history and progression of mitral regurgitation.
- Chordal rupture - depends on tolerance of severe MR.
Patients with normal left ventricular function and severe acute pulmonary edema are supposed to have severe MR.
Diagnosis
Symptoms
- Acute miral regurgitation presents with the following symptoms:
- Chronic mitral regurgitation may have a prolonged asymptomatic interval phase before the heart enters a decompensated phase where the patient may have the symptoms of low cardiac output and pulmonary congestion. By the time symptoms develop, left ventricular dysfunction may have already occurred.
Physical Examination
- S3 and S4 may be heard on auscultation.
- A holosystolic murmur is heard in the apex region of the heart and radiating to the axilla. MR murmur may be soft, short and even absent. 70% papillary muscle rupture cases have no murmur.
Imaging
- Transthoracic echocardiography (TTE). Three important points that are to be considered while doing an ECHO assessment include:
- How does it affect the left ventricle ?
- What causes it ?
- How much is there ?
In mitral valve prolapse the valve leaflets go into the left atrium. Te eccentric jet is away from the abnormal leaflet.
Coaptation in left ventricle jet hugs posteriorly is seen in ischemic mitral regurgitation.
Echocardiographic findings to quantify the severity of mitral regurgitation include:
- Regurgitant volume - (>60 ml)
- Regurgitant fraction - (>55%)
- Effective regurgitant orifice (ERO) (ratio of regurgitant flow volume to the velocity of the mitral insufficiency jet (ERO = Flow / Velocity)) - (>0.4 cm2)
All the three factors mentioned above are better parameters to quantify severity than color jet area.
- If the left ventricular and left atrial sizes are normal on an ECHO mitral regurgitation is not severe.
- Central jets indicate normal mitral valve and therefore not severe.
- Wide eccentric jets indicate that the regurgitation is severe.
Echocardiographic findings must match the symptoms.
TTE can underestimate the clinical picture in patients with clinical signs of severe and mild MR. In that circumstances it is imperative to get a TEE or a cardiac catheterization.
If TTE is negative transesophageal echocardiography (TEE) or cardiac catheterization are the preferred diagnostic imaging modalities.