Mitral Regurgitation
Definition
The backward flow of blood into the left atrium during systole; may be acute or chronic.
Etiology
Any abnormality(s) of the mitral valve apparatus:- Mitral annulus (e.g., dilatation, calcification)
- Mitral leaflets (e.g., prolapse, endocarditis, flail)
- Chordae tendineae (e.g., elongation, rupture)
- Papillary muscles (e.g., fibrosis, calcification, ischemia, rupture)
- Ventricular myocardium (e.g., ischemia, infarction)
Signs and Symptoms
- Fatigue
- Dyspnea upon exertion
- Orthopnea
- Palpitations
Complications
- Left ventricular volume overload with left ventricular dilatation
- Pulmonary hypertension
- Pulmonary edema (especially with acute mitral regurgitation)
- Congestive heart failure (due to increased left atrial pressure)
- Left atrial thrombus formation/systemic embolization
Cardiac Auscultation
- Blowing, high-pitched systolic murmur, heard best at the cardiac apex radiating to the axilla
- Third heart sound possible
Electrocardiogram
- May be normal in mild cases or in acute mitral regurgitation
- Left atrial enlargement
- Left ventricular hypertrophy
- Atrial fibrillation
- Right ventricular hypertrophy
Chest X-ray
- Heart size may be normal in mild cases or in acute regurgitation
- Cardiomegaly (due to left atrial and left ventricular enlargement in significant chronic mitral regurgitation
Cardiac Catheterization
- Right heart catheterization to determine pulmonary capillary wedge and pulmonary artery pressures (SPAP, MPAP, PAEDP)
- The degree of regurgitation is determined during ventriculography (injection of contrast into to the left ventricle) by observing reflux of the contrast into the left atrium
Treatment
- Valvular repair or replacement; ideally, surgery should be performed before there is clinical evidence of left ventricular failure.
M - Mode
- Left atrial enlargement
- Left ventricular enlargement
- Left ventricular volume overload pattern (defined as hyperkinesia of the left ventricular walls with left ventricular dilatation)
- Evidence of pulmonary hypertension
2-D
- Anatomic basis for the presence of mitral regurgitation (e.g. mitral annular calcification)
- Left atrial enlargement; LV enlargement with volume overload pattern
- Rapid sideways expansion of the left atrium in systole
- Increased LA/RA ratio (normal is 1:1)
- Abnormal systolic bowing of the interatrial septum
- Evidence of pulmonary hypertension
PW Doppler
- Increased mitral E velocity (>1.3 m/sec) may indicate significant regurgitation
- Determine the severity of the regurgitant jet by the mapping technique
- Determine the regurgitant fraction
- Determine the aortic valve/mitral valve ratio (< 1.0 may indicate significant regurgitation)
- Determine left ventricular diastolic filling pattern: Stage II (pseudonormal) or III is associated with significant mitral regurgitation)
- Obtain pulmonary venous inflow: diminished or reversed S wave and increased D wave may indicate significant regurgitation
CW Doppler
- Decreased velocity of the mitral regurgitant jet (< 4 m/sec) indicates an elevated left atrial pressure due to significant regurgitation
- Asymmetrical shape of the mitral regurgitation inflow velocity envelope indicates a rapid rise in left atrial pressure due to significant regurgitation
- Compare the regurgitant Doppler spectral display with the mitral inflow Doppler spectral display
Color Flow Doppler
- Determine jet area
- Determine regurgitant jet area/left atrial area
- Deter mine regurgitant jet width at the regurgitant orifice
- Determine proximal acceleration (flow convergence), which indicates 3+ or 4+ severity
- Determine proximal isovelocity surface area (PISA)
Guide for Quantitating the Severity of Mitral Regurgitation
Mild (grade 1+)
- Normal history, physical exam, EKG, and chest X-ray
- Normal left atrial and left ventricular dimensions by echo
- Normal peak velocity across mitral valve as recorded by PW Doppler
- Regurgitant fraction <20%
Moderate (grade 2+)
- Possible abnormal history, physical exam, EKG or chest X-ray
- Mild left atrial and left ventricular enlargement by echocardiography
- Normal peak velocity across the mitral valve by PW Doppler
- Complete mitral regurgitation envelope as recorded by CW Doppler
- Regurgitant fraction 20 to 30%
Moderately severe (grade 3+)
- Abnormal history, physical exam, EKG and/or chest x-ray
- Moderate to severe left atrial and left ventricular enlargement
- Left atrial dimension greater than right atrial dimension
- Systolic pulsation of the left atrium
- Abnormal high peak velocity across the mitral valve by PW Doppler
- Abnormal aortic valve peak velocity to mitral valve peak velocity ratio as recorded by PW Doppler
- Strong complete MR spectral envelope by CW Doppler
- Proximal acceleration present by color flow Doppler
- Wide, thick mitral regurgitation jet
- Significant incomplete closure of the mitral valve in the parasternal short axis view of the mitral valve as visualized by color flow Doppler
- Regurgitant fraction 30 to 50%
Severe (grade 4+)
- Abnormal history, physical exam, EKG and/or chest x-ray
- Etiology of mitral regurgitation causes complete lack of systolic coaptation of the mitral valve best visualized by 2-D Echo
- A short left ventricular ejection time and/or premature aortic closure
- Moderate to severe left atrial and left ventricular enlargement
- Abnormally high peak velocity across the MV by PW Doppler
- Abnormal aortic valve to mitral valve peak velocity ratio by PW Doppler
- Strong complete mitral regurgitation signal with the gray scale of mitral regurgitation darker than mitral inflow as visualized by CW Doppler
- Peak velocity of mitral regurgitation < 4 m/sec with asymmetrical spectral shape
- Isovolumic relaxation time <60 msec
- Proximal acceleration present by color flow Doppler
- Wide, thick mitral regurgitant jet as visualized by color flow Doppler
- Regurgitant jet area / left atrial area ratio > 40%
- Regurgitant fraction > 40%