Mitral Regurgitation

· Moderate to severe MR is the most common valvular disease in the US

· The leading cause of MR in the developing world is rheumatic HD

· In the US, the most common cause  is degenerative, followed by ischemic MR

· MR can be classified into “functional” and “organic”:

· Functional MR implies that the valve leaflets are structurally normal, but MR results from dilation of the MV annulus due to ischemic changes (LV disease, causing tethering of the chordate and stretching of  the papillary muscles

· Organic MR can be due to ischemic disease, but only in the setting of papillary muscle rupture; otherwise it refers to actual valvular abnormalities from endocarditis, degenerative disease, rheumatic disease, inflammatory disease (SLE), etc.

· Presentation of MR can be acute or insidious.  Acute MR presents with symptomatic heart failure because the ventricles are not prepared to handle the sudden increase in volume load, but over time, the LV is able to dilate and remodel (eccentric hypertrophy); the LA also enlarges, allowing more regurgitant volume

· LV ejection fraction in chronic MR may be greater than normal because of the increase in preload and the afterload reducing effects of  the regurgitant flow in the LA.  Threfore LV EF can be overestimated, and misleading about the degree of LV dysfunction

· An EF of <60% in a patient with severe MR is a class I indication for mitral valve repair

 

 

Management of MR:

a) In acute setting, afterload reduction helps to reduce regurgitant flow into the low-pressure LA by decreasing SVR

      - If patient is unstable, intraaortic balloon counterpulsation can further augment afterload reduction

 

b) Definitive management is surgical, as no medical therapy has been shown to improve outcomes

      - Key is to perform intervention before LV becomes decompensated to the point where it will not respond even after surgical correction

      - Unfortunately, it is difficult to predict which patients will respond to surgery, but those with LV <30% and markedly dilated LVs have lower chance

      - In pts where MR is secondary to DCM, trial of medical therapy to see if reverse remodeling occurs and MR improves is reasonable

 

c) Mitral Valve Repair vs Mitral Valve Replacement:
When possible, Mitral Valve Repair is superior to replacement based on improved ventricular function and survival
Mortality in the former is~1% whereas it is 5% in the latter.

 

 

Society of Thoracic Surgeon’s risk model for valvular surgery.  This is a link to the online calculator: http://209.220.160.181/STSWebRiskCalc261/

 

 

(Ellen Eaton MD, 7/20/10)

(Christopher Woo MD, 9/3/10)

(Victoria Kelly MD, 3/17/11)