Mitral Regurgitation: Murmur, Pathophysiology, and Treatment

Mitral regurgitation (formerly called mitral insufficiency) results in a volume load on the heart (increases preload) and reduces afterload. The result is an enlarged LV with an increased ejection fraction (EF). Over time, the stress of the volume overload reduces myocardial contractile function; when this occurs, there is a drop in ejection fraction and a rise in end-systolic volume. Mitral regurgitation may arise from any portion of the complex valve apparatus ( such as leaflets, annulus, chordae, papillary muscles, or LV free wall) and may present acutely or chronically.

Pathophysiology of Mitral insufficiency

  • Acute
    • Abrupt elevation of left atrial pressure in the setting of normal LA size and compliance, causing backflow into pulmonary circulation with resultant pulmonary edema.
    • As cardiac output decreases because of decreased forward flow, hypotension and shock can occur
  • Chronic
    • Gradual elevation of left atrial pressure in the setting of dilated LA and LV (with increased left atrial compliance)
    • LV dysfunction occurs due to dilation
    • Pulmonary HTN can result from chronic backflow into pulmonary vasculature

Causes of Mitral insufficiency

  • Acute
    • Endocarditis (most often Staphylococcus aureus)
    • Papillary muscle rupture (from infarction) or dysfunction (from ischemia)
    • Chordae tendineae rupture
  • Chronic
    • Mitral valve prolapse (MVP)
    • Rheumatic fever
    • Marfan syndrome
    • Cardiomyopathy causing dilation of mitral annulus

Prognosis

  • The acute form is associated with much higher mortality
  • Survival is related to extent of Left Ventricular cavity dilation

Clinical Features of Mitral regurgitation

  • Symptoms
    • Dyspnea on exertion, PND, orthopnea
    • Palpitations
    • Pulmonary edema
  • Signs
    • Mitral regurgitation murmur is Holosystolic (starts with S1 and continues on through S2) at the apex, which radiates to the back or clavicular area, depending on which leaflet is involved
    • AFib is a common finding
    • Other findings: Diminished S1, widening of S2, S3 gallop; laterally displaced PMI; loud, palpable P2 and typical mitral regurgitation murmur

Characteristics of Mitral Regurgitation murmur

Mitral regurgitation murmur
Characteristics of Mitral Regurgitation murmur

Diagnosis

  • CXR findings: Cardiomegaly, dilated LV, pulmonary edema.
  • Echocardiogram: MR; dilated LA and LV; decreased LV function. It should be performed serially in patients with known Mitral regurgitation

Treatment

  • Medical
    • Afterload reduction with vasodilators is recommended for symptomatic patients only; they are not recommended in most asymptomatic patients as they may mask the progression of the disease
    • Chronic anticoagulation if the patient has AFib
    • IABP can be used as a bridge to surgery for acute MR (decreases afterload and favors normal flow, not regurgitant flow)
  • Surgical
    • Mitral valve repair (preferred) or mitral valve replacement.

Indication for Surgery

Acute Mitral regurgitation
Chronic symptomatic Mitral regurgitation
Asymptomatic MR with LVEF <60% or LV end-systolic diameter >40 mm
Pulmonary Hypertension caused by MR
New-onset Atrial Fibrillation
Chronic severe primary MR when another cardiac surgery is planned.

Remember

Mitral regurgitation resulting from ischemia-induced dysfunction of the papillary muscle should improve after appropriate revascularization.

References

  1. https://semanticscholar.org/paper/43d99e403a99c644e217c802fe4c190afac86f9c

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