EM@3AM: Mitral Regurgitation

Author: Vivek Medepalli, MD (EM Resident Physician, UTSW / Parkland Memorial Hospital) // Reviewed by: Brit Long, MD (@long_brit, EM Attending Physician, San Antonio, TX), Colin Danko, MD (EM Attending Physician, UTSW / Parkland Memorial Hospital) and Alex Koyfman, MD (@EMHighAK, EM Attending Physician, UTSW / Parkland Memorial Hospital)

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Answer: Mitral Regurgitation

Epidemiology:

• Primary mitral regurgitation secondary to valvular disease occurs in 1.5-3% of the population ^[1,2]
  • Most commonly due to mitral valve prolapse in developed countries and rheumatic heart disease in developing countries ^[3]
• Prevalence of mitral regurgitation during cardiac catheterization in the setting of acute MI is 9-13% ^[4]
  • Moderate-to-severe regurgitation in 3-4% of acute MI patients
• Mitral regurgitation seen in 38% of patients with dilated cardiomyopathy
• More common in males

Etiology:

• Primary Mitral Regurgitation ^[3,5]
  • Degenerative mitral valve disease (ex. Mitral valve prolapse)
  • Rheumatic heart disease
  • Endocarditis
  • Trauma
  • Congenital malformations
  • Drug-related valvular disease (ex. Cabergoline, bromocriptine)
• Secondary Mitral Regurgitation ^[3,5]
  • Coronary artery disease
  • Acute myocardial infarction (ruptured papillary muscle)
  • Dilated cardiomyopathy
  • Hypertrophic cardiomyopathy

Pathophysiology:

• Acute Mitral Regurgitation: Commonly seen with acute MI, chordae tendinae rupture, endocarditis, and trauma^[2,5]
  • Regurgitant flow through diseased mitral valve leads to systolic backflow into the left atrium
  • Subsequent backflow into the pulmonary circulation leads to pulmonary edema and sudden-onset shortness of breath
  • Pulmonary hypertension leads to backflow into venous circuit, resulting in JVD, hepatomegaly, peripheral edema
  • Decreased filling of left ventricle leads to decreased forward flow, resulting in hypotension and cardiogenic shock
• Chronic Mitral Regurgitation: ^[2,5]
  • Changes occur more slowly, leading to eccentric hypertrophy and dilation of the left atrium
  • Chronic left atrial dilation can lead to atrial fibrillation

Clinical Features:

• Acute Mitral Regurgitation: ^[6]
  • Sudden-onset pulmonary edema and hypotension
  • Cardiogenic shock
  • Physical exam will show pulmonary rales, peripheral edema, JVD, hepatomegaly, S3, hyperdynamic cardiac apex
    • Classic murmur described as holosystolic, most prominent over the cardiac apex, and radiating to the axilla
      • Only present in 50% of cases; however, absence of murmur does not exclude acute mitral regurgitation ^[2,7]
•  Chronic Mitral Regurgitation
  • Majority of patients have mild regurgitation at baseline, which is often asymptomatic or associated with mild dyspnea ^[7]
  • Some patients with mild symptoms at rest can have profound acute regurgitation with exercise, resulting in acute pulmonary edema ^[3,8]

Evaluation:

• Transthoracic Echocardiogram:
  • Recommended to evaluate the presence, etiology, severity, and further hemodynamic consequences of the regurgitation ^[3,10]
    • Often shows an elevated ejection fraction (>60%) due to forward flow into the systemic circulationcombined with backflow into the left atrium ^[10]
    • Since regurgitant lesions tend to overestimate LV function, the absence of hyperdynamic function is concerning for impaired function
  • Color doppler shows backward flow into the left atrium
  • Consider transesophageal echocardiogram in patients with inconclusive transthoracic echocardiogram

• Chest X-Ray
  • May show cardiomegaly, enlarged left atrium, or pulmonary edema in symptomatic patients ^{[2, 6]}

• EKG
  • Will not show changes strictly due to mitral regurgitation acutely, but may reveal underlying cardiac ischemic event as source of symptoms
  • May reveal left atrial enlargement (biphasic P waves) or left ventricular hypertrophy in the setting of chronic mitral regurgitation ^[6]
• Supplemental laboratory evaluation: tailor to patient’s clinical presentation
  • Troponins if ACS is suspected
  • Blood cultures if the patient has clinical signs of endocarditis
  • Pro-BNP is often elevated and nonspecific

Treatment:

• Severe acute mitral regurgitation typically requires emergent surgical valve repair or replacement ^[6]
• Volume overload and hypertension worsen regurgitation
• Patients are afterload sensitive; the goal blood pressure is the lowest value that provides organ perfusion
• Volume overload but perfusing
  • Decreasing afterload reduces regurgitant flow and increases cardiac output
    • Utilize dihydropyridine calcium channel blockers such as nicardipine or clevipidine; nitroglycerin may also be used
  • Preload reduction assists with gas exchange and cardiac function
    • Utilize nitroglycerin infusion with titration
    • Noninvasive positive pressure ventilation (NIPPV) and diuretics may be used
  • Target slightly higher heart rates, as slow heart rates increase regurgitant flow
• Volume overload but poor perfusion
  • Provide inotropic support while maintaining mean arterial pressure
    • Start epinephrine infusion, or use dobutamine (be ready with norepinephrine)
    • Milrinone can be used in the ICU
  • Preload reduction
    • Use NIPPV
  • HR control; avoid bradycardia and severe tachycardia
    • If significantly tachycardic, use amiodarone or even IV digoxin
•  Emergent consultation recommended to interventional cardiology and cardiothoracic surgery
  • Mechanical circulatory support may be used as a bridge to surgery
• In the setting of ACS, prompt revascularization therapy is indicated
  • May be sufficient to reverse acute mitral regurgitation not caused by chordae tendinae or papillary muscle rupture ^[6]
• If patient has clinical signs of endocarditis, start broad spectrum antibiotic therapy

Consultation:

• Cardiology/Interventional Cardiology
• Cardiothoracic Surgery

Disposition:

• Mild-to-moderate symptomatic mitral regurgitation with hemodynamic stability can be admitted to floor/ward with telemetry capabilities ^[6]
• Severe mitral regurgitation may require ICU admission and/or emergent surgical repair

Summary and Pearls:

• The most common cause of primary mitral regurgitation is prior structural valve disease (ex. Mitral valve prolapse) and secondary mitral regurgitation is ischemic heart disease
• Acute mitral regurgitation presents with sudden onset dyspnea, JVD, peripheral edema
• The diagnostic modality of choice is transthoracic echocardiogram (TTE); EKG and laboratory markers can provide supplementary information to reveal etiology
• Mild to moderate mitral regurgitation can be managed with symptomatic medical therapy, while severe valve disease requires ICU admission and possible emergent surgical valve repair or replacement

References