Left Ventricular Outflow Obstruction

Aka: Left Ventricular Outflow Obstruction, Left Ventricular Outflow Tract Obstruction, LVOTO

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II. Pathophysiology

  1. Left Ventricular Outflow Obstruction (LVOTO) occurs with conditions that impair left ventricular filling
  2. LVOTO results in decreased Stroke Volume, Cardiac Output and Cardiogenic Shock
  3. Secondary Mitral Regurgitation may occur as the mitral valve is pulled toward obstruction
    1. May increase left atrial pressures and result in Acute Pulmonary Edema

III. Causes

  1. Critically ill patients
    1. Hypovolemia leads to narrowing of the left ventricular outflow tract
    2. Tachycardia leads to decreased diastolic filling (decreased time in diastole)
  2. Hypertrophic Cardiomyopathy (HOCM)
    1. Abnormally thickened Myocardium and abnormal mitral valve movement impair filling
  3. Subaortic Stenosis
  4. Bicuspid Aortic Valve stenosis
  5. Supravalvular Aortic Stenosis (SVAS)
    1. Rare condition, associated with Williams Syndrome (most common), as well as Familial Hypercholesterolemia
  6. Aortic Coarctation
  7. Hyperdynamic left ventricle
  8. Systolic anterior motion of the mitral valve (SAM)
    1. May complicate Mitral valve regurgitation or Mitral Valve Prolapse
    2. Mitral valve lodges in the left ventricular outflow tract resulting in mechanical obstruction

IV. Findings

  1. Presentations
    1. Cardiogenic Shock
    2. Syncope or Near Syncope
    3. Hypotension
  2. Clinical Clues
    1. Tachycardic, hypotensive patients who worsen with Vasopressors or inotropes (due to increased Tachycardia)
    2. Cardiogenic Shock that worsens with Diuretics and Nitroglycerin

V. Differential Diagnosis

  1. See Cardiogenic Shock

VI. Imaging

  1. Echocardiogram (PLAX View)
    1. Left ventricle hyperdynamic and small
    2. Myocardium or septum may be thickened (Cardiomyopathy)
    3. Mitral Regurgitation may be present
      1. Color Doppler Ultrasound
      2. Mitral valve motion in systole
    4. Measurements consistent with Left Ventricular Outflow Obstruction (LVOTO)
      1. Left ventricle diastolic diameter <2.2 cm
      2. Continuous-Wave Doppler (CWD) with high-velocity, late-peak
      3. LVOT gradient >30 mmHg

VII. Management: Acute Emergent

  1. Early, emergent cardiology Consultation
  2. Stabilize Hypotension
    1. Intravenous Fluids
      1. Expand left ventricle with Preload
      2. Slows Heart Rate, increasing diastolic filling time
    2. Vasopressors
      1. Peripheral Vasoconstrictors (e.g. Vasopressin, Phenylephrine) are preferred
      2. Avoid inotropes (increase Heart Rate and contractility) that worsen obstruction
  3. Manage Tachydysrhythmias
    1. Synchronized Cardioversion for Atrial Fibrillation with Rapid Ventricular Rate
    2. Consider Esmolol to slow Tachycardias
  4. Other measures
    1. Avoid initial diuresis (decreases Preload)

VIII. Resources

  1. Left Ventricular Outflow Obstruction (Internet Book of Critical Care, Dr. Farkas)
    1. https://emcrit.org/ibcc/lvoto/
  2. Left Ventricular Outflow Obstruction (StatPearls)
    1. https://www.ncbi.nlm.nih.gov/books/NBK470446/

IX. References

  1. DeMeester and Swaminathan (2024) EM:Rap, 9/2/2024
  2. Mallemat and Swaminathan (2024) Crit Bits: Left Ventricular Outflow Obstruction, EM:Rap 11/11/2024

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