II. Pathophysiology
- Left Ventricular Outflow Obstruction (LVOTO) occurs with conditions that impair left ventricular filling
- LVOTO results in decreased Stroke Volume, Cardiac Output and Cardiogenic Shock
- Secondary Mitral Regurgitation may occur as the mitral valve is pulled toward obstruction
- May increase left atrial pressures and result in Acute Pulmonary Edema
III. Causes
- Critically ill patients
- Hypovolemia leads to narrowing of the left ventricular outflow tract
- Tachycardia leads to decreased diastolic filling (decreased time in diastole)
-
Hypertrophic Cardiomyopathy (HOCM)
- Abnormally thickened Myocardium and abnormal mitral valve movement impair filling
- Subaortic Stenosis
- Bicuspid Aortic Valve stenosis
- Supravalvular Aortic Stenosis (SVAS)
- Rare condition, associated with Williams Syndrome (most common), as well as Familial Hypercholesterolemia
- Aortic Coarctation
- Hyperdynamic left ventricle
- Systolic anterior motion of the mitral valve (SAM)
- May complicate Mitral valve regurgitation or Mitral Valve Prolapse
- Mitral valve lodges in the left ventricular outflow tract resulting in mechanical obstruction
IV. Findings
- Presentations
- Clinical Clues
- Tachycardic, hypotensive patients who worsen with Vasopressors or inotropes (due to increased Tachycardia)
- Cardiogenic Shock that worsens with Diuretics and Nitroglycerin
V. Differential Diagnosis
VI. Imaging
-
Echocardiogram (PLAX View)
- Left ventricle hyperdynamic and small
- Myocardium or septum may be thickened (Cardiomyopathy)
- Mitral Regurgitation may be present
- Color Doppler Ultrasound
- Mitral valve motion in systole
- Measurements consistent with Left Ventricular Outflow Obstruction (LVOTO)
- Left ventricle diastolic diameter <2.2 cm
- Continuous-Wave Doppler (CWD) with high-velocity, late-peak
- LVOT gradient >30 mmHg
VII. Management: Acute Emergent
- Early, emergent cardiology Consultation
- Stabilize Hypotension
- Intravenous Fluids
- Expand left ventricle with Preload
- Slows Heart Rate, increasing diastolic filling time
- Vasopressors
- Peripheral Vasoconstrictors (e.g. Vasopressin, Phenylephrine) are preferred
- Avoid inotropes (increase Heart Rate and contractility) that worsen obstruction
- Intravenous Fluids
- Manage Tachydysrhythmias
- Synchronized Cardioversion for Atrial Fibrillation with Rapid Ventricular Rate
- Consider Esmolol to slow Tachycardias
- Other measures
- Avoid initial diuresis (decreases Preload)
VIII. Resources
- Left Ventricular Outflow Obstruction (Internet Book of Critical Care, Dr. Farkas)
- Left Ventricular Outflow Obstruction (StatPearls)
IX. References
- DeMeester and Swaminathan (2024) EM:Rap, 9/2/2024
- Mallemat and Swaminathan (2024) Crit Bits: Left Ventricular Outflow Obstruction, EM:Rap 11/11/2024
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Related Studies
| Concepts | Disease or Syndrome (T047) |
| MSH | D014694 |
| English | Left Ventricular Outflow Obstruction, Outflow Obstruction, Left Ventricular, Left ventricular outflow obstruction, Ventricular Outflow Obstruction, Left |
| Portuguese | Obstrução do Fluxo Ventricular Esquerdo |
| Spanish | Obstrucción al Flujo de Salida del Ventrículo Izquierdo |
| French | Obstacle à l'éjection ventriculaire gauche, Obstruction ventriculaire gauche |
| German | Ventrikelausflußobstruktion, Links- |
| Italian | Ostruzione del flusso al ventricolo sinistro, Ostruzione del flusso ventricolare sinistro |
| Norwegian | Venstre ventrikkel-utløpsobstruksjon |
| Dutch | Outflow-obstructie van linkerventrikel |
