What is left ventricular outflow obstruction (LVOT obstruction)?

From the Guidelines

Left ventricular outflow obstruction (LVOT obstruction) is a dynamic condition where blood flow from the left ventricle to the aorta is impeded, often caused by hypertrophic cardiomyopathy, and is defined by a peak instantaneous continuous wave Doppler gradient or peak-to-peak cardiac catheterization gradient of 30 mm Hg or more at rest or with physiologic provocation. This condition can lead to an increase in LV systolic pressure, resulting in a complex interplay of abnormalities including prolongation of ventricular relaxation, elevation of LV diastolic pressure, mitral regurgitation, myocardial ischemia, and a decrease in forward cardiac output 1. The mechanism of LVOT obstruction in hypertrophic cardiomyopathy is primarily due to mitral valve systolic anterior motion (SAM) and mitral-septal contact, rather than systolic contraction of the hypertrophied basal ventricular septum encroaching on the LVOT 1. Some key points to consider about LVOT obstruction include:

• It can occur at various levels, including the subvalvular area, the aortic valve itself, or the supravalvular region
• The condition is dynamic, varying with loading conditions and contractility of the ventricle, and can be exacerbated by increased myocardial contractility, decreased ventricular volume, or decreased afterload 1
• Patients may experience symptoms such as chest pain, shortness of breath, dizziness, fainting, and in severe cases, heart failure or sudden cardiac death
• Diagnosis typically involves echocardiography, cardiac MRI, or cardiac catheterization to assess the degree and location of obstruction
• Treatment depends on the cause and severity, ranging from medication management with beta-blockers or calcium channel blockers to reduce heart contractility, to surgical interventions such as septal myectomy, alcohol septal ablation, or valve replacement, with marked gradients of 50 mm Hg or more representing the conventional threshold for surgical or percutaneous intervention if symptoms cannot be controlled with medications 1.

From the Research

Definition of Left Ventricular Outflow Obstruction (LVOT Obstruction)

• Left ventricular outflow tract obstruction (LVOTO) is a condition where there is a blockage or narrowing of the left ventricular outflow tract, which is the passage through which blood flows from the left ventricle to the aorta 2, 3.
• This obstruction can be caused by various factors, including hypertrophic cardiomyopathy (HCM), which is a condition where the heart muscle becomes thickened, leading to a narrowing of the left ventricular outflow tract 2, 3.

Clinical Significance of LVOT Obstruction

• LVOTO is associated with reduced survival in patients with HCM, and the severity of the obstruction is related to the risk of sudden death and heart failure 4.
• The presence of LVOTO can also lead to hemodynamic instability, which can be unresponsive to conventional supportive measures, and can precipitate hemodynamic shock in critically ill patients 5, 6.
• The clinical significance of LVOTO is not limited to HCM, as it can also occur in other conditions, such as after aortic valve replacement, and can be caused by various pathoanatomic mechanisms 6.

Diagnosis and Management of LVOT Obstruction

• Echocardiographic examination is essential in recognizing LVOTO and its underlying conditions, and in identifying the most appropriate therapeutic strategy 5, 6.
• The management of LVOTO depends on the underlying cause and the severity of the obstruction, and can include conservative (medical) and surgical options 6.
• A stepwise approach should be formulated based on the physiological and anatomical substrates predisposing to LVOTO, and a comprehensive echocardiographic examination can aid in risk prediction, diagnosis, severity characterization, and follow-up of management efficacy 6.