From the Guidelines
Turbulent flow across the Left Ventricular Outflow Tract (LVOT) is a significant finding that requires prompt evaluation and management to prevent adverse outcomes, such as heart failure and sudden cardiac death, as highlighted in the 2020 AHA/ACC guideline for the diagnosis and treatment of patients with hypertrophic cardiomyopathy 1.
Clinical Significance
Turbulent flow across the LVOT indicates abnormal blood flow patterns that may suggest underlying cardiac pathology, including hypertrophic cardiomyopathy, aortic valve stenosis, subaortic membrane, or dynamic LVOT obstruction. The 2020 AHA/ACC guideline emphasizes the importance of evaluating LVOT gradients, which can be dynamic and influenced by various factors, including patient effort and instruction during resting transthoracic echocardiography (TTE) 1.
Diagnostic Approach
A comprehensive echocardiogram, including stress echocardiography, is essential for evaluating the presence and severity of LVOT obstruction, as well as for assessing the patient's functional capacity 1. Cardiopulmonary exercise testing (CPET) with simultaneous measurement of respiratory gases can provide objective data on the severity and mechanism of functional limitation, and is a standard part of the evaluation for patients with severe symptoms, including those being considered for cardiac transplantation 1.
Management
Management of turbulent flow across the LVOT depends on the specific cause and severity, but may include beta-blockers, such as metoprolol 25-100 mg twice daily, for symptomatic patients with dynamic obstruction, as well as avoidance of dehydration and vasodilators 1. For significant aortic stenosis, surgical intervention may be necessary. Patients should be monitored for symptoms like chest pain, syncope, or heart failure, and CPET can be helpful in differentiating hypertrophic cardiomyopathy from other causes of ventricular hypertrophy, such as athletic adaptation 1.
Key Considerations
- Turbulent flow across the LVOT is a significant finding that requires prompt evaluation and management to prevent adverse outcomes.
- A comprehensive echocardiogram, including stress echocardiography, is essential for evaluating the presence and severity of LVOT obstruction.
- CPET with simultaneous measurement of respiratory gases can provide objective data on the severity and mechanism of functional limitation.
- Management depends on the specific cause and severity, but may include beta-blockers, avoidance of dehydration and vasodilators, and surgical intervention for significant aortic stenosis.
From the Research
Turbulent Flow Across LVOT
- Turbulent flow across the left ventricular outflow tract (LVOT) can be caused by various factors, including systolic anterior motion of the mitral valve, septal hypertrophy, and decreased preload or afterload 2.
- LVOT obstruction can lead to hemodynamic compromise and is not uncommon in ICU patients, particularly those with septic shock or severe hypovolemia 2.
- The diagnosis of LVOT obstruction is typically made using Doppler echocardiography, with a peak pressure gradient of at least 30 mmHg at rest or during physiological provocation 2.
Causes and Mechanisms
- Decreased preload due to hypovolemia or decreased afterload due to septic shock can induce a change in LV shape and lead to LVOT obstruction 2.
- Increased heart rate and LV hyperkinesis produced by dobutamine infusion can also contribute to the development of LVOT obstruction 2.
- Septal myectomy can be an effective treatment for LVOT obstruction, particularly in patients with asymmetrical basal septal hypertrophy (ABSH) 3, 4.
Clinical Implications
- LVOT obstruction can be a challenging condition to manage, particularly in patients who have undergone aortic valve replacement 5, 4.
- The ratio of LVOT area to aortic annulus area (L/A ratio) has been identified as a predictor of complete atrioventricular block (CAVB) and permanent pacemaker implantation (PPI) after transcatheter aortic valve replacement (TAVR) 6.
- A low L/A ratio is associated with a higher risk of TAVR-related CAVB and PPI, and may be used to guide treatment decisions 6.