From the Guidelines
For a patient with hypertrophic obstructive cardiomyopathy (HOCM) with left ventricular outflow tract (LVOT) obstruction, transthoracic echocardiography (TTE) is recommended to measure the peak LVOT gradient, both at rest and with provocation, as stated in the 2024 AHA/ACC/AMSSM/HRS/PACES/SCMR guideline for the management of hypertrophic cardiomyopathy 1.
Key Measurements
The following measurements should be obtained using TTE:
- Peak LVOT gradient, both at rest and with provocation, using continuous wave Doppler aligned parallel to the LVOT flow, typically from the apical five-chamber or three-chamber views
- Septal thickness
- Mitral valve morphology and systolic anterior motion (SAM)
- Mitral regurgitation severity
- Left atrial size
Importance of TTE
TTE is essential for diagnosis, risk stratification, treatment decisions, and monitoring disease progression in HOCM patients. The measurement of peak LVOT gradient is crucial for assessing the severity of LVOT obstruction, and provocative maneuvers such as Valsalva, standing, or exercise should be performed to unmask latent obstruction if the resting gradient is <30 mmHg.
Clinical Decision-Making
The information obtained from TTE can inform clinical decision-making, including medication adjustments, septal reduction therapy considerations, and monitoring disease progression. Additionally, TTE can be useful in evaluating the response to treatment and assessing the need for further interventions.
Guideline Recommendations
The 2024 AHA/ACC/AMSSM/HRS/PACES/SCMR guideline recommends TTE as the primary imaging modality for patients with HOCM, with CMR imaging offering complementary information and as an alternative to echocardiography for selected patients in whom the echocardiogram is inconclusive 1. The guideline also recommends repeat TTE every 1 to 2 years to assess the degree of myocardial hypertrophy, dynamic LVOTO, MR, and myocardial function in patients with HOCM who have no change in clinical status or events 1.
From the Research
Measuring LVOT Gradient in HOCM Patients using TTE
- Transthoracic echocardiography (TTE) is a useful tool for measuring left ventricular outflow tract (LVOT) gradient in patients with hypertrophic obstructive cardiomyopathy (HOCM) 2.
- TTE can help identify patients with fixed LVOT obstruction, which is important for choosing therapy 3.
- The LVOT gradient measured by TTE can be variable, and this variability should be considered when determining appropriate therapy in symptomatic patients 2, 4.
- A study found a strong correlation between Doppler measurements and simultaneous measurement of LVOT gradient, confirming the accuracy of TTE measurements 2.
Factors Affecting LVOT Gradient Measurement
- The degree of LVOT obstruction is dynamic and dependent upon ventricular load and contractility 5, 2.
- Spontaneous variability in LVOT gradient can lead to misclassification of obstruction severity in some patients 4.
- Provocative maneuvers or interventions can also affect LVOT gradient measurements 2, 4.
Clinical Implications
- Accurate measurement of LVOT gradient is crucial for managing HOCM patients, as it directs the management algorithm and determines the need for interventions such as septal reduction therapy or alcohol septal ablation 5, 6.
- Consideration of LVOT gradient variability is essential for making informed treatment decisions and avoiding misclassification of obstruction severity 2, 4.