Example case of hypertropic cardiomyopathy (HOCM)

Example of biventricular hypertrophy - Uploaded September 2025 by G. Altit

Echocardiographic evaluation of HCM must systematically answer ten essential questions:

1. Presence and distribution of hypertrophy (septal, concentric, apical, mid-ventricular).

   1. Care must be taken not to overestimate septal thickness by including the septal band, which often appears hyperechoic and hypertrophied. In diastole, this band separates clearly from the interventricular septum and should be excluded from measurements.

2. Left ventricular systolic function, including ejection fraction and strain analysis.

3. Left ventricular diastolic function, using transmitral Doppler, tissue Doppler, and left atrial size.

   1. Diastolic Function Assessment includes: Mitral inflow Doppler (E/A ratio, deceleration time). Tissue Doppler imaging (E/e′ ratio >12–15 suggests elevated filling pressures). Pulmonary vein Doppler, where large retrograde A waves indicate advanced diastolic dysfunction. Correlation with invasive LVEDP is imperfect, but a systematic approach combining multiple parameters improves accuracy.

4. Right ventricular size and function.

5. Presence of left ventricular outflow tract (LVOT) obstruction at rest.

6. Beyond the neonatal period - provocable obstruction (Valsalva, exercise, or dobutamine stress echo if resting gradient <30 mmHg).

7. Mitral valve anatomy (leaflet length, papillary muscle position, subvalvular apparatus).

8. Mitral regurgitation severity and jet direction.

9. Guidance for surgical myectomy or alcohol septal ablation when indicated.

10. Family screening, including echocardiography for first-degree relatives.

Fixed vs. Dynamic Obstruction 

Left-sided obstruction in HCM may coexist with fixed lesions such as coarctation of the aorta, valvular aortic stenosis, or subaortic membrane. When both are present, Doppler gradients are no longer reliable, and severity must be assessed using: 

• Qualitative parameters (LVOT flow profile, color Doppler aliasing). 

• Planimetry for aortic valve area. 

• Invasive hemodynamics when necessary.

• Cardiac MRI may be of value to better characterize cardiac structures.

Mitral Valve and Subvalvular Anomalies 

Several anatomic variants contribute to persistent obstruction, including: 

• Bifid or hypertrophied papillary muscles. 

• Muscular bridges connecting papillary muscles. 

• Shortened or thickened chordae tendineae. 

• Anomalous direct insertion of the leaflet onto the papillary muscle. 

These anomalies may necessitate concomitant mitral valve repair or papillary muscle realignment at the time of septal myectomy.

Coronary abnormalities

Angina is a frequent symptom in pediatric HCM despite the absence of atherosclerotic disease. Mechanisms include: 

• Coronary microvascular dysfunction (impaired flow reserve). 

• Coronary fistulae or abnormal arborization. 

• Epicardial coronary anomalies (hypoplasia, absence). 

• Myocardial bridging (systolic compression of a coronary segment). Myocardial bridges are seen in up to 50% of patients with HCM. They are not associated with sudden cardiac death but can contribute to exertional angina. Surgical unroofing or myectomy may be considered in selected symptomatic cases.

• In some cases, a markedly dilated coronary sinus may mimic a low atrial septal defect or persistent left SVC on echocardiography, leading to diagnostic confusion. Careful review of venous anatomy and use of contrast or cross-sectional imaging may clarify the finding.

Key points

• When resting gradients are absent, provoke obstruction with physiologic maneuvers. 

• Carefully assess mitral valve anatomy — elongated leaflets, displaced papillary muscles, and chordal abnormalities are frequent and clinically significant. 

• Consider MRI for poor echo windows, for detecting fibrosis, or when apical aneurysm is suspected. 

• Midventricular obstruction and apical aneurysm are high-risk phenotypes requiring close follow-up and anticoagulation when thrombus is present.

• Studies have shown that up to 40% of patients with hypertrophic cardiomyopathy have ≥3 prominent trabeculations, most often localized to the apex and lateral wall. Segmental strain analysis reveals: A preserved base-to-apex gradient in classic HCM. A markedly abnormal or reversed gradient in LV Non-Compaction, reflecting the embryologic arrest of compaction and impaired apex-to-base myocardial mechanics.

• Patients with HCM require a comprehensive and repeated evaluation, using complementary imaging modalities (TEE, cardiac MRI, coronary angiography) when indicated by symptoms or when transthoracic echo is limited. Early recognition of overlapping phenotypes and high-risk features (e.g., midventricular obstruction, apical aneurysm, severe diastolic dysfunction) is crucial for timely intervention and prevention of complications.

Systolic Anterior Motion of Mitral Valve

In a structurally normal heart, the normal mechanics dictate that the posterior mitral valve leaflet is typically shorter in length compared to the anterior leaflet. Consequently, the coaptation of the mitral valve occurs closer to the lateral wall of the left ventricle. This positioning ensures that the coaptive mitral valve offers the least resistance to the path of blood flow leaving the left ventricular outflow tract (LVOT) during the process of systole. Systolic Anterior Motion of the Mitral Valve, or SAM, is characterized by an abnormal movement where the mitral valve leaflets move into the left ventricular outflow tract during systole. When SAM is present, the observation will be the anterior displacement of either one or both of the mitral valve leaflets. This condition is identified as a manifestation of mitral valve dysfunction. The clinical importance of SAM rests on its ability to result in the obstruction of blood flow that is moving from the left ventricle into the aorta. When this dynamic obstruction occurs, it results in dynamic left ventricular outflow tract obstruction. SAM is commonly associated with hypertrophic cardiomyopathy (HCM). In patients diagnosed with hypertrophic cardiomyopathy, factors contributing to the development of SAM often include abnormalities present in the mitral valve leaflets and in the subvalvular apparatus, which encompasses both the papillary muscles and the chordal apparatus. 

Echocardiography is ideally suited as a diagnostic tool for identifying both the presence of SAM and the severity of the outflow tract obstruction. SAM is characterized by the mitral valve touching the septum during systole. Normally, at the end of diastole, the mitral valve is co-opted with the other leaflet toward the lateral wall. SAM contributes to the pathophysiology of HCM, where it further exacerbates the hypoperfusion state due to low cardiac output. When SAM occurs, the movement of the mitral valve into the LVOT leads to two primary consequences:

1. Outflow Obstruction: The contact between the mitral valve and the septum obstructs the flow of blood leaving the left ventricle. This obstruction creates turbulence and flow acceleration in the LVOT. When assessed by continuous wave (CW) Doppler across the LVOT, this obstruction presents as a dagger-shaped or shark tooth appearance in the wave, instead of the normal parabolic shape. The dagger shape indicates that the blood is initially moving at or slightly above normal velocity, but then there is a strong push from the left ventricle at the end of the ejection phase.

2. Mitral Regurgitation (MR): The abnormal movement can also result in mitral regurgitation, although the sources note that MR is often not seen in neonates with SAM.

Mechanistic Causes of SAM

Three main theories behind the causation of SAM, particularly in the presence of hypertrophic muscles and a bulging septum:

1. The Venturi Effect Theory:

   • In a heart with a bulging septum due to hypertrophy, the forceful ejection of blood creates a very high pressure proximal to the obstruction.

   • The high velocity of blood flow through the narrowed LVOT space leads to the creation of a negative pressure zone, which "sucks" the mitral valve leaflet into the LVOT.

   • This effect is accentuated in cases where afterload is reduced, as this allows for very strong contraction and potentially a lower aortic root pressure. Reducing the afterload further (e.g., potentially through the use of milrinone) could exaggerate the obstruction and worsen cardiac output by accentuating the Venturi effect.

2. Papillary Muscle Displacement Theory:

   • Normally, blood flow entering the heart from the mitral valve moves in a clockwise direction before exiting.

   • In the presence of projecting, bigger papillary muscles, the blood flow is diverted.

   • Instead of moving in a straight path, the flow moves in an anticlockwise direction, going behind the lateral leaflet of the mitral valve. This action pushes the mitral valve leaflet toward the septum, thereby creating the obstruction.

3. Vector Flow Mapping Analysis (Bulging Septum):

   • This theory relates to the bulging of the interventricular septum.

   • When blood exits the ventricle, the bulging septum causes turbulence.

   • Some of the turbulent blood flow goes behind the mitral valve, pushing the leaflet towards the septum and causing the obstruction.

That being said, many believe SAM is caused simply by flow drag parallel to the septum, but this is an oversimplification. In HCM, the subvalvular apparatus — especially the posterior papillary muscle — is displaced anteriorly, which alters inflow direction. Blood enters the LV toward the septum, creating a vortex that pulls the mitral valve toward the septum. This vortex, rather than simple Venturi effect, produces SAM.

Echocardiographic Clues 

• Posteriorly directed MR jet in mild cases. 

• Central or anteriorly directed jet suggests intrinsic mitral disease. 

• Elongated anterior leaflet (>30 mm in adults) may require surgical shortening during myectomy.

References:

• Manabe S, Kasegawa H, Arai H, Takanashi S. Management of systolic anterior motion of the mitral valve: a mechanism-based approach. Gen Thorac Cardiovasc Surg. 2018 Jul;66(7):379-389. doi: 10.1007/s11748-018-0915-0. Epub 2018 Apr 3. PMID: 29616461.

• American Society of Echocardiography - What Causes Systolic Anterior Motion

• Session «Imagerie et Echographie» - RFMCC pratique 2020 - Dr Marie-Josée Raboisson  - YouTube

• Geske, Jeffrey B., et al. "Septal reduction therapies in hypertrophic cardiomyopathy: comparison of surgical septal myectomy and alcohol septal ablation." Interventional cardiology 6.2 (2014): 199.