What are the typical 2D (two-dimensional) echo findings in patients with Hypertrophic Obstructive Cardiomyopathy (HOCM)?

2D Echocardiographic Findings in Hypertrophic Obstructive Cardiomyopathy (HOCM)

The most important 2D echocardiographic findings in HOCM include asymmetric septal hypertrophy with a septal-to-posterior wall thickness ratio ≥1.4, systolic anterior motion (SAM) of the mitral valve, and dynamic left ventricular outflow tract obstruction (LVOTO) that worsens with provocative maneuvers. 1

Primary Diagnostic Features

Left Ventricular Hypertrophy

• Asymmetric septal hypertrophy (ASH):
  • Septal thickness ≥1.4 cm (typically 1.4-3.7 cm)
  • Septal-to-posterior wall thickness ratio ≥1.4 (range 1.4-3.2) 2
  • Maximal wall thickness should be measured in all LV segments from base to apex 1
• Distribution patterns:
  • Most common: Basal anterior septum
  • Less common: Mid-ventricular, apical, or concentric patterns
  • Atypical patterns may require contrast echocardiography for proper visualization 1

Dynamic Left Ventricular Outflow Tract Obstruction

• LVOT gradient measurement:
  • Resting gradient ≥30 mmHg is diagnostic of obstruction
  • Gradient ≥50 mmHg is considered hemodynamically significant 1
• Provocative testing (essential when resting gradient <50 mmHg):
  • Valsalva maneuver
  • Standing position
  • Exercise echocardiography 1
• Mid-systolic closure of the aortic valve may be observed 3

Mitral Valve Abnormalities

• Systolic anterior motion (SAM) of the mitral valve:
  • Pathognomonic finding in obstructive HCM
  • Characterized by large backward component in late systole
  • Extreme approximation to the interventricular septum at peak 2
• Mitral regurgitation:
  • Secondary to SAM and LVOTO
  • Usually posteriorly directed jet 1

Secondary Features

Left Ventricular Function

• Preserved or hyperdynamic systolic function:
  • Typically elevated ejection fraction (often >65%)
  • Reduced longitudinal strain despite normal EF 1
• Diastolic dysfunction:
  • Abnormal mitral inflow pattern
  • Reduced diastolic descent rate of mitral valve
  • Reduced mean diastolic posterior wall velocity 2
  • Increased E/e' ratio (suggestive of elevated filling pressures) 1

Left Atrial Enlargement

• Increased left atrial volume index (>34 mL/m²)
• Reflects chronic diastolic dysfunction and mitral regurgitation 1

Other Features

• Papillary muscle abnormalities:
  • Hypertrophy
  • Anterior displacement
  • Direct insertion into anterior mitral leaflet 1
• Apical aneurysm (in some variants)
  • May require contrast echocardiography for detection 1
• Right ventricular hypertrophy (less common) 1

Diagnostic Approach

1. Comprehensive 2D and Doppler assessment:

   • Measure wall thickness in all segments
   • Assess LV systolic and diastolic function
   • Evaluate mitral valve function and morphology 1

2. Dynamic assessment:

   • Perform Valsalva maneuver in sitting and semi-supine positions
   • Standing assessment if no gradient is provoked
   • Exercise echocardiography for symptomatic patients with resting gradient <50 mmHg 1

3. Consider advanced techniques when standard imaging is suboptimal:

   • Contrast echocardiography for suspected apical variants or aneurysms
   • Transesophageal echocardiography (TEE) when mechanism of obstruction is unclear
   • 3D echocardiography for accurate assessment of LVOT area and morphology 1

Clinical Pitfalls and Caveats

• Overestimation of wall thickness can occur with:

  • Oblique imaging planes, especially at the apex
  • Inclusion of paraseptal structures (moderator band, false tendons) 1
  • Improper technique with spoiled gradient echo images 1

• Underestimation of LVOTO:

  • Resting echocardiography misses obstruction in up to 50% of cases
  • Always perform provocative maneuvers when suspecting HOCM 1

• Differential diagnosis considerations:

  • Athlete's heart (typically lacks SAM and has symmetric hypertrophy)
  • Hypertensive heart disease (typically concentric pattern)
  • Infiltrative diseases (may have specific echo features like "ground glass" appearance in amyloidosis) 1

Regular follow-up echocardiography (every 1-2 years in stable patients) is essential to monitor disease progression, detect complications, and guide therapeutic decisions 1.