What is the significance of proximal septal thickening on echocardiogram (echo) with a normal ejection fraction (EF)?

Significance of Proximal Septal Thickening on Echo with Normal EF

Proximal septal thickening on echocardiography with normal ejection fraction is potentially significant and warrants further evaluation to rule out early hypertrophic cardiomyopathy or other cardiac pathologies.

Differential Diagnosis

• Hypertrophic Cardiomyopathy (HCM): Proximal septal thickening is a hallmark finding in HCM, even with preserved ejection fraction. This requires careful evaluation as it may represent early disease 1.

• Hypertensive Heart Disease: Chronic hypertension can cause septal thickening, though typically more concentric rather than isolated to the proximal septum 2.

• Normal Variant: In some individuals, a septal/posterior wall ratio up to 1.3 can be seen in 12% of normal subjects without clinical significance 3.

• Coronary Artery Disease: Approximately 11% of patients with coronary artery disease demonstrate disproportionate septal thickening, which may represent a secondary adaptation rather than primary HCM 4.

• Acute Conditions: Rarely, acute ventricular wall thickening can occur in conditions like sepsis, myocarditis, or thrombotic microangiopathy due to myocardial edema 5.

Clinical Significance and Evaluation

When to Be Concerned

• Septal-to-Posterior Wall Ratio:

  • Ratio ≥1.3: Potentially abnormal, seen in 39% of patients with concentric hypertrophy and 95% with HCM 3.
  • Ratio ≥1.5: More specific for genetically determined asymmetric septal hypertrophy 3.

• Associated Findings that increase concern:

  • Left atrial enlargement 1.
  • Diastolic dysfunction on Doppler assessment 1.
  • Left ventricular outflow tract obstruction 1.
  • Family history of HCM or sudden cardiac death 1.

Recommended Evaluation

1. Comprehensive Echocardiographic Assessment:

   • Measure septal thickness at multiple levels 1.
   • Assess for systolic anterior motion of the mitral valve 1.
   • Evaluate diastolic function with Doppler imaging 1.
   • Measure left atrial size 1.

2. Advanced Imaging:

   • Consider cardiac MRI if there is diagnostic uncertainty, as it provides better tissue characterization and can detect fibrosis 1.

3. Family Screening:

   • If HCM is suspected, first-degree relatives should be screened 1.

4. Genetic Testing:

   • Consider if there are other features suggestive of HCM 1.

Prognostic Implications

• Normal EF with Septal Thickening:

  • May represent early disease with preserved systolic function 1.
  • Longitudinal strain measurements may detect early systolic dysfunction even when EF is normal 1.

• Monitoring:

  • Serial echocardiography is recommended to assess for progression of septal hypertrophy 1.
  • Global longitudinal strain (GLS) may provide prognostic information even when EF is normal 1.

Clinical Pitfalls to Avoid

• Don't dismiss as normal variant without thorough evaluation, especially if septal thickness exceeds 13mm 1.

• Don't rely solely on ejection fraction as it may be normal or even increased in early HCM despite underlying myocardial dysfunction 1.

• Don't overlook diastolic dysfunction, which often precedes systolic dysfunction in HCM and can cause symptoms despite normal EF 1.

• Don't forget to assess for dynamic obstruction during Valsalva maneuver, which may unmask latent obstruction 1.

• Don't ignore family history, as HCM is often inherited in an autosomal dominant pattern 1.

Conclusion

Proximal septal thickening on echocardiography, even with normal EF, should prompt a thorough evaluation for HCM and other cardiac pathologies. The finding is not always pathological but requires careful assessment of additional echocardiographic features, clinical context, and family history to determine its significance and guide management.