What is the significance of peak longitudinal strain in assessing cardiac function?

Significance of Peak Longitudinal Strain in Cardiac Function Assessment

Peak longitudinal strain (GLS) is a superior and more sensitive marker for detecting subclinical myocardial dysfunction than ejection fraction, allowing early identification of cardiac abnormalities before symptoms develop or ejection fraction declines.

Understanding Peak Longitudinal Strain

Peak longitudinal strain measures the percentage of myocardial deformation (shortening) during systole, typically assessed using speckle-tracking echocardiography (STE). Unlike traditional ejection fraction measurements, strain imaging can detect subtle changes in myocardial function that occur before overt systolic dysfunction becomes apparent.

Key characteristics of longitudinal strain:

• Measures deformation of myocardial fibers along their long axis
• Expressed as a negative percentage (more negative values indicate better function)
• Normal GLS values are typically more negative than -18% 1
• More sensitive to early myocardial damage than ejection fraction

Clinical Applications

1. Early Detection of Cardiac Dysfunction

• Identifies subclinical LV dysfunction when ejection fraction remains normal 2
• Particularly valuable in heart failure with preserved ejection fraction (HFpEF) 2
• Detects myocardial changes before symptoms develop 2

2. Prognostic Value

• Reduced GLS predicts adverse outcomes in various cardiovascular conditions:
  • Heart transplant patients with reduced GLS experience higher mortality 2
  • Predicts 30-day readmission in HFpEF patients 2
  • Identifies high-risk patients with cardiomyopathies 2

3. Chemotherapy-Induced Cardiotoxicity

• Early detection of cardiotoxicity before EF decline:
  • A ≥11% relative reduction in GLS predicts subsequent trastuzumab-associated cardiotoxicity 2
  • A 10-15% early reduction in GLS during therapy is the most useful parameter for predicting cardiotoxicity 2
  • Abnormalities can persist years after cardiotoxic exposure 2

4. Coronary Artery Disease Assessment

• GLS cutoff value of -16.5% has been shown to detect significant coronary artery disease with 87.6% sensitivity and 85.7% specificity 3
• Regional layer-specific longitudinal strain can help detect ischemic territories 4
• Segmental LPSS value ≥-12% can detect abnormal segmental motion with sensitivity of 70-82% 5

5. Valvular Heart Disease

• Provides early detection of cardiac dysfunction in patients with valvular heart disease before ejection fraction declines 6
• Helps determine optimal timing for intervention to prevent permanent cardiac dysfunction 6

Interpretation Guidelines

1. Normal vs. Abnormal Values:

   • GLS worse than -18% is considered abnormal 1
   • Values vary by cardiac region: basal (-16.7%), mid (-18.2%), and apical (-21.1%) segments 5

2. Specific Cutoff Values:

   • GLS ≥ -16.5%: Significant coronary artery disease 3
   • GLS ≥ -13.5%: High SYNTAX score (severe coronary disease) 3
   • GLS ≥ -14.5%: Triple vessel disease 3

3. Technical Considerations:

   • Vendor variability exists - use same equipment for serial measurements 1
   • Image quality affects accuracy - ensure adequate visualization 2
   • Consider regional vs. global measurements 1

Limitations and Pitfalls

• Lack of standardization across different ultrasound vendors 2
• Requires good image quality for accurate tracking 2
• May be affected by loading conditions and heart rate 2
• Software designed primarily for LV assessment may be less accurate for RV or complex congenital heart conditions 2
• Not all guidelines have established definitive reference ranges for strain values in all clinical scenarios 2

Conclusion

Peak longitudinal strain provides valuable information about cardiac function beyond traditional ejection fraction measurements. Its ability to detect early myocardial dysfunction makes it particularly useful for monitoring patients with preserved ejection fraction, those receiving cardiotoxic therapies, and those with valvular heart disease. As technology and standardization improve, strain imaging is becoming an increasingly important tool in comprehensive cardiac assessment.