Clinic Procedures

1. Concept and Measurement

• Longitudinal Strain: Refers to the change in length of myocardial fibers from base to apex during the cardiac cycle, particularly during systole.
• Global Strain: Measures the overall deformation across the entire left ventricle, focusing on the longitudinal axis.
• Echocardiographic Technique: LV GLS is typically measured using 2D speckle tracking echocardiography or 3D imaging, which tracks the movement of speckles in myocardial tissue.

2. Components of the LV GLS

• Longitudinal Deformation: The heart muscle shortens during contraction (systole), and this shortening is quantified in terms of strain (percentage change in length).
• Global vs. Regional Strain: While global refers to the overall function of the entire left ventricle, regional strain can be assessed to detect localized dysfunction.
• Positive and Negative Strain Values: A negative GLS value indicates myocardial shortening (normal function). A more negative value (e.g., -20%) indicates better myocardial function, whereas values closer to 0% or positive suggest dysfunction.

3. Clinical Relevance and Functionality

• Detection of Systolic Dysfunction: GLS is a sensitive marker for detecting subtle systolic dysfunction, even before a reduction in ejection fraction (EF) becomes apparent.
• Early Detection of Heart Disease: It is useful for identifying early myocardial impairment in conditions such as heart failure, ischemic heart disease, valvular heart diseases, and chemotherapy-induced cardiotoxicity.
• Quantification of Cardiac Performance: Helps in assessing the effectiveness of cardiac interventions or treatments, providing a precise evaluation of myocardial strain.
• Comparative Advantage: It offers better sensitivity compared to traditional measures like ejection fraction (EF), which might not reflect early dysfunction.

4. Functional Components

• Left Ventricular Walls: GLS specifically tracks the longitudinal strain of the left ventricular myocardium, primarily focusing on the inferior, anterior, lateral, and septal walls.
• Strain Curves: The strain value is derived from the strain curve, which shows the percentage deformation of myocardial fibers during the cardiac cycle, and is analyzed for timing and magnitude.

5. Normal vs. Abnormal GLS

• Normal GLS: Typically between -18% to -22% (more negative values indicate better function).
• Abnormal GLS: Values less than -16% may indicate impaired function, and a reduction in GLS is often seen in heart diseases like diastolic dysfunction, ischemic heart disease, and heart failure.

6. Benefits of Using LV GLS

• Objective and Quantitative: Provides a precise, numerical value that can be tracked over time.
• Early Detection: Helps identify early cardiac dysfunction in conditions where conventional measures like EF may be normal.
• Non-invasive: It’s a non-invasive and safe test that can be easily repeated for ongoing monitoring.
• Predictive Value: Poor GLS is associated with worse clinical outcomes, making it a valuable prognostic marker.

7. Limitations

• Operator-Dependent: Accurate assessment requires skilled echocardiography operators.
• Technical Factors: Image quality, heart rate, and technical settings can influence accuracy.
• Variability: There can be variability in results across different vendors or systems used for strain measurement.