Global Longitudinal Strain: Key Insights and Clinical Relevance

Global longitudinal strain (GLS) has become a valuable tool for assessing heart function, offering greater sensitivity than traditional measures like ejection fraction. By evaluating myocardial deformation, GLS detects subtle changes in cardiac performance that might otherwise go unnoticed.

Its clinical use continues to expand, from early disease detection to treatment monitoring. Understanding the factors influencing GLS and its role in various cardiovascular conditions is essential as research advances.

Basic Concepts Of Myocardial Strain

Myocardial strain quantifies heart muscle fiber deformation during contraction and relaxation, providing a more refined assessment of cardiac mechanics than traditional volumetric measures. Expressed as a percentage, strain represents the relative change in myocardial length. Global longitudinal strain (GLS) specifically evaluates the shortening of myocardial fibers along the left ventricle’s long axis, serving as a sensitive marker of systolic function. Unlike ejection fraction, which reflects volumetric changes, GLS captures intrinsic myocardial contractility, making it particularly useful for detecting subclinical dysfunction.

The myocardium consists of three fiber layers—subendocardial, midmyocardial, and subepicardial—each contributing differently to cardiac function. Longitudinal fibers, primarily in the subendocardial layer, are highly susceptible to ischemia and other pathological insults. This vulnerability explains why GLS often declines before ejection fraction in conditions such as hypertensive heart disease and chemotherapy-induced cardiotoxicity. A normal GLS value typically ranges from -18% to -22%, with more negative values indicating better myocardial deformation. A reduction in GLS, even with normal ejection fraction, signals early myocardial impairment and highlights its prognostic value.

Strain analysis relies on speckle-tracking echocardiography, which tracks acoustic markers within the myocardium to quantify deformation. This technique allows for angle-independent assessment, improving accuracy over Doppler-based strain imaging. GLS is measured by averaging strain values from multiple left ventricular segments, ensuring a comprehensive evaluation of myocardial performance. Regional dysfunction can alter strain patterns—myocardial infarction leads to segmental strain reductions, while diffuse diseases like amyloidosis cause a more uniform decline.

Techniques For Determining Global Longitudinal Strain

Accurate GLS measurement depends on advanced imaging techniques that track myocardial deformation throughout the cardiac cycle. Speckle-tracking echocardiography (STE) is the preferred method due to its angle independence and high reproducibility. Unlike Doppler-based strain imaging, which is affected by angle dependency and signal noise, STE provides a more reliable assessment by evaluating strain in multiple planes.

The process begins with acquiring high-quality two-dimensional echocardiographic images, typically from standard apical views. Frame rates between 50 and 90 frames per second balance temporal resolution and image quality. Automated border detection algorithms help delineate myocardial contours, though manual adjustments may be needed for accuracy. The software tracks myocardial speckles frame by frame, calculating strain by measuring the relative change in segmental length over time. The GLS value is then derived by averaging strain measurements from multiple myocardial segments.

Despite its advantages, STE is affected by image quality and vendor-specific software differences. Variability in strain measurements across echocardiographic platforms remains a challenge, prompting efforts to standardize GLS acquisition. The American Society of Echocardiography and the European Association of Cardiovascular Imaging recommend vendor-neutral software and standardized imaging protocols to improve consistency. Studies indicate inter-vendor variability can impact GLS values by 2% to 3%, underscoring the importance of consistent methodology when comparing results.

Cardiac magnetic resonance (CMR) feature-tracking offers an alternative for GLS assessment, particularly when echocardiographic image quality is suboptimal. CMR feature-tracking uses cine sequences to analyze myocardial motion, applying speckle-tracking principles to magnetic resonance images. This method provides superior spatial resolution and tissue characterization, making it useful for detecting diffuse myocardial fibrosis or subtle contractile abnormalities. While CMR-derived GLS correlates well with echocardiographic measurements, differences in quantification techniques require careful interpretation when comparing results.

Variables Influencing Strain Measurements

The accuracy of GLS is affected by multiple factors, making standardization a challenge. One significant contributor to variability is image quality—poor acoustic windows or suboptimal endocardial border delineation can cause tracking errors. STE relies on high-resolution images with well-defined myocardial speckles, and inadequate visualization due to patient body habitus, lung interference, or ultrasound attenuation can compromise accuracy. Frame rate selection is also critical; excessively low frame rates may miss peak strain values, while excessively high frame rates can introduce noise and reduce tracking fidelity.

Physiological factors such as preload and afterload conditions also influence GLS values. While myocardial strain reflects intrinsic contractility, loading conditions alter myocardial deformation independently. Increased preload, as seen in volume overload states like mitral regurgitation, can exaggerate strain values by enhancing myocardial stretch. Conversely, elevated afterload, such as in systemic hypertension, can reduce strain due to increased ventricular wall stress. These fluctuations highlight the need for careful interpretation in dynamic clinical settings.

Inter-vendor variability in strain measurement remains a limitation despite standardization efforts. Different echocardiographic software platforms use proprietary tracking algorithms, leading to subtle discrepancies. Studies comparing GLS across vendors report differences of up to 2-3%, which can be clinically relevant when monitoring disease progression or treatment response. To mitigate this, guidelines recommend using the same imaging system for serial assessments whenever possible. Differences in strain reference ranges between vendors also emphasize the need to establish institution-specific normal values.

Applications In Various Cardiovascular Conditions

GLS is a sensitive marker for detecting early myocardial dysfunction across various cardiovascular conditions. In heart failure with preserved ejection fraction (HFpEF), where ejection fraction often fails to capture subtle impairments, GLS identifies early systolic dysfunction before clinical symptoms appear. Studies show reduced GLS in HFpEF patients correlates with worse exercise capacity and higher hospitalization rates, highlighting its prognostic value. Similarly, in heart failure with reduced ejection fraction (HFrEF), GLS provides additional insight by quantifying myocardial contractility, aiding risk stratification and treatment monitoring.

In ischemic heart disease, GLS reliably detects myocardial injury even when wall motion abnormalities are absent on conventional echocardiography. Patients with acute coronary syndrome often show regional strain reductions before infarction develops, making GLS valuable for early diagnosis. GLS also predicts long-term outcomes after myocardial infarction, with more impaired values linked to higher rates of adverse cardiac events. In patients undergoing coronary revascularization, GLS helps assess myocardial viability and guide clinical decision-making.

Influence Of Age And Sex

Physiological variations in GLS occur across age groups and between sexes, requiring careful interpretation in clinical practice. Myocardial deformation is influenced by structural and functional changes with aging, as well as hormonal and anatomical differences between men and women. Recognizing these variations is essential for establishing appropriate reference ranges.

Aging leads to progressive myocardial changes, including increased fibrosis, reduced compliance, and altered fiber orientation. These factors contribute to a gradual decline in GLS, even in individuals without overt cardiovascular disease. Studies show GLS values become less negative with age, reflecting reduced myocardial contractility. This decline results from both intrinsic myocardial changes and increased arterial stiffness, which raises afterload and affects left ventricular deformation. Despite this trend, GLS remains a more sensitive marker of early dysfunction than ejection fraction, particularly in older adults with preserved systolic function but impaired strain values.

Sex-related differences in GLS stem from variations in myocardial structure, hormonal influences, and baseline cardiac function. Women generally have higher (more negative) GLS values than men, reflecting greater myocardial contractility despite similar ejection fractions. Estrogen’s cardioprotective effects contribute to this difference, as do anatomical variations such as smaller left ventricular cavities and thicker myocardial walls relative to body size. However, these differences diminish after menopause as estrogen levels decline, leading to a convergence in GLS values between sexes in older age groups. Understanding these physiological variations ensures GLS is applied appropriately in both men and women across different life stages.