An abnormal global longitudinal strain (GLS) means your heart muscle is not squeezing as efficiently as it should along its long axis, and it often signals trouble before other tests pick anything up. GLS is a measure of how much the heart muscle deforms during each beat, captured through specialized ultrasound imaging. Where traditional measures like ejection fraction can look reassuringly normal for years while the heart quietly deteriorates, GLS tends to flag problems earlier, making it one of the more valuable tools cardiologists have gained in the past two decades.
What GLS Actually Measures
Your heart muscle shortens and lengthens with every beat. GLS captures that shortening specifically in the lengthwise (longitudinal) direction, from base to apex. The measurement uses a technique called speckle-tracking echocardiography, which follows tiny acoustic markers in the ultrasound image frame by frame, calculating how much the tissue deforms. The result is expressed as a negative percentage: a GLS of −20% means the muscle shortened by 20% during contraction. More negative values mean better function, which trips people up at first. A reading of −22% is healthier than −14%.
This approach measures deformation of the muscle itself, which shows up abnormal earlier than visible wall-motion problems on a standard echocardiogram. In coronary artery disease, for instance, the inner layers of the heart wall (the subendocardium) lose function first. GLS can detect that reduced shortening while the wall still appears to move normally on a conventional echo.1PubMed Central. A Case of Myocardial Ischemia Detected by Global Longitudinal Strain Using Intraoperative Speckle-Tracking Echocardiography in a High-Risk Patient Undergoing Abdominal Aortic Aneurysm Repair That early sensitivity is the core reason GLS has become clinically important: it detects what cardiologists call subclinical dysfunction, meaning the heart is struggling but has not yet produced symptoms or obvious abnormalities on older tests.2International Journal of Cardiology and Cardiovascular Disorder. Global Longitudinal Strain Measured by 2D Speckle Tracking Echocardiography in Stable Angina Patients and Their Angiographic Correlation
What Counts as Normal
The reference range for left ventricular GLS in healthy adults runs roughly from −24% to −16%, though individual values depend on age, sex, and the ultrasound equipment used.3PubMed. Echocardiographic Reference Ranges of Global Longitudinal Strain for All Cardiac Chambers Using Guideline-Directed Dedicated Views As a rough rule of thumb, values less negative than about −16% are generally considered reduced, and most clinical studies use a cutoff somewhere between −16% and −20% depending on the condition being studied.
Age makes a difference. GLS values tend to drift toward less negative numbers as people get older, so a reading of −17% in an 80-year-old carries a different significance than the same number in a 30-year-old. Sex matters too: women typically have slightly more negative (better) GLS than men. In healthy children, the average left ventricular GLS is around −20%, with a fairly tight confidence interval.4PubMed Central. Reference Ranges of Left Ventricular Strain Measures by Two-Dimensional Speckle Tracking Echocardiography in Children: A Systematic Review and Meta-Analysis
One practical complication: different ultrasound vendors and software packages produce slightly different numbers for the same heart. While the field has worked hard to standardize, you cannot assume a GLS of −18% from one machine means exactly the same thing on another. This is why cardiologists prefer to track changes in GLS over time using the same equipment and software, rather than comparing single readings across different labs.
Why GLS Often Matters More Than Ejection Fraction
Ejection fraction (EF) has been the go-to measure of heart function for decades. It estimates what fraction of blood the heart pumps out with each beat. The problem is that EF can stay normal even when the heart muscle is already damaged, because the heart compensates in other ways. A person can have an EF of 55% and still have meaningful dysfunction that GLS would reveal.
In one study of diabetic patients with no cardiovascular complaints and perfectly normal ejection fractions, over 60% already had early systolic dysfunction detectable by GLS. Their average GLS was about −17.4%, compared with −20.6% in healthy controls.5Wiadomości Lekarskie. The Preference of Using Global Longitudinal Strain Speckle Tracking Echo Study Over Measurement of Left Ventricle Ejection Fraction (LVEF) in the Early Detection of Subclinical Systolic Dysfunction in Diabetic Patients Those patients felt fine. Their EF looked fine. But their heart muscle was already underperforming.
In heart failure, the gap between the two measures becomes even more striking. A study of patients hospitalized with acute heart failure found that GLS was a significantly better predictor of who would die within five years than ejection fraction was. Each 1% worsening (less negative) in GLS was associated with a 5% increase in mortality risk, and the sickest group by GLS had a five-year death rate of 49% compared with 34% in the mildest group. After adjusting for other factors, GLS remained an independent predictor of death, while ejection fraction did not.6PubMed. Global Longitudinal Strain to Predict Mortality in Patients With Acute Heart Failure Similar findings have been confirmed in heart failure with reduced ejection fraction specifically, where GLS was the only echocardiographic measure that independently predicted mortality after accounting for clinical variables.7PubMed. Global Longitudinal Strain Is a Superior Predictor of All-Cause Mortality in Heart Failure With Reduced Ejection Fraction
In stable heart failure patients who had not yet developed symptoms, GLS outperformed ejection fraction at predicting who would progress clinically. The accuracy of GLS in identifying these patients was substantially higher than that of EF alone.8PubMed Central. Global Longitudinal Strain versus Left Ventricular Ejection Fraction for the Prediction of Short-term Clinical Progression in Asymptomatic Stable Heart Failure Patients An earlier landmark study put it bluntly: GLS is a superior predictor of outcome compared with either ejection fraction or wall-motion scoring, and a GLS worse than about −12% carried a prognosis roughly equivalent to an EF below 35%.9PubMed. Prediction of all-cause mortality from global longitudinal speckle strain: comparison with ejection fraction and wall motion scoring
Common Conditions That Cause Abnormal GLS
An abnormal GLS reading does not point to a single diagnosis. Many different cardiac and systemic conditions can impair longitudinal shortening. What makes GLS useful is that it picks up damage or dysfunction from a wide variety of causes, often before those causes produce symptoms.
Coronary Artery Disease
Blocked or narrowed coronary arteries reduce blood flow to the heart muscle, and the resulting ischemia hits the subendocardial fibers first. Because those fibers run longitudinally, GLS drops before other measures of function change. In patients with normal resting wall motion, resting GLS performed comparably to stress echocardiography for predicting significant coronary artery disease, and it added meaningful predictive value on top of clinical information alone.10PubMed Central. Rest global longitudinal 2D strain to detect coronary artery disease in patients undergoing stress echocardiography: a comparison with wall-motion and coronary flow reserve responses When individual segments show reduced strain, cardiologists can sometimes infer which coronary artery territory is affected.
Hypertension
High blood pressure forces the heart to work harder over time, and GLS often deteriorates long before the heart visibly thickens or the ejection fraction drops. In patients with essential hypertension and preserved EF, poorly controlled blood pressure was associated with substantially lower GLS and roughly nine-fold higher odds of having a GLS worse than −19%, compared with patients whose blood pressure was well-managed.11The Open Cardiovascular Medicine Journal. Predictors of Impaired Left Ventricular Global Longitudinal Strain in Patients with Essential Hypertension and Preserved Ejection Fraction The number of blood-pressure medications a patient required also correlated with worsening GLS, suggesting that the severity and duration of hypertension matters, not just whether blood pressure is elevated at a single visit. Diabetes and high cholesterol, which commonly coexist with hypertension, further worsen GLS independently.
Cancer Therapy
One of the most established clinical uses for GLS monitoring is in patients undergoing cancer treatment, particularly with drugs like anthracyclines (commonly used for breast cancer and lymphoma). These medications can damage the heart, and European Society of Cardiology guidelines now specifically identify GLS as a key tool for detecting this damage early. A relative decrease in GLS of more than 15% during cancer treatment is the recommended threshold for suspecting subclinical cardiac injury.12PubMed Central. Global Longitudinal Strain in Cardio-Oncology: A Review Multiple studies have consistently found that GLS detects this myocardial dysfunction before ejection fraction declines, giving oncologists and cardiologists a window to start protective medications or adjust cancer treatment before irreversible damage occurs.13PubMed Central. Strain Imaging in Cardio-Oncology
Valve Disease
In aortic stenosis, where the aortic valve narrows and forces the heart to pump harder, GLS can help determine when a patient who still feels fine should consider valve replacement. Patients with severe aortic stenosis and a baseline GLS worse than about −18% were more likely to develop symptoms and need valve intervention during follow-up compared with those whose GLS was more preserved.14PubMed Central. Association of Left Ventricular Global Longitudinal Strain With Asymptomatic Severe Aortic Stenosis: Natural Course and Prognostic Value A meta-analysis confirmed that patients with abnormal stress responses had worse resting GLS, and the difference in GLS between groups more than doubled during exercise.15Cardiovascular Biomedicine Journal. Global longitudinal strain in stress test of asymptomatic severe aortic stenosis: a focused meta-analysis
Heart Failure with Preserved Ejection Fraction
This condition, where the heart fails despite a normal-looking EF, has long been difficult to assess with traditional imaging. GLS has proved particularly valuable here. In a study of over 300 patients with this type of heart failure, about 59% had abnormal GLS. Over a median follow-up of nearly five years, those with abnormal GLS experienced significantly more adverse outcomes, were more likely to see their ejection fraction deteriorate over time, and faced roughly 74% higher risk for a composite of death and hospitalization compared with those whose GLS was normal.16PubMed. Global longitudinal strain predicts clinical outcomes in patients with heart failure with preserved ejection fraction
The Pattern Matters, Not Just the Number
Cardiologists do not just look at the single GLS number. The pattern of which segments are affected and how the strain is distributed across the heart can point toward a specific diagnosis. One classic example is cardiac amyloidosis, a condition where abnormal proteins build up in the heart muscle. In amyloidosis, the base and middle segments of the heart show markedly reduced strain while the apex is relatively spared, creating a distinctive “apical sparing” pattern on the strain map. This pattern is both sensitive and specific for amyloidosis and helps differentiate it from other causes of thickened heart walls.17PubMed. Relative apical sparing of longitudinal strain using two-dimensional speckle-tracking echocardiography is both sensitive and specific for the diagnosis of cardiac amyloidosis
Regional strain patterns also help distinguish an athlete’s heart from a diseased one. Competitive athletes often develop thickened heart walls as a healthy adaptation to training, which can look worryingly similar on a standard echo to a condition called hypertrophic cardiomyopathy. GLS helps sort this out. In people with wall thickness above 11 mm, a GLS reading of −18% or better distinguished healthy adaptation from pathological thickening with about 79% specificity.18PubMed Central. Global longitudinal strain differentiates physiological hypertrophy from maladaptive remodeling In some cases, resting GLS looks similar in athletes with and without underlying disease, but exercise GLS can unmask the difference.19Journal of the American Society of Echocardiography. Abnormal Global Longitudinal Strain: What Does It Mean?
Blood Pressure at the Time of the Test
One underappreciated wrinkle: your blood pressure at the exact moment of the echocardiogram can affect the GLS reading. GLS is sensitive to afterload, which is essentially the resistance the heart pumps against. When blood pressure is elevated, the heart works harder to push blood out, and GLS may appear worse than it would at a lower blood pressure, even though the heart muscle itself has not changed. Longitudinal strain is particularly sensitive to this effect because of the orientation and mechanical properties of the longitudinal muscle fibers.20PubMed Central. Impact of blood pressure changes on myocardial work indices in hypertensive patients in a day
This has prompted some researchers to propose adjusting GLS values for the patient’s blood pressure at the time of the test. Blood-pressure-adjusted strain showed improved ability to predict cardiac events and death compared with unadjusted values.21PubMed Central. Prognostic utility of blood pressure-adjusted global and basal systolic longitudinal strain This adjustment is not yet routine in clinical practice, but it is worth knowing about. If your blood pressure was unusually high during the echo, a mildly abnormal GLS may partially reflect that transient spike rather than permanent heart-muscle damage.
How GLS Guides Treatment Decisions
An abnormal GLS is not just a number that predicts bad outcomes; it increasingly drives what doctors actually do. In cancer patients receiving cardiotoxic chemotherapy, detecting a significant GLS drop triggers a conversation about starting heart-protective medications such as beta-blockers, ACE inhibitors, or statins. Evidence supports the protective value of these drugs in at-risk patients, and using GLS to identify who needs them allows clinicians to target treatment rather than giving cardioprotective drugs to everyone.22PubMed Central. Global Longitudinal Strain Monitoring to Guide Cardioprotective Medications During Anthracycline Treatment
In valve disease, GLS can influence the timing of surgery. If a patient with severe aortic stenosis has no symptoms but GLS is declining, that may tip the scales toward earlier valve replacement rather than watchful waiting.14PubMed Central. Association of Left Ventricular Global Longitudinal Strain With Asymptomatic Severe Aortic Stenosis: Natural Course and Prognostic Value For patients already in heart failure, GLS helps assess whether treatments are working. In a study of cardiac contractility modulation therapy (a device-based treatment for heart failure), GLS improved alongside ejection fraction and measures of the heart’s energy efficiency at six-month follow-up.23PubMed Central. The Effects of Device-Based Cardiac Contractility Modulation Therapy on Left Ventricle Global Longitudinal Strain and Myocardial Mechano-Energetic Efficiency in Patients with Heart Failure with Reduced Ejection Fraction
Strain Beyond the Left Ventricle
While left ventricular GLS gets most of the attention, strain measurements are now applied to other heart chambers as well. Right ventricular strain assesses the right side of the heart, which pumps blood to the lungs and can fail independently of the left side. Normal right ventricular free-wall strain ranges from about −35% to −17%.3PubMed. Echocardiographic Reference Ranges of Global Longitudinal Strain for All Cardiac Chambers Using Guideline-Directed Dedicated Views Left atrial strain has become particularly relevant for detecting early dysfunction that precedes atrial fibrillation and for estimating how stiff the left ventricle is during filling, a measurement traditionally requiring invasive catheterization.24Current Cardiovascular Imaging Reports. New Insights in Strain Mechanics (LA, RA, and RV) Chamber-specific software has improved the reliability of these measurements, and vendor-independent tools now show strong agreement with established vendor-specific platforms for left ventricular, right ventricular, and left atrial strain.25European Heart Journal – Cardiovascular Imaging. A new vendor-independent software tool allows for reliable measurement of left ventricular, right ventricular and left atrial global longitudinal strain
Technical Factors That Can Throw Off the Reading
GLS is more reproducible than ejection fraction, but it is not immune to technical pitfalls. Several factors can produce misleading values even when the heart itself is fine, or mask real problems when it is not.
Frame rate is one of the biggest technical influences. If the ultrasound acquires too few frames per second, the software cannot track speckle movement accurately, and strain values are systematically underestimated. Studies on both simulated models and real patient data have confirmed that lower frame rates lead to lower (worse-appearing) strain numbers and higher measurement variability.26European Heart Journal – Cardiovascular Imaging. The influence of frame rate on two-dimensional speckle-tracking strain measurements: a study on silico-simulated models and images recorded in patients For three-dimensional speckle tracking, frame rates below about 18 per second produced significantly lower strain values than higher frame-rate acquisitions.27PubMed. Effects of frame rate on three-dimensional speckle-tracking-based measurements of myocardial deformation
Image quality also matters. Poor acoustic windows, which are common in patients who are obese, have lung disease, or are on mechanical ventilation, degrade tracking accuracy. The reproducibility of GLS before cardiac surgery, for example, showed moderate observer variability with a coefficient of variation around 8% to 10% between different readers.28PubMed. Global longitudinal strain before cardiac surgery: Improving feasibility, reproducibility, and variability That means two sonographers analyzing the same images might come up with readings that differ by about one to two percentage points, which is enough to cross a clinical threshold in borderline cases.
Cardiac MRI offers an alternative way to measure GLS through a technique called feature tracking, and its values correlate well with speckle-tracking echocardiography, with correlation coefficients in the range of 0.71 to 0.87 depending on the specific strain parameter.29PubMed. Quantification of left ventricular myocardial strain: Comparison between MRI tagging, MRI feature tracking, and ultrasound speckle tracking However, the two methods are not perfectly interchangeable. A study in breast cancer patients undergoing chemotherapy found statistically significant differences between MRI-derived and echo-derived GLS values, concluding that switching between the two techniques during longitudinal monitoring is not reliable.30Circulation. Abstract 4145207: A Comparison Between Global Longitudinal Strain (GLS) Derived with CMR Feature-Tracking (CMR-FT) and 2D Speckle-Tracking Echocardiography (2D-STE) to Monitor Cancer Therapy-Related Cardiac Dysfunction (CTRCD) The practical takeaway: if your GLS is being tracked over time for any reason, try to get it done the same way each time.
When an Abnormal GLS Might Not Mean What You Think
Context shapes interpretation. A few situations commonly produce GLS readings that look alarming but are not necessarily cause for immediate worry. High blood pressure at the time of the test, as discussed above, is one. Another is pregnancy, during which normal cardiovascular changes can shift GLS. Acute illness, dehydration, and tachycardia (a fast heart rate) can all transiently affect strain values without reflecting permanent damage to the heart muscle.
On the flip side, a normal GLS does not guarantee a healthy heart. In certain conditions like constrictive pericarditis, the problem lies in the sac around the heart rather than the muscle itself, and GLS may appear normal despite significant hemodynamic compromise. Some infiltrative diseases in their earliest stages may show regional abnormalities while the global number is still within range. This is why cardiologists look at the regional strain map, not just the single global figure, and why GLS is interpreted alongside the full clinical picture rather than in isolation.