The Sokolow-Lyon criteria help doctors detect left ventricular hypertrophy (LVH) on an electrocardiogram (ECG). To use them, you measure the S wave in lead V1 plus the R wave in lead V5 or V6. If the sum is greater than 35 millimeters, the criteria are considered positive for LVH. You can also check the R wave in lead aVL — if it exceeds 11 millimeters, that also suggests LVH.
What Are the Sokolow-Lyon Criteria?
The Sokolow-Lyon criteria are a set of voltage measurements developed in the 1940s. They were created to identify LVH using a standard 12-lead ECG. The criteria rely on the fact that an enlarged left ventricle generates stronger electrical signals, which appear as taller waves on the tracing.
The main formula is: S wave depth in V1 + R wave height in V5 (or V6) ≥ 35 mm. A secondary criterion is: R wave in aVL ≥ 11 mm. If either threshold is met, the ECG is considered suggestive of LVH.
How to Measure the Sokolow-Lyon Voltage
You need a standard ECG with proper calibration. Each small square on the ECG grid equals 0.1 mV, and each large square equals 0.5 mV. The standard calibration is 10 mm/mV, meaning 1 mV equals 10 mm in height.
To measure:
- Find lead V1. Measure the depth of the S wave (the first downward deflection after the R wave) in millimeters.
- Find lead V5 (or V6). Measure the height of the R wave (the first upward deflection) in millimeters.
- Add the two numbers together.
- Then check lead aVL and measure the height of the R wave alone.
If the sum exceeds 35 mm, or if the R wave in aVL exceeds 11 mm, the criteria are positive. Some clinicians also use V6 instead of V5, but the principle is the same.
What Does a Positive Result Mean?
A positive Sokolow-Lyon criterion does not automatically mean a person has LVH. It is a screening tool, not a diagnosis. Many factors can raise voltage on an ECG, including a thin chest wall, young age, or athletic conditioning. Conversely, obesity, lung disease, or pericardial effusion can lower voltage and mask LVH.
Research consistently shows that the Sokolow-Lyon criteria have high specificity (few false positives) but low sensitivity (they miss many true cases of LVH). For example, when compared to echocardiography — a much more accurate test — the Sokolow-Lyon criteria may only detect about 20–40% of confirmed LVH cases. This means a negative result does not rule out LVH.
What Are the Limitations of the Sokolow-Lyon Criteria?
The main limitation is poor sensitivity. Many people with LVH confirmed by imaging will have a normal Sokolow-Lyon measurement. The criteria also assume normal body habitus and electrode placement — any variation can change the voltages.
Another limitation is age. Younger people naturally have larger QRS voltages, so the criteria may overdiagnose LVH in healthy younger adults. Older adults often have lower voltages due to lung changes or chest shape, so the criteria may underdiagnose LVH in them.
Additionally, the criteria were developed before modern imaging. They are best used as a rapid bedside screening tool, not as a definitive test. Most current guidelines recommend using echocardiography or cardiac MRI to confirm LVH when the ECG is suspicious or risk factors are present.
How Does This Compare to Other ECG Criteria for LVH?
Several other voltage-based criteria exist, and they all have similar strengths and weaknesses. The Cornell criteria use the R wave in aVL plus the S wave in V3, with different thresholds for men and women. The Romhilt-Estes scoring system adds points for voltage, ST-T changes, and left atrial enlargement.
A comparison table shows key differences:
| Criteria | Formula | Threshold | Notes |
|---|---|---|---|
| Sokolow-Lyon | SV1 + RV5/V6 | ≥ 35 mm | Older, low sensitivity |
| Cornell | RaVL + SV3 | ≥ 28 mm (men), ≥ 20 mm (women) | Sex-specific |
| Romhilt-Estes | Point system | ≥ 5 points | Includes non-voltage criteria |
No single ECG criterion is perfect. Many clinicians combine multiple criteria to improve detection. Some studies suggest the Cornell criteria have slightly better sensitivity than Sokolow-Lyon, but no voltage-only approach matches imaging accuracy.
When Should the Sokolow-Lyon Criteria Be Used?
The Sokolow-Lyon criteria are most useful as a quick, inexpensive screening tool in settings where ECG is already being performed. For example, during a routine physical, if a patient has high blood pressure or a family history of heart disease, the ECG can raise suspicion of LVH.
However, if LVH is suspected based on symptoms (shortness of breath, chest pain, palpitations) or risk factors (long-standing hypertension, aortic stenosis), an echocardiogram is the appropriate next step. The Sokolow-Lyon criteria should not be relied upon to exclude LVH in a symptomatic patient.
Recent guidelines from cardiology societies emphasize that ECG criteria for LVH are useful for risk stratification but not for diagnosis. A positive result warrants further evaluation. A negative result in a high-risk person still requires imaging.
Can You Use the Sokolow-Lyon Criteria on a Computer-Interpreted ECG?
Many modern ECG machines automatically report Sokolow-Lyon indices. The computer measures the voltages and prints the sum. This can save time and reduce measurement error. However, the same limitations apply — the computer uses the same thresholds and may still miss or overcall LVH.
It is important to review the raw tracing. Electrode misplacement, artifact, or poor tracing quality can cause inaccurate automated measurements. A clinician should always confirm the computer’s interpretation by manually measuring the waves on a clear strip.
Frequently Asked Questions
How do I calculate the Sokolow-Lyon criteria?
Measure the S wave in V1 and the R wave in V5 (or V6) in millimeters, then add them. A sum greater than 35 mm is positive. Also check the R wave in aVL — above 11 mm is another positive sign.
What is a normal Sokolow-Lyon voltage?
There is no single “normal” number because voltage varies by age, body habitus, and sex. In general, a sum below 35 mm and an R wave in aVL below 11 mm are considered normal by these criteria.
Why is the Sokolow-Lyon criteria not always accurate?
These criteria miss many true cases of LVH (low sensitivity) because factors like obesity, lung disease, or electrode placement can reduce voltage. Also, young or thin people may have high voltage without LVH, causing false positives.
Which is better: Sokolow-Lyon or Cornell criteria?
Neither is clearly superior. Some research suggests Cornell criteria have slightly better sensitivity, especially in women. However, both are imperfect screening tools, and echocardiography remains the gold standard for diagnosing LVH.
