Sokolow-Lyon index on ECG

What is the Sokolow-Lyon index and how to calculate it?

The Sokolow-Lyon index is one of the key parameters used when interpreting a standard 12-lead electrocardiogram. Its main clinical task is to detect left ventricular hypertrophy (LVH) and subsequently assess the patient's overall cardiovascular risk.

According to clinical guidelines (level of recommendation validity B, level of evidence reliability 1), performing a 12-lead ECG is recommended for absolutely all patients suffering from arterial hypertension. This study should be performed at least 1–2 times a year.

The formula for calculating the indicator is extremely simple. The physician needs to evaluate the amplitude of the ventricular complex in the chest leads:

• Measure the depth of the S wave in lead V1 (in millimeters).
• Measure the height of the R wave in lead V5 or V6 (choose the maximum value, also in millimeters).
• Add the obtained values together: SV1 + RV5-6.

If the final sum exceeds 35 mm, this is regarded as a reliable electrocardiographic sign of increased left ventricular myocardial mass.

Additional ECG criteria for hypertrophy

In addition to the Sokolow-Lyon index, additional parameters are mandatory calculated to improve diagnostic accuracy. A comprehensive approach helps reduce the likelihood of diagnostic error when analyzing the ECG. These mandatory criteria include:

1. R-wave amplitude in lead aVL: a value of $\ge 11$ mm is considered an electrocardiographic sign of pathology.
2. Cornell voltage index: calculated as the sum of the amplitudes of the R wave in lead aVL and the S wave in lead V3 (RaVL + SV3). The reference values for this indicator strictly depend on the patient's gender: for women, a result of $> 20$ mm is considered pathological, and for men, $> 28$ mm.
3. Cornell product: this index takes into account not only voltage (amplitude) but also the duration of the ventricular complex. The calculation formula is as follows: (RaVL + SV5 mm $\times$ QRS ms). A result exceeding $2440$ mm $\times$ ms indicates the presence of left ventricular hypertrophy.

The role of ECG and EchoCG in comprehensive diagnostics

Despite its availability and mandatory application, a standard ECG has lower sensitivity in detecting myocardial hypertrophy compared to echocardiography (EchoCG). Nevertheless, electrocardiography remains an indispensable tool for assessing heart rate (HR), analyzing heart rhythm, and timely detecting various arrhythmias.

For a more precise verification of the diagnosis, patients are referred for EchoCG.

• Main goal of the study: precise determination of the left ventricular mass index (LVMI) and assessment of diastolic function.
• Indications for initial examination: the study is mandatory when placing a patient under dispensary monitoring, as well as upon detecting any pathological changes on the ECG.

Subsequently, ultrasound monitoring is performed as indicated. However, it becomes strictly mandatory (at least once a year or once every 2 years, depending on the clinical situation) if the patient fails to achieve target blood pressure levels, AND ECG records the progression of hypertrophy (an increase in the Sokolow-Lyon index or Cornell product is observed).

As an adjunct to instrumental methods, the mandatory diagnostic minimum includes laboratory tests—specifically, a urine test for microalbuminuria (performed upon enrollment in dispensary monitoring and at least once every 2 years thereafter).

Class and exam questions

What else to study on this topic

• Cornell voltage index and Cornell product: calculation rules
• Determining LVMI (left ventricular mass index) via EchoCG
• Assessment of cardiac diastolic function in arterial hypertension
• Urine test for microalbuminuria as part of the mandatory diagnostic minimum
• Indications for dynamic EchoCG monitoring in hypertensive patients

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.