Left ventricular hypertrophy (LVH) is a condition characterized by increased muscle mass in the left ventricle.
Its main causes are high blood pressure, aortic stenosis and, and, less frequently, hypertrophic cardiomyopathy.
The electrocardiogram is a tool that allows early diagnosis, with low sensitivity but high specificity..
The Sokolow-Lyon criteria, described in 1949, is one of the most widely used criteria in clinical practice, because of its simplicity and ease, to determine left ventricular hypertrophy.
To calculate the Sokolow-Lyon criteria, the amplitude of the S wave in lead V1 must be added to the amplitude of the highest R wave in leads V5 or V6.
Sokolow-Lyon Index= SV1 + R (V5 or V6)
If the result is greater than 3.5 mV (35 mm or 7 large squares) it is suggestive of left ventricular hypertrophy.
The increased thickness of the left ventricle in LVH causes an increase in electrical forces during its depolarization.
This increase generates a deepening of the S waves in right precordial leads (V1-V2) and a greater amplitude of the R waves in left precordial leads (V5-V6).
The Sokolow-Lyon index is the sum of both waves, so in case of left ventricular hypertrophy it is usually greater than 35 mm.
The Sokolow-Lyon criteria has a low sensitivity for detecting left ventricular hypertrophy, but a high specificity.
According to studies, the body mass index is the factor that most frequently alters its assessment.
In obese patients, the amplitude of the QRS complex in precordial leads usually decreases due to the interposition of fat between the electrical potentials and the electrodes, leading to an underdiagnosis of the pathology.
On the contrary, it is frequent to find Sokolow-Lyon criteria higher than 35 mm in young and thin patients without associated ventricular hypertrophy, probably in relation to the proximity of the myocardium to the electrodes.
The Sokolow-Lyon criteria is a quick method to make the diagnosis of left ventricular hypertrophy with the electrocardiogram, since it reflects increased electrical forces during depolarization in a ventricle with greater muscle mass.
As it is influenced by the patient's body mass index,, it can cause false positives in young and thin people, and underdiagnosis in obese patients, it is recommended to evaluate other indexes (Romhilt-Estes score, Cornell voltage criteria, or Peguero-Lo Presti criteria) together with the other features of the left ventricular hypertrophy electrocardiogram (left axis deviation, ST-segment depression) to guarantee a certainty diagnosis.
In case of suspicion, an echocardiogram is recommended to confirm the electrocardiographic diagnosis.
