Left ventricular hypertrophy (LVH) is a condition characterized by an increase in the mass of the left ventricle of the heart. This thickening of the heart muscle can be caused by various factors, including high blood pressure, heart valve disease, and genetic conditions. Identifying LVH is crucial because it can lead to serious complications like heart failure, arrhythmias, and sudden cardiac death. The electrocardiogram (ECG) is a valuable tool in detecting LVH, often revealing characteristic changes in voltage and repolarization. One specific ECG finding associated with LVH is the "strain pattern," a manifestation of the heart's attempt to compensate for increased workload. This article will delve into the details of LVH on ECG, focusing specifically on the LV strain pattern, its implications, and how it differs from other ECG abnormalities.
What is LVH on ECG?
The ECG reflects the electrical activity of the heart. In LVH, the increased muscle mass alters the electrical signals, resulting in specific ECG changes. These changes are primarily characterized by increased voltage, reflecting the greater mass of the left ventricle. The most common ECG criteria for LVH include:
* Increased QRS voltage: This is the most prominent feature. The amplitude of the R waves in the precordial leads (V1-V6) and the S waves in the limb leads (I, aVL, V5, V6) are significantly increased. Specific voltage criteria, such as the Sokolow-Lyon voltage criterion (SV1 + RV5 or RV6 ≥ 35 mm) or Cornell voltage criterion (RV5 + SV1 ≥ 28 mm in men, ≥ 20 mm in women), are commonly used to diagnose LVH. These criteria, however, have limitations and should be interpreted cautiously in the context of other ECG findings and clinical information.
* Left axis deviation: The electrical axis of the heart may shift to the left due to the increased mass of the left ventricle. This is reflected in a negative QRS complex in lead aVF and a predominantly negative QRS complex in lead II.
* ST-T wave abnormalities: While not always present, repolarization abnormalities such as ST-segment depression, T-wave inversion, or both, can accompany LVH. These are often seen in the lateral leads (I, aVL, V5, V6) and are associated with the increased myocardial workload and potential strain on the left ventricle.
* QRS duration: Prolonged QRS duration may occur in cases of LVH, particularly when accompanied by conduction abnormalities. A QRS duration exceeding 100 ms suggests the presence of bundle branch blocks or other conduction delays. This is important to note, as these factors can affect the interpretation of the voltage criteria for LVH.
It’s crucial to understand that the presence of these ECG changes alone doesn't definitively diagnose LVH. Other conditions can mimic these findings. Therefore, the ECG should be interpreted in conjunction with clinical information, such as patient history, physical examination, and other diagnostic tests like echocardiography. Echocardiography remains the gold standard for diagnosing and quantifying LVH.
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