What does QRS axis left deviation mean?

Apr 17, 2023 Source: Cainiu Health

Dr. Tian Hongbo

Introduction

The QRS axis refers to the direction of the QRS complex in the electrocardiogram (ECG). If the QRS axis is leftward deviated, it indicates that the dominant direction of cardiac electrical activity is toward the left. Left axis deviation may have various causes, including ventricular hypertrophy, left ventricular enlargement, left bundle branch block, and others. Additionally, it could also be caused by cardiac rotation.

QRS axis refers to the direction of the QRS complex in the electrocardiogram (ECG). If the QRS axis is leftward deviated, it indicates that the dominant direction of cardiac electrical activity is toward the left. Left axis deviation of the QRS may have various causes, including ventricular hypertrophy, left ventricular enlargement, left bundle branch block, and others.

1. Ventricular Hypertrophy

Ventricular hypertrophy refers to thickening of the ventricular wall, causing the heart's electrical activity to shift to the left. It is usually caused by conditions such as hypertension, myocardial disease, or valvular disorders.

2. Left Ventricular Enlargement

Left ventricular enlargement refers to an increase in the size of the left ventricle, leading to a leftward shift in cardiac electrical activity. It is commonly caused by hypertension, aortic valve stenosis, and similar conditions.

3. Left Bundle Branch Block

Left bundle branch block refers to an interruption or delay in the conduction system of the left bundle branch, resulting in a leftward deviation of cardiac electrical activity. It is typically caused by myocardial infarction, myocarditis, or related conditions.

In addition, left axis deviation may also result from cardiac rotation or positional changes. It is recommended to analyze the patient's medical history, physical findings, and other test results to determine the specific underlying cause and provide appropriate treatment.

View All

Which is more serious: left or right axis deviation on ECG?

Left axis deviation is more serious than right axis deviation. The electrical axis usually refers to the mean QRS axis, which is the resultant of all instantaneous vectors during ventricular depolarization and indicates the direction and magnitude of the average ventricular electrical potential over the total duration of depolarization. Right axis deviation is commonly seen in normal individuals, whereas left axis deviation often suggests an underlying cardiac abnormality.

View Full Answer

Normal QRS interval range

The normal range of the P/QRS/T waves on an electrocardiogram (ECG) primarily refers to the QRS axis, which normally falls between −30° and +90°. A more negative value indicates left-axis deviation—commonly associated with left ventricular hypertrophy—while a more positive value suggests right-axis deviation. Interpretation must be integrated with the patient’s clinical history and overall ECG findings. However, structural cardiac abnormalities cannot be definitively diagnosed by ECG alone; echocardiography is required for confirmation.