Time : 2023-07-03
1. The ECG axis generally refers to the average QRS axis, which represents the magnitude and direction of ventricular depolarization.
2. The right axis deviation of the ECG means that the main wave direction of lead I is downward, and the main wave direction of lead aVF is upward.
The normal ECG axis points down to the left, between 0°-90°. Right axis deviation mainly means that the main wave direction is downward in lead I and the main wave direction is upward in lead aVF. If the main wave direction of lead I is downward, the direction of the electric axis is located in the negative direction of the lead, that is, the second and third quadrants; if the direction of the main wave of lead aVF is upward, the direction of the electric axis is located in the positive direction of lead aVF, that is, the second and third quadrants. third and fourth quadrants. The two overlap each other in the third quadrant (+90°-+180°), and the electric axis deviates to the right.
Right-side deviation of the cardiac axis is generally affected by the anatomical position of the heart in the thoracic cavity, the mass ratio of the two ventricles, the function of the conduction system in the ventricle, the conduction state of the excitation in the chamber, age, body shape and other factors. Right axis deviation can be seen in subjects with normal variation. Right ventricular hypertrophy is an important cause of right axis deviation.
Another reason is myocardial infarction of the left ventricular side wall. When the ventricular depolarization loses the normal vector of depolarization to the left during lateral wall myocardial infarction, the electric axis deviates to the right; left posterior branch block is rarely the cause of right axis deviation reason. In patients with chronic lung disease (emphysema or chronic bronchitis), the ECG often shows right axis deviation.
Finally, it should be noted that the sudden appearance of the mean electrical axis of the QRS to the right (does not necessarily cause a true rightward deviation of the electrical axis), should consider whether there is the possibility of acute pulmonary embolism.