Leftward deviation of the electrical axis in sinus rhythm is usually a normal physiological phenomenon, which does not have much effect on the body. The leftward deviation of the electrical axis in normal subjects has a certain clinical significance and needs to be considered in the context of the patient’s clinical condition. There are a number of factors that influence the direction of the electrical axis of the heart, including age, body size, the ratio of the right and left ventricles of the heart, and the functional status of the bundle branches. If there is only leftward deviation of the electrical axis, and there is no evidence of cardiothoracic disease, and there is no other intraventricular block, the leftward deviation of the electrical axis can be considered to be of no pathological significance. Leftward deviation of the electrical axis in sinus rhythm is commonly seen in the elderly with a leftward deviation of the ECG axis, in short and obese people with a tendency for the cardiac electrical axis to be leftward, and also when the heart position moves to the right, the electrical axis may be rightward, or else leftward. In addition, the right ventricular hypertrophy is usually rightward biased, the left ventricular hypertrophy is usually leftward biased, and lastly, in left anterior branch block, the cardiac axis is leftward biased.