Electrocardiogram (ECG) diagnostic abnormality of leftward deviation of electrical axis is a technical term used in ECG, which indicates the change of the electrical axis of the center of electrocardiographic vectors, which may be either physiological or pathological. If repeated ECGs indicate leftward deviation of the electrical axis, and there is no other abnormality, it may be due to physiological reasons, which are generally related to body size and age, for example, some short and fat people may have leftward deviation of the electrical axis. If it is a pathologic left deviation of the electrical axis, it is usually seen in patients with hypertension, left ventricular hypertrophy, resulting in the enlargement of the left heart and left deviation of the electrical axis, or myocarditis, coronary artery disease, heart failure, dilated cardiomyopathy, etc., which may lead to left deviation of the electrical axis in the case of left bundle branch conduction block. Leftward deviation of the electrical axis may also occur in myocardial infarction. If the electrocardiogram indicates left deviation of the electrical axis, it is necessary to go to the hospital for timely examination, such as cardiac ultrasound, etc., to find out the cause of the disease, and actively carry out the treatment to avoid delaying the condition.