Electrocardiographic axis generally refers to the average QRS electrical axis, which is the sum of all the instantaneous vectors during ventricular depolarization, and leftward deviation of the electrical axis means that the electrical axis is between -30 degrees and -90 degrees. The leftward deviation of the electrical axis means that the electrical axis of the heart is between -30 degrees and -90 degrees. There are many reasons for the formation of leftward deviation of the electrical axis, such as short and fat people are prone to leftward deviation of the electrical axis, the elderly are prone to leftward deviation, and in the position of the chest cavity, if the heart position is shifted to the left, the electrical axis will be leftward deviation. In hypertensive patients with left ventricular hypertrophy, cardiomyopathy and myocarditis may also cause leftward deviation of the electrical axis. Patients with leftward deviation may experience chest pain, chest tightness, precordial discomfort, palpitations, heart failure, and may even develop A.S. syndrome or cardiogenic shock. If the condition of eccentricity continues to progress and the primary disease is not treated in a timely manner, the heart may become over-hypertrophied and lead to serious heart failure. If the patient has left deviation of the electrical axis, it is recommended to go to the hospital in time, find out the cause of the disease, and actively cooperate with the doctor to take appropriate treatment.