Cardiac resynchronization therapy refers to the addition of left ventricular pacing to conventional pacemaker therapy, using biventricular pacing to correct the patient’s cardiac function, improve the patient’s clinical symptoms, improve work tolerance and quality of life, and thereby provide a definitive correction of heart failure. Cardiac resynchronization therapy is indicated for patients with heart failure classified as Grade 3 or lower in cardiac function, as well as Grade 4 patients who do not require bed rest, have an ejection fraction of 35% or less on cardiac ultrasound, and have an electrocardiogram with a QRS wave group greater than or equal to 0.12 seconds. Patients with heart failure who meet the above criteria are eligible for cardiac resynchronization therapy, which can lead to a very clear improvement in cardiac function in heart failure patients.