Cardiac resynchronization therapy (CRT) helps restore a normal heart rhythm by pacing both sides of the heart. CRT delivers a steady pattern of small electrical pulses to the heart muscle through the leads. These small pulses encourage the heart to beat in a regular rhythm. CRT generally stimulates the right atrium first and then both the left and right ventricles. The time between the stimulation of the right atrium and the left and right ventricles is programmed to maximize the heart’s pumping action. Because CRT paces both ventricles, the heart device controls when each side of the heart contracts. This control helps your heart maintain a normal rhythm.