The rhythm of each heart beat is controlled by electrical pulses. These signals coordinate and synchronize the contraction of the atria and of the ventricles. They also provide the electrical sequence of activation that causes the ventricles to contract in a coordinated manner. In heart failure, this electrical sequence of activation is distorted A new surgical treatment can now be offered as an option to patients suffering from heart failure: cardiac resynchronization therapy (CRT). Implantable devices designed for CRT stimulate the two ventricles of the heart to beat at the same time by delivering tiny electrical pulses to both sides. This therapy is intended for patients with moderate to severe heart failure who also have ventricular dysynchrony, a condition in which the two ventricles are not beating synchronously. An example of a CRT device is a CRT pacemaker, which is a more advanced version of a standard pacemaker and is about the size of a pocket watch. Once implanted in the chest, the CRT pacemaker not only helps the heart keep a normal rhythm but improves contraction pattern in the left ventricle, improving the overall efficiency beneath the skin, usually below the collarbone. The performance of CRT devices was studied during the course of several clinical trials. The study showed that the CRT devices provide proven quality-of-life benefits to patients and funded hope for an increased life span.