A biventricular pacemaker is a medical device that stimulates the heart's lower chambers (ventricles) to beat at the same time. It is commonly used to treat heart failure. The device is also known as a cardiac resynchronization therapy (CRT) pacemaker, and may sometimes be referred to as a triple-chamber pacemaker. The term "biventricular pacemaker" is often used interchangeably with "CRT pacemaker", but both terms refer to the same medical device. Other synonyms for the term may include "resynchronization pacemaker", "cardiac stimulator", and "dual-chamber pacemaker". Regardless of the term used, a biventricular pacemaker remains an important and life-saving device in the treatment of heart disease.