Pacemaker and heart pump. X-ray of the chest of a patient who is waiting for a heart and lung transplant. They have a pacemaker and a left ventricular assist device (LVAD) fitted. The left ventricle is the main pumping chamber of the heart, responsible for the circulation of oxygenated blood through the body. When it stops working properly, an LVAD is temporarily implanted to assist blood circulation. A pacemaker is a device that supplies electrical impulses to a malfunctioning heart so that it beats normally.