Pacemaker and coronary artery bypass surgical clips. X-ray showing a pacemaker (upper left) in a 78-year-old patient who has had coronary artery bypass surgery. Pacemakers supply electrical impulses along wires (long, thin) connected to the heart (centre left). These electrical impulses help to keep the patient's heart beating regularly. Surgical clips remain from the patient's coronary artery bypass surgery. This is where an implanted vessel diverts blood flow around a narrowed or blocked coronary artery, which improves blood flow and oxygen supply to the heart. This patient has also experienced pleural effusion, which is the presence of excess fluid in the pleural cavity (between the layers surrounding the lungs). This can impair breathing (by limiting expansion of the lungs), and is most commonly a result from heart failure or cancer.