Coloured X-ray of the chest of a 49 year old male patient with severe heart failure. The patient has prosthetic aortic and mitral valves (white rings at centre) in his heart as well as a pacemaker (top left). The pacemaker supplies electrical pulses to the heart to keep it beating regularly. There is also pleural effusion of the right lung (at left). Pleural effusion is the presence of excess fluid in the pleural cavity (between the layers surrounding the lungs). It can impair breathing and is common in patients with heart failure.