Disturbance in the transmission of the electrical stimuli that cause contraction of the cardiac muscle. The stimuli originate in the walls of the right auricle and normally pass to the ventricles via the cardiac septum. If damage to a heart muscle impairs the functioning of this system, impulses from the auricles do not reach the ventricles, which slowly contract independently of the auricles, slowing down the heartbeat, and possibly causing the patient to faint. Treatment is by implantation of an artificial pacemaker to regulate the heart beat. Heartburn (pyrosis) Sharp burning feeling behind the breastbone resulting from the mucous membrane of the oesophagus coming in contact with gastric juices from the stomach. In contrast to the gastric mucous membrane, which is resistant to the very strong gastric acids, the mucous membrane of the oesophagus is not. Everyone suffers from heartburn occasionally, for example after a heavy meal, or even without a definite cause. If heartburn recurs regularly, it will usually be the result of a malfunction of the sphincter at the entrance to the stomach, and as a result gastric juices can flow into the oesophagus (reflux), especially when the person is lying down. Rupture of the diaphragm is an important cause of reflux. Another is increased pressure in the abdominal cavity, with gastric acid being squeezed upwards in consequence; this occurs, for example, in cases of obesity and during pregnancy.