Attacks of unconciousness caused by the heart suddenly ceasing to pump enough blood to provide the brain with adequate oxygen: when the supply of oxygen-rich blood is interrupted for 15 seconds the patient turns pale and loses consciousness. As soon as the heart starts to pump enough blood again the brain receives more oxygen and the patient recovers. Stokes-Adams attacks are the result of disturbances in cardiac rhythm: total stoppage of the heart, extremely low heart rate and fibrillation. The latter condition does not cease spontaneously, and can only be corrected by electric shock. If the heart beats too slowly or not at all it must be stimulated by injection. An effective treatment is the fitting of a pacemaker, to ensure that heart rate remains above a certain minimum.