Heart block is a disorder of the heartbeat.
This interrupts the passage of impulses from the atria to the ventricles. There are various degrees of heart block. In first-degree block, the passage of impulses is delayed and there are no symptoms. In second-degree heart block, some of the atrial impulses fail to reach the ventricles that can cause the pulse to become irregular. In third-degree block, known as complete heart block, no atrial impulses reach the ventricles and the flow of oxygenated blood to the brain and the rest of the body is insufficient.