There are two sub-types of second degree heart block:
Second degree heart blockĪ second degree heart block is where there is a series of increasing delays in the time that it takes the AV node to send the pulse to the ventricle, until eventually a heartbeat is skipped. First degree heart block does not usually cause any noticeable symptoms and treatment is rarely required. First degree heart blockĪ first degree heart block is where there is split-second delay in the time that it takes electrical pulses to move through the AV node. These are described in more detail below. There are three main types of heart block: However, it can result in an abnormally slow heartbeat (bradycardia), leading to the body’s organs and tissue becoming deprived of oxygen. The AV node conducts the impulse into the two lower chambers of the heart (the ventricles).Ī heart block occurs if the transmission of the impulse between the AV node and the ventricles is interrupted.Ī heart block does not mean that the heart stops beating altogether, because other ‘back-up’ systems can take over. The impulse is then sent to another selection of cells that are known as the atrioventricular node (AV node).
The SA node is often referred to as a natural pacemaker because, like artificial pacemakers, it generates a series of electrical impulses at regular intervals. The contractions are triggered by electrical impulses that are generated by a selection of specialised cells that are known as the sinoatrial node (SA node). When the heart beats, the heart muscle contracts (pulls inwards) in order to pump blood around the body. The most serious type of heart block known as a complete, or third degree, heart block will have symptoms, but often those with less serious heart block can have symptoms too. A heart block is when the electrical impulses that control the beating of the heart muscle are disrupted.