<unk>  <unk>  is a disorder in the heart's rhythm due to a fault in the natural pacemaker. This is caused by an obstruction – a<unk>  – in the electrical conduction system of the heart. Sometimes a disorder can be inherited. Despite the severe-sounding name,<unk>  may cause no symptoms at all in some cases, or occasional missed heartbeats in other cases (which can cause light-headedness, syncope (fainting), and palpitations), or may require the implantation of an artificial pacemaker, depending upon exactly where in the heart conduction is being impaired and how significantly it is affected.<unk>  should not be confused with other conditions, which may or may not be co-occurring, relating to the heart and/or other nearby organs that are or can be serious, including angina (heart-related chest pain), heart attack (myocardial infarction), any type of heart failure, cardiogenic shock or other types of shock, different types of abnormal heart rhythms (arrhythmias), cardiac arrest, or respiratory arrest. In severe cases where the heart's ability to control and trigger heartbeats may be completely ineffective or unreliable,<unk>  can usually be treated by inserting an artificial pacemaker, a medical device that provides correct electrical impulses to trigger heart beats, compensating for the natural pacemaker's unreliability. Therefore,<unk>  frequently has no effects, or mild and occasional effects, and is not life-threatening in the vast majority of cases, and is usually treatable in more serious cases. The human heart uses electrical signals to maintain and initiate the regular heartbeat in a living person; incorrect conduction or interference from external sources can lead to mild or serious symptoms depending upon the location of the<unk> age and how severely conduction is being<unk> ed. Conduction is initiated by the sinoatrial node ("sinus node" or "SA node"), and then travels to the atrioventricular node ("AV node") which also contains a secondary "pacemaker" that acts as a backup for the SA nodes, then to the bundle of His and then via the bundle branches to the point of the apex of the fascicular branches.<unk> ages are therefore classified based on where the<unk> age occurs - namely the SA node ("Sinoatrial<unk> "), AV node ("AV<unk> " or AVB), and at or below the bundle of His ("Intra-Hisian" or "Infra-Hisian<unk> " respectively). Infra-Hisian<unk> s may occur at the left or right bundle branches ("bundle branch<unk> ") or the fascicles of the left bundle branch ("fascicular<unk> " or "Hemiblock"). SA and AV node<unk> s are each divided into three degrees, with second-degree<unk> s being divided into two types (written either "type I or II" or "type 1 or 2"). The term "Wenckebach<unk> " is also used for second degree type 1<unk> s of either the SA or AV node; in addition second-degree<unk> s type 1 and 2 are also sometimes known as " Mobitz 1" and "Mobitz 2". Clinically speaking, the<unk> s tend to have more serious potential the closer they are to the "end" of the electrical path (the muscles of the heart regulated by the heartbeat), and less serious effects the closer they are to the "start" (at the SA node), because the potential disruption becomes greater as more of the "path" is<unk> ed" from its "end" point. Therefore, most of the important<unk> s are AV nodal<unk> s and infra-Hisian<unk> s. SA<unk> s are usually of lesser clinical significance, since in the event of SA<unk> , the AV node contains a secondary pacemaker which would still maintain a heart rate of around 40 - 60 beats per minute, sufficient for consciousness and much of daily life in the majority of individuals.
Heart block
Torsades de pointes
Sinus arrhythmia
Angina
Angina 
Atrial fibrillation
Carditis
Broken heart