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Sick sinus syndrome (SSS), also called sinus node dysfunction (SND), or sinoatrial node disease, is a group of abnormal heart rhythms (arrhythmias) presumably caused by a malfunction of the sinus node, the heart's primary pacemaker. Bradycardia-tachycardia syndrome is a variant of sick sinus syndrome in which slow arrhythmias and fast arrhythmias alternate. It is often associated with ischaemic heart disease and heart valve disease. ==Causes== Sick sinus syndrome is a relatively uncommon syndrome in the young and middle age population. It can result in many abnormal heart rhythms (arrhythmias), including sinus arrest, sinus node exit block, sinus bradycardia, and other types of bradycardia (slow heart rate).〔Semelka M, Gera J, Usman S. Sick Sinus Syndrome: A Review. Am Fam Physician. 2013 May 15;87(10):691-696.〕 Sick sinus syndrome may also be associated with tachycardias (fast heart rate) such as atrial tachycardia (PAT) and atrial fibrillation. Tachycardias that occur with sick sinus syndrome are characterized by a long pause after the tachycardia. Sick sinus syndrome is also associated with azygos continuation of interrupted inferior vena cava Abnormal rhythms are often caused or worsened by medications such as digitalis, calcium channel blockers, beta-blockers, sympatholytic medications, and anti-arrhythmics. Disorders that cause scarring, degeneration, or damage to the conduction system can cause sick sinus syndrome, including sarcoidosis, amyloidosis, hemochromatosis, Chagas' disease, and cardiomyopathies. Sick sinus syndrome is more common in elderly adults, where the cause is often a non-specific, scar-like degeneration of the cardiac conduction system. Cardiac surgery, especially to the atria, is a common cause of sick sinus syndrome in children. Coronary artery disease, high blood pressure, and aortic and mitral valve diseases may be associated with sick sinus syndrome, although this association may only be incidental. The mechanism is related to delayed escape. Congenital SSS can be due to mutations of the gene responsible for formation of Alpha subunit of sodium channel (SCN5A). A Russian study showed that the heterozygous variant of connexin 40 polymorphism gene variant is more frequent among patients with sick sinus node syndrome and their healthy relatives than in persons of control group, suggesting a link between the gene and the disease. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Sick sinus syndrome」の詳細全文を読む スポンサード リンク
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