Nav1.5 kb. The gene consists of 28 exons, of which exon 1 and in part exon 2 form the 5’ untranslated region (5’UTR) and exon 28 the 3’ untranslated region (3’UTR) of the RNA. SCN5A is part of a family of 10 genes that encode different types of sodium channels, i.e. brain-type (Na1.1, Na1.2, Na1.3, Na1.6), neuronal channels (Na1.7, Na1.8 and Na1.9), skeletal muscle channels (Na1.4) and the cardiac sodium channel Na1.5. SCN5A is mainly expressed in the heart, where expression is abundant in working myocardium and conduction tissue. In contrast, expression is low in the sinoatrial node and atrioventricular node.
Sinoatrial block delayed or blocked on the way to the atria, thus delaying the atrial beat. (An AV block, occurs in the AV node and delays ventricular depolarisation). SA blocks are categorized into three classes based on the length of the delay. Sinoatrial blocks are typically well-tolerated. They are not as serious as an AV block and most often do not require treatment. In some people, they can cause fainting, altered mental status, chest pain, hypoperfusion, and signs of shock. They can also lead to cessation of the SA node and more serious dysrhythmias. In a first degree sinoatrial block, there is