Editing Sinus node dysfunction (section)

==Causes==
Sinus node dysfunction can be caused by intrinsic and extrinsic factors that affect the normal functioning of the sinus node. Intrinsic causes can include degeneration, dysfunction, or remodeling of the sinus node while extrinsic causes can create or worsen underlying atrial arrhythmias.<ref name="Semelka20132" /> Intrinsic causes tend to be responsible for permanent sinus node dysfunction while extrinsic causes are more commonly temporary.<ref name="Semelka20132" />

=== Intrinsic causes ===
Age-related degenerative fibrosis of the sinus node is often identified as the most common intrinsic cause.<ref name="Semelka20132" /><ref name="John2016" /> Other intrinsic causes include inherited ion channel dysfunctions, remodeling diseases such as [[heart failure]] and [[atrial fibrillation]], infiltrative diseases such as [[sarcoidosis]], [[amyloidosis]], [[Hereditary haemochromatosis|hemochromatosis]], and [[connective tissue disease]]s, inflammatory etiology such as [[rheumatic fever]], [[Chagas disease]], and [[Lyme disease]], as well as atherosclerotic and ischemic changes to the sinus node artery.<ref name="Semelka20132" /><ref name="John2016" />

Inherited sinus node dysfunction has been associated with mutations of the gene responsible for the formation of the alpha subunit of the sodium channel ([[SCN5A]]).<ref name="Semelka20132" />

=== Extrinsic causes ===
Common cardiac pharmacology such as [[Beta blocker|beta-blockers]], [[calcium channel blocker]]s, [[digoxin]], sympatholytic medication, and other antiarrhythmics can alter sinus node function to create an arrhythmia such as sick sinus syndrome. Electrolyte abnormalities such as [[hyperkalemia]], [[hypokalemia]], and [[Hypocalcaemia|hypocalcemia]] can also alter normal sinus node functioning. [[Hypothyroidism]], [[Hypoxia (medical)|hypoxia]], [[hypothermia]], and various toxins have also been associated with sinus node dysfunctions.<ref name="Semelka20132" /><ref name="John2016" />