This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S, Subject name: Medicine
Most common cause of arrhythmia is - 
Select and explain. 
A. Ischemic injury, B. Automatism, C. Trigered activity, D. heafailure
A: Ischemic injury
Answer: A: Ischemic injury 
Explanation: Ischemic injury is the most common cause of rhythm disorders, because of direct damage or due to the dilation of hea chambers with consequent alteration in conduction system firing. Far less common are inherited causes of arrhythmias. These are caused by mutations in genes that regulate various ion channels that regulate depolarization and repolarization of myocardial cells. Such channelopathies are impoant (but founately uncommon) substrates for fatal arrhythmias. They underlie some cases of sudden cardiac death. Ref : Harrisons 20th edition pg 1443