What would cause ventricular irrability?

Cellular level: Irritability refers to enhanced ability of the heart cells to generate an electrical impulse (known as action potential). This happens when a substance referred to as cyclic amp increases in the heart cell causing increased entry of calcium into the cell. With increased calcium, the heart cell both fire impulses rapidly as well as contract vigorously. I will go over some of the causes next.

Causes are many many: Some of the causes that may increase irritability include anything that results in high adrenaline levels (fear, anxiety, dehydration, pain, anemia , severe other illness etc.), low potassium and magnesium levels, high calcium levels, medication such as cold remedies with decongestants, excessive alcohol and caffeine, inflammation or injury to the heart muscles as in heart attack and myocarditis.