dear u have to take acitrom becoz u r more prone to clot formation due to mechanical valve in urs body,Acitrom is an anticoagulant that functions as a vitamin K antagonist .The only common side effect of acitrom is haemorrhage (bleeding).All types of bleeding occur more commonly, but the most catastrophic ones are those involving the brain (intracerebral hemorrhage/hemorrhagic stroke) and the spinal cord.A rare but serious complication resulting from treatment is skin necrosis and gangrene of limbs ,Osteoporosis,Calcification of valves and arteries.All these side effects u can avoid by maintaing INR between 2 and 3 and strict dietary modification like avoiding eating substances containing vitamin k like green leafy vegetables