Undergone angioplasty with insertion of stent on 15.05.2013. Can I go for hair transplantation?

Likely. Hair transplant would be considered a fairly low-risk procedure. Depending on the person who is doing the transplant for you, they may want you to discontinue Plavix (clopidogrel) or similar medication, if you're still on it. Generally, most can discontinue Plavix (clopidogrel) or similar medication after about 12 months of implantation of stent. Discuss with your cardiologist.
Great question! Generally drug coated stents these days necessitate one year of aspirin and Plavix (or Brilinta (ticagrelor) or Effient). I usually stop the latter agent after one year, and that frees the patient up for more elective procedures that might otherwise not been safely done on these aggressive anti platelet agents. The person performing the procedure will probably want a clearance letter from the cardiologist.