To my knowledge, having a heart attack, having stents placed or being on plavix should not disqualify someone from that type of license. However, if he experienced any events where he passed out (ie from an arrhythmia), this may prevent him from keeping his license, at least until he is stable for a number of months (I'm less familiar with this, but I've seen around a 6 month time frame).
Sorry CDL is a chauffesr drivers license needed for professional drivers i.e. tractor trailer, bus and etc.
Can you please define a cdl? I am not familiar with the term.