It sounds like they did a heart catheterization. That's usually one of the early procedures they'll do when they think somebody has had a heart attack. They may insert a stent which will help keep the coronary artery open or they may have inserted a balloon which will stuff the crap blocking things tighter against the walls of the artery, leaving a wider opening for blood to flow through.
When you say his heart is only operating at 30%, two possibilities come to mind: the first is that his "ejection fraction" is only 30% and so his heart isn't doing a good job moving blood. That can be improved with medication. The other is that maybe you misunderstood what they said and that one or more of his coronary arteries is only 30% open due to a lifetime of fried chicken, french fries, all the joys in life. In that case a cigarette can trigger the heart attack because the nicotine will cause the vessel to constrict. A 70% blockage combined with nicotine constriction may be enough to trigger the attack.
He needs to quit smoking if he does. When somebody says that cigarettes can kill you, in his case they're not kidding.
I'm sorry he's having a tough time of it. How old is he? Generally speaking, the older you are when you have a heart attack, the better your chances are of surviving it. The heart will develop other routes for blood flow (called collateral circulation) if you live long enough with poor circulation. That's why an old bastard like Dick Cheyne can keep surviving them while some young dude on the tennis court just drops dead.
Give Lucky my best and tell him the odds are in his favor. Life will return to normal; just not this week.