Narrowing heart vessel?

My husband was diagnosed with a "smoker's vessel" but he is not a smoker. He has an occasional cigar in the summer - 3 months out of the year. He had a heart cathetirization and found nothing wrong-no blockage anywhere in his arteries. No high blood pressure, he never had a heart attack, the ekg came back clear and his stress tests didn't show anything. Is a narrowing or "smoker's vessel" treatable? We were told that they couldn't put a stent in because the artery was too narrow. He can't have a by p surgery because there is no blockage. Are there any cardiologists out there who can shed some light to this? Is this hereditary? His father always had chest pains and kept taking antacids. He lived to be 87, My husband just turned 59. Thanks.