Your DH's enlarged heart is most likely due to his hypertension...and hypertension is exacerbated by sleep apnea. Sometime sleep apnea is a sole cause of high blood pressure. I happen to have a brilliant cardiologist sitting next to me reading this (I'm at work) and he concurs...as much as he can without seeing your husband and taking a full history.
My DH's heart was
slightly enlarged on his chest xray last month due to him having untreated high blood pressure (usually 145/90) for 8-9 years. He started on a calcium channel blocker with a diuretic, and his heart will probably never be back to normal, but it should shrink a bit. I am an RN in a cardiac ER, so I know that eventually he will need an echocardiogram and stress test...but not in the near future because he's extremely well controlled with his Diovan (we're talking 110/60 now) and has no chest pain at all anymore, no SOB with exertion, basically asymptomatic.
Your PMD has probably known all along that this was coming...a heart in a body of a person that is hypertensive gets bigger and less contractile over the years just because it works so much harder...it's a big muscle. I don't doubt that your husband will probably get a 2-D echo of his heart to check output sometime soon, but I wouldn't necessarily freak out because his heart is a tad enlarged. On the other hand, I wouldn't ignore it, and make darn sure that his BP is well controlled, uncontrolled HTN leads to all sorts of nasty things like congestive heart failure and kidney failure.
Keep us posted, hopefully everything will work out okay.