disneystar, I know what you're going through - my dh collapsed with a heart attack three days before my ds was born. It was a horrible traumatic time for both of us and there is nothing really that anybody can say that can make things easier for you right now. And at least I didn't have other children to worry about which must be adding to your stress.
on the other hand, the good news is that your husband is alive and in the right place - being looked after in hospital. it will be a long journey for both of you for him to get back to health but now that he is in the system he should get the drugs and aftercare to make sure that long term he has a good recovery - I ended up thinking of it as a silver lining that he had had an attack when he did (horrible as it was) as it would have been SO much worse if the underlying condition had got worse and he'd had a fatal attack a year or two down the line. And like you, I'd always thought of dh as the fit,healthy and strong one.
as wmmchoc said - recovery can take a long time - from dh experience I would have said that 6 weeks was an absolute minimum, just to be getting back up and about. he went back to work at 3 months afterwards, part time orignially and that was too much too soon, but think he just wanted to do it to prove to himself that he was OK if you see what I mean. Rehabilitation takes time and sometimes by doing too much too soon you end up taking one step forwards and two steps back, so no matter how frustrating it is, make sure he doesn't try to rush it! 2.5 yrs on and dh still can get tired more easily and isn't back to his old self, he still has to take care with things.
If you can, try to make sure that dh gets to go on a rehab course or two (dh's was run by community and hospital physios) that cover physical and mental rehab, along with things like looking after yourself, what to eat, lifestyle changes etc. if you can go too, that would be great as tbh there is a lot to take in and your dh won't be feeling great and thus probably not taking it all in.
there is lots of useful info on the british heart foundation website, they also have lots of useful leaflets that we picked up from the cardiac ward.
definitely worth trying to see the cardiac consultant with your dh before he is discharged as previously mentioned. remember to ask if they think that there might be any inherited reason why your dh has had an attack so early - and if there is anything they can do to scan your children to check that they are not going to be similiarly affected.
also, make sure that when he is discharged, that you get some follow up numbers to call if you have any questions or queries or worries - it is very easy to get very worried by every little twinge and pain, most of the time the stress of it is probably worse than the little twinge but there can be after problems and being able to ring up the ward/cardiac nurse/etc who know your history will be a relief - they will be able to say 'don't worry' or 'ring for an ambulance' or something inbetween and that will put your mind at rest.
on a practical but horrible note - have you and your dh made wills? Incredibly difficult subject to bring up I know, but it is worth getting one done asap, if, god forbid, the worst should happen. doesn't have to be fully thought out or complicated - they can be changed after death by a deed of variation very easily. but if there is no will, ie he is intestate, there are rules that have to be followed regarding the distribution of your dh assets which can cause lots of problems down the line as for example, if you own your own house and you have children, a part of it can end up in trust for them, leaving you sooner or later without the full value of your house. I am oversimplifying horribly here - but there are some horror stories on mumsnet of people that this has happened to that adds lots of problems at an already incredibly stressful time. so throw together a very simple document and get it signed and witnessed (am sure the nurses will be used to helping with this), do one for yourself at the same time, and then it is one less thing to worry about.
does your dh have any kind of insurance cover or health cover? Often these have to be initiated within a month of the problem starting, if not sooner (crazy, as it is the last thing you need to be worrying about at the time and it is not like you are up to doing much yourself) but if he has, check what the timescales are. guess this particularly applies to your holiday as it is so imminent.
you might find that dh also becomes more susceptible to bugs that he wouldn't have got previously - and lots of over the counter medicines for coughs and colds etc can't be taken with lots of the heart drugs that he might be taking - so it is worth double checking everything with the pharmacist and maybe asking the consultant for names of over the counter drugs that he could take for common conditions, just so you are ready.
it might also be worth getting yourself to the doctor or your midwife to get checked out if you are feeling stressed and worried about the effects this is all having on your pregnancy. they may very say that there is nothing to worry about from your health and baby's health point of view but it will mean that they are aware of the situation and able to keep an eye on you, plus they may well be able to offer some sort of help (practial and/or counselling, extra pg appts etc) and talk through what to expect with your dh and what support services they offer, etc. Remember that you will need support too - not just because you are pg - but because this has big knock on effects on you too, so don't be afraid to accept help.
sorry, this has turned into a really long post. I hope it doesn't read too much like doom and gloom but provides a little practical support at a moment when that is the last thing you want to be thinking of yourself. You are both in a scary place at the moment but you will end up stronger and wiser at the end of it, and you may well find that you all end up healthier and happier too as a result of the changes that you make to your lives.
Big hugs and let us know how your dh gets on. Let me know if you have any more questions and I'll try to answer them.