It's only good to walk away if things get out of hand and to avoid a physical altercation it's never a good idea to walk away without communicating with your mate what the issue or issues are and working them out. Communication in one of the most important aspects of a relationship and if you are not able to communicate your feelings and the problems within the relationship then you will never work those issues out, Whomever said it was best to walk away was not giving you the correct way of solving the problem it will only make the problem more intense and more stressful for you both it's better to talk it out than to sit in silence and then have a huge blow up about everything all at once. What you both need to do is sit down with each other and one at time say what your issues are and the other not interrupt and listen to each other and then talk through a solution to that problem.
If you are not communicating your feelings then he won't know how you feel about things and it's never healthy to hold in pent up anger that could be one of the reason he has heart issues but it's not your fault that he has the heart issue. You need to talk this out and not stop talking until this is ironed out. What you could do is ask your husband what about you bothers him this way he is feeling as though he is being heard and will be more willing to hear you out also and if you do not agree with something he says wait until he is finished talking to voice your disagreement and then follow that with why you disagree this way he won't feel dismissed and will continue to show you the same respect that you showed him. You should both go by the old saying "Never go to bed angry" there is a reason they say that it's not healthy for the relationship and it may not be healthy health wise either. Even if one or the other apologize for any hurt feeling but always make sure that you go to bed on good terms. You never want to live with regrets like if something were to happen to either of you, you don't want to live the rest of your life thinking that you left things unsaid.
You will not fix this overnight and you have to take baby steps towards correcting the issues and don't lose patience if things don't work themselves out right away with any marriage with issues you have to take the time and make the effort to work things out before they get worse and walking away is never the answer that is just masking the issues and they will definitely come up again so you might as well nip them in the bud now.