Have you contacted his cardiologist? What kind of medicines is he taking? I have read that licorice will increase BP. I found the below treatments for low BP on Medicine.net. I am sure that your husband's condition precludes him from using some or all of the medicines below:
ephedrine-oral
midodrine-oral, ProAmatine
norepinephrine bitartrate-injection, Levophed
yohimbine-oral, Aphrodyne, Viritab, Yocon, Yohimex
ephedrine-injectable
hawthorn (Crataegus laevigata)-oral
http://www.medicinenet.com/script/main/forum.asp?articlekey=1950&articletype=pharm
Digitalis will increase his ejection fraction and blood flow rate, if he is in or at a certain stage of heart failure, but will not necessarily increase his blood pressure due to decreasing his vascular bed resistance. It would seem as though it might stop the passing out with increasing the blood flow. I don't know how well his arrhythmia would respond to Digitalis.
Did you not receive instructions from the hospital for what to do upon discharge? Surely low BP was discussed concerning someone with CHF. I would call the damn hospital and demand information or call 911 and return him. Read the discharge instructions. See if there are directions to be followed if low BP occurs.
I certainly would check with your Cardiologist asap. It certainly could be too heavy medication dosage(s). I have passed out on two separate occasions, the beta blocker dose I was taking was too high.