I have fainted once before but it was from too low of blood pressure. I have orthostatic hypotension which means I get low blood pressure from standing up too quickly. I see stars and have completely fainted.
Alcohol is a potent depressant of the central nervous system (brain in particular) and activates the inhibitory neurotransmitters in the brain. The acute effects of alcohol depend on the concentration of alcohol in the blood (directly correlated with the amount and time of drinking). Initially, alcohol generally produces feelings of relaxation and cheerfulness, but further consumption can lead to blurred vision and coordination problems. After excessive drinking, unconsciousness can occur and extreme levels of consumption can lead to alcohol poisoning and death.
Hence, it is definitely not due to stroke or heart attack. Inco-ordination and unconsciousness could occur after bouts of heavy drinking.