Alcohol when ingested acts acts as an stimulant of CNS, hence resulting in increased heart rate
, as time passes it 's metabolized in the liver
in sugar and than to fat, and now it begins to act as a depressant of CNS, AND there is fall of heart rate.
The 90 bpm is due to a reflex phenomena, and an undesirable symptom.
You please better leave it immediately for your own good, because when health is lost it never comes back, honour the Blessings of God; as more than 40% of bed is occupied in hospitals due to complication/s of alchololism.
GOODMAN GILLMAN PHARMACOLOGY TEXT BOOK.