For whatever it’s worth, I used Metoprolol sucessfully for 18-19 years. My heart rate stayed very reliably in the 50s.

A doctor in the Republic of Georgia introduced me to the use of coffee off the circadian rhythm cycle. At night when I woke up with heart symptoms, this doc prescribed a strange use of coffee to stimulate the heart at the wrong time in the sleep cycle. Oddly it worked for me. Low light or none plus coffee to stimulate the heart amounted to mixed signals to the brain. The darkness and normal sleep patterns say you should sleep now. But the stimulant in the coffee says to stay awake. For me, the result was peaceful sleep with good breathing. Not saying this would work for anybody else, but it could be worth a shot,

Coffee after midnight is not the same thing as coffee at dawn. Ask Balzac if you get the chance.