Hello and welcome to Healthcare Magic. Thanks for your query.
in any form, be it tobacco or marijuana, will cause adverse health consequences. Especially, after a open heart surgery, smoking marijuana frequently is definitely going to cause him problems.
The increase in blood pressure and the slowing of his heart rate
are indeed concerning and need a proper evaluation. I would suggest that you inform the doctor about these symptoms as well as his marijuana smoking, so that appropriate remedial measure can be taken.
Wish you all the best.
Dr. Jonas Sundarakumar