I'd suggest taking just one hit, and see how you feel. As we age, tolerance decreases.

My heart rate goes to 100 or more when I vape even a small amount of high-altitude Sativa.

You may have a mitral valve prolapse, or murmer, which are very common and not usually dangerous. I have them.

Try eating fish at least a couple of times a week, if you don't already, or if you don't eat fish take fish oil capsules, or krill oil. I also take extract of hawthorne berry, and Co-Q10, both of which help the heart to normalize.

The best idea would be to see a cardiologist and get your heart checked out. You don't have to mention the weed smoking.