That's a common response to smoking weed. And it may be partially a response to smoking itself and not so much to weed. But basically, you had a sort of "adrenergic" response (as if you'd had a burst of adrenalin) and felt your heart respond to that. Before the THC and CBD and other cannabinoids kick in, you get some vaso-constriction right after smoking. After a time, that constriction lessens and the veins and arteries in your body relax and dilate. But during that first vaso-constriction phase, you feel your heart race. This is when folks have panic attacks and jitters. It's when they feel an energetic high. And this response is especially likely when you're smoking more Sativa-heavy strains of weed, which have a stimulant-like effect.

One of the lesser known facts about weed smoking is that within that first hour or two of smoking, your risk of heart attack increases by about five times what it normally is. You're also at greater risk of arrhythmias during this time. Although lots of people enjoy touting the fact that no one has ever died from smoking weed, the medical community knows that plenty of people have likely died from weed-smoking-initiated heart attacks. Only the official cause, of course, is a heart attack. But weed smoking does present some risks to the heart.

Go easy next time you smoke. Maybe try switching to a new strain. And make sure you're in good cardiovascular shape if you're going to be a smoker because if you're not, you may be at risk. (I'm guessing you're quite young and fairly healthy, but if you've been a cigarette smoker, that's already put you at some risk of cardiovascular troubles.) If all else fails, get a vaporizer and take your cannabis in that way. Good luck!