usually there are a number of smaller factors that compound and cause a lot of cumulative strain on the heart. vasoconstriction is the worst for me, but it might be different for you. other things to look out for are dehydration, low potassium levels (heart arrhythmia, dehydration), not enough protein, not enough vitamin c, exerting yourself more than you would sober, etc. personal experience tells me that most of these issues are either subtle or nonexistent until i am vasoconstricted for too long or if i exert myself too much while vasoconstricted. i usually don't get chest pain at all if i take a vasodilator with the initial dose, but sometimes i might forget to redose later. grapeseed works well for me. coq-10 also seems to help with general chest pain. niacin (not the flush free kind) is a good one too, but it can't be taken as many times per day, so i save it for the end of the experience usually. i used to take l-arginine, but now i just have a couple raw eggs instead