They do not narrow the bloodvessels but dilate them. Psychedelics hardly enhance the activity of the cardiovascular system (comparable with 1 or 2 cups of coffee for most experiences). High dose LSD (400+ mics) produces shaking heart beats which are harmless but may come across as alarming if found for the first time or unexpected. A good mescaline experience may be accompanied with tachycardia, notorious vein expansion, tight feeling in the neck and a mild suppression of respiration. But it feels very natural and the Indians believed mescaline was a medicine to the heart, both physically and mentally, for any healthy person. I do know what they are aiming at. Smoking DMT can elevate heart pulse substantially for a brief moment priorly to the knock out. Mushrooms are the safest entheogens regarding palpitations. All the classical four do not produce vasoconstriction but there's always a (minor) change in blood pressure or pulse, harmless for a healthy being.
Oh and remember kids, don't smoke nicotine, hot drinks are not for the belly, sugar is worthless and saturated fats are wack. Therefore, suck a lemon. :mrgreen: