Every body s body chemistry is different. I knew a guy who would smoke a bowl of meth and go to sleep. The fundamentals of amphetamines is that it creates the secretion of adrenaline into your blood stream. This does a number of things including, obviously speeding up the heart rate dramatically. If the 3 lines were done together, there were large lines, and if your tolerance was somewhat low, the sudden shock to your system could have created a higher pressure around your heart. this would restrict the volume of blood going through your arteries and creating the faint feeling and the pressure in your chest.