that's not why they had to get up. It's because they were hitting the EPO so hard, their hematocrits would be like over 60% (60% red blood cells/mL of blood) and thus when their heart rate/cardiac output would drop during sleep (to very low levels typically of highly trained athletes...not because of the EPO) the blood would be too viscous and start to clot

so the low heart rates caused a problem for those abusing EPO, but wasn't a result of using EPO