While it
would seem endogenous opioid peptides would reduce pain and heart rate,
allowing more time for ventricular filling, there a number of human studies
suggesting EOP levels do not correlate with blood pressure, heart rate, and
central venous pressure in cases of myocardial infarction. On the contrary, animal
studies suggest endorphins may augment ischemic damage during MI, and in animal
models of circulatory shock and heart failure opioid receptor blockade has been
shown to improve hemodynamic parameters and survival rates.