How do you calculate? cardiac output?

Several: Can use 2d echo, mra of heart, and right heart cath. Cardiac output is the measure of how many liters per minute the blood is being circulated in the body.

Math: Cardiac out put is: co=hrxsv heart rate and stroke volume, which is the amount of blood ejected with each cardiac cycle. Sv is a little more complicated as it involves pre-load, afterload and contractility. Heart catheters and cardiac echo are the best ways to get the measurements.