The physician studies the pattern

The physician studies the pattern on the paper to see if the heart rhythm is normal

And what's next?

Okay... Was the physician able to determine if the patient was dead or alive?

Yes it could be. Assessment could be through auscultatory method, that is listening to the heart sounds rate and rhythm with the use of the stethoscope. This is real time. Clinicians also make judgment visually through the study of documented diagnostics like EKG - which is most important for comparison purposes from an old data.