This first room is asking about Anatomy and Physiology concepts that are critical as the building blocks of critical thinking and clinical judgement. Let’s break down the riddle.

I'm a signal that travels in waves 
Across the heart, my pattern engraves. 
In the body's theater, a rhythmic plot 
Electrical impulses, a lively lot. 
Nurses watch me on a monitor's trace 
Deciphering patterns with skilled grace. 
From atria to ventricles, I swiftly go 
A cardiac dance, a rhythmic flow 
In health and illness, I take the lead 
A waveform mystery for those who read. 
A cipher is used to crack the code 
5 letters to translate what has been showed 

The beginning of the riddle is describing the waveform found in an Electrocardiogram (EKG or ECG), however as we go further in the riddle we are actually being asked about the “cipher”. When analyzing an EKG/ ECG you must first identify the specific sections of the waveform. What is a universal language to identify the characteristic electrical activity of the heart. “5 letters to translate”.