Relationship to Pulse
Since the ECG attempts to describe what's happening in the heart, the presence of the QRS complex (i.e. ventricular contraction) should match the mechanical heart beat. It's uncommon for the electrical heart rate and the mechanical pulse to not match - but it does happen, especially in an emergency setting.
Always check for a pulse!
Regardless of the rhythm, always get into the habit of confirming that the patient's pulse matches the ECG reading.
Asynchrony between the pulse and the ECG rhythm could indicate fluctuations in cardiac output.
The biggest issue occurs when there is some form of organized electrical activity but no mechanical pulse. This is called Pulseless Electrical Activity (PEA).
Immediately start CPR! For PEA, defibrillation is not performed (especially if the ECG rhythm is "normal").
In Canada and the United States, treatment is based on the AHA/HSF Advanced Cardiac Life Support Cardiac Arrest algorithm:
For more information, check out the AHA ACLS Cardiac Arrest pathway here: