What could cause an ECG pulse rate and a pulse rate measure on the wrist to be different?

The ECG shows atrial fibrillation with 80 QRS/min. It is irregularly irregular. The pulse is listed a 174/min.

I disagree with the above answers. Heart RATE and heart RHYTHM are separate things. You can have atrial fibrillation, which is an abnormal heart RHYTHM and the heart RATE can be fast (uncontrolled) as in when it is 174 or slow (controlled) as in when it is 80. It is possible for the heart rate and/or rhythm to flip back and forth between controlled and uncontrolled or afib and normal sinus rhythm.
The other issue is that the ECG and palpating the radial pulse are different ways of measuring how rapidly your heart is beating. Palpating the wrist performs this function by feeling the sensation of the mechanical ventricular contraction which is pushing the blood from the heart to the wrist radial artery. The ECG does this by measuring the number of times there is an R wave which corresponds to the electrical depolarization leading to mechanical ventricular contraction. So the ECG is an indirect measurement while palpation is a direct measurement.
Sometimes the heart rate can be so fast that there is not time for the ventricle to fill with blood so that when it contracts it will register an R wave on the ECG but because there is insufficient blood in the ventricle you may not feel the sensation of a pulse at the radial artery. This will result in the pulse number being low and the ECG number being high.
The converse is when because of the rapid irregularly irregular abnormal rhythm of atrial fibrillation, the ECG is unable to always accurately determine when there is an R wave and it will undercount them while the pulse at the wrist is giving a higher more accurate count.
This is a bit complex so the important things to understand are that treatment of atrial fibrillation begins with RATE control and once this is achieved, the RHYTHM often will convert to normal on its own. If it does not, then decisions can be made on how to address RHYTHM control.

Malfunction.

Does the patient actually have a radial pulse of 174bpm? If so, that patient needs some antiarrhythmicsand/or cardioversion immediately. Contact your attending.

Does the monitor just say 80bpm, or are the complexes far enough apart so that it actually looks like it could be 80bpm. If so, somebody screwed up when taking the pulse... they should probably be talked to.

If the ECG shows a very rapid rate but only says 80bpm, you need to go by the actual rate. If the complexes are really close together, GRAB AN ATTENDING and get this patient the appropriate meds.

Is the attending aware that the patient is in a-fib? Is this a new onset?

These are all things that you really do need to know.


DO NOT TAKE MEDICAL ADVICE OFF OF THE INTERNET. IF YOUR PATIENT IS IN DISTRESS, ALERT A PHYSICIAN THAT CAN DO SOMETHING ABOUT IT.

In all probability, the person counting the radial pulse got it wrong. In this case, the ECG would be more accurate...if the pulse was counted at the same time as the ECG tracing, that is.