(5/x) Finally, here's a case where the ECG heart rate that is displayed LIES!
In this case, you can see that the patient has a bigeminy. The ECG is showing a heart rate of 91, however, there is only ONE arterial line beat for every two electrical beats. Thus, the effective heart rate is actually ~45 BPM.
This is surprisingly common, and without arterial line can be missed. Another clue can be looking at the pulse ox pleth tracing.
This also happens with rapid atrial fibrillation where the HR is reading 130s but only 70-80BPM if you look at the arterial line. That is another indication to me that potentially rate/rhythm controlling the patient will help their hemodynamics.