Why should you always hook up to surface ECG rather than relying solely on the FF-IEGM?

Why should you always hook up to surface ECG rather than relying solely on the FF-IEGM?

• A. FF-IEGM is biased
• B. FF-IEGM is unbiased
• C. FF-IEGM is unaffected by lead orientation
• D. FF-IEGM is diagnostic only

Answer: (A)

The key idea is that far-field intracardiac electrograms are biased and don’t provide a complete, reliable picture on their own. Far-field signals come from distant parts of the heart and can be distorted by the catheter’s position, lead orientation, filtering, and nearby electrical activity. That means the timing and morphology you see in a FF-IEGM can mislead you about what’s actually happening in the heart’s rhythm. A surface ECG, by contrast, gives a global view of cardiac electrical activity in real time and serves as a standard reference for rhythm interpretation. By comparing FF-IEGM with the surface ECG, you can correctly relate intracardiac events to the overall rhythm, confirm conduction patterns, and avoid misinterpretation that could arise from biased intracardiac signals. So the best answer notes that FF-IEGM is biased. The other statements aren’t correct: FF-IEGM is not unbiased, it can be affected by lead orientation, and FF-IEGM by itself is not diagnostic.

The key idea is that far-field intracardiac electrograms are biased and don’t provide a complete, reliable picture on their own. Far-field signals come from distant parts of the heart and can be distorted by the catheter’s position, lead orientation, filtering, and nearby electrical activity. That means the timing and morphology you see in a FF-IEGM can mislead you about what’s actually happening in the heart’s rhythm.

A surface ECG, by contrast, gives a global view of cardiac electrical activity in real time and serves as a standard reference for rhythm interpretation. By comparing FF-IEGM with the surface ECG, you can correctly relate intracardiac events to the overall rhythm, confirm conduction patterns, and avoid misinterpretation that could arise from biased intracardiac signals.

So the best answer notes that FF-IEGM is biased. The other statements aren’t correct: FF-IEGM is not unbiased, it can be affected by lead orientation, and FF-IEGM by itself is not diagnostic.