____ electrograms include both local and farfield signals and represent a summation of all cardiac activity

• A. Bipolar
• B. Tripolar
• C. Intracardiac
• D. Unipolar

Answer: (D)

Unipolar electrograms are recorded with one electrode referenced to a distant indifferent electrode, so the potential at the recording site includes contributions from the entire heart. Because the reference is far away, signals from distant regions are not canceled, making the waveform a summation of all cardiac activity occurring at that moment. This gives a broader view of the heart’s electrical activity, capturing both local events and far-field signals. In contrast, bipolar recordings use two nearby electrodes and subtract one from the other, which emphasizes local activation and reduces far-field influence. Tripolar configurations mix signals for noise rejection but don’t primarily define the global summation seen in a unipolar recording. Intracardiac simply describes the location of the recording, not the signal’s composition.