Which electrogram type includes both local and far-field signals and represents the summation of all cardiac activity?

Which electrogram type includes both local and far-field signals and represents the summation of all cardiac activity?

• A. Unipolar
• B. Bipolar
• C. Orthogonal
• D. Multipolar

Answer: (A)

Unipolar electrograms reflect the global electrical field of the heart. With a distant reference electrode, the recorded signal at the sensing site includes both nearby (local) activation and signals coming from other regions (far-field). This combination yields a waveform that represents the summation of all cardiac activity as seen from that location, giving a broader view of activation across the heart. Bipolar recordings use two closely spaced electrodes and subtract the signals, which emphasizes local activation while greatly reducing far-field content, so they don’t show the global summation. Orthogonal recordings capture activity along three perpendicular axes for directional information, not a single summated signal. Multipolar approaches sample from many sites to map activity, producing multiple localized signals rather than one global summation.

Unipolar electrograms reflect the global electrical field of the heart. With a distant reference electrode, the recorded signal at the sensing site includes both nearby (local) activation and signals coming from other regions (far-field). This combination yields a waveform that represents the summation of all cardiac activity as seen from that location, giving a broader view of activation across the heart.

Bipolar recordings use two closely spaced electrodes and subtract the signals, which emphasizes local activation while greatly reducing far-field content, so they don’t show the global summation. Orthogonal recordings capture activity along three perpendicular axes for directional information, not a single summated signal. Multipolar approaches sample from many sites to map activity, producing multiple localized signals rather than one global summation.