In ventricular fibrillation, how may the EEG waveform evolve before potentially becoming asystole?

• A. The waveforms may progress from coarse to fine and eventually disappear.
• B. QRS complexes become more pronounced.
• C. P waves become dominant and QRS disappear.
• D. Rhythm becomes regular with consistent rate.

Answer: (A)

When the brain is not being perfused during ventricular fibrillation, its electrical activity changes as neurons fail. The EEG shows a progression as oxygen and glucose supply drop: you first may see coarse, high-amplitude slow waves, reflecting partial, disorganized neuronal activity. As ischemia continues and neurons fail further, the activity becomes finer—lower amplitude and faster, less synchronized patterns. If perfusion does not return, this activity eventually disappears, leading to an isoelectric (flat) EEG. This sequence—coarse waves, then finer activity, then disappearance—best matches the described evolution.

The other options describe ECG features (QRS complexes or P waves) or a regular rhythm, which do not describe EEG changes during cerebral ischemia in cardiac arrest.