1. Mechanism of Action: When the heart enters a state of fibrillation, the cardiac muscle fibers contract in a chaotic, uncoordinated manner, failing to pump blood. A defibrillator delivers a controlled, high-energy dose of electric current (an electric shock) to the heart.
2. Restoring Rhythm: This sudden electrical surge depolarizes a large part of the heart muscle simultaneously. This momentarily stops the chaotic electrical activity, allowing the heart's natural pacemaker (the SA node) to re-establish a
normal, coordinated heart rhythm.
3. Role in the Clinical Setting: Defibrillation is distinct from pacing. While a pacemaker maintains a rhythm, a defibrillator is used to "reset" a dangerous rhythm that has already occurred. It is not used for measurement (like blood pressure or temperature) or imaging (like X-ray or MRI).