Why is there a reduction in impedance during lesion formation?

During lesion formation in the context of ablation procedures, a reduction in impedance is primarily attributed to the physiological changes that occur in the tissue rather than a singular event, such as the explosion of cell membranes.

As tissue is heated during ablation, the cellular structure is disrupted, leading to the breakdown of cell membranes and the release of intracellular fluids. This process increases the conductivity of the tissue because the normally insulating membrane barriers are compromised, allowing electricity to flow more easily. The increase in ionic mobility and the alteration of tissue architecture result in lower impedance as the ablation progresses. Therefore, while the notion of cell membranes exploding captures part of the mechanism, it is the overall process of cellular breakdown and consequent changes in tissue properties that lead to reduced impedance.

The other options do not typically explain the phenomenon accurately, as they either suggest an increase in resistance or do not directly relate to the actual changes occurring during the thermal ablation process.