How does epinephrine lower defibrillation threshold?

Epinephrine lowers the defibrillation threshold by enhancing myocardial contractility and promoting vasoconstriction, which improves coronary and cerebral perfusion during cardiac arrest. It increases the release of norepinephrine and enhances the excitability of cardiac tissues, making them more responsive to electrical shocks. This combined effect helps to stabilize the heart's electrical activity, increasing the likelihood of successful defibrillation. Additionally, epinephrine's ability to increase systemic vascular resistance aids in maintaining circulation during resuscitation efforts.