Abstract: A defibrillation insulating device prevents current from directly shunting through the blood pool from the right ventricular defibrillation electrode to a superior vena cava electrode and vice versa. This forces current to flow through the heart muscle, thus increasing the current density throughout the heart, to depolarize the majority of the cardiac tissue with a minimum of energy.

Abstract: A lead having a defibrillation electrode that is deployed for defibrillation using artificial muscle. In an undeployed position, the defibrillation electrode is small in diameter so as to be easily implanted pervenously and nonobstructive to cardiac contraction and blood flow. In a deployed position the defibrillation electrode is larger in diameter for defibrillation shock delivery. Thus, the electrode forces an increased amount of current to flow through the heart muscle during shock delivery to depolarize the majority of the cardiac tissue with a minimum of energy, while not obstructing blood flow at other times when not used for energy delivery.