Cardiovascular power source for automatic implantable cardioverter defibrillators

A method of measuring the ventricular function of a heart, comprising;

• providing an implant comprising:
• a power consuming means for responding to a physiological requirement of the body;
• a power source comprising a flexible piezoelectric assembly configured to generate an electrical current when flexed by the tissue of the body, wherein the piezoelectric assembly comprises an upper electrode, an opposed lower electrode, and a plurality of nanowires arranged in an array and forming a nanowire layer, wherein each of the plurality of nanowires is generally oriented parallel to a common array axis, and wherein the plurality of nanowires are operatively coupled to the upper electrode layer and the opposed lower electrode layer;
• and
• a power storage device electrically coupled to the power source and to the power consuming means;
• measuring the current generated by the power source;
• and
• calculating the strength of the heart's contraction from the measured current generated by power source.