A biologic agent delivery system provides for delivery of a biologic agent
to a stimulation site to which electrical stimulation pulses are to be
delivered from an electrical stimulation device. Examples of the
electrical stimulation device include cardiac pacemakers and neural
stimulators. The biologic agent modifies tissue property to lower the
stimulation threshold of the stimulation site. The genetic modification
of the tissue property improves efficacy and/or energy efficiency of an
electrical stimulation therapy.