An implantable system is provided that includes: a cell repopulation source comprising genetic material, undifferentiated and/or differentiated contractile cells, or a combination thereof capable of forming new contractile tissue in and/or near an infarct zone of a patient's myocardium; and an electrical stimulation device for electrically stimulating the new contractile tissue in and/or near the infarct zone of the patient's myocardium or otherwise damaged or diseased myocardial tissue.