A method for treating a patient's heart is provided. The method includes providing a light source which emits light having an initial power density. The method further includes positioning the light source relative to the patient's heart with intervening tissue of the patient between the light source and the patient's heart. The method further includes directing light onto cardiac tissue of the patient's heart from the light source through the intervening tissue without damaging the intervening tissue. The cardiac tissue is irradiated by an efficacious power density of light for an efficacious period of time.
