An EKG even a treadmill cannot rule out cardiac problems. If he has any family or personal history of Cardiac problems especially if the pain is severe and consistent after exercise and is squeezing or pressure on the chest or radiating to the shoulders and down the arm it should be investigated further. Other causes PD can be dystonia. or it may be related to costochodritis an irritation of the joint between the sternum and the ribs which is made worse by putting a little pressure on the joint. Parkinson's meds to my knowledge usually do not cause chest pain. I would check with hi doctor (neurologist) to rule out any neuro cause(unlikely) and especially if this is new or severe I would push the Primary Care Physician for an explanation.