What is cardio thoracic vascular surgery my son 's stents are blocked, he has cardiomyopathy and needs a defibrillator?

Heart and arteries. This is specialty dealing with heart blood vessels and chest and lungs.
See below. This sounds like cardiac bypass surgery. If the stents are blocked then the heart is not getting enough blood flow. This will continue to cause problems. Talk to your physician and find out exactly what they mean.
Cardiac Surgeon. A cardio-thoracic surgeon treats disorder son both the heart and the lungs. Some restrict their practice to either the heart or the lungs. It sounds like your son needs a cardiologist or cardiac surgeon.