Which specialty of doctor reads an angiogram?

Several. The doctor who does the angiogram will interpret the results. Angiograms of the heart vessels done and read by interventional cardiologists. Angiograms of the brain read by interventional radiologists or neurologist. Angiograms of arms legs neck often by interventional radiologists or vascular surgeons. Vessels of the abdomen and pelvis usually by interventional radiologists.
Cardiology/Radiology. If it is a coronary angiogram, then the cardiologist who performed the angiogram (catheterization) reads the angiogram. If it is an angiogram of the leg, arm, or aorta, it can be read by a vascular surgeon. Generally, a brain angiogram is read by an interventional or neuro radiologist. If it is an angiogram of another part of the body, usually it is an interventional radiologist.