The heart is supplied by oxygen rich blood through three coronary arteries (vessels).
Your father's coronary angiogram shows that all three vessels are diseased (tVCAD= triple vessel Coronary Artery Disease).
This means that in all three vessels there is evidence of blockages.
Blockages can be mild or severe or even complete, so the fact that your father has tVCAD dooes not say much about the severity of the disease.
That he does not feel well could mean that it is serious though.
The coronary angiogram report must include much more about the severity of the disease. What did his doctor say?