What can cause sudden blackout in a diabetic patient?

The CT scan shows no significant lesion in the brain and no focal hemorrhagic bleeding event, which is one of the main causes in many cases. Heart diseases can also cause unconsciousness. In such cases, we monitor indoor patients on Holter monitor for any kind of rhythmic change in heart beat and to see if there is any atrial or ventricular fibrillation. Your father did not have a positive sign there. His heart rhythms are normal. Sometimes there is an imbalance in the serum electrolytes and fluid; electrolyte imbalance may lead to unconsciousness and syncope. But your father is fine with that, too. Your father's angiography for single artery occlusive disease went eventless, and normal flow to the heart was restored with stent deployment. My final impression is patients with diabetes also sometimes get unconscious due to the low glucose levels in the blood and due to low supply of glucose to the tissues. For example as in case of type II diabetes, they get low insulin levels that cause them to get problems with taking glucose into the tissues from the blood. No need to worry as this may be anything that is not so obvious and so minor and a single event that cannot be revealed on investigations. In such situations, usually, there is no harm to the patient. Patients after angiography may sometimes get such an issue due to manipulation of the heart in angiography. But, this is not a major issue of medical concern. There is no problem with his heart and the stent is not displaced from the site which may be a source of tension for the patient. Your father is totally alright. I have scanned and observed all the reports deeply, and he is fine in every respect.