How can an endoscopy gastroscopy cause a heart attack or stroke??? just read it on the internet that endoscopy can cause heart attak/stroke. how?why?

Heart attack: There is a certain amount of stress with every medical procedure. Stress is one of the triggers for heart attack. Some people are more susceptible than others to the stressors.

Rare complication: Whenever things are put down the throat (eg. scopes or fingers) which cause reflex gagging then, in hypersensitive people the Vagus nerve can cause strong cardiac stimulation resulting in standstill or severe arrhythmia to be triggered in hypersensitive individuals. Proper anesthesia of the patient usually avoids this from happening but despite this it's still a rare complication that can happen.