my brother yesterday had a breathlessness, dizziness ,blackouts,with no symptom of pain in chest or abdomen, nofever ,he was not able to drink , fr which he went to doctor.his pulse was 166 beats /min .HR=122 breaths/min. blood pressure was normal. temp was normal. he was kept on oxygen mask fr hour an hour.and later given pantosecd tablet and discharged. I want to know what are the probable diagnosis in this case.(I m a 3rd year medical student).