Thanks for writing to Health Care Magic, I am Dr Asad Riaz, I have closely read your question and I understand your concerns, I will hereby guide you regarding your health related problem.
As such a blood pressure reading of 100/59 mmHg or a pulse of 61 doesnot cause passing out or
syncope. But the medicines you are on sometimes cause a postural drop in blood pressure, which means that the blood pressure instead of rising (as it does on standing) falls causing the patient to feel dizzy and sometimes pass out.
Dehydration also causes the same.
If there is a history of heart problems in the past, any episodic disturbance in heart rhythm can also cause one to pass out
For this I would advise you to get your postural Blood pressure checked, take
Lisinopril at night and get an EKG (preferably 24 hours Holter) done to look into the cause
I hope this answered your question, if you have more feel free to ask.
Regards.
Dr.Asad Riaz.
General and Family Physician.