C Fran Mason,   Thanks for your interesting question.    You mentioned that you have passed out in the past in response to pain, but that this episode was different.  When a person passes out, this is usually a vaso-vagal reaction.  Pain, seeing something unpleasant (like blood), extreme fear, etc causes a cascade of events initiated by the vagus nerve and the sympathetic nervous system.  The two main changes to occur are a drop in blood pressure and slowing of the heart beat.  For this reason, if you see someone who is passing out, lay them down flat as soon as possible, to help restore blood flow to the brain.  If a person's natural pacemaker is abnormal, its response to a vaso-vagal reaction might be exaggerated, and the heart may stop for several seconds.  We sometimes see this response when we test patients who have passed out.  We apply pressure to the carotid artery area where there is a bundle of nerves called the carotid sinus.  This pressure stimulates the vagus nerve.  While doctors perform this maneuver, we watch the cardiac monitor and if there is a long pause, it indicates that the natural pacemaker is not functioning appropriately.    Before considering a pacemaker, we look for other factors that may have influenced the situation, such as medications, especially beta blockers, which can also slow the heart and change the pacemaker's response in these situations.  If an abnormally functioning pacemaker is diagnosed, then a pacemaker can be placed which is set for a certain rate, depending on the patient.  If not needed, the pacemaker is in standby mode, until the pulse falls below a pre-programmed rate.  Some pacemakers even respond to the body's need for higher pulse rate, such as exercise.  The procedure of placing the pacemaker is considered minor, and is done under local anesthesia with the patient awake.   Unfortunately you have heart disease, as well as a strong family history of heart disease.  This make the likelihood of having a disease natural pacemaker greater.  This is called Sick Sinus Syndrome.   It sounds like your doctor is on top of the situation.   Best wishes.   Martin Cane, M.D.