Hi there -
I hope by now you've seen your doctor. An EKG at the very least is in order. While you may have no history of coronary artery disease or even structural heart disease, you may have an electrical problem in your heart that's causing these episodes, and this could be something simple or something more serious, but in either case the fainting creates a major problem on its own, even if it's essentially benign, since falling down can cause serious injury.
You may be having simple vasovagal or neurocardiogenic syncope (faint) or you may have a more serious electrical problem. Since it seems your heart slows prior to the syncopal episodes, you could have a prolonged Q-T interval (potentially very serious, but at least manageable if diagnosed) or an intermittent form of heart block. These can be essential or acquired. They can be acquired due to use of certain medications, in particular, or other conditions. The less serious issues can be managed as well, but anything that causes a loss of consciousness is a potentially dangerous one anyway, not only from falling but also because it can happen when one is driving.
A cardiological workup is the first order of business. If that turns up nothing then a tilt table test, usually also performed by a cardiologist, as well as an echocardiogram, may need to be done. If none of this turns up anything, then a neurological study should be performed, but from the description provided by you it sounds like a heart and/or circulatory problem.
I hope this is helpful to you. Please keep us updated as to what you learn from your visit with the doctor and any subsequent workups. Best of luck to you.
John Kenyon, EMT, CCT
Non-invasive cardiology tech, Emergency and Critical Care technician, Critical Incident Stress Mgmt. specialist