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Evaluating The Cause Of Syncope

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Updated April 11, 2012

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

If you have had an episode of syncope (a transient loss of consciousness also referred to as fainting), it is important for you and your doctor to figure out what caused the episode. There are many potential causes of syncope, and unless your doctor approaches the diagnosis in a systematic way, things can get confusing in a hurry. This article discusses a straightforward and systematic approach to the diagnosis of syncope.

First Things First

In evaluating the cause of syncope, your doctor has an immediate question to answer: Does the syncope in your case suggest an increased risk of sudden death? Fortunately, arriving at an answer to this question is usually pretty straightforward, and also fortunately, in the large majority of cases the answer to this question is "no." Still, it is critical to address this question right away. Since life-threatening syncope is almost always cardiac in origin, this means your doctor needs to determine whether you have, or are likely to have, a significant cardiac condition. If your doctor decides that your syncope may have been due to a cardiac condition, an immediate evaluation is necessary -- and it may be necessary to hospitalize you until a life-threatening cause is ruled out, or you are adequately treated.

If (as is much more often the case) your doctor does not find any sign of a life-threatening condition, then he or she can perform a less hurried evaluation to find the cause of your syncope, and hospitalization is only rarely needed.

A Two-Phased Approach To Evaluating Syncope

Phase One - Medical History and Physician Examination

This, far and away, is the most important step in diagnosing the cause of syncope. The history and physical examination give vital clues in diagnosing nearly all causes of syncope. However, while all doctors are taught this, many, unfortunately, never seem to learn it.

This is why you need to be aware of this fact: In the large majority of cases, the doctor should have an excellent idea as to the cause of syncope after talking to you and examining you. So if your doctor fails to do a thorough medical history (which is described below), and performs only a cursory physical examination, and then has no idea as to what caused your syncope, then you should consider seeing another doctor.

Taking a careful medical history must include getting the details about any possible cardiac history you may have, including: a) all information pertaining to any prior history of heart disease; b) if you have no history of heart disease, then evaluating your risk factors for heart disease; and c) asking you about any family history you may have of heart disease, especially any family history of sudden death. In addition, the doctor should ask you for the details of each and every one of your syncopal episodes -- all the way back to childhood, if necessary -- including information regarding when each one occurred, what you were doing at the time, whether there was any warning, how long it lasted, whether you regained consciousness as soon as you fell down, and whether you have discovered a way to abort the episodes if you feel one coming on.

The physical examination should include thorough neurological and cardiac exams. Your doctor should take your blood pressure in each arm, and should measure your blood pressure and pulse while you are lying down, and again when you are standing.

By the end of the history and physical, your doctor ought to have an excellent idea as to what is causing your syncope. In particular, at the very least your doctor should know how likely it is that you have a cardiac problem causing the syncope -- in which case, sudden death is a concern. If cardiac disease is not suspected, then generally your doctor will need to order no more than one or two directed tests to confirm her suspicions. She should be able to tell you what she thinks is the problem, and should even be giving you some idea of what the treatment will likely entail.

On the other hand, if your doctor has finished up with you and is standing there, shaking her head, ordering a whole battery of tests and procedures, shotgun-like, that address numerous organ systems, then you are both in for a very hard time. This would be the time to consider seeking a second opinion.

Phase Two - Directed Testing

After the history and physical exam:

  • If your doctor suspects a cardiac cause for your syncope, a non-invasive cardiac workup should be done immediately. In most cases, this work-up will consist of an echocardiogram, and in some cases a stress test. If some form of obstructive heart disease is found (such as aortic stenosis), then treatment to relieve the obstruction should be planned as soon as possible. If this initial evaluation points to a cardiac arrhythmia as the cause of your syncope, you may need electrophysiologic testing. In this case, it is likely that you will need to remain on a hospital monitor until you receive definitive therapy.

    Read about the cardiac causes of syncope.

  • If your doctor suspects a neurological cause, then she will probably order a CT scan of the brain or electroencephalogram (EEG), or in some cases, angiography (a dye study to visualize the arteries to the brain) to confirm the diagnosis. Syncope due to neurological disorders, however, are relatively uncommon.

    Read about the neurological causes of syncope.

  • If your doctor has diagnosed or strongly suspects vasomotor syncope (that is, orthostatic hypotension, POTS, or vasovagal syncope), usually no further testing is necessary. In some cases, a tilt table study may be useful in confirming the diagnosis. But generally, once this type of syncope is identified, your doctor can immediately move toward instituting therapy. The majority of people who have syncope turn out to have vasovagal syncope.

    Read about vasomotor syncope.

  • If your doctor -- despite taking a careful medical history and performing a thorough physical examination -- still has no good presumptive explanation for your syncope, it is usually a good idea to perform non-invasive cardiac testing to rule out subtle cardiac disease. This testing generally will consist of an echocardiogram, often ambulatory monitoring (where you wear a cardiac monitor at home for several days or weeks), and possibly stress testing. A tilt table study may also be useful. If syncope remains undiagnosed after these studies, electrophysiologic testing may be considered.

Summary

Using this general two-phase approach, it is probable that your doctor will be able to diagnose the cause of your syncope quickly and accurately, and will be able to initiate appropriate therapy in short order.

Sources:

Strickberger SA, Benson DW, Biaggioni I, et al. AHA/ACCF Scientific Statement on the evaluation of syncope: from the American Heart Association Councils on Clinical Cardiology, Cardiovascular Nursing, Cardiovascular Disease in the Young, and Stroke, and the Quality of Care and Outcomes Research Interdisciplinary Working Group; and the American College of Cardiology Foundation: in collaboration with the Heart Rhythm Society: endorsed by the American Autonomic Society. Circulation 2006; 113:316.

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