Syncope Diagnosis
There are three main ways to identify the causes of syncope: the medical history, the physical examination, and cardiac testing. A medical history and physical examination are recommended for anyone who has had syncope. Some people will also require cardiac testing.
Medical history — Gathering as much information as possible about events that occurred before, during, and after a syncopal episode can be helpful in determining the possible cause of syncope.
As an example, vasovagal syncope is suspected in a person who has warning signs of nausea or sweating. In contrast, a sudden loss of consciousness with no warning is more likely to be due to a heart rhythm problem. A person who has syncope during exertion is more likely to have an obstruction to blood flow (aortic stenosis or hypertrophic cardiomyopathy) or ventricular tachycardia as a cause.
Information about current medications and pre-existing medical conditions such as diabetes, heart disease, or psychiatric illness can help pinpoint the cause of syncope. If the person has abnormal body movements while unconscious and requires a long time to recover consciousness, the person may have had a seizure and not a true syncopal episode.
Physical examination — The clinician will measure your heart rate and blood pressure to help determine if a rhythm disturbance or low blood pressure caused the syncope. You may be asked to sit or stand while the blood pressure is measured to test for orthostatic hypotension. The clinician will listen to your heart for abnormal sounds that can be present in conditions such as aortic stenosis. You may have a test for blood in the stool to evaluate for blood loss, which could result in syncopal episodes.
If the cause of the syncope is not readily apparent, the clinician may perform special maneuvers to test your response. As an example, you may be asked to bear down as if having a bowel movement; abnormal heart sounds that occur in response to this maneuver can point to hypertrophic cardiomyopathy. The clinician may firmly massage your carotid artery (located in the neck) while your heart rate is closely monitored with an electrocardiogram (ECG or EKG). The heart’s response to this maneuver can give clues to a possible diagnosis.
Testing — A number of medical tests are available to help determine the cause of the syncope.
Electrocardiogram — Anyone who have had an episode of syncope should have an ECG. An ECG can be performed in a clinician’s office and takes only a few minutes. Sticky pads are placed on your chest, abdomen, arm, and leg, and are connected to a recording device with long, thin cables. This is not painful and there is no risk of electric shock with an ECG.
The ECG provides a picture of the electrical activity passing through the heart muscle. A normal ECG does not necessarily mean that syncope is not caused by a heart rhythm problem. Heart rhythm problems are often brief, come and go, and may not be present at the moment when the ECG is performed.
Rhythm monitoring — Heart rhythm monitoring may be recommended to diagnose rhythm problems that come and go and have not been detected with a routine ECG. This monitoring may be done at home or in the hospital.
●Holter monitor – You may be asked to wear a monitoring device, called a Holter monitor, for 24 or 48 hours while performing normal daily activities at home. The device is connected to several long thin cables that are attached to your chest with sticky pads (similar to an ECG). The cables connect to a small, portable machine that can be attached to a belt or strap that is carried over the shoulder (figure 3).
However, this type of monitoring has limited use and provides a diagnosis in only about 2 to 3 percent of people with syncope. If you do not experience a syncopal episode while wearing the Holter monitor, the test may need to be repeated, or an alternate form of long-term monitoring may be recommended.
●Event recorder – An event recorder may be recommended to capture rhythm problems associated with a syncopal episode. The advantages of an event recorder compared with a Holter monitor are its small size and the ability to monitor for abnormal rhythms for longer periods of time (usually one to two months).
Some devices require you to activate the recorder when you feel symptoms of a syncopal episode. However, if you lose consciousness and another person is not available to assist with the recording, the opportunity to “capture” the event on the monitor may be lost (figure 4).
●Intermittent loop recorders – Intermittent loop recorders were developed to capture rhythm problems that occur before the device is activated. When you activate the monitoring device after regaining consciousness, the ECG recordings from the previous few minutes are retrieved and stored for analysis at a later time.
An implantable loop recorder (ILR) provides a way to monitor rhythms over an extended period of time (eg, 18 to 24 months). The ILR is implanted under the skin on the upper left chest area. It stores events automatically according to programmed criteria, or can be activated by the patient. The ILR may be most useful if your symptoms are infrequent and an arrhythmia is suspected, but other forms of testing are negative or inconclusive.
Echocardiogram — An echocardiogram is useful for identifying underlying structural heart disease such as hypertrophic cardiomyopathy or significant aortic stenosis. These findings alone do not conclusively establish the specific cause for syncope.
An echocardiogram uses ultrasound (sound waves) to obtain detailed pictures of your heart as it beats. A technician presses a transducer (wand) against your chest and abdomen. The transducer is attached to a recording device and monitor. You are awake during the procedure. An echocardiogram does not use radiation.
Upright tilt table test — This test is often done in healthy patients who have syncope. You lie on a flat table and are tilted at various angles while your heart rate and blood pressure are monitored closely (figure 5). Your response to the change in position can sometimes give clues about the cause of syncope.
Electrophysiology study — An electrophysiology study (EPS) may be performed if you have heart disease or if a rhythm problem is suspected.
Most people undergo EPS in a hospital setting. You will be given a sedative before the procedure but may be awake during testing. The physician uses a local anesthetic to numb a small area over a blood vessel, usually in the groin, and then threads small wires through the blood vessels into the heart using x-ray (fluoroscopic) guidance. Once in the heart, precise measurements of the heart’s electrical function can be obtained.
Exercise testing — In some people, especially those with a history of syncope during exertion, an exercise test is useful. Your blood pressure, heart rate, and rhythm are monitored while exercising on a treadmill or bicycle.
Electroencephalogram — An electroencephalogram (EEG) is used to diagnose seizures, but may be part of the evaluation of unexplained “collapse” events. It involves the measurement of electrical activity in the brain. It can be performed in a provider’s office or in a hospital, and generally takes approximately one hour. Multiple electrodes (small, flat metal discs) will be attached to your head and face with a sticky paste. The electrodes are connected to a recording device with long, thin wires. You must lie still and avoid speaking during the test.
An EEG is frequently obtained in people with syncope, but is rarely useful. It can be helpful if you have syncope and seizure-like activity.
Syncope Treatment
Treatment of syncope is based upon the underlying cause. The goal of treatment is to prevent recurrences or more serious problems.
Vasovagal syncope treatment — Vasovagal syncope can usually be treated by learning to take precautions to avoid potential triggers and minimize the potential risk of harm. For example, if you faint while blood is being drawn, you may be instructed to lie down during the procedure. If you have a feeling that you will pass out during any activity, you should immediately lie down and elevate your legs.
Counter-pressure maneuvers — Counter-pressure maneuvers such as tensing your arms with clenched fists, leg pumping, and leg-crossing may stop a vasovagal syncopal episode, or at least delay it long enough that you can lie down with the feet elevated. Such maneuvers include:
●Leg crossing while tensing the leg, abdominal, and buttock muscles.
●Hand gripping, which involves gripping a rubber ball or similar object as hard as possible.
●Arm tensing, which involves gripping one hand with the other while simultaneously moving both arms away from the body.
Medications — People with a heart rhythm problem may be started on medication to control the rhythm.
People with orthostatic hypotension may benefit from increasing the amount of blood fluid volume. Fludrocortisone (Florinef) is one medicine that is used to increase blood volume. Midodrine is a medication that constricts blood vessels that may be used in combination with fludrocortisone.
Pacemakers — A pacemaker is a small device that is implanted under your skin. Wires from the device are threaded to the heart where they emit impulses that help regulate the heartbeat. Pacemakers are often recommended if you have syncope caused by sinus bradycardia, carotid sinus hypersensitivity, or heart block. Some new pacemakers are directly implanted within the heart, but these are still only infrequently used.
Implantable cardioverter-defibrillator — In some people with serious, life-threatening ventricular arrhythmias (such as ventricular tachycardia) that cause syncope, a device called an implantable cardioverter-defibrillator (ICD) is used. The device is surgically implanted under the skin in your chest, similar to a pacemaker. It can sense when a life-threatening ventricular arrhythmia is occurring and administer an electric shock to correct the problem and potentially prevent the person from dying.
Orthostatic training — In people with orthostatic hypotension and certain types of vasovagal syncope, orthostatic training may be useful to prevent syncope. Techniques are designed to decrease pooling of blood in the extremities, which can allow the blood pressure to drop when you stand. Methods to decrease this problem include the following:
●Use of elastic compression stockings, which are worn on the feet and lower legs
●Contraction of the leg muscles before and while standing
●Rising to stand slowly and in stages
Safety Issues
Passing out while driving or other activities can potentially harm both the patient and those around him/her. As a result, driving restrictions are sometimes recommended for certain people with syncope. This generally includes people who have a history of syncope that occurs without warning or known cause. Driving restrictions are governed by state or local laws.
Source: UpToDate
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