The medical term for “Faint” is “Syncope”. It occurs when blood flow to the entire brain is suddenly reduced. Most causes are obviously temporary, because if not, death ensues. In many cases, the faint cures itself, because falling from standing to lying allows more blood to arrive.
General Causes of Syncope
- Vasovagal Syncope
- Orthostatic Syncope
- Cardiac Arrhythmias
- Other Heart Diseases
- Neck Movement causing Syncope
Vasovagal Syncope: The Vagus Nerve runs from the brain down to the bowel and bladder, able to affect all the organs in between. In terms of the heart, Vagal action slows the heart rate. The prefix “vaso-“ means blood vessels, so when the heart suddenly slows, blood flow to the brain drops.
The Vagus Nerve can be stimulated in various contexts:
- Emotional trigger: fear, pain, anxiety, laughter, disgust (sight of blood, etc.)
- Reflex actions: cough, urination, defecation, swallowing (esp. cold liquid)
- Straining: weight-lifting, horn-playing, etc.
- Situations: crowded room, prolonged standing, heat, etc.
- Digesting a heavy meal
If we think the patient had Vasovagal Syncope, we don’t do any tests. Diagnosis is made by the history alone. We just need to be comfortable that the person did not have Cardiac Syncope (see below). Treatment is simple reassurance.
Orthostatic Syncope: This means that blood pressure drops upon standing. It may be provoked by:
- Loss of blood volume (hemorrhage, dehydration)
- Medications / Alcohol
- Blood pressure instability from certain diseases (Diabetes, Parkinson’s etc.)
We don’t need any tests if fainting occurred in the past, and the patient feels fine now. If symptoms of any sort persist, we measure Postural Vital Signs to confirm our suspicion (check heart rate and blood pressure lying down, and then upon standing; see link).
Treatment is patient education: if lying down, sit for a while before standing up; stand with caution, to be able to sit again if necessary.
Cardiac Arrhythmias: Here the heart doesn’t pump efficiently due to an abnormal heart rhythm. See the link for detailed descriptions of the various kinds. In general, Arrhythmias may be:
- Not so dangerous: Supraventricular Tachycardia (fainting is rare, but may occur at the very onset)
- Life-Threatening: heart block, bradycardia, ventricular tachycardia, long QT
Heart Diseases (other): We especially suspect these if Fainting occurs during exertion. There may be other symptoms as well, such as chest pain, shortness of breath, nausea, or burst of cold sweat. These diseases may be either:
- Coronary Artery Disease (i.e. Heart Attack, or less serious Angina)
- Outflow obstruction (interference with blood flow as it’s pumped from the heart) —Hypertrophic Cardiomyopathy, Tumors, Aortic Stenosis
Neck Movement causing Syncope may be from either:
- Pressure on Vagus Nerve running next to the carotid pulse (slows the heart rate)
- Unusual anatomy that occludes the carotid artery (causing TIA)
This is pretty rare. Diagnosis is made by history, then by various imaging (x-rays, etc.) to seek anatomical abnormalities.