Vasovagal syncope

What is Syncope?

Syncope is the medical term used to describe loss of consciousness, passing out or fainting. Several medical conditions could result in syncope such as seizure disorders, heart rhythm abnormalities such as slow or fast rhythms and problems related to heart valve. You are seeing a cardiologist as your doctors are concerned about syncope relating to heart abnormalities. In most cases, syncope is due to a condition called Vasovagal syncope (VVS), also known as neurocardiogenic syncope (NCS). Other names used to refer to VVS include vasodepressor syncope or common faint. It commonly occurs in young fit and well people and more common in women.

What is vasovagal syncope (VVS)?

VVS, also known as neurocardiogenic syncope, occurs due to your autonomic (involuntary) nervous system sending out exaggerated signals that results in low blood pressure and heart rate which results in low blood flow to your brain causing syncope. It is believed to be related to the “fight-or-flight” response that we all have in response to a stressful situation. When there is a certain stressful stimulus, but not always perceived as stressful, your body can either respond by increasing your blood pressure, heart rate and get you ready to move or respond – the ‘fight’ response. Alternatively, your autonomic nervous system can respond with a ‘vagal’ response that results in low blood pressure and slower heart rate – the ‘flight / avoid’ response. You can think of it like ‘playing dead’ response many animals use as anti-predatory behaviour. The low blood pressure and slower heart rate can cause symptoms of feeling dizzy, light-headedness and result in syncope. Other common associated symptoms include nausea, feeling clammy, hot and sweaty, abdominal discomfort, blurry vision, muffled hearing and perception of curtain coming down / vision going dark. These symptoms are warning signs before the episode escalates to syncope. An episode of vasovagal exacerbation / syncope can range from mild to severe. These warning signs provide an opportunity to act before it becomes severe. Hence, lying down when you have those warning symptoms prevents exacerbation.

The usual mechanism of VVS is thought to be related to inappropriate or exaggerated relaxation of blood vessels and low heart rate, resulting in low blood pressure at a time when the body needs more blood pressure and heart rate. This is driven by the vagus nerve – vasovagal. ‘Vaso’ refers to the blood vessel or vascular component. As the blood vessels relax and blood pools, this information is relayed to the brain through the autonomic nervous system. The usual response is for the brain to activate the sympathetic nervous system to increase heart rate, vascular tone and thereby blood pressure. It is not known how and why this response if withheld resulting in worsening spiral that results in lower blood pressure and or heart rate resulting in syncope.

Syncope is normal body response telling you get your head down lower to the ground so that blood can return to your brain. Trying to stand up or walk when you are having an episode will exacerbate your symptoms and often worsen the situation. People often feel washed out and exhausted after an episode. This feeling may last minutes, hours or in some cases, rest of the day.

How do I find out if I have VVS?

Although VVS can be diagnosed based on your symptoms, description, and situations, it is still important to exclude other serious causes of syncope. You will need some basic tests such as 12-lead ECG, 24-hour Holter monitor, 24-hour blood pressure monitor and usually an echocardiogram. Other investigations people may consider include an electroencephalogram (EEG) if seizure is suspected. Occasionally a tilt table test may be required to make the diagnosis, but it is becoming increasing uncommon.

What can I do to prevent VVS?

In most cases, non-pharmacologic (not using medications) treatment is the mainstay of treatment for people with VVS. Three most important aspects of managing VVS include hydration, preventing exacerbation, symptom recognition, and special manoeuvres.

Hydration: Staying well hydrated is the most effective way to prevent VVS. Preventing dehydration is important. Alcohol and caffeinated beverages contribute to dehydration. Hence limiting or avoiding them is a good first step. Drinking enough water until your urine is clear (not yellow) is generally a good indicator that you are drinking adequate amounts of water. Generally, you will need to drink 2 litres of water a day. If your blood pressure is low despite adequate hydration, additional salt intake maybe required. Salt acts like magnet to water keeping it within your blood vessels. It is important to note that excess salt can be harmful if you have normal or high blood pressure to start with. Only those with low blood pressure might benefit from increased salt intake. Having additional fluid intake (300-500mls) prior to sustained exercise can be helpful.

Preventing exacerbation: Certain situations are known to exacerbate VVS. Avoiding them where possible or being adequately prepared for those situations is an important strategy in managing VVS. Sleep deprivation appears to be important risk factor. Other common situations include standing up for a prolonged period, working in a hot / warm / stuffy environment, pausing after exercising, having a painful stimulus such as having a needle or blood taken, sight of blood and hearing bad news. If you cannot avoid these situations, being aware that these situations exacerbate VVS is important to recognise and prepare for the eventuality.

Symptom recognition: One of the most important ways to control or avoid a full syncope is to be aware of early or warning symptoms. These include feeling dizzy, light-headed, feeling squeamish, nausea, feeling clammy, hot, and sweaty, abdominal discomfort, blurry vision, muffled hearing, and perception of curtain coming down / vision going dark. People observing you may report you look pale, gray or colour draining out of your face. It is important to recognize these symptoms to institute special manoeuvres.

Special manoeuvres: As soon as you recognise symptoms of VVS, you should institute these manoeuvres. Blood is pooling in the periphery that triggers VVS. The aim of these manoeuvres is to return blood to your brain. The best manoeuvre is to lie down on your back. Raising legs up or keeping your knees bent improves blood returning to your brain. Other options include a low squat which squeezes your peripheral blood vessels and prevents further pooling. If lying down or squatting is not possible, crossing your legs and squeezing your leg muscles and tensing your abdominal muscles can help return blood to your brain. It may also help to use the last manoeuvre as a preventative measure when standing up for too long or working in a hot environment before you have an episode.

It is important to note that trying to stand up or walk when you are having an episode will exacerbate your symptoms and often worsen the situation. Lie down and avoid standing up when you are having a vasovagal episode.

Are there any medical treatments for VVS?

Medical treatments are not usually required for most people and not recommended as initial strategy. There are several medications which may help VVS but do not cure your condition. Medications are only considered in severe cases and when all the above measures fail. There are specialists specialising in management of autonomic dysfunction who might be able to help you further.

What are other associated conditions?

Other autonomic dysfunction related cardiac conditions include inappropriate sinus tachycardia (IST), and postural orthostatic tachycardia syndrome (POTS). Simple measures such as lifestyle modification, adequate hydration and optimal blood pressure control are the mainstay of treatment in most cases. Once these have been addressed adequately, medications such as Ivabradine can be considered for these related conditions when elevated normal heart rate is the predominant problem. These conditions can be sporadic with periods of exacerbation but generally settle over time. Medications can be weaned and restarted for as needed.

Do I need a pacemaker for slow heart rate?

It is quite uncommon to recommend a pacemaker for VVS. Many people either grow out of it or tend to have a good understanding and control of their condition with time. There are very specific criteria we use to determine if a pacemaker may be of benefit. Older people may benefit from pacemaker if these episodes are frequent, occur without warning, have long pauses in their rhythm or have severe injury as a result of their VVS.

What is the long-term outlook with VVS?

The long-term outlook is positive in people with VVS. Once adequate treatment is instituted, people can expect to lead a normal life. VVS can occur in clusters over time and can sometimes recur later in life.