What is Carotid Sinus Hypersensitivity?
Carotid sinus hypersensitivity (CSH) is a condition that often results in fainting, also known as syncope. This happens because certain receptors in the carotid sinus, a part of the body where the internal and external carotid arteries (the main arteries of the neck) come together to form what’s known as the common carotid artery, react excessively when stimulated.
These receptors, known as baroreceptors (from the Greek word “baro”, meaning pressure or stretch), send signals through a nerve (the glossopharyngeal nerve) to a part of the brain (the solitary nucleus in the medulla). If these receptors detect increased pressure or stretch, they activate the parasympathetic nervous system, a part of your nervous system that helps your body rest and relax. This leads to vasodilation (widening of the blood vessels), bradycardia (slowed heart rate), and hypotension (low blood pressure). Lowered blood pressure then lessens the effect of these baroreceptors.
However, in order to officially diagnose someone with CSH, they must either have a pause in their heart rate for 3 seconds or more, known as “asystole” (referring to the heart’s inability to contract normally), or a decrease in systolic blood pressure (the pressure in your arteries during the contraction of your heart muscle) by 50 mmHg or more, termed as “hypotension”. If fainting occurs due to low blood pressure and a slow heart rate after a carotid sinus massage (a gentle pressing of the neck to stimulate the carotid sinus), the condition is termed as mixed (both heart and blood pressure related), even if the person doesn’t show any symptoms.
There are three types of CSH: cardioinhibitory, where the heart rate slows; vasodepressor, where the blood pressure drops; and a mixed type, a combination of the two situations.
What Causes Carotid Sinus Hypersensitivity?
We don’t exactly know what causes CSH, or carotid sinus hypersensitivity. However, we do know that it mostly occurs in people over the age of 50. It’s also more common in men, especially those who already have long-term health conditions like high blood pressure, heart disease, diabetes, and issues with their heart valves.
CSH also seems to be linked with brain conditions like Parkinson’s disease, Alzheimer’s disease, and dementia with Lewy bodies. In fact, people with these conditions tend to have higher rates of CSH.
Scientists believe that the cause of CSH might be linked to damage in a part of the brain called the medullary autonomic nuclei. This part of the brain senses signals from baroreceptors, a type of sensor in your body that helps to regulate and maintain your blood pressure. When there is damage in this area, your body might respond too strongly to these signals. The result is low blood pressure and a slow heart rate, both of which are symptoms of CSH.
Risk Factors and Frequency for Carotid Sinus Hypersensitivity
Carotid sinus hypersensitivity, or CSH, is more common in the United States than one might think, with 35 to 40 cases reported per year for every million people. It’s more prevalent in older individuals and fairly uncommon among younger people. In fact, men are more likely to suffer from CSH than women – the ratio being 4 to 1.
As people age, the likelihood of them having CSH goes up — the prevalence rate is 2.4% for people in their 60s, and then it jumps to 9.1% for people in their 70s. By the time individuals reach 80 years old, a whopping 40% of them could have CSH.
CSH is prevalent worldwide as well, especially among elderly people who experience unexplained fainting or syncope – it accounts for almost 30% of such cases. Among those living in nursing homes, 14% may suffer from CSH. However, it’s important to note that other conditions may cause fainting too, so there’s some overlap in these statistics.
- The different forms of CSH show up with varying frequency: cardioinhibitory is at 70%, vasopressor at 10%, and mixed type at 20%.
Signs and Symptoms of Carotid Sinus Hypersensitivity
Patients with Carotid Sinus Hypersensitivity (CSH) often have a medical history that includes high blood pressure, diabetes, heart disease, along with neurodegenerative disorders like Parkinson’s and Alzheimer’s diseases. If these patients undergo a physical exam, it might look normal except for the signs related to these diseases.
The main symptoms of CSH are:
- Near fainting or fainting
- Unexplained falls
- Changes in vision before losing consciousness (like darkening of the visual field)
The physical examination may show:
- Low blood pressure
- Pale skin
- Slow heart rate
- Bruises from fall-related injuries
It’s crucial to figure out the reason behind falls or fainting in older individuals, because important conditions can be missed, such as severe narrowing of the aortic valve (aortic stenosis), abnormal heart rhythms (arrhythmias), or neurological conditions like seizures or stroke. Missing these diagnoses can be particularly dangerous if the individual has repeated fainting episodes while driving, swimming, diving, parachuting, or operating heavy machinery. Meanwhile, CSH can occur without causing any symptoms and might only be noticed during a procedure called a carotid massage.
Rarely, there have been cases described in the medical literature where tumors in the head and neck have caused an overreaction of the carotid sinus, due to the tumor pressing on the blood pressure sensors (baroreceptors). How this would be managed would depend on various factors including the type and stage of the tumor, the patient’s age, and prognosis.
Testing for Carotid Sinus Hypersensitivity
If a person faints or experiences a sudden loss of consciousness, doctors follow multiple steps to find out the reason. Initial steps include checking vital signs, testing for low blood pressure when standing up (orthostatic hypotension), and asking about past instances of dehydration due to coughing, urination, or exercise. Detailed family, medical and surgical history is collected; especially instances of sudden cardiac death in the family or if the person has had gastrointestinal surgery which leads to unusual fainting after eating.
Doctors often conduct several tests to narrow down the reason for fainting. This includes a complete blood count, a basic metabolic panel, and a glucose test using a fingerstick (as low blood glucose can lead to fainting). Additionally, an electrocardiogram or ECG (which checks the heart’s electrical activity) and in some cases, an echocardiogram (an ultrasound of the heart) can be helpful. To check for small strokes or temporary blockages of blood flow to the brain, doctors perform a neurological exam. They also utilize a tilt table test which checks how blood pressure responds to changes in position and is used in diagnosing conditions like vasovagal syncope and orthostatic hypotension. If doctors suspect a neurological cause of fainting, a CT scan of the brain or an EEG (a test to check the brain’s electrical signals) may be performed.
To diagnose Carotid Sinus Hypersensitivity (CSH), a condition which may cause fainting, a carotid massage is often performed under observation. This involves massaging an area near the front of the neck where the carotid artery divides. The massage is normally done on the right side first, before moving to the left, if needed. This is done with the patient lying flat and the massage lasts 5 to 10 seconds.
However, carotid massages are not suitable for everyone. It shouldn’t be performed on people known to have had a stroke, heart attack, or a minor, temporary stroke (TIA) in the last three months. It is also ill-advised for those with certain arrhythmia conditions or whose carotid artery makes an abnormal sound when examined using a stethoscope. An ultrasound test of the carotid artery should be done to check for narrowing and if the narrowing is severe, the massage shouldn’t be performed. These are considered as contraindications, i.e., circumstances that suggest this procedure should not be carried out, for a carotid massage.
Treatment Options for Carotid Sinus Hypersensitivity
Patients with Carotid Sinus Hypersensitivity (CSH) should be informed about their condition and what might trigger an event. There are two types of CSH events: cardioinhibitory, which involves a decrease in heart rate, and vasodepressor, which involves a decrease in blood pressure. You should avoid activities that might stimulate the area around the carotid sinus in the neck, such as wearing tight collars or neck manipulations during activities like getting a massage or chiropractic treatment. It’s also important to manage any other medical conditions you may have, such as high blood pressure or diabetes.
If you have been diagnosed with CSH but have not experienced any symptoms or events related to the condition, you usually don’t need further evaluation or treatment. This conclusion is reached when you’re being evaluated for fainting (syncope) due to causes other than CSH.
For patients who have no symptoms of CSH but have experienced an event during a monitored carotid massage, a test where a doctor applies gentle pressure on the neck to stimulate the carotid sinus, no further treatment is usually needed. The best approach is to steer clear of situations that might trigger CSH events while also keeping on top of any other health conditions.
However, if you have symptoms of CSH, the type of treatment you need will depend on the subtype of CSH you have.
If you have the vasopressor subtype where blood pressure drops significantly, you might be advised to increase your salt intake and stay well-hydrated, providing that you don’t have high blood pressure or heart failure which can worsen with increased salt and fluid intake. If these basic measures don’t alleviate your symptoms, you may be prescribed medications like fludrocortisone or midodrine, which help increase blood pressure. It’s important to monitor and adjust these medications carefully to avoid negatively affecting blood pressure and CSH events.
For the cardioinhibitory subtype of CSH, where the heart rate significantly decreases, a dual-chamber pacemaker might be inserted. This device helps control your heart’s rhythm by stimulating both the upper and lower chambers of the heart. It’s used in this type of CSH because, in some cases, there can be a complete blockage in the heart’s electrical signals – this device helps overcome that. If you have a mixed subtype of CSH, where both blood pressure and heart rate decrease significantly, a pacemaker can also be very helpful.
In the past, surgical or radiologic procedures were used to treat CSH by disrupting the nerves in the carotid sinus. However, these methods are no longer used due to associated complications.
What else can Carotid Sinus Hypersensitivity be?
Carotid Sinus Hypersensitivity (CSH) can sometimes cause fainting, or syncope, which can be tricky to understand and diagnose especially when a person doesn’t report a stimulation of the carotid artery like a sudden movement of the neck or a quick change in blood pressure. Here are some conditions that could be mistaken for CSH:
- Vasovagal syncope, which often happens due to pain or seeing blood and is usually preceded by warning signs such as feeling faint, lightheaded, or nauseous.
- Situational syncope, which can be triggered by actions that dramatically increase pressure in the abdomen like coughing, going to the toilet, or urinating.
- Orthostatic hypotension, which is a drop in blood pressure when you stand up from sitting or lying down.
- Syncope caused by heart problems (cardiogenic syncope) or abnormal heart rhythms (arrhythmias).
- Heart attacks (myocardial infarction).
- Life-threatening blood clot in the lungs (pulmonary embolism).
- Severe narrowing of the heart’s aortic valve (aortic stenosis).
- Seizures.
- Thickening of heart muscle (hypertrophic cardiomyopathy).
- Short-term reduced blood flow to the brain (transient ischemic stroke).
- Fainting caused by conditions that affect body’s metabolism (for example, low blood sugar).
- Medication side effects.
Hence, a comprehensive approach that does not ignore crucial conditions is required during the diagnosis process. Each case of fainting should be thoroughly examined and tested with a proper diagnostic plan to ensure correct management. However, some cases of fainting may remain without a clear cause.
What to expect with Carotid Sinus Hypersensitivity
Patients with CSH, or Carotid Sinus Hypersensitivity, have the same likelihood of mortality as the general population, meaning that the condition itself isn’t seen as dangerous. However, what primarily concerns these patients are injuries related to fainting episodes. An unexpected fall or suddenly losing consciousness in serious situations can lead to major injuries, like multiple fractures or bleeding within the skull. This is particularly concerning for many older patients who take medications that prevent blood clots, as these can potentially lead to life-threatening consequences.
Possible Complications When Diagnosed with Carotid Sinus Hypersensitivity
The biggest issue to be mindful of are falls that happen accidentally. This can be a serious concern, particularly in elderly populations who are residing in care facilities. These individuals might be taking medications that stop their blood from clotting, have weak bones due to osteoporosis, not be good candidates for surgery, or run the risk of experiencing complications post-surgery. Another concern comes when performing a neck procedure meant to diagnose health conditions. If those doing the procedure are not thorough in their assessment of the neck’s health (they skip the step of listening for abnormal sounds using a stethoscope or don’t check for narrowing of the carotid artery), it can cause a stroke.
Considerations to note:
- Accidental falls in elderly populations
- Potential issues related to anticoagulants and osteoporosis
- Possibility of not being suitable for surgical treatment
- Risk of complications after surgery
- Risk of stroke while undergoing a carotid massage for diagnosis
- Missing a comprehensive neck evaluation which includes checking for abnormal sounds or narrowing of the carotid artery
Preventing Carotid Sinus Hypersensitivity
It’s important for patients to understand their disease and how it affects their health. An example of this is in conditions that involve the sinus node, which helps control the heart rate. Patients are advised to avoid wearing tight clothing around the neck and not to put too much pressure on the area near the sinus node, such as when shaving. This is a part of managing the disease.
Patients should also take precautions to avoid certain activities that require full awareness like driving, operating heavy equipment, or participating in water activities like swimming or diving. The rules for driving can vary based on where you live, and your doctor can give you guidance on this.
However, there are treatments available that may allow patients to return to these activities. For example, some patients may benefit from a device called a pacemaker, which helps regulate the heart rate. If a pacemaker is implanted for a certain type of condition called cardioinhibitory CSH, the patient might be able to drive again a week after the procedure. Patients with another type called vasodepressor subtype might be able to return to previous activities once their blood pressure is stabilized.
