Postural orthostatic tachycardia syndrome (POTS) is a disorder that affects blood flow and can cause an abnormally fast heart rate and lightheadedness or fainting when standing up. Some research has linked POTS to an increased risk of stroke, but the connection is not fully understood. In this article, we’ll explore the relationship between POTS and stroke and look at the potential mechanisms behind it.
What is POTS?
POTS is a form of dysautonomia, meaning it is caused by a malfunction of the autonomic nervous system. This is the system that controls involuntary bodily functions like heart rate, blood pressure, digestion, and more.
In POTS, the autonomic nervous system does not properly constrict blood vessels and increase heart rate in response to postural changes. Normally when you stand up, gravity causes blood to pool in the legs and abdomen. Baroreceptors in the arteries detect this change in blood flow and pressure. They send signals to the brain to constrict blood vessels and increase heart rate to maintain blood supply to the brain.
In POTS, this compensatory mechanism does not work properly. Heart rate increases only partially or not at all. This means blood pools in the legs when standing, and insufficient blood returns to the heart and reaches the brain.
The most common symptoms are:
– An increase in heart rate of 30 beats per minute or more within 10 minutes of standing, or heart rate over 120 bpm when standing
– Dizziness, lightheadedness, and fainting upon standing
– Palpitations and fast heart rate
– Fatigue, exercise intolerance, nausea, tremors, and headaches
POTS often begins after a viral illness, pregnancy, surgery, trauma, or other event that temporarily worsens orthostatic intolerance. It mainly affects women between the ages of 15 and 50. An estimated 1 to 3 million Americans have POTS.
How could POTS increase stroke risk?
Research suggests there are several ways POTS could potentially increase the risk of stroke:
With POTS, blood pressure can drop suddenly when standing due to insufficient constriction of blood vessels. This is called orthostatic hypotension.
Low blood pressure reduces blood flow to the brain. If blood flow is diminished long enough, it can cause ischemia – lack of oxygen to brain tissues. Ischemic strokes happen when an artery supplying the brain becomes blocked.
Orthostatic hypotension from POTS could theoretically trigger ischemic strokes through chronic low blood flow to the brain. However, there is little research evidence directly linking the two conditions.
Many people with POTS experience heart rhythm abnormalities like skipped heart beats or rapid, irregular heart rates. These are known as arrhythmias.
Certain arrhythmias, especially atrial fibrillation, increase the risk of stroke. When the upper chambers of the heart quiver chaotically in atrial fibrillation, blood can pool and form clots. If a clot travels to the brain, it triggers a stroke.
Some studies have found higher rates of arrhythmias like inappropriate sinus tachycardia and premature ventricular contractions in people with POTS. It’s possible these arrhythmias could raise stroke risk. But again, no studies have directly tied POTS-related arrhythmias to stroke.
Excessive blood pooling in the legs and abdomen is a hallmark of POTS. This reduces the amount of blood returning to the heart. Stagnant blood is more prone to developing clots.
If a clot formed in the legs traveled to the brain, it could potentially cause an ischemic stroke. However, this mechanism remains theoretical.
Some research using brain imaging has found people with POTS have reduced blood flow to the brain compared to healthy controls. This is called cerebral hypoperfusion.
One study using MRI found cerebral blood flow decreased by 27% in POTS patients compared to controls when moving from a supine to upright position. Reduced brain blood flow could potentially deprive brain tissue of oxygen, leading to strokes. But this study was small, with only 14 POTS patients.
There is some evidence that autoimmune mechanisms may play a role in a subset of POTS cases. Autoimmune disorders like lupus and Sjogren’s syndrome have been linked to increased stroke risk.
If immune system abnormalities contribute to POTS in some patients, this could theoretically also raise the risk of stroke. But more research is needed to understand if and how autoimmunity contributes to POTS and stroke risk.
What does the research say?
There are a few small studies that have investigated stroke prevalence in POTS patients, with mixed results:
– A 2018 study of 171 POTS patients found a 7% rate of stroke/TIA – much higher than the 0.7% rate in the general population.
– A 2015 study found a 4.2% rate of ischemic stroke in 140 POTS patients, again higher than general population rates.
– However, a 2019 study of 456 POTS patients found no increased risk of stroke compared to controls. The stroke rate was 0.4%, similar to the general population.
Overall the research is limited and conflicting. Larger studies are still needed to understand if POTS definitively increases stroke risk and the strength of the relationship. POTS is also frequently associated with related conditions like mast cell activation syndrome and Ehlers-Danlos syndrome that themselves increase stroke risk.
Who may be at highest risk?
There are likely certain POTS patients that could be at increased risk of stroke, including:
– Those with very high blood pressure drops upon standing. Drops of 25+ mm Hg systolic increase stroke risk.
– Those with arrhythmias like prolonged tachycardia, atrial fibrillation, or frequent PVCs.
– Anyone with a history of migraine headaches, which raise stroke risk. Migraines are common in POTS.
– Those with high blood thickness or hypercoagulability. This increases clotting risk.
– Anyone with an autoimmune disorder in addition to POTS.
– POTS patients over age 50. Stroke risk increases with age.
– Those with cardiovascular risk factors like hypertension, diabetes, or high cholesterol.
– Anyone with a history of smoking, which doubles stroke risk.
– Those with a family history of stroke. Genetics can increase risk.
– POTS patients with elevated D-dimer or C-reactive protein levels, indicating increased blood clotting and inflammation.
– People with clinical markers of impaired blood flow like retinopathy or endothelial dysfunction.
Can treating POTS reduce stroke risk?
There are several treatments for POTS that could theoretically lower stroke risk by improving blood flow:
– **Increasing fluid and salt intake** – Promotes blood volume expansion and reduces orthostatic drops in blood pressure.
– **Compression stockings** – Prevent blood pooling in legs.
– **Exercise** – Improves cardiovascular fitness.
– **Medications** like beta blockers or Midodrine – Help maintain blood pressure.
– **Ivabradine** – Lowers heart rate.
– **Fludrocortisone** – Increases blood volume.
– **Pyridostigmine** – Improves orthostatic intolerance.
Lifestyle adjustments like slowly moving from sitting to standing, elevating the head of the bed, and avoiding triggers like heat, alcohol, and prolonged standing can also minimize drops in blood pressure and therefore could hypothetically lower stroke risk.
While these treatments improve POTS symptoms, no studies have specifically looked at their impact on stroke risk. More research would be needed to know if they directly reduce the chance of stroke in POTS patients.
In summary, POTS may potentially increase the risk of stroke through effects like orthostatic hypotension, arrhythmias, blood pooling, and cerebral hypoperfusion. However, the link is not fully proven, and stroke risk likely varies significantly among individual POTS patients. Those with very low blood pressure, arrhythmias, and vascular risk factors are likely at highest risk. More large-scale studies are needed to clarify the relationship between POTS and stroke. In the meantime, POTS patients should be vigilant about controlling vascular risk factors and other stroke contributors like hypertension, smoking, and diabetes. Treatments that improve blood pressure and heart rate may lower stroke risk by minimizing the blood flow changes that can occur in POTS.