Postural Orthostatic Tachycardia Syndrome (POTS) is a complex condition involving the autonomic nervous system, which regulates involuntary bodily functions like heart rate and blood flow. When a person with POTS stands up, they experience an abnormally large increase in heart rate, often accompanied by symptoms such as dizziness and fatigue. Heat generally exacerbates POTS symptoms. This occurs because the body’s natural response to heat directly conflicts with the existing circulatory challenges faced by those with this syndrome.
The Physiological Impact of Heat
When exposed to heat, the body initiates a cooling process involving peripheral vasodilation. This is when blood vessels near the skin’s surface widen, allowing warm blood to flow closer to the air and facilitating heat transfer away from the body. This process can increase blood flow to the skin by as much as 5 to 7 liters per minute to optimize heat dissipation.
For a person with POTS, who already experiences blood pooling in the lower extremities upon standing, this widespread vasodilation presents a significant challenge. The widened vessels in the skin act as a larger container for blood, which further reduces the amount of blood returning to the heart and brain. This decrease in central blood volume, known as central hypovolemia, intensifies the circulatory problems that define the syndrome.
Increased sweating is the body’s primary evaporative cooling mechanism. While necessary for thermoregulation, high sweat rates can lead to significant fluid loss, potentially up to 3 liters per hour in extreme conditions. This rapid volume depletion further decreases circulating blood volume, making it harder for the heart to pump and maintain blood pressure. This fluid loss also flushes out electrolytes, such as sodium and potassium, which are necessary for proper nerve and muscle function.
How Heat Intensifies POTS Symptoms
The cardiovascular system compensates for the reduction in central blood volume and blood pressure caused by heat and vasodilation. The heart attempts to correct this imbalance by increasing its rate, which intensifies the hallmark symptom: tachycardia. This rapid heart rate increase is a stress response that often results in palpitations and chest discomfort.
The body’s inability to effectively manage blood flow under heat stress also worsens neurological symptoms. Reduced blood flow to the brain, even a temporary decrease, can trigger lightheadedness, dizziness, and pre-syncope. Heat stress can also contribute to more pronounced fatigue and “brain fog,” including difficulty with concentration and memory.
Heat intolerance is itself a common symptom in POTS. This discomfort is amplified by the autonomic nervous system’s impaired ability to regulate body temperature, making it difficult to cool down properly. Even simple daily activities, like taking a hot shower, can trigger a severe worsening of symptoms due to the heat-induced vasodilation.
Essential Heat Management Strategies
Managing heat is a proactive effort that centers on maintaining blood volume and lowering core body temperature. Aggressive hydration is a fundamental strategy, but it must include essential electrolytes, particularly sodium, for effective fluid retention. Many healthcare providers recommend a sodium intake significantly higher than the standard dietary recommendation, sometimes ranging from 3,000 to 6,000 milligrams per day, which should be discussed with a doctor.
External cooling methods are highly effective at reducing the physiological strain of heat. Cooling vests can be worn to keep the core body temperature down, and studies have shown they can reduce cardiovascular strain. Simple tools like cooling towels, which use evaporative cooling, or personal handheld fans can provide immediate relief when symptoms begin to escalate.
Lifestyle adjustments can minimize heat exposure and conserve energy throughout the day. Time necessary outdoor activities, such as errands or exercise, for the cooler morning or evening hours. Wearing light-colored, loose-fitting clothing made of moisture-wicking fabrics can also help the body regulate temperature more efficiently. Immediately move to a cool environment at the first sign of increased heart rate or lightheadedness.