Orthostatic Hypotension (OH) and Postural Orthostatic Tachycardia Syndrome (POTS) are conditions affecting the body’s ability to regulate blood pressure and heart rate upon standing. While they share some overlapping symptoms, they are distinct conditions with different underlying physiological mechanisms.
Understanding Orthostatic Hypotension
Orthostatic Hypotension (OH) is characterized by a significant drop in blood pressure when a person stands up from a sitting or lying position. This involves a sustained decrease in systolic blood pressure of at least 20 mm Hg or diastolic blood pressure of at least 10 mm Hg within three minutes of standing. This drop occurs because the body fails to adequately compensate for the gravitational pooling of blood in the lower extremities.
Common symptoms of OH include dizziness, lightheadedness, blurred vision, weakness, and sometimes fainting upon standing. These symptoms usually resolve when the person sits or lies down. OH can be caused by various factors, such as dehydration, certain medications, prolonged bed rest, or underlying medical conditions like diabetes or Parkinson’s disease. It is more prevalent in older adults.
Understanding POTS
Postural Orthostatic Tachycardia Syndrome (POTS) is a form of dysautonomia, a disorder of the autonomic nervous system that regulates involuntary bodily functions. It is defined by an abnormal and sustained increase in heart rate upon standing, typically without a significant drop in blood pressure that would meet the criteria for OH. For adults, this means an increase of 30 beats per minute (bpm) or more, or a heart rate exceeding 120 bpm, within 10 minutes of standing.
POTS presents with a wide array of symptoms beyond an elevated heart rate. These can include lightheadedness, severe fatigue, brain fog, heart palpitations, exercise intolerance, and gastrointestinal issues. Other symptoms may involve headaches, shakiness, chest pain, shortness of breath, and a reddish-purple discoloration of the legs upon standing. While the exact cause is often unknown, POTS can sometimes be triggered by events like viral infections, surgery, or trauma.
Similarities and Differences Between OH and POTS
Both Orthostatic Hypotension and POTS manifest with symptoms triggered or worsened by an upright posture, indicating an issue with blood pressure and blood flow regulation when standing. Lightheadedness and dizziness are common symptoms shared by both conditions. However, their specific physiological responses are distinct.
The primary difference lies in the defining physiological change upon standing. OH is characterized by a significant drop in blood pressure, where the body fails to adequately maintain blood pressure. In contrast, POTS is defined by an excessive increase in heart rate, with blood pressure remaining relatively stable or experiencing only a mild, non-diagnostic drop.
POTS often involves a broader range of symptoms compared to isolated OH. Patients with POTS commonly report severe fatigue, cognitive difficulties (“brain fog”), and gastrointestinal issues, which are not typically primary symptoms of OH. The underlying mechanisms also differ; OH often results from insufficient constriction of blood vessels or an inadequate increase in heart rate to counteract gravity, leading to reduced blood flow to the brain. POTS involves a complex dysregulation of the autonomic nervous system, leading to an exaggerated heart rate response as the body attempts to compensate for perceived inadequate blood return to the heart.
Diagnosing and Managing Both Conditions
Diagnosis for both conditions involves assessing blood pressure and heart rate changes in response to positional changes. Common diagnostic tools include the tilt-table test, where a person lies on a table that is then tilted upright while vital signs are monitored. An active stand test, measuring blood pressure and heart rate at intervals after standing from a supine position, can also be used. Blood tests may be performed to rule out other conditions.
Management strategies for OH and POTS share common approaches but also include specific treatments tailored to each condition. Non-pharmacological interventions for both involve increasing fluid and salt intake to boost blood volume, and wearing compression garments to reduce blood pooling in the legs. Gradual physical reconditioning, often starting with exercises performed while lying down, can also be beneficial. Medication choices depend on the specific physiological imbalance; for OH, medications may aim to increase blood pressure. For POTS, medications might focus on reducing heart rate or managing specific autonomic symptoms. It is important to consult a healthcare professional for an accurate diagnosis and a personalized management plan.