Postural orthostatic tachycardia syndrome

Overview

Postural Orthostatic Tachycardia Syndrome (POTS) is a form of dysautonomia—a disorder of the autonomic nervous system—that primarily affects blood circulation. It is characterized by an excessive increase in heart rate (usually more than 30 beats per minute in adults or more than 40 bpm in adolescents) that occurs when transitioning from lying down to standing up, without a corresponding drop in blood pressure. POTS can lead to a wide range of symptoms that affect multiple body systems, often significantly impairing quality of life. It predominantly affects women between the ages of 15 and 50, although it can occur in people of all ages and genders.

Causes

The exact cause of POTS is not fully understood, and it is believed to be multifactorial. Some common contributing factors and associated conditions include:

• Neuropathic POTS: Caused by damage to the small fiber nerves that regulate blood vessel constriction in the limbs and abdomen.

• Hyperadrenergic POTS: Characterized by elevated levels of norepinephrine, resulting in excessive sympathetic nervous system activity.

• Hypovolemia: A reduced blood volume, which can compromise circulation and heart rate regulation.

• Autoimmune disorders: POTS has been associated with autoimmune diseases such as lupus and Sjögren’s syndrome.

• Post-viral onset: Some cases of POTS develop after a viral illness, including infections such as Epstein-Barr virus or COVID-19.

• Genetic predisposition: There may be a hereditary component, especially in families with a history of dysautonomia or connective tissue disorders.

• Deconditioning: Prolonged bed rest or inactivity can lead to POTS-like symptoms in some individuals.

Symptoms

POTS symptoms often worsen upon standing and improve when lying down. The condition is chronic and symptoms may vary in severity from day to day. Common symptoms include:

• Rapid heartbeat (tachycardia) upon standing

• Lightheadedness or dizziness

• Fatigue and exercise intolerance

• Palpitations or a feeling of heart racing

• Shakiness or tremors

• Nausea and gastrointestinal disturbances

• Brain fog or difficulty concentrating

• Headaches

• Chest pain or discomfort

• Shortness of breath

• Visual disturbances such as tunnel vision or blurred vision

• Cold or discolored extremities due to poor circulation

• Sleep disturbances

Diagnosis

Diagnosis of POTS involves a comprehensive clinical evaluation and tests to rule out other conditions. A diagnosis is typically confirmed when there is a heart rate increase of 30 bpm or more (or 40 bpm in adolescents) within 10 minutes of standing, without a significant drop in blood pressure. Common diagnostic approaches include:

• Active stand test: Heart rate and blood pressure are measured after lying down, then repeatedly during and after standing for several minutes.

• Tilt table test: The patient is strapped to a table that is gradually tilted upright, while vital signs are monitored.

• Blood tests: To check for anemia, thyroid disorders, or electrolyte imbalances.

• 24-hour heart rate monitoring: To assess variations in heart rate throughout the day.

• Autonomic function tests: To evaluate how the autonomic nervous system responds to various stimuli.

Treatment

There is no cure for POTS, but treatment aims to manage symptoms and improve quality of life. Management is highly individualized and may include a combination of the following:

Non-pharmacological Strategies

• Increasing salt and fluid intake to boost blood volume

• Wearing compression garments to reduce blood pooling in the legs

• Gradual reconditioning exercises, starting in a recumbent position

• Physical counter-maneuvers (e.g., leg crossing or muscle tensing) when standing

• Avoiding triggers such as prolonged standing, hot environments, or dehydration

Medications

• Beta blockers: Such as propranolol, to reduce heart rate

• Fludrocortisone: To help retain sodium and increase blood volume

• Midodrine: A vasoconstrictor that helps raise blood pressure

• Pyridostigmine: Enhances nerve signal transmission in the autonomic system

• Ivabradine: May be used off-label to regulate heart rate

Prognosis

The prognosis for POTS varies widely. Some individuals experience significant improvement with treatment and lifestyle modifications, especially if the condition was triggered by a viral illness or temporary stressor. Others may face long-term challenges and require ongoing management. Adolescents with POTS often show better outcomes than adults. Early diagnosis, tailored therapy, and support from knowledgeable healthcare professionals can greatly improve symptom control and overall quality of life. However, for a subset of patients, POTS can remain a debilitating chronic condition.