From the Guidelines
Hyperadrenergic orthostatic intolerance, also known as Postural Orthostatic Tachycardia Syndrome (POTS), is characterized by excessive sympathetic nervous system activation upon standing, with primary signs including a significant increase in heart rate and blood pressure, accompanied by symptoms such as palpitations, anxiety, tremulousness, chest pain, and shortness of breath. The condition is often associated with a marked orthostatic heart rate increase of >30 beats per minute (or >40 beats per minute in individuals 12-19 years of age) within 10 minutes of standing or head-up tilt, in the absence of orthostatic hypotension 1. Patients with POTS may experience a range of symptoms, including:
- Lightheadedness
- Palpitations
- Tremulousness
- Generalized weakness
- Blurred vision
- Exercise intolerance
- Fatigue These symptoms typically develop upon standing, are relieved by sitting or lying, and may be worse in the morning, with heat exposure, and after meals or exertion 1. The diagnosis of POTS is based on the presence of these symptoms, along with a heart rate increase of >30 beats per minute within 10 minutes of standing, and the absence of orthostatic hypotension. The pathophysiology of POTS is debated and likely heterogeneous, with proposed mechanisms including deconditioning, immune-mediated processes, excessive venous pooling, and a hyperadrenergic state 1. The condition can significantly impact quality of life and may be associated with conditions like partial dysautonomia, pheochromocytoma, or be medication-induced. It is essential to note that POTS is a distinct condition from orthostatic hypotension, and its diagnosis and management require a comprehensive approach, taking into account the patient's symptoms, medical history, and physical examination findings 1.
From the Research
Signs of Hyperadrenergic Orthostatic Intolerance (POTS)
- Symptoms of orthostatic intolerance, including lightheadedness, fatigue, altered mentation, and syncope, associated with postural tachycardia and plasma norepinephrine concentrations that are disproportionately high in relation to sympathetic outflow 2
- Palpitations due to excessive orthostatic sinus tachycardia, lightheadedness, tremor, and near-syncope 3, 4
- Increase in heart rate of at least 30 bpm (or a rate that exceeds 120 bpm) that occurs in the first 10 min of upright posture or head up tilt test (HUTT) 5
- Increase in systolic blood pressure of ≥ 10 mm Hg during the HUTT with concomitant tachycardia or serum catecholamine levels (serum norepinephrine level ≥ 600 pg/mL) upon standing 5
Pathophysiology
- Abnormal autonomic nervous system regulation, autoimmunity, a hyperadrenergic state, and hypovolemia may contribute to the pathophysiology of orthostatic intolerance and POTS 6
- Impaired functioning of the norepinephrine transporter may contribute to the pathophysiologic mechanism of orthostatic intolerance, resulting in excessive sympathetic activation in response to physiologic stimuli 2
Diagnostic Criteria
- Symptoms of orthostatic intolerance of greater than six months' duration accompanied by a heart rate increase of at least 30 bpm (or a rate that exceeds 120 bpm) that occurs in the first 10 min of upright posture or head up tilt test (HUTT) 5
- Increase in systolic blood pressure of ≥ 10 mm Hg during the HUTT with concomitant tachycardia or serum catecholamine levels (serum norepinephrine level ≥ 600 pg/mL) upon standing 5