From the Guidelines
Patients with Postural Orthostatic Tachycardia Syndrome (POTS) generally do not exhibit significant structural cardiac abnormalities. POTS is primarily a disorder of the autonomic nervous system that affects blood circulation, characterized by an abnormal increase in heart rate upon standing without corresponding blood pressure changes 1. While the heart itself is typically structurally normal in POTS patients, they may show functional cardiac changes such as reduced stroke volume, decreased cardiac output, and blood pooling in the lower extremities when upright. Some patients might demonstrate mild left ventricular remodeling or reduced ventricular mass due to deconditioning, but these are considered secondary effects rather than primary cardiac pathology. The tachycardia observed in POTS is a compensatory mechanism attempting to maintain cerebral perfusion in the face of autonomic dysfunction, not a result of intrinsic heart disease. This distinction is important because treatment focuses on managing autonomic dysfunction, increasing blood volume, and improving cardiovascular conditioning rather than addressing cardiac structural issues. Key characteristics of POTS include:
- A heart rate increase of ≥30 bpm during a positional change from supine to standing (or ≥40 bpm in those 12–19 years of age) 1
- The absence of orthostatic hypotension (>20 mm Hg reduction in systolic BP) 1
- Symptoms associated with standing, such as lightheadedness, palpitations, tremulousness, generalized weakness, blurred vision, exercise intolerance, and fatigue 1. Given the most recent evidence from 2022 1, it's clear that POTS is a complex condition with various manifestations, but cardiac abnormalities are not typically a primary concern.
From the Research
Cardiac Abnormalities in POTS
- Patients with Postural Orthostatic Tachycardia Syndrome (POTS) often exhibit cardiac abnormalities, including orthostatic intolerance and a symptomatic increase in heart rate upon standing 2.
- The pathophysiology of POTS is complex and multifactorial, involving various mechanisms such as hyperadrenergic, neuropathic, and hypovolemic phenotypes 2, 3.
- Cardiac abnormalities in POTS can be managed with lifestyle modifications, including increased fluid and salt intake, compression garment use, physical reconditioning, and postural training 2.
- Pharmacologic therapies, such as beta-blockers, ivabradine, and midodrine, can be used to manage specific symptoms of POTS, including excessive heart rate and orthostatic intolerance 4, 5, 6.
Types of Cardiac Abnormalities
- Hyperadrenergic POTS is characterized by excessive norepinephrine production or impaired reuptake, leading to sympathetic overactivity and making beta-blockers an effective treatment option 2.
- Neuropathic POTS is characterized by impaired vasoconstriction during orthostatic stress, and responds to agents that enhance vascular tone, such as pyridostigmine and midodrine 2.
- Hypovolemic POTS is often triggered by dehydration and physical deconditioning, and responds primarily to volume expansion and exercise 2.
Treatment Options
- Ivabradine, a heart rate lowering agent, has been shown to be effective in reducing heart rate and providing symptomatic relief in patients with POTS 4, 5.
- Midodrine, an agent that enhances vascular tone, has also been shown to be effective in improving symptoms in patients with POTS 5, 6.
- Beta-blockers, which reduce heart rate and blood pressure, can be used to manage symptoms of POTS, particularly in patients with hyperadrenergic POTS 2, 3, 6.