The Postural Tachycardia Syndrome (POTS): pathophysiology, diagnosis & management

Abstract

Postural tachycardia syndrome (POTS), characterized by orthostatic tachycardia in the absence of orthostatic hypotension, has been the focus of increasing clinical interest over the last 15 years 1. Patients with POTS complain of symptoms of tachycardia, exercise intolerance, lightheadedness, extreme fatigue, headache and mental clouding. Patients with POTS demonstrate a heart rate increase of >or=30 bpm with prolonged standing (5-30 minutes), often have high levels of upright plasma norepinephrine (reflecting sympathetic nervous system activation), and many patients have a low blood volume. POTS can be associated with a high degree of functional disability. Therapies aimed at correcting the hypovolemia and the autonomic imbalance may help relieve the severity of the symptoms. This review outlines the present understanding of the pathophysiology, diagnosis, and management of POTS.

Figure 1

Hemodynamics with Upright Posture in POTS The tracings for heart rate, blood pressure, and tilt table angle are shown for a patient with the postural tachycardia syndrome (POTS; left) and for a healthy control subject (right) during a 30 minute tilt head-up test. With head-up tilt, the heart rte immediately increases in POTS and peaks at over 170 bpm prior to the end of the tilt. In contrast the heart rate of the healthy control subject rises to just over 100 bpm. The patient with POTS does not experience a reduction in blood pressure during the tilt test. It is largely unchanged during the test.

Figure 2

Acrocyanosis in POTS One of the more striking physical features in the postural tachycardia syndrome (POTS) is the gross change in dependent skin color that can occur with standing. The panel shows the legs of 2 people who have been standing for 5 minutes, a healthy control subject (left) and a patient with POTS (right). The patient with POTS (right) has significant dark red mottling of her legs extending up to the knees while standing, while the control subject does not have a similar discoloration.

Figure 3

Pathophysiological Schema in POTS There are multiple distinct pathophysiological subtypes within the postural tachycardia syndrome (POTS). The top panel (3a) shows a basal situation with a normal amount of sympathetic nervous system outflow from the brain that activates receptors in the blood vessels (vascular tone & venous return), heart (heart rate & contractility) and kidney (blood volume regulation through renin). Panel 3b shows a schematic of Neuropathic POTS. There is patchy denervation of the sympathetic innervation of the blood vessels in the extremities (especially the legs) and the kidney with subsequent hypovolemia and increased orthostatic venous pooling. This feeds back to the brain to increase sympathetic nervous system outflow in a compensatory effort. This increased sympathoneural flow is sensed most in the heart where there is no denervation. Panel 3c shows a schematic of Central Hyperadrenergic POTS. In this case, the underlying problem is excessive sympathetic nervous outflow from the brain that affects the blood vessels, kidneys and the heart. In addition to tachycardia, this form of POTS is often associated with orthostatic hypertension.

Figure 3

Pathophysiological Schema in POTS There are multiple distinct pathophysiological subtypes within the postural tachycardia syndrome (POTS). The top panel (3a) shows a basal situation with a normal amount of sympathetic nervous system outflow from the brain that activates receptors in the blood vessels (vascular tone & venous return), heart (heart rate & contractility) and kidney (blood volume regulation through renin). Panel 3b shows a schematic of Neuropathic POTS. There is patchy denervation of the sympathetic innervation of the blood vessels in the extremities (especially the legs) and the kidney with subsequent hypovolemia and increased orthostatic venous pooling. This feeds back to the brain to increase sympathetic nervous system outflow in a compensatory effort. This increased sympathoneural flow is sensed most in the heart where there is no denervation. Panel 3c shows a schematic of Central Hyperadrenergic POTS. In this case, the underlying problem is excessive sympathetic nervous outflow from the brain that affects the blood vessels, kidneys and the heart. In addition to tachycardia, this form of POTS is often associated with orthostatic hypertension.

Figure 3

Pathophysiological Schema in POTS There are multiple distinct pathophysiological subtypes within the postural tachycardia syndrome (POTS). The top panel (3a) shows a basal situation with a normal amount of sympathetic nervous system outflow from the brain that activates receptors in the blood vessels (vascular tone & venous return), heart (heart rate & contractility) and kidney (blood volume regulation through renin). Panel 3b shows a schematic of Neuropathic POTS. There is patchy denervation of the sympathetic innervation of the blood vessels in the extremities (especially the legs) and the kidney with subsequent hypovolemia and increased orthostatic venous pooling. This feeds back to the brain to increase sympathetic nervous system outflow in a compensatory effort. This increased sympathoneural flow is sensed most in the heart where there is no denervation. Panel 3c shows a schematic of Central Hyperadrenergic POTS. In this case, the underlying problem is excessive sympathetic nervous outflow from the brain that affects the blood vessels, kidneys and the heart. In addition to tachycardia, this form of POTS is often associated with orthostatic hypertension.

Figure 4

Blood Volume Deviation in POTS The 3 panels show the blood volumes of control subjects and patients with POTS compared to hat expected based on their individual height, weight and gender. Data are shown for plasma volume (PV; Panel A), red cell volume (RC; Panel B) and total blood volume (TBV; Panel C). The plasma volume and total blood volume of the control subjects was similar to their expected values. The patients with POT had a deficit of their plasma volume (Panel A), red cell volume (Panel B) and total blood volume (Panel C) compared to the control group. Figures adapted with data from Raj SR, Biaggioni I, Yamhure PC, Black BK, Paranjape SY, Byrne D, Robertson D. The Renin-Aldosterone Paradox and Perturbed Blood Volume Regulation Underlying the Postural Tachycardia Syndrome. Circulation 2005; 111:1574-1582.