From the Director

Clinical Challenge: Unexplained Tachycardia in 24-Year-Old Woman

The patient experienced random short bursts of chest pain and felt that she was going to pass out, starting 2 weeks before ED visit.

© B. BOISSONNE T/ SCIENCE SOURCE

The wide variety of symptoms often masks diagnosis of POTS.

A24-year-old woman presents to the clinic for follow-up after an emergency department (ED) visit for chest pain and lightheadedness. The patient, a student at a local university, reports that she was studying at the library with a friend when she suddenly felt her heart begin to race and felt “like she was going to pass out.” She says that the chest pain and lightheadedness began 30 minutes before her near-syncope.

The patient experienced random short bursts of chest pain starting 2 weeks before the ED visit. However, she describes her current pain as constant (not short bursts), located on the left side of her chest, and so severe (sharp and stabbing pain) that it makes it di cult for her to catch her breath while speaking. The earlier episodes (short bursts of chest pain) seem to have been aggravated by stress or after transitioning from a sitting to a standing position. The patient has not tried anything to alleviate her symptoms. During the ED visit, the patient rated her chest pain as 7 on a scale of 1 to 10, with 1 being very little pain and 10 being the worst pain she has felt in her life.

The patient was admitted for chest pain, palpitations (racing, skipped beats), dizziness, and shortness of breath. However, at the clinic visit, the patient denies having experienced any chest pain, dizziness, palpitations, chills, night sweats, fatigue, or weight changes. She also denies chest tightness, edema, decreased endurance, cough, or dyspnea.

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Clinic Examination

The patient is taking an oral contraceptive containing norgestimate and ethinyl estradiol (0.25 mg and 35 mg, respectively). She denies taking any over-the-counter medications or herbal supplements. She reports an allergy to penicillin that causes her to break out in a rash.

The patient underwent cholecystectomy in January 2014 and had no surgical complications. She denies any other chronic illnesses. She is up to date on all immunizations and has regular annual screening examinations. She denies tobacco, alcohol, and illicit drug use. The patient states she exercises 3 times a week and eats a balanced diet.

The patient has a family history of sudden cardiac death: her older brother passed away when he was 17 years old. She also has a family history of asthma (father and 3 brothers) as well as type 2 diabetes (maternal grandparents). She denies any other family history of chronic illness.

On presentation, the patient appears well and is alert and oriented ×4. She appears to be in acute distress but is well nourished and has no body or breath odors. She is 172.72 cm tall (68 in) and weighs 68.2 kg, with a BMI of 22.8. Vital signs are shown in Table 1 and are remarkable for an increase in heart rate of nearly 30 bpm when she transitions from supine to standing.

Physical Examination

Review of skin/hair/nails shows that the tips of the fingers and nail beds are cyanotic, with a 4-second capillary refill time. Cardiac examination shows sinus tachycardia but no other abnormalities. No abnormalities are found on respiratory assessment or examination of extremities.

The diagnostic and treatment plan for the patient’s chest pain and lightheadedness/hypovolemia are shown in Table 2.

Discussion

Postural orthostatic tachycardia syndrome (POTS) is a disorder characterized by the following 3 factors1,2: 1. Increase in heart rate of ≥30 beats per minute (or ≥40 bmp in patients aged 12-19 years) when moving from the supine to standing position; standing heart rate often is >120 beats per minute 2. Symptoms of lightheadedness, palpitations, tremor, generalized weakness, blurred vision, exercise intolerance, and fatigue 3. Absence of orthostatic hypotension

The prevalence of POTS is approximately 0.2% to 1% in developed countries; it is most common among premenopausal White women, with the majority of patients presenting between the ages of 15 and 25 years.2,3 More than 75% of patients with POTS are women.2,3 The syndrome is common in patients with chronic fatigue syndrome, anxiety, somatic hypervigilance, and autoimmune disorders.2,3

Patients with POTS present with varying symptoms, which commonly are abrupt and insidious in onset; however, some patients may experience symptoms of POTS after a viral illness, pregnancy, trauma, or surgery.2 In addition to the symptoms already mentioned, patients with POTS may experience migraine headaches, brain fog, sweating, insomnia, edema when standing, acrocyanosis, anxiety, nausea, abdominal cramps, early satiety, bloating, constipation, and diarrhea.2,3 Patients with POTS may faint, but presyncope is a more common symptom.3 Symptoms may be exacerbated by dehydration, heat, alcohol, and exercise.2 The symptoms of POTS may be cyclic in nature, with some women experiencing a worsening of symptoms during

TABLE 1. Vital Signs

Temperature, °F 98.2

Heart rate (supine), bpm 108

Blood pressure, mmHg 92/63

Respiratory rate, bpm 14

Pulse oximetry, % 100

Orthostatic vitals

Blood pressure, mmHg 97/66

Heart rate (standing), bpm 146

TABLE 2. Diagnostic and Treatment Plan

Chest Pain

Diagnostic ECG, stress ECG, chest radiograph, event monitor for 30 d

Laboratory tests CBC, BMP, thyrotropin, urine pregnancy

Treatment Atenolol 25 mg orally once daily

Education Discuss the importance of taking atenolol as directed and not abruptly stopping beta-blockers; set up sessions with physical therapist to begin exercise training

Lightheadedness and Hypovolemia

Diagnostic Orthostatic vital signs

Treatment Normal saline 1000 mL IV bolus

Education Discuss importance of high-salt diet and other strategies to avoid hypovolemic episodes

BMP, basic metabolic panel; CBC, complete blood cell count; ECG, electrocardiogram; IV, intravenous

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certain stages of their menstrual cycle associated with weight and fluid changes, and other patients experiencing a cycle of POTS symptoms lasting several days followed by a similar number of days with no or minimal symptoms.4

Etiology of POTS

Various pathophysiologic mechanisms have been described in patients with POTS, including peripheral autonomic denervation, hypovolemia, hyperadrenergic stimulation, cardiovascular deconditioning, and anxiety/hypervigilance.2,3 It is unclear which of these abnormalities are primary and causative and which are secondary. These various etiologies have led to the categorization of POTS into subtypes: neuropathic, hypovolemic, and hyperadrenergic. The various mechanisms underlying POTS may overlap, complicating diagnosis.2

Neuropathic POTS occurs in approximately 50% of cases and is associated with distal autonomic denervation, most commonly in the feet and toes.2 In this subtype, impaired sympathetic tone results in reduced venoconstriction, causing blood to pool in the lower extremities rather than return to the heart when a patient is standing.2 This decreased blood flow to the heart results in orthostasis and tachycardia.2

Hypovolemia plays a large role in the symptomatic presentation in up to 70% of patients with POTS.2 The exact cause of hypovolemia is unknown but may be related to low plasmin renin activity and aldosterone levels.2 Laboratory findings in patients with POTS has led some investigators to suggest that a renal disorder (eg, renal denervation) may play a primary role in the etiology of POTS.5 In addition, Fu et al found that cardiac size/mass and blood volume were markedly decreased in patients with POTS compared with healthy sedentary patients without POTS.6 The researchers concluded that deconditioning (ie, cardiac atrophy and hypovolemia) is a cause of POTS.6

The hyperadrenergic subtype, which occurs in up to 50% to 60% of patients with POTS, is caused by elevated levels of epinephrine and norepinephrine (≥600 pg/mL) in the blood when a patient is standing.2,3 Unlike neuropathic POTS, in which the patient’s blood pressure decreases and heart rate increases on standing, patients with hyperadrenergic POTS have an increase in both systolic blood pressure and heart rate on standing.2 Patients with this subtype tend to have sympathetic activation symptoms, including palpitations, anxiety, tachycardia, and tremor.2,3 Baroreflex transfer is impaired in all patients with POTS, further decreasing blood pressure when a patient switches from a supine to an upright position.7

Secondary POTS may be caused by underlying conditions such as diabetes, lupus, and alcoholism, as well as chemotherapy.8 Although anxiety, panic disorder, and somatic vigilance are common in patients with POTS, research suggests that the excessive heart rate response to orthostatic stress in POTS is not caused by anxiety and is a physiologic response that maintains arterial pressure during venous pooling.4,9

Diagnosis of POTS

Because POTS shares overlapping symptoms with serious medical illnesses, especially cardiac diseases, a thorough history, physical examination, and 12-lead electrocardiogram are essential to the differential diagnosis of this condition.2 Evaluation should focus on excluding cardiovascular causes, such as structural heart defects and tachyarrhythmias, as well as endocrine dysfunction.3 Select patients may benefit from the following tests2: • 24-hour Holter monitoring • Transthoracic echocardiogram • Exercise stress test • Autonomic testing • Thyroid function test and complete blood cell count • Tilt-table testing and/or standing test

Diagnosis can be aided through a standing test, which requires a patient to transition from a seated to a standing position. During the 30-minute test, the patient’s heart rate and blood pressure are measured to evaluate the body’s response to the change in position.5 Unlike orthostatic hypotension, patients with POTS will not have a decrease in blood pressure when transitioning from a seated to standing position. A head-up tilt test also is helpful in the diagnostic workup of POTS because it allows for monitoring vital signs over a longer period than the standing test.2

Treatment Options

There is no single definitive treatment for POTS, and a combination of approaches often is needed.2 Nonpharmacologic treatment approaches should be used first (Table 3, page 24).2 The American College of Cardiology recommends a regular, structured, and progressive exercise program for POTS that includes aerobic reconditioning and resistance training for the thighs.2 Research by Fu et al found that exercise training increased left ventricular mass and blood volume and decreased upright heart rate in patients with POTS; 10 out of 19 patients in this study no longer met the criteria for POTS after training, and all patients showed improved quality of life.6

Consumption of up to 2 to 4 L of water and 10 to 12 g of sodium daily also may be considered.2 Avoidance of caffeine, alcohol, prolonged heat, and use of norepinephrine transport inhibitors may be helpful.2,3

If nonpharmacologic strategies are not effective, patients with short-term clinical decompensations can be treated with an acute intravenous infusion of up to 2 L of saline.2 Treatment with fludrocortisone, pyridostigmine, midodrine, or low-dose

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TABLE 3. Guideline-Recommended POTS Treatments2

Nonpharmacologic Treatments

Exercise program

Increased water and salt intake

Compression clothing

Pharmacotherapy

≥2 L IV saline infusion

Fludrocortisone or pyridostigmine

Midodrine or low-dose propranolol

Clonidine or methyldopa (for patients with prominent hyperadrenergic features)

IV, intravenous

propranolol may be considered.2 For patients with prominent hyperadrenergic features, clonidine or methyldopa may be used.2

Results of a double-blind trial comparing propranolol to exercise in 19 patients with POTS found that both propranolol treatment and exercise training lowered standing heart rate, but only exercise was linked with an increase in plasma aldosterone to renin ratio. In addition, exercise, but not propranolol treatment, was associated with improvements in quality of life.10

In patients with hyperadrenergic POTS, the use of betablockers significantly decreased patients’ norepinephrine blood levels on standing.11 Patients initiating therapy with beta-blockers should be started on low doses and then slowly titrated until symptom relief is achieved because higher doses are not as well tolerated. Patient education on the need for a trial-and-error approach to find an effective treatment for symptomatic relief is important.

Prognosis

This condition may negatively affect quality of life; patients may avoid certain activities that caused tachycardic and hypovolemic episodes, such as sports or other physically strenuous activities, or delay activities because of persistent fatigue.

However, POTS is a manageable disease that often improves over time with proper treatment.2 In a follow-up study of 54 patients with POTS, the majority of patients (n=39; 70%) experienced symptom improvement at 1 year; 17 patients (30%) experienced worsening of symptoms.12

With adherence to exercise recommendations, diet modification, and medication regimens, patients with POTS can reduce or eliminate symptoms and improve their quality of life. Pharmacologic treatment should not be the sole therapy for patients with POTS. Clinicians should stress the importance of exercise and increased salt intake along with medications for symptom relief when counseling patients with POTS. To aid in treatment adherence and optimize outcomes, a strong patient/provider relationship is essential. ■

Laura Gillen, PA-C, works with the Augusta University Medical Center plastic surgery team in Augusta,Georgia;Tyger Meade Clayton, MPA, PA-C, works in urgent care and occupational medicine and is assistant professor in the PA Department at Augusta University.

References

1. Shen W-K, Sheldon RS, Benditt DG, et al. 2017 ACC/AHA/HRS guideline for the evaluation and management of patients with syncope: a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society. J Am Coll Cardiol. 2017;70(5):e39-e110. 2. Sheldon RS, Grubb BP 2nd, Olshansky B, et al. 2015 Heart Rhythm Society expert consensus statement on the diagnosis and treatment of postural tachycardia syndrome, inappropriate sinus tachycardia, and vasovagal syncope. Heart Rhythm. 2015;12(6):e41-63. 3. Zhao S, Tran VH. Postural orthostatic tachycardia syndrome. In: StatPearls. StatPearls Publishing; 2021 Jan. Updated August 15, 2020. Accessed August 14, 2021. https://www.ncbi.nlm.nih.gov/books/NBK541074/ 4. Low PA, Sandroni P, Joyner M, Shen W-K. Postural tachycardia syndrome (POTS). J Cardiovasc Electrophysiol. 2009;20(3):352-358. 5. Raj SR, Biaggioni I, Yamhure PC, et al. Renin-aldosterone paradox and perturbed blood volume regulation underlying postural tachycardia syndrome. Circulation. 2005;111(13):1574-1582. 6. Fu Q, Vangundy TB, Galbreath MM, et al. Cardiac origins of the postural orthostatic tachycardia syndrome. J Am Coll Cardiol. 2010;55(25):2858-2868. 7. Raj SR. Postural tachycardia syndrome (POTS). Circulation. 2013;127(23): 2336-2342. 8. Kizilbash SJ, Ahrens SP, Bruce BK, et al. Adolescent fatigue, POTS, and recovery: a guide for clinicians. Curr Probl Pediatr Adolesc Health Care. 2014;44(5):108-133. 9. Masuki S, Eisenach JH, Johnson CP, et al. Excessive heart rate response to orthostatic stress in postural tachycardia syndrome is not caused by anxiety. J Appl Physiol (1985). 2007;102(3):896-903. 10. Fu Q, Vangundy TB, Shibata S, Auchus RJ, Williams GH, Levine BD. Exercise training versus propranolol in the treatment of the postural orthostatic tachycardia syndrome. Hypertension. 2011;58(2):167-75. 11. Thieben MJ, Sandroni P, Sletten DM, et al. Postural orthostatic tachycardia syndrome: the Mayo clinic experience. Mayo Clin Proc. 2007;82(3):308-313. 12. Kimpinski K, Figueroa JJ, Singer W, et al. A prospective, 1-year follow-up study of postural tachycardia syndrome. Mayo Clin Proc. 2012;87(8):746-752.