Two conditions that increase heart rate often confused

By Marilynn Larkin

NEW YORK (Reuters Health) - In young people, postural tachycardia syndrome (POTS) is often confused with postural vasovagal syncope (VVS), but the two conditions are mutually exclusive, researchers say.

“Recurrent VVS is caused by transient cerebral hypoperfusion from episodic hypotension and bradycardia; diagnosis is made by medical history,” whereas POTS is “defined by chronic daily symptoms of orthostatic intolerance with excessive upright tachycardia without hypotension,” Drs. Marvin Medow and Julian Stewart of New York Medical College in Valhalla explained in a paper online March 28 in Pediatrics.

They add: “POTS has recently been conflated with VVS when excessive tachycardia is succeeded by hypotension during tilt testing.”

Drs. Medow and Stewart told Reuters Health, “We are receiving more frequent requests to evaluate patients who are being told that they have POTS simply because they experience increases in their heart rate when upright. We also see patients with postural VVS in which blood pressure falls and heart rate increases.”

“There seems to be some confusion distinguishing between these two groups because in some fainters, the heart rate increases to levels that may suggest POTS, but POTS patients do not exhibit hypotension,” they said in a joint email. “Also, POTS is chronic with day-to-day symptoms, while syncope is episodic.”

The team performed head-up tilt testing on 47 patients (29 female, mean age 18) with recurrent VVS who fainted at least three times within the last year, and 15 controls matched for age and BMI. Blood pressure, heart rate, cardiac output, total peripheral resistance, and end-tidal carbon dioxide were also measured.

Compared with lying supine, heart rate increased significantly after five- and 10-minute head-up tilt testing in both controls (65 bpm versus 83 versus 85, P<0.001) and VVS patients (69 versus 103 versus 109).

Whereas head-up tilt testing maximally increased heart rate by 20.3 beats per minute in controls, the increase in VVS patients was significantly greater, at 39.8. An increase in heart rate of at least 40 beats per minute occurred in 26% of VVS patients after the five-minute head-up tilt test and 44% after the 10-minute test, but not in controls.

“The take-home message,” Drs. Medow and Stewart say, “is that patients should not be told that they have POTS based solely on orthostatic increases in heart rate.”

Editorialist Dr. Jeffrey B. Anderson, Director, Syncope Clinic at Cincinnati Children’s Hospital in Ohio, told Reuters Health, “Patients with POTS have a variety of symptoms that are due to orthostatic intolerance and that can have significant psychologic effects as well.”

“Both POTS and VVS can typically be diagnosed with a good history and physical examination,” he said by email. “In fact, the American College of Cardiology, along with the Heart Rhythm Society and the American Heart Association, recently published guidelines that recommend minimal testing in patients presenting for these conditions.”

“Differentiating these two problems is important and is required to prescribe appropriate treatment recommendations as well as anticipatory guidance,” he stressed. “Overtesting for these medical conditions is expensive and may lead to misdiagnosis, resulting in further testing and medical system utilization.”

Dr. Daphne T. Hsu, Division Chief, Pediatric Cardiology and Co-Director, Pediatric Heart Center, Children's Hospital at Montefiore in New York City, commented, “Both of these diagnoses are made clinically, as there is no definitive test that defines one or the other. (The findings) mean that a fast heartbeat on a tilt test does not automatically mean a patient has POTS and will be prone to fainting more often.”

Treatment for either condition usually involves “lifestyle changes, with VVS patients encouraged to drink more and stay well hydrated and POTS patients encouraged to do more exercise and increase their activity levels,” she told Reuters Health by email. “But these recommendations are not absolute and often both types will respond to all therapies.”

SOURCE: http://bit.ly/2ouWTAL and http://bit.ly/2ovbAnh

Pediatrics 2017.

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