Postural Heart Rate Changes in Young Patients With Vasovagal Syncope Marvin S. Medow, PhD,a, b Sana Merchant, MD, a Melissa Suggs, BS, MS, a Courtney Terilli, BSN,a Breige O’Donnell-Smith, MD, a Julian M. Stewart, MD, PhDa, b BACKGROUND AND OBJECTIVES: Recurrent postural vasovagal syncope (VVS) is caused by transient abstract cerebral hypoperfusion from episodic hypotension and bradycardia; diagnosis is made by medical history. VVS contrasts with postural tachycardia syndrome (POTS), defined by chronic daily symptoms of orthostatic intolerance with excessive upright tachycardia without hypotension. POTS has recently been conflated with VVS when excessive tachycardia is succeeded by hypotension during tilt testing. We hypothesize that excessive tachycardia preceding hypotension and bradycardia is part of the vasovagal response during tilt testing of patients with VVS. METHODS: We prospectively performed head-up tilt (HUT) testing on patients with recurrent VVS (n = 47, 17.9 ± 1.1 y), who fainted at least 3 times within the last year, and control subjects (n = 15, 17.1 ± 1.0 y), from age and BMI-matched volunteers and measured blood pressure, heart rate (HR), cardiac output, total peripheral resistance, and end tidal carbon dioxide. RESULTS: Baseline parameters were the same in both groups. HR (supine versus 5 and 10 minutes HUT) significantly increased in control (65 ± 2.6 vs 83 ± 3.6 vs 85 ± 3.7, P < .001) and patients with VVS (69 ± 1.6 vs 103 ± 2.3 vs 109 ± 2.4, P < .001). HUT in controls maximally increased HR by 20.3 ± 2.9 beats per minute; the increase in patients with VVS of 39.8 ± 2.1 beats per minute was significantly greater (P < .001). An increase in HR of ≥40 beats per minute by 5 and 10 minutes or before faint with HUT, occurred in 26% and 44% of patients with VVS, respectively, but not in controls. CONCLUSIONS: Orthostasis in VVS is accompanied by large increases in HR that should not be construed as POTS. NIH WHAT IS KNOWN ON THIS SUBJECT: Recurrent Departments of aPediatrics, and bPhysiology, New York Medical College, Valhalla, New York postural vasovagal syncope (VVS) is defi ned by Drs Medow and Stewart were responsible for the design of the experiments, analysis, and episodic loss of consciousness resulting from interpretation of the data, and drafting the original manuscript; Dr Merchant, Ms Suggs, and hypotension. Upright heart rate is not specifi ed Dr O’Donnell-Smith were responsible for collection, assembly, and interpretation of the data; for VVS. Postural tachycardia syndrome (POTS) Mrs Terilli was responsible for subject recruitment, collection, assembly, and interpretation is defi ned by chronic symptoms and excess of the data; and all authors approved the fi nal manuscript as submitted. tachycardia while upright, without hypotension. DOI: 10.1542/peds.2016-3189 The defi nitions are mutually exclusive. Accepted for publication Jan 24, 2017 WHAT THIS STUDY ADDS: Orthostatic heart rate Address correspondence to Marvin S. Medow, PhD, New York Medical College, Center for (HR) increases in many patients with recurrent VVS. Hypotension, 19 Bradhurst Ave, Suite 1600 South, Hawthorne, NY 10532. E-mail: marvin_medow@ Although our patients with VVS did not have POTS, nymc.edu they had signifi cant HR increases when upright at PEDIATRICS (ISSN Numbers: Print, 0031-4005; Online, 1098-4275). 5 and10 minutes. HR increases alone do not confer Copyright © 2017 by the American Academy of Pediatrics a diagnosis of POTS. FINANCIAL DISCLOSURE: The authors have indicated they have no fi nancial relationships relevant to this article to disclose. To cite: Medow MS, Merchant S, Suggs M, et al. Postural Heart Rate Changes in Young Patients With Vasovagal Syncope. Pediatrics. 2017;139(4):e20163189 Downloaded from www.aappublications.org/news by guest on September 25, 2021 PEDIATRICS Volume 139 , number 4 , April 2017 :e 20163189 ARTICLE Imposition of an orthostatic stress, form is VVS, in which ∼40% of sought to show that HR increases such as standing up, causes a rapid people experience at least 1 episode alone do not confer a diagnosis downward displacement of ∼500 throughout life, most presenting of POTS. To test this hypothesis, to 700 mL from central stores into initially during adolescence. 17, 18 the following experiments were the splanchnic and lower extremity VVS can be elicited by upright performed. vascular beds. 1 The resulting posture and by emotional stress (eg, excessive blood pressure (BP) “blood phobia”). 19 VVS, if recurrent, decreases, and if uncompensated is characteristically episodic in METHODS can result in orthostatic hypotension otherwise healthy patients. Unlike (OH) and orthostatic intolerance POTS, which is a form of chronic OI, Subjects (OI). Rapid circulatory compensation VVS is rarely present on a daily basis. for orthostasis occurs via the To test this hypothesis, we performed In VVS due to orthostasis (ie, postural a prospective study over a 3-year sympathetic and parasympathetic VVS), changes in HR and BP can arms of the autonomic nervous period at the Center for Hypotension, occur in the following manner. Upon which is an outpatient facility of the system for appropriate heart rate standing up, there is a brief period (HR) and BP control. 2 – 6 The normal Department of Pediatrics at New during which autonomic adjustments York Medical College, Valhalla, New baroreflex response to decreased BP 20 are initialized. Thereafter, BP York. We recruited VVS subjects involves peripheral vasoconstriction stabilizes and HR increases due and a reflex tachycardia. 7, 8 with a history of recurrent fainting to increased sympathetic activity, who had fainted at least 3 times OI is the inability to tolerate compensatory vasoconstriction within the last year (47 patients upright posture that is relieved by with venous emptying, and vagal [29 female] ranging in age from 12 21–23 recumbency, and is accompanied withdrawal. Usually, BP slowly to 20 years). We also recruited 15 by signs and symptoms that include decreases and HR reflexively healthy nonfainting control subjects loss of consciousness (LOC), increases. Symptoms of OI can begin (9 female), ranging in age from 11 to cognitive deficits, loss of vision or within minutes of standing upright, 22 years. hearing, lightheadedness, headache, and if not relieved by recumbency, a fatigue, nausea and abdominal pain, later precipitous fall in BP caused by Patients who fainted were referred sweating, and tremulousness. 9 Two vasodilation followed by a fall in HR to our center for investigation after common causes of OI in younger results in LOC.11, 19 experiencing at least 3 episodes of patients are vasovagal syncope (VVS) During an upright tilt test of VVS, if fainting within the last 12 months. and postural tachycardia syndrome reflex tachycardia were excessive, Data were analyzed for those 10, 11 (POTS). as defined above, an erroneous patients who experienced VVS during Patients with POTS experience diagnosis of POTS might be made. 24, 25 our upright tilt procedure, which chronic OI plus excessive tachycardia Such a diagnosis is incorrect on duplicated their vasovagal episodes when upright in the absence of clinical grounds because POTS that occurred in the real world, and hypotension. Symptoms occur daily, is chronic OI, whereas episodic who experienced a pre- and the almost always interfere with work VVS is not. Although a diagnosis postsyncopal postdrome as described and/or school activities, and the of syncope by laboratory testing below. None of the patients with VVS illness must be present for several requires a finding of hypotension, had daily orthostatic symptoms, and months to be diagnosed. 12 – 14 this specifically excludes a diagnosis all were fully functional between Excessive tachycardia in POTS is of POTS. syncopal episodes. We also recruited control subjects from age- and BMI- defined by an increase of HR to >120 We therefore hypothesized that beats per minute during a 10-minute matched volunteers to also undergo excessive tachycardia preceding a 70° head-up tilt (HUT). There were tilt or an increase of >30 beats per hypotension and bradycardia is often minute in adults or an increase of no differences in the ages, weight, part of the vasovagal response, and and BMI between the groups. >40 beats per minute in those can be observed during tilt table 15 younger than 19 years of age. testing of patients diagnosed with Patients with VVS gave a medical Syncope is defined as a “total loss of VVS, who are free of chronic day to history and underwent a physical consciousness due to transient global day symptoms of OI, but do have examination, electrocardiography, cerebral hypoperfusion characterized postural hypotension and therefore echocardiography, and prolonged by rapid onset, short duration, and do not have POTS. And because electrocardiography monitoring if spontaneous complete recovery, ” 16 we have observed orthostatic HR needed to exclude cardiac causes for which is almost always due to increases in many patients with syncope. Control subjects, recruited hypotension. The most common recurrent VVS without POTS, we by online advertising to students at Downloaded from www.aappublications.org/news by guest on September 25, 2021 2 MEDOW et al our institution, reported no clinical finger photoplethysmograph (FMS, obtained during the baseline period, illness, no OI, and had never fainted. Amsterdam, The Netherlands) on and at 5 and 10 minutes after HUT. the right forefinger or middle finger. All data were collected for 30 seconds The diagnosis of VVS was based The Finometer uses the ModelFlow before and after the time periods. on clinical history and diagnostic algorithm to estimate beat-to-beat features encompassed predisposing Patients with VVS were tilted back to cardiac output (CO) by pulse-wave situations, prodromal symptoms, supine when fainting was imminent; analysis. Before experiments began, physical signs, and postdrome imminent postural VVS was defined ModelFlow CO was calibrated against recovery and symptoms in the by a tilt-induced decrease in MAP an Innocor inert gas rebreathing CO absence of heart disease.