The Clinical and Electroencephalographic Spectrum of Tilt-Induced Syncope and “Near Syncope” in Youth

BackgroundThe aim of the study was to characterize the clinical and electroencephalographic (EEG) patterns associated with tilt-induced reflex syncope and delayed orthostatic hypotension without syncope in youth.MethodsWe conducted a prospective observational study of 95 patients referred to a pediatric neurology clinic for head-upright tilt testing. Clinical signs, symptoms, video EEG, and continuous blood pressure and heart rate were monitored.ResultsEighty patients had reflex syncope, and 15 had delayed-onset hypotension without syncope. The mean age was 15.3 (standard deviation ±2.3) years; 75 (78.9%) were female. All patients with hypotension only had corresponding signs and symptoms; 13 (86.7%) had corresponding EEG slowing. The duration of EEG slowing with hypotension far exceeded the presyncope interval from onset of slowing to loss of consciousness among patients with syncope (P < 0.001). Although prior near-syncope and presyncope episodes were reported commonly in both groups, patients with delayed hypotension without syncope were less likely to have experienced loss of consciousness during episodes of orthostatic intolerance (P < 0.001). Patients with syncope had either slow-flat-slow (n = 23) or slow-only (n = 57) EEG patterns. Compared to those with slow-only EEG patterns, patients with the slow-flat-slow pattern had greater rates of asystole (P < 0.001), myoclonic movements (P < 0.001), facial grimace (P = 0.003), vocalizations (P = 0.002), and arm flexion (P < 0.001) or extension (P = 0.006) during tilt-induced syncope.ConclusionsAmong otherwise healthy youth, orthostatic signs and symptoms vary across the spectrum of tilt-induced reflex syncope and delayed hypotension without syncope. Delayed hypotension without syncope may represent the poorly defined phenomenon of “near syncope” in some patients.     

Hemodynamic and neurohumoral responses to head-up tilt in patients with chronic fatigue syndrome

Background: Data on the prevalence of orthostatic intolerance (OI) in patients with chronic fatigue syndrome (CFS) are limited and controversial. We tested the hypothesis that a majority of CFS patients exhibit OI during head-up tilt. Methods: Hemodynamic and neurohumoral responses to 40 minutes of head-up tilt were studied in 36 CFS patients and 36 healthy controls. Changes in stroke volume, cardiac output and peripheral vascular resistance were estimated from finger arterial pressure waveform analysis (Modelflow). Blood samples were drawn before and at the end of head-up tilt for measurement of plasma catecholamines. Results: At baseline, supine heart rate was higher in CFS patients (CFS: 66.4 ± 8.4 bpm; controls: 57.4 ± 6.6 bpm; p < 0.001) as was the plasma epinephrine level (CFS: 0.11 ± 0.07 nmol/l; controls: 0.08 ± 0.07 nmol/l: p = 0.015). An abnormal blood pressure and/or heart rate response to head-up tilt was seen in 10 (27.8 %) CFS patients (6 presyncope, 2 postural tachycardia, 2 tachycardia and presyncope) and 6 (16.7 %, p = 0.26) controls (5 presyncope, 1 tachycardia, 2 tachycardia and presyncope). Head-up tilt-negative CFS patients showed a larger decrease in stroke volume during tilt (−46.9 ± 10.6) than head-up tilt-negative controls (−40.3 ± 13.6 %, p = 0.008). Plasma catecholamine responses to head-up tilt did not differ between these groups. Conclusion: Head-up tilt evokes postural tachycardia or (pre)syncope in a minority of CFS patients. The observations in head-up tilt-negative CFS patients of a higher heart rate at baseline together with a marked decrease in stroke volume in response to head-up tilt may point to deconditioning. Received: 20 July 2001, Accepted: 19 February 2002     

Comparison of the active standing test and head-up tilt test for diagnosis of syncope in childhood and adolescence

Abstract We examined 51 children and adolescents with orthostatic symptoms using two orthostatic tests, the active standing test (the AS test) and head-up tilt test (HUT), and compared circulatory responses, autonomic function in addition to the induction rate of syncope during short-time orthostasis. Syncope was induced in eight patients with both tests, in only six patients with the AS test and in only one patient with HUT. The induction rate was significantly higher with the AS test (p<0.0001). In addition, the AS test is common and daily postural motion and does not require a tilt table. We calculated percent changes in systolic blood pressure at the initial drop (ID-SBP), in systolic blood pressure (SBP), in diastolic blood pressure (DBP), in heart rate (HR), component coefficient variation LF/HF (LF/HF) from supine to upright. HR were significantly larger in fainters than in non-fainters with both tests, although there was no difference in SBP and in DBP. In six fainters only with the AS test, HR was significantly larger with the AS test than with HUT. With the AS test ID-SBP were correlative with LF/HF, and LF/HF were correlative with HR, whereas these relations were not clear in HUT. These results indicated the AS test caused cardiac sympathetic activation associated with an initial pressure drop, and was more prone to induce syncope with a greater HR increase in some patients. We conclude the AS test is as potential as HUT as a diagnostic test for syncope.     

Baroreflex dysfunction induced by microgravity: potential relevance to postflight orthostatic intolerance

Microgravity imposes adaptive changes in the human body. This review focuses on the changes in baroreflex function produced by actual spaceflight, or by experimental models that simulate microgravity, e.g., bed rest. We will analyze separately studies involving baroreflexes arising from carotid sinus and aortic arch afferents (high-pressure baroreceptors), and cardiopulmonary afferents (low-pressure receptors). Studies from unrelated laboratories using different techniques have concluded that actual or simulated exposure to microgravity reduces baroreflex function arising from carotid sinus afferents (carotic-cardiac baroreflex). The techniques used to study the carotid-cardiac baroreflex, using neck suction and compression to simulate changes in blood pressure, have been extensively validated. In contrast, it is more difficult to selectively study aortic arch or cardiopulmonary baroreceptors. Nonetheless, studies that have examined these baroreceptors suggest that microgravity produces the opposite effect, ie, an increase in the gain of aortic arch and cardiopulmonary baroreflexes. Furthermore, most studies have focus on instantaneous changes in heart rate, which almost exclusively examines the vagal limb of the baroreflex. In comparison, there is limited information about the effect of microgravity on sympathetic function. A substantial proportion of subjects exposed to microgravity develop transient orthostatic intolerance. It has been proposed that alterations in baroreflex function play a role in the orthostatic intolerance induced by microgravity. The evidence in favor and against this hypothesis is reviewed.     

Clinical presentation and management strategies of cardiovascular autonomic dysfunction following a COVID-19 infection – A systematic review

Background

Cardiovascular autonomic dysfunction may reportedly occur after a coronavirus-disease-2019 (COVID-19) infection, but the available evidence is scattered. Here we sought to understand the acute and mid-term effects of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection on cardiovascular autonomic function.

Methods

We performed a systematic PubMed, Embase, Web of Science, medRxiv, and bioRxiv search for cases of cardiovascular autonomic dysfunction during an acute SARS-CoV-2 infection or post-COVID-19 condition. The clinical-demographic characteristics of individuals in the acute versus post-COVID-19 phase were compared.

Results

We screened 6470 titles and abstracts. Fifty-four full-length articles were included in the data synthesis. One-hundred and thirty-four cases were identified: 81 during the acute SARS-CoV-2 infection (24 thereof diagnosed by history) and 53 in the post-COVID-19 phase. Post-COVID-19 cases were younger than those with cardiovascular autonomic disturbances in the acute SARS-CoV-2 phase (42 vs. 51 years old, p = 0.002) and were more frequently women (68% vs. 49%, p = 0.034). Reflex syncope was the most common cardiovascular autonomic disorder in the acute phase (p = 0.008) and postural orthostatic tachycardia syndrome (POTS) the most frequent diagnosis in individuals with post-COVID-19 orthostatic complaints (p < 0.001). Full recovery was more frequent in individuals with acute versus post-COVID-19 onset of cardiovascular autonomic disturbances (43% vs. 15%, p = 0.002).

Conclusions

There is evidence from the scientific literature about different types of cardiovascular autonomic dysfunction developing during and after COVID-19. More data about the prevalence of autonomic disorders associated with a SARS-CoV-2 infection are needed to quantify its impact on human health.     

What is the minimum duration of head-up tilt necessary to detect orthostatic hypotension?

Abstract Objective There is uncertainty as to the minimum duration of head-up tilt (HUT) needed to detect orthostatic hypotension (OH). The orthostatic duration has variably been recommended to be 1, 2, 3, and 5 minutes. The purpose of the current study was 1) to determine the minimum duration of HUT necessary to detect OH and 2) to identify different patterns of orthostatic blood pressure (BP) response in patients with OH. Design/methods We evaluated the medical records of 66 consecutive patients (mean age 70.0±10.1 years; 64% male) seen at Mayo Clinic-Rochester from 2000–2001 who fulfilled the criteria for OH (systolic blood pressure [SBP] reduction 20mm Hg within 3 minutes of HUT) during routine clinical autonomic studies. All patients completed an autonomic reflex screen with continuous monitoring of heart rate and BP during supine rest and 5 minutes of 70 degree HUT. Severity of autonomic deficits was quantified with the Composite Autonomic Severity Score (CASS). Results Overall, BP was the lowest at 1 minute with gradual and partial recovery over the following 4 minutes. Eighty-eight percent of patients (N=58) developed OH by 1 minute of HUT, with an additional 11% (N=7) developing OH by 2 minutes and the remaining 1% (N=1) developing OH by 3 minutes. We identified two broad patterns of SBP response to HUT. Forty-eight percent (N=32) of patients demonstrated an initial drop in SBP ( 20 mm Hg),which remained stable until tilt-back. Thirty-six percent (N=24) demonstrated an initial drop ( 20mm Hg) followed by a progressive decline in SBP until tilt-back. Repeated measures analysis of variance confirmed that the SBP change in response to HUT differed significantly among patients with a stable vs. progressive pattern [F(3,32)=25.1, p<0.001). Patients with the progressive pattern also had more severe adrenergic impairment on the CASS (p=0.03) and were more likely to have their tilt test terminated early (prior to 5minutes) due to presyncope (p<0.0001) than patients with the stable pattern. Conclusions One minute of HUT will detect OH in the great majority (88%) of patients and three minutes will detect the balance. Orthostatic stress beyond 2 minutes is necessary to detect the pattern of progressive OH. Since this group has more severe adrenergic deficits than the group with stable OH, we suggest that the progressive pattern is due to greater impairment of compensatory reflexes. Recognition of the group with progressive fall in BP is important since this group may be at greater risk of orthostatic syncope.     

Early versus late postural tachycardia: a re-evaluation of a syndrome

Postural tachycardia syndrome (POTS) involves an HR-rise within 10 minutes of head-up tilt. Hypokinetic circulation, older age, and ACE-inhibitor or Angiotensin-Receptor Blockers were associated with "Late" POTS (after 10 minutes of tilt) versus "Early" POTS (within 10 minutes of tilt).     

Pyridostigmine for treatment of neurogenic orthostatic hypertension

Abstract We report the result of a follow-up, open-label study of pyridostigmine for treatment of orthostatic hypotension. Aim of the study was to evaluate self-reported efficacy and patients satisfaction with the medication. Most patients were very satisfied with the medication and chose to continue it.This study was supported in part from grants from the National Institutes of Health, Bethesda, MD: 5 K23 RR15537 (Dr. Sandroni), NS3 2352, NS4 4233 NS4 3364 (Dr. Low), and Mayo GCRC grant M01-RR00585     

The role of delayed orthostatic hypotension in the pathogenesis of chronic fatigue

Past studies have shown that severe fatigue was the presenting symptom in six of seven patients with delayed orthostatic hypotension and that tilt table-induced hypotension was found in 22 of 23 patients with the chronic fatigue syndrome. We have determined the prevalence of fatigue, volunteered in response to a nonspecific pre-examination questionnaire used in 431 patients, each subsequently diagnosed as having one of eight neurological or endocrine disorders. The results show that fatigue is a very common symptom in patients with delayed orthostatic hypotension (n=21), as well as both primary (n=30) and secondary (n=106) hypocortisolism: 70–83% in all groups. In contrast, fatigue was an uncommon complaint in patients with multiple system atrophy (MSA) (n=30), pituitary dosorders without hypocortisolism (n=106) or idiopathic hirsutism (n=96): 7–33% in all groups, and was intermediate in prevalence in patients with acute hyperadrenergic orthostatic hypotension (n=32): 41%. It is concluded that fatigue commonly results from delayed orthostatic hypotension and all forms of hypocortisolism but is less common in patients with acute orthostatic hypotension, both idiopathic and due to MSA, which more commonly present with lightheadedness or syncope.     

Bilateral TIAs and unilateral seizures due to orthostatic hypotension. A case report

After a reversible right hemispheric stroke, a patient with bilateral carotid occlusion developed left motor seizures and bilateral TIAs, both triggered by orthostatic hypotension. A CT-scan showed a right frontal hypodense area. Hemodynamic factors may cause focal seizures in patients with cortical lesions.

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Riassunto Dopo un attacco ischemico reversibile in emisfero destro, un paziente con occlusione carotidea bilaterale presentò crisi epilettiche focali motorie agli arti di sinistra e TIA bilaterali, entrambi scatenati da ipotensione ortostatica. Una TAC dimostrò un 'area ipodensa frontale destra. Fattori emodinamici possono provocare crisi epilettiche focali in pazienti con lesioni corticali.

     

Impact of the COVID-19 pandemic on clinical autonomic practice in Europe: a survey of the European Academy of Neurology and the European Federation of Autonomic Societies

Background and purpose

The objective was to investigate the impact of the coronavirus disease 2019 (COVID-19) pandemic on European clinical autonomic practice.

Methods

Eighty-four neurology-driven or interdisciplinary autonomic centers in 22 European countries were invited to fill in a web-based survey between September and November 2021.

Results

Forty-six centers completed the survey (55%). During the first pandemic year, the number of performed tilt-table tests, autonomic outpatient and inpatient visits decreased respectively by 50%, 45% and 53%, and every third center reported major adverse events due to postponed examinations or visits. The most frequent newly diagnosed or worsened cardiovascular autonomic disorders after COVID-19 infection included postural orthostatic tachycardia syndrome, orthostatic hypotension and recurrent vasovagal syncope, deemed to be likely related to the infection by ≥50% of the responders. Forty-seven percent of the responders also reported about people with new onset of orthostatic intolerance but negative tilt-table findings, and 16% about people with psychogenic pseudosyncope after COVID-19. Most patients were treated non-pharmacologically and symptomatic recovery at follow-up was observed in ≥45% of cases. By contrast, low frequencies of newly diagnosed cardiovascular autonomic disorders following COVID-19 vaccination were reported, most frequently postural orthostatic tachycardia syndrome and recurrent vasovagal syncope, and most of the responders judged a causal association unlikely. Non-pharmacological measures were the preferred treatment choice, with 50%–100% recovery rates at follow-up.

Conclusions

Cardiovascular autonomic disorders may develop or worsen following a COVID-19 infection, whilst the association with COVID-19 vaccines remains controversial. Despite the severe pandemic impact on European clinical autonomic practice, a specialized diagnostic work-up was pivotal to identify non-autonomic disorders in people with post-COVID-19 orthostatic complaints.     

帕金森病患者体位性低血压及餐后低血压的相关危险因素

目的 探讨帕金森病(PD)患者体位性低血压(0H)和餐后低血压(PPH)的相关危险因素.方法 对55例原发性PD患者(PD组)和35例健康对照者(正常对照组)进行清醒后、早餐前15 min和早餐后60 min卧位和直立位血压的测量,以及PD自主神经症状量表(SCOPA-AUT)评分,并对结果进行比较.分析OH和PPH的相关危险因素.结果 PD组餐后立位收缩压及舒张压显著低于正常对照组(均P＜0.01);OH、PPH发生率及SCOPA-AUT总分和各项评分均显著高于正常对照组(均P＜0.01).PD患者OH与左旋多巴等效剂量换算呈正相关(P ＜0.05);PPH与PD病程及OH呈正相关,与SCOPA-AUT中瞳孔调节分数呈负相关(均P＜0.05).结论 PD患者OH和PPH的发生率高.抗PD药物剂量大是PD患者OH发生的危险因素.病程长、OH及瞳孔副交感神经功能损害是发生PPH的危险因素.     

Vasomotor reactivity as a predictor for syncope in patients with orthostatism

Gur AY, Auriel E, Korczyn AD, Gadoth A, Shopin L, Giladi N, Bornstein NM, Gurevich T. Vasomotor reactivity as a predictor for syncope in patients with orthostatism.
Acta Neurol Scand: 2012: 126: 32–36.
© 2011 John Wiley & Sons A/S. Objectives – Syncope in patients with orthostatic hypotension (OH) may be the result of impaired cerebral autoregulation. Cerebral autoregulation status can be determined by assessing cerebral vasomotor reactivity (VMR). We assessed and compared VMR in patients with OH with and without syncope. Material and methods – Twenty‐nine patients with OH underwent transcranial Doppler (TCD) and the Diamox test (1 g acetazolamide IV) for assessing VMR during elaboration of their OH syndrome. The percent difference between cerebral blood flow velocities (BFV) in the middle cerebral (MCA) and vertebral (VA) arteries before and after acetazolamide was defined as VMR%. We considered increases of BFV of ≥40% as being indicative of good VMR and classified our study patients as having good or impaired VMRs accordingly. Results – Mean VMR% values of the MCA and VA in patients with OH with syncope (n = 12) were significantly lower as compared with patients with OH without syncope (n = 17): 25.2 ± 20.5% and 42.5 ± 18.6%; 20.9 ± 15.5% and 40.8 ± 28.5%, respectively (P < 0.05). Conclusions – Among patients with OH, we found an association between the presence of syncope and impaired VMR. Assessment of VMR among patients with OH may predict those who are at higher risk to faint and fall and to support more aggressive intervention.     

Fainting in animals

Fainting (syncope) is unconsciousness due to insufficient cerebral circulation in the context of a temporary failure of the systemic circulation. This paper firstly aims to discuss fainting in animals, and secondly to discuss animal physiology to broaden the understanding of human fainting.Of the three major syncope types (cardiac, orthostatic and reflex syncope), only cardiac syncope occurs in animals as in man, through arrhythmia or output failure.Mans orthostatic fainting tendency has been blamed on his upright posture. A comparison with animals shows that giraffes, treeclimbing snakes, and animals that quickly raise and lower their heads face more serious gravitational circulatory challenges than man, but do not appear to faint. Merely carrying the brain above the heart does not explain a fainting tendency, as the human heart-to-brain height is smaller than that of many mammals with similar blood pressure. Two evolutionary novelties may be to blame: the proportion of cardiac output going upwards to the brain is much larger than in apes, and mans large legs suggest that the volume lost to venous pooling is also larger.Emotional factors play a role in many reflex syncope events. Tonic immobility (feigning death,playing possum) is not a good model, as it concerns immobility as a survival strategy of an attentive brain, rather than unconsciousness due to circulatory breakdown. Whether orienting and defense responses form a valid model remains to be proven. Emotional fainting may be uniquely human; how mental processes can shut down the circulation and thereby the brain needs serious study, as it may hold the key to syncope prevention.     

The tilting cardiovascular response in orthostatic syncope

159 patients with a previous discharge diagnosis of recurrent vasodepressor syncope associated with prolonged standing or other circumstance known to trigger the condition were examined in order to isolate the orthostatic form. 72 patients with a history of at least two episodes of loss of consciousness after standing still for at least 10' were selected for testing by head-up tilt. Those who showed signs or symptoms during the test were tested a further twice, the third time after atropine administration. This process resulted in the diagnosis of orthostatic vasodepressor syncope in 28 patients who presented both 1) a positive test associated with hypotension and bradycardia and 2) bradycardia-free hypotention on repetition of the test with atropine.

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Sommario Abbiamo studiato 159 pazienti diagnosticati come affetti da sincope vasodepressiva associata a differenti condizioni ed in particolare anche alla prolungata stazione eretta. Fra questi ne selezionammo 72 che nell'anamnesi presentavano almeno due episodi di perdita di coscienza in ortostatismo. 71 soggetti, paragonabili per sesso ed età, costituirono il gruppo di controllo. I 143 pazienti così individuati furono sottoposti a tilting: quelli positivi lo ripeterono altre due volte, l'ultima con contemporanea somministrazione di atropina.Questo iter diagnostico portò alla diagnosi di sincope ortostatica vasodepressiva in 28 soggetti che presentarono: 1) la positività del test associata a ipotensione e bradicardia, 2) una ipotensione senza bradicardia durante la ripetizione del test con atropina.Infine fu possibile identificare due piccoli sottogruppi di pazienti che manifestarono durante il test asistolia (2 pazienti) e ipotensione associata a tachicardia (sincope simpatotonica, 3 casi) per i quali sono indicati provvedimenti terapeutici differenziati.

     

Acute haemodynamic response to sleeping head-up at 6 inches in older inpatients

Objective  Our aim was to investigate the effect of monotherapy of sleeping head-up (SHU) at 6 in. in a group of older inpatients with OH from all causes. Methods  We recruited nine consecutive inpatients (mean age (SD) 76(5) years) with persistent, symptomatic OH with a mean systolic blood pressure (SBP) drop on standing and nadir SBP of 68 (27.8) and 94 (19.2) mmHg respectively. All patients underwent SHU for 1 week. Beat-to-beat haemodynamics during lying and standing, 24-hour ambulatory blood pressure, supine haematocrit, urea/electrolytes, plasma renin activity and aldosterone were measured before and after intervention. Results  One week after SHU, SBP, stroke volume and cardiac output increased significantly (all P < 0.05) by 12 mmHg, 15 ml and 1.3 l/minutes respectively while heart rate and total peripheral resistance were significantly reduced by 3.6 bpm and 0.355 dynes/s/cm⁵ respectively during 2 minute of standing. Serum creatinine was also significantly lower. Five patients improved in their mobility following SHU. Interpretations  SHU for 1 week at 6 in. was well tolerated by older in-patients with OH, associated with improved orthostatic tolerance, and with haemodynamic changes in keeping with increased extracellular volume. SHU at 6 in. has a role in the acute treatment of OH for patients in hospital, but its longer-term effects and in the out-patient setting require further study. Electronic supplementary material  The online version of this article (doi: ) contains supplementary material, which is available to authorized users. Clinical trial registration information: Not a clinical trial.     

Phase of the menstrual cycle does not affect orthostatic tolerance in healthy women

Abstract Women of child-bearing age have a lower orthostatic tolerance (OT) than older women or men, and women suffering from frequent syncopal episodes often comment that their symptoms occur at certain times of the menstrual cycle. However, it is not known whether, in asymptomatic women, OT varies at different phases of the menstrual cycle. We studied 8 healthy asymptomatic women aged 26.8±3.4 years. We determined OT using a test of combined head-up tilting and lower body suction. We continuously monitored beat-to-beat blood pressure (Finapres), heart rate (ECG), and cerebral and forearm blood flow velocities (Doppler ultrasound). On each test day we assessed carotid baroreceptor sensitivity from suction/pressure applied to a neck chamber. We also determined estradiol and progesterone levels from a venous blood sample. Tests were performed in early follicular and late luteal phases, and during ovulation. Serum concentrations of estradiol (pmol • l^–1) and progesterone (nmol • l^–1) were in follicular phase 464.1 ± 63 and 6.3 ± 2.8; ovulation 941.6 ± 298 and 5.8 ± 1.2; luteal phase 698±188 and 32.3 ± 9.6. Progesterone levels were significantly higher in the luteal phase (p < 0.001). OT was not different on any test day: follicular 31.9 ± 1.6 min, ovulation 31.3 ± 0.7 min; luteal 31.1 ± 2.2 min. Supine and tilted heart rates and blood pressures, the maximum heart rate, and the cerebral autoregulatory and forearm vascular resistance responses to the orthostatic stress were similar during all studies. Both cardiac and vascular resistance carotid baroreceptor sensitivities were also similar on all test days. These results suggest that there is no difference in either OT or cardiovascular control at the tested phases of the menstrual cycle in healthy women.     

Cardiovascular variables do not predict head-up tilt test outcome better than body composition

Reflex syncope is a well-recognized phenomenon, but the understanding of its underlying pathophysiology remains limited. We hypothesized that patients with a history of syncope and a positive head-up tilt test (HUTT) outcome are in a “not-yet defined” abnormal state even before the head-up position. We performed a 45 min HUTT on 86 patients with a history of syncope. We assessed 19 variables during the supine period before head-up position. Of these variables, 9 were cardiovascular variables (CV) while 8 were body composition variables (BC). The two remaining variables were age and sex. Forty-five patients (41 ± 15 years, 22 males) have a positive HUTT outcome and 41 a negative one (46 ± 15 years, 22 males). Statistical tests applied on each of the 19 variables individually did not discriminate patients with a positive and a negative outcome. We used neural networks to screen the sets of variables that allowed for the best predictions of HUTT outcomes. The sensitivity, specificity, positive and negative predictive values (PPV and NPV, respectively) were determined. The best set of predictive values determined from the 19 variables was 76, 81, 78 and 80% for sensitivity, sensibility, PPV, and NPV, respectively. Unexpectedly, the HUTT outcome prediction performed with cardiovascular variables was not better than the prediction performed with body composition variables only. Patients with a positive HUTT outcome are in an abnormal state that can be detected even before the head-up position. Body composition is an important contributor to this abnormal state.