Head-up Tilt Test Research Articles

Coefficient of variation of heart rate and blood pressure in rapid identification of children with suspected orthostatic intolerance

Objective: To investigate the clinical value of coefficient of variation of heart rate and blood pressure in rapid identification of children with suspected orthostatic intolerance(OI). Methods: This was a retrospective study. The medical records of 379 children with OI were collected, who were admitted to the Department of Pediatrics of Qilu Hospital of Shandong University from January 2015 to January 2020. Another 20 out-patient children without syncope or syncope aura were selected as control. According to the results of standing test and head-up tilt test (HUTT), all the patients with OI were divided into the following 4 groups: vasovagal syncope (VVS) group, postural tachycardia syndrome (POTS) group, POTS combined with VVS (POTS+VVS) group and HUTT negative group. Then, coefficient of variation of systolic pressure (SBPCV), coefficient of variation of diastolic pressure (DBPCV) and coefficient of variation of heart rate (HRCV) in standing test and HUTT were calculated. Kruskal-Wallis test was used for comparison among the five groups, and Dunnett's T3 method for comparison between two groups. Paired t test was used to compare the coefficient of variation between supine and erect position and tilt position in each group. The predictive values of HRCV,SBPCV and DBPCV for negative HUTT were evaluated by receiver operating characteristic (ROC) curve. Results: Among the 379 children, there were 79 in HUTT negative group, 208 in VVS group, 52 in POTS group, and 40 in POTS+VVS group. The SBPCV of supine-erect position of the control group, HUTT negative group, VVS group, POTS group, POTS+VVS group were (3.8±1.0)%, (5.3±2.2)%, (6.6±3.4)%, (5.9±3.6)%, (6.9±2.8)%, respectively. Similarly, the SBPCV of supine, erect and head-up tilt position were (4.5±0.8)%, (6.0±1.9)%, (7.1±2.6)%, (6.0±2.1)%, (7.3±2.5)%; the DBPCV of supine-erect position were (7.3±1.2)%, (9.1±3.7)%, (9.1±4.9)%, (9.1±4.8)%, (11.6±4.6)%; the DBPCV of supine, erect and tilt position were (7.4±1.1)%, (9.4±2.9)%, (10.1±3.8)%, (9.2±3.3)%, (11.0±4.7)%; the HRCV of supine-erect position were (7.6±2.6)%, (12.9±3.7)%, (16.2±4.3)%, (21.2±5.9)%, (24.9±5.3)%; and the HRCV of supine, erect and tilt position were (8.1±1.6)%, (10.1±2.7)%, (14.1±4.3)%, (15.6±3.7)%, (18.9±4.0)%, respectively. All the indexes showed significant differences among the five groups (χ2=21.91, 25.47, 19.82, 14.65, 104.52, 92.51, all P<0.05). ROC curve analysis showed that when the SBPCV and HRCV of supine-erect position reached 4.4% and 10.5%, the area under the curve of ROC were 0.713 and 0.877, the sensitivity of predicting negative HUTT were 58.2% and 78.5%, and the specificity were 80.0% and 95.0%, respectively. Conclusions: Coefficient of variation of heart rate and blood pressure may serve as potential diagnostic indexes in evaluating autonomic function of OI patients. SBPCV ≥ 4.4% or HRCV ≥ 10.5% of supine-erect position could be an indication of HUTT.

Vasoactive Biomarkers in Patients With Vasovagal Syncope During Head-Up Tilt Test: A Case-Control Study.

Background:Vasovagal syncope (VVS) is the most common cause of syncope. Some stages of its pathophysiological mechanisms remain unclear. Vasoactive substances such as nitric oxide metabolites (NOx) and endothelin (ET) may be involved during acute orthostatic stress.Objective:To analyze plasma changes in NOx and ET and heart rate variability (HRV) in the supine positions (T1) and during the head-up tilt test (HUTT) (T2), in patients with VVS (case group) and control group.Methods:Thirty-seven patients (17 in the case group and 20 in the control group), matched for age and sex (mean aged 31.8 years) underwent HUTT with simultaneous HRV recording and venipuncture. Blood samples were collected during phases T1 and T2 and the analysis was performed without knowledge of the HUTT result.Results:In the total sample, there was an increase in NOx values (P = .014), however there was no increase in ET values from phase T1 to phase T2. Patients with VVS tended to increase plasma NOx values (P = .057) and had significantly higher plasma values compared to ET (P = .033) between phases T1 to T2. In the control group, there was no significant change in the values of these vasoactive substances. Regarding HRV, there were a decrease in the component HF (high frequency) and increased of the LF (low frequency)/HF ratio during HUTT.Conclusions:There was an increase in ET during HUTT occurred only in the case group. These patients are more likely to have an imbalance between antagonistic vasoactive biomarkers during orthostatic stress.

Minimal Vasovagal Dysautonomia in Patients with Rare or Unique Syncope

Introduction: It is common to find people sent to perform a Head Up Tilt Test (HUT) who suffered a single syncope, or syncopes that occur during certain periods and never appear again. We wonder how these people are different from those who have never had syncope. Methods: We found 300 patients who suffered only one (unique) or a maximum of 5 vasovagal syncopes during their life. And their HUT was positive for vasovagal dysautonomia. We compared them, with 120 healthy volunteers who have never had syncope. We try to explain how some constitutional predisposing factors act in these patients, and are associated with environmental triggers to precipitate the syncope. Results: We found differences between cases and controls in predisposing factors such as: heredity, joint hypermobility, baroreflex failure, venous compliance and some neurological diseases. Then an environmental factor acts as a trigger for syncope: prolonged standing, stress, pain and emotions, dehydration, use of certain drugs, abundant food. Conclusions: There are people with minimally expressed vasovagal dysautonomia who have an organic predisposition to present vasovagal syncopes (heredity, joint hypermobility, baroreflex failure, venous compliance, some neurological diseases, etc.). But this predisposition is not enough by itself to produce syncopes. One or more environmental factors must be added, acting as a trigger that would be the reason why these episodes are so infrequent.

Defecation Syncope; Digging Deep: A Case Report

Defecation syncope explains the exaggerated vasovagal response while defecating, which may result in unconsciousness and rarely cardiac arrest. It is underreported, mainly because of the patient's hesitation and inability to correlate the two, unless specifically probed by meticulous history taking; the importance of which cannot be over-emphasized. A 28- year old fieldworker with two episodes of syncope, the last of which culminated in a cardiac arrest requiring resuscitation by a bystander. Upon further questioning, it was revealed that both times, the patient had the urge to defecate followed by dizziness and warmth preceding the loss of consciousness. A head-up tilt table test was planned as a means to reenact the symptoms. Upon confirmation of diagnosis, the patient was counselled for lifestyle changes only. Defecation syncope leading to cardiac arrest is a rare entity but with high mortality ratio. Since vagal tone increases during straining effort, reducing physiological response may be helpful to avoid lethal results. Hydration, avoidance of constipation, and squatting position are among the important key risk-reducing factors.

Syncope and the aging patient: Navigating the challenges.

Syncope in the elderly patient is a common presentation and the most common causes are usually non-cardiac. Older adults however are more challenging dilemmas as their presentation is complicated by co-morbidities, mainly cardiovascular and neurodegenerative disorders. Frailty and cognitive impairment add to the ambiguity of the presentation, and polypharmacy is often a major modifiable contributing factor. Vasovagal syncope is a common presentation throughout life even as we age. It has a favorable prognosis and conservative management usually suffices. Vasovagal syncope in this population may be misdiagnosed as accidental falls and is frequently associated with injury, as is carotid sinus syndrome. The initial approach to these patients entails a detailed history and physical examination including a comprehensive medication history, orthostatic vital signs, and a 12-lead electrocardiogram. Further cardiac and neuroimaging rarely helps, unless directed by specific clinical findings. Head-up tilt testing and carotid sinus massage retain their diagnostic accuracy and safety in the elderly, and implantable loop recorders provide important information in many elderly patients with unexplained falls and syncope. The starting point in management of this population with non-cardiac syncope is attempting to withdraw unnecessary vasoactive and psychotropic medications. Non-pharmacologic and pharmacologic therapy for syncope in the elderly has limited efficacy and safety concerns. In selected patients, pacemaker therapy might offer symptomatic relief despite lack of efficacy when vasodepression is prominent. An approach focused on primary care with targeted specialist referral seems a safe and effective strategy.

Establishment of Normative Data for Autonomic Function Tests in Indian Population.

Background:Normative data for autonomic function tests (AFT) is not available for Indian population.Objective:The aim of the study was to establish normative data in AFT and its correlation with age, gender, and body mass index.Material and Methods:The study was done on 254 healthy subjects of age ≥18 years. All AFTs were done in autonomic laboratory at the Department of Neurology, Christian Medical College and Hospital, Ludhiana. Cardiovascular tests (heart rate response to deep breathing, HR changes in Valsalva maneuver and head-up tilt test (HUT)) and quantitative sudomotor axon reflex testing (QSART) were performed in all the subjects. Fifty subjects underwent thermoregulatory sweat test (TST).Results:The mean age (SD) of study participants was 43 (16.0) years (range 20–84), and 129 (50.8%) were men. The normative value range (2.5–97.5 percentile) for HR difference, E: I ratio, and Valsalva ratio (VR) was 3.5–47.0, 1.05–1.93, and 1.11–2.64, respectively, for all the subjects. HR difference and E: I ratio showed an significant inverse relation with age (r = -0.623 and r = -0.584, respectively). VR also showed an inverse relation with age (r = -0.575, P =< 0.001), and female had a lower value than male (1.63 vs 1.78, P =< 0.001). In QSART, mean (SD) sweat volume was higher in males 0.630 (0.230) compared to females 0.513 (0.132) for all sites, P < 0.001, and similar trend was noticed for sweat area in TST.Discussion and Conclusion:Normative AFT data has been established for Indian population for the first time. The values are comparable to previously published studies.

Compression Stockings Improve Cardiac Output and Cerebral Blood Flow during Tilt Testing in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) Patients: A Randomized Crossover Trial.

Background and Objectives: Orthostatic intolerance (OI) is a clinical condition in which symptoms worsen upon assuming and maintaining upright posture and are ameliorated by recumbency. OI has a high prevalence in patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Limited data are available to guide the treatment of OI in ME/CFS patients. We and others have previously described patient-reported subjective improvement in symptoms using compression stockings. We hypothesized that these subjective reports would be accompanied by objective hemodynamic improvements. Materials and Methods: We performed a randomized crossover trial in 16 ME/CFS patients. Each underwent two 15-min head-up tilt table tests, one with and one without wearing knee-high compression stockings that provided 20–25 mm Hg compression. The order of the tests was randomized. We measured heart rate and blood pressure as well as cardiac output and cerebral blood flow (CBF) using extracranial Doppler of the internal carotid and vertebral arteries. Results: There were no differences in supine measurements between the 2 baseline measurements. There were no differences in heart rate and blood pressure at either end-tilt testing period. Compared to the test with the stockings off, the mean percentage reduction in cardiac output during the test with compression stockings on was lower, 15 (4)% versus 27 (6)% (p < 0.0001), as was the mean percentage CBF reduction, 14 (4)% versus 25 (5)% (p < 0.0001). Conclusion: In ME/CFS patients with orthostatic intolerance symptoms, cardiac output and CBF are significantly reduced during a tilt test. These abnormalities were present without demonstrable heart rate and blood pressure changes and were ameliorated by the use of compression stockings.

Clinician needs and perceptions about cardioneuroablation for recurrent vasovagal syncope: An international clinician survey.

Cardioneuroablation (CNA) targets the intrinsic cardiac autonomic nervous system ganglionated plexi located in the peri-atrial epicardial fat. There is increasing interest in CNA as a treatment of vasovagal syncope (VVS), despite no randomized clinical trial (RCT) data. The purpose of this study was to poll the opinion on CNA) for VVS. A REDCap (Research Electronic Data Capture) survey was administered to international physicians treating patients with VVS on their opinion about patient selection criteria, ablation approach, RCT design, and most appropriate end points for CNA procedures. The survey was completed by 118 physicians; 86% were cardiac electrophysiologists. The majority of respondents (79%) would consider referring a patient with refractory VVS for CNA, and 27% have performed CNA for VVS themselves. Most felt patient selection should require a head-up tilt test with a cardioinhibitory response (67%) and suggest a minimum age of 18 years with a median of 3 (interquartile range 2-5) episodes in the past year. There were differences in patient selection between physicians who have performed CNA themselves and those who have not. The majority felt that the ablation strategy should include both atria (70%) with an anatomical approach in combination with autonomic stimulation (85%). Performing a sham procedure in the control arm was supported by 56% of respondents, providing equipoise in RCT design. The preferred primary outcome was freedom from syncope within 1 year of follow-up. There is widespread support for well-designed RCTs to confirm the hypothesized clinical benefit of CNA, provide data to guide the risk-benefit equations during patient selection, and appropriately estimate the placebo effect.

Prognostic Value of Biomarkers in Children and Adolescents With Orthostatic Intolerance.

Orthostatic intolerance (OI) refers to a series of symptoms that occur during upright standing, which can be relieved when returned to the supine position. OI is a common cause of syncope in children and adolescents. In recent years, more and more studies have been carried out to assess the prognosis of OI by using biomarkers, among which, flow-mediated vasodilation, left ventricular ejection fraction and fractional shortening, hemodynamic change during head-up tilt test, detection of 24-h urinary sodium excretion, body mass index, midregional pro-adrenomedullin, and erythrocytic H2S producing rate are relatively stable, inexpensive, and easy to obtain. With the help of biomarkers, individualized treatment can be carried out to improve the long-term prognosis of children and adolescents with OI. This article reviews the prognostic value of biomarkers in children and adolescents with OI.

Comparison of cortisol levels in patients with vasovagal syncope and postural tachycardia syndrome.

ABSTRACTObjectives:To compare the levels of cortisol in patients of vasovagal syncope (VVS) and postural tachycardia syndrome (POTS).Methods:A cross-sectional analytical study was conducted at Islamic International Medical College, Rawalpindi and Electrophysiology Department at (AFIC). This study included 80 subjects, comprising of 35 patients in each group of vasovagal syncope and postural tachycardia syndrome and 10 healthy subjects. Patients with complaint of syncope was evaluated for vasovagal syncope and postural tachycardia syndrome using Head Up Tilt Test (HUTT. Blood samples of all the participants were taken and serum cortisol was analyzed using ELISA method. Results were analyzed on SPSS Statistics 21 using ANOVA with a p value of ≤0.05 regarded as significant.Results:Hormonal analysis shows that cortisol levels in the vasovagal, postural tachycardia syndrome and in control group was 153±16.7pg/ml, 160.17±pg/ml, and 69.65± 5.8pg/ml respectively. Cortisol levels were significantly higher in both vasovagal and POTS groups as compared to controls with a p-value of 0.04 and 0.023 respectively. However, there was no significant difference between vasovagal and POTS patients with p value 0.570.Conclusion:It is concluded from the study that cortisol responses of VVS and POTS were positive.

Cerebral Autoregulation during Orthostatic Challenge in Congenital Central Hypoventilation Syndrome.

Rationale: Congenital central hypoventilation syndrome (CCHS) is a rare autonomic disorder with altered regulation of breathing, heart rate (HR), and blood pressure (BP). Aberrant cerebral oxygenation in response to hypercapnia/hypoxia in CCHS raises the concern that altered cerebral autoregulation may contribute to CCHS-related, variably impaired neurodevelopment. Objectives: To evaluate cerebral autoregulation in response to orthostatic challenge in CCHS cases versus controls. Methods: CCHS and age- and sex-matched control subjects were studied with head-up tilt (HUT) testing to induce orthostatic stress. Fifty CCHS and 100 control HUT recordings were included. HR, BP, and cerebral oxygen saturation (regional oxygen saturation) were continuously monitored. The cerebral oximetry index (COx), a real-time measure of cerebral autoregulation based on these measures, was calculated. Measurements and Main Results: HUT resulted in a greater mean BP decrease from baseline in CCHS versus controls (11% vs. 6%; P < 0.05) and a diminished increase in HR in CCHS versus controls (11% vs. 18%; P < 0.01) in the 5 minutes after tilt-up. Despite a similar COx at baseline, orthostatic provocation within 5 minutes of tilt-up caused a 50% greater increase in COx (P < 0.01) and a 29% increase in minutes of impaired autoregulation (P < 0.02) in CCHS versus controls (4.0 vs. 3.1 min). Conclusions: Cerebral autoregulatory mechanisms appear to be intact in CCHS, but the greater hypotension observed in CCHS consequent to orthostatic provocation is associated with greater values of COx/impaired autoregulation when BP is below the lower limits of autoregulation. Effects of repeated orthostatic challenges in everyday living in CCHS necessitate further study to determine their influence on neurodevelopmental disease burden.

Abstract 11329: Prospective Analysis of Vascular Resistance in Patients with Persistent Tachycardia and or Dyspnea on Exertion in the Post Acute Sequela of Covid-19 Syndrome

Introduction: The cause of tachycardia and dyspnea on exertion (DOE) in the Post Acute Sequelae CoV-2 syndrome (PASC) has yet to be identified. While endothelial invasion of the virus is well documented, how that might explain PASC is unknown. Hypothesis: Covid induced changes in vascular signaling to autonomic regulatory centers can induce sinus tachycardia and DOE. Methods: In a prospective, observational study, we enrolled 18 PASC patients who reported DOE or inappropriate tachycardia. All patients had normal left ventricular function, CXR, Hgb and thyroid studies. None had preexisting autonomic dysfunction. Vascular resistance was assessed by echocardiographic measurement of aortic-vascular impedance (Zva)=(systolic BP + mean Ao valve gradient)/stroke volume index. Ambulatory heart rate monitoring and head-up tilt table testing (HUTT) were performed. Results: Consecutively enrolled patients (18) were studied (17 females, ages 27 to 64). None had a significant aortic valve gradient. Zva was elevated in 17 of 18 patients. Ambulatory monitoring revealed episodes of symptomatic sinus tachycardia. Higher average daily heart rates correlated significantly with higher Zva levels (fig1). The 14 patients with DOE trended to higher average Zva levels than the 4 patients without dyspnea (4.13 +- 0.85 vs 3.5 +- 0.24, P=0.14). Of the 17 patients who had HUTT, 16 demonstrated patterns of orthostatic intolerance consistent with excess sympathetic tone including both postural orthostatic tachycardia and neurogenic cardiac syncope. Conclusions: PASC associated sinus tachycardia and HUTT abnormalities result from excess sympathetic tone. Covid-19 vascular injury as evidenced by abnormal Zva values may result in abnormal vascular signaling to autonomic regulatory centers. Resultant increases in sympathetic output may produce inappropriate sinus tachycardia, vasomotor dysregulation and DOE via peripheral vasoconstriction.

Autonomic Dysfunction among Migraineurs with and without Complaints of Orthostatic Intolerance: Evidence for Small Fiber Nerve Damage

Background and Objective: Migraineurs often complain of orthostatic intolerance (OI), and its recognition is vital to appropriate treatment. This study attempts to identify and characterize autonomic dysfunction, comparing a sample of migraineurs with OI with a sample of migraineurs without OI. Methods: In a prospective cohort study, we examined one migraine sample complaining of OI for &gt; 6 months (Group 1) and another group without OI (Group 2), using a 70-degree, 45-minute head-up passive tilt-table (HUT45) test, electrocardiographic R-R interval measurements during deep breathing, blood pressure and heart rate monitoring during Valsalva and release, QSART, and skin biopsy for nerve fiber density. We compared results with standard, 10-minute head-up passive tilt-table (HUT10) results to determine which test promoted greater sensitivity, specificity and diagnostic accuracy. Descriptive statistics were computed for each group, defined by the presence or absence of OI. We conducted several receiver operating characteristic analyses to determine whether certain clinical characteristics were predictive of symptoms of OI. Results: Thirty-nine Group 1 and 22 Group 2 subjects were studied and were similar demographically. Thirty eight of 39 (97.4%) Group 1, versus 15/22 (68.2%) Group 2 subjects, manifested abnormal HUT45 results, a significant difference (p=0.002). The HUT45 showed higher sensitivity (0.59; 95% CI: 0.42-0.74) than the standard 10-minute tilt-table test (HUT10) for all expressions of OI (0.31; 95% CI: 0.17-0.48). No differences in autonomic laboratory or skin biopsy findings distinguished the groups. We detected biopsy-proven small fiber neuropathy in 22/39 (56.4%) Group 1 and 10/22 (45.5%) Group 2 subjects. Discussion and Conclusions: In migraineurs, OI is an expression of autonomic dysfunction. We found evidence for a peripheral autonomic deficit on skin biopsy in 45% or more of both groups of migraineurs. Extending the head-up tilt table test to 45-minutes increases diagnostic sensitivity, spares patients misdiagnosis and unnecessary testing, and satisfies the principle of ecological validity.

Autonomic nervous system function in women with anorexia nervosa.

Abnormalities in autonomic function have been observed in people with anorexia nervosa. However, the majority of investigations have utilised heart rate variability as the sole assessment of autonomic activity. The current study utilised a variety of methodologies to assess autonomic nervous system function in women with a current diagnosis of anorexia, a past diagnosis of anorexia who were weight-restored, and healthy controls. The sample included 37 participants: 10 participants with anorexia, 17 weight-restored participants (minimum body mass index > 18.5 for minimum of 12months) and 10 controls. Assessments of autonomic function included muscle sympathetic nerve activity (MSNA) using microneurography, heart rate variability, baroreflex sensitivity, blood pressure variability, head-up tilt table test, sudomotor function and assessment of plasma catecholamines. MSNA (bursts/min) was significantly decreased in both anorexia (10.22 ± 6.24) and weight-restored (17.58 ± 1.68) groups, as compared to controls (23.62 ± 1.01, p < 0.001 and p = 0.033, respectively). Participants with anorexia had a significantly lower standard deviation in heart rate, lower blood pressure variability and decreased sudomotor function as compared to controls. Weight-restored participants demonstrated decreased baroreflex sensitivity in response to head-up tilt as compared to controls. Women with a current or previous diagnosis of anorexia have significantly decreased sympathetic activity, which may reflect a physiological response to decreased energy intake. During the state of starvation, women with anorexia also displayed decreased sudomotor function. The consequences of a sustained decrease in MSNA are unknown, and future studies should investigate autonomic function in long-term weight-restored participants to determine whether activity returns to normal.

Cardiovascular autonomic responses during head-up tilt test in newly diagnosed type 2 diabetes.

Autonomic dysfunction is commonly observed in patients with long-standing type 2 diabetes. Previous studies have confirmed the value of both subjectively assessed symptoms and objective measurements of autonomic nervous system function in diagnosing cardiovascular autonomic neuropathy. However, the head-up tilt test (HUTT) has been rarely used to investigate cardiovascular autonomic responses in subjects with high risk ofnewly diagnosed type 2 diabetes (nT2D). To evaluate autonomic cardiovascular responses through passive orthostatic challenge along the diabetes continuum. The study population was stratified as normoglycemic (n = 16), prediabetes (n = 20), and nT2D (n = 20). The prevalence of orthostatic intolerance and autonomic cardiovascular responses was evaluated with the Task Force Monitor during a 30-min passive HUTT. Spectral indices of heart rate and blood pressure variability and baroreceptor effectiveness index (BEI) were calculated through the HUTT. BEI was obtained by the sequence method. There were no differences in the prevalence of orthostatic intolerance or in the indices of heart rate and blood pressure variability among the three groups of study. The BEI was attenuated in the nT2D group in supine rest and throughout HUTT compared with normoglycemic and prediabetes groups. The multivariable linear regression analysis showed that BEI was associated with fasting glucose (β = - 0.52, p <0.001) and HbA1c (β = - 0.57, p <0.001) independently of cardiovascular risk factors. Cardiovascular autonomic neuropathy, expressed as blunted BEI, is the only abnormal autonomic nervous test detected in nT2D, and it was independently associated with fasting glucose and HbA1c values.

Early Cerebral Hypoperfusion in Patients with Orthostatic Intolerance Without Tachycardia During Head-Up Tilt Test is Independent of Vasovagal Response.

Cerebral hypoperfusion before syncope has been shown in patients with chronic orthostatic intolerance (OI) without tachycardia, but it is unknown if an initial decrease of cerebral blood flow velocity (CBFv) could be related to the vasovagal response (VVR) to head-up tilt test (HUTT). The objective of the study was to compare cardiovascular, cerebrovascular, and autonomic variables during HUTT in OI patients with or without a VVR. We included 74 subjects (58% female, mean age 33 ± 12 years) who underwent a 30-min HUTT and were divided into three groups: OI with VVR positive (VVR+), OI without VVR negative (VVR-), and asymptomatic healthy subjects with negative HUTT (control group). Cardiovascular, cerebrovascular, and autonomic variables were assessed beat-to-beat during HUTT with a Task Force monitor and a trans-cranial Doppler. Mean values were evaluated at baseline and throughout the first 10 min of tilting. Cardiovascular variables were similar in the three groups. Systolic, diastolic, and mean CBFv were similar in VVR+ and VVR-, but both groups had lower CBFv than the control group. Systolic and diastolic CBFv decreased from baseline since min 1 in VVR+ and VVR- and since min 5 in the control group. The mean CBFv had a significant decrease since min 1 compared to baseline in all groups. Spectral indices of heart rate and blood pressure variability showed a similar autonomic response to HUTT in all groups. Patients with chronic OI without tachycardia have early postural cerebral hypoperfusion, regardless of the VVR during HUTT.

Diagnosing Neurally Mediated Syncope Using Classification Techniques.

Syncope is a medical condition resulting in the spontaneous transient loss of consciousness and postural tone with spontaneous recovery. The diagnosis of syncope is a challenging task, as similar types of symptoms are observed in seizures, vertigo, stroke, coma, etc. The advent of Healthcare 4.0, which facilitates the usage of artificial intelligence and big data, has been widely used for diagnosing various diseases based on past historical data. In this paper, classification-based machine learning is used to diagnose syncope based on data collected through a head-up tilt test carried out in a purely clinical setting. This work is concerned with the use of classification techniques for diagnosing neurally mediated syncope triggered by a number of neurocardiogenic or cardiac-related factors. Experimental results show the effectiveness of using classification-based machine learning techniques for an early diagnosis and proactive treatment of neurally mediated syncope.

Adenosine plasma levels and adenosine receptor levels determine the outcome of adenosine test and head-up tilt test in syncopal patients with a normal heart

Abstract Background/Introduction The neurohumoral profile underlying the manifestation of reflex syncope remains incompletely understood. Adenosine plasma (ADP) and adenosine receptor (ADR) levels may differentiate the outcomes of head-up tilt table test (HUTT) and adenosine test (ADT) but their role in the diagnostic evaluation of patients with syncope has yet to be determined. Purpose We sought to assess the ADP and ADR levels in patients without structural heart disease who underwent HUTT and ADT tests as part of the diagnostic workup of syncope. We specifically investigated differences in the outcomes of the HUTT and ADT tests as well as to the ADP levels during HUTT. Methods HUTT and ADT were performed as per the standard protocols. ADT was considered positive in the event of asystole &amp;gt;6 seconds or heart block for &amp;gt;10 seconds after intravenous Adenosine 0.15 mg/kg administration in the supine position. ADP levels were assessed at three timepoints during the HUTT: at baseline (supine), immediately after bed tilt and, in cases of a positive HUTT, at the time of syncope. Patients were categorized in quintiles of very low, low, intermediate, high and very high baseline ADP levels. We also assessed the A2A ADR levels of monocytes. Results We prospectively analyzed 124 patients (71 women, age 46.78±21.01 years). ADT was positive in 12.9% of patients and HUTT in 44.4% of patients. Patients with very low baseline ADP levels (lowest quintile) more frequently presented with a positive ADT (odds ratio [OR] 4.08, 95% Confidence Interval [CI] 1.40 to 13.13, p&amp;lt;0.05). Baseline ADP did not differ between patients with positive and negative HUTT. However, patients with vasodepressor response to HUTT exhibited increase in ADP from baseline to bed tilt (0.33±1.03 vs. 0.42±1.14 ppm/Um/L, p&amp;lt;0.05) and in syncope (0.70±1.89, P&amp;lt;0.05), while no difference was noted in patients with cardioinhibitory or mixed response. Patients with positive ADT and negative HUTT had higher ADR levels (221.5±88.56 MFI) as compared to patients with negative ADT and positive HUTT (59.78±83.65 MFI, p&amp;lt;0.05) and to patients with positive ADT and HUTT (33.29±35.77 MFI, p&amp;lt;0.05). Within patients with positive HUTT, those with onset of syncope in the Isoprenaline provocation phase (&amp;gt;20 min) had lower ADR levels (80.88±238.98 vs 89.43±96.08 MFI, p&amp;lt;0.05). Conclusion(s) Baseline ADP levels are related to the outcome of ADT while an ADP increase immediately after bed tilt and in syncope is evident in vasodepressor response to HUTT. Higher ADR levels are related to positive ADT and negative HUTT. Lower ADR levels are associated with more delayed onset of syncope during HUTT. ADP and ADR levels warrant further investigation as they may characterize a subset of patients with specific responses to ADT and HUTT and may be implicated in the pathophysiology of reflex syncope. Funding Acknowledgement Type of funding sources: None.

Support Vector Machine-Based Classification of Vasovagal Syncope Using Head-Up Tilt Test.

Simple SummarySyncope is a medical condition triggered by short-lived interruption of the oxygen supply to the brain, which may result in free fall or accidents. The diagnosis of syncope is a challenging task, as various other states of altered consciousness present with the same symptoms as syncope. This work uses historical medical data for the diagnosis of syncope using sophisticated computing solutions. The experimental results prove the effectiveness of the approach, leading to the proactive prediction of syncope.Syncope is the medical condition of loss of consciousness triggered by the momentary cessation of blood flow to the brain. Machine learning techniques have been established to be very effective way to address such problems, where a class label is predicted for given input data. This work presents a Support Vector Machine (SVM) based classification of neuro-mediated syncope evaluated using train–test–split and K-fold cross-validation methods using the patient’s physiological data collected through the Head-up Tilt Test in pure clinical settings. The performance of the model has been analyzed over standard statistical performance indices. The experimental results prove the effectiveness of using SVM-based classification for the proactive diagnosis of syncope.

Association of folate and vitamin B12 deficiency with vasovagal syncope: a case-control study

Abstract Background Studies demonstrated an association between vitamin B12 deficiency and vasovagal syncope (VVS) in pediatric patients. Moreover, some evidence suggested a pathophysiological role of plasma catecholamines elevation in VVS, which can arise from folate or vitamin B12 deficiency in terms of biochemical pathways. Purpose We aimed to evaluate the association of folate and vitamin B12 deficiency with VVS in adults. Methods In this case-control study, adult patients (18–70 years of age) with the diagnosis of VVS based on history and physical examination (2018 ESC guidelines) who underwent a head-up tilt test (HUTT) were included as the case group. The control group comprised age- and sex-matched individuals who participated in a population-based cohort study. The most important exclusion criteria were taking vitamin B12 or folate supplements, carbamazepine and phenobarbital, and a history of bariatric surgeries. Plasma levels of vitamin B12, folate, homocysteine, and thyroid-stimulating hormone (TSH), a possible confounder, were measured by Abbott Diagnostics chemiluminescence kits. We compared categorical variables and continuous variables by Chi-square and t-test, respectively. Logistic regression models were employed for adjusting for possible confounders, including age, sex, and TSH. Results From February 2020 to February 2021, we screened 157 patients with VVS, of whom 44 patients were included. After matching for age and sex, 44 healthy individuals without a history of syncope were examined as the control group. The mean age was 37.9 years in both groups, with 23 women (52.3%) in each group. Baseline characteristics were comparable across the study groups. There were no significant differences between serum levels of vitamin B12, folate, homocysteine, and TSH, as well as the prevalence of deficiency of folate and vitamin B12 between case and control groups (Table 1), even after adjusting for confounding variables. Serum levels of vitamin B12 were remarkably lower in patients with a lifetime syncopal episodes of ≥3 compared to patients with &amp;lt;3 lifetime attacks (Table 2, P=0.042). This correlation remained statistically significant after adjusting for possible confounders, including age, sex, and TSH by the logistic regression model (P=0.032). Conclusions In this study, we found that there is no significant difference between the prevalence of folate and vitamin B12 deficiency and serum levels of these vitamins in adult patients with VVS and healthy individuals; however, serum vitamin B12 was significantly lower in patients with recurrent VVS compared to patients with a lower burden of syncopal episodes. Future studies with larger sample sizes are recommended in the recurrent VVS subgroup. Therapeutic implications of these findings should be investigated in randomized-controlled trials. Funding Acknowledgement Type of funding sources: Foundation. Main funding source(s): Iran National Science Foundation Table 1Table 2