Predictors of Positive Head-Up Tilt Test in Patients with Suspected Neurocardiogenic Syncope or Presyncope

OH, J.H., et al .: Predictors of Positive Head-Up Tilt Test in Patients with Suspected Neurocardiogenic Syncope or Presyncope. Neurocardiogenic syncope is the most common cause of syncope in patients who present in outpatient clinics. Head-up tilt test (HUT) has been widely used to diagnose neurocardiogenic syncope. However, the HUT does not always produce a positive response in patients with suspected neurocardiogenic syncope. The aim of the present study was to assess the clinical history and characteristics of patients with suspected neurocardiogenic syncope or presyncope who undertook HUT, and to identify prognostic factors of a positive HUT response. During the first phase of HUT, patients were tilted to a 70-degree angle for 30 minutes. If the first phase produced a negative response, the second phase was subsequently performed involving intravenous isoproterenol administration. Of 711 patients, 423 (59.5%) patients showed a positive HUT response. In contrast to previous studies, this study showed that the vasodepressive type (76.6%) was the most common pattern of positive response, and that the rate of positive response during the first phase was low (7.1%). By multivariate analysis, the occurrence of junctional rhythm was found to be a predictor of an impending positive response in HUT   (P < 0.001)   . The shorter time interval between the last episode and HUT was also a predictor of positive response   (P = 0.0015)   . Younger age   (P = 0.0003)   and a history of physical injury during a syncopal episode   (P = 0.019)   were found to be associated with a positive response in the first phase of HUT. (PACE 2003; 26[Pt. I]:593–598)     

Demonstration of Syncope in Patients After Pacemaker Implantation: Role of Head-Up Tilt Test to Distinguish Neurocardiogenic Vasodepressor Syncope From Pacemaker Syndrome

It is important to distinguish clinically neurocardiogenic syncope from pacemaker syndrome in patients after pacemaker implantation. We report two syncopal patients with AV sequential physiological pacemakers who displayed neurocardiogenic Vasodepressor syncope (VDS) during head-up tilt (HUT) testing. Neurocardiogenic VDS, as a cause of syncope in patients following pacemaker implantation, might be involved in these patients as well as pacemaker syndrome. HUT is a useful diagnostic test in distinguishing neurocardiogenic VDS from pacemaker syndrome in patients with syncope following pacemaker implantation. Careful evaluations for diagnosis of pacemaker syndrome are needed in these patients.     

A "Dysautonomic" Head-Up Tilt Test Pattern in Elderly Patients with Neurocardiogenic Syncope

The characteristics of neurocardiogenic syncope (NCS) in elderly patients remain unclear. We compared the hemodynamic profiles of young and older patients with consecutive and positive head-up tilt tests (HUT). Continuous, noninvasive, and reliable monitoring of arterial pressure (AP) and heart rate (HR) was done throughout 46 consecutive positive HUTs of symptomatic patients. The population (12-82 years old) was divided into two groups: younger patients, Y (n = 25, < or = 65 years), and older patients, O (n = 21). Changes in AP and HR after the first minute of tilting, during the stable orthostatic phase and during syncope were compared. Except for systolic pressure, baseline hemodynamic parameters were similar in Y and O. No difference appeared in the mean time elapsed before syncope (19+/-9 vs 22+/-2 min). Asymptomatic hypotension was observed, only in O, 1 minute after tilting, followed by a progressive fall in the mean AP before syncope (0+/-0.9 vs -1+/-0.7 mmHg/min) without HR increase (0.7+/-1 vs 0+/-0.6 beats/min). This pressure slope was strongly related to age (r = 0.54, P < 0.001). Hemodynamic recording during HUT identifies a dysautonomic pattern in elderly patients with NCS and the abnormal AP/HR responses to orthostasis may be a feature specific to this population. Although the central mechanism of NCS is common to all ages, the age-related characteristics of the trigger event may indicate the need for specific management at different ages.     

Tilt Training: A Treatment for Malignant and Recurrent Neurocardiogenic Syncope

The treatment of neurocardiogenic syncope is insufficient in many cases. We hypothesized that the repeated exposure of the cardiovascular system to orthostatic stress could have a therapeutic effect on the regulation of cardiovascular reflex mechanisms. We have started a program of tilt training for heavily symptomatic patients. After hospital admission, patients were tilted daily (60-degree inclination), until syncope, or until a maximum of 45–90 minutes. The patients were instructed to continue a program of daily tilt training at home: two 30-minute sessions of upright standing against a vertical wall. No medication was prescribed. A total of 260 tilt table sessions were performed in 42 patients. The first tilt test was positive after 21 ± 13 minutes. The syncope was cardioinhibitory in 14 cases, vasodepressor in 19, mixed in 9. At the time of hospital discharge, 41 patients could support 45 minutes of head-up tilting. After a mean follow-up time of 15.1 (SD 7.8) months, 36 patients remained completely free of syncope. Syncope still occurred in one patient and presyncope in four patients. One patient died from an extensive myocardial infarction. The abnormal autonomic reflex activity of neurocardiogenic syncope can be remedied by a program of continued tilt training without the administration of drugs. This new treatment has proven to be effective for the vasodepressor and the cardioinhibitory type of syncope.     

Usefulness of Plasma Catecholamines During Head-Up Tilt as a Measure of Sympathetic Activation in Vasovagal Patients

Vasovagal syncope is a common clinical disorder which has been traditionally related to a vasovagal reflex precipitated by an initial excess sympathetic stimulation. We hypothesized that the increase in plasma Catecholamines during head-up tilt is more accentuated in patients with tilt induced vasovagal syncope. To test this hypothesis, plasma Catecholamines were measured in supine posture and during head-up tilt in patients with a history suggestive of vasovagal syncope. Of these, 13 had a normal response to tilt (nonvasovagal group; age 41 ± 19 [SD]years) and 11 had a vasovagal response to tilt (vasovagal group; 39 ± 20 years). In the supine posture at rest, plasma epinephrine and norepinephrine were not significantly different between the nonvasovagal and the vasovagal groups (39 ± 28 ng/L vs 46 ± 38 ng/L, P = 0.5792, 335 ± 158 ng/L vs 304 ± 124 ng/L, P = 0.6007, respectively). Furthermore, the tilt induced changes in plasma epinephrine and norepinephrine were not different between the two groups (20 ± 20 ng/L vs 35 ± 55 ng/L, P = 0.3562, 264 ± 158 ng/L vs 242 ± 205 ng/L, P = 0.7724, respectively) suggesting that differences in the hemodynamic response to tilt are not predictable by the supine levels of circulating plasma Catecholamines, and that the extent of plasma catecholamines increase during tilt does not determine the hemodynamic outcome of the tilt test. Since orthostatic changes of plasma Catecholamines could be influenced by volume factors, we assessed plasma renin activity and aldosterone as surrogates of blood volume. Baseline plasma renin activity and aldosterone were not significantly different between the two groups. We conclude that inasmuch as plasma catecholamines reflect the status of sympathetic activity, our data do not support the hypothesis that accentuation of sympathetic activity precedes necessarily the tilt induced vasovagal syncope. However, one should take in consideration that multiple factors may influence catecholamine levels and catecholamines kinetics. A hyperresponsiveness of β-receptors to Catecholamines in patients with vasovagal syncope may be suggested but needs to be tested.     

Vasovagal Syncope: Diagnostic Role of Head-Up Tilt Test in Patients with Positive Ocular Compression Test

We investigated the relative merits of the ocular compression test and the head-up tilt test to aid differentiation of syncope and seizures in young patients. Sixteen patients (10 males and 6 females) with a mean age of 14 ± 4.7 (SD) years (range 7–22 years) underwent graded head-up till (15°, 30°, and 45° for 2 minutes each, then 60° for 20 minutes) following positive ocular compression testing defined as precipitation of asystole for at least 3 seconds (mean 5 seconds ± 2 seconds, range 3–12 seconds). Each patient presented with recurrent unexplained loss of consciousness (mean number of episodes 30 ± 45, mean duration of illness 52 ± 40 months), and seven patients were receiving anticonvulsant medications, three of these had normal EEGs. Eleven patients (69%) developed vasovagal syncope during head-up tilt, reproducing their clinical episodes (systolic blood pressure decreased from 105 ± 10 mmHg to 84 ± 13 mmHg, diastolic blood pressure from 75 ± 9 to 22 ± 25 mmHg, and heart rate from 89 ± 13 beats/mm to 37 ± 20 beats/min). Asystole occurred in two patients during vasovagal syncope lasting 11 seconds in one and 16 seconds in the other, and, it was associated with myoclonic movements in both (convulsive syncope). Based on these findings, and given the perceived potential hazards of the ocular compression test, the head-up tilt test may be a safer procedure that adds useful information to the diagnostic evaluation of these patients.     

The Usefulness of Head-Up Tilt Testing and Hemodynamic Investigations in the Workup of Syncope of Unknown Origin

To enhance the clinical evaluation of patients suffering from recurrent syncope of unknown origin, the integrity of mechanisms controlling blood pressure was examined in 151 patients utilizing a screening tilt test. Ninety-eight patients had an abnormal blood pressure and/or heart rate response to tilt testing, including provoked syncopal attacks in 63 patients. Whenever indicated, the screening tilt test was followed by blood volume and hemodynamic determinations, as well as autonomic nervous system testing to identify contributing pathophysiological abnormalities (hypovolemia, venous pooling, autonomic dysfunction). Detailed analysis of this battery of tests allowed us to conclude that: (1) The tilt test is commonly a provocative tool in the workup of patients with recurrent syncope due to vasovagal - vasodepressor reactions and other abnormalities of blood pressure regulation; (2) Its usefulness is augmented by associated hemodynamic and blood volume evaluations; (3) The identification of contributory pathophysiological mechanisms of blood pressure control facilitates specific therapeutic interventions.     

Methods Other Than Tilt Testing for Diagnosing Neurocardiogenic (Neurally Mediated) Syncope

The recording of spontaneous episodes of bradycardic neurocardiogenic syncope (NCS) has shown that: a prolonged ventricular asystole seems necessary to cause syncope; asystole is preceded by other bradyarrhythmias in the vast majority of cases; some warning symptoms precede the loss of consciousness in most cases; conventional dual-chamber pacing is efficacious both in patients with a positive response to carotid sinus massage (CSM) and eyeball compression test (EBC) and in those with a positive response to tilt-testing (TT). CSM, EBC, and TT are established tools for diagnosing NCS, when the recording of spontaneous syncope is lacking. When combined together, they are probably able to correctly identify most patients affected by NCS. Nevertheless, whether the type of reflex induced by the cardiovascular reflexivity maneuvers correlates with that of the spontaneous syncope is largely unknown. Our knowledge suggests that the correlation may be unsatisfactory, owing to the following: the variability of the mechanism of spontaneous syncope from patient to patient and also, in the same patient, from one episode to another; the discordance of the type of response when 2 or 3 tests are positive in the same patient, the response being more frequently asystolic with CSM and EBC and more frequently vasodepressor with TT; the different timing between hypotension induced by CSM (in which it follows the bradycardia) and that induced by TT (in which it usually precedes the bradycardia) and the uncertainty about the timing of hypotension during the spontaneous syncope; the good reproducibility of the spontaneous event by CSM and EBC, but not by TT, when cardiac asystole is the manifestation of NCS: and the fairly high rate of false-positive results of cardiovascular reflexivity maneuvers. Hypotension is the main reason for the failure of pacemaker therapy in all the forms of neurocardiogenic syncope (NCS), whether diagnosed by CSM, EBC, or TT. Thus, the need arises to correctly identify the magnitude of the hypotensive reflexes of spontaneous events.     

Sensitivity and Specificity of the Tilt Table Test in Young Patients with Unexplained Syncope

The usefulness of the head-up tilt testing (HUT) has heen previously addressed in diagnosing vasovagal neuroregulatory syncope in the teenage population. However, data concerning sensitivity and specificity is deficient due to the lack of control groups. We compared the response to HUT in young patients referred because of syncope or near syncope (n = 44, mean age 16 ± 3 years SD) to healthy young volunteers with a normal physical examination and no previous history of syncope (n = 18, mean age 16 ± 2 years) and io determine the sensitivity and specificity of HUT. The graded tilt protocol was performed at 15°, 30°, and 45° (each for 2 min), and then 60° for 20 minutes. Cuff blood pressure was measured every minute and lead IIECG was continuously monitored. Results; 25 of the 44 patients (57%) developed a vasovagaJ response or became symptomatic after 13.8 ± 5.7 minutes of HUT. Three of the 18 volunteers (17%) had a vasovagal response and became symptomatic after 9 ± 3 minutes of HUT. There was no statistical difference among the four groups (with and without tilt induced vasovagal response) in terms of age and baseline hemodynamic data. The sensitivity of 20 minutes HUT was 57% and its specificity was 83%. The presyncopal hemodynamic response in patients with history of syncope that was characterized by a significant decrease in systolic blood pressure and lack of increase of diastolic blood pressure as compared with baseline and with other groups. Gonclusions: 20 minutes at 60° HUT has a high specificity for the diagnosis of vasovagal syncope. Its limited sensitivity is counterbalanced by the advantage of limiting the incidence of false-positive results in patients without the vasovagal syndrome.     

Tolerance to Lower Body Negative Pressure Exposure: Comparison Between Patients with Neurocardiogenic Syncope and Controls

Lower body negative pressure exposure (LBNPE) produces hemodynamic modifications similar to those produced by head-up tilt test (HUT). Patients with vasovagal syncope are more susceptible to HUT than healthy persons. The supine position during LBNPE would facilitate the simultaneous performance of complementary methods. The aim of this study was to compare tolerance to LBNPE between a group of patients with vasovagal syncope and a group of healthy volunteers. Eleven patients with vasovagal syncope and positive HUT and 13 healthy volunteers without prior history of syncope and negative HUT were included. The following protocol was used: −10 mmHg, 1 minute; −20 mmHg, 1 minute; −30 mmHg, 3 minutes, and −40, −50, −60, and −70 mmHg, 5 minutes for each stage. Tolerance was expressed as: maximum tolerated negative pressure (Max NP), maximum tolerated time (Max T), and Σ P × T, where P = pressure and T = time. Syncope or presyncope during the test was considered positive LBNPE. LBNPE was positive at −50 or −60 mmHg in 8 of 11 patients (73%). One healthy volunteer had presyncope after 5 minutes at −70 mmHg. Tolerance, as expressed by any of the three parameters, was significantly higher for the healthy volunteers (Max NP: −59.1 ± 7.9 vs −70, P < 0.01; Max T: 19.1 ± 4.2 vs 24.4 ± 0.3, P < 0.01; Σ P × T: 836.3 ± 269.5 vs 1214.6 ± 18, P < 0.01). We conclude that patients with neurocardiogenic syncope have a significantly lower tolerance to LBNPE than subjects with no previous history of syncope.     

Head-Up Tilt Test in Patients with High Pretest Likelihood of Neurally Mediated Syncope: An Approximation to the "Real Sensitivity" of this Testing

This study was designed to examine the "true sensitivity" of a specific head-up tilt (HUT) testing protocol using clinical findings. The HUT protocol used 45 minutes at 60 degrees for the baseline portion and intermittent boluses of 2, 4, and 6 micrograms of isoproterenol in the second phase. Eighty-eight patients (40 men and 48 women; mean age of 33.8 +/- 16 years) with recurrent syncope and high pretest likelihood of neurally mediated syncope were included. The following were considerated as high pretest likelihood criteria: (1) at least two syncopal episodes; (2) no structural heart disease and normal baseline ECG; (3) age < 65 years; (4) a typical history of neurally mediated syncope, triggering factors plus premonitory signs; and (5) short duration of symptoms and fast recovery without neurological sequelae. Fifty-four patients (61%) had a positive tilt test (34/88 baseline [39%] and 20/50 with isoproterenol [40%]). The shorter time interval between the last syncopal episode and baseline HUT test was the only predictor for a positive response (P < 0.003). Conversely, this time interval was not predictor of positive responses during isoproterenol-tilt testing. In conclusion: (1) we claim a "sensitivity" for this combined protocol of 61%; and (2) our results indicate that patients with syncope of unknown origin must be tilted nearest as possible to the last syncope to increase the positive responses of HUT test.     

Safety and Tolerability of an Aggressive Tilt Table Test Protocol in the Evaluation of Patients with Suspected Neurocardiogenic Syncope

Safety and tolerability of a one-step tilt table test with high dose (5 μg/min) isoproterenol (ISO) without intermediate stages were evaluated in a symptomatic population of 300 patients referred for clinical syncope, near syncope, or dizziness. ISO has been used as a provocative test but remains controversial. A population of 118 male and 182 female patients with a mean age of 45 (range 5–90) years underwent 300 tests. Heart rate and blood pressure were monitored continuously. A positive test was one in which clinical symptoms were reproduced or hemodynamic criteria met. Patients were initially supine for 5 minutes followed by head upright tilt (HUT) to an angle of 80± for 10 minutes. Negative tests were repeated with an infusion of ISO at a rate of 5 μg/min, HUT was positive in 133 (44.3%) of 300 tests. With a 10-minute HUT alone, only 17 (5.7%) of 300 of tests were positive. Of the initial negative tests, 273 of 283 were tested with ISO. With ISO, 116(42.5%) of 273 were positive. ISO in high dose (5 μg/min) was used in 264 of 273 patients, while low dose (1.0–2.5 μg/min) was used in 9 of 273 under special circumstances. High dose ISO was tolerated in 164 (62.1 %) of 264 patients, reduced in 87 (33%) of 264, and discontinued in 11 (4.2 %) of 264. Reasons for reduction included tachycardia (40 patients), nausea (31 patients), chest pain (2 patients), arrhythmia (5 patients), or other (9 patients). Adverse effects resolved within 1 minute of dose reduction. This one-step high dose ISO protocol reproduced neurocardiogenic syncope in symptomatic patients who tested negative without ISO and was safe, tolerated, and expeditious.     

Heart Rate Variability During Head-up Tilt Testing in Patients with Suspected Neurally Mediated Syncope

The relation between heart rate variability (HRV) and outcome of head-up tilt testing (HUT) in patients with neurally mediated syncope (NMS) was studied in 30 patients with presumed NMS (33 ± 13 years) and in 11 age-matched controls. After 15 minutes of baseline supine observation, patients were tilted to 60± for 45 minutes or until syncope occurred. HRV parameters included RR intervals, standard deviation of normal-to-normal RR intervals (SDNN), and root mean square successive differences (RMSSD). HRV analysis was performed during 5-minute intervals in the supine position immediately after onset of HUT and before syncope or after 30–35 minutes of tilt in patients without syncope. Syncope occurred after a mean tilt duration of 32 minutes in 14 (47%) of 30 patients with presumed NMS, whereas all controls had an uneventful HUT. In the supine position, RR intervals and RMSSD were comparable among HUT-positive patients, HUT-negative patients, and controls (RR intervals: 799 ± 92, 854 ± 137, and 818 ± 128 ms, P = NS; RMSSD: 43 ± 40, 36 ± 34, and 53 ± 42 ms, P = NS). Baseline SDNN was also comparable in HUT-positive patients versus HUT-negative patients with presumed NMS (50 ± 26 vs 52 ± 20 ms, P = NS). Within 5 minutes preceding syncope or after 30–35 minutes of tilt, RR intervals and RMSSD were shorter in HUT-positive patients compared to HUT-negative patients, or to controls (RR intervals: 606 ± 86 vs 710 ± 117 and 739 ± 123 ms, P < 0.05; RMSSD: 12 ± 5 vs 23 ± 19 and 40 ± 32 ms, P < 0.05). Thus, HRV analysis in the baseline supine position was not a predictor of HUT outcome in patients with suspected NMS. Syncope during HUT seemed to be preceded by increased sympathetic activity manifested by an increase in heart rate and by a decreased parasympathetic tone manifested by a decrease in RMSSD measured for 5 minutes before the event, in comparison with HUT-negative patients and with controls.     

Polymorphic Ventricular Tachycardia Induced During Tilt Table Testing in a Patient with Syncope and Probable Dysfunction of the Sinus Node

We present a case of life-threatening arrhythmia occurring during tilt table testing in a 44-year-old man with syncope. Polymorphic ventricular tachycardia occurred while the patient was tilted up under the intravenous infusion of isoproterenol (2 μg/min). No ischemia, QTc prolongation, or electrolyte abnormality preceded this event. The arrhythmia was not induced by programmed ventricular stimulation or exercise testing. Based on electrophysiological and clinical data, the diagnosis of sick sinus syndrome was entertained.     

Head-Up Tilt Testing With and Without Isoproterenol Infusion in Healthy Subjects of Different Ages

Passive head-up tilt testing with or without infusion of isoproterenol is used in the investigation and management of patients with syncope. Twenty-five healthy asymptomatic volunteers prospectively grouped according to age (young [28 ± 1.7 years]: n = 9; middle [51 ± 3.3 years]: n = 11; elderly [81 ± 2.4 years]; n = 5; mean ± SE) were studied during: (1) supine carotid sinus massage: (2) 60° head-up tilt aione; and (3) infusion of isoproterenoJ to raise the heart rate 20% above supine baseline, prior to a 10-minute repeat tilt. Symptoms occurred in three subjects (12%) and only occurred with passive tilting alone. Two young subjects had syncope with sinus pauses greater than 10 seconds, One elderly subject developed atrial flutter. No subject had symptoms or hypotension during tilt plus isoproterenol or a pause greater than 3 seconds with carotid sinus massage. With passive tilt, mean heart rate increased by 16 ± 6 beats/min and 18 ± 7.8 beats/min in the young and middle aged subjects (P < 0.05), but only by 6 ± 5 beats/min in the elderly (P = NS, supine vs 60° in each group). With head-up tilt plus isoproterenol infusion, the mean heart rate elevation in response to tilt was 17 ± 9 beats/ min, 8 ± 3 beats/min, and 12 ± 4 beats/min for the young, middle, and elderly subjects, respectively (P < 0.05, supine vs 60° in each group). Supine serum norepinephrine concentration values were 229 ± 33 pg/mL, 374 ± 107 pg/mL, and 409 ± 41 pg/mL (mean ± SE) in the young, middle aged, and elderly groups, respectively (P = 0.05, young vs elderly). With head-up tilt, these significantly rose in the three groups. With tilt, serum epinephrine tended to rise (P < 0.10) only in the young and middle aged groups. Serum dopamine did not significantly increase in response to tilt in any of the groups. These studies suggest that tilt testing protocols need to be assessed against age and protocol matched controls.     

Comparison of Sensitivity and Specificity of Tilt Protocols with and without Isoproterenol in Children with Unexplained Syncope

Head-up tilt testing with or without isoproterenol is extensively used in the evaluation of patients with unexplained syncope. However, sensitivity and specificity of tilt protocols with and without isoproterenol have not been clarified in children, due to lack of age matched control subjects. This study was designed to assess and to compare the sensitivity and specificity of tilting alone and tilting in conjunction with isoproterenol. Thirty children with unexplained syncope (group I) and 15 age-matched control subjects (control group I) underwent successive 60° head-up tilts for 10 minutes during infusions of 0.02, 0.04, and 0.06 μg/kg/min of isoproterenol, after a baseline tilt to 60° for 25 minutes. Also, 35 children (group II) with unexplained syncope and 15 healthy control subjects (control group II) were evaluated by head-up tilt to 60° for 45 minutes without an infusion of isoproterenol. In response to tilt protocol with graded isoproterenol, 23 (76.6%) of the patients in group I and 2 of the 25 (13.3%) control subjects developed syncope. Accordingly, the sensitivity of tilt testing with isoproterenol was 76.6%, and its specificity was 86.7%. Tilt testing without isoproterenol was positive in 17 (48.5%) of the patients in group II but in only 1 of the 15 (6.6%) control subjects. Thus, sensitivity and specificity of tilt testing without isoproterenol were 48.5% and 93.4%, respectively. The mean heart rate and systolic blood pressure decreased significantly (P < 0.001) in all tilt positive patients during syncope. In conclusion, the head-up tilt test is a valuable diagnostic test in the evaluation of children with unexplained syncope, and isoproterenol is likely to increase the sensitivity of the test without decreasing its specificity.     

Reproducibility of Head Upright Tilt Table Test Results in Patients with Syncope

Head upright tilt table testing is a promising technique for the evaluation and management of vasovagal (neuroregulatory) syncope. In order to determine the day-to-day reproducibility of results using this technique we performed head upright tilt table testing (with or without graded isoproterenol infusion) in 21 patients (12 males, 9 females, mean age 34 ± 19.1 years). During the first tilt study a total of 14 patients experienced syncope (six during baseline tilt, mean tilt time 15.8 ± 7 minutes, eight following tilt with graded isoproterenol infusion, mean tilt time 17.7 ± 9 minutes) while seven were negative. During the second tilt study (performed 3–7 days following the first study) the results of the first study were duplicated in 19 patients (90%) (six during baseline tilt, mean time 17.5 ± 8 minutes, eight following graded isoproterenol infusion, mean time 15.9 ± 7 minutes), however the level of provocation required to provoke syncope differed from that needed in the initial test in five patients (24%). We conclude that the results of head upright tilt table testing with graded isoproterenol infusions can be duplicated in 90% of patients, although some day-to-day variability exists in the degree of provocation necessary to elicit a positive response.     

Low Body Mass Index Is Associated with a Positive Response during a Head‐Up Tilt Test

Background : To describe the association between body mass index (BMI) and a positive response during a head‐up tilt test (HUT) in patients referred for an investigation of syncope. Methods : Observational study of patients referred for the diagnostic evaluation of syncope. Patients were divided into four groups according to their BMI: <18.5 kg/m², 18.5–24.9 kg/m², 25–29.9 kg/m², and > 30 kg/m². Results : A total of 419 patients were evaluated. The mean age was 43 ± 22 years, and 62% were female. The prevalence of a positive tilt test was different between groups when stratified by BMI (P = 0.01), with a higher proportion of patients with positive tests among those with BMI <18.5 kg/m² compared with other groups (P = 0.05). Multivariate analysis also showed that underweight patients had a 3.9 times higher risk for a positive HUT response (P = 0.01); additionally, the use of contraceptive drugs was associated with a protective effect during HUT (odds ratio: 0.35, confidence interval:0.19–0.45, P = 0.001). Conclusion : In our sample, changes in BMI are associated with a positive response for HUT, and oral contraceptives seemed to protect against this response. Further studies are needed with larger numbers of patients to corroborate this finding. (PACE 2013; 36:37–41)     

Studies on Hemodynamic Instability in Paroxysmal Supraventricular Tachycardia: Noninvasive Evaluations by Head-Up Tilt Testing and Power Spectrum Analysis on Electrocardiographic RR Variation

DOI, A., et al. : Studies on Hemodynamic Instability in Paroxysmal Supraventricular Tachycardia: Noninvasive Evaluations by Head-Up Tilt Testing and Power Spectrum Analysis on Electrocardiographic RR Variation. Hemodynamic instability is a crucial determinant of the best therapeutic option in paroxysmal supraventricular tachycardia (PSVT). However, it is still unclear if hemodynamic instability is tachycardia dependent or independent. We performed frequency-domain analysis of electrocardiographic RR variations during induced PSVT and head-up tilt tests after successful ablation to investigate the role of autonomic vasomotor function in hemodynamic instability during PSVT. Thirty-six patients with (syncope group,  n = 18  ) and without (nonsyncope group,  n = 18  ) syncope and/or presyncope during PSVT were enrolled in this study. Serial blood pressure, heart rate, and variations in heart rate during induced PSVT and head-up tilt tests were examined. Initial blood pressure fall and heart rate changes during induced PSVT were greater in the syncope group than in the nonsyncope group. A significant positive linear relationship was found between these two. Delayed blood pressure fall was observed in the syncope group, independent of heart rate changes. Syncope in PSVT could be predicted from the results of head-up tilt tests with 82% accuracy. Heart rate responses after isoproterenol infusion were significantly greater in the syncope group than in the nonsyncope group. The changes in low frequency to high frequency (LF:HF) values during induced PSVT and head-up tilt tests were significantly greater in the syncope group than in the nonsyncope group, and an exponential correlation was found between LF:HF changes in both tests. We conclude that PSVT rate and vasomotor reaction are related with hemodynamic instability during PSVT and head-up tilt testing is a useful method for determining if patients will have syncope during PSVT.