Positive Head-up Tilt Test Research Articles

719-1 Does Vasodepressor Syncope Require Normal Ventricular Function?

Vasodepressor syncope is believed to be preceded by hypercontractility which leads to mechanoreceptor stimulation. Therefore, a preserved left ventricular function is supposedly required to trigger the reflex. We analyzed our experience in patients with positive head-up tilt test. Out of 500 patients 32 had previous history of structural heart disease. Of them 8 patients had severe left ventricular dysfunction (EF < 30%). The mean age was 52 ± 8 years, 5 were male and 3 female. Mean EF was 22 ± 5%. Six patients had dilated cardiomyopathy and 2 had myocardial infarction. Electrophysiologic study was negative in 6 patients while the remaining two had inducible sustained monomorphic ventricular tachycardia requiring defibrillator implant. Syncope was witnessed by physicians in 6 out of 8 patients and was associated with bradycardia and hypotension. In all 8 patients head-up tilt reproduced symptoms. Upright tilt was positive at baseline in 7 patients and during isoproterenol infusion in 1 patient. Five patients were treated with theophylline, 1 with ephedrine, and 2 with disopyramide. After a mean follow-up of 2.2 ± 1.3 years all 8 patients were free of vasodepressor-related syncope. We conclude that vasodepressor syncope is possible even in the presence of severely impaired ventricular function and should, therefore, be entertained in such cases. Alternative mechanisms may mediate the circulatory response in this population.

749-3 Time Evolutive (Recursive) Heart Rate Variability Analysis Provides New Insights into the Mechanisms of Vasovagal Syncope During Head-up Tilt Test

Vasovagal syncope (WS) during head-up tilt test (HUT) is the result of an imbalance of the sympathovagal tone (5S). However, standard heart rate variability analysis (HRV) is of limited value in understanding WS mechanisms as it gives no insight into beat to beat modulation (BBM) of the 5S and requires stationary conditions. We used a new method based on a recursive estimation of HRV temporal indices to compare BBM of the vagal tone in 10 patients (pts) (27 ± 8) with WS during positive HUT to 10 control subjects (C) (32 ± 3) during 30 min. negative HUT. Time evolutive HRV demonstrates, in the last seconds before syncope, the paradoxical vagal input to the sinus node confirmed by a sudden raise of sinus variability, never shown before. Time evolutive HRV is a promising method yielding new insights into the imbalance of the 5S appearing during VVS.

Limitations of head-up tilt test for evaluating the efficacy of therapeutic interventions in patients with vasovagal syncope: Results of a controlled study of etilefrine versus placebo

Objectives. This study assessed the efficacy of oral etilefrine (10 mg three times a day) in preventing a positive response to head-up tilt testing.Background. Previous reports have suggested that oral etilefrine can be effective either in preventing a positive response to head-up tilt testing or in reducing syncopal recurrences in patients with vasovagal syncope. Up to now most studies assessing drug therapy in these patients have been uncontrolled.Methods. This was a randomized double-blind crossover study of etilefrine versus placebo in 30 consecutive patients with syncope and a baseline positive head-up tilt test. After the first test, patients had no treatment for 3 days and were randomized to receive etilefrine or placebo for 4 additional days. They underwent tilt testing under treatment and again after 3 days of washout; they then received the alternative treatment for 4 days, and a third test was performed.Results. Head-up tilt test results were negative in 13 (43%) patients with etilefrine and 15 (50%) with placebo (p = NS). Therefore, the statistical power of the study was only 10%. The rate of positive responses decreased with repeated testing irrespective of the assigned treatment: A positive response was obtained during the second head-up tilt test in 20 patients (10 with placebo, 10 with etilefrine) but in only 12 during the third (7 with etilefrine, 5 with placebo) (p < 0.05).Conclusions. Oral etilefrine (10 mg three times a day) was not superior to placebo in preventing a positive response to head-up tilt testing. Despite a low statistical power, the high rate of negative response with placebo (50%) suggests that controlled trials are needed to assess the real efficacy of any treatment in patients with vasovagal syncope.

A placebo-controlled trial of intravenous and oral disopyramide for prevention of neurally mediated syncope induced by heap-up tilt

Objectives. A double-blind randomised trial was designed to determine the efficacy of intravenous and oral disopyramide phosphate in preventing neurally syncope induced by a head-up tilt test.Background. Neurally mediated syncope is a frequent cause of syncope and may be induced by head-up tilt, testing. Recent uncontrolled trials have suggested that disopyramide may be an effective therapy in patients with neurally mediated syncope.Methods. Twenty-two consecutive patients with recurrent neurally mediated syncope and two or successive positive head-up tilt test responses were randomly allocated to receive either intravenous disopyramide or placebo. Head-up tilt testing at 60 ° was performed for 15 min. If presyncope or syncope was not provoked, isoproterenol infusion was started at a rate of 1 μg/min and the rate gradually increased until a 25% increase in heart rate was achieved. Eleven patients were subsequently randomised in crossover fashion to receive oral disepyramide (800 mg/day) or placebo during 1 week. The primary end point was prevention of syncope or presyncope provoked by head-up tilt testing.Results. Head-up tilt test results were positive for syncope in 12 (75%) of 16 patients receiving intravenous placebo and in 12 (60%) of 20 patients receiving disopyramide (p = 0.55 Fisher exact test, 95% confidence interval [CI] −14% to 40%).In the intravenous phase, complete crossover was achieved in 15 patients. Head-up tilt test results during this were positive in 13 patients (87%) receiving placebo and in 12 patients (80%) receiving disopyramide (p = 0.50 Fisher exact test, 95% CI −19% to 32%) and were positive in all patients receiving their initially randomized drug or placebo. In the oral phase, head-up tilt results were positive in only two patients (18%) assigned to placebo and in three patients (27%) receiving disopyramide (p = 0.54 Fisher exact test, 95% CI −42% to 24%).A mean follow-up time of 29 ± 8 months was obtained in 21 of the 22 patients. Syncope recurred in 3 (27%) of the 11 patients receiving disopyramide and 3 (30%) of the 10 patients not treated pharmacologically (p > 0.05).Conclusions. Intravenous disopyramide was ineffective for the prevention of neurally mediated syncope provoked by head-up tilt testing. No significant effect was observed after oral therapy with disopyramide. There was a striking decrease in the incidence of positive tilt test results over time regardless of intervention, thus discouraging the use of head-up tilt as the single method of assessing therapeutic efficacy. Recurrence of syncope after the investigative protocol was infrequent over long-term follow-up regardless of treatment group.

Use of intravenous esmolol to predict efficacy of oral beta-adrenergic blocker therapy in patients with neurocardiogenic syncope

The usefulness of esmolol in predicting the efficacy of treatment with an oral beta-adrenergic blocking agent was evaluated in 27 consecutive patients with neurocardiogenic syncope. Seventeen patients had a positive head-up tilt test response at baseline and 10 patients required intravenous isoproterenol for provocation of hypotension. All patients were then given a continuous esmolol infusion (500 μg/kg per min loading dose for 3 min followed by 300 μg/kg per min maintenance dose) and rechallenged with a head-up tilt test at baseline or with isoproterenol.Of the 17 patients with a positive baseline tilt test response, 11 continued to have a positive response to esmolol challenge. Sixteen patients (including all 10 patients with a positive tilt test response with isoproterenol) exhibited a negative response to upright tilt during esmolol infusion.Irrespective of their response to esmolol infusion, all patients had a follow-up tilt test with oral metoprolol after an interval of ≥5 half-lives of the drug. All 16 patients (100%) with a negative tilt test response during esmolol infusion had a negative tilt test response with oral metoprolol. Of the 11 patients with a positive tilt test response during esmolol infusion, 10 (90%) continued to have a positive response with oral metoprolol.It is concluded that in the electrophysiology laboratory, esmolol can accurately predict the outcome of a head-up tilt response to oral metoprolol. This information may be helpful in formulating a therapeutic strategy at the initial head-up tilt test in patients with neurocardiogenic syncope.