Induction of neurally mediated syncope with adenosine.
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BACKGROUND: Tilt testing is used to establish the diagnosis of neurally mediated syncope. However, applicability of the tilt test is limited by test sensitivity and length of time required to perform the test. We hypothesized that adenosine could facilitate the induction of neurally mediated syncope through its sympathomimetic effects and therefore could be used as an alternative to routine tilt testing. METHODS AND RESULTS: In protocol 1, the yield of adenosine tilt testing (12 mg while upright, followed by 60 degrees tilt for 5 minutes) and a 15-minute isoproterenol tilt test were compared in 84 patients with a negative 30-minute drug-free tilt test. In protocol 2, 100 patients underwent an initial adenosine tilt test followed by our routine tilt test (30-minute drug-free tilt followed by a 15-minute isoproterenol tilt). Six additional control patients underwent microneurography of the peroneal nerve to compare the sympathomimetic effects during bolus administration of adenosine and continuous infusion of isoproterenol. In protocol 1, the yields of adenosine (8 of 84, 10%) and isoproterenol (7 of 84, 8%) tilt testing were comparable (P=NS). In protocol 2, the yields of adenosine (19 of 100, 19%) and routine (22 of 100, 22%) tilt testing were also comparable (P=NS). Although the yield of adenosine tilt testing was comparable in both protocols, patients with a negative adenosine tilt test but a positive routine tilt test usually required isoproterenol to elicit the positive response. Microneurography confirmed discordant sympathetic activation after adenosine and isoproterenol administration. CONCLUSIONS: Adenosine is effective for the induction of neurally mediated syncope, with a diagnostic yield comparable to routine tilt testing. However, the discordant results obtained with adenosine and the isoproterenol phase of routine tilt testing suggest that adenosine and isoproterenol tilt testing may have complementary roles in eliciting a positive response. Therefore, a tilt protocol that uses an initial adenosine tilt followed, if necessary, by an isoproterenol tilt would be expected to increase the overall yield and reduce the duration of tilt testing. (+info)
Effect of etilefrine in preventing syncopal recurrence in patients with vasovagal syncope: a double-blind, randomized, placebo-controlled trial. The Vasovagal Syncope International Study.
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BACKGROUND: Etilefrine is an alpha-agonist agent with a potent vasoconstrictor effect, which is potentially useful in preventing vasovagal syncope by reducing venous pooling and/or by counteracting reflex arteriolar vasodilatation. The present multicenter, randomized, placebo-controlled study was designed to evaluate the efficacy of this drug for the long-term management of patients with recurrent vasovagal syncope. METHODS AND RESULTS: In the 20 participating centers, 126 patients with recurrent vasovagal syncope (at least 3 episodes in the last 2 years) and a positive baseline head-up tilt response were randomly assigned to placebo (63 patients) or etilefrine at a dosage of 75 mg/d (63 patients) and were followed up for 1 year or until syncope recurred. The primary end-point of the study was the first recurrence of syncope. There were no differences between the 2 study groups in the patients' baseline characteristics. During follow-up, the group treated with etilefrine had a similar incidence of first syncopal recurrence to that of placebo group both in the intention-to-treat analysis (24% versus 24%) and in on- treatment analysis (26% versus 24%). Moreover, the median time to the first syncopal recurrence did not significantly differ between the 2 study groups (106 days in the etilefrine arm and 112 days in the placebo arm). CONCLUSIONS: Oral etilefrine is not superior to placebo in preventing spontaneous episodes of vasovagal syncope. Randomized controlled studies are essential to assess the real usefulness of any proposed therapy for patients with vasovagal syncope. (+info)
Utility of a single-stage isoproterenol tilt table test in adults: a randomized comparison with passive head-up tilt.
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OBJECTIVES: This study was conducted to develop a time-efficient tilt table test. BACKGROUND: Current protocols of tilt table testing are quite time-consuming. This study was designed to assess the diagnostic value, tolerance and procedural time of a single-stage isoproterenol tilt table protocol. METHODS: A single-stage isoproterenol tilt table test was compared with the passive tilt table test. The study was prospectively designed in a randomized and crossover fashion. RESULTS: The study population consisted of 111 patients with a history of syncope (mean age 55 +/- 20 years). Of the total, 62 patients (56%; 95% confidence interval, 46% to 65%) had a positive vasovagal response during isoproterenol tilt table testing and 35 (32%; 23% to 41%) during passive tilt table testing (p = 0.002). The mean procedural times of the study population were 11.7 +/- 3.6 min and 36.9 +/- 13.3 min for isoproterenol and passive tilt table testing, respectively (p < 0.001). All patients tolerated single-stage isoproterenol testing. In the 23 control subjects (mean age 34 +/- 11 years), the apparent specificities were 91% (72% to 99%) and 83% (61% to 99%) for passive and single-stage tilt table testing, respectively. CONCLUSIONS: The single-stage isoproterenol tilt table test was more effective in inducing a positive vasovagal response in an adult population than the standard passive tilt table test, and it significantly reduced the procedural time. The increase in positive yield was associated with a moderate decrease in apparent specificity. These observations support the conclusion that single-stage tilt table testing could be a reasonable diagnostic option in patients undergoing syncope evaluation. (+info)
Effects of paroxetine hydrochloride, a selective serotonin reuptake inhibitor, on refractory vasovagal syncope: a randomized, double-blind, placebo-controlled study.
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OBJECTIVES: The purpose of the study was to determine whether the well tolerated serotonin reuptake inhibitor paroxetine hydrochloride could prevent vasovagal syncope in patients resistant to or intolerant of previous traditional therapies. BACKGROUND: Serotonergic mechanisms play a major role in the processes leading to neurocardiogenic vasovagal syncope, and serotonin reuptake inhibitors have been reported to be effective in preventing refractory syncope. METHODS: Sixty-eight consecutive patients (26 men and 42 women, mean age 44.7+/-16.5 years) with recurrent syncope and positive head-up tilt test and in whom standard therapies with beta-adrenergic blocking agents, vagolytic, negative inotropic or mineral corticoid agents were ineffectual or poorly tolerated were referred for study. Patients randomly received either paroxetine at 20 mg once a day or a placebo. A head-up tilt test was then reperformed after one month of treatment, and the clinical effect was noted over a mean follow-up of 25.4+/-7.9 months. RESULTS: The response rates (negative tilt test) after one month of treatment were 61.8% versus 38.2% (p < 0.001) in the paroxetine and placebo groups, respectively. During follow-up spontaneous syncope was reported in six patients (17.6%) in the paroxetine group as compared to 18 patients (52.9%) in the placebo group (p < 0.0001). Only one patient (2.9%) asked to be discontinued from the drug for severe side effects. CONCLUSIONS: Paroxetine was found to significantly improve the symptoms of patients with vasovagal syncope unresponsive to or intolerant of traditional medications and was well tolerated by patients. (+info)
Contribution of head-up tilt testing and ATP testing in assessing the mechanisms of vasovagal syndrome: preliminary results and potential therapeutic implications.
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BACKGROUND: In patients with vasovagal syndrome, head-up tilt testing may reproduce symptoms generally associated with vasodepression. Recent research suggests ATP testing identifies patients with abnormal vagal cardiac inhibition. This preliminary study examined the joint contribution of both tests in identifying underlying mechanisms in the general population with vasovagal syndrome. METHODS AND RESULTS: Both tests were performed in random order during 1 session and outside of predominant sympathetic periods in 72 patients hospitalized for syncope (n=56) or presyncope (n=16) for whom no cardiac or extracardiac cause was found. For passive and isoproterenol-provocative tilt testing by standard protocol, reproduction of symptoms defined a positive test. The ATP test consisted of injecting ATP 20 mg IV at bedside, continuously monitoring ECG and blood pressure; a vagal cardiac pause >10 seconds defined a positive test. For most patients (64%), >/=1 test was positive. Of the 41 patients (57%) with a positive tilt test (either passive or provoked by isoproterenol), 32% had cardiac disease; none had significant bradycardia (<50 bpm). Of the 8 patients (11%) with a positive ATP test, 62% had cardiac disease; the probability of a positive result increased with age (P=0.015). Both tests were positive in 3 patients and negative in 26 patients; the tilt and ATP test results were uncorrelated (P=0.28). CONCLUSIONS: Results suggest tilt and ATP tests individually and jointly determine the mechanism of vasovagal symptoms in most patients and that vagal cardiac inhibition increases with age. (+info)
The effects of the hypothalamus on hemodynamic changes elicited by vagal nerve stimulation.
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To investigate the means by which neurogenic shock or syncope occur in dentistry, we determined the hemodynamic response to the activation of vagal tone in cats while they were under emotional stress. The hypothalamus and the vagal nerve were electrically stimulated to produce emotional stress and to activate vagal tone, respectively. Hemodynamic changes were recorded during vagal stimulation (Va group) and during vagal stimulation preceded by hypothalamic stimulation (AH + Va group). Although blood pressure decreased in both groups, the degree of hypotensive response in the AH + Va group was greater than the response in the Va group. Total peripheral resistance (TPR) was reduced in the AH + Va group but was increased in the Va group. The blood flow to the skeletal muscles in the AH + Va group was greater than that of the Va group. Reduced TPR, which could be due to vasodilation in the skeletal muscles, was the cause of intensified hypotension in the AH + Va group. Clearly, the hypotension produced by vagal stimulation was worsened when it was preceded by hypothalamic stimulation; this occurrence could be related to the tendency of blood to flow to the skeletal muscles. (+info)
Accurate diagnosis of convulsive syncope: role of an implantable subcutaneous ECG monitor.
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Convulsive syncope due to transient bradycardia is recognized as a cause of treatment-resistant seizures. However, the diagnosis may be difficult to make with conventional electrocardiographic devices if attacks are infrequent. We present a case of apparent epilepsy in which a new implantable electrocardiographic event recorder (the 'Reveal' insertable loop recorder) was used to show that attacks were caused by prolonged asystole of up to 36 s in duration. The insertable loop recorder may have an important role in the investigation of patients with treatment-resistant seizures, particularly where there is a strong suspicion of an underlying cardiac arrhythmia. (+info)
Serum prolactin levels after seizure and syncopal attacks.
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Loss of consciousness and falling are the key features of syncope. Common accompaniments include tonic and myoclonic muscle activity, eye deviations, automatisms, vocalizations and hallucinations that may render the distinction from epileptic seizures difficult. The frequently increased levels of serum prolactin (SPRL) were observed immediately after generalized and complex partial seizures. Presumably, the hormone release is caused by the propagation of epileptic activity, usually from the temporal lobe to the hypothalamic pituitary axis. Numerous reports have demonstrated that the post-ictal SPRL level may be used to differentiate between epileptic and syncopal, non-epileptic attacks. In order to confirm the hypothesis, the SPRL levels were measured in patients with complex partial seizures (CPS) and patients with vaso-vagal syncopal attacks (VVS). The SPRL levels were prospectively measured for each patient as soon as possible after the event (within 1 hour), then 1 hour after the first determination and finally blood was sampled 24 hours later. During the study period (18 months), 18 patients with CPS and 15 patients with VVS were investigated in total. The mean values of SPRL levels in both groups were increased immediately after the event (CPS group: 1142 +/- 305 mIU/l; VVS group: 874 +/- 208 mIU/l). The elevated SPRL levels were found in 14 (78%) patients immediately after CPS and in 9 (60%) patients immediately after VVS. After examining the results of the present study we conclude that the elevated serum prolactin level after an epileptic attack is of no significant value in differential diagnosis between epileptic and vaso-vagal syncopal attacks. (+info)