Evolution of patients with clinical neurocardiogenic (vasovagal) syncope not subjected to specific treatment

Potential consequences of cardioneuroablation for vasovagal syncope: A call for appropriately designed, sham-controlled clinical trials

Cardioneuroablation (CNA) is being increasingly used to treat patients with vasovagal syncope (VVS). Bradycardia, in the cardioinhibitory subtype of VVS, results from transient parasympathetic overactivity leading to sinus bradycardia and/or atrioventricular block. By mitigating parasympathetic overactivity, CNA has been shown to improve VVS symptoms in clinical studies with relatively small sample sizes and short follow-up periods (<5 years) at selected centers. However, CNA may potentially tip the autonomic balance to a state of sympathovagal imbalance with attenuation of cardiac parasympathetic activity. A higher heart rate is associated with adverse cardiovascular events and increased mortality in healthy populations without cardiovascular diseases. Chronic sympathovagal imbalance may also affect the pathophysiology of spectra of cardiovascular disorders including atrial and ventricular arrhythmias. This review addresses potential long-term pathophysiological consequences of CNA for VVS.

Are women really more affected by vasovagal syncope than men?

It is commonly reported that vasovagal syncope (VVS) is more frequent in women. Presently, this issue has never been investigated. The purpose of this review was to evaluate, through an extensive review of the literature, whether women are really more affected by VVS than men. The gender distribution was investigated in individuals with classical and nonclassical VVS. The database PubMed was searched using the terms 'syncope', 'vasovagal syncope', 'neurally mediated syncope' and 'tilt testing'. Twelve studies dealing with classical and 75 with nonclassical VVS were eligible. In the individuals with classical (N = 1861) and nonclassical VVS (N = 9696), a trend towards a greater percentage of women emerged (P = 0.14 and 0.07, respectively). In the total population with VVS (N = 11 557), the percentage of women was significantly higher than that of men (58 versus 42%, P = 0.03). Most of the individuals were young or middle-aged. In 84% of the studies, the percentage of women was greater than that of men. A separate analysis was carried out in older VVS patients (≥60 years) and only two studies were eligible to be evaluated. Considering that almost all the studies were carried out in the western nations, where the number of men and women is almost superimposable until the age of 65 years and a bias by gender has never been reported in the management of VVS, these data strongly suggest that young and middle-aged women are more affected by VVS than their male counterparts. At present, data are too scant to draw a definitive conclusion in older VVS patients.

Renal nerve stimulation for treatment of neurocardiogenic syncope: a review from perspective of commercialization potential

A strong evidence of outcomes for vasovagal syncope is not easily identified. It would seem reasonable that the proposed Mayo Clinic technology would be reserved for cases with severe recurrent or refractory syncope. However, recurrence levels are relatively low, and while some predictive methods have been proposed, recurrence is also influenced by the interaction that occurs during screening and examinations, i.e. recurrence diminishes once an initial diagnosis has been made. Finally, a key factor in being able to identify suitable patients relates to understanding the relative significance of the vasodepression and cardioinhibitory components-the therapy is best suited to patients that have a significant level of both components. It is probably not needed in patients with mainly cardioinhibitory involvement-data from ISSUE 2 and ISSUE 3 studies suggest that this is a relatively large proportion, particularly with asystolic involvement. The challenge remains in having suitable screening tests to identify the best patients. Tilt table testing has questions concerning its ability to replicate clinical syncope-implantable loop recorders (ILRs) may provide more accurate data but their usage is not yet widely accepted given the costs and invasive nature of the monitor.

Comparison of recurrence rate based on the frequency of preceding symptoms in patients with neurocardiogenic syncope or presyncope

BACKGROUND AND OBJECTIVES

In patients with neurocardiogenic syncope or presyncope, symptoms developed unpredictably and intermittently. The purpose of this study was to determine whether there was any significant difference in the recurrence rate of symptoms during the follow-up period between patients with many episodes of symptoms and those with fewer episodes of symptoms before diagnosis, as well as to assess the clinical significance of previous episodes of symptoms during treatment.

SUBJECTS AND METHODS

A total of 100 patients with neurocardiogenic syncope or presyncope were divided in two groups (high episode group, n=54; low episode group, n=46) according to the frequency of symptoms before the head-up tilt test. We retrospectively analyzed the recurrence of symptoms using telephone interviews and medical record reviews.

RESULTS

The clinical characteristics were not significantly different between the two groups. However, the recurrence rate was significantly lower in the high episode group than in the low episode group (5.6% vs. 19.6%, p=0.001). In the high episode group, patients treated with medication showed higher recurrence of symptoms than those without medication. In the lower episode group, a similar result was observed.

CONCLUSION

The frequency of previous symptoms at the diagnosis of neurocardiogenic syncope or presyncope did not predict the occurrence of symptoms during the follow-up period. Therefore, to continue drug treatment based on the frequency of symptoms in patients with neurocardiogenic syncope or presyncope may not be the best option.

Clinical factors associated with quality of life in patients with transient loss of consciousness

INTRODUCTION

Transient loss of consciousness (TLOC) is common and can be lethal. Although the patients with the most prevalent causes of TLOC have a benign prognosis, morbidity is considerable. Aim of this article, therefore, was to compare the generic quality of life (QoL) of patients presenting with TLOC with that of the general population, to compare the disease-specific QoL with that of an American referral sample, and to examine which sociodemographic and clinical factors are associated with QoL in these patients.

METHODS

This study was part of the fainting assessment study (FAST), which assessed diagnostic strategies for adult patients presenting with TLOC to the Academic Medical Center Amsterdam, between February 2000 and May 2002. The generic short form-36 (SF-36) health survey and the disease-specific syncope functional status questionnaire (SFSQ) were used to assess QoL.

RESULTS

Of 468 included patients, 82% completed the questionnaires. Patients with TLOC scored poorer on all scales of the SF-36 than the Dutch population, with effect sizes ranging from 0.43 to 1.11 (>0.5 = moderate effect; >0.8 = large effect). The SFSQ indicated mean impairment in 33% of the listed activities (such as driving). Female gender, higher level of comorbidity, shorter duration of complaints, having had more than one syncopal episode, and the presence of presyncopal episodes were associated with poorer QoL.

CONCLUSION

TLOC seriously affects QoL, especially in patients with a recent onset of clinical symptoms and those suffering from both syncopal and presyncopal episodes.

Long-term outcome of patients with vasovagal syncope

BACKGROUND

After abnormal head-up tilt test (HUT), several trials have evaluated treatment strategies for vasovagal syncope (VVS). However, few unequivocal results have been obtained. The aim of the study was to prospectively analyze the natural history of patients with VVS who did not undergo specific treatment but received education for avoiding syncope after an abnormal HUT.

METHODS

From 1996, 334 consecutive patients with VVS and an abnormal HUT result were followed. All of them received education for avoiding syncope as first-line therapy.

RESULTS

During 30.4 +/- 21 months, there were no cardiac deaths. However, 101 patients (30.2%) had recurrences (1 recurrence, n = 64; > or =2, n = 37), which were not influenced by the type of response during HUT or by age. Time to first recurrence was correlated with the number of recurrences (r: -0.34, P =.0001). Mean recurrence-free time was 50.1 months (95% CI 46-54) and the cumulative probability of no recurrence was 69.8%. Receiver operator character curve analysis, demonstrated significant differences in the recurrence rate between patients with <5 or > or =5 previous episodes of syncope (25.1% vs 44%; P =.001). In addition, the mean recurrence-free time of patients with <5 episodes was significantly longer (54.1 months) than in patients with > or =5 episodes (39.6 months; P =.0005). Multivariate logistic regression identified the previous number of episodes as an independent risk marker of recurrences (odds ratio 2.34, 95% CI 1.4-3.8, P =.001). Age (at HUT performance) as a continuous variable was not a predictor of outcome.

CONCLUSIONS

Survival of patients with VVS presenting after an abnormal HUT is excellent. Although the broad majority of those patients do not suffer recurrences after education, the number of previous syncopal episodes critically influences the recurrence rate.

Drug treatment of orthostatic hypotension because of autonomic failure or neurocardiogenic syncope

Orthostatic hypotension either because of autonomic failure or neurocardiogenic syncope can be very incapacitating and should be treated accordingly. Drug therapy is frequently needed to alleviate orthostatic symptoms. The physiopathological basis of neurocardiogenic syncope and of autonomic failure is completely different and their treatment should be distinct. In the past 5 years, many randomized, placebo-controlled trials have shed light on the efficacy of specific pressor drugs. In patients with orthostatic hypotension because of autonomic failure, alpha-adrenoceptor agonists, and midodrine in particular, have been shown to increase standing blood pressure and decrease orthostatic symptoms. Other drugs such as octreotide, indomethacin or ergotamine have also been shown to elevate standing blood pressure and/or orthostatic tolerance. Fludrocortisone is a well known and frequently used pressor drug but randomized controlled studies are needed to measure its efficacy. In patients with orthostatic hypotension associated with neurocardiogenic syncope, clinical trials have demonstrated that beta-blockers, especially beta(1)-selective agents without intrinsic sympathomimetic activity such as atenolol, midodrine and paroxetine can decrease recurrence of syncope. Treatment algorithms, such as those presented in this review, should always be interpreted in the light of individual patient characteristics. Many of the drugs used for orthostatic hypotension have multiple indications and contraindications that should influence therapeutic decisions. Little is known about the effectiveness and tolerability of specific combinations of pressor drugs. Consequently, sound clinical judgment and close follow-up of patients should always guide combination therapy.

Long-term outcome of patients with recurrent syncope of unknown cause in the absence of organic heart disease and relation to results of baseline tilt table testing

Among 123 patients with unexplained syncope in the absence of heart disease who were followed up for 24 +/- 7 months, syncope recurred in a similar minority of them regardless of baseline tilt table testing results. An initially unsuspected cardiac or neuropsychiatric disorder was uncovered in 17 patients later on follow-up examination.

Insulin sensitivity in young women with vasovagal syncope

BACKGROUND

Insulin, in addition to its known metabolic effects, has sympatho-excitatory and vasodilatory actions on muscular blood vessels. The goal of this study was to evaluate insulin sensitivity in young women with vasovagal syncope and positive tilt test results (HUT+) and to compare it with that in patients with negative tilt test results (HUT-) and in control subjects without a history of syncope.

METHODS

Different indices of insulin sensitivity were obtained by an oral glucose tolerance test (OGTT) in 13 young women with syncope and HUT+ (age 26.8 +/- 9.1 years, body mass index 20.4 +/- 2.1), 8 patients with HUT- (age 26 +/- 5.6 years, body mass index 21.9 +/- 2.4), and 13 control subjects without syncope and HUT- (age 28.9 +/- 8.8 years, body mass index 23.1 +/- 1.7). The following parameters were assessed: fasting glucose and insulin levels (G(0), I(0)); G(0)/I(0) ratio; G(0) x I(0); areas under the curve for glucose and insulin; homeostatic model assessment (HOMA); quantitative insulin sensitivity check index (QUICKI); and composite whole-body insulin sensitivity index (ISI).

RESULTS

G(0) and I(0) values were significantly lower in patients with HUT+ than in control subjects (G(0) 4.9 vs 81.9, P <.05, I(0) 4.7 vs 9.1, P <.005). All the fasting values-based indices (ie, HOMA 0.9 vs 1.9, P <.005) and the ISI (12.8 vs 7.1, P =.01) differed significantly in both groups. None of the parameters showed significant differences between patients with HUT- and control subjects. Sixty-one percent of patients with HUT+ had a vasovagal reaction during OGTT.

CONCLUSIONS

Young women with vasovagal syncope and HUT+ have a greater insulin sensitivity. They have a propensity to reproduce symptoms during the OGTT. This hypersensitivity could be one of the predisposing factors for vasovagal episodes.

[Vasovagal syncope in pediatric patients: a medium-term follow-up analysis]

INTRODUCTION AND OBJECTIVES

Little information is available on the evolution of pediatric patients with vasovagal syncope. We therefore aimed to assess the medium-term clinical outcome of children evaluated by tilt testing for syncope of unknown origin.

PATIENTS AND METHOD

Fifty-one children under 17 years of age who had undergone tilt testing were identified from a data base and studied prospectively. Kaplan-Meier and Cox regression analyses were performed to estimate syncope-free survival, its predictors, and the relative risks of several patient subgroups.

RESULTS

Forty-seven (92%) of the children were followed for a mean 21 9 months. The rate of recurrence of syncope was considerably lower than that estimated during history taking before the tilt test (19% vs 47%; p < 0.01). Although the low rate made it difficult to identify predictors, several potential predictors emerged from the multivariate analysis. Only the history of more than one syncope before the tilt test (vs. isolated syncope) was found to have independent predictive value (p = 0.04). The cumulative probability of recurrence projected for a period of 38 months was 66.2% (SEM = 16.5%) for children with more than one syncope before testing vs. 0% for those who had experienced only one. No other events occurred.

CONCLUSIONS

The medium-term prognosis seems to be good for children with vasovagal syncope of unknown origin, given the low rate of recurrence, regardless of the results of tilt testing. The only predictor of recurrent syncope was pretest history, such that children with only one syncope before testing experience no recurrence and those with one or more episodes are estimated to have an increasingly higher likelihood of recurrence. These data may be useful for the recommending tilt testing and for planning therapy for children with vasovagal syncope.

Evaluation and treatment of pediatric patients with neurocardiogenic syncope

Neurocardiogenic syncope is the most common form of syncope in children. The most widely accepted mechanism of its etiology is a vigorous contraction of the heart due to relative hypovolemia leading to stimulation of C-fibers and sympathetic withdrawal. Episodes usually occur with an upright position and are preceded by a typical prodrome. A classic history is paramount to the diagnosis. Tilt testing aids in the diagnosis in certain cases. The cornerstone of therapy is maintaining adequate hydration and avoiding situations that may lead to harm with syncopal events. Beta blockers, fludrocortisone, alpha adrenergic agents and disopyramide are commonly used to prevent syncope. Seratonin reuptake inhibitors, pacing with rate drop algorithms and tilt training are relatively new in the armamentarium of therapy.

Diagnostic evaluation and management of patients with syncope

This article focuses on the evaluation of patients with syncope, a symptom not a disease. Syncope is a transient loss of consciousness associated with loss of postural tone with spontaneous recovery. The authors discuss the utility of an indications for different diagnostic tests, the indications for hospital admission, and the management of patients with certain known causes of syncope, including vasovagal and arrhythmic.

Formal analysis of the optimal duration of tilt testing for the diagnosis of neurally mediated syncope

BACKGROUND

Although tilt testing has emerged as the test of choice for assessing patients with suspected neurally mediated syncope, the optimum duration of tilt testing is poorly defined. This in part relates to the absence of a gold standard to assess test performance.

OBJECTIVE

Our purpose was to formally estimate the effects of varying duration of drug-free tilt testing on test performance in diagnosing neurally mediated syncope.

DESIGN

If a test's specificity is known, then in the absence of a gold standard an imputed (estimated) sensitivity may be calculated on the basis of the observed diagnostic yield in a given population as a function of assumed population prevalence. We determined the relationship of specificity to drug-free tilt test duration by use of data from 11 previous studies reporting the results of drug-free tilt testing in a total of 435 control subjects (60 to 80 degrees of tilt, footboard support, 15- to 60-minute duration). Data (weighted for study size) were fit to an exponential function relating specificity to tilt duration. Test yield was evaluated as a function of tilt duration in 213 consecutive patients referred to our laboratory for the evaluation of suspected neurally mediated syncope who underwent passive tilt testing for up to 30 to 60 minutes.

RESULTS

The estimated specificity of tilt testing was 94% at 30 minutes, 92% at 40 minutes, and 88% after 60 minutes of passive tilt. The cumulative yield of tilt testing was only 17% at 30 minutes, 22% at 40 minutes, and 28% after 60 minutes. On the basis of an estimated population prevalence of 25% to 50% in this referral population, imputed sensitivity is 27% to 48% at 30 minutes, 36% to 64% at 40 minutes, and 43% to 74% after 60 minutes of passive tilt. The overall diagnostic accuracy was not strongly influenced by tilt duration beyond 30 minutes and ranged from 60% to 84%.

CONCLUSIONS

Passive tilt testing (ie, tilt testing without pharmacologic provocation) for durations of up to 60 minutes has limited sensitivity for diagnosing neurally mediated syncope. For populations with a pretest likelihood of 25% to 50%, test results are inaccurate in one to two fifths of patients.

Intravenous nitrates for pharmacological stimulation during head-up tilt testing in patients with suspected vasovagal syncope and healthy controls

Nitrates may be used for pharmacological stimulation during tilt testing for the diagnosis of vasovagal syncope. In this study we assessed the diagnostic value of intravenous nitrates during tilt testing in patients with a typical history of vasovagal syncope. Twenty patients and 23 controls were tilted at 700 for a maximum duration of 30 minutes. After a 10-minute baseline supine phase, the test started with a continuous nitrate infusion at 1 microg/kg/min and increased every 5 minutes by 1 microg/kg/min, to a maximum of 6 microg/kg/min at the end of the test. The test was ended if the subjects developed a positive response (syncope or presyncope). Nineteen patients (95%) and 17 (74%) of the controls had a positive response. At test end sensitivity was 95%, but specificity was 26% and accuracy was 58%. Receiver operator characteristics (ROC) analysis revealed a maximum accuracy of 79% at 18 minutes, with a sensitivity of 80% and a specificity of 78%. Intravenous nitrates during tilt testing in patients with typical clinical criteria of vasovagal syncope is highly effective in provoking vasovagal syncope. Based on the ROC analysis, a maximum accuracy of 79% was attained at 18 minutes (at a dose of 4 microg/kg/min), suggesting a good diagnostic performance when tilt duration is limited to this point. A positive result requiring more than 18 minutes of stimulated tilting should be interpreted with caution, due to the accompanying considerable decrease of specificity.

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.

Multiscale analysis of blood pressure signals

We describe the multiresolution wavelet analysis of blood pressure waves in vasovagal syncope-affected patients compared with those in healthy people, using Haar and Gaussian bases. A comparison between scale-dependent and scale-independent measures discriminating the two classes of subjects is made. What emerges is a sort of equivalence between these two methodological approaches, that is, both methods reach the same statistical significance of separation between the two classes.

Neurohormonal profile before and after beta-blockade in patients with neurocardiogenic syncope

Our objective was to evaluate the effects of beta-blockers on the neurohormonal profile, particularly vasopressin (VP) release, in vasovagal syncope and to gain further insight on the pathophysiology of this syndrome. Patients (< or =75 years) with no cardiovascular, neurological disorders, or contraindications to the use of isoproterenol or beta-blockers and being explored for unexplained syncope were included. An 80 degrees HUT was performed under identical conditions. After a 25-min period of passive tilt, isoproterenol was infused at a rate of 1-5 microg/mn if required. Two groups matched for age and sex were considered: a HUT-positive and a HUT-negative group. The HUT-positive group was then given beta-blockers, subsequently reassessed, and divided into two subgroups: alpha beta-blocker nonresponder group and a beta-blocker responder group. Blood samples for assays of norepinephrine (NE), epinephrine (E), and VP were taken at baseline and the end of the procedure. In all, 44 subjects entered the study, 22 in each group. The HUT-positive group exhibited an obvious lesser increase in plasma NE and a clear-cut rise in plasma E and VP compared to the HUT-negative group (P < 0.05). Even though no patient in the HUT-positive group reported recurrent symptoms under treatment, the second HUT could distinguish two subgroups: a beta-blocker nonresponder group (n = 12) whose HUT remained positive and a beta-blocker responder group (n = 10) whose HUT was normalized. The time course of plasma E and VP during the second HUT was similar to that for the HUT-positive and HUT-negative groups. In conclusion, the efficacy of beta-blockers is associated not only with a reduction of the sympathoadrenal stimulation seen in vasovagal syncope but also with a lower release of VP suggesting that low-pressure baroreceptors might be involved in VP release.

[Long-term prognosis of patients with syncope of unknown origin in prolonged asystole induced by the head-up tilt test]

INTRODUCTION AND OBJECTIVES

Prognosis and therapeutic assessment of patients with syncope and prolonged asystole during head-up tilt test remain unclear. The aim of the present study was to analyze the clinical evolution of patients with syncope of unknown origin, no heart disease and severe cardioinhibitory response induced by head-up tilt.

METHODS

A prospective follow-up study was performed in 12 patients (6 male and 6 female, mean age 31 +/- 20 years) with recurrent syncope, no heart disease and affected by severe cardioinhibitory syncope induced by head-up tilt test. This was defined as syncope or near-syncope induced by baseline or isoproterenol tilt with asystole of > or = 3 seconds. All patients were re-tilted twice: with salt and fluid and with metoprolol (25 mg/b.i.d). According to the results of these tests, 5 patients were discharged with dietetic measures (salt & fluid) and 5 with metoprolol. In 2 patients who showed recurrent prolonged asystole a DDD pacemaker was implanted.

RESULTS

After follow-up of 34 +/- 20 months all patients ae alive. The number of recurrences was small (2 syncopes and 2 near-syncopes). No relationship was observed between the number of syncopal recurrences and the applied treatment.

CONCLUSIONS

We conclude that prolonged asystole induced by head-up tilt test does not confer an adverse prognosis in patients with syncope of unknown origin and no heart disease, thus, the clinical evolution of these patients is benign.

Head-up tilt test. A nonspecific method of evaluating patients with bifascicular block

BACKGROUND

Patients with bifascicular block have an increased risk of syncopal attacks, but the underlying mechanism often remains unclear despite an extensive diagnostic workup. The head-up tilt test has been established as an important diagnostic tool in the unmasking of vasovagal syncope in patients with unexplained syncope. Its role in the evaluation of patients with bifascicular block has not been studied.

METHODS AND RESULTS

A head-up tilt test, using a 60 degrees angle of tilt for 45 minutes without pharmacological provocation, was performed in 25 patients with bifascicular block and syncope that remained unexplained after an extensive invasive and noninvasive electrophysiological investigation. As a control group, 25 subjects with bifascicular block without syncope, matched for age, sex, left ventricular function, and underlying heart disease, were included. A positive head-up tilt test was found in 7 (28%) of the syncope patients and in 8 (32%) of the control subjects (P = NS). Six patients, of whom 3 had a positive tilt test, had recurrent syncopal attacks during 32 months of follow-up. None of the control subjects had syncope during follow-up.

CONCLUSIONS

This study gives rise to serious concern regarding the specificity of the head-up tilt test in patients with bifascicular block. A head-up tilt test should therefore be interpreted with caution, and its role as a diagnostic tool in this patient category remains to be established.