Dual chamber pacing aborts vasovagal syncope induced by head-up 60 degrees tilt

Pacing Therapies for Vasovagal Syncope

Vasovagal Syncope (VVS) is mediated by a cardiac autonomic reflex with resultant bradycardia and hypotension, precipitating syncope. While benign and mostly well controlled, recurrent VVS can be debilitating and warrants intervention. Non-pharmacological management of VVS have had variable success. In patients with recurrent cardioinhibitory VVS, permanent pacing can be effective. The utility of pacing to preempt the syncopal depends on the prominent temporal role of bradycardia during the vasovagal reflex. Current guidelines recommend pacing as a therapy to consider in older patients with recurrent VVS. Although younger patients can benefit, one should be cautious given the long-term risk of complications. Available data appears to favor a dual chamber pacemaker with closed loop stimulation algorithm to prevent recurrent cardioinhibitory VVS. Several aspects, including mechanistic understanding of VVS and appropriate patient selection, remain unclear, and require further study.

Pacing for Vasovagal Syncope

Vasovagal syncope (VVS) is due to a common autonomic reflex involving the cardiovascular system. It is associated with bradycardia (cardioinhibitory response) and/or hypotension (vasodepressor response), likely mediated by parasympathetic activation and sympathetic inhibition. While generally a situational, isolated and/or self-limited event, for some, VVS is recurrent, unpredictable and debilitating. Conservative, non-pharmacological management may help, but no specific medical therapy has been proven widely effective. Permanent pacing may have specific benefit, but its value has been debated. The temporal causative association of bradycardia with syncope in those with VVS may help identify which patient could benefit from pacing but the timing and type of pacing in lieu of blood pressure changes may be critical. The mode, rate, pacing algorithm and time to initiate dual-chamber pacing preferentially with respect to the vasovagal reflex may be important to prevent or ameliorate the faint but completely convincing data are not yet available. Based on available data, DDD pacing with the closed loop stimulation algorithm appears a viable, if not the best, alternative presently to prevent recurrent VVS episodes. While several knowledge gaps remain, permanent pacing appears to have a role in managing select patients with VVS.

Should we treat severe vasovagal syncope with a pacemaker?

Cardiac pacing for vasovagal syncope (VVS) addresses the cardioinhibitory component of the reflex but cannot directly affect vasodepression, which occurs in every reflex even when hidden by dominant cardioinhibition. The randomized controlled trials of pacing in VVS have, after almost 2 decades, determined that a small number of patients can benefit because their vasodepressor component is not severe. Early studies compared pacing with no therapy yielding highly significant benefits. Subsequently, all study patients had implanted devices with half being switched off. No benefit was seen. The ISSUE-3 study found significant benefit (P < 0.039) in prevention of syncope recurrence in older patients. A sub-study later showed those with negative tilt tests, otherwise indistinguishable from tilt-positives, had 5% recurrence in 21 months (P < 0.004). There is acceptance that pacing must be dual chamber, but the question of how pacing is delivered remains open. Relying on falling heart rate is insufficient, probably because it occurs too late. Other algorithms which indirectly detect neuroendocrine changes earlier than heart rate fall may have useful application. In clinical terms, the patient to be considered for pacing should not be young and have severe symptoms. Ideally, tilt testing should be negative implying vasodepression of lesser severity and, therefore, yielding fewer syncope recurrences. When selecting pacing, additional concern must be given to regression to the mean of symptoms, severe to less severe. Patients seek help when they are at their worst. Moreover, many years of pacing are unlikely to be free of complications related to implanted hardware.

Pacemaker therapy in syncope

The current evidence for pacemaker therapy is reviewed in 2 different syncopal conditions: reflex syncope with cardioinhibitory response and syncope in patients with bundle branch block. Although recent trials support the use of pacemaker therapy in selected patients with reflex syncope in whom an asystole is documented during spontaneous syncope or in whom an asystole is provoked with adenosine-5'-triphosphate administration, the best strategy in these patients and in those with syncope and bundle branch block is not well established. Ongoing clinical trials will answer this question.

Hemodynamic significance of heart rate in neurally mediated syncope

BACKGROUND

Vasovagal and vasodepressor syncope are used interchangeably in the literature to describe the common faint syndrome, now collectively named neurally mediated syncope. The significance of heart rate (HR) in these reflex-induced reactions remains unclear.

HYPOTHESIS

The study was undertaken to investigate the hemodynamic significance of HR in tilt-induced neurally mediated syncope.

METHODS

In all, 113 patients with syncope of unknown etiology were studied by head-up tilt test with invasive hemodynamic monitoring. Thirty-five patients (15 women, 20 men, age range 21 to 72 years) developed syncope and were enrolled for analysis. The hemodynamic data were compared between patients who developed bradycardia (vasovagal group, n = 15) and those without bradycardia (vasodepressor group, n = 20).

RESULTS

The baseline hemodynamic data (mean +/- standard deviation) and the hemodynamic responses after 10-min headup tilt were similar between patients in the vasovagal and vasodepressor groups. During syncope, patients with vasovagal reaction developed hypotension and paradoxical bradycardia (HR = 52.4 +/- 5.9 beats/min), while patients with vasodepressor reaction developed a precipitous drop in arterial blood pressure with inappropriate HR (105 +/- 21 beats/min) compensation. Patients with vasovagal syncope manifested a significantly lower cardiac index and a significantly higher systemic vascular resistance index than patients with vasodepressor syncope (1.47 +/- 0.29 vs. 1.97 +/- 0.41 1/min/m2, p < 0.001 and 2098 +/- 615 vs. 1573 +/- 353 dynes x s x cm(-5) x m2, p < 0.003, respectively). A positive correlation existed between HR and cardiac index (r = 0.44, p = 0.008) during syncope in the patients studied.

CONCLUSIONS

These findings suggest that the hemodynamic characteristics of vasovagal and vasodepressor reactions are different, and that HR plays a significant role in neurally mediated syncope.

Permanent cardiac pacing as primary therapy for neurocardiogenic (reflex) syncope

Recurrent reflex (or neurocardiogenic) syncope is a common clinical problem. Pacemaker therapy has been advocated as a potential therapy in severe or drug refractory cases of reflex syncope, while others have suggested that it may provide a benefit if employed as a primary therapeutic modality. The following paper reviews the concepts behind pacemaker therapy for reflex syncope and the results of various clinical trials that have evaluated its potential utility as a primary therapeutic modality.

Role of pacemakers in treating neurocardiogenic syncope

Patients with frequent vasovagal syncope have a poor quality of life and often resist treatment with standard pharmacologic approaches. Clinical vasovagal syncope may be associated with some degree of bradycardia. Studies of temporary pacing during tilt table tests showed that pacing prevented syncope in a little more than half of patients who developed a vasovagal response. Six open-label studies of permanent pacing show that permanent pacemaker therapy is associated with substantial improvement over medical therapy. The roles of specific pacemaker modes have not been determined, although there is some evidence that rate-drop responsiveness helps. The second Vasovagal Pacemaker Study will quantify the true benefits of pacing for vasovagal syncope and assess the role of rate-drop response algorithms.

Strategy for the management of vasovagal syncope

The disorders of autonomic control associated with orthostatic intolerance are a diverse group of syndromes that can result in syncope and near-syncope. A basic understanding of the pathophysiology of these disorders is essential to diagnosis and proper treatment. It is especially important to recognise the difference between the effect of prolonged upright posture on a failing autonomic nervous system (a hyposensitive or dysautonomic response) and the vasovagal response (which may be a hypersensitive response). Vasovagal syncope is the most common abnormal response to upright posture and occurs in all age groups. The advent of tilt table testing has helped define a population with an objective finding during provocative testing that has enabled researchers to study the mechanism of vasovagal syncope and to evaluate the efficacy of treatments. In most patients, vasovagal syncope occurs infrequently and only under exceptional circumstances and treatment is not needed. Treatment may be indicated in patients with recurrent syncope or with syncope that has been associated with physical injury or potential occupational hazard. Based on study data, patients with vasovagal syncope can now be risk stratified into a high-risk group likely to have recurrent syncope and a low-risk group. Many patients with vasovagal syncope can be effectively treated with education, reassurance and a simple increase in dietary salt and fluid intake. In others, treatment involves removal or avoidance of agents that predispose to hypotension or dehydration. However, when these measures fail to prevent the recurrence of symptoms, pharmacological therapy is usually recommended. Although many pharmacological agents have been proposed and/or demonstrated to be effective based on nonrandomised clinical trials, there is a remarkable absence of data from large prospective clinical trials. Data from randomised placebo-controlled studies support the efficacy of beta-blockers, midodrine, serotonin reuptake inhibitors and ACE inhibitors. There is also considerable clinical experience and a consensus suggesting that fludrocortisone is effective. Encouraging new data suggest that a programme involving tilt training can effectively prevent vasovagal syncope. For patients with recurrent vasovagal syncope that is refractory to these treatments, implantation of a permanent pacemaker with specialised sensing/pacing algorithms appears to be effective. A number of larger clinical trials are underway which should help further define the efficacy of a number of different treatments for vasovagal syncope.

Neurally mediated syncope

The prevalence and incidence of syncope increases with advancing years due to age related physiological changes in the neurocardiovascular, endocrine and renal systems. Cardiovascular syncope can present as falls because of amnesia for loss of consciousness or postural instability due to hypotension. Drop attacks or non accidental falls should thus be investigated for causes of syncope. The most common causes of neurally mediated syncope in older adults are carotid sinus syndrome, orthostatic hypotension and vasovagal syncope.

Neurocardiogenic syncope: aetiology and management

Neurocardiogenic syncope is the most common cause of syncope presenting in the outpatient setting. It is usually encountered among individuals without an underlying heart disease, but not uncommonly participates in the syncope mechanism of patients with an obstructive or an arrhythmic cardiac cause for syncope as well. The vasovagal event is caused by a transient profound hypotensive reaction most commonly associated with inappropriate bradycardia resulting from activation of a complex autonomic reflex. The pathophysiology of neurocardiogenic syncope has been elucidated by tilt table testing, a noninvasive and well-tolerated method for reproducing the event in susceptible individuals. Although the majority of people with vasovagal fainting need no specific treatment, treatment is required for those presenting with problematic features such as frequent events accompanied by trauma or accidents, and occasionally by a severe cardioinhibitory pattern response. A number of different drugs have been proposed to favourably act on different aspects of the neurocardiogenic reflex but only a few randomised, placebo-controlled, drug-specific trials are currently available. Alternatively, cardiac pacing has also been introduced for patients who have symptoms that are drug-refractory or for those with a severe cardioinhibitory hypotensive response. The selection of the appropriate treatment plan should be individualised after consideration of patient history, clinical characteristics and preference, results of the baseline tilting study, and the existing evidence from the few randomised, controlled studies performed so far.

How and when to pace in vasovagal syncope

This article discusses the indications for pacing in vasovagal syncope. It also reviews the literature on pacing results; notably, there are two small randomized controlled trials of pacing versus no therapy (or continued nondevice therapy) that show a clear benefit for pacing. The mode of benefit is, as yet, unclear. Pacing has to be dual chamber with some form of rate hysteresis. Ways of improving pacemaker therapy delivery in vasovagal syncope are anticipated.

Permanent cardiac pacing to prevent vasovagal syncope

Patients with frequent vasovagal syncope have a poor quality of life and often resist treatment with standard pharmacologic approaches. Although the evidence is weak, clinical vasovagal syncope is probably associated with some degree of bradycardia. Studies of temporary pacing during tilt table tests showed that pacing prevented syncope in a little over half of patients who developed a vasovagal response. Six open-label studies of permanent pacing show that permanent pacemaker therapy is associated with substantial improvement over medical therapy. The roles of specific pacemaker modes have not been determined, although there is some evidence that rate-drop responsiveness helps. The second Vasovagal Pacemaker Study will quantify the true benefits of pacing for vasovagal syncope and assess the role of rate-drop response algorithms.

Emerging indications for cardiac pacing

Substantial data have been accumulated and indications have been well delineated for pacemaker implantation in the treatment of sinus node dysfunction and heart block. However, many other indications have been proposed for pacemaker implantation. In this review, the authors examine available data regarding pacemaker implantation for new indications: neurally mediated syncope, hypertrophic obstructive cardiomyopathy, congestive heart failure, prevention of atrial fibrillation, and the relative merits of single-chamber and dual-chamber pacemakers.

Cardiac pacing. A review

Pacing is a field of rapid clinical progress and technologic advances. Clinical progress in the 1990s included the refinement of indications for pacing as well as the use of pacemakers for new, nonbradycardiac indications, such as the treatment of cardiomyopathies and CHF and the prevention of atrial fibrillation. Important published data and studies in progress are shedding new light on issues of pacing mode selection, and they may influence future practice significantly. Important technologic advances include development of new rate-adaptive sensors and sensor combinations and the evolution of pacemakers into sophisticated diagnostic devices with the capability to store data and ECGs. Automatic algorithms monitor the patient for appropriate capture, sensing, battery status, and lead impedance, providing better patient safety and pacemaker longevity.

Syncope in the elderly: new trends in diagnostic approach and nonpharmacologic management

Syncope in the elderly is an important health care issue because of the large patient population, challenging diagnostic and therapeutic approaches, and potentially devastating consequences. Significant comorbidity and atypical clinical presentations render a precise determination of the cause of syncope difficult. Recent studies suggest that noninvasive tests, such as carotid sinus massage or tilt-table testing, can be helpful in the diagnostic workup. It has been shown that permanent pacemaker therapy benefits elderly patients with carotid sinus hypersensitivity, and younger patients with recurrent vasovagal syncope. The implantable wireless loop recorder can be effective in documenting transient arrhythmias as causes of syncope in selected patients. Elderly patients with syncope and a low ejection fraction are at increased risk of sudden death due to malignant ventricular arrhythmia. Electrophysiologic study and electrophysiology-guided therapy should be considered in this segment of the population.

Treatment of vasovagal syncope: pacemaker or crossing legs?

A 50-year-old male patient continued to experience syncope after implantation of a pacemaker. During cardiovascular examination, the patient showed a typical vasovagal response, with normal pacemaker function. Leg crossing, which prohibits the pooling of blood in the legs and abdomen, at the onset of symptoms helped to prevent this response. The authors recommend a course of leg crossing as a measure to treat vasovagal syncope.

Determining the optimal pacing intervention rate for vasovagal syncope

INTRODUCTION

In this study, patients with rate hysteresis pacemakers implanted for vasovagal syncope were re-studied using serial tilt testing to determine whether, once triggered, pacing was more effective if the intervention rate was higher than the standard rate.

METHODS AND RESULTS

Twenty patients (mean age 55.4 years, range 23-81, 14 male) were studied, with randomisation to either initial standard rate (80-90 beats/min) intervention, or to initial high rate (120 beats/min) intervention. Although 18 of the 20 reported complete abolition of syncope since pacing, only 8 patients could be objectively assessed. The respective mean time to tilt down after symptom onset with standard and high rate intervention was 193+/-234s and 185+/-143s, (P>0.05).

CONCLUSION

Repeat tilt testing was only of limited value in assessing the benefit of pacing. There was no advantage with high rate intervention in delaying the loss of consciousness (or intolerable symptoms) after the initial onset of symptoms.

Vasodepressor Syncope

Neurocardiogenic syncope is a common disorder affecting various individuals of different ages with a wide variety of circumstances and comorbid conditions. Although a large amount of data is available regarding evaluation and treatment options, there is still sufficient latitude for the physician to exercise clinical judgment. We summarize current opinions on treatment here and also add some of our own bias regarding how to manage such patients. The vast majority of patients can be assessed by a reduction of symptomatic episodes with therapy. In all patients, careful follow-up should be made after initiating therapy. Not all patients will obtain complete resolution of symptoms. If episodes of complete syncope are reduced to infrequent dizzy spells, however, this may be satisfactory. In other patients, abrupt syncope may be converted to spells with a sufficient prodromal warning for the patient to take evasive action.

Respiratory changes in vasovagal syncope

INTRODUCTION

Respiratory changes accompany the cardiovascular changes during head-up, tilt test-induced vasovagal syncope.

METHODS AND RESULTS

Using the 45-minute 60 degrees head-up Westminster protocol, 29 patients were studied (mean age 53.9+/-20.0 years; 19 females). Two groups resulted: tilt-induced vasovagal syncope positive and negative. The cardiorespiratory parameters blood pressure (BP), heart rate (HR), tidal volume, and minute volume were measured. Comparisons of the cardiorespiratory parameters were made within the positive group and negative group, and then between the two groups. There were 14 in the positive group and 15 in the negative group. Baseline measurements were normalized to 1.0. Comparing the late tilt periods between the positive and negative groups, there were differences in BP (P < 0.002), HR (P < 0.002), tidal volume (P < 0.05), and minute volume (P < 0.002). In the positive group comparing early with late intervals: BP 1.11+/-0.09 versus 0.49+/-0.17, P < 0.0001; HR 1.18+/-0.12 versus 0.85+/-0.35, P < 0.009; tidal volume 1.39+/-0.34 versus 2.17+/-1.00, P < 0.015; and minute volume 1.24+/-0.26 versus 3.3+/-2.03, P < 0.0025. There were no comparable cardiorespiratory changes in the negative group.

CONCLUSION

There were significant differences in the respiratory and cardiovascular parameters measured between those who were positive and those who were negative for tilt-induced vasovagal syncope. Within the positive group, in addition to the falls in HR and BP, there were significant increases in minute volume and tidal volume during late tilt. This suggests that there may be a role for respiratory sensors in vasovagal syncope that may permit earlier and hence possibly more effective therapy for selected patients.

Successful treatment of malignant neurocardiogenic syncope with repeated tilt training program

Recent reports have shown that repeated tilt-table testing or tilt training is a very effective therapy for the treatment of neurocardiogenic syncope induced by head-up tilt testing. The present patient experienced repeated syncopal or presyncopal attacks and had shown prolonged asystole on an electrocardiogram during syncope. The presyncope could be reproducibly induced by head-up tilt testing. Oral propranolol and/or disopyramide therapies failed to prevent his symptoms. Tilt training (2 sessions/day) was repeated every day for 4 weeks at home, and then head-up tilt testing was performed again. The syncope or presyncope was not induced by head-up tilt testing. The patient has continued with this training and has had no symptoms during the follow-up period of 1 year.

Pacing to prevent vasovagal syncope

Patients with frequent vasovagal syncope have markedly poor quality of life and are often resistant to treatment with standard pharmacologic approaches. Vasovagal syncope is due to combinations of bradycardia and hypotension. There is accumulating evidence that many of these patients may respond to permanent cardiac pacing. Several controlled open-label studies suggest that about half of paced patients no longer faint, and most of the rest are improved. At this point, we do not know the role of placebo, and specific pacing modes in this improvement are not known. Ongoing trials will clarify how to select patients and how best to pace them.

Cardiac pacing for severe childhood neurally mediated syncope with reflex anoxic seizures

OBJECTIVE

To determine whether permanent cardiac pacing could prevent syncope and seizures in children with frequent severe neurally mediated syncope, and if so whether dual chamber pacing was superior to single chamber ventricular pacing.

METHODS

Dual chamber pacemakers were implanted into 12 children (eight male, four female) aged 2-14 years (median 2.8 years) with frequent episodes of reflex anoxic seizures and a recorded prolonged asystole during an attack. The pacemaker was programmed to sensing only (ODO), single chamber ventricular pacing with hysteresis (VVI), and dual chamber pacing with rate drop response (DDD) for four month periods, with each patient allocated to one of the six possible sequences of these modes, according to chronological order of pacemaker implantation. The parent and patient were blinded to the pacemaker mode and asked to record all episodes of syncope or presyncope ("near miss" events). The doctor analysing the results was blinded to the patient and pacemaker mode.

RESULTS

One patient was withdrawn from the study after the pacemaker was removed because of infection. In the remaining children, both dual chamber and single chamber pacing significantly reduced the number of syncopal episodes compared with sensing only (p = 0.0078 for both). VVI was as effective as DDD for preventing syncope, but DDD was superior to VVI in reducing near miss events (p = 0.016).

CONCLUSIONS

Permanent pacing is an effective treatment for children with severe neurally mediated syncope and reflex anoxic seizures. VVI is as effective as DDD in preventing syncope and seizures, but DDD is superior in preventing overall symptoms.

Role of pacing in the treatment of vasovagal syncope

Patients with frequent vasovagal syncope have a markedly poor quality of life and are often resistant to treatment by standard pharmacologic approaches. Although the evidence is not conclusive, clinical vasovagal syncope is probably associated with some degree of bradycardia. Studies of temporary pacing during tilt-table testing have shown that pacing prevents syncope in more than half of patients who develop a vasovagal response. Three open-label studies of permanent pacing showed that pacing was associated with substantial improvement, and the prospective randomized Vasovagal Pacemaker Study reported an 85% relative risk reduction in patients randomized to pacemaker therapy compared with medical therapy. The roles of specific pacemaker modes in vasovagal syncope have not been determined, although early evidence indicates that rate-drop responsiveness is useful. The second Vasovagal Pacemaker Study may clarify the role of rate-drop responsiveness.

Neurally Mediated Syncope

Syncope is a common problem in medical practice. Of the various types of syncope, the neurally mediated syncopal syndromes (of which vasovagal syncope is the most common) predominate. In most cases, neurally mediated syncope is a solitary event that can be managed with only reassurance, but certain patients (those with multiple recurrences or those who have been injured as a result of syncope) need further investigation and therapy. Dietary and lifestyle changes are crucial and often overlooked aspects of therapy that may be sufficient to control symptoms. Pharmacologic therapy, which usually starts with beta-blockers or fludrocortisone, can also be effective. Finally, certain patients may continue to have recurrences despite the use of both nonpharmacologic and pharmacologic therapy. It was recently demonstrated that permanent pacing may be effective in preventing recurrent syncopal episodes in some of these patients.

Dual chamber pacing for neurally mediated syncope with a prominent cardioinhibitory component

The role of cardiac pacing for treatment of recurrent neurally mediated syncope (NMS) remains controversial. We hypothesized that dual chamber pacing in NMS patients with a prominent cardioinhibitory component may be beneficial. Twelve patients (mean age = 37.8+/-17 years, range 15-78 years, 7 men and 5 women) with a mean of 4+/-2.2 episodes of syncope underwent tilt table evaluation. Patients were passively tilted to 70 degrees head-up position for 20 minutes and then returned to the supine position. Isoproterenol was then infused at 1-2 microg/min to increase heart rate by > or = 25% and tilt was repeated. Patients lost consciousness after 16+/-6 minutes of tilt; nine patients had syncope in the baseline state and three during isoproterenol infusion. All patients had at least 5 seconds of asystole with a mean of 9.5+/-4 seconds (range 5-20 s). A dual chamber permanent pacemaker with a special feature allowing heart rate acceleration in response to bradycardia was implanted in all patients. During a mean follow-up of 18.6+/-4.2 months, 11 (92%) of these patients were free of syncope and had negative tilt table test. One (8%) patient had two episodes of syncope. We conclude that dual chamber pacing may be beneficial in patients with NMS with a prominent cardioinhibitory component.

Management of vasovagal syncope

Vasovagal syncope is a common disorder of autonomic cardiovascular regulation that can be very disabling and result in a significant level of psychosocial and physical limitations. The optimal approach to treatment of patients with vasovagal syncope remains uncertain. Although many different types of treatment have been proposed and appear effective based largely on small nonrandomized studies and clinical series, there is a remarkable absence of data from large prospective clinical trials. However, based on currently available data, the pharmacologic agents most likely to be effective in the treatment of patients with vasovagal syncope include beta blockers, fludrocortisone, and alpha-adrenergic agonists. In this article, we provide a summary of the various therapeutic options that have been proposed for vasovagal syncope and review the clinical studies that form the basis of present therapy for this relatively common entity.

Contribution of head-up tilt testing and ATP testing in assessing the mechanisms of vasovagal syndrome: preliminary results and potential therapeutic implications

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.

"Rate-drop response" cardiac pacing for vasovagal syncope. Rate-Drop Response Investigators Group

Recent reports suggest that cardiac pacing incorporating a rate-drop response algorithm is associated with a reduction in the frequency of syncopal episodes in patients with apparent cardioinhibitory vasovagal syncope. The detection portion of the algorithm employs a programmable heart rate change-time duration "window" to both identify abrupt cardiac slowing suggestive of an imminent vasovagal event and trigger "high rate" pacing. The purpose of this study was to develop recommendations for programming the rate-drop response algorithm. Pacemaker programming, symptom status, and drug therapy were assessed retrospectively in 24 patients with recurrent vasovagal syncope of sufficient severity to warrant consideration of pacemaker treatment. In the 53 +/- 19 months prior to pacing, patients had experienced an approximate syncope burden of 1.2 events/month. During follow-up of 192 +/- 160 days, syncope recurred in 4 patients (approximate syncope burden, 0.3 events/month, p < 0.05 vs. pre-pacing), and pre-syncope in 5 patients. In these patients, rate-drop response parameters were initially set based on electrocardiographic and/or tilt-table recordings, and were re-programmed at least once in 14 (58%) individuals. A 20 beat/min window height (top rate minus bottom rate), a window width of 10 beats (61% of patients), and 2 or 3 confirmation beats (79% of patients) appeared to be appropriate in most patients. Treatment intervention rate was set to > 100 beats/min in 89% of patients, with a duration of 1 to 2 min in 79%. In conclusion, a narrow range of rate-drop response parameter settings appeared to be effective for most individuals in this group of highly symptomatic patients.

The North American Vasovagal Pacemaker Study (VPS). A randomized trial of permanent cardiac pacing for the prevention of vasovagal syncope

OBJECTIVES

This study was done to evaluate pacemaker therapy for severe recurrent vasovagal syncope.

BACKGROUND

Nonrandomized studies have suggested that permanent pacing might help control the symptoms of recurrent vasovagal syncope. The study goal was to evaluate the effect of permanent pacemaker implantation on syncope in patients with frequently recurrent vasovagal syncope.

METHODS

Patients with > or = 6 lifetime episodes of syncope and with a tilt-table test that induced syncope or presyncope, as well as a relative bradycardia, were randomized to receive a dual-chamber pacemaker or not. The pacemaker prevented bradycardia and provided high-rate pacing if a predetermined drop in heart rate occurred (rate-drop response). The primary outcome was the first recurrence of syncope. Patients also completed a detailed diary recording presyncopal episodes.

RESULTS

A total of 284 patients was originally planned and a pilot study of 60 patients was initiated. At the planned first formal interim analysis of efficacy of the pilot study, an unanticipated large treatment effect was observed which fulfilled the prespecified criteria for early termination of the study. At that time, there were 54 patients enrolled, randomized evenly to no pacemaker or to pacemaker. In the no-pacemaker and pacemaker groups the mean ages were 40 and 46 years; 74% and 70% patients, respectively, were female. The baseline tilt-table test showed a slowest heart <60/min or longest heart period >1000 ms in 60% of no-pacemaker patients and 72% of pacemaker patients. There was a marked reduction in the postrandomization risk of syncope in pacemaker patients (relative risk reduction 85.4%, 95% confidence interval 59.7% to 94.7%; 2p=0.000022).

CONCLUSIONS

Dual-chamber pacing with rate-drop response reduces the likelihood of syncope in patients with recurrent vasovagal syncope.

Variable cerebral dysfunction during tilt induced vasovagal syncope

Electroencephalographic (EEG) monitoring was performed during head-up tilt testing (HUT) in a group of 63 consecutive patients (27 males, 36 females, mean age 41.5 years) with a history of recurrent syncope of unknown origin despite extensive clinical and laboratory evaluation. Syncope occurred in 27/63 patients (42.8%) during HUT and was cardioinhibitory in 11/27 (40.7%) and vasodepressor in 16/27 (59.3%). All patients with a negative response to HUT had no significant EEG modifications. In patients with vasodepressor syncope a generalized high amplitude 4-5 Hz (theta range) slowing of EEG activity appeared at the onset of syncope, followed by an increase in brain wave amplitude with a reduction of frequency at 1.5-3 Hz (delta range). The return to the supine position was associated with brain wave amplitude reduction and frequency increase to 4-5 Hz, followed by restoration of a normal EEG pattern and arousal (mean total duration of syncope 23.2 s). In patients with cardioinhibitory syncope, a generalized high amplitude EEG slowing in the theta range was noted at the onset of syncope, followed by a brain wave amplitude increase and slowing in the delta range. A sudden reduction of brain wave amplitude ensued leading to the disappearance of electroencephalographic activity ("flat" EEG). The return to the supine position was not followed by immediate resolution of EEG abnormalities or consciousness recovery, both occurring after a longer time interval (mean total duration of syncope 41.4 s). EEG monitoring during HUT allowed the recording and systematic description of electroencephalographic abnormalities developing in the course of tilt induced vasovagal syncope.

Electroencephalographic correlates of vasovagal syncope induced by head-up tilt testing

BACKGROUND AND PURPOSE

We sought to determine whether the introduction of EEG monitoring during head-up tilt testing could significantly improve the understanding of the cerebral events occurring during tilt-induced vasovagal syncope and the potential danger to the patient of this diagnostic procedure.

METHODS

EEG monitoring was performed during head-up tilt testing in a group of 63 consecutive patients (27 males and 36 females; mean age, 41.5 years) with a history of recurrent syncope of unknown origin despite extensive clinical and laboratory assessment.

RESULTS

Syncope occurred in 27 of 63 patients (42.8%) during head-up tilt testing and was found to be cardioinhibitory in 11 of 27 (40.7%) and vasodepressor in 16 of 27 (59.3%). All patients with a negative response to head-up tilt testing showed no significant EEG modifications. In patients with vasodepressor syncope, a generalized high-amplitude, 4- to 5-Hz (theta range) slowing of EEG activity appeared at the onset of syncope, followed by an increase of brain-wave amplitude with the reduction of frequency at 1.5 to 3 Hz (delta range). The return to the supine position was associated with brain-wave amplitude reduction and frequency increase to 4 to 5 Hz, followed by restoration of a normal EEG pattern and arousal (mean total duration of syncope, 23.2 seconds.). In patients with cardioinhibitory syncope, a generalized high-amplitude EEG slowing in the theta range was noted at the onset of syncope, followed by a brain-wave amplitude increase and slowing in the delta range. A sudden reduction of brain-wave amplitude then ensued, leading to the disappearance of electrocerebral activity ("flat" EEG). The return to the supine position did not allow either the immediate resolution of EEG abnormalities or consciousness recovery, both of which occurred after a further time interval (mean total duration of syncope, 41.4 seconds.).

CONCLUSIONS

EEG monitoring during head-up tilt testing allowed recording and systematic description of electrocerebral abnormalities developing in the course of tilt-induced vasovagal syncope.

Treatment of malignant neurocardiogenic vasovagal syncope with a rate drop algorithm in dual chamber cardiac pacing

A 29-year-old man with malignant vasovagal syncope presented with episodes of abrupt loss of consciousness associated with an aura, totaling more than 10 episodes over 3 months. Holter monitoring showed cardiac arrest with a duration of 15 seconds. Oral propranolol and disopyramide therapy failed to prevent the syncope. A dual chamber pacemaker with a rate drop response algorithm successfully prevented the syncope but not the aura. There may be multifactors involved in the mechanism of this syndrome. The patient has returned to a normal active life. This rate drop algorithm is an effective therapy for the prevention of syncope in malignant vasovagal syncope.

Effect of dual-chamber pacing with automatic rate-drop sensing on recurrent neurally mediated syncope

We tested the hypotheses that a dual-chamber pacemaker that paces when intrinsic rate drops abruptly would reduce the number of syncopal spells and improve the quality of life in patients with highly recurrent neurally mediated syncope. Twelve patients with highly frequent neurally mediated syncope and at least 1 syncopal spell after tilt testing received dual-chamber pacemakers with automatic rate-drop sensing. The pacemakers were implanted 17+/-26 months after tilt testing, and the patients then were followed for 12+/-2 months. We compared the time to the first recurrence of syncope, syncope frequency, and quality of life for the 2 periods between tilt testing and pacemaker implantation, and between implantation and last follow-up. Only 6 of 12 patients fainted after pacemaker insertion. The median time to syncope recurrence before and after pacing was 7 days and 5.3 months, respectively. The geometric mean frequency of faints before and after pacing was 5.0 spells/month (95% confidence interval 2.7 to 9.2) and 0.30 spells/month (95% confidence interval 0.2 to 0.4), p <0.001. After 6 months the mean perception of health on the 100-point EuroQol scale rose from 55 to 82 (p = 0.003), and the general health perception on the SF-36 scale rose from 51 to 72 (p = 0.005). Permanent dual-chamber pacing with automatic rate-drop sensing in patients with highly frequent syncope is associated with a marked reduction in the likelihood of syncope and a marked improvement in quality of life.

Asystolic cardiac arrest during head-up tilt test: incidence and therapeutic implications

Occasionally, the cardioinhibitory response may be profound during tilt induced syncope. Whether this response is associated with more severe symptoms or predicts a poor response to pharmacotherapy remains controversial. The aim of this study was to characterize patients with vasovagally mediated asystole occurring during head-up tilt test and to evaluate the respective interests of sequential pacing and beta-blockers to treat them. We performed 60 degree tilt testing in 179 consecutive patients with unexplained syncope (91 women and 88 men, age 36.6 +/- 20.1 years). Asystole was defined as a ventricular pause > 5 seconds. All patients with tilt induced asystole received therapy with either beta-blockers or sequential pacing, the efficacy of which was evaluated with serial tilt tests. Of 77 patients with positive tilt test, 10 developed syncope related to asystole (mean duration 11.9 +/- 4.9 s), 2 with spontaneous recovery, and 8 with seizures needing a brief cardiopulmonary resuscitation. When compared with patients without asystole, asystolic patients had more severe symptoms (seizures: 6/10 vs 9/67, P = 0.05, injury 9/10 vs 27/67, P = 0.0048). In the first six patients in whom cardiac pacing was considered, syncope or presyncope still occurred despite atrioventricular pacing at 45 beats/min. Five of these 6 patients, as well as the remaining 4 asystolic patients, were tilted with beta-blockers: 3 patients became tilt-negative; 3 were significantly improved; and 3 did not respond. During follow-up (mean 22.7 +/- 11.7 months) with every patient taking beta-blockers and seven having a permanent pacemaker, no syncopal recurrence was observed. Tilt-induced asystole that may require resuscitative maneuvers occurs especially in patients with a history of seizures or injury. Therapy with beta-blockers in often effective to prevent induction of syncope as well as recurrences.

Can adenosine 5'-triphosphate be used to select treatment in severe vasovagal syndrome?

BACKGROUND

Selection of treatment in vasovagal syndrome should be guided by the mechanism of symptoms. This study determined whether a simple drug test may assess one mechanism.

METHODS AND RESULTS

To identify patients at risk of severe cardioinhibitory response of vagal origin, we infused 20 mg ATP into 316 patients hospitalized for recurrent syncope (n=195) or presyncope (n=121) of unknown origin and into normal subjects (n=51). We then assessed the ECG and clinical responses to the drug, recommended therapy, and followed up the subjects chronically. A cardiac pause > 10 seconds was seen in only 3 normal subjects (6%). Therefore, a pause < or = 10 seconds yielded the approximately 95th percentile of the normal range. ATP provoked a pause > 10 seconds in 130 symptomatic patients (41%) and a pause < or = 10 seconds in 186 symptomatic patients (59%). Thus, symptomatic patients with pauses > 10 seconds were proposed for pacemaker implantation; all other patients and normal subjects were simply monitored. Among long-pause patients with follow-up, the observed recurrence rate for the 104 with pacemakers was one-third that for the 21 who were only monitored (P<.0001). Among followed-up short-pause patients, the rate in the 153 monitored-only patients did not differ from the 20 implanted patients (P=.432).

CONCLUSIONS

The vagal effect of ATP may identify the subgroup of patients at high risk of severe cardioinhibitory response of vagal origin who likely will benefit from pacemaker therapy. This fast, uncomplicated test should be considered for further use in screening patients with vasovagal syndrome.

Permanent cardiac pacing in elderly patients with recurrent falls, dizziness and syncope, and a hypersensitive cardioinhibitory reflex

The study was designed to assess the outcome of treatment with permanent dual-chamber pacing of elderly patients with falls, dizziness and syncope associated with the demonstration of a hypersensitive cardioinhibitory reflex. Questionnaires were sent to patients (and their general practitioners) who had been referred to a regional pacing centre with recurrent falls, dizziness or syncope diagnosed as likely to be secondary to cardioinhibitory carotid sinus syndrome or predominantly cardioinhibitory vasovagal syndrome. After pacemaker insertion, 84% of patients had no further syncope over a mean follow-up period of 10 (range 1.5 to 30) months. Minor symptoms persisted in only 40% of all patients. Symptoms were unchanged in 22%. It was concluded that permanent dual-chamber pacing is an effective treatment for elderly patients with recurrent falls, dizziness and syncope in whom a hypersensitive cardioinhibitory reflex is found. Good results were obtained in this group with a simple diagnostic work-up.

Syncope: current diagnosis and treatment

The patient with syncope often poses a formidable diagnostic challenge. A large number of underlying causes must be considered, ranging in severity from benign to life-threatening. A careful, systematic clinical evaluation beginning with a history, physical examination, and ECG will establish the diagnosis in most patients, and the judicious use of specialized testing will confirm or uncover the cause in many of the remaining cases. Further basic and clinical research into the pathogenesis and treatment of neurocardiogenic syncope, the role of HUT testing in neurally mediated syncope, and the optimal use of EPS in patients with cardiac disease will markedly improve our management of these patients in the future.

Rate-drop response programming

Effective programming of the rate-drop response algorithm requires careful attention to the heart rate and blood pressure responses seen during diagnostic tilt testing. In order to undertake effective programming, additional tilt testing procedures may be necessary, and it is vital that the protocol should be identical on each occasion and very careful note taken of exact times of onset of symptoms and relative timing of onset of changes in heart rate and blood pressure. The algorithm settings in the Thera DR generator as delivered (factory or "shelf" parameter settings) must be considered nontherapeutic (an unusual situation for a pacemaker algorithm) and will require adjustment for each individual patient. Effective therapeutic settings are likely to result in an excess of pacing interventions; these, however, tend to be less symptomatic than the syncope or presyncope suffered by the patient and are generally well tolerated or not noticed.

Cardiac pacing for vasovagal syncope: a reasonable therapeutic option?

A number of studies have evaluated the effect of cardiac pacing for prevention of tilt induced vasovagal syncope. The findings are relatively consistent. Pacing does not prevent the onset of vasovagal syncope. This is predictable since hypotension (vasodepressor effect) typically occurs prior to bradycardia. However, dual chamber may prolong the presyncopal period in patients with a prominent cardioinhibitory component. Further, the relation of laboratory observations to spontaneous events is uncertain. In the largest retrospective assessment of pacing efficacy, 89% of patients reported improved symptoms and 62% remained free of symptom recurrence over 50 months.

Clinical experience with Thera DR rate-drop response pacing algorithm in carotid sinus syndrome and vasovagal syncope. The International Rate-Drop Investigators Group

This study examined the effectiveness of cardiac pacing using the Thera DR rate-drop response algorithm for prevention of recurrent symptoms in patients with carotid sinus syndrome (CSS) or vasovagal syncope. The algorithm comprises both diagnostic and treatment elements. The diagnostic element consists of a programmable "window" used to identify heart rate changes compatible with an evolving neurally mediated syncopal episode. The treatment arm consists of pacing at a selectable rate and for a programmable duration. Forty-three patients (mean age 53 +/- 20.4 years) with CSS alone (n = 8), CSS in conjunction with vasovagal syncope (n = 4), or vasovagal syncope alone (n = 31) were included. Thirty-nine had recurrent syncope, while the remaining four reported multiple presyncopal events. Prior to pacing, 40 +/- 152 syncopal episodes (range from 1 to approximately 1,000 syncopal events) over the preceding 56 +/- 84.5 months. Postpacing follow-up duration was 204 +/- 172 days. Three patients have been lost to follow-up and in one patient the algorithm was disabled. Among the remaining 39 individuals, 31 (80%) indicated absence or diminished frequency of symptoms, or less severe symptoms. Twenty-three patients (23/29, or 59%) were asymptomatic with respect to syncope or presyncope. Sixteen patients had symptom recurrences. Of these, seven experienced syncope (7/39, or 18%) and 9 (29%) had presyncope: the majority of patients with recurrences (6/7 syncope and 7/9 presyncope) were individuals with a history of vasovagal syncope. Consequently, although symptoms were observed during postpacing follow-up, they appeared to be of reduced frequency and severity. Thus, our findings suggest that a transient period of high rate pacing triggered by the Thera DR rate-drop response algorithm was beneficial in a large proportion of highly symptomatic patients with CSS or vasovagal syncope.

Prolonged asystole induced by head up tilt test. Report of four cases and brief review of the prognostic significance and medical management

Head up tilt is an established test for assessing patients with vasovagal syncope. Prolonged asystole during the test has previously been reported in patients suffering from the malignant form of this syndrome. Little is known about the prognostic significance of this response and there is no consensus about the optimum treatment. Four such patients are reported who were treated pharmacologically. During follow up they remained free from major events and their symptoms were well controlled. Conservative management is the initial method of choice and only if this fails should implantation of a dual chamber permanent pacemaker be considered.

North American Vasovagal Pacemaker Study: study design and organization

The North American Vasovagal Pacemaker Study is an ongoing multicenter randomized, clinical trial that assesses the efficacy of dual chamber pacing utilizing rate drop sensing in patients with frequent syncopal spells. Patients are eligible if they have had at least six syncopal spells and a positive tilt table test, or a recurrence of syncope within 6 months of a positive tilt test. The tilt table test must have provoked a relative bradycardia. Patients are randomized to receive a Medtronic Thera DR with rate drop sensing, or to continue on their usual therapy. All patients complete a log of their presyncopal and syncopal spells daily, and are contacted every 2 months. The primary outcome measure is the time to the first recurrence of syncope. The goal of the main study is to recruit 284 patients in 3 years with a final fourth year of follow-up; this will result in an 80% chance of detecting a 30% reduction in the risk of syncope. A pilot study is under way with the aim to recruit 60 patients over a period of 2 years with a final third year of follow-up. Recruitment began in July 1995 and 47 patients have been enrolled to date.