Permanent pacing for cardioinhibitory malignant vasovagal syndrome

Transcatheter Leadless Pacemaker for the Treatment of Vasovagal Syncope

Vasovagal syncope (VVS) is largely a benign condition focused on patient education, lifestyle modification, and avoidance of triggers. However, a subset of patients may benefit from permanent pacemaker placement. Commonly, patients with VVS are younger and those requiring pacing have symptoms associated with severe cardioinhibitory syncope. With the advent of leadless pacemaker systems, a lot of the risks associated with traditional transvenous pacemaker systems are mitigated. In this article, we provide a comprehensive review of the data available for the treatment of cardioinhibitory vasovagal syncope using leadless pacemaker systems.

Likelihood of injury due to vasovagal syncope: a systematic review and meta-analysis

AIMS

Vasovagal syncope (VVS) is the most common type of syncope and is usually considered a benign disorder. The potential for injury is worrisome but the likelihood is unknown. We aimed to determine the proportion of patients injured due to VVS.

METHODS AND RESULTS

A systematic search of studies published until August 2020 was performed in multiple medical and nursing databases. Included studies had data on the proportion of patients with injury due to VVS prior to study enrolment. Random effects methods were used. Twenty-three studies having 3593 patients met inclusion criteria. Patients were diagnosed clinically with VVS, and 82% had >2 syncopal episodes before enrolment. Tilt test was positive in 60% and 14 studies reported comorbidities (32.6% hypertensive). The weighted mean injury rate was 33.5% [95% confidence interval (CI): 27.3-40.5%]. The likelihood of injury correlated with population age (r = 0.4, P = 0.05), but not with sex, positive tilt test, or hypertension. The injury rates were 25.7% (95% CI: 19.1-32.8%) in studies with younger patients (mean age ≤50 years, n = 1803) and 43.4% (95% CI: 34.9-52.3%) in studies with older patients (P = 0.002). Nine studies reported major injuries; with a weighted mean rate of major injuries of 13.9% (95% CI: 9.5-19.8%).

CONCLUSION

Injuries due to syncope are frequent, occurring in 33% of patients with VVS. The risk of major injuries is substantial. Older patients are at higher risk. Clinicians should be aware of the risk of injuries when providing care and advice to patients with VVS.

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 in vasovagal syncope: Physiology, pacemaker sensors, and recent clinical trials-Precise patient selection and measurable benefit

The role of pacing in vasovagal syncope (VVS) is considered from a physiological basis. Most VVS patients lose consciousness due to hypotension before severe bradycardia/asystole occurs. Patients who benefit from dual-chamber pacing typically are older with highly symptomatic, late-onset, frequent and severe syncope with short/no prodrome and documented severe cardioinhibition. Tilt testing is of value in patients with recurrent unexplained syncope to identify important hypotensive susceptibility stemming from reduced venous return and stroke volume (SV). A negative tilt test in vasovagal patients with spontaneous asystole documented by an implantable/insertable loop recorder is associated with lower syncope recurrence rates after pacemaker implantation. Pacing may be more effective if triggered by sensor detection of a parameter changing earlier in the reflex than bradycardia when SV may still be relatively preserved. In this regard, detection of right ventricular impedance offers promise. Conservatism is recommended, limiting pacing in VVS to a small subset of symptomatic older patients with clearly documented cardioinhibition and paying particular attention to the timing of loss of consciousness in relation to asystole/bradycardia. Understanding VVS physiology permits application of well-timed, appropriate pacing that yields benefit for highly symptomatic patients.

Closed-looped stimulation cardiac pacing for recurrent vasovagal syncope: A systematic review and meta-analysis

BACKGROUND

Vasovagal syncope (VVS) is defined by transient loss of consciousness with spontaneous rapid recovery. Recently, a closed-loop stimulation pacing system (CLS) has shown superior effectiveness to conventional pacing in refractory VVS. However, systematic review and meta-analysis has not been performed. We assessed the impact of CLS implantation and reduction in recurrent VVS events by a systematic review and a meta-analysis.

METHODS

We comprehensively searched the databases of MEDLINE and EMBASE from inception to September 2017. Included studies were published prospective or retrospective cohort, randomized controlled trial, and case-control studies that compared VVS events between recurrent, severe, or refractory cardioinhibitory VVS patient implanted with CLS and conventional pacing. Data from each study were combined using the random-effects, generic inverse variance method of DerSimonian and Laird to calculate odds ratios and 95% confidence intervals.

RESULTS

Six studies from November 2004 to October 2017 were included in this meta-analysis involving 224 recurrent, severe, or refractory cardioinhibitory VVS patients implanted with CLS and 163 recurrent, severe, or refractory VVS patients implanted with conventional pacing. CLS significantly reduced recurrent VVS events compared to conventional pacing (pooled odds ratio = 0.23, 95% confidence interval: 0.13-0.39, P = 0.000, I 2 = 36.5%) as well as subgroup of four randomized controlled trial studies (pooled odds ratio = 0.28, 95% confidence interval: 0.17-0.44, P = 0.000, I 2 = 39.2%).

CONCLUSION

Closed-loop stimulation significantly reduced recurrent VVS events up to 80% when compared to conventional pacing. Our study suggests that CLS is an effective tool for preventing syncope recurrences in patients with recurrent, severe, or refractory cardioinhibitory VVS.

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.

Pacing in neurocardiogenic/vasovagal syncope

Pacing for neurocardiogenic or vasovagal syncope (VVS) has been practised for five decades, but the 1986 advent of tilt testing provided a means of diagnosis frequently revealing, in the early days, asystole caused by VVS. This was the basis for pacing these patients and the first studies created enthusiasm followed by randomised controlled trials, which were imperfectly designed, "confirming" benefit. When better trial design was employed, there was no obvious benefit. However, some cardiologists had seen patients experience a huge positive difference with pacing, so they set out to identify them. Two studies using ECG loop recorders to document heart rhythm during spontaneous attacks allowed better patient selection for pacing and appeared to achieve the aim. Further, it was noted in the second study, a randomised controlled trial (RCT) with good design, that tilt testing added a further dimension to the identification of the patient who would benefit. Thus, loop recorders are used to show asystole in spontaneous attacks and when tilt testing is negative, implying a lesser vasodepressor component, the patient will have the best outcome. From the available evidence, pacing should be dual-chamber in older patients (>40 years) with severe symptoms and in whom standard measures have demonstrably failed. The method of triggering pacing and its timing of introduction have not yet been resolved. Today's method is rate-hysteresis but there is another sensed event as an alternative: right ventricular impedance, which is now in RCT with substantial pilot evidence in its favour.

Autonomic Dysfunction in Cardiology: Pathophysiology, Investigation, and Management

Presyncope and syncope are common medical findings, with a > 40% estimated lifetime prevalence. These conditions are often elicited by postural stress and can be recurrent and accompanied by debilitating symptoms of cerebral hypoperfusion. Therefore, it is critical for physicians to become familiar with the diagnosis and treatment of common underlying causes of presyncope and syncope. In some patients, altered postural hemodynamic responses result from a failure of compensatory autonomic nervous system reflex mechanisms. The most common presentations of presyncope and syncope secondary to this autonomic dysfunction include vasovagal syncope, neurogenic orthostatic hypotension, and postural tachycardia syndrome. The most sensitive method for diagnosis is a detailed initial evaluation with medical history, physical examination, and resting electrocardiogram to rule out cardiac syncope. Physical examination should include measurement of supine and standing blood pressure and heart rate to identify the pattern of hemodynamic regulation during orthostatic stress. Additional testing may be required in patients without a clear diagnosis after the initial evaluation. Management of patients should focus on improving symptoms and functional status and not targeting arbitrary hemodynamic values. An individualized structured and stepwise approach should be taken for treatment, starting with patient education, lifestyle modifications, and use of physical counter-pressure manoeuvres and devices to improve venous return. Pharmacologic interventions should be added only when conservative approaches are insufficient to improve symptoms. There are no gold standard approaches for pharmacologic treatment in these conditions, with medications often used off label and with limited long-term data for effectiveness.

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.

Reflex syncope: Diagnosis and treatment

For the diagnosis of reflex syncope, diligent history-building with the patient and a witness is required. In the Emergency Department (ED), the assessment of syncope is a challenge which may be addressed by an ED Observation Unit or by a referral to a Syncope Unit. Hospital admission is necessary for those with life-threatening cardiac conditions although risk stratification remains an unsolved problem. Other patients may be investigated with less urgency by carotid sinus massage (>40 years), tilt testing, and electrocardiogram loop recorder insertion resulting in a clear cause for syncope. Management includes, in general terms, patient education, avoidance of circumstances in which syncope is likely, increase in fluid and salt consumption, and physical counter-pressure maneuvers. In older patients, those that will benefit from cardiac pacing are now well defined. In all patients, the benefit of drug therapy is often disappointing and there remains no ideal drug. A role for catheter ablation may emerge for the highly symptomatic reflex syncope patient.

The Current Indication for Pacemaker in Patients with Cardioinhibitory Vasovagal Syncope

The most frequent cause of syncope is vasovagal reflex. It is associated with worse quality of life, depression, fatigue and physical injury. Recurrence of vasovagal syncope is an aggravating, reaching the rate of 69%. Initial step and pharmacological treatment may not work, especially in patients with recurrent syncope without prodrome. These patients can present cardioinhibitory response with asystole. Studies were designed to analyses the effectiveness of pacemaker for prevention of syncope. In this review, nonrandomized clinical trials, open-label randomized, double-blind randomized, placebo-controlled, and studies based on tilt test or Implantable Loop Recorder findings will be discussed.

Reflex vasovagal syncope--is there a benefit in pacemaker therapy?

Reflex vasovagal syncope often affects young populations and is associated with a benign prognosis in terms of mortality. However, a minority of patients have recurrent episodes, with a considerable impact on their quality of life. Pacemaker therapy has been an option in these patients since the 1990s if a conservative strategy fails. Initially, non-randomized and open-label randomized trials showed promising results, but these studies were associated with a significant placebo effect. Recently, an approach based on the use of implantable loop recorders has shown that some patients with reflex vasovagal syncope could benefit from implantation with dual-chamber pacemakers, particularly patients aged >40 years, with recurrent syncopal episodes resulting in frequent injuries, in whom a long asystole (≥3 s asystole with syncope or ≥6 s asystole without syncope) has been documented with an implantable loop recorder. The authors present a literature review on the role of cardiac pacing in reflex vasovagal syncope and propose a diagnostic and therapeutic decision flowchart for patients with syncope of probable reflex etiology.

Management of vasovagal syncope: 2004

Vasovagal syncope is a common disorder that affects at least 20% of people at some time in their lives. Probably half of these patients faint recurrently; for many this causes physical trauma, a substantial reduction in quality of life, and difficulties with driving, employment and education. The last 15 years have seen striking advances in diagnostic approaches and prognostic understanding. A number of physiological, pharmacological and electrical therapies have been developed and tested to various degrees in patients. These include counterpressure manoeuvres, salt and fluid recommendations, and attempted treatment with fludrocortisone, midodrine, beta-blockers, serotonin reuptake inhibitors, and permanent pacemakers. This review highlights the most important of these advances and suggests strategies for managing this often difficult problem.

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.

Are treatments for vasovagal syncope effective? A meta-analysis

BACKGROUND

Therapies used to treat vaso-vagal syncope (VVS) recurrence have not been proven effective in single studies.

METHODS

Comprehensive search of PubMed, EMBASE and Cochrane Central databases of published trials was done. Randomized or non-randomized studies, comparing the intervention of interest to control group(s), with the endpoint of spontaneous recurrence or syncope on head-up tilt test, were included. Data were extracted on an intention-to-treat basis. Study heterogeneity was analyzed by Cochran's Q statistics. A random-effect analysis was used.

RESULTS

α-adrenergic agonists were found effective (n=400, OR 0.19, CI 0.06-0.62, p<0.05) in preventing VVS recurrence. β-blockers were not found to be effective when only randomized studies comparing β-blockers to non-pharmacologic agents were assessed (9 studies, n=583, OR 0.48, CI 0.22-1.04, p=0.06). Tilt-training had no effect when only randomized studies were considered (4 studies, n=298, OR 0.47, CI 0.21-1.05, p=0.07). Selective serotonin reuptake inhibitors were found effective (n=131, OR 0.28, CI 0.10-0.74, p<0.05), though the analysis contained only 2 studies. Pacemakers were found effective in preventing syncope recurrence when all studies were analyzed (n=463, OR 0.13, CI 0.05-0.36, p<0.05). However, studies comparing active pacemaker to sensing mode only did not show benefit (3 studies, n=162, OR 0.45, CI 0.09-2.14, p=0.32).

CONCLUSIONS

This meta-analysis highlights the totality of evidence for commonly used medications used to treat VVS, and the requirement for larger, double-blind, placebo controlled trials with longer follow-up.

Late Recognition of Malignant Vasovagal Syncope

A 21-year-old female with a history of seizures since the age of 5 presented for long-term electroencephalographic (EEG) monitoring, but was found instead to have neurocardiogenic syncope. Is it appropriate for this patient to get a pacemaker?

Contemporary pacemakers: what the primary care physician needs to know

Pacemaker therapy is most commonly initiated because of symptomatic bradycardia, usually resulting from sinus node disease. Randomized multicenter trials assessing the relative benefits of different pacing modes have made possible an evidence-based approach to the treatment of bradyarrhythmias. During the past several decades, major advances in technology and in our understanding of cardiac pathophysiology have led to the development of new pacing techniques for the treatment of heart failure in the absence of bradycardia. Left ventricular or biventricular pacing may improve symptoms of heart failure and objective measurements of left ventricular systolic dysfunction by resynchronizing cardiac contraction. However, emerging clinical data suggest that long-term right ventricular apical pacing may have harmful effects. As the complexity of cardiac pacing devices continues to grow, physicians need to have a basic understanding of device indications, device function, and common problems encountered by patients with devices in the medical and home environment.

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.

Outcome of patients with dual-chamber pacemakers implanted for the prevention of neurally mediated syncope

Dual-chamber pacemaker insertion (PI) has been found to reduce the recurrence of neurally mediated syncope (NMS) in 3 randomized trials. However, the long-term benefits of PI are unknown. To assess the natural history of NMS, we followed a cohort of 40 patients who underwent PI for frequent NMS for 46 to 75 months. We assessed the reduction in syncope frequency after PI and the time to first recurrence of syncope. Sixty months after PI, 32.5% of patients remained free of NMS. The frequency of syncope decreased from 0.46 to 0.06 spells/month (before to after PI, p = 0.04). Two groups of patients were identified, with responders to PI defined as having a 75% decrease in the frequency of NMS. Responders (n = 22) experienced a significant decrease in the frequency of NMS (0.31 to 0.01 spells/month, p <0.0001), whereas nonresponders did not experience a similar reduction (p = 0.8). Responders could not be identified by either baseline or tilt-test parameters. Patients without an early recurrence of syncope after PI (within 6 months) experienced a significant reduction in the frequency of NMS (0.24 to 0.02 spells/month, p = 0.0002), although the reduction was not significant (p = 0.3) in patients with an early recurrence of syncope. Some, but not all, patients respond to permanent PI for NMS. The long-term benefit of permanent PI can be predicted by timing of the first recurrence of syncope, but not by preimplantation factors.

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.

Diagnosis and treatment of neurally mediated syncope

BACKGROUND

Syncope is caused by a severe but reversible reduction in blood flow to the brain stem neurons responsible for supporting consciousness (reticular activating system). Neurally mediated syncope, also referred to as vasovagal or reflex syncope, is the most frequent cause of loss of consciousness in apparently normal subjects.

REVIEW SUMMARY

Neurally mediated syncope is believed to be a reflex response with afferent, central, and efferent pathways. Characteristic autonomic changes in neurally mediated syncope are an increase in parasympathetic efferent activity causing bradycardia and a reduction in sympathetic vasoconstrictor outflow causing vasodilatation. Premonitory symptoms, such as nausea, diaphoresis, abdominal discomfort, and blurred vision, are caused by autonomic activation and are distinguishing features of neurally mediated syncope. Neurally mediated syncope frequently has a characteristic trigger, although this may not be apparent. Testing orthostatic tolerance during passive head-up tilt is the best available diagnostic procedure to evaluate patients with syncope in whom a cardiac cause has been excluded. In many cases, once the diagnosis of neurally mediated syncope is confirmed, it may suffice to reassure the patient and teach him to avoid known triggers and to recognize and act upon early warning symptoms. Because subjects with neurally mediated syncope may potentially be sodium depleted, increasing salt intake can be beneficial in improving their orthostatic intolerance.

CONCLUSIONS

Neurally mediated syncope is the most common form of syncope in healthy adults. The best diagnostic tools are the clinical history and passive head-up tilt. The best treatment strategies are the avoidance of triggering factors as well as intravascular volume expansion.

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.

Syncope

Successful treatment of patients with syncope depends on the accuracy of the diagnosis, because syncope is a symptom, not a disease; diagnosis of the cause for syncope therefore creates a blueprint for treatment. Most experienced practitioners can diagnose the cause of syncope for less than half of their patients. Excessive and repeat testing is expensive and may not improve the chance of a correct diagnosis. Patient history is the key to the diagnosis. Treatment may vary from a lifestyle change to open heart surgery. The great challenge of treating patients with syncope is to provide cost-effective, safe therapy to those with a benign course and still provide needed treatment for those whose syncope is life threatening.

Permanent cardiac pacing versus medical treatment for the prevention of recurrent vasovagal syncope: a multicenter, randomized, controlled trial

BACKGROUND

This clinical investigation was performed to compare the effects of permanent dual-chamber cardiac pacing with pharmacological therapy in patients with recurrent vasovagal syncope.

METHODS AND RESULTS

Patients from 14 centers were randomized to receive either a DDD pacemaker provided with rate-drop response function or the beta-blocker atenolol at the dosage of 100 mg once a day. Inclusion criteria were age >35 years, >/=3 syncopal spells in the preceding 2 years, and positive response to tilt table testing with syncope occurring in association with relative bradycardia. The primary outcome was the first recurrence of syncope after randomization. Enrollment was started in December 1997, and the first formal interim analysis was performed on July 30, 2000. By that time, 93 patients (38 men and 55 women; mean age, 58.1+/-14.3 years) had been enrolled and randomized, although follow-up data were available for all patients (46 patients in the pacemaker arm, 47 patients in the pharmacological arm). The interim analysis showed a significant effect in favor of permanent cardiac pacing (recurrence of syncope in 2 patients [4.3%] after a median of 390 days) compared with medical treatment (recurrence of syncope in 12 patients [25.5%] after a median of 135 days; OR, 0.133; 95% CI, 0.028 to 0.632; P=0.004). Consequently, enrollment and follow-up were terminated.

CONCLUSIONS

DDD pacing with rate-drop response function is more effective than beta-blockade for the prevention of syncopal recurrences in highly symptomatic vasovagal fainters with relative bradycardia during tilt-induced syncope.

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.

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.

Dual-chamber pacing in the treatment of neurally mediated tilt-positive cardioinhibitory syncope : pacemaker versus no therapy: a multicenter randomized study. The Vasovagal Syncope International Study (VASIS) Investigators

BACKGROUND-This study was performed to compare implantation of a DDI pacemaker with rate hysteresis with no implant in respect to syncopal recurrences in patients with severe cardioinhibitory tilt-positive neurally mediated syncope. METHODS AND RESULTS-Forty-two patients from 18 European centers were randomized to receive a DDI pacemaker programmed to 80 bpm with hysteresis of 45 bpm (19 patients) or no pacemaker (23 patients). Inclusion criteria were >/=3 syncopes over the last 2 years and a positive cardioinhibitory (Vasovagal Syncope International Study types 2A and 2B) response to tilt testing. The median number of previous syncopal episodes was 6; asystolic response to tilt testing was present in 36 patients (86%) (mean asystole, 13.9+/-10.2 seconds). All patients were followed up for a minimum of 1.0 years and a maximum of 6.7 years (mean, 3.7+/-2.2). One patient (5%) in the pacemaker arm experienced recurrence of syncope compared with 14 patients (61%) in the no-pacemaker arm (P=0.0006). In the no-pacemaker arm, the median time to first syncopal recurrence was 5 months, with a rate of 0.44 per year. On repeated tilt testing performed within 15 days after enrollment, positive responses were observed in 59% of patients with pacemakers and in 61% of patients without pacemakers (P=NS). CONCLUSIONS-In a limited, select group of patients with tilt-positive cardioinhibitory syncope, DDI pacing with hysteresis reduced the likelihood of syncope. The benefit of the therapy was maintained over the long term. Even in untreated patients, the syncopal recurrence burden was low. A negative result of tilt testing was not a useful means to evaluate therapy efficacy.

Emerging indications for permanent pacing

New indications for pacing are being investigated in the areas of vasovagal syncope, hypertrophic obstructive cardiomyopathy, dilated cardiomyopathy, and atrial fibrillation. It is hoped that pacing will offer an alternative therapy to patients who are refractory to medical therapy. Although pacing for vasovagal syncope continues to be controversial, it appears that a highly symptomatic group with a predominately cardioinhibitory component can benefit. Current data indicate that dual-chamber pacing should not be considered therapeutically equal to septal myectomy in patients with hypertrophic obstructive cardiomyopathy, but may be considered in those more than 65 years of age, or in others who are not good surgical candidates. Biventricular or left ventricular pacing appears promising in heart failure patients and may be combined with implantable cardioverter-defibrillator therapy. Lead technology for coronary vein placement needs further improvement. Dual-site atrial pacing appears to help prevent recurrences of atrial fibrillation and may become a useful adjunct to drug, ablative, and implantable cardioverter-defibrillator therapies.

Role of carotid sinus syndrome and neurocardiogenic syncope in recurrent syncope and falls in patients referred to an outpatient clinic in a district general hospital

Carotid sinus syndrome (CSS) and neurocardiogenic syncope (NCS) are recognised as important causes of recurrent syncope and falls in the elderly. In this study the role of CSS (diagnosed with carotid sinus massage) and NCS (diagnosed with prolonged head-up tilt) in a district general hospital were investigated. Over 27 consecutive months carotid sinus massage was performed in 139 patients. Of these 29 (20.8%) patients (mean (SD) age of 78 (9) years) showed a positive response. Of these 18 (62%) patients showed a positive response only when carotid sinus massage was performed with 70( degrees ) head-up tilt. Thirteen (8.7%) of the 149 patients who had prolonged head-up tilt testing were found to have NCS. The mean (SD) age for patients with NCS was 59 (26) years and the mean (SD) time required to produce a positive response during prolonged head-up tilt was 12 (5) minutes. It is concluded that carotid sinus massage and head-up tilt testing are useful in patients presenting with unexplained syncope and falls in a district general hospital setting. Carotid sinus massage should be repeated upon head-up tilt if a negative response is obtained in the supine position.

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.

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.

A review of pathophysiology and therapy of patients with vasovagal syncope

Vasovagal syncope is a common disorder that can compromise quality of life and lead to significant morbidity. It is characterized by an initial exaggerated sympathetic output followed by parasympathetic activation and sympathetic withdrawal, as shown by diagnostic head-up tilt (HUT) table testing. Numerous drugs have been evaluated for treating this disorder. beta-Blockers are well studied and commonly administered but are specifically more efficacious in patients with isoproterenol HUT than in those with regular HUT. The role of the serotonergic system has captured new interest. Selective serotonin reuptake inhibitors show promising results in preventing vasovagal syncope in treatment-refractory patients. Also, new investigations suggest that serotonin receptor antagonism may be beneficial. Despite these findings, definitive treatment does not exist.