2017 ACC/AHA/HRS guideline for the evaluation and management of patients with syncope: Executive summary

Syncope and loss of consciousness after implantation of a cardioverter-defibrillator in patients with Brugada syndrome: Prevalence and characteristics in long-term follow-up

Background

Syncope is a significant prognostic factor in patients with Brugada syndrome (BrS). However, the risk of ventricular arrhythmia in patients with nonarrhythmic loss of consciousness (LOC) is similar to that in asymptomatic patients. LOC events after implantable cardioverter-defibrillator (ICD) implantation may provide insights into underlying causes of the initial LOC episode.

Objective

The purpose of this study was to examine LOC characteristics following ICD implantation.

Methods

We retrospectively analyzed 112 patients with BrS (mean age 47 years; 111 men) who were treated with an ICD. The patients were classified into 3 groups based on symptoms at implantation: asymptomatic (35 patients); LOC (46 patients); and ventricular tachyarrhythmia (VTA) (31 patients). We evaluated the incidence and cause of LOC during long-term follow-up after ICD implantation.

Results

During mean follow-up of 12.2 years, 41 patients (37%) experienced LOC after ICD implantation. Arrhythmic LOC occurred in 5 asymptomatic patients, 14 LOC patients, and 16 patients with VTA. Nonarrhythmic LOC, similar to the initial episode, occurred after ICD implantation in 6 patients with prior LOC (2 with neurally mediated syncope and 4 with epilepsy). Most epileptic patients experienced LOC during rest or sleeping, and did not show an abnormal encephalogram during initial evaluation of the LOC episodes.

Conclusion

After ICD implantation, 13% of patients had nonarrhythmic LOC similar to the initial episode. Accurate classification of LOC based on a detailed medical history is important for risk stratification, although distinguishing arrhythmic LOC from epilepsy-related LOC episodes can be challenging depending on the circumstances and characteristics of the LOC event.

Neuroimaging for differential diagnosis of transient neurological attacks

BACKGROUND

Rapid yet comprehensive neuroimaging protocols are required for patients with suspected acute stroke. However, stroke mimics can account for approximately one in five clinically diagnosed acute ischemic strokes and the rate of thrombolyzed mimics can be as high as 17%. Therefore, to accurately determine the diagnosis and differentiate mimics from true transient ischemic attacks, acute ischemic stroke is a challenge to every clinician.

DISCUSSION

Medical history and neurological examination, noncontract head computed tomography, and routine magnetic resonance imaging play important roles in the assessment and management of patients with transient neurological attacks in the emergency department. This review attempts to summarize how neuroimaging can be utilized to help differentiate the most common mimics from transient ischemic attack and acute ischemic stroke.

CONCLUSION

Although imaging can help direct critical triage decisions for intravenous thrombolysis or endovascular therapy, more detailed medical history and neurological examination are crucial for making a prompt and accurate diagnosis for transient neurological attack patients.

Syncope and the Risk of Subsequent Motor Vehicle Crash: A Population-Based Retrospective Cohort Study

IMPORTANCE

Medical driving restrictions are burdensome, yet syncope recurrence while driving can cause a motor vehicle crash (MVC). Few empirical data inform current driving restrictions after syncope.

OBJECTIVE

To examine MVC risk among patients visiting the emergency department (ED) after first-episode syncope.

DESIGN, SETTING, AND PARTICIPANTS

A population-based, retrospective observational cohort study of MVC risk after first-episode syncope was performed in British Columbia, Canada. Patients visiting any of 6 urban EDs for syncope and collapse were age- and sex-matched to 4 control patients visiting the same ED in the same month for a condition other than syncope. Patients' ED medical records were linked to administrative health records, driving history, and detailed crash reports. Crash-free survival among individuals with syncope was then compared with that among matched control patients. Data analyses were performed from May 2020 to March 2022.

EXPOSURES

Initial ED visit for syncope.

MAIN OUTCOMES AND MEASURES

Involvement as a driver in an MVC in the year following the index ED visit. Crashes were identified using insurance claim data and police crash reports.

RESULTS

The study cohort included 43 589 patients (9223 patients with syncope and 34 366 controls; median [IQR] age, 54 [35-72] years; 22 360 [51.3%] women; 5033 [11.5%] rural residents). At baseline, crude MVC incidence rates among both the syncope and control groups were higher than among the general population (12.2, 13.2, and 8.2 crashes per 100 driver-years, respectively). In the year following index ED visit, 846 first crashes occurred in the syncope group and 3457 first crashes occurred in the control group, indicating no significant difference in subsequent MVC risk (9.2% vs 10.1%; adjusted hazard ratio [aHR], 0.93; 95% CI, 0.87-1.01; P = .07). Subsequent crash risk among patients with syncope was not significantly increased in the first 30 days after index ED visit (aHR, 1.07; 95% CI, 0.84-1.36; P = .56) or among subgroups at higher risk of adverse events after syncope (eg, age >65 years; cardiogenic syncope; Canadian Syncope Risk Score ≥1).

CONCLUSIONS AND RELEVANCE

The findings of this population-based retrospective cohort study suggest that patients visiting the ED with first-episode syncope exhibit a subsequent crash risk no different than the average ED patient. More stringent driving restrictions after syncope may not be warranted.

Resource utilisation among patients with syncope presenting to the emergency department

BACKGROUND

Syncope is a common problem encountered in the emergency department (ED) and a significant source of ED resource utilisation, including advanced imaging modalities. Current guidelines do not recommend routine Computed Tomography (CT) imaging of the head for patients seen in the ED due to syncope.

OBJECTIVE

In this study, we investigate resource allocation in the ED for syncope-related visits, including advanced imaging modalities using a large national database.

OUTCOMES ANALYSIS

Data from the CDC's National Hospital Ambulatory Medical Care Survey (NHAMCS) for years 2008-2017 were compiled and analysed. Intrinsic survey and constructed variables were utilised to identify and investigate all syncope-related ED visits in the United States during the study period that met study criteria. Appropriate bivariate and multivariate statistical analyses were applied in order to identify and compare the resource utilisation, demographics, and ED visit dynamics of syncope and non-syncope-related ED visits.

RESULTS

During the study period, there were over 15 million ED visits for syncope. A high percentage of syncope visits received head CT compared with non-syncope visits (34% vs. 4.5%, P > .001). When investigated by age-grouping utilisation of head CT ranged from 26.5 (95% CI 18.9-27.5) for ages 18-40 to as high as 40.2% (95% CI 33.8-47.1) for ages 80 and higher. Compared with non-syncope ED visits, syncope-related ED visits were older and more likely to have Medicare or private insurance.

CONCLUSION

Syncope continues to be a large and growing share of visits to US EDs. Despite well-supported, evidence-based recommendations that do not recommend routine utilisation of head CT in syncope-related ED visits, these data suggest that emergency physicians routinely over-utilise this modality. More specific guidelines may be required to help reduce the use of imaging studies for patients who present to the ED with syncope.

Cardioneuroablation for cardioinhibitory vasovagal syncope

BACKGROUND

Cardioneuroablation (CNA) is an emerging technique being used to treat patients with cardioinhibitory vasovagal syncope (VVS). We describe a case of CNA in targeting atrial ganglionated plexi (GP) based upon anatomical landmarks and fractionated electrogram (EGM) localization in a patient with cardioinhibitory syncope.

CASE PRESENTATION

A 20-year-old healthy female presented with malignant VVS and symptomatic sinus pauses, with the longest detected at 10 s. She underwent acutely successful CNA with demonstration of vagal response (VR) noted after ablation of left sided GP, and tachycardia noted with right sided GP ablation. All GP sites were defined by anatomical landmarks and EGM analysis. By using the fractionation mapping software of Ensite Precision mapping system with high density mapping, fragmented EGMs were successfully detected in each GP site. One month after vagal denervation, there were no recurrent syncopal episodes or sinus pauses. Longer term follow-up with implantable loop recorder is planned.

CONCLUSION

We performed CNA in a patient with VVS by utilizing a novel approach of combined use of high density mapping and fractionation mapping software. With this approach, we were able to detect fractionation in all GP sites and demonstrate acute VR. This workflow may allow for a new, standardized technique suitable for widespread use.

Fractionation Mapping of the Ganglionated Plexi for Cardioneuroablation

Cardioneuroablation (CNA) is an emerging technique used to treat patients with vasovagal syncope (VVS). We herein describe a case of CNA targeting the atrial ganglionated plexi (GPs) based upon anatomical landmarks and fractionated electrogram (EGM) localization in a 20-year-old healthy female who presented to our center with malignant VVS and symptomatic sinus pauses, the longest of which measured 10 seconds. She underwent acutely successful CNA with a demonstration of vagal response noted following ablation of the left-sided GPs, and tachycardia was noted with right-sided GP ablation. All GP sites were defined by anatomical landmarks and EGM analysis. By using the fractionation mapping software of the EnSite Precision™ cardiac mapping system (Abbott, Chicago, IL, USA) with high-density mapping, fragmented EGMs were successfully detected in each GP site. One month after vagal denervation, no recurrent syncopal episodes or sinus pauses had been recorded. Longer-term follow-up with an implantable loop recorder is planned. Broadly, we performed CNA in a patient with VVS by combining high-density mapping and fractionation mapping software in a novel approach, which allowed us to detect fractionation in all GP sites and demonstrate an acute vagal response. This workflow may facilitate the introduction of a standardized technique suitable for widespread use.

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.

Defining Cardiac Dysautonomia - Different Types, Overlap Syndromes; Case-based Presentations

The cardiovascular branch of autonomic nervous system (ANS) is responsible for the regulation of heart rate, blood pressure, and maintaining homeostasis during physiological stress such as exercise and standing upright. ANS constantly controls the rate and force of heart contractions and the vascular tone with the aim to maintain the sufficient tissue perfusion with oxygenated blood and secure venous return to the heart. Dysautonomias, result of ANS malfunction, are often found in patients with cardiovascular symptoms. Apart from the most prevalent one, arterial hypertension, the cardiovascular dysautonomic continuum encompasses other important although less known conditions: postural orthostatic tachycardia syndrome, inappropriate sinus tachycardia, orthostatic hypotension and reflex syncope. Moreover, heart diseases may evoke autonomic imbalance by themselves; cardiac pump failure is usually associated with sympathetic hyperactivity, neuroendocrine vasopressor activation, higher heart rate, reduced heart rate variability and baroreflex hyposensitivity, all of which are predictors of adverse outcomes. Cardiologists and electrophysiologist frequently see patients for the evaluation and management of unexplained syncope, orthostatic intolerance, heart rhythm abnormalities and symptoms of palpitations. Recognizing the presence of cardiac dysautonomia is an important skill which is necessary for the appropriate evaluation and treatment of these patients. Clinical presentations may overlap, and the importance of a thorough history cannot be over-emphasized. In this review we will present a cases of a patients with cardiac dysautonomia which is illustrative of a typical patient experience, followed by a review of the autonomic nervous system and discussion of prevalence, clinical presentation, and pathophysiology of common cardiac dysautonomias.

Is there any link between vitamin D deficiency and vasovagal syncope?

BACKGROUND

This study aimed to investigate serum 25[OH]D levels between patients with vasovagal syncope (VVS) diagnosed with head-up tilt table test (HUTT) and age-matched healthy people.

METHODS

The study included 75 consecutive patients (32.3 ± 10.7 years), who presented with syncope and underwent HUTT and 52 healthy controls (32.9 ± 14.1 years). HUTT patients were divided into two groups according to whether there was syncope response to the test. Patients underwent cardiac, psychiatric, and neurological investigation. Serum 25[OH]D levels were measured by chemiluminescent microparticle immunoassay method.

RESULTS

There was no difference between the two groups in terms of age, gender, body mass index (BMI), echocardiographic findings (P > .05). Mean serum 25[OH]D (24.5 ± 6.3 vs 20.1 ± 8.8 ng/mL, P = .003) and vitamin B12 levels (436.4 ± 199.2 vs 363.1 ± 107.6 pg/mL, P = .009) was lower in syncope patients when compared to the control group. In correlation analyses, syncope was shown as correlated with the vitamin D (r = -264, P = .003) and vitamin B12 levels (r = -233, P = .009). But, multivariate regression analyses showed that only vitamin D increased risk of syncope [OR: 0.946, 95% CI (0.901-0.994)]. There was no difference in terms of age, gender, BMI, echocardiographic findings between the in HUTT positive (n = 45) and negative groups (n = 29). Only vitamin D level was significantly lower in HUTT positive group (17.5 ± 7.7 vs 24.4 ± 9.1 ng/mL, P = .002). There was no difference among in the vasovagal subgroups in terms of vitamin D level and other features.

CONCLUSION

Vitamin D and B12 levels were reasonably low in syncope patients, but especially low Vitamin D levels were associated with VVS diagnosed in HUTT.

Diagnostic yield of pulmonary embolism testing in patients presenting to the emergency department with syncope

BACKGROUND

Syncope occurs in 1 in 4 people during their lifetime and accounts for 1% to 1.5% of emergency department (ED) visits. Most causes of syncope are benign, but syncope may be caused by life-threatening conditions including pulmonary embolism (PE) in up to 2% of cases. A recent publication reported the prevalence of PE in patients with syncope to be over 17%.

AIMS

We sought to determine the frequency and diagnostic yield of testing for PE in patients presenting to the ED with syncope in our large, integrated health care system.

METHODS

We performed a retrospective, longitudinal cohort study of patients who presented with syncope to EDs within a 21-hospital integrated health care system from 2010 to 2015 to find the frequency and diagnostic yield of testing for PE in patients with syncope at index ED visit and within 180 days afterward.

RESULTS

We screened 2 749 371 ED encounters to find 32 440 (1.2%) with syncope. Median age was 52 (interquartile range, 31-71), 57.5% were female, and 90% were Caucasian. PE was diagnosed on the index ED visit in 259 (0.8%; 95% confidence interval [CI], 0.7%-0.9%) cases. Assessment for suspected PE with D-dimer occurred in 5089 (15.7%) patients, and 2338 (7.2%) underwent computed tomography pulmonary angiography (CTPA). The yield of CTPA was 7.9%. PE was detected in 2.2% in whom a D-dimer was performed. From index visit to 180 days, 467 (1.4%; 95% CI, 1.3%-1.6%) patients were diagnosed with a PE, and 1051 (3.2%, 95% CI, 3.0%-3.4%) patients died.

CONCLUSION

Diagnostic testing for PE is frequent in patients with syncope presenting to the EDs of a large, integrated health care system. The yield of diagnostic testing is low.

Skin sympathetic nerve activity as a biomarker for syncopal episodes during a tilt table test

BACKGROUND

Autonomic imbalance is the proposed mechanism of syncope during a tilt table test (TTT). We have recently demonstrated that skin sympathetic nerve activity (SKNA) can be noninvasively recorded using electrocardiographic electrodes.

OBJECTIVE

The purpose of this study was to test the hypothesis that increased SKNA activation precedes tilt-induced syncope.

METHODS

We studied 50 patients with a history of neurocardiogenic syncope undergoing a TTT. The recorded signals were band-pass filtered at 500-1000 Hz to analyze nerve activity.

RESULTS

The average SKNA (aSKNA) value at baseline was 1.38 ± 0.38 μV in patients without syncope and 1.42 ± 0.52 μV in patients with syncope (P = .77). On upright tilt, aSKNA was 1.34 ± 0.40 μV in patients who did not have syncope and 1.39 ± 0.43 μV in patients who had syncope (P = .65). In all 14 patients with syncope, there was a surge of SKNA before an initial increase in heart rate followed by bradycardia, hypotension, and syncope. The peak aSKNA immediately (<1 minute) before syncope was significantly higher than baseline aSKNA (2.63 ± 1.22 vs 1.39 ± 0.43 μV; P = .0005). After syncope, patients were immediately placed in the supine position and aSKNA dropped significantly to 1.26 ± 0.43 μV; (P = .0004). The heart rate variability during the TTT shows a significant increase in parasympathetic tone during syncope (low-frequency/high-frequency ratio: 7.15 vs 2.21; P = .04).

CONCLUSION

Patients with syncope do not have elevated sympathetic tone at baseline or during the TTT except immediately before syncope when there is a transient surge of SKNA followed by sympathetic withdrawal along with parasympathetic surge.

Loperamide Mimicking Brugada Pattern

Brugada syndrome is an inherited arrhythmia that increases a patient's risk of sudden cardiac death. Certain pharmacologic agents may induce a transient Brugada pattern on surface electrocardiogram (EKG). One of these is loperamide, an over-the-counter agent commonly used to manage diarrhea. We report the case of a patient who experienced EKG changes that mimicked Brugada pattern after excessive intake of loperamide.

Left Ventricular Ejection Fraction and Fractional Shortening are Useful for the Prediction of the Therapeutic Response to Metoprolol in Children with Vasovagal Syncope

The objective of this manuscript was to explore if left ventricular ejection fraction (LVEF) and left ventricular fractional shortening (LVFS) could predict the efficacy of metoprolol therapy on vasovagal syncope (VVS) in children. Forty-nine children, including 30 with VVS and 19 gender- and age-matched healthy controls, were included in the study. Metoprolol was prescribed to the VVS subjects. The clinical data were obtained during follow-up at 2 and 6 months. The results showed that LVEF and LVFS of responders were significantly higher than those of non-responders both at the 2-month follow-up (LVEF: 72.5 ± 3.2% vs. 64.6 ± 3.4%; LVFS: 40.9 ± 2.3% vs. 34.9 ± 2.9%), and at the 6-month follow-up (LVEF: 72.8 ± 2.8% vs. 65.5 ± 4.6%; LVFS: 41.1 ± 1.9% vs. 35.8 ± 3.6%). The receiver operating characteristic curve (ROC) analysis demonstrated that 70.5% as a cutoff value of baseline LVEF yielded a sensitivity of 80% and a specificity of 100% in predicting the therapeutic effectiveness of metoprolol at 2 months. For baseline LVFS, 38.5% as a cutoff value yielded a sensitivity of 90% and a specificity of 90%. At the 6-month follow-up, the ROC analysis demonstrated that 70.5% as a cutoff value of baseline LVEF yielded a sensitivity of 81.3% and a specificity of 88.9% in the prediction of metoprolol efficacy. For baseline LVFS, 37.5% as a cutoff value yielded a sensitivity of 93.8% and a specificity of 66.7%. In conclusion, baseline LVEF and LVFS might be useful predictors of the efficacy of β-blocker therapy on VVS in children.

Orthostatic hypotension for the cardiologist

PURPOSE OF REVIEW

Orthostatic hypotension is a phenomenon commonly encountered in a cardiologist's clinical practice that has significant diagnostic and prognostic value for a cardiologist. Given the mounting evidence associating cardiovascular morbidity and mortality with orthostatic hypotension, cardiologists will play an increasing role in treating and managing patients with orthostatic hypotension.

RECENT FINDINGS

The American College of Cardiology, American Heart Association, and Heart Rhythm Society recently published consensus guidelines on the diagnosis, treatment, and management of syncope and their instigators, including orthostatic hypotension. Additionally, consensus guidelines have also been recently updated, reinforcing the universal definition orthostatic hypotension and its closely associated pathologies. Finally, the United States Food and Drug Administration (FDA) recently approved droxidopa, a synthetic oral norepinephrine prodrug, in 2014 for the treatment of neurogenic orthostatic hypotension (nOH), and it represents a well tolerated, effective, and easy to use intervention for nOH. This represents only the second drug approved by the FDA for orthostatic hypotension, the first being midodrine in 1986. A handful of smaller head-to-head studies have pitted not only pharmacologic agents to one another but also nonpharmacologic interventions to pharmacologic agents. Additionally, recent studies have also reported on more convenient screening tools for orthostatic hypotension.

SUMMARY

Though there have been many advances in the management of orthostatic hypotension, nOH remains a chronic, debilitating, and often progressively fatal condition. Cardiologists can play a very important role in optimizing hemodynamics in this patient population to improve quality of life and minimize cardiovascular risk.

[Circulatory failure : Out- and inpatient management]

Circulatory insufficiency is often understood as symptomatic hypotension due to various causes. The clinical result of circulatory dysregulation is arterial hypotension. The manifestation of hypotension is often divided into chronic and acute forms. Chronic hypotension can be distinguished etiopathogenetically into primary and secondary hypotension. Acute hypotension is usually equated to circulatory shock. While patients with chronic hypotension should be seen primarily by their general practitioner, patients with acute hypotension and a frequently severe clinical manifestation should be evaluated in the emergency department or, if there is a specific cause, directly in the acute clinic. Standardization of diagnostic and therapeutic pathways in both out- and inpatient care-not only for the management of circulatory weakness-would be an improvement not only in regards to patient care, but also with respect to healthcare economics.

Syncope workup: Greater yield in select trauma population

BACKGROUND

There is great variation in practice regarding the assessment of trauma patients who present with syncope. The purpose of this study was to determine the yield of screening studies (electrocardiogram, echocardiogram, and carotid duplex) and define characteristics to identify groups that may benefit from these investigations.

METHODS

We conducted a retrospective cohort study of all trauma patients from 2003 to 2015 who received a carotid duplex as part of a syncope evaluation at our urban Level 1 Trauma Center. Demographics, clinical findings as well as interventions undertaken (ie: placement of defibrillators/pacemakers) as a result of the syncope evaluation were collected. Data analysis was performed with STATA 14 and relationships between comorbidities, positive findings and interventions were assessed. Significance was assumed for p < 0.05.

RESULTS

736 trauma patients were included in the study. The most common mechanism of injury was fall (592, 82%). A history of congestive heart failure (CHF) and/or coronary artery disease (CAD) and age ≥ 65 were significantly associated with abnormal ECG and ECHO findings, but not with severe carotid stenosis. Elevated Injury Severity Scale (ISS) was significantly associated with an abnormal ECHO on both univariate and multivariate analysis. An abnormal ECG was predictive of an abnormal ECHO (p = 0.02). Ten patients (1.4%) underwent placement of a defibrillator and/or pacemaker, all of whom reported having CHF. Only 11 patients (1.7%) had severe carotid stenosis (>70%) requiring intervention.

CONCLUSION

The screening studies used in a syncope evaluation have low yield in the general trauma population. Carotid duplex should not be routinely performed. Cardiac evaluation should be tailored to individuals with cardiac comorbidities, older age and elevated ISS. An ECG should be used as initial screening in this patient cohort.

Pacing as a treatment for reflex-mediated (vasovagal, situational, or carotid sinus hypersensitivity) syncope: A systematic review for the 2017 ACC/AHA/HRS guideline for the evaluation and management of patients with syncope: A report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society

OBJECTIVES

To determine, using systematic review of the biomedical literature, whether pacing reduces risk of recurrent syncope and relevant clinical outcomes among adult patients with reflex-mediated syncope.

METHODS

MEDLINE (through PubMed), EMBASE, and the Cochrane Central Register of Controlled Trials (through October 7, 2015) were searched for randomized trials and observational studies examining pacing and syncope, and the bibliographies of known systematic reviews were also examined. Studies were rejected for poor-quality study methods and for the lack of the population, intervention, comparator, or outcome(s) of interest.

RESULTS

Of 3,188 citations reviewed, 10 studies met the inclusion criteria for systematic review, including a total of 676 patients. These included 9 randomized trials and 1 observational study. Of the 10 studies, 4 addressed patients with carotid sinus hypersensitivity, and the remaining 6 addressed vasovagal syncope. Among the 6 open-label (unblinded) studies, we found that pacing was associated with a 70% reduction in recurrent syncope (relative risk [RR]: 0.30; 95% confidence interval [CI]: 0.15-0.60). When the 2 analyzable studies with double-blinded methodology were considered separately, there was no clear benefit (RR: 0.73; 95% CI: 0.25-2.1), but confidence intervals were wide. The strongest evidence was from the randomized, double-blinded ISSUE-3 (Third International Study on Syncope of Uncertain Etiology) trial, which demonstrated a benefit of pacing among patients with recurrent syncope and asystole documented by implantable loop recorder.

CONCLUSIONS

There are limited data with substantive evidence of outcome ascertainment bias, and only 2 studies with a double-blinded study design have been conducted. The evidence does not support the use of pacing for reflex-mediated syncope beyond patients with recurrent vasovagal syncope and asystole documented by implantable loop recorder.