Syncope. Physiological considerations and an analysis of the clinical characteristics in 510 patients

Impact of Admission of Patients With Syncope in Non-Teaching Hospitals Versus Teaching Hospitals: A Nationwide Analysis

Syncope is a common condition affecting many individuals, and it remains uncertain whether admission to academic medical centers (AMCs) leads to better outcomes than non-AMCs. This study is aimed to investigate whether there is a difference in mortality, length of stay (LoS), and total hospital charges between patients admitted with syncope to AMCs and non-AMCs. This retrospective cohort study used the National Inpatient Database (NIS) to examine patients aged 18 years and older admitted with a primary diagnosis of syncope to AMCs and non-AMCs from 2016 to 2020. Univariate and multivariate logistic regression analyses were conducted, adjusting for confounders, to assess the primary outcome of all-cause in-hospital mortality and secondary outcomes, including hospital LoS and total cost of admission. Patient characteristics were also described. Of the 451,820 patients who met the inclusion criteria, 69.6% were admitted to AMCs and 30.4% to non-AMCs. Patient age was similar between the two groups (68 years in AMC versus 70 years in non-AMC; p < 0.001), as was sex distribution (52% female in AMC versus 53% in non-AMC; 48% male in AMC versus 47% in non-AMC; p < 0.002). Most patients in both groups were white, while the percentages of black and Hispanic patients were slightly higher in non-AMCs. The study found no difference in all-cause mortality between patients admitted to AMCs and non-AMCs (p = 0.33). However, LoS was marginally longer in AMC patients (2.6 days in AMC versus 2.4 days in the non-AMC group; p < 0.001), and the total cost was higher for AMCs by $3,526 per admission. The estimated total economic burden related to syncope was over 3 billion USD per year. This study suggests that the teaching status of hospitals did not significantly affect the mortality of patients admitted with syncope. However, it may have contributed to marginally longer hospital LoS and higher total hospital charges.

Tilt Test: A Review

SUMMARY

This review recapitulates the head-up tilt test, which is commonly used for evaluation of orthostatic syndromes and dysautonomia. Tilt test evaluates autonomic system responses to orthostatic stress. Established tilt testing includes monitoring of heart rate and blood pressure; adding capnography and cerebral blood flow monitoring expands its diagnostic yield and allows assessing cerebral blood flow regulation. Common syndromes detectable by the tilt test are neurally mediated syncope (vasodepressor, cardiovagal, or mixed), orthostatic hypotension, postural orthostatic tachycardia syndrome, hypocapnic cerebral hypoperfusion, and orthostatic cerebral hypoperfusion syndrome. This review describes relevant physiology, tilt test protocols, diagnostic criteria for orthostatic syndromes, grading test results, diagnostic accuracy, limitations of the tilt test, and safety considerations.

Association Between Baseline Blood Pressures, Heart Rates, and Vasovagal Syncope in Children and Adolescents

BACKGROUND

Vasovagal syncope is the most common cause of syncope in children and adults, accounting for 50-66% of unexplained syncope. There are no studies establishing the relationship between syncope, baseline heart rate, and blood pressure.

OBJECTIVE

To identify a possible association between baseline blood pressure and heart rate with syncope.

DESIGN/METHODS

We conducted a questionnaire-based chart review study. A questionnaire was distributed to the guardian of children between eight and 18 years of age who attended the Pediatric Ambulatory Care Clinic at Flushing Hospital Medical Center. Based on the responses in the questionnaire, subjects were classified either as cases (positive for syncope) or controls (negative for syncope). Children and adolescents with neurological, cardiac, or any medical condition that can cause syncopal episodes were excluded from the study. Data collected from the questionnaire included age, gender, ethnicity, medical history, family history of syncope, and the amount of salt used in food. Anthropometric and vital signs for the current visit (height, weight, BMI, blood pressure, and heart rate) and vital signs from two previous visits were collected from electronic medical records. The data was analyzed using t-test and chi-square test with Microsoft Excel software (Microsoft Office Standard, v. 14, Microsoft; 2010); p<0.05 was considered significant.

RESULTS

A total of 197 subjects were included in this study. There were 18 cases and 179 controls. Of the cases, (4/18) 22.2% were more likely to have a systolic blood pressure lower than the 10th percentile for their gender, age, and height as compared with controls (7/179) 3.9%, p = 0.003. The subjects with a history of syncope were more likely to add salt to their food (p = 0.004). There were no significant differences between cases and controls for age, gender, ethnicity between cases and controls for systolic blood pressure. No significant difference was observed between the heart rates of cases and controls.

CONCLUSIONS

Children and adolescents with syncope were more likely to have a systolic blood pressure lower than the 10th percentile, and there was no difference in the baseline heart rate. In addition, children with syncope were more likely to add salt to their food.

Pediatric syncope: is detailed medical history the key point for differential diagnosis?

Syncope is a transient loss of consciousness as a result of global cerebral hypoperfusion. It is generally benign but may be a sign of pathology. The purpose of this study was to analyze the frequency of syncope due to cardiac, neurocardiogenic, neurologic, situational, psychiatric, and other causes and make a differential diagnosis of syncope types according to detailed medical history and further investigations. We examined prospectively 268 children presented to pediatric polyclinics as well as cardiology and neurology departments (age range, 1-18 years) with a primary complaint of syncope for the study. Cardiac syncope was diagnosed in 12 patients, neurocardiogenic syncope in 232, neurologic syncope in 9, psychiatric syncope in 9, situational in 4, and benign paroxysmal positional vertigo in 2. The neurologic syncope group consists of patients diagnosed with epilepsy after evaluation. Eight patients in the cardiac syncope group were found to have diseases such as long QT syndrome, and the remaining patients had hypertrophic cardiomyopathy, atrioventricular nodal reentry tachycardia, ventricular tachycardia, and a second-degree heart block that can cause sudden death. In conclusion, syncope is a common problem in childhood that requires hospitalization. Because it may be the first finding of an underlying malignant cardiac or neurologic disease, clinicians must be very careful during medical evaluation. An electrocardiogram and a medical history including the details of the event, chronic diseases, and familial diseases are among the most important steps for the right diagnosis and prognosis. Instead of a routine procedure, further diagnostic workup should be directed according to medical history for high yield. Convulsive movements may be defined in all types of syncope related with cerebral hypoxia, and this may lead to a misdiagnosis of seizure by the clinician.

Cough syncope

Loss of consciousness following cough was first described in 1876 as "laryngeal vertigo" Since then, several hundred cases of what is now most commonly termed cough syncope have been reported, often in association with various medical conditions. Some early authors assumed this entity to be a form of epilepsy, but by the mid-20th century, general consensus reflected that post-tussive syncope was a consequence of markedly elevated intrathoracic pressures induced by coughing. A typical profile of the cough syncope patient emerging from the literature is that of a middle-aged, large-framed or overweight male with obstructive airways disease. Presumably, such an individual would be more likely to generate the extremely high intrathoracic pressures associated with cough-induced fainting. The precise mechanism of cough syncope remains a matter of debate. Theories proposed include various consequences of the marked elevation of intrathoracic pressures induced by coughing: diminished cardiac output causing decreased systemic blood pressure and, consequently, cerebral hypoperfusion; increased cerebrospinal fluid (CSF) pressure causing increased extravascular pressure around cranial vessels, resulting in diminished brain perfusion; or, a cerebral concussion-like effect from a rapid rise in CSF pressure. More recent mechanistic studies suggest a neurally mediated reflex vasodepressor-bradycardia response to cough. Since loss of consciousness is a direct and immediate result of cough, elimination of cough will eliminate the resultant syncopal episodes. Thus, the approach to the patient with cough syncope requires thorough evaluation and treatment of potential underlying causes of cough, as summarized in several recently published cough management guidelines.

Recognizing life-threatening causes of syncope

While the overall prognosis of syncope is favorable, the identification of individuals with a potentially life-threatening cause is of paramount importance. Cardiac syncope is associated with an elevated risk of mortality, and includes both primary arrhythmic and obstructive etiologies. Identification of these individuals is contingent on careful clinical assessment and judicious use of diagnostic investigations. This article focuses on life-threatening causes of syncope and a diagnostic approach to facilitate their identification.

Validation of the San Francisco Syncope Rule in two hospital emergency departments in an Asian population

OBJECTIVES

The objective was to externally validate the ability of the San Francisco Syncope Rule (SFSR) to accurately identify patients who will experience a 7-day serious clinical event in an Asian population.

METHODS

This was a prospective cohort study, with a sample of adult patients with syncope and near-syncope enrolled. Patients 12 years old and below and patients with loss of consciousness after head trauma, a witnessed seizure, with known alcohol or illicit drug ingestion, and altered level of consciousness or persistent new neurologic deficits were excluded. The patients were evaluated for the presence of one or more of the five SFSR variables: shortness of breath, history of heart failure, hematocrit <30%, systolic blood pressure <90 mm Hg, and abnormal electrocardiogram (ECG). The patients were followed up by medical record review or telephone interview. Seven-day outcomes were death, arrhythmia, myocardial infarction, acute pulmonary edema, significant structural heart disease, pulmonary embolism, major cardiac procedure, stroke, subarachnoid hemorrhage, major bleeding, and anemia.

RESULTS

A total of 1,250 patients from two centers were recruited. Fifty-six patients were excluded from primary analysis because of incomplete data (n = 55) and/or they were noncontactable for follow-up (n = 32). Of the 1,194 patients analyzed, 138 patients (11.6%) experienced adverse outcomes at 7 days. The rule performed with a sensitivity of 94.2% (95% confidence interval [CI] = 89.0% to 97.0%) and a specificity of 50.8% (95% CI = 47.7% to 53.8%).

CONCLUSIONS

In this study, SFSR rule had a sensitivity of 94.2%. This suggests caution on the strict application of the rule to all patients presenting with syncope. It should only be used as an aide in clinical decision-making in this population.

Autonomic dysfunction in older people

The autonomic nervous system comprises the sympathetic, parasympathetic and enteric nervous systems and plays an integral role in homeostasis. This includes cardiovascular and temperature control, glucose metabolism, gastrointestinal and reproductive function and increasing evidence to support its involvement in the inflammatory response to infection and cancer. Ageing is associated with autonomic dysfunction, and many clinical syndromes associated with older adults are due to inadequate autonomic responses to physiological stressors. The aim of this review is to explore the relationship between autonomic dysfunction and ageing illustrated with examples of maladaptive autonomic responses in a variety of different clinical syndromes including an exploration of autonomic cellular changes. Appropriate investigation and management strategies are outlined, recognizing the fine balance needed to improve symptoms without creating further medical complications.

Needle phobia: etiology, adverse consequences, and patient management

Needle phobia has profound health, dental, societal, and legal implications, and severe psychological, social, and physiologic consequences. There is genetic evidence for the physiologic response to needle puncture, and a significant familial psychological component, showing evidence of inheritance. Needle phobia is also a learned behavior. The dental practitioner must recognize patients with needle phobia before the administration of local anesthetics to identify patients who are potentially reactive and to prevent untoward sequelae. Needle phobia is highly associated with avoidance behavior, and the dentist must exhibit compassion and respect. To avoid bradycardia, hypotension, unconsciousness, convulsions, and possibly asystole, oral premedication with benzodiazepines or other antianxiety agents must be considered for patients who are needle phobic. Management of needle phobiaeinduced syncope includes perioperative monitoring, oxygen administration, positioning, atropine, and vasopressors.

Predictive models of syncope causes in an outpatient clinic

The investigation of unexplained syncope remains a challenging clinical problem. In the present study we sought to evaluate the diagnostic value of a standardized work-up focusing on non invasive tests in patients with unexplained syncope referred to a syncope clinic, and whether certain combinations of clinical parameters are characteristic of rhythmic and reflex causes of syncope.

METHODS AND RESULTS

317 consecutive patients underwent a standardized work-up including a 12-lead ECG, physical examination, detailed history with screening for syncope-related symptoms using a structured questionnaire followed by carotid sinus massage (CSM), and head-up tilt test. Invasive testings including an electrophysiological study and implantation of a loop recorder were only performed in those with structural heart disease or traumatic syncope. Our work-up identified an etiology in 81% of the patients. Importantly, three quarters of the causes were established non invasively combining head-up tilt test, CSM and hyperventilation testing. Invasive tests yielded an additional 7% of diagnoses. Logistic analysis identified age and number of significant prodromes as the only predictive factors of rhythmic syncope. The same two factors, in addition to the duration of the ECG P-wave, were also predictive of vasovagal and psychogenic syncope. These factors, optimally combined in predictive models, showed a high negative and a modest positive predictive value.

CONCLUSION

A standardized work-up focusing on non invasive tests allows to establish more than three quarters of syncope causes. Predictive models based on simple clinical parameters may help to distinguish between rhythmic and other causes of syncope.

High diagnostic yield and accuracy of history, physical examination, and ECG in patients with transient loss of consciousness in FAST: the Fainting Assessment study

BACKGROUND

Transient loss of consciousness (TLOC) is a common clinical problem.

OBJECTIVE

The aim of this study was to assess the yield and accuracy of the initial evaluation, consisting of standardized history, physical examination, and ECG performed by attending physicians in patients with TLOC.

METHODS AND RESULTS

Five hundred and three adult patients (mean age 53 +/- 19; 56% male) presenting with TLOC to the Academic Medical Center Amsterdam between February 2000 and May 2002 were included in this study. After initial evaluation, the physician made a certain, a highly likely (>80% certain), or no initial diagnosis. Initially undiagnosed patients received additional cardiological testing, additional history taking, and autonomic function tests. After 2 years of follow-up, an expert committee determined the final diagnoses. Two-year follow-up was obtained in 99% of the patients. The yield of certain diagnoses after the initial evaluation was 24%, increasing to 63% after including the highly likely diagnoses. The diagnostic accuracy of the initial certain diagnoses was 93% (95% CI 87-97%), decreasing to 88% (95% CI 84-91%) after inclusion of the initial highly likely diagnoses.

CONCLUSION

Attending physicians can make a diagnosis based on initial evaluation in 63% of patients with TLOC, with an overall diagnostic accuracy of 88%. The use of additional testing, beyond history, physical examination, and ECG can be avoided in many patients with TLOC.

Death after emergency department visits for syncope: how common and can it be predicted?

STUDY OBJECTIVE

Syncope is a common condition that is usually benign but occasionally associated with death. This study evaluates the incidence of death after an emergency department (ED) visit for syncope and whether these deaths can be predicted.

METHODS

A prospective cohort study was conducted during a 45-month period. All patients were followed up 1-and-a-half years after their initial ED visit to determine whether they had died. Death certificates were independently reviewed by 2 physicians for the cause and date of death to determine whether the death was possibly related to the initial visit for syncope. Sensitivity and specificity of risk factors (defined by the San Francisco Syncope Rule) or age greater than 65 years was calculated for all-cause mortality and mortality thought possibly related to syncope.

RESULTS

There were 1418 consecutive patients with syncope during the study period, representing 1.2% of all ED visits. The all-cause death rate was 1.4% at 30 days, 4.3% at 6 months, and 7.6% at 1 year. It was believed that the death rates from causes possibly related to syncope were 2.3% and 3.8% at 6 months and 1 year. Of the 112 deaths at 1 year, 37% were cardiac related. At 6 months, the risk factors had a sensitivity of 89% (95% confidence interval [CI] 79% to 95%) and specificity of 53% (95% CI 52% to 53%) for all-cause mortality and sensitivity of 100% (95% CI 90% to 100%) and specificity 52% (95% CI 52% to 53%) for predicting deaths likely or possibly related to syncope. Age greater than 65 years had similar sensitivity but much worse specificity compared with the set combined risk factors.

CONCLUSION

Deaths related to syncope after an ED visit are low, especially in the first 6 months and can usually be predicted by risk factors.

Prospective validation of the San Francisco Syncope Rule to predict patients with serious outcomes

STUDY OBJECTIVE

We prospectively validate the San Francisco Syncope Rule (history of congestive heart failure, Hematocrit <30%, abnormal ECG result [new changes or non-sinus rhythm], complaint of shortness of breath, and systolic blood pressure <90 mm Hg during triage).

METHODS

In a prospective cohort study, consecutive patients with syncope or near syncope presenting to an emergency department (ED) of a teaching hospital were identified and enrolled from July 15, 2002, to August 31, 2004. Patients with trauma, alcohol, or drug-associated loss of consciousness and definite seizures were excluded. Physicians prospectively applied the San Francisco Syncope Rule after their evaluation, and patients were followed up to determine whether they had had a predefined serious outcome within 30 days of their ED visit.

RESULTS

Seven hundred ninety-one consecutive visits were evaluated for syncope, representing 1.2% of all ED visits. The average age was 61 years, 54% of patients were women, and 59% of patients were admitted. Fifty-three visits (6.7%) resulted in patients having serious outcomes that were undeclared during their ED visit. The rule was 98% sensitive (95% confidence interval [CI] 89% to 100%) and 56% specific (95% CI 52% to 60%) to predict these events. In this cohort, the San Francisco Syncope Rule classified 52% of the patients as high risk, potentially decreasing overall admissions by 7%. If the rule had been applied only to the 453 patients admitted, it might have decreased admissions by 24%.

CONCLUSION

The San Francisco Syncope Rule performed with high sensitivity and specificity in this validation cohort and is a valuable tool to help risk stratify patients. It may help with physician decisionmaking and improve the use of hospital admission for syncope.

The San Francisco Syncope Rule vs physician judgment and decision making

OBJECTIVE

To compare a clinical decision rule (San Francisco Syncope Rule [SFSR]) and physician decision making when predicting serious outcomes in patients with syncope.

METHODS

In a prospective cohort study, physicians evaluated patients presenting with syncope and predicted the chance (0%-100%) of the patient developing a predefined serious outcome. They were then observed to determine their decision to admit the patient. All patients were followed up to determine whether they had a serious outcome within 7 days of their emergency department visit. Analyses included sensitivity and specificity to predict serious outcomes for low-risk patients and comparison of areas under the receiver operating characteristic curve for the decision rule, physician judgment, and admission decisions.

RESULTS

During the study period, there were 684 visits for syncope with 79 visits resulting in serious outcomes. The area under the receiver operating characteristic curve was 0.92 (95% confidence interval [CI], 0.88-0.95) for the SFSR compared with physician judgment 0.89 (95% CI, 0.85-0.93) and physician decision making 0.83 (95% CI, 0.81-0.87). Physicians admitted 28% of patients in a low-risk group, with a median length of stay of 1 day (interquartile range, 1-2.5 days). The SFSR had the potential to absolutely decrease admissions by 10% in this low-risk group and still predict all serious outcomes.

CONCLUSIONS

Physician judgment is good when predicting which patients with syncope will develop serious outcomes, but contrary to their judgment, physicians still admit a large number of low-risk patients. The SFSR performs better than current physician performance and has great potential to aid physician decision making.

Diagnostic value of history taking in reflex syncope

The medical history, in combination with the physical examination and a 12-lead electrocardiogram, plays a key role in the diagnosis and risk stratification of patients with syncope. However, diagnostic clinical criteria are not uniformly applied. In older studies, the diagnostic criteria for vasovagal or reflex syncope often included typical precipitating events and warning symptoms. More recent studies have documented that a variety of unrecognized stressors can trigger reflex syncope and that warning signs and symptoms may be minimal. A characteristic medical history (a trigger and/or prodromi) is enough to diagnose reflex syncope if the risk for a cardiac cause of syncope is low (e. g. patients < 65 yrs, without a history of heart disease and no ECG abnormalities). In elderly subjects with a higher risk of cardiac syncope, the yield of the medical history is lower. However, a prospective study of the value of the medical history for the diagnosis of syncope with long-term follow-up has not been performed.

Derivation of the San Francisco Syncope Rule to predict patients with short-term serious outcomes

STUDY OBJECTIVE

The causes of syncope are usually benign but are occasionally associated with significant morbidity and mortality. We derive a decision rule that would predict patients at risk for short-term serious outcomes and help guide admission decisions.

METHODS

This prospective cohort study was conducted at a university teaching hospital and used emergency department (ED) patients presenting with syncope or near syncope. Physicians prospectively completed a structured data form when evaluating patients with syncope. Serious outcomes (death, myocardial infarction, arrhythmia, pulmonary embolism, stroke, subarachnoid hemorrhage, significant hemorrhage, or any condition causing a return ED visit and hospitalization for a related event) were defined at the start of the study. All patients were followed up to determine whether they had experienced a serious outcome within 7 days of their ED visit. Univariate analysis was performed with chi2 and nonparametric techniques on all predictor variables. kappa Analysis was performed on variables requiring interpretation. Variables with kappa more than 0.5 and a P value less than.1 were analyzed with recursive partitioning techniques to develop a rule that would maximize the determination of serious outcomes.

RESULTS

There were 684 visits for syncope, and 79 of these visits resulted in patients' experiencing serious outcomes. Of the 50 predictor variables considered, 26 were associated with a serious outcome on univariate analysis. A rule that considers patients with an abnormal ECG, a complaint of shortness of breath, hematocrit less than 30%, systolic blood pressure less than 90 mm Hg, or a history of congestive heart failure has 96% (95% confidence interval [CI] 92% to 100%) sensitivity and 62% (95% CI 58% to 66%) specificity. If applied to this cohort, the rule has the potential to decrease the admission rate by 10%.

CONCLUSION

The San Francisco Syncope Rule derived in this cohort of patients appears to be sensitive for identifying patients at risk for short-term serious outcomes. If prospectively validated, it may offer a tool to aid physician decision making.

Syncope and burns

Syncope is a common condition that may lead to serious injuries including burns and head injury. To date, here has been no specific discussion of syncope and burns in the literature. A retrospective case-note review of consecutive patients admitted to a Tertiary Burns Centre over a 3.5-year-period was conducted. Five hundred and fifty nine patients were admitted during the study period. Six of these had burns related to alterations of consciousness that excluded alcohol/drug ingestion and epilepsy. The mean percentage body surface area burnt was 9.7%, the mean length of hospital stay was 28.5 days and the mean length of stay per percentage surface area burnt was 4.0 days per percent body surface burnt. The mean size of the injury in syncopal patients is slightly larger than the general burns patients (8.4%) but the length of stay is doubled. This is partly related to surgery being delayed due to investigation of the syncope episode. Focused investigations should reduce both the overall length of hospital stay and the number of investigations.

Historical criteria that distinguish syncope from seizures

OBJECTIVES

We prospectively sought evidence-based criteria that distinguished between seizures and syncope.

BACKGROUND

Loss of consciousness is usually due to either seizures or syncope. There are no evidence-based historical diagnostic criteria that distinguish them.

METHODS

A total of 671 patients with loss of consciousness completed a 118-item historical questionnaire. Data sets were complete for all subjects. The data set was randomly divided into two equal groups. The contributions of symptoms to diagnoses in one group were estimated with logistic regression and point scores were developed. The accuracy of the decision rule was then assessed using split-half analysis. Analyses were performed with and without inclusion of measures of symptom burden, which were the number of losses of consciousness and the duration of the history. The scores were tested using receiver-operator characteristic analysis.

RESULTS

The causes of loss of consciousness were known satisfactorily in 539 patients and included seizures (n = 102; complex partial epilepsy [50 patients] and primary generalized epilepsy [52 patients]) and syncope (n = 437; tilt-positive vasovagal syncope [267 patients], ventricular tachycardia [90 patients] and other diagnoses such as complete heart block and supraventricular tachycardias [80 patients]). The point score based on symptoms alone correctly classified 94% of patients, diagnosing seizures with 94% sensitivity and 94% specificity. Including symptom burden did not significantly improve accuracy, indicating that the symptoms surrounding the loss of consciousness accurately discriminate between seizures and syncope.

CONCLUSIONS

A simple point score of historical features distinguishes syncope from seizures with very high sensitivity and specificity.

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.

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.

Yohimbine in neurally mediated syncope. Pathophysiological implications

In this study, we evaluated if increased sympathetic stimulation is an essential requirement for the development of neurally mediated syncope (NMS) by manipulating overall sympathetic outflow in subjects susceptible to tilt-induced syncope. Eight previously characterized patients with recurrent NMS (five females and three males; 34+/-2 yr) were recruited from the Vanderbilt Syncope Unit and eight age-matched controls underwent initial administration of clonidine (CLO) or yohimbine (YHO). This was done, prospectively, to determine doses of these agents that would increase or decrease plasma norepinephrine levels by >/= 30%. On a different day, in all subjects we determined intraarterial blood pressure, EKG and muscle sympathetic nerve activity (MSNA) both supine and during upright tilt. After this, subjects randomly received either CLO or YHO, and 3 h later another tilt was performed. After 1 wk, a similar procedure with the other drug was performed. During the two basal tilts, all the control subjects completed the study, whereas all the NMS patients developed syncope. Reduction in sympathetic tone by CLO resulted in a decreased tolerance to tilt in three out of eight controls and in all the NMS patients. In contrast, YHO not only increased basal plasma NorEpi levels and MSNA, but also prevented syncope in seven out of eight patients. In a selected population of patients, increased sympathetic activity is not a prerequisite for the development of syncope. Yohimbine-induced enhancement of sympathetic tone in patients with NMS improves orthostatic tolerance and raises the possibility that this drug may be a useful agent in the treatment of NMS.

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.

[Indications for emergency EEG in disease, a brief loss of consciousness in generalized epileptic seizures in the adult]

EEG provides essential information for the management of patients in whom a first epileptic seizure is suspected because of transient alteration of consciousness. Postictal or interictal EEG abnormalities are useful to the clinician even when the diagnosis of epileptic seizure appears clinically evident. EEG is especially useful when recordings are performed immediately after the episode, in the absence of benzodiazepine therapy, and repeated later. After a transient loss or alteration of consciousness, the EEG should be considered as part of the emergency management, and thus rapidly obtained, whenever the evolution and/or the clinical signs of the episode are consistent with a focal epileptic seizure, especially if gestual or oro-facial automatisms, or bizarre deambulatory behavior have preceded the episode. EEG should also be considered as an emergency examination when a tonic-clonic seizure is suspected clinically, eg, when loss of consciousness is prolonged and inconsistent with a syncopal attack; when it is accompanied by clonic movements or spasms and followed by postictal confusion or stertor; when it entails a head injury or a tongue biting, or when it is preceded by premonitory signs or symptoms consistent with epilepsy. In the absence of such clinical suspicion, an EEG is not justified.

Vagal and sympathetic mechanisms in patients with orthostatic vasovagal syncope

BACKGROUND

Autonomic and particularly sympathetic mechanisms play a central role in the pathophysiology of vasovagal syncope. We report direct measurements of muscle sympathetic nerve activity in patients with orthostatic vasovagal syncope.

METHODS AND RESULTS

We studied 53 otherwise healthy patients with orthostatic syncope. We measured RR intervals and finger arterial pressures and in 15 patients, peroneal nerve muscle sympathetic activity before and during passive 60 degree head-up tilt, with low-dose intravenous isoproterenol if presyncope did not develop by 15 minutes. We measured baroreflex gain before tilt with regression of RR intervals or sympathetic bursts on systolic or diastolic pressures after sequential injections of nitroprusside and phenylephrine. Orthostatic vasovagal reactions occurred in 21 patients, including 7 microneurography patients. Presyncopal and nonsyncopal patients had similar baseline RR intervals, arterial pressure, and muscle sympathetic nerve activity. Vagal baroreflex responses were significantly impaired at arterial pressures below (but not above) baseline levels in presyncopal patients. Initial responses to tilt were comparable; however, during the final 200 seconds of tilt, presyncopal patients had lower RR intervals and diastolic pressures than nonsyncopal patients and gradual reduction of arterial pressure and sympathetic activity. Frank presyncope began abruptly with precipitous reduction of arterial pressure, disappearance of muscle sympathetic nerve activity, and RR interval lengthening.

CONCLUSIONS

Patients with orthostatic vasovagal reactions have impaired vagal baroreflex responses to arterial pressure changes below resting levels but normal initial responses to upright tilt. Subtle vasovagal physiology begins before overt presyncope. The final trigger of human orthostatic vasovagal reactions appears to be the abrupt disappearance of muscle sympathetic nerve activity.

Neurally mediated syncopal syndromes: pathophysiological concepts and clinical evaluation

The neurally mediated syncopal syndromes encompass a number of apparently related disturbances of reflex cardiovascular control characterized by transient inappropriate bradycardia and/or vasodilation of various arterial and venous beds. Certain of these syndromes (e.g., carotid sinus syndrome, postmicturition syncope) are encountered occasionally in clinical practice, whereas others are quite rare (e.g., swallow syncope). On the other hand, vasovagal syncope occurs so frequently, that as a group, the neurally mediated syncopal syndromes are among the most important causes of syncope. The pathophysiology of the neurally mediated syncopal syndromes is incompletely understood, but can be considered in terms of four basic elements: (1) the afferent limb; (2) central nervous system (CNS) processing; (3) the efferent limb; (4) feedback loops. The afferent limb consists of several peripheral and CNS trigger sites and the associated connections to medullary cardiovascular centers. CNS processing and efferent signals result in both bradycardia, which may be marked or relative, and vasodilatation. Failure of baroreceptor feedback controls to prevent hypotension is important in facilitating development of symptomatic hypotension. Head-up tilt table testing has become the diagnostic technique of choice for clinically assessing susceptibility to neurally mediated syncope, particularly of the vasovagal type. Most studies suggest that such testing discriminates relatively well between symptomatic patients and asymptomatic control subjects, of whom 10%-15% have a false-positive test results. Sensitivity of tilt table testing is more difficult to evaluate because there is no accepted diagnostic gold standard. However, sensitivity (measured against a classic presentation) has been estimated to range from 32%-85%, with most reports favoring the higher end of this range. Treatment strategies for neurally mediated syncope remain controversial. Many single episodes do not warrant treatment unless physical injury has occurred, or a high risk occupation or avocation is involved. Tilt test exposure alone may prove beneficial in educating patients with recurrent syncope to recognize warning signs of an imminent faint. Large controlled clinical studies have not been performed to test the efficacy of pharmacological therapy (e.g., beta-adrenergic blockers, disopyramide, serotonin reuptake blockers, vasoconstrictors) or pacing therapy. Such studies may be difficult to undertake due to the variable frequency of spontaneous symptoms and apparent long periods of remission. Nonetheless, many investigators and clinicians have come to rely on these agents, and on tilt testing to guide treatment decisions. Studies employing careful correlation of long-term clinical follow-up with results of early and perhaps later repeat tilt studies are still needed.

Randomized double-blind, placebo-controlled trial of oral atenolol in patients with unexplained syncope and positive upright tilt table test results

The objective of this investigation was the assessment of the response rate of oral atenolol in patients with vasovagal syncope after 1 month of treatment. We randomized into two groups all patients referred to our unit who had had at least one episode of syncope or two episodes of presyncope 1 month before presentation and had a positive isuprel Tilt Table Test (TTT). Group 1 (Gr 1) received oral atenolol, and group 2 (Gr 2) received placebo medication. After a 1-month period patients were reassessed for degree of their symptoms and underwent repeated TTT. Forty-two patients were enrolled in the study. Gr 1 and Gr 2 were comparable in age (38 +/- 13 years vs 43 +/- 14 years, p = 0.216 and sex (male/female = 6:15 vs 10:11, p = 0.204). The severity of attack was similar in both groups. Eight patients in Gr 1 and six patients in Gr 2 had mitral valve prolapse (p = 0.5). No significant differences were seen in systolic blood pressure (122 +/- 17 vs 117 +/- 16 mmHg, p = 0.334), diastolic blood pressure (70 +/- 11 vs 72 +/- 11 mm Hg, p = 0.677), and heart rate (79 +/- 12 vs 79 +/- 13, p = 0.98) between the two groups. The response rates (negative TTT) after 1 month of treatment were 62% versus 5% (p = 0.0004) in the atenolol and control group, respectively. Moreover, patients who received atenolol reported feeling better compared with those who received placebo (71% vs 29%, p = 0.02). In conclusion, atenolol significantly improved symptoms of patients with vasovagal syncope.(ABSTRACT TRUNCATED AT 250 WORDS)

Upright postures and isoproterenol infusion for provocation of neurocardiogenic syncope: a comparison of standing and head-up tilting

Head-up tilt testing has proved to be useful in provocation of neurocardiogenic syncope. The purpose of this study was to examine whether simply assuming an upright posture by standing can be an alternative to the head-up tilt testing for diagnosis of neurocardiogenic syncope. Eighty-four patients with recurrent unexplained syncope and 22 normal volunteers were recruited into the study. Forty-seven patients with syncope and all normal volunteers received the standing test. Thirty-seven of the patients with syncope received head-up tilt testing (90 degrees). All subjects lay down for 5 minutes and then assumed an upright posture until syncope or presyncope occurred or until a maximum of 10 minutes was reached in each stage of the test. The tests included four stages: baseline and infusion of 1, 2, or 3 micrograms/min isoproterenol in each of the successive stages. Five subjects could not tolerate the procedure, and further testing was terminated. Overall, the standing test was positive in 83% of the patients with syncope, and its specificity was 74%. The head-up tilt testing was positive in 75% of the patients with syncope. The duration of assuming an upright posture before occurrence of syncope or presyncope was significantly longer in the syncope-tilting group in the third stage (p < 0.01) and the fourth stage (p < 0.05) compared with the syncope-standing group. However, the curves of the time course for cumulative positive rates were not significantly different (p = 0.0739) in the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)

The contribution of isoproterenol to the prolonged tilt test

In this study the tilt test, in combination with isoproterenol administration, was used to investigate 44 patients with unexplained syncope. The reproducibility of the method was studied in a group of 32 patients who underwent a second test. The administration of isoproterenol during the test increased the sensitivity of the method from 52 to 70% and the reproducibility of a positive result from 61% to 83%, at the expense of a small decrease in specificity (from 100% to 93%). Isoproterenol should thus be considered an essential part of the method, although the low reproducibility of specific types of haemodynamic response limits its value in the choice and the follow up of treatment in individual cases.

Neurohumoral antecedents of vasodepressor reactions

Vasodepressor (vasovagal) syncope, the most common cause of acute loss of consciousness, can occur in otherwise vigorously healthy people during exposure to stimuli decreasing cardiac filling. Antecedent physiological or neuroendocrine conditions for this dramatic syndrome are poorly understood. This study compared neurocirculatory responses to non-hypotensive lower body negative pressure (LBNP) in subjects who subsequently developed vasodepressor reactions during hypotensive LBNP with responses in subjects who did not. In 26 healthy subjects, LBNP at -15 and -40 mmHg was applied to inhibit cardiopulmonary and arterial baroreceptors. All the subjects tolerated 30 min of LBNP at -15 mmHg, but during subsequent LBNP at -40 mmHg 11 subjects had vasodepressor reactions, with sudden hypotension, nausea, and dizziness. In these subjects, arterial plasma adrenaline responses to LBNP both at -15 and at -40 mmHg exceeded those in subjects who did not experience these reactions. In 16 of the 26 subjects, forearm noradrenaline spillover was measured; in the eight subjects with a vasodepressor reaction, mean forearm noradrenaline spillover failed to increase during LBNP at -15 mmHg (delta = -0.06 +/- (SEM) 0.04 pmol min-1 100mL-1), whereas in the eight subjects without a vasodepressor reaction, mean forearm noradrenaline spillover increased significantly (delta = 0.31 +/- 0.13 pmol min-1 100mL-1). Plasma levels of beta-endorphin during LBNP at -15 mmHg increased in some subjects who subsequently had a vasodepressor reaction during LBNP at -40mmHg. The findings suggest that a neuroendocrine pattern including adrenomedullary stimulation, skeletal sympathoinhibition, and release of endogenous opioids can precede vasodepressor syncope.

Dangling: a review of relevant physiology, research, and practice

Although dangling is a common nursing intervention, little research has been conducted to test its effectiveness or to compare various dangling methods. By contrast, abundant information is available about orthostatic responses. In this article the authors explain the physiologic principles underlying orthostatic responses, focusing on blood volume distribution and the role of the mechanoreceptors, discuss typical and atypical responses to dangling and standing, describe clinical manifestations of orthostatic hypotension and syncope, present research-based practice guidelines, and, provide specific recommendations for future research. Because of the wide variability in heart rate and blood pressure responses to orthostasis, the authors stress the importance of signs and symptoms such as nausea, pallor, dizziness, visual dimming, and impaired consciousness in assessing orthostatic tolerance. Studying rituals such as dangling can advance nursing practice, improve patient outcomes, and move nursing to a research-based practice.

The value of the clinical history in the differentiation of syncope due to ventricular tachycardia, atrioventricular block, and neurocardiogenic syncope

BACKGROUND

The present study was undertaken to identify and quantitate the symptoms associated with neurocardiogenic syncope, syncope due to ventricular tachycardia, and syncope resulting from atrioventricular block.

PATIENTS AND METHODS

Eighty patients referred for evaluation of syncope in whom a diagnosis of neurocardiogenic syncope, atrioventricular block, or ventricular tachycardia was established were studied. Each patient was interviewed using a standard questionnaire. The clinical histories were then compared to identify which variables best differentiated the cause of syncope.

RESULTS

The clinical histories of patients with syncope due to ventricular tachycardia and atrioventricular block were similar. Only age, the duration of prodromal symptoms, diaphoresis prior to syncope, and fatigue following syncope differed. In contrast, the clinical history in patients with neurocardiogenic syncope differed greatly from that obtained in patients with syncope due to atrioventricular block or ventricular tachycardia. Features of the clinical history that were predictive of syncope due to atrioventricular block or ventricular tachycardia were male sex, age > 54 years, < or = 2 episodes of syncope, and a duration of warning of < or = 5 seconds. Features of the clinical history predictive of syncope not due to ventricular tachycardia or atrioventricular block were palpitations, blurred vision, nausea, warmth, diaphoresis, or lightheadedness prior to syncope, and nausea, warmth, diaphoresis, or fatigue following syncope.

CONCLUSIONS

The results of this study identify and compare the features of the clinical history obtained in patients with syncope due to ventricular tachycardia, atrioventricular block, and neurocardiogenic syncope and demonstrate that the clinical history is of value in distinguishing patients with these three causes of syncope.

Pacing may not prevent neurocardiogenic syncope: the importance of correct diagnosis

A 28-year-old female with frequent attacks of syncope showed high degree atrioventricular (AV) block in Holter's electrocardiographic monitoring. A permanent pacemaker (VVIR) was implanted. However, the syncope recurred despite the normally-functioning pacemaker. The syncope associated with hypotension and bradycardia was reproduced by upright posture for 8 min. This neurocardiogenic syncope was prevented by propranolol (30 mg/day). Neurocardiogenic syncope should be ruled out before pacemaker implantation in patients with syncope, particularly in young adults with no apparent symptom/electrocardiography correlation.

Nitroglycerin infusion during upright tilt: a new test for the diagnosis of vasovagal syncope

The aim of our present study was to assess the value of nitroglycerin infusion during upright posture as a new provocative test for diagnosis of vasovagal syncope. To this purpose 40 patients with unexplained syncope (17 men and 23 women, mean age 47 years) and 25 asymptomatic control subjects with negative baseline head-up tilt underwent two other tilting tests, one during nitroglycerin infusion and one during isoproterenol infusion. The protocol of the nitroglycerin test consisted of a maximum of five successive stages of 5 minutes in the supine position plus 10 minutes 80-degree upright tilt at progressively increasing infusion rates (increments of 0.86 microgram/kg/hr every stage). During the nitroglycerin test a positive response (syncope in association with sudden hypotension and bradycardia) occurred in 21 (53%) patients with unexplained syncope, an exaggerated response (minor symptoms in association with slowly increasing hypotension alone) occurred in 10 (25%), a negative response in 9 (22%), and drug intolerance in 0. During the isoproterenol test these percentages were 25%, 25%, 32%, and 18%, respectively. Only 2 (8%) control subjects had a positive response to nitroglycerin test and 2 (8%) to isoproterenol test. Thus the nitroglycerin test seems to be a useful alternative tool for diagnosis of vasovagal syncope; it is equally specific but more sensitive and feasible than the isoproterenol test.

Evaluation of edrophonium as a provocative agent for vasovagal syncope during head-up tilt-table testing

Vasovagal syncope after head-up tilting is thought to be secondary to a complex, neurally-mediated reflex with both vasodepressor and cardioinhibitory efferent components. The efficacy of edrophonium, an acetylcholinesterase inhibitor, as a provocative agent for triggering syncope during head-up tilt testing was evaluated. Forty-five consecutive patients (22 female and 23 male) with history of recurrent unexplained syncope received edrophonium (10 mg intravenous) after 30 minutes of 60 degrees head-up tilting alone. Twenty normal control subjects (9 female and 11 male) were tested with head-up tilt testing and edrophonium. Syncope was induced in 19 of 45 patients with the diagnosis of unexplained syncope. In 9 patients who developed syncope with head-up tilting alone, the predominant hemodynamic finding was marked vasodepression. In contrast, in 10 patients who developed syncope only after head-up tilting and edrophonium, the predominant hemodynamic findings were marked vasodepression and bradycardia. Syncope was induced in 1 of 20 normal subjects after head-up tilting and edrophonium. There was no long-term complication from using edrophonium. It is concluded that head-up tilt testing with edrophonium: (1) significantly increases the identification of patients with vasovagal syncope, (2) may be particularly useful when provocation with isoproterenol is undesirable, and (3) may be an effective method to help differentiate patients with a significant reflex cardioinhibitory component from those with a predominantly reflex vasodepressor component.

Prognosis after syncope: impact of left ventricular function

A cardiac cause of syncope has been associated with increased sudden death risk, whereas unexplained syncope has a benign prognosis. However, in patients who have depressed left ventricular function, the accuracy of diagnostic tests and the efficacy of therapy, such as antiarrhythmic drugs, are reduced. Previous studies of patients with syncope have not evaluated the contribution of left ventricular performance in risk stratification for sudden death. The purpose of our study of a large population of patients with syncope was to determine the impact of left ventricular dysfunction on sudden death risk if syncope is caused by a cardiac cause or remains unexplained after electrophysiologic testing. We retrospectively evaluated the relationship of left ventricular ejection fraction to sudden death prognosis in 88 consecutive patients referred for electrophysiologic testing to determine a cause of syncope. The mean age was 57 +/- 18 years, left ventricular ejection fraction was 0.41 +/- 0.20, and 66 patients (75%) had structural heart disease. In 49 patients (56%) a cardiac cause of syncope was diagnosed, and in 39 patients (44%) the cause of syncope remained unexplained after evaluation. Cardiac syncope was attributed to ventricular tachycardia in 27 patients, bradyarrhythmia in 11 patients, and supraventricular tachyarrhythmia in 11 patients. By logistic regression only structural heart disease was independently associated with cardiac cause of syncope (p = 0.003). After a mean follow-up of 790 +/- 688 days, nine patients had died suddenly, eight (89%) of whom had left ventricular ejection fraction less than 0.30.(ABSTRACT TRUNCATED AT 250 WORDS)

Critical carotid and vertebral arterial occlusive disease and cough syncope

BACKGROUND AND PURPOSE

Cough syncope typically occurs in patients with known chronic lung disease. The mechanism usually involves a combination of decreased venous return, increased cerebrospinal fluid pressure, and secondary hypocapnia, all resulting in cerebral arterial vasoconstriction. Cough syncope has not in the past been associated with occlusive cerebrovascular disease.

CASE DESCRIPTION

We describe a 50-year-old man with a 6-month history of episodes of loss of consciousness during paroxysms of coughing. Physical examination showed asymmetrical upper extremity blood pressures and carotid and subclavian artery bruits. Pulmonary function studies were normal. Ultrasound and angiography showed total occlusion of the left common carotid artery, right internal carotid artery, and right vertebral artery; tight stenosis of the right subclavian artery; and a hypoplastic left vertebral artery. The patient had a left subclavian-to-left common carotid artery bypass and has had no syncope since that time.

CONCLUSIONS

To our knowledge, this is the first reported case of cough syncope and severe cerebrovascular disease in which surgery led to amelioration of symptoms. Cerebrovascular occlusive disease may contribute to cough syncope.