Syncope in adults: Risk assessment and additional diagnostic evaluation

INTRODUCTION — Syncope is a clinical syndrome in which transient loss of consciousness is caused by a period of inadequate cerebral nutrient flow, most often the result of an abrupt drop of systemic blood pressure. Typically, the inadequate cerebral nutrient flow is of relatively brief duration and, in syncope, is, by definition, spontaneously self-limited.

Loss of postural tone is inevitable with loss of consciousness, and consequently syncope is usually associated with collapse, which may trigger injury due to a fall (if the person is standing) or other type of accident (eg, if syncope occurs while driving or operating machinery). Recovery from true syncope is usually complete and rapid, with episodes rarely lasting more than a minute or two. Longer periods of real or apparent loss of consciousness suggest that the event is not syncope or not syncope alone (eg, syncope resulting in a head injury and concussion, thereby prolonging the event). Note, however, that patients and witnesses have difficulty estimating the duration of events; consequently, such estimates should be carefully considered only as one part of the comprehensive evaluation.

Issues relating to the evaluation of syncope in adults will be reviewed here. However, it must be kept in mind that not all "collapse" events are syncope. Consequently, the clinician must be able to exclude other conditions (eg, seizures, accidental falls, or metabolic disturbances) (algorithm 1) before focusing on the syncope evaluation strategies discussed here. The approach to the adult patient with syncope in the emergency department, as well as the pathogenesis, etiology, and management of syncope in adults are discussed elsewhere. (See "Approach to the adult patient with syncope in the emergency department" and "Syncope in adults: Epidemiology, pathogenesis, and etiologies" and "Reflex syncope in adults and adolescents: Clinical presentation and diagnostic evaluation" and "Syncope in adults: Management and prognosis".)

ASSESSMENT BASED ON THE INITIAL EVALUATION — The initial evaluation and, in particular, the history-taking of the patient with suspected transient loss of consciousness (TLOC) or syncope may result in one of several possible outcomes: a certain basis for symptoms, a suspected basis for symptoms, or an unknown or unexplained cause.

Certain diagnosis — Approximately 50 percent of the time, the initial evaluation by experienced clinicians leads to a relatively certain diagnosis of the cause of TLOC. Patients with a certain diagnosis generally do not require further diagnostic evaluation, although, on occasion, carefully chosen confirmatory testing may be warranted.

Examples of situations in which the clinician should feel comfortable that the diagnosis of the basis of syncope has been established based on initial evaluation include:

●Classic vasovagal syncope, in which precipitating events such as fear, severe pain, or emotional distress are associated with typical prodromal symptoms, especially if there are concomitant symptoms suggesting autonomic activation (eg, hot/cold sensation, nausea, sweating, etc).

●Situational syncope after urinating (postmicturition syncope), defecating (defecation syncope), coughing (cough syncope), or swallowing (deglutition syncope).

●Orthostatic (postural) syncope in which there is documentation by history of postural change leading to presumed orthostatic hypotension associated with syncope or presyncope. The presence of orthostatic blood pressure changes during office examination, with associated reproduction of symptoms, may help to confirm the diagnosis, but since a patient's drug and volume statuses may not be the same in the clinic as at the time of spontaneous symptoms, the absence of a diagnostic blood pressure drop during the medical examination does not exclude the diagnosis of orthostatic (postural) syncope. Further, measuring blood pressure by sphygmomanometer may be too slow to capture transient blood pressure falls. A beat-by-beat noninvasive recorder is preferred.

●Arrhythmia-related syncope when there is documented electrocardiographic (ECG) evidence of a significant tachyarrhythmia, bradyarrhythmia, or malfunctioning cardiac implantable electronic device.

Suspected diagnosis — In approximately 30 percent of cases, the initial evaluation will reveal clues from the history, the physical exam, or the ECG that result in a possible diagnosis for the cause of TLOC/syncope. These patients then have a suspected but as yet uncertain (or unconfirmed) cause of TLOC. Nevertheless, the suspected diagnosis may be valuable in focusing the subsequent evaluation strategy. (See 'Selected additional testing' below.)

For patients with a suspected but as yet uncertain diagnosis for the cause of syncope after the initial evaluation, specific confirmatory testing is warranted in order to solidify or, conversely, to exclude the suspected diagnosis. Such testing may also aid in the planning of treatment. Tilt-table testing is an example of a "confirmatory" test, albeit with suboptimal sensitivity and specificity, that is often used when the diagnosis of a reflex vasovagal syncope is suspected but the presentation is not classical. In this regard, only about 40 percent of the presumed vasovagal syncopes are "classic" in presentation, and this percentage may be even lower in older adult patients. Other autonomic studies may help identify orthostatic hypotension due to neurologic conditions, and these can be incorporated with tilt-table testing. (See "Upright tilt table testing in the evaluation of syncope".)

Unexplained diagnosis — When the initial evaluation, including history, physical examination, and ECG, is completely nondiagnostic in a patient with TLOC and suspected syncope, the patient is considered to have an unexplained diagnosis; this occurs in approximately 20 percent of cases. In such patients, the strategy for subsequent assessment varies according to the severity and frequency of the episodes and the presence or absence of heart disease.

The presence of heart disease has been shown to be an independent predictor of cardiac cause of syncope, with a sensitivity of 95 percent and a specificity of 45 percent; by contrast, in the absence of structural heart disease or abnormal ECG, the likelihood of cardiac syncope is very low (3 percent).

●No evidence of structural heart disease – In the absence of demonstrable structural heart disease or channelopathies (eg, long QT syndrome, Brugada syndrome), the causes of syncope are usually reflex in nature, and most often vasovagal [1].

The majority of patients with single or rare episodes of syncope and an unexplained diagnosis probably have reflex syncope (most often vasovagal syncope). For patients with rare or solitary events, apart from advice regarding how to recognize episodes (in order to reduce the likelihood of falls/injury) and how to avoid/prevent "triggers," more aggressive treatment measures are generally not needed.

•For patients with multiple recurrences of syncope and an unexplained diagnosis in the absence of structural heart disease, and who have a normal ECG, reflex syncope remains the most probable diagnosis. At this stage, if the etiology is in doubt, tilt-table testing and carotid sinus massage (CSM) may be helpful.

-Tilt-table testing is principally directed at unmasking susceptibility to the vasovagal syncope; its value for assessing susceptibility to other types of reflex syncope (ie, situational syncope) is less well established.

-CSM is exclusively directed to assessing the possibility of carotid sinus hypersensitivity (CSH) and carotid sinus syndrome (CSS) [2]. Carotid sinus syndrome is usually a condition of older (ie, >60 years, mainly male) persons unless the patient has had prior neck surgery or irradiation. Diagnosis is best established if CSM results in reproduction of syncope symptoms.

-Other autonomic tests may suggest or unmask underlying autonomic disturbances such as those that accompany neurologic disorders (eg, Parkinsonism, pure autonomic failure, or multiple system atrophy). For patients with signs of autonomic failure or neurologic disease, a specific neurologic diagnosis should be sought by involving the appropriate neurologic consultant.

•Psychiatric assessment may be helpful for patients with frequent recurrences of apparent TLOC, especially if the episodes are reported to be very long in duration (often >5 minutes) and occur many times per day or week. The diagnosis in such cases is most likely "pseudosyncope/pseudoseizures." This diagnosis is further supported if the patient also has multiple other somatic complaints. A past history of physical and/or sexual abuse has been reported to be present in approximately 25 percent of these patients, although it is not clear that the frequency of such history is much greater than that in the population as a whole. Tilt-table testing with video electroencephalogram monitoring can be very useful in confirming pseudosyncope/pseudoseizures [2,3]. Insertable loop recorders may also be helpful to exclude an arrhythmic cause.

●Known structural heart disease or an abnormal ECG – Patients with known structural heart disease have a significantly greater likelihood of cardiac syncope than is the case in individuals with normal hearts [1,2,4]. In such patients, or in those who have an abnormal ECG suggestive of underlying structural heart disease, transthoracic echocardiography is important.

Stress testing may be warranted if ischemic heart disease is suspected and/or the syncope occurred during exertion (ie, in "full flight") as opposed to after termination of exertion.

In many instances, prolonged ambulatory ECG monitoring will be needed. The choice of ambulatory ECG monitoring system is largely dependent on the frequency with which events occur. In the case of very rare events, an insertable cardiac monitor (ICM; also referred to as an implantable loop recorder) may be helpful to monitor the ECG for months to years. In any event, the choice should be on a case-by-case basis, using history and clinical experience as guides [5]. (See 'Ambulatory ECG monitoring' below and "Ambulatory ECG monitoring".)

Risk stratification — Wherever the initial syncope evaluation leads, clinicians must determine whether the affected individual needs in-hospital care for further evaluation and/or initiation of treatment. The primary factor determining whether the patient with presumed syncope should be hospitalized is the individual's immediate mortality risk (table 1), with secondary issues including the potential for physical injury (eg, fall risk) and, to a lesser extent, the issue of whether certain treatments require hospital monitoring for safe initiation. Patients can be classified as high risk (requiring admission), intermediate risk (admission is case-by-case dependent), and low risk (patient can be evaluated as an outpatient). In all cases, arrangements for prompt outpatient care are essential. The development of "syncope/collapse" clinics has been shown to be helpful in this regard.

The American College of Emergency Physicians, American College of Physicians, European Society of Cardiology, American College of Cardiology, and American Heart Association have established guidelines and algorithms for management and disposition [1,2,6-8]. The policy statements are based primarily on the risk stratification data presented above and suggest admission for patients with evidence of acute decompensated (ie, congestive) heart failure or structural heart disease and patients at high risk for adverse outcomes (table 2) [6].

High-risk patients — Several prognostic markers identify patients with syncope who should be hospitalized for evaluation and treatment (table 3).

●Syncope associated with symptoms suggestive of acute myocardial ischemia, acute aortic dissection, decompensated heart failure, and/or suspicion of hemodynamically concerning underlying structural heart disease (eg, aortic or mitral stenosis, severe pulmonary hypertension, or hypertrophic cardiomyopathy) have the highest immediate mortality and recurrence risks.

●Also at high risk are patients with syncope and certain ECG abnormalities, including high-grade atrioventricular (AV) block, cardiac rhythm pauses of five seconds or greater, preexcitation syndromes (eg, Wolff-Parkinson-White Syndrome), suspected cardiomyopathy, or evidence suggestive of a primary arrhythmia syndrome (eg, long QT syndrome, Brugada syndrome, catecholaminergic paroxysmal ventricular tachycardia, short QT syndrome, etc).

●Patients with syncope during exercise (ie, in "full flight," not afterward while "cooling" down), while lying down ("supine" syncope), without any warning, and those with syncope causing motor vehicle accidents or severe injury should generally be considered for in-hospital evaluation.

Risk stratification of patients with syncope presenting to the emergency department using prediction tools is discussed separately. (See "Approach to the adult patient with syncope in the emergency department", section on 'Risk stratification'.)

Intermediate-risk patients — Patients considered to be at intermediate risk of mortality or recurrent syncope resulting in injury are primarily those with a history of structural heart disease or channelopathy but who have no signs of active or unstable cardiac disease, no major ECG abnormalities, no family history of sudden death, and no evidence of a malfunctioning cardiac device. Often, patients have symptoms that are not consistent with classic vasovagal or reflex-mediated syncope, thereby raising cardiac syncope as a possible etiology. Decisions regarding the need for hospitalization, further evaluation, and treatment are often made in such patients on a case-by-case basis.

Low-risk patients — Patients considered to be at low risk of mortality or recurrent syncope resulting in injury typically have no evidence of structural heart disease and have a normal baseline ECG. In most cases, the syncope is thought to be reflex or orthostatic syncope, both of which are generally considered relatively benign with regard to the risk of early mortality or recurrent syncope resulting in injury, but not necessarily with regard to falls and injury. Most of the time, these patients can be treated and discharged home for further outpatient evaluation as needed, along with plans for prompt outpatient follow-up. However, such patients should be alerted to the risk of falls so that they can take precautions to remain safe as the outpatient evaluation is conducted.

SELECTED ADDITIONAL TESTING — If additional diagnostic testing is deemed necessary following the initial evaluation, the choice of testing should be individualized and based on the results of initial assessment, rather than taking a standardized approach to testing in all patients [2,8]. By using this approach, low-yield testing can be avoided in many patients, thereby reducing the likelihood of false-positive testing and enhancing the cost effectiveness of the evaluation.

A number of diagnostic tests are potentially useful, but each test should be chosen selectively to address a suspected diagnosis or diagnoses. Since syncope is by definition a cardiovascular issue, the meaningful tests are mostly cardiovascular in nature. Neurologic testing is generally of low yield and historically has been overused unless the history or physical examination suggest a specific nonsyncope neurologic issue such as a seizure [9]. On the other hand, neurologic consultation is often necessary in idiopathic orthostatic hypotension in which an underlying neurologic disease such as Parkinson disease or pure autonomic failure may be discovered. (See "Mechanisms, causes, and evaluation of orthostatic hypotension", section on 'Baroreflex dysfunction'.)

Ambulatory ECG monitoring — Ambulatory ECG monitoring is warranted when there is suspicion that a cardiac arrhythmia may be the cause of syncope. However, the choice of monitor system depends on the expected frequency of symptom events [2,5,8]. Thus, unless symptoms are occurring daily, a 24- or 48-hour Holter monitor is not likely to be useful in making a diagnosis. Even in-hospital monitoring for one to three days may be nonproductive. In cases of significant but infrequent symptoms, longer-term ambulatory monitoring systems are more likely to be helpful [10]. (See "Ambulatory ECG monitoring".)

The following types of ambulatory ECG monitoring are available and provide variable amounts and types of information:

●Continuous ambulatory ECG (Holter) monitoring and patch monitoring – Continuous ambulatory ECG (Holter) monitoring includes a continuous recording of all ECG data for a period of 24 or 48 hours. Continuous ambulatory ECG (Holter) monitoring devices have patient-activated event markers and encoded time markers, and may be helpful in patients with daily or near daily symptoms. However, syncope patients rarely have symptoms of such frequency. Consequently, Holter monitor recording has almost no value in this setting.

In contemporary practice, continuous ECG recording with a patch monitor (all-in-one small adhesive device that does not require separate leads, wires, or battery packs) is capable of continuously recording an ECG for up to 14 days, although only a single lead is recorded, and symptom correlation documentation (an important and highly desirable feature) is poor.

●Event monitoring and mobile cardiac outpatient telemetry (MCOT) monitoring – Event monitors (insertable cardiac monitors [ICM]/loop recorders, postevent monitoring devices that are placed when symptoms arise, or autotriggered event recorders) are most commonly used for patients with less frequent (ie, weekly to monthly) symptoms of palpitations, presyncope, or syncope. Typically utilized for two to four weeks (although possibly up to three months), event monitors are small, lightweight devices with electrodes applied either continuously or when the device is positioned when symptoms arise. These devices have limited utility in the syncope evaluation unless the device is continuously worn.

In contemporary practice, MCOT may be preferable to wearable event (loop) monitoring. MCOT allows the patient or witness to activate the device when symptoms arise, but the device will also activate and automatically record when an arrhythmia is detected. MCOT device technology is not universally available. MCOT is expensive but may be cost effective in terms of superior symptom-rhythm correlation. Additionally, with MCOT, the ECG findings can be sent to the clinician promptly via internet access.

●Insertable cardiac monitors (ICM) – The ICM is a subcutaneous monitoring device (picture 1) for the detection of cardiac arrhythmias (these were previously termed insertable loop recorders). ICMs are most commonly utilized in the evaluation of palpitations or syncope of undetermined etiology, particularly when symptoms are infrequent (eg, less than once per month) and/or other ambulatory monitoring has been unrevealing or inconclusive [2]. The ICM, which stores recorded ECG data that can be retrieved by interrogating the device (including remote downloads from the patient's home), offers the ability to monitor for cardiac arrhythmias for prolonged periods of months to years [11].

ICMs have the best yield (up to a 75 percent detection rate for the cause of syncope at three years), as they may be used to monitor heart rhythm in patients for up to several years, do not need to be removed during certain activities such as showering or swimming, and may identify significant cardiac rhythm abnormalities when the patient is sleeping.

As examples of the safety and efficacy of ICMs for evaluating patients with syncope:

•In a randomized trial of 246 patients (mean age 70 years) with unexplained syncope who were randomly assigned to conventional management, evaluation in a dedicated syncope clinic, ICM placement, or combined evaluation in a syncope clinic with ICM placement, both evaluation in a dedicated syncope clinic and ICM placement resulted in significantly earlier diagnosis [12].

•In a small randomized trial, 60 patients (mean age 66 years) were assigned to "conventional" testing with an external loop recorder and tilt and electrophysiologic testing, or to prolonged monitoring with an ICM with one year of monitoring [13]. A diagnosis (most commonly bradycardia) was established more often with prolonged monitoring (55 versus 19 percent with conventional testing).

•In a series of 392 patients with recurrent syncope, among whom 106 patients had a recurrent syncopal episode recorded on the ICM, 53 patients had therapy guided by this information (including pacemaker placement in more than 80 percent), while the remaining patients had no specific therapy, primarily because an arrhythmic cause was not identified [14].

•Among a cohort of 41 patients with recurrent syncope and structural heart disease but negative findings during invasive electrophysiology studies, 33 patients received an ICM and were followed for an average of 15 months. During follow-up, 22 of 33 patients had recurrent syncope with evidence documenting reflex-mediated syncope, while only one patient had a documented need for permanent pacing [1].

Exercise testing — Exercise testing generally has a low diagnostic yield in patients with syncope unless the symptoms occurred during maximum exercise. In patients with symptoms during exercise who undergo exercise testing, the following observations may be helpful:

●Syncope is reproduced during or immediately after exercise in the presence of ECG abnormalities or severe hypotension.

●Mobitz type II second- or third-degree AV block develop during exercise even without syncope. This response suggests block distal to the AV node and is predictive of progression to permanent AV block.

Exercise testing may also be helpful in other settings. Failure to shorten the QT interval with exercise may be a sign of congenital long QT syndrome even when this abnormality is not apparent in the resting ECG [15]. Exercise-induced ventricular ectopy can also be seen in patients with catecholaminergic polymorphic ventricular tachycardia. (See "Congenital long QT syndrome: Diagnosis" and "Catecholaminergic polymorphic ventricular tachycardia".)

Carotid sinus massage (CSM) — Carotid sinus syndrome (CSS) is an infrequent cause of collapse in older patients (generally males >60 years of age) and/or individuals who have had prior head/neck surgery or irradiation. Careful massage of the neck at the angle of the mandible by an experienced clinician (both sides at separate times) may unmask carotid sinus hypersensitivity. CSS is diagnosed if carotid sinus hypersensitivity is present (usually a sinus pause >3 to 5 seconds and/or a blood pressure fall of >50 mmHg) with reproduction of symptoms (which usually requires the patient to be seated upright when tested) [2,8]. Although there is little evidence of risk, most guidelines indicate that practitioners should avoid CSM in patients with history of transient ischemic attack or stroke within the past three months and in patients with carotid bruits (except if carotid Doppler studies have previously excluded significant carotid stenosis). However, this procedure can be performed safely and with useful diagnostic effect by experienced clinicians. (See "Carotid sinus hypersensitivity and carotid sinus syndrome".)

Autonomic testing — The utility of tilt-testing is controversial, and many centers do not rely on such testing. However, when interpreted by an experienced clinician, such testing remains useful [15]. In addition, clinical experience suggests that tilt-testing when used in conjunction with ambulatory recording of spontaneous syncope can help to determine if a cardiac pacemaker may be helpful in certain individuals. Tilt-testing may also be incorporated into a more comprehensive series of autonomic tests (eg, active standing, Valsalva maneuver, sinus arrhythmia, etc). The more complete test capability permits evaluation of a range of possible diseases of the autonomic nervous system that may contribute to increased syncope susceptibility.

While classic vasovagal syncope can often be identified by a carefully taken medical history alone, many cases are not classic; this is particularly the case in older individuals. Additionally, a positive tilt-test helps the patient to know that the physician has seen the problem, thereby increasing the patient's confidence in the diagnosis. This is helpful for future treatment success.

Further, many centers undertake other autonomic testing maneuvers in conjunction with the tilt-table test. In such cases, they assess the patient's overall autonomic status and thereby provide a much more comprehensive assessment of possible causes of syncope. (See "Upright tilt table testing in the evaluation of syncope".)

Neurologic imaging or electroencephalogram (EEG) are rarely useful in evaluating syncope. However, transient loss of consciousness (TLOC) includes several conditions that may warrant neurologic testing. Head trauma and epilepsy are the most important examples, as they may be associated with true loss of consciousness, whereas other neurologic conditions (eg, transient ischemic attacks) are not. In true syncope (which is a cardiovascular disorder), neurologic diagnostic tests are not needed in the absence of concern related to syncope-induced head injury. Syncope is not a primary neurologic condition in the vast majority of cases, and tests such as head imaging or EEG are not likely to provide a diagnosis and as a consequence are not cost effective. Neurologic consultation is warranted if autonomic failure (eg, primary autonomic failure or Parkinson disease) is deemed a possible underlying cause. EEG testing as part of the autonomic testing laboratory is becoming increasingly more common [16].

Electrophysiology study — Electrophysiology study is rarely indicated but may be useful in selected patients with unexplained TLOC/syncope in whom the presence of structural heart disease increases the likelihood that a cardiac arrhythmia leads to syncope [2,8,17-21]. However, some patients with structural heart disease may already have an indication for a pacemaker or an implantable cardioverter-defibrillator, and therefore electrophysiology study may not be needed. (See "Primary prevention of sudden cardiac death in patients with cardiomyopathy and heart failure with reduced LVEF" and "Ventricular arrhythmias: Overview in patients with heart failure and cardiomyopathy", section on 'Clinical manifestations'.)

Neurologic testing — Neurologic testing (eg, EEG alone, head computed tomography [CT], or head magnetic resonance imaging [MRI]) as a solitary evaluation is rarely warranted in patients with true syncope. However, neurologic consultation may be helpful to identify certain disorders (eg, Parkinson disease or pure autonomic failure) that may predispose to orthostatic syncope or syncope during exertion. Other neurologic disorders (eg, seizures) can cause TLOC that may be confused with syncope (table 4).

As a rule, neurologic tests (eg, EEG, brain CT scan, brain MRI, and carotid Doppler ultrasound) are ordered more frequently than is appropriate. In one review of 649 patients, 53 percent had at least one neurologic test [9]. Such testing is rarely useful.

The 2018 European Society of Cardiology guidelines recommend neurologic referral in patients in whom TLOC is suspected to be epilepsy rather than syncope [2]. In addition, neurologic referral to evaluate the underlying disease is indicated when syncope is due to autonomic failure.

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Syncope".)

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5^th to 6^th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10^th to 12^th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

●Basics topic (see "Patient education: Syncope (fainting) (The Basics)")

●Beyond the Basics topic (see "Patient education: Syncope (fainting) (Beyond the Basics)")

SUMMARY AND RECOMMENDATIONS

●Definition – Syncope is a transient loss of consciousness (TLOC) due to inadequate cerebral nutrient flow. In the vast majority of cases, the underlying cause is a temporary but self-limited drop in systemic blood pressure. Other causes of loss of consciousness such as head trauma, seizures, intoxications, or metabolic disorders should also be considered. Distinguishing syncope from these other conditions can only be accomplished with careful diagnostic assessment (algorithm 1). (See 'Introduction' above and "Syncope in adults: Clinical manifestations and initial diagnostic evaluation".)

●Outcomes of the initial evaluation – The initial evaluation of the patient with suspected TLOC or syncope may result in one of several possible outcomes: a certain basis for symptoms (approximately 50 percent), a suspected basis for symptoms (approximately 30 percent), or an unknown or unexplained cause (approximately 20 percent). (See 'Assessment based on the initial evaluation' above.)

●Risk stratification – Wherever the initial syncope evaluation leads, clinicians must determine whether the affected individual needs in-hospital care for further evaluation and/or initiation of treatment. The primary factor determining whether the patient with presumed syncope should be hospitalized is the individual's immediate mortality risk, with secondary issues including the potential for physical injury (eg, fall risk) and, to a lesser extent, the issue of whether certain treatments require hospital monitoring for safe initiation. Patients can be classified as high risk (requiring admission), intermediate risk (admission is case-by-case dependent), and low risk (patient can be evaluated as an outpatient). (See 'Risk stratification' above.)

●Role of additional testing – If additional diagnostic testing is deemed necessary following the initial evaluation, the choice of testing should be individualized and based on the results of initial assessment rather than taking a standardized approach to testing in all patients. In any event, test results must be carefully interpreted in the context of the clinical history and presentation; this requires some experience. By using this approach, low-yield testing and inappropriate conclusions can be avoided, thereby reducing the likelihood of false-positive testing and enhancing the cost-effectiveness of the evaluation. (See 'Selected additional testing' above.)

●Use of ambulatory ECG monitoring – Ambulatory ECG monitoring can be very valuable in an effort to establish or exclude an arrhythmic cause of syncope. The choice among various ambulatory ECG monitoring technologies (eg, Holter-type, patch monitors, event monitors, mobile continuous outpatient telemetry, and insertable loop recorders) must be based on the suspected monitoring duration that will be required to capture a spontaneous symptom event. A device that can activate on its own in the setting of an arrhythmia and/or has a loop memory to retain information for later download is preferred. (See 'Ambulatory ECG monitoring' above.)