From the Guidelines
The workup for syncope should begin with a thorough history and physical examination, focusing on the circumstances surrounding the event, prodromal symptoms, and any associated features, as recommended by the 2017 ACC/AHA/HRS guideline for the evaluation and management of patients with syncope 1.
Initial Evaluation
The initial evaluation should include orthostatic vital signs, electrocardiogram (ECG), and basic laboratory tests including complete blood count, basic metabolic panel, and cardiac enzymes.
- A thorough history should focus on the circumstances surrounding the event, including position, activity, and any predisposing factors or precipitating events, as outlined in the 2009 European Heart Journal guidelines for the diagnosis and management of syncope 1.
- The physical examination should assess for signs of heart disease, neurological abnormalities, and other potential causes of syncope.
Further Testing
If cardiac causes are suspected, an echocardiogram should be performed to assess structural heart disease and ejection fraction.
- For patients with recurrent unexplained syncope or suspected cardiac arrhythmias, ambulatory cardiac monitoring is recommended, ranging from 24-48 hour Holter monitors for frequent episodes to implantable loop recorders for infrequent events, as suggested by the 2004 European Heart Journal guidelines on management of syncope 1.
- Tilt-table testing may be useful for suspected vasovagal syncope, while exercise stress testing is appropriate when exertional syncope is reported.
- Carotid sinus massage can be considered in older patients without carotid disease.
Risk Stratification
The diagnostic approach should be guided by risk stratification, with high-risk features including older age, structural heart disease, abnormal ECG, family history of sudden cardiac death, or syncope during exertion warranting more urgent and comprehensive evaluation, as recommended by the 2017 ACC/AHA/HRS guideline 1.
Neuroimaging and EEG
Neuroimaging (CT or MRI) is generally not recommended unless focal neurological findings are present, as true neurological syncope is rare.
- Electroencephalogram (EEG) should be reserved for cases where seizures are suspected. The most recent and highest quality study, the 2017 ACC/AHA/HRS guideline 1, provides the basis for these recommendations, prioritizing morbidity, mortality, and quality of life as the outcome.
From the Research
Work-up for Syncope
The work-up for syncope involves a thorough clinical assessment to identify the underlying cause and quantify the risk to the patient 2. The goals of the clinical assessment are:
- To identify the precise cause of syncope in order to implement a mechanism-specific and effective therapeutic strategy
- To quantify the risk to the patient, which depends on the underlying disease rather than the mechanism of syncope
Initial Evaluation
The initial evaluation of a patient with syncope should include:
- A thorough clinical history, which is the best diagnostic tool 3
- Physical examination, including orthostatic blood pressure measurements 4
- 12-lead electrocardiogram (ECG), which is the only instrumental test recommended for the initial evaluation of patients with suspected syncope 5
Classification of Syncope
Syncope can be classified into three main categories:
- Cardiac syncope, which may be structural (mechanical) or electrical 2
- Reflex (neurally mediated) syncope, which can be further categorized into:
- Vasovagal syncope (from emotional or orthostatic stress)
- Situational syncope (due to specific situational stressors)
- Carotid sinus syncope (from pressure on the carotid sinus)
- Atypical reflex syncope (episodes of syncope or reflex syncope that cannot be attributed to a specific trigger or syncope with an atypical presentation) 2
- Orthostatic syncope, which is caused by an abnormal drop in systolic blood pressure upon standing 2
Further Testing
Further testing may be considered if the initial evaluation is inconclusive and indicates possible adverse outcomes 4. This may include:
- Prolonged electrocardiographic monitoring
- Stress testing
- Echocardiography
- Neuroimaging (only if findings suggest a neurologic event or a head injury is suspected)
- Laboratory tests (based on history and physical examination findings)
Risk Stratification
Patients with syncope can be designated as having lower or higher risk of adverse outcomes according to history, physical examination, and electrocardiographic results 4. Risk stratification tools, such as the Canadian Syncope Risk Score, may be beneficial in this decision. Some tools include cardiac biomarkers as a component.