From the Guidelines
Syncope investigations should begin with a thorough history, physical examination, and 12-lead ECG for all patients, as recommended by the 2017 ACC/AHA/HRS guideline for the evaluation and management of patients with syncope 1. These initial assessments help determine the likely cause and guide further testing. For patients with suspected cardiac syncope, echocardiography is recommended to evaluate structural heart disease and ejection fraction, as stated in the 2017 ACC/AHA/HRS guideline 1. Ambulatory ECG monitoring (24-hour Holter, 7-30 day event monitors, or implantable loop recorders) should be used when arrhythmias are suspected, with the duration of monitoring determined by the frequency of symptoms. Some key points to consider in the investigation of syncope include:
- Tilt table testing is valuable for diagnosing vasovagal syncope, particularly in recurrent cases without clear cardiac cause, as noted in the 2004 European Heart Journal guidelines 1.
- Carotid sinus massage may identify carotid sinus hypersensitivity in older patients, as recommended in the 2004 European Heart Journal guidelines 1.
- Exercise stress testing should be performed when syncope occurs during or shortly after exertion, as stated in the 2004 European Heart Journal guidelines 1.
- Blood tests including complete blood count, electrolytes, glucose, and cardiac biomarkers can identify metabolic causes.
- For patients with neurological symptoms, brain imaging (CT or MRI) and EEG may be appropriate, but the 2021 ACR Appropriateness Criteria suggest that brain CT and MRI should be avoided in uncomplicated syncope 1. The investigation pathway should be individualized based on initial findings, with cardiac causes prioritized due to their higher mortality risk, as emphasized in the 2017 ACC/AHA/HRS guideline 1. Patients with high-risk features (older age, structural heart disease, abnormal ECG, or exertional syncope) warrant more urgent and comprehensive evaluation, as recommended in the 2017 ACC/AHA/HRS guideline 1.
From the Research
Investigations for Syncope
The investigations for syncope (fainting) include:
- A careful history and physical examination to differentiate syncope from other conditions that may cause a loss of consciousness or falling 2, 3, 4, 5
- Electrocardiography (ECG) as part of the initial evaluation to identify potential cardiac causes of syncope 2, 3, 4, 5, 6
- Additional testing based on the initial clinical evaluation, such as:
- Prolonged electrocardiographic monitoring, echocardiography, and exercise stress testing for patients with suspected cardiac syncope 2, 3, 4, 5
- Head-up tilt-table testing and carotid sinus massage for patients with suspected neurogenic reflex-mediated syncope 2
- Neuroimaging (e.g., head computed tomography, magnetic resonance imaging, carotid and transcranial ultrasonography) for patients with suspected cerebrovascular causes of syncope or focal neurologic signs or symptoms 2, 4
- Laboratory tests (e.g., hemoglobin measurement) based on history and physical examination findings 4
- Risk stratification tools, such as the Canadian Syncope Risk Score, to inform decisions regarding hospital admission 4
- Specific electrocardiographic presentations, such as bradycardia, atrioventricular block, intraventricular conduction abnormality, and tachydysrhythmia, can provide a reason for the loss of consciousness and guide early therapy and disposition 6