From the Guidelines
The diagnostic workup for syncope and collapse 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. The initial evaluation should include orthostatic vital signs, electrocardiogram (ECG), and basic laboratory tests including complete blood count, basic metabolic panel, and cardiac enzymes. For patients with suspected cardiac syncope, additional tests may include echocardiography, ambulatory cardiac monitoring (Holter monitor for 24-48 hours or event recorder for 2-4 weeks), and exercise stress testing, as suggested by the 2017 ACC/AHA/HRS guideline 1. If neurological causes are suspected, brain imaging (CT or MRI) and electroencephalogram (EEG) may be appropriate, but should be guided by specific clinical findings and not solely by the presence of syncope, as emphasized by the ACR Appropriateness Criteria for syncope 1. For recurrent unexplained syncope, tilt-table testing can help diagnose vasovagal syncope, while implantable loop recorders may be used for long-term monitoring (up to 3 years) in patients with infrequent episodes, as recommended by the 2017 ACC/AHA/HRS guideline 1. Carotid sinus massage may be performed in older patients to detect carotid sinus hypersensitivity, but should be avoided in those with carotid bruits or history of stroke, as cautioned by the 2017 ACC/AHA/HRS guideline 1. The diagnostic approach should be guided by the initial risk stratification, with high-risk features including age >60, history of cardiac disease, abnormal ECG, syncope during exertion or while supine, absence of prodrome, or associated injury requiring prompt and more extensive evaluation, often in an inpatient setting, as highlighted by the ACR Appropriateness Criteria for syncope 1.
Key considerations in the diagnostic workup include:
- A thorough history and physical examination to identify potential causes of syncope
- Initial testing with orthostatic vital signs, ECG, and basic laboratory tests
- Additional testing guided by clinical findings and risk stratification
- Avoidance of unnecessary testing, particularly brain imaging, in patients with uncomplicated syncope
- Consideration of cardiac and neurological causes, and guidance by relevant clinical guidelines and appropriateness criteria.
From the Research
Diagnostic Workup for Syncope
The diagnostic workup for syncope, or loss of consciousness, typically involves a combination of clinical evaluation, laboratory tests, and imaging studies. The goal of the workup is to determine the underlying cause of the syncope and to identify any potential life-threatening conditions.
Initial Evaluation
- A thorough clinical history and physical examination are essential in the initial evaluation of syncope 2
- A 12-lead electrocardiogram (ECG) is also recommended as part of the initial evaluation 2
- Supine and standing blood pressure measurements, as well as laboratory tests such as cardiac biomarkers, may be ordered based on the patient's clinical presentation 3
Risk Stratification
- The European Society of Cardiology guidelines recommend risk stratification of syncope patients into high-, intermediate-, and low-risk groups based on clinical features and initial evaluation results 3
- High-risk patients should be hospitalized and undergo further evaluation, while low-risk patients may be discharged with education on the benign nature of their condition 3
Imaging Studies
- Cardiac imaging tests, such as transthoracic echocardiography, may be ordered if the clinical evaluation suggests a cardiac cause of syncope 4
- Advanced imaging techniques, such as multidetector computed tomography and cardiac magnetic resonance imaging, may be reserved for selected cases where echocardiography is inconclusive 4
Laboratory Studies
- Laboratory studies, such as cardiac enzymes and electrocardiogram, may be ordered as part of the diagnostic workup, but the yield of these tests may be low in patients with suspected syncope 5
- The diagnostic workup should be tailored to the individual patient based on their clinical presentation, rather than following a standardized protocol for all patients with suspected syncope 5
Differential Diagnosis
- Syncope can be mimicked by other conditions, such as seizures, stroke, metabolic disorders, and head trauma, which must be considered in the differential diagnosis 6
- A thorough history and physical examination can help guide further diagnostic evaluation and management of patients with suspected syncope 6