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 2021 ACR Appropriateness Criteria for syncope 1. The initial evaluation should include orthostatic vital signs, a 12-lead ECG, and basic laboratory tests (complete blood count, electrolytes, glucose, and renal function) to identify potential cardiac or non-cardiac causes of syncope.
- A detailed history and physical examination are crucial in identifying patients with high-risk features, such as age >60 years, male gender, known underlying congenital or acquired cardiac disease, palpitations or other cardiac-related symptoms prior to syncopal episode, syncope during exertion, syncope in supine position, low number of prior syncopal episodes, and family history of sudden cardiac death 1.
- 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 for the evaluation and management of patients with syncope 1.
- Brain imaging (CT or MRI) and electroencephalography are not recommended for routine evaluation of syncope, unless there are specific indications such as focal neurological deficits or trauma, as stated in the 2021 ACR Appropriateness Criteria for syncope 1.
- Tilt-table testing can be useful in diagnosing vasovagal syncope, while electrophysiology studies may be necessary for those with suspected arrhythmias, as recommended by the 2017 ACC/AHA/HRS guideline for the evaluation and management of patients with syncope 1.
- The workup should be tailored to the patient's risk factors, with more urgent and comprehensive evaluation for those with heart disease, abnormal ECG findings, syncope during exertion, or family history of sudden cardiac death, as these suggest potentially life-threatening causes 1.
From the Research
Initial Evaluation
The workup for syncope typically begins with a detailed history and thorough physical examination, including orthostatic vital signs and carotid sinus pressure 2, 3, 4, 5. This initial assessment may diagnose up to 50% of patients and allows for immediate short-term risk stratification 3.
Diagnostic Testing
Laboratory testing and neuroimaging have a low diagnostic yield and should be ordered only if clinically indicated 3. Several comparable clinical decision rules can be used to assess the short-term risk of death and the need for hospital admission 3.
Specialized Testing
In cases of unexplained syncope, provocative testing and prolonged electrocardiographic monitoring strategies can be diagnostic 3. Electrophysiologic studies can identify a potential cause in up to two thirds of patients with underlying structural heart disease 2. Head-up tilt testing has been useful in diagnosing neurally mediated syncope and guiding its therapy 2. Autonomic function testing is a safe way to evaluate patients with syncope further, and to assess their parasympathetic and sympathetic nervous systems 6.
Risk Stratification
Patients with presyncope have similar prognoses to those with syncope and should undergo a similar evaluation 3. Low-risk patients with a single episode of syncope can often be reassured with no further investigation 3. High-risk patients with cardiovascular or structural heart disease, history concerning for arrhythmia, abnormal electrocardiographic findings, or severe comorbidities should be admitted to the hospital for further evaluation 3.
Treatment
The treatment of neurally mediated and orthostatic hypotension syncope is largely supportive, although severe cases may require pharmacotherapy 3. Cardiac syncope may require cardiac device placement or ablation 3. Treatment based on electrophysiologic diagnoses is effective in preventing syncope recurrences but may also reduce cardiac mortality 2.