From the Guidelines
The workup for syncope should begin with a thorough history and physical examination, focusing on the circumstances surrounding the event, followed by an electrocardiogram (ECG) to evaluate for cardiac causes. This approach is supported by the most recent guidelines, including the 2017 ACC/AHA/HRS guideline for the evaluation and management of patients with syncope 1. The history should include questions about the circumstances surrounding the event, such as position, activity, and predisposing factors, as well as questions about the onset of the attack, including symptoms such as nausea, vomiting, and palpitations 2.
Additional testing may include:
- Orthostatic vital signs to evaluate for orthostatic hypotension
- Echocardiogram to evaluate for structural heart disease
- Holter or event monitoring to evaluate for arrhythmias
- Tilt-table testing to evaluate for neurally mediated syncope
- Blood work, including complete blood count, electrolytes, and glucose, to evaluate for metabolic causes
The causes of syncope can be categorized into three main groups:
- Cardiac (structural heart disease, arrhythmias)
- Neurally mediated (vasovagal, situational, carotid sinus hypersensitivity)
- Orthostatic hypotension (medication-induced, volume depletion, autonomic dysfunction)
Cardiac causes are generally the most concerning and carry the highest mortality risk. Vasovagal syncope, triggered by emotional stress or prolonged standing, is the most common cause overall. Management depends on the underlying cause and may include cardiac interventions (pacemaker, ICD, ablation), medication adjustments, volume repletion, compression stockings, or behavioral modifications. Patients with unexplained syncope, especially those with heart disease or abnormal ECG, should be hospitalized for further evaluation due to increased risk of adverse outcomes. The 2017 ACC/AHA/HRS guideline provides a comprehensive approach to the evaluation and management of syncope, and its recommendations should be followed to ensure optimal patient outcomes 1.
From the Research
Work-up of Syncope
The work-up of syncope involves a thorough clinical history, physical examination, and electrocardiogram (ECG) as the initial steps 3, 4, 5, 6, 7.
- A detailed history is crucial in identifying the cause of syncope, with the classification of syncope based on the underlying pathophysiological mechanism, including cardiac, orthostatic, and reflex (neurally mediated) mechanisms 3.
- Physical examination, including orthostatic blood pressure measurements, is also essential in the evaluation of syncope 4, 5, 6.
- Electrocardiography is a mandatory diagnostic tool, which, although normal in the majority of patients with syncope, has the potential to identify patients with high likelihood of cardiac syncope due to arrhythmic or cardiopulmonary disorder 7.
Causes of Syncope
The causes of syncope can be categorized into:
- Cardiac causes, which may be structural (mechanical) or electrical, and are associated with increased morbidity and mortality 3, 4, 5.
- Orthostatic hypotension, caused by an abnormal drop in systolic blood pressure upon standing, which can be due to autonomic nervous system failure or hypovolaemia 3.
- Reflex (neurally mediated) syncope, which can be further categorized into vasovagal syncope, situational syncope, carotid sinus syncope, and atypical reflex syncope 3.
- Neurally mediated syncope, which is the most common type and has a benign course 5.
Risk Stratification
Risk stratification is essential in the management of syncope, with patients designated as having lower or higher risk of adverse outcomes according to history, physical examination, and electrocardiographic results 4, 5.
- Risk stratification tools, such as the Canadian Syncope Risk Score, may be beneficial in informing decisions regarding hospital admission 4.
- Patients with life-threatening causes of syncope should be managed urgently and appropriately, while those with reflex or orthostatic syncope should have any exacerbating medication addressed and be provided with general measures to increase blood pressure 3.