What is the appropriate workup for a patient experiencing presyncope (near syncope)?

From the Guidelines

The workup for presyncope should begin with a thorough history and physical examination, focusing on cardiovascular and neurological systems, as recommended by the American College of Radiology Appropriateness Criteria 1. Initial testing should include orthostatic vital signs, electrocardiogram (ECG), and basic laboratory tests including complete blood count, basic metabolic panel, and cardiac enzymes. If the history suggests cardiac causes, an echocardiogram, Holter monitor or event recorder for 24-48 hours, and exercise stress testing may be appropriate, as suggested by the American Heart Association and American Red Cross guidelines for first aid 1. For recurrent unexplained episodes, extended cardiac monitoring with implantable loop recorders can be considered. Tilt-table testing is useful when vasovagal syncope is suspected, and neurological evaluation including electroencephalogram (EEG) and brain imaging may be necessary if seizures are suspected, as recommended by the American College of Radiology Appropriateness Criteria 1. Carotid sinus massage can help diagnose carotid sinus hypersensitivity in older patients. Additional specialized tests like electrophysiology studies may be needed for suspected arrhythmias. This comprehensive approach is important because presyncope can result from various causes including cardiac arrhythmias, structural heart disease, orthostatic hypotension, vasovagal reactions, or neurological conditions, and early identification of the underlying cause is crucial as some conditions, particularly cardiac causes, may be life-threatening if left untreated, as highlighted by the 2024 American Heart Association and American Red Cross guidelines for first aid 1.

Some key points to consider in the workup for presyncope include:

• Maintaining or assuming a safe position, such as assisted sitting or lying down, to prevent injury 1
• Using physical counterpressure maneuvers (PCMs) to avoid syncope, with lower-body PCMs being preferable to upper-body and abdominal PCMs 1
• Avoiding the use of PCMs when symptoms of a heart attack or stroke accompany presyncope 1
• Considering the use of echocardiography, Holter monitoring, and exercise stress testing in patients with suspected cardiac causes of presyncope, as recommended by the American College of Radiology Appropriateness Criteria 1

From the Research

Presyncope Workup

• The workup for presyncope involves a detailed history, physical examination, and electrocardiography 2, 3
• The initial evaluation may diagnose up to 50% of patients and allows immediate short-term risk stratification 2
• Laboratory testing and neuroimaging have a low diagnostic yield and should be ordered only if clinically indicated 2
• A standardized approach to syncope evaluation reduces hospital admissions and medical costs, and increases diagnostic accuracy 2

Diagnostic Criteria

• The classification of syncope is based on the underlying pathophysiological mechanism causing the event, and includes cardiac, orthostatic and reflex (neurally mediated) mechanisms 4
• Reflex syncope can be categorised into vasovagal syncope, situational syncope, carotid sinus syncope, and atypical reflex syncope 4
• Cardiovascular causes of syncope may be structural (mechanical) or electrical 4
• Orthostatic hypotension is caused by an abnormal drop in systolic blood pressure upon standing, and is defined as a decrease of >20 mmHg in systolic blood pressure or a reflex tachycardia of >20 beats/minute within 3 minutes of standing 4

Management

• Patients with life-threatening causes of syncope should be managed urgently and appropriately 4
• In patients with reflex or orthostatic syncope, it is important to address any exacerbating medication and provide general measures to increase blood pressure, such as physical counter-pressure manoeuvres 4
• Where heart disease is found to be the cause of the syncope, a specialist opinion is warranted and where possible the problem should be corrected 4
• Physical counter-pressure maneuvers (PCM) may provide benefit for prevention of syncope during acute episodes of presyncope and may be tried in the first aid setting 5

Risk Stratification

• Several comparable clinical decision rules can be used to assess the short-term risk of death and the need for hospital admission 2, 6
• Low-risk patients with a single episode of syncope can often be reassured with no further investigation 2
• 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 2