What is the approach to a patient with recurrent syncope (fainting) and its underlying causes?

From the Guidelines

The approach to a patient with recurrent syncope should prioritize identifying the underlying cause, with a focus on cardiac, reflex-mediated, and orthostatic hypotension causes, and management should be tailored to the specific cause, with consideration of the latest guidelines from the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society 1. When evaluating a patient with recurrent syncope, it is essential to consider the following key points:

• A thorough history, physical examination, and electrocardiogram (ECG) are crucial to identify the underlying cause of syncope, which can be categorized into cardiac, reflex-mediated, and orthostatic hypotension causes.
• Initial evaluation should include orthostatic vital signs, detailed medication review, and assessment of prodromal symptoms, as recommended by the 2017 ACC/AHA/HRS guideline for the evaluation and management of patients with syncope 1.
• For patients with suspected cardiac syncope, further testing should include echocardiography, ambulatory cardiac monitoring, and possibly electrophysiology studies if arrhythmias are suspected.
• For reflex-mediated syncope, tilt-table testing may be helpful, and management may include increased salt and fluid intake, physical counterpressure maneuvers, and sometimes midodrine (2.5-10mg three times daily) or fludrocortisone (0.1-0.2mg daily), as suggested by the 2017 ACC/AHA/HRS guideline 1.
• Orthostatic hypotension requires addressing underlying causes, medication adjustments, compression stockings, and possibly pharmacologic therapy.
• Patients should be counseled about driving restrictions and fall prevention while evaluation and treatment are ongoing, as emphasized by the 2019 American Heart Association and American Red Cross focused update for first aid 1. Some key management strategies for specific causes of syncope include:
• Midodrine (2.5-10mg three times daily) is a reasonable option for patients with recurrent vasovagal syncope with no history of hypertension, heart failure, or urinary retention, as it has been associated with a 43% reduction in syncope recurrence 1.
• Physical counterpressure maneuvers (PCMs) may be beneficial in preventing syncope in patients with vasovagal or orthostatic presyncope, as suggested by the 2019 American Heart Association and American Red Cross focused update for first aid 1.
• Fludrocortisone (0.1-0.2mg daily) might be reasonable for patients with recurrent vasovagal syncope and inadequate response to salt and fluid intake, unless contraindicated, as it has been associated with a marginally insignificant 31% risk reduction in adults with moderately frequent vasovagal syncope 1.

From the Research

Approach to Patient with Recurrent Syncope

• The goals of the clinical assessment of a patient with syncope are to identify the precise cause and to quantify the risk to the patient 2
• A structured approach to the patient with syncope is required, with history-taking being the most important aspect of the clinical assessment 2
• The classification of syncope is based on the underlying pathophysiological mechanism causing the event, and includes cardiac, orthostatic, and reflex (neurally mediated) mechanisms 2

Causes of Syncope

• Cardiovascular causes of syncope may be structural (mechanical) or electrical 2
• 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 2
• Reflex syncope can be categorised into vasovagal syncope, situational syncope, carotid sinus syncope, and atypical reflex syncope 2

Diagnosis and Management

• A thorough history and physical examination, including orthostatic assessment, are crucial for making the diagnosis 3
• Short-term risk assessment should be performed to determine the need for admission 3
• In patients with suspected cardiac syncope, monitoring is indicated until a diagnosis is made 3
• In patients with suspected reflex syncope or orthostatic hypotension, outpatient evaluation with tilt-table testing is appropriate 3
• Syncope units have been shown to improve the rate of diagnosis while reducing cost and thus are highly recommended 3

Specific Considerations

• Arrhythmic syncope is cardiac syncope specifically due to rhythm disorders, and both bradyarrhythmia and tachyarrhythmia can cause a sudden decrease in cardiac output and produce syncope 4
• The ECG in patients with syncope should be examined carefully for signs of structural heart disease, conduction system disease, and primary electrical disease 5
• Important forms of cardiomyopathy accompanied by ECG changes include hypertrophic cardiomyopathy and arrhythmogenic right ventricular dysplasia 5
• Common ECG findings in patients with syncope include left ventricular hypertrophy, repolarization abnormalities, QRS widening, and pseudoinfarction patterns 5