What to check in a patient with vasovagal (vasovagal syncope) syncope associated with defecation?

From the Guidelines

When evaluating a patient with vasovagal syncope associated with defecation, it is crucial to focus on both cardiac and gastrointestinal factors to prioritize morbidity, mortality, and quality of life as outcomes.

Key Evaluation Steps

• Obtain a detailed history of the syncopal episodes, including timing, duration, prodromal symptoms, and recovery, as emphasized in the 2017 ACC/AHA/HRS guideline for the evaluation and management of patients with syncope 1.
• Check orthostatic vital signs and perform a thorough cardiovascular examination, including an ECG to rule out arrhythmias or conduction abnormalities, which is a critical step in identifying potential cardiac causes of syncope.
• Consider a 24-hour Holter monitor or event recorder if episodes are frequent, to capture any transient cardiac abnormalities that might be contributing to the syncope.
• Assess for gastrointestinal issues such as constipation, hemorrhoids, or anal fissures that may cause straining during defecation, as these can trigger vasovagal syncope.

Management Strategies

• Review medications that might contribute to syncope, particularly antihypertensives, diuretics, or those with anticholinergic effects, and adjust them as necessary to minimize the risk of syncope.
• Laboratory tests should include complete blood count, electrolytes, and blood glucose to identify anemia or electrolyte imbalances that could predispose to syncope.
• Management typically involves addressing constipation with increased fluid intake, dietary fiber (25-30g daily), and regular exercise, which can help reduce straining during defecation and thereby decrease the risk of vasovagal syncope.
• For persistent constipation, consider osmotic laxatives like polyethylene glycol (17g daily) or stool softeners like docusate sodium (100mg twice daily), as these can help manage constipation without exacerbating the risk of syncope.
• Advise patients to avoid prolonged straining, use proper positioning during defecation, and perform counter-pressure maneuvers if prodromal symptoms occur, as these strategies can help prevent vasovagal syncope episodes.

Pathophysiological Considerations

These recommendations target the pathophysiology of vasovagal syncope, which involves inappropriate vagal activation causing bradycardia and vasodilation, leading to cerebral hypoperfusion and loss of consciousness, as described in the guidelines 1. By addressing both cardiac and gastrointestinal factors, and by implementing strategies to manage constipation and prevent straining during defecation, healthcare providers can effectively reduce the risk of vasovagal syncope and improve patient outcomes.

From the Research

Vasovagal Syncope with Defecation

To check in a patient with vasovagal syncope associated with defecation, consider the following:

• Clinical characteristics: Patients with defecation syncope (DS) tend to be older women, whereas those with micturition syncope (MS) tend to be middle-aged men 2.
• Triggering factors: Identify any triggering factors, such as straining during defecation, which can lead to vasovagal syncope 2.
• Heart rate and blood pressure variability: Assess heart rate and blood pressure variability, as patients with vasovagal syncope may have increased vagal sinus modulation at rest 3.
• Tilt-test responses: Use spectral indices of heart rate variability to predict tilt-test responses, which can help diagnose vasovagal syncope 3.
• Autonomic nervous system control: Evaluate autonomic nervous system control, as it is controversial in subjects with vasovagal syncope 3.
• Medical history: Take a thorough medical history, including the frequency and recurrence of syncopal episodes, as patients with common vasovagal syncope tend to have more recurrent episodes 2.
• Physical examination: Perform a physical examination, including blood pressure and heart rate measurement, to assess for any underlying conditions that may contribute to vasovagal syncope 4, 5, 6.

Diagnostic Tests

Consider the following diagnostic tests:

• Head-up tilt test: Use a head-up tilt test to diagnose vasovagal syncope, as it can help predict the risk of syncope 5, 3, 2.
• Electrocardiogram (ECG): Perform an ECG to rule out any underlying cardiac conditions that may contribute to syncope 4, 6.
• Blood tests: Conduct blood tests to rule out any underlying medical conditions that may contribute to syncope, such as anemia or electrolyte imbalances 4, 6.