Valsalva-induced syncope during apnea diving

Area of Science:

• Cardiology
• Neurology
• Sports Medicine

Background:

• Transient loss of consciousness (syncope) can occur during breath-hold diving.
• Autonomic nervous system dysfunction is a potential cause of syncope.

Observation:

• A young man experienced syncope with myoclonic jerks during apnea diving.
• Standard autonomic function tests were largely normal, except for an exaggerated blood pressure drop during the Valsalva maneuver.
• Physiologic recordings revealed significant drops in blood pressure and cerebral blood flow velocity during syncope.

Findings:

• Valsalva-induced syncope with myoclonic jerks was reproduced via straining.
• Findings were inconsistent with baroreflex failure or vasovagal mechanisms.
• Mechanical factors reducing cardiac blood return and a low brain ischemia threshold were implicated.

Implications:

• Highlights the role of mechanical factors in syncope during straining activities.
• Suggests a need to consider reduced cerebral perfusion thresholds in athletes.
• Informs risk assessment for individuals engaging in breath-hold activities.