What is the difference in hemodynamics between Müller's (Müller's maneuver) and Valsalva (Valsalva maneuver) in patients with patent foramen ovale (PFO)?

Hemodynamic Differences Between Müller's and Valsalva Maneuvers in Patent Foramen Ovale

The Valsalva maneuver creates superior right-to-left pressure gradients across a patent foramen ovale compared to the Müller maneuver, making it the preferred provocative technique for PFO detection and assessment.

Physiological Mechanisms

Valsalva Maneuver

• Definition: Forced expiratory effort against a closed glottis for 10-30 seconds (equivalent to 30-40 mmHg pressure) 1
• Hemodynamic effects in PFO:
  • Increases intrathoracic pressure
  • Transiently increases right atrial pressure relative to left atrial pressure
  • Creates a right-to-left pressure gradient across the atrial septum
  • Enhances right-to-left shunting through the PFO 1, 2
• Clinical significance: Detected in 84% of patients as the most effective maneuver for creating right-to-left atrial pressure gradients 2

Müller Maneuver

• Definition: Forced inspiratory effort against a closed upper airway 3
• Hemodynamic effects in PFO:
  • Generates negative intrathoracic pressure
  • Creates different cardiac loading conditions compared to Valsalva
  • Less effective at creating the right-to-left pressure gradient needed to detect PFO shunting
  • Not standardized for PFO detection in clinical guidelines 3

Clinical Applications in PFO Assessment

Diagnostic Superiority of Valsalva

• Valsalva maneuver is specifically mentioned in guidelines as the standard provocative technique for PFO detection 1, 4
• The REDUCE trial specifically noted that PFO with right-to-left shunting during Valsalva was a key inclusion criterion for patients who benefited from PFO closure 1
• Valsalva creates significantly higher mean pressure gradients and longer duration of pressure overlap between atria compared to other maneuvers 2

Technical Considerations

• Proper Valsalva technique:
  • Patient should be in supine position
  • Bearing down against closed glottis for 10-30 seconds
  • Pressure equivalent to 30-40 mmHg 1
• Adequacy assessment: A 20 cm/sec decrease in transmitral E velocity indicates an effective Valsalva maneuver 5
• Detection rates: Adequate Valsalva maneuver during echocardiography significantly improves PFO detection (missed only 9% of PFOs vs. 19% when inadequately performed) 5

Clinical Implications for PFO Management

Risk Stratification

• The magnitude of right-to-left shunting during Valsalva helps quantify PFO significance:
  • Moderate shunt: 6-25 microbubbles
  • Large shunt: >25 microbubbles crossing the atrial septum 1
• Larger shunts detected during Valsalva are associated with higher stroke risk and greater benefit from PFO closure 1, 4

Therapeutic Decision-Making

• PFO closure decisions are influenced by shunt size during Valsalva:
  • The CLOSE trial required either atrial septal aneurysm or large interatrial shunt (>30 microbubbles) during Valsalva for inclusion 1
  • The REDUCE trial showed benefit in patients with moderate-to-large shunts during Valsalva 1

Practical Recommendations

1. For PFO detection:

   • Use Valsalva as the primary provocative maneuver during contrast echocardiography
   • Ensure proper technique with adequate duration (10-30 seconds) and pressure (30-40 mmHg)
   • Verify effectiveness by observing decreased transmitral flow

2. For hemodynamic assessment:

   • Quantify shunt size during Valsalva for risk stratification
   • Consider PFO closure for patients ≤60 years with large shunts during Valsalva and cryptogenic stroke 1, 4

3. For research protocols:

   • Standardize Valsalva technique when studying PFO-related outcomes
   • Consider the timing of contrast injection relative to Valsalva phase for optimal detection

The Valsalva maneuver remains the gold standard for creating the hemodynamic conditions necessary to detect and assess PFOs, with superior right-to-left pressure gradients compared to the Müller maneuver 2.