What is platypnea and how is it managed?

Platypnea: Definition and Management

Platypnea is a rare clinical condition characterized by dyspnea (shortness of breath) that worsens in the upright position and improves when lying down, often associated with orthodeoxia (decreased oxygen saturation when upright). 1, 2

Definition and Pathophysiology

Platypnea is the opposite of orthopnea and is typically part of platypnea-orthodeoxia syndrome (POS), which has two key features:

• Platypnea: Positional dyspnea that worsens when standing/sitting and improves when lying down
• Orthodeoxia: Arterial desaturation that occurs in the upright position and improves in the recumbent position

The syndrome is caused by a right-to-left shunt that can occur at either:

• Intracardiac level: Most commonly through a patent foramen ovale (PFO) 3, 4
• Intrapulmonary level: Such as in pulmonary arteriovenous malformations (PAVMs) 1

Clinical Presentation

Key clinical features include:

• Dyspnea that worsens when sitting or standing
• Improvement of symptoms when lying down
• Hypoxemia in the upright position that improves when recumbent
• May present with symptoms of paradoxical embolism (stroke, TIA) if intracardiac shunt is present 4

Diagnostic Approach

1. Clinical recognition: Suspect platypnea when patients report dyspnea that worsens upon standing

2. Confirm orthodeoxia: Measure oxygen saturation in both upright and supine positions to document positional desaturation

3. Identify underlying cause:

   • Echocardiography: Transthoracic and transesophageal echocardiography with bubble study to detect intracardiac shunts 4, 5
   • CT angiography: To identify pulmonary arteriovenous malformations 1
   • Cardiac catheterization: To assess hemodynamics and confirm right-to-left shunting 4

Management

Management depends on the underlying cause:

For Intracardiac Shunts (e.g., PFO)

• Transcatheter closure of the defect is the definitive treatment 4, 5
• This procedure can lead to complete resolution of symptoms and normalization of oxygen saturation

For Pulmonary Arteriovenous Malformations

• Percutaneous transcatheter embolization of the feeding artery is the treatment of choice 1
• Any PAVM detected by CT or catheter angiography should be considered for treatment due to the risk of paradoxical embolism
• Follow-up CT angiography within 6-12 months after treatment, then every 3-5 years

Supportive Measures

• Oxygen therapy for symptomatic hypoxemia (O₂ saturation <90%) 6
• Positioning: Advise patients to lie down when experiencing severe symptoms
• Non-pharmacological approaches: Cooling the face, using small ventilators, proper positioning 6

Special Considerations

• Pregnancy: Associated with rapid growth of PAVMs due to hormonal and hemodynamic changes, with higher risk of complications 1
• Kyphosis and osteoporosis: Can cause or exacerbate platypnea-orthodeoxia by changing cardiac position 5
• Pulmonary embolism: Can be associated with platypnea-orthodeoxia when combined with PFO 7

Prognosis

Prognosis is excellent when the underlying cause can be definitively treated:

• Closure of intracardiac shunts typically results in immediate symptom resolution 4
• Embolization of PAVMs has high success rates, though persistent perfusion may occur in 0-21% of cases depending on the embolic material used 1

Platypnea-orthodeoxia syndrome should be considered in any patient with unexplained positional dyspnea, especially when accompanied by positional oxygen desaturation, as definitive treatment can lead to complete symptom resolution.