Platypnea-orthodeoxia syndrome

OVERVIEW

Platypnea-orthodeoxia (P-O) syndrome is an under-diagnosed condition characterized by dyspnea and deoxygenation when changing from a recumbent to an upright position

• It is usually caused by increased right-to-left shunting of blood on assuming an upright position, with normal pressure in the right atrium
• It may also be caused by intrapulmonary shunting combined with extensive pulmonary lesions or severe V/Q mismatching

CAUSES

Common

• Atrial septal defect (ASD) or persistent foramen ovale (PFO) (present in ~20-25% of the population)
  • position-dependent shunting, often in combination with one of the rarer conditions below.
  • right-to-left shunt causes hypoxia, from either
    1. right atrial pressure > left atrial pressure, or
    2. mechanical distortion – of either the fossa ovalis itself or the flow of blood from the IVC to the ASD/PFO

Rare

• Other Cardiac
  • Pericardial effusion
  • Constrictive pericarditis
  • Aortic aneurysm
  • Tricuspid regurgitation
  • Mediastinal shift
• Pulmonary
  • Multiple pulmonary emboli
  • Pulmonary emphysema
  • Radiation-induced bronchial stenosis
  • Hepatopulmonary syndrome
  • Amiodarone toxicity of the lungs
  • Pulmonary A-V communications
  • PCP pnuemonia
  • fat embolism syndrome
• Autonomic
  • Parkinson disease
  • Bilateral thoracic sympathectomy
• Abdominal
  • Hepatic cirrhosis
  • Ileus

INVESTIGATIONS

• failure of correction of hypoxia during 100% oxygen test
• supine and upright PaO2 measurement
  • with upright deoxia
• tilt transesophageal echocardiogram with bubble study (<100% sensitive) - diagnosis of the shunt can be difficult
  • A syringe filled with 9 ml saline and 1 ml air is agitated, macroscopic bubbles expelled and the remaining microbubble emulsion injected IV
  • The test is positive if microbubbles are seen in the left atrium within two to three cycles of the initial appearance in the right atrium
  • Injection of contrast via the leg may increase the sensitivity of the test as most shunting occurs via the IVC
• look for other underlying causes

MANAGEMENT

• Closure of the ASD or PFO
  • temporary closure by balloon occlusion
  • permanent occlusion by open surgery or percutaneous intervention
• Treat any associated condition, examples include:
  • A case associated with Parkinson’s disease was attributed to postural hypotension and improved with fludrocortisone
  • A case associated with radiation-induced bronchial stenosis was relieved by bronchial dilation initially, and later by bronchial stenting
  • A case associated with bilateral thoracic sympathectomy (van Heerdon 2004) was treated initially with noradrenaline and almitrine

References and Links

• Cheng TO. Mechanisms of platypnea-orthodeoxia: what causes water to flow uphill?. Circulation. 2002;105(6):e47. [article]
• Cheng TO. Platypnea-orthodeoxia syndrome: etiology, differential diagnosis, and management. Cathet Cardiovasc Interv. 1999; 47: 64–66. PMID: 10385164 [article]
• Jacob L, Bonnet F, Pavie A, et al. Severe hypoxemia revealing traumatic tricuspid regurgitation with right-to-left intracardiac shunt. J Trauma. 1985;25(7):659-61. PMID: 4009773
• Lee CH, Cheng ST. Shortness of breath while sitting up: hepatopulmonary syndrome. CMAJ. 2011 Jan 11;183(1):80. PMC3017258.
• Ptaszek LM, Saldana F, Palacios IF, M Wu S. Platypnea-Orthodeoxia Syndrome in Two Previously Healthy Adults: A Case-based Review. Clin Med Cardiol. 2009 Apr 9;3:37-43. PMC2872575.
• Salvetti M, Zotti D, Bazza A, Paini A, Bertacchini F, Chiari E, Coletti G, Rosei EA, Muiesan ML. Platypnea and orthodeoxia in a patient with pulmonary embolism. Am J Emerg Med. 2013 Apr;31(4):760.e1-2. PMID: 23380102.