Platypnea-Orthodeoxia Syndrome

A 62-year-old woman with a 25-year history of dyspnea was hospitalized because of hypoxemia. The dyspnea had become more severe during the past few years; it was worse in the standing position, was not exacerbated by walking, and was immediately relieved on lying down. She had no seasonal variation or environmental trigger of the dyspnea.

An oxygen saturation of 80% on room air prompted a ventilation-perfusion scan, which showed low probability of pulmonary embolism. Results of an ultrasonogram of the lower extremities were negative for deep venous thrombosis.

Her history included asthma/chronic obstructive pulmonary disease, cerebrovascular accident, hypertension, hypothyroidism, anxiety disorder, and obesity. She denied chronic liver disease and alcoholism.

Blood pressure was 153/78 mm Hg; respiration rate, 24 breaths per minute; oxygen saturation, 98% on 3 L; and jugular venous pressure, 5 to 6 cm. Cardiac and respiratory findings were normal. A chest radiograph showed an elevated left hemidiaphragm. Results of a high-resolution CT scan of the chest were normal. Pulmonary function tests with optimal patient effort revealed mild obstructive airways disease. A sniff test showed no evidence of paralysis of the right or left hemidiaphragm.

A complete 2-dimensional transesophageal echocardiogram with color Doppler and an agitated saline contrast injection on a tilt table (with omniplane probe insertion) showed mild aortic and mitral valvular regurgitation and normal left ventricular function, with an ejection fraction estimated to be 65% (A and B). The study also demonstrated a patent foramen ovale (PFO), with right-to-left shunting, and an atrial septal aneurysm (arrow), with a severe right-to-left shunt, which worsened in the upright position. The rest of the study findings were normal.

Chandar Abboy, MD, and Sunil Kumar Dama, MD, of Cincinnati suspected platypnea, and the patient was tested for orthodeoxia. Results showed an oxygen saturation of 97% on lying down that dropped to 90% on standing up.

The patient's PFO was not suitable for closure with a closure device. She underwent an open heart procedure, which revealed a Chiari network over the atrial septum. The fossa ovalis was prominent, but the interatrial septum was not aneurysmal, and there was a slitlike PFO at the top of the fossa ovalis in the classic position. The fossa was identified and closed with 2 mattress sutures.

Although rare, platypnea-orthodeoxia syndrome can be seen with cirrhosis of the liver, pulmonary arteriovenous malformations, chronic pulmonary embolism, intracardiac shunting, and postpneumonectomy.¹ This syndrome is most commonly associated with interatrial communications, mainly through a PFO and rarely through a true atrial septal defect.²

The cause of orthodeoxia with a PFO has not been determined.Three mechanisms have been suggested for this right-to-left shunt in the absence of pulmonary hypertension:

• External compression of the right atrium in the upright position, which causes an increase in right heart pressures.

• Decrease in right ventricular compliance.

• The possibility of an abnormal relationship between the inferior vena cava and the atrial septum where the blood is shunted through a PFO or atrial septal defect in the upright position.²

An intracardiac shunt with a PFO does not cause platypnea-orthodeoxia syndrome. The positional nature of platypnea-orthodeoxia syndrome in the absence of pulmonary hypertension suggests either structural anomalies or right atrial compression on standing.

In this patient, the interatrial aneurysm on the transesophageal echocardiogram was actually a Chiari network--a fenestrated membrane of threads and strands in the right atrium.³ The Chiari network is considered an embryonic remnant caused by incomplete resorption of the right valve of the sinus venosus. Usually of no clinical significance, the network is found in 2% to 3% of the population and can be associated with other complications, such as thrombus, catheter entanglement, and arrhythmia.³

Consider platypnea-orthodeoxia syndrome in the differential diagnosis of dyspnea. Although standard testing with ECG, chest radiography, and transthoracic echocardiography should be performed, it may not be diagnostic. Even a routine transthoracic echocardiogram does not rule out intracardiac shunting. To show intracardiac shunting based on positional changes, perform a transesophageal echocardiogram with a contrast study on a tilt table in the supine and upright position.

At follow-up, the patient's room-air oxygen saturation was 96%. A transthoracic echocardiogram with color Doppler showed mild aortic and moderate tricuspid valvular regurgitation. The estimated peak right ventricular systolic pressure was 46 mm Hg. No intracardiac shunt was detected by contrast study with agitated saline.

References:

REFERENCES:

1. Acharya SS, Kartan R. A case of orthodeoxia caused by an atrial septal aneurysm. Chest. 2000;118:871-874.
2. Faller M, Kessler R, Chaouat A, et al. Platypnea-orthodeoxia syndrome related to an aortic aneurysm combined with an aneurysm of the atrial septum. Chest. 2000;118:553-557.
3. Cooke JC, Gelman JS, Harper RW. Chiari network entanglement and herniation into the left atrium by an atrial septal defect occluder device. J Am Soc Echocardiogr. 1999;12:601-603.