Platypnoea orthodeoxia syndrome is a rare condition in which shortness of breath and hypoxaemia occur when upright and resolve when prone. The hypoxaemia results from increased right to left shunting of deoxygenated blood, when standing, through a patent foramen ovale (PFO), atrial septal defect (ASD) or other right to left shunt, in the absence of raised right-heart pressure. We present the case of a patient with platypnoea orthodeoxia with marked shunting through a large PFO, evaluated by transesophageal and transthoracic echo.
A 71-year-old man was referred for investigation of unexplained hypoxaemia. He complained of exertional shortness of breath, initially thought to be secondary to moderate aortic regurgitation due to a dilated aortic root. There were no clinical features of connective tissue disorders and the aortic root dilatation was presumed secondary to hypertension. Whilst attending the cardiothoracic surgery outpatients for consideration for surgery he was found to be hypoxic with oxygen saturations (SaO 2 ) of 88% that was felt to be out of keeping with the severity of the valvular abnormality.
Surgery was postponed and he underwent a number of investigations. Pulmonary function tests showed normal lung function with an FEV1 of 2.9L/min and an FVC of 3.75L. A chest radiograph was normal and a CT scan showed minor basal bronchiectasis only, with no other pulmonary pathology. The aortic root was dilated to 4.8cm. A transthoracic echocardiogram confirmed a symmetrically dilated aortic root with moderate aortic regurgitation on colour Doppler. The aortic valve had three equally sized cusps which were thin and pliable. The left ventricular size and function were normal and there were no other valvular abnormalities.
A transesophageal echo was performed, under sedation, to further evaluate the valvular pathology. The aortic pathology was confirmed and it also showed an aneurysmal interatrial septum and a PFO with a right to left shunt, seen by the passage of a large amount of agitated saline contrast into the left heart using an upper limb contrast injection ( Figs. 1 and 2 ). Right ventricular size and function were normal as was the estimated pulmonary artery systolic pressure (PASP). Cardiac catheterization showed minor non-obstructive coronary artery disease, an aortogram confirmed the dilated aortic root with moderate aortic regurgitation. Right-heart catheterization revealed normal right-sided pressures, including PASP. A shunt calculation showed a Qp/Qs of less than 1:1.5. Twenty-four-hour oximetry, however, showed several episodes of profound hypoxaemia during the day with SaO 2 of approximately 85%.
The episodic hypoxaemia was investigated further. In the supine position SaO 2 was approximately 96% but fell to 85% on standing and platypnoea orthodeoxia was suspected. The anatomical shunt calculated after breathing 100% oxygen for 20min in the supine position was 5% but when repeated in the upright position was 31%.
The transthoracic echo was then repeated to assess the effect of posture on the shunt through the PFO, with a femoral line inserted for contrast injections, in the supine and standing positions. When supine SaO 2 breathing air was 98% and injection of agitated saline contrast showed right to left shunting with a large number of bubbles crossing to the left heart in three beats of injection ( Fig. 3 ). On injection of contrast in the standing position there was total opacification of the left heart within three beats indicating a marked increase in the shunt volume ( Fig. 4 ). SaO 2 also fell in the standing position to 88%. This confirmed the diagnosis of platypnoea orthodeoxia with both a fall in his oxygenation and a marked increase in right to left shunting via the PFO in the standing position.
Platypnoea orthodeoxia syndrome (POS) is an uncommon condition whose exact mechanism remains poorly understood. For it to occur a right to left shunt must be present. This can be intrapulmonary due to arteriovenous malformations or intracardiac from a PFO or ASD. A physiological shunt in patients with pulmonary fibrosis is another recognized cause. 1–4 POS has been described following right pneumonectomy and in association with other thoracic deformities. Eicher et al. recently reported a series of 19 patients with POS, 12 of whom had a dilated aortic root. 2 Four of these 12 patients also had thoracic pathology, but in the remaining eight the dilated aortic root was the only abnormality.
The association between intra-thoracic or aortic root pathology and POS is postulated to be due to distortion of right atrial anatomy occurring when the patient adopts the upright posture. The relationship between the inferior vena cava (IVC) and the right atrium is altered in the standing position leading to a change in flow dynamics with the deoxygenated IVC blood directly towards the fossa ovalis and hence preferentially through the PFO or ASD.
As we suspected a diagnosis of POS in our patient we elected to inject contrast from the right femoral vein to maximise our chances of detecting a change in the magnitude of the right to left shunt with position. Even in patients without POS, injection of contrast from the arm may not achieve adequate opacification of the right atrium due to selective streaming of IVC flow towards the interatrial septum. Several authors have highlighted the advantage of injecting contrast from the leg in this case when attempting to demonstrate the presence of a PFO. 5,6 It is our practice to perform contrast injection from the right femoral vein in patients with suboptimal right atrial opacification during injection from the arm and a high clinical probability of embolic stroke disease.
Imaging of a patient in the standing position is technically more difficult than in the standard left lateral position. However, in patients with unexplained breathlessness related to changes in posture, the diagnosis of platypnoea orthodeoxia should be considered. In those patients with an intracardiac shunt, assessment of the degree of shunting with changes in posture should be considered.
Treatment of this condition is by closure of the septal defect either by open or percutaneous methods. These options were discussed with our patient but after reflection he felt that his symptoms were not sufficiently troublesome to warrant closure of his PFO at this time. He remains under review in the out-patient clinic for monitoring of his symptoms and his aortic pathology.