Transcatheter Management of Platypnea-Orthodeoxia Syndrome

Initially described in 1949 by Burchell et al.,1 the Platypnea-Orthodeoxia Syndrome (POS) is an uncommon symptom complex and was well characterized by the mid-1980s.2 POS is characterized by: 1) increased dyspnea in the upright position, relieved by assuming the recumbent position (platypnea); and 2) development or accentuation of hypoxemia in the upright position (orthodeoxia). The etiology of POS is not well understood and the syndrome is seen in association with several pulmonary disorders such as post-pneumonectomy or lobectomy, as well as obstructive lung disease, although it can occur without any associated pulmonary abnormalities.3 The symptoms appear to be secondary to intracardiac shunt via a patent foramen ovale (PFO) that is exaggerated in the upright position. These patients usually have normal right heart pressures and tend to be older. There are several proposed mechanisms including the horizontal displacement of the interatrial septum, leading to preferential blood flow from the inferior vena cava via the patent foramen ovale into the left atrium, with intermittent right-to-left shunting which is exaggerated in the upright position. This phenomenon does not require increased right atrial pressure; a proposed mechanism is the instantaneous pressure difference between the right and left atria,3 despite normal mean right atrial pressure. Incapacitating dyspnea, which improves in the recumbent position in the absence of overt pulmonary disease should raise the possibility of this syndrome. Confirmation of hypoxemia by pulse oximetry and lack of improvement of hypoxia by supplemental oxygen, indicating a fixed right-to-left shunt solidifies the suspicion. Documentation of dynamic change of arterial oxygen saturation between the upright and recumbent positions by arterial blood gas analysis or pulse oximetry confirms the diagnosis. The presence of intracardiac shunting at the level of the PFO may be documented by intravenous injection of agitated saline (bubble study) during echocardiography. Contrast echocardiography should be performed in both the supine and upright positions, perhaps with the use of tilt table, to demonstrate the orthostatic nature of bubble passage to the left side. This may be further demonstrated during transesophageal echocardiography which also allows for further delineation of the atrial septal anatomy and the frequently co-existing atrial septal aneurysms. Treatment of POS due to intracardiac shunting at the level of the foramen ovale is by its technically simple surgical closure and remains the standard. It should be considered if the patient requires surgical intervention for other reasons such as ascending aortic aneurysm or coronary artery disease. In the absence of coexisting disorders requiring cardiac surgery, transcatheter closure appears to be an effective management option.3–10 In this issue of the journal, Delgado and associates10 (see pages 578–582) describe clinical, echocardiographic and hemodynamic findings of 18 consecutive patients with POS who underwent transcatheter closure of their atrial defects (ADs). Devices to close the ADs were successfully implanted in all 18 patients; 6 were buttoned devices, 11 were CardioSeal and one Amplatzer PFO Occluder. Full occlusion at implantation was seen in 55% of the patients. By 24 hours, full occlusion was present in 12 (66%) patients, small shunt in 4 (22%) and moderate shunt in 2 (11%). The oxygen saturations in the upright position improved from 83% to 96%. Two patients required repeat intervention at 1 and 6 months, respectively, after the initial procedure to treat moderate residual shunts. Actuarial freedom from reintervention was 79% at the mean follow-up period of 2.9 years. This is a well written paper and, as the authors stated, is the largest single institution series of patients undergoing tramscatheter closure of ADs to treat POS. A few comments with regard to follow-up, technique and devices are in order. Follow-up. There appears to be some confusion with regard to the follow-up data presentation. My overall impression is that 2 patients required reintervention at 1 and 6 months, respectively, after initial device placement. But at one place (“Recurrent platypnea or orthodeoxia”), it says “6 years,” which may be a typo. Also, Figure 3 depicting freedom from recurrence and reintervention shows that no interventions occurred until 50 months, whereas moderate shunt with symptoms was noted at 1 and 6 months, requiring repeat transcatheter closure. Technique. The authors used general anesthesia and transesophageal echocardiography (TEE) along with fluoroscopy for device implantation. We prefer to perform the procedures under conscious sedation with either intracardiac echocardiographic (ICE) or transthoracic echocardiographic guidance for device implantation, especially because some of these patients have multiple health problems, making them unsuitable for general anesthesia. This is the preferred approach for closure of PFOs. In ASD cases, however, ICE or TEE guidance is required. Routine use of 11 French sheaths in all patients is not necessary; some devices can be implanted via smaller sheaths, depending upon the size of the device. Devices. Clamshell, buttoned, Amplatzer and CardioSeal devices have been used successfully in occluding PFOs to treat POS.6-9 The clamshell device is no longer in use, but its successor, CardioSeal, may be used under the Humanitarian Device Exemption (HDE). The buttoned device and, particularly, the hybrid version of the buttoned device,3,9,10 may be useful, but this device is no longer in clinical trials. The Amplatzer Septal Occluder, while approved by the FDA for closure of ostium secundum ASDs, it is not specifically designed for PFO. The modified version of the Amplatzer, the Amplatzer PFO occluder11 and PFO-Star12 are specifically designed to occlude PFOs, but are still in clinical trials although the Amplatzer PFO occluder may be used under the HDE. Other devices, namely, ASDOS, Das Angel Wing and Helex device, though not reported to have been used in the management of POS, have the potential to be useful in PFO occlusion in POS. ASDOS and Das Angel Wing devices are no longer in clinical trials, but the Helex device is undergoing clinical trials at present. A number of other recently described devices, namely Premere, SolySafe, SeptRx and BioStar are at varying stages of animal and human experimentation and may become useful in the treatment of ADs in POS. The device selection is largely based on the availability of a given device at a given institution. The protocols, procedures and methods of implantation of these devices are different from one to the other and should be mastered prior to their use. Summary and conclusions. POS is a unique clinical entity, uncommon but probably underdetected. It is characterized by dyspnea (platypnea) in the upright position associated with arterial hypoxemia (orthodeoxia). Both of these symptoms are relieved in the supine position. POS is usually associated with thoracic, pulmonary or aortic pathology, although it may rarely be seen without any discernable abnormalities. Posture-related right-to-left shunting across the PFO is thought to be the cause of symptoms seen in these patients. Closure of the PFO is clearly indicated to relieve the symptoms of patients with POS. Surgical closure is the standard treatment for PFO closure. POS patients usually have significant comorbidities that would make them high-risk surgical candidates. Transcatheter closure using a variety of devices is a safe, effective and less invasive alternative to surgical closure. This procedure can be done with either transthoracic, transesophageal or intracardiac echocardiographic guidance and requires an average of one-day hospital stay. Once the FDA approves some these devices for general use, transcatheter closure will become the treatment of choice for closure of PFO causing POS. Prior to such approval, the transcatheter option is available only at institutions participating in clinical trials with investigational device exemption.

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