The relative risk of a thromboembolic event is four-fold higher in the 25–35% of adults with a patent foramen ovale (PFO) and 33-fold higher in patients who also have an atrial septal aneurysm. The American PICSS trial showed a yearly incidence of stroke or death after an initial event of 5% with warfarin and 9% with acetylsalicylic acid. The presence of a PFO more than doubles the mortality rate in patients with clinically relevant pulmonary embolism. The risk of a PFO increases with age. Proof of effectiveness in migraine alleviation is likely to be achievable in a couple of years – much quicker than in prevention of paradoxical embolism. Percutaneous closure of PFO has been performed with various devices at the University Hospital Bern in Switzerland since April 1994, with over 1,000 patients treated. At the last available transoesophageal echocardiogram, a significant residual shunt persisted in 4% with Amplatzer devices and 17% with other devices. During follow-up, a recurrent embolic event was observed in 1.6% of patients per year – less than would be expected under medical treatment. Several randomised multicentre trials comparing catheter closure with medical treatment have been started. The PC and CLOSURE trials are in the follow-up phase; results cannot be expected before 2010, and they may well be ‘falsely’ neutral because the follow-up is rather short for the low-risk patients randomised. In a matched control study on patients with cryptogenic stroke and a PFO, 158 patients were treated medically and 150 concomitant patients underwent percutaneous PFO closure. At four years, PFO closure resulted in a trend towards risk reduction of death, stroke or transient ischaemic attack (TIA) (9 versus 24%; p=0.08) compared with medical treatment. The calculated occurrence of patients with cryptogenic strokes associated with a PFO amounts to somewhere between 100 and 300 per year and per million population, corresponding to more than 10% of yearly coronary angioplasty cases. Coronary and peripheral paradoxical emboli without prior exclusion of competing causes plus the presumed associations between PFO and migraine or decompression illness in divers open additional vast fields of potential indications for catheter closure. Finally, the linearly decreasing prevalence of a PFO with age suggests a weeding out of PFO carriers (unless spontaneous closure is assumed). A PFO represents a lethal threat that increases with age. It can be closed percutaneously in 15 minutes virtually free of complications. The patient can resume unrestricted physical activities a few hours after the intervention.
The patent foramen ovale (PFO) is a common remnant of the intrauterine phase. After birth, the pressure in the right atrium drops with the first breath. The flap–valve-like gap between the cranial muscular septum secundum and the caudal membranous septum primum closes like a door ajar in a draught. Normally, the two septa have sufficient overlap and the septum primum is quite stable, allowing permanent fusion of the gap. However, in about one in four people mechanical fusion fails to occur and the gap remains openable. Facilitating factors are lack of sufficient overlap (the septum primum may even fail to reach the septum secundum, thereby producing one of the various types of secundum atrial septal defects), an extremely thin and mobile septum primum (also called atrial septal aneurysm [ASA]) or a Eustachian valve (a Chiari network bundling the inferior vena cava flow directly onto the site of the foramen ovale). Combinations of these factors compound the chance of a persistent PFO and also render it more dangerous (e.g. opening with virtually every heart beat, even when there is no increased pressure in the right atrium, such as after a Valsalva manoeuvre).
The risk of a PFO remains controversial. Case reports proving that venous thrombi cross the PFO on one side and embolically occluded arterial vessels in otherwise healthy people on the other side suggest that crossing these venous thrombi can cause paradoxical embolism. Opinions vary from the extreme point of view that PFO significantly shortens life by intrinsic selective mortality to the point of view that paradoxical embolisms through the PFO are so rare that one should only bother with PFO closures in the case of a third otherwise unexplained cerebral vascular accident occurring under anticoagulation.
The idea of selective mortality may be corroborated by the fact that the prevalence of PFO decreases with age.1 The only other explanation for this finding is spontaneous closure of the PFO throughout life; this second, conservative point of view is shared by American specialists, who have published the most recent guidelines.2
- Hagen PT, Scholz DG, Edwards WD, Incidence and size of patent foramen ovale during the first 10 decades of life: an autopsy study of 965 normal hearts, Mayo Clin Proc, 1984;59:17–20.
- Sacco RL, Adams R, Albers G, et al., Guidelines for prevention of stroke in patients with ischemic stroke or transient ischemic attack: a statement for healthcare professionals from the American Heart Association/ American Stroke Association Council on Stroke: cosponsored by the Council on Cardiovascular Radiology and Intervention: the American Academy of Neurology affirms the value of this guideline, Stroke, 2006;37: 577–617.
- Meier B, Closure of the patent foramen ovale. The end of the sound and vision era approaching, JACC Cardiovasc Interv, in press.
- Windecker S, Meier B, Patent foramen ovale and cryptogenic stroke: to close or not to close? Closure: what else!, Circulation, in press.
- Windecker S, Wahl A, Nedeltchev K, et al., Comparison of medical treatment with percutaneous closure of patent foramen ovale in patients with cryptogenic stroke, J Am Coll Cardiol, 2004;44:750–58.