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Interventional Cardiology
Closing the Patent Foramen Ovale with Amplatzer Devices
Bernhard Meier
Professor and Chairman, Cardiology, Cardiovascular Department, University Hospital Bern
Abstract
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.
Keywords
Foramen ovale, device closure, stroke, migraine
Disclosure: Bernhard Meier has received research grants and speaker fees from AGA Medical.
Received: 8 September 2008 Accepted: 28 November 2008
Correspondence: Bernhard Meier, Professor and Chairman of Cardiology, Cardiovascular Department, University Hospital, 3010 Bern, Switzerland. E: bernhard.meier@insel.ch
The patent foramen ovale (PFO) is a common remnant of the The risk of a PFO remains controversial. Case reports proving that
intrauterine phase. After birth, the pressure in the right atrium drops venous thrombi cross the PFO on one side and embolically occluded
with the first breath. The flap–valve-like gap between the cranial arterial vessels in otherwise healthy people on the other side suggest
muscular septum secundum and the caudal membranous septum that crossing these venous thrombi can cause paradoxical embolism.
primum closes like a door ajar in a draught. Normally, the two septa Opinions vary from the extreme point of view that PFO significantly
have sufficient overlap and the septum primum is quite stable, shortens life by intrinsic selective mortality to the point of view that
allowing permanent fusion of the gap. However, in about one in four paradoxical embolisms through the PFO are so rare that one should only
people mechanical fusion fails to occur and the gap remains bother with PFO closures in the case of a third otherwise unexplained
openable. Facilitating factors are lack of sufficient overlap (the septum cerebral vascular accident occurring under anticoagulation.
primum may even fail to reach the septum secundum, thereby
producing one of the various types of secundum atrial septal defects), The idea of selective mortality may be corroborated by the fact
an extremely thin and mobile septum primum (also called atrial septal that the prevalence of PFO decreases with age.
1
The only other
aneurysm [ASA]) or a Eustachian valve (a Chiari network bundling the explanation for this finding is spontaneous closure of the PFO
inferior vena cava flow directly onto the site of the foramen ovale). throughout life; this second, conservative point of view is shared by
Combinations of these factors compound the chance of a persistent American specialists, who have published the most recent guidelines.
2
PFO and also render it more dangerous (e.g. opening with virtually
every heart beat, even when there is no increased pressure in the Even taking an intermediate position, textbooks and definitions will
right atrium, such as after a Valsalva manoeuvre). need to be rewritten. The term cryptogenic stroke cannot be used in
© TOUCH BRIEFINGS 2009 71
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