Procedure
PFO and ASD closure
A hole between the two upper chambers, closed by a device delivered through a vein. Of everything done here, this is the procedure where choosing the right patient matters most — the trials only became positive once they got that part right.
The Anatomy
A PFO and an ASD are not the same thing
They are often mentioned together because both are openings between the atria and both can be closed the same way. The reasons for closing them are quite different.
Patent foramen ovale (PFO)
Before birth, blood bypasses the lungs through a flap between the two upper chambers of the heart. In most people that flap seals in infancy. In roughly a quarter of adults it never fully does, leaving a passage that usually stays shut because pressure holds it closed — but that can open when pressure on the right side rises, as it does when you strain or cough. A PFO is a normal variant, not a disease. Most people with one will never know and never need anything done.
Atrial septal defect (ASD)
An ASD is a true hole in the wall between the upper chambers rather than an unsealed flap. Blood flows continuously from the left side to the right, which sends extra volume through the right heart and lungs year after year. Over decades that extra work enlarges the right heart, and it is the strain rather than the hole itself that becomes the problem.
Selection
Who this actually helps
Around a quarter of adults have a patent foramen ovale and almost none of them need anything done. The question is never whether one is present but whether it explains what happened.
- A stroke with no other explanation
- The usual reason to close a PFO is an ischaemic stroke in a younger patient where a thorough workup has found no other cause — no atrial fibrillation, no carotid disease, no small vessel disease. The theory is that a clot from the venous circulation crossed through the flap instead of being filtered by the lungs. Closure is secondary prevention: it is done to stop a second stroke, not a first.
- An ASD that is straining the right heart
- Where a defect is large enough that the right atrium and ventricle have enlarged, closure removes the extra volume load. This is a different and more mechanical indication than the PFO one, and the evidence behind it is not in dispute.
- Selection is the whole procedure
- The early PFO trials were negative. They only became positive once enrolment was narrowed — the CLOSE trial, for instance, required patients aged 16 to 60, a stroke within the previous six months with imaging to corroborate it, and a large shunt or an atrial septal aneurysm, while excluding small vessel disease and significant narrowing of an artery supplying the brain. Closing a PFO in someone outside that profile exposes them to the risks without the benefit.
~1%
Annual risk of another stroke on medical therapy alone, in the trial populations
<0.5%
Annual risk after closure, in appropriately selected patients
3
Randomised trials — RESPECT, REDUCE, and CLOSE — behind that difference
These figures come from the published trials, not from this center, and they describe the populations those trials enrolled. They are not a prediction about any individual patient.
The Procedure
What the day looks like
For a PFO the hardest part happens before the procedure, in deciding whether to do it at all.
- 1
Before anything is scheduled
For a PFO, the decision comes before the procedure and involves more than one specialty: the stroke workup has to be complete and genuinely negative, which usually means prolonged rhythm monitoring to exclude atrial fibrillation as the real culprit. Closing a PFO in someone whose strokes are actually caused by undetected AF treats the wrong thing.
- 2
Sedation and access
The procedure is done under sedation, through a vein in the groin. Imaging guides it throughout — either an ultrasound probe in the esophagus or one inside the heart, alongside X-ray.
- 3
Measuring the defect
The opening is crossed with a catheter and sized directly. Choosing a device that matches the anatomy is what determines whether it sits securely and seals completely.
- 4
Placing the device
The device is folded inside a delivery catheter, advanced across the defect, and opened so that a disc sits on each side of the wall, gripping it between them. Its position and seal are confirmed on imaging before the delivery system is released.
- 5
Recovery and going home
You are monitored for a defined period and most patients go home the same day. You will be on antiplatelet medication for a period afterwards, and endocarditis precautions apply for the first six months while the device is being covered by your own tissue.
- 6
The months afterwards
Tissue grows over the device during roughly six months, after which it becomes part of the wall. Follow-up imaging confirms it is in position and the defect is sealed. Antibiotic cover before dental work is advised during that period.
Excluding atrial fibrillation is part of the workup, not an afterthought — a stroke caused by undetected AF is not treated by closing a PFO. That is one advantage of having this conversation at a center whose main work is atrial fibrillation, with long-term rhythm monitoring available to settle the question properly.
Risks
What can go wrong, and how likely it is
The first entry is the one to read twice, because it is the risk most specific to this procedure.
New atrial fibrillation
Both the REDUCE and CLOSE trials found more atrial fibrillation in the patients who had closure, and it appears to be caused by the procedure itself — a device placed in the atrial wall irritating tissue that is sensitive to being irritated. Most of it is early and settles. It is worth taking seriously here of all places, because atrial fibrillation is its own risk factor for stroke, which is the thing the closure was done to prevent.
Device problems
A device can sit poorly, move, or leave a small residual leak. Any of these can require a second procedure, and rarely surgery. Correct sizing at the time is the main protection against it.
Fluid around the heart
Crossing the atrial wall and manipulating catheters there can perforate it and allow blood to collect around the heart. Uncommon, and managed by draining the fluid.
Stroke during the procedure
Air or clot can travel through the catheter system. Anticoagulation during the case and careful technique with the delivery system are what reduce it.
Bleeding at the access site
Bruising is common and settles; a larger collection or vessel injury is less common and occasionally needs attention.
It may not prevent every stroke
Closure reduces the risk of another stroke in the right patient. It does not remove it, and it does nothing about the other causes of stroke — blood pressure, cholesterol, diabetes, smoking, and atrial fibrillation all still matter just as much afterwards as before.
Sources
Questions about your procedure?
Our team will confirm your date, walk you through preparation, and answer questions about insurance, sedation, and recovery.