18.1 PFO & ASD Closure

PFO & ASD Closure

ARRT Cardiac-Interventional Procedures 2.B.1 is percutaneous closure of a patent foramen ovale (PFO) and an atrial septal defect (ASD). The same interventional Focus of Questions used throughout 2.B applies on every case: anatomy and pathophysiology, indications, contraindications, imaging, access, ultrasound, equipment, complications, and closure. These are right-heart, usually femoral-venous device implants. They are not coronary stents, and they are not a license to device-close every hole in the atrial septum.

Quick Answer: A PFO is a flap-like tunnel. A secundum ASD is a true tissue deficiency in the fossa ovalis and is the device-closable ASD. Primum and sinus venosus ASDs are usually surgical. Cryptogenic stroke is the classic PFO indication after a workup that found no other source. Image with ICE or TEE. Transseptal puncture is not always needed for a PFO — the tunnel is already there. Balloon-size a secundum ASD. Devices are double-disk. Watch residual shunt, device embolization, rare atrial erosion, AF, and device thrombus. Antiplatelet therapy follows implant.

Anatomy and pathophysiology

Fetal circulation uses the foramen ovale so oxygenated placental blood can reach the left heart. After birth, left-atrial pressure rises, the septum primum flap presses against the septum secundum, and the tunnel usually seals. A PFO is failure of that fusion: a probe-patent tunnel, not a punched-out hole. Right-to-left shunting occurs when RA pressure exceeds LA pressure (Valsalva, cough, pulmonary hypertension) — the mechanism of paradoxical embolism.

An ASD is a true congenital communication. Types the R.T.(CI) must name:

• Ostium secundum — fossa ovalis, most common, percutaneous device territory when rims are adequate.
• Ostium primum — endocardial-cushion / AV-canal spectrum, often a cleft mitral valve and a low defect next to the AV valves. Surgical. Do not device-close a primum ASD.
• Sinus venosus — SVC (more common) or IVC insertion, frequently anomalous pulmonary venous return. Surgical.
• Coronary sinus (unroofed) — rare; surgical.

Hemodynamically, a significant ASD is a left-to-right atrial shunt: RV volume overload, RA/RV enlargement, and eventual pulmonary overcirculation. A PFO is usually not a large left-to-right volume shunt; the exam story is paradoxical embolus, not Qp/Qs. An atrial septal aneurysm (hypermobile septum) plus a large PFO shunt is the high-risk PFO morphology that shows up in cryptogenic-stroke teaching.

Indications and contraindications

PFO indication (teaching): secondary prevention after cryptogenic stroke (PFO-associated ischemic stroke) in selected patients once carotid disease, AF, and other sources have been reasonably excluded — typically a younger patient with a high-risk PFO (large shunt, atrial septal aneurysm). Platform-trial language (RESPECT, REDUCE, CLOSE) is how the indication was earned; ARRT is not asking you to recite p-values. Other teaching uses: platypnea-orthodeoxia and selected decompression illness in divers. Migraine is not a default exam indication.

ASD indication (teaching): a secundum defect with RV volume overload, a hemodynamically significant shunt (classic cath teaching often cites Qp/Qs ≳ 1.5:1 — lab teaching, not an unpublished ARRT cutoff), or paradoxical embolism through an ASD. Symptoms include dyspnea, atrial arrhythmias, and reduced exercise capacity.

Contraindications: primum or sinus venosus ASD (send to surgery), inadequate rims for a secundum device (especially a deficient inferior/IVC rim that will not hold a disk), active infection/endocarditis, intracardiac thrombus, and a patient who cannot take the planned antiplatelet regimen. Nickel sensitivity is a relative issue for some nitinol devices. A PFO closed “because we saw bubbles” without a stroke workup is not the indication.

Imaging, access, and ultrasound

Imaging. TEE or ICE is implant-level guidance. ICE is typically a femoral-venous ultrasound catheter in the RA that shows tunnel versus hole, rims, disks as they sandwich the septum, and a pericardial effusion if you perforate. TEE needs an airway plan and often anesthesia. Fluoroscopy watches the delivery sheath and disk release; it does not replace echo rims. A bubble study (agitated saline) diagnoses a PFO: bubbles in the LA within a few beats of RA appearance, especially with Valsalva. After implant, color Doppler and a repeat bubble study look for residual shunt.

Access. Femoral venous is the workhorse. The right femoral vein is the usual path to the IVC, RA, and septum. Arterial access is not required for a straightforward PFO/ASD closure unless the operator wants an arterial line. Transseptal puncture is not always needed for a PFO — you cross the existing tunnel with a catheter and wire. For a secundum ASD you cross the defect. A needle transseptal is used when the tunnel will not admit the sheath or when a separate left-atrial procedure is planned; it is not the default PFO story.

Ultrasound. Vascular ultrasound guides the venous stick and later diagnoses a hematoma or fistula. ICE is the intracardiac ultrasound. Surface TTE can follow residual shunt as an outpatient; it is not the implant-guidance tool.

Equipment: balloon sizing and double-disk devices

Sizing a secundum ASD. A sizing balloon is inflated across the defect until stop-flow (color Doppler through the defect stops, or a waist appears on fluoro). Measure the waist. That diameter, plus echo rims, chooses the device. Do not size a PFO tunnel the same way you size a round ASD hole — PFO devices are chosen for tunnel length and floppy septum, not for a circular tissue gap.

Devices are double-disk (two disks and a connecting waist). ASD occluders (Amplatzer-class septal occluder teaching) have a waist meant to fill the hole. PFO occluders have a slimmer connecting waist for a tunnel. Gore-class (Cardioform) devices are softer, more fabric-forward, and are often discussed when erosion risk of a stiffer disk is the worry. Know the double-disk concept and that device ≠ Watchman (that is LAA, chapter 19) and device ≠ MitraClip. Delivery is a long dedicated sheath from the femoral vein into the LA through the PFO or ASD. Left disk first (LA), pull back to the septum, then right disk (RA), confirm sandwich on ICE/TEE, then release. Heparin while you are left-sided is expected; ACT targets are lab protocol, not an unpublished ARRT second.

Complications, antiplatelet, and closure

Residual shunt: color through or around the device. A tiny residual PFO tunnel leak may close as the device endothelializes; a large residual ASD shunt means malposition, undersizing, or a rim that never held.

Device embolization: the device is no longer on the septum — RA, RV, PA, or left heart. This is a snare and surgical-backup problem. Oversizing that “must hold” on a deficient inferior rim is how you embolize.

Atrial erosion (rare): a stiffer disk, especially near the aortic root or atrial wall, can erode days to years later — tamponade or fistula. Rare does not mean ignore chest pain and effusion after a septal occluder.

Atrial fibrillation: new or recurrent AF after atrial hardware. Thrombus on the device is why antiplatelet therapy is not optional while the disks endothelialize. Typical teaching (protocol-based, not an unpublished ARRT month count): antiplatelet therapy after implant, often dual antiplatelet for a defined early window then aspirin, plus endocarditis precautions per the implanting service. Air embolism during sheath exchanges is the same dry-manifold catastrophe as any left-sided case.

Closure of the access site is venous hemostasis: manual pressure, figure-of-8 stitch, or a venous closure device. This is not an arterial collagen plug unless you also stuck an artery.

Table: PFO versus secundum ASD versus the trap

Worked case

A 42-year-old with ischemic stroke, no AF on monitoring, open arteries, and a TEE that shows a PFO with an atrial septal aneurysm. ICE from the femoral vein. Cross the tunnel — do not start with a transseptal needle. Deploy a double-disk PFO occluder, confirm both disks and no new effusion. Start the lab’s antiplatelet protocol. If the same TEE had shown a primum defect next to a cleft mitral valve, stop: that is surgery, not an ASD occluder. If instead the defect is a round secundum hole with good rims, balloon stop-flow size it, then choose an ASD-waist double-disk — not a PFO tunnel device guessed from one cine frame.

Exam traps

• Device-closing a primum or sinus venosus ASD.
• Treating PFO as a volume-overload Qp/Qs disease.
• Assuming transseptal puncture is mandatory for every PFO.
• Skipping balloon sizing on a secundum ASD.
• Confusing a septal occluder with LAA or mitral-clip hardware.
• Stopping antiplatelets because the stick was venous.