ISCHEMIC STROKE / PREVENTION
Patent foramen ovale (PFO)
Created 25/01/2023, last revision 04/02/2023
- before birth, the atrial septum is formed by two leaves. After birth, the pressure rises in the left atrium and the two leaves fuse
- in 1/3 of people, the leaves do not fuse, and a different-sized opening called the patent foramen ovale (PFO) or foramen ovale apertum (FOA) persist
- PFO causes a right-to-left shunt – blood can flow from the right atrium directly into the left atrium, bypassing the pulmonary circulation
- various particles in the blood can bypass pulmonary circulation together with the blood and enter systemic circulation (paradoxical embolism)
- small clots released from the veins of the lower limbs and pelvis
- gas bubbles (formed during fast decompression in scuba divers or administered via IV injections)
- certain hormones (serotonin in migraine with aura?)
- PFO alone does not cause hemodynamic problems
- PFO is not the only cause of right-to-left shunt:
- intracardiac shunts (90%) – patent foramen ovale (PFO), atrial septal defects
- extracardiac shunts (10%) – mostly pulmonary AV shunts
- combination of extra- and intracardiac shunts is possible
PFO and cryptogenic stroke
PFO and cryptogenic stroke- patent foramen ovale (PFO) is associated with cryptogenic stroke (CS), though the pathogenicity of a discovered PFO in the setting of CS is typically unclear
- the prevalence of PFO is about 25% in the general population and up to 46% in patients with CS
- PFO is occasionally associated with the following:
- atrial septal aneurysm (ASA) / hypermobile atrial septum – defined as excursion ≥ 10-15 mm from the midline
- atrial septal defect
- atrial septal aneurysm (ASA) / hypermobile atrial septum – defined as excursion ≥ 10-15 mm from the midline
- PFO-related stroke mechanisms:
- paradoxical embolization from peripheral veins
- embolization of a thrombus formed directly within the PFO channel
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Diagnostic evaluation
PFO detection
Contrast-enhanced transesophageal echocardiography (cTEE)
- 2D or 3D + bubble test – sensitivity and specificity between 89-95%
- information on the shape and size of the PFO and associated pathologies (ASA, septal hypermobility, LAA thrombus, etc.)
- disadvantages:
- invasive nature of the procedure; some patients do not tolerate it
- a lower sensitivity for small PFOs
TCD/TCCD bubble test
- non-invasive screening method → see here
- detects all right-to-left shunts (cardiac and extracardiac)
- sensitivity and specificity are reported over 90%
Cardiac CT/MRI
- can be performed in patients who cannot tolerate TEE
- provides information on potential thrombi and other pathology
- may also be useful for monitoring PFO occlusion
Other methods
Doppler ultrasound / MR venography
- detection of a possible source of emboli in the pelvic and lower limbs veins
D-dimers
- normal levels: 0.068-0.494 mg/L
- level <0.5 mg/l makes DVT unlikely but not impossible
- false-positive results are common
Management
- primary prevention: PFO closure is not indicated
- secondary prevention: consider antiplatelet or anticoagulant therapy and PFO closure
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PFO and migraine
- a higher prevalence of PFO has been reported in patients with migraine with aura than in patients with migraine without aura or patients without migraine (48% vs. 23% and 20%, respectively).
- the causal association remains unclear
- some small non-randomized trials have reported a reduced incidence of migraine after PFO closure
- randomized trials MIST (Starfix, 2016) and PREMIUM (Amplatzer, 2017) did not show a preventive effect
