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					PATENT FORAMEN OVALE
Beauty Spot or Health Threat

         Lindsay Morrison
 Cardiothoracic Centre - Liverpool
   Royal College of Physicians
             22.3.02
Diagram and Description of PFO
• A patent foramen ovale (PFO) is a persistent, usually
  flap like opening between the left sided atrial septum
  primum and the right sided secundum at the location
  of the fossa ovalis.
• In utero, the foramen ovale serves as a physiological
  conduit for right-to-left shunting.
• After birth, with the establishment of pulmonary
  circulation, the increased left atrial blood flow and
  pressure results in functional closure of the foramen
  ovale.
• This functional closure is subsequently followed by
  anatomical closure of the septum primum and
  septum secundum.
          PFO - Incidence
• Probe-patent foramen ovale shown to
  persist in up to 25-35% of adults at autopsy.
• PFO detected in vivo in 5-20% of adults
  using contrast echo.
• Most PFO’s are small, but 1-3% of the
  population have a PFO that is 1cm diameter
  or larger, which are clinically relevant
           PFO - Detection
• Echocardiogram - TTE
                 - TOE +/- PROVOCATIVE
                              MANOEUVRES
                    - contrast studies
• Cardiac Catheterisation
A PFO cannot be detected by
physical examination.
     PFO’s and Paradoxical Embolism
1.   Phenomenon of paradoxical embolism in presence
     of a PFO was first described by Cohnheim in 1877.
2.   Paradoxical embolism is thought to be responsible
     for an embolic event in:
     a) the absence of a left-sided thrombo-embolic
        source.
     b) the potential for right-to-left shunting and
     c) the detection of thrombus in the venous system
        or right atrium.
3.   The diagnosis of paradoxical embolism is usually
     presumptive.
 PFO and Paradoxical Embolism
The mechanisms for a PFO to mediate
paradoxical embolism are believed to be:
 1) a chronic elevation of right atrial pressure eg
    pulmonary hypertension, COPD, pulmonary
    embolism.
 2) a transient elevation of right atrial pressure after
    release of positive airway pressure (valsalva, cough,
    diving)
 3) Cyclical pressure differences between the atria with
    transient right-to-left shunt.
PFO and Paradoxical Embolism
  A PFO may be especially dangerous during surgical
  interventions that are prone to embolisation into the
  venous system of:

• fat (orthopaedic surgery)
• air (neurosurgery, cardiac surgery)
Consequences of right-to-left shunting and
    paradoxical thrombo-embolism

 -   Stroke
 -   decompression illness (gas embolism)
 -   arterial hypoxaemia
 -   migraine with aura
 -   transient global amnesia
Show fig.6 on migraine and PFO from
    Cardiology Rounds Paper
            PFO and Stroke
• Estimated 750,000 strokes per year in USA
  with a mortability of 25%
• Third leading cause of death behind heart
  disease and cancer
• 80% of strokes are ischaemic
• Cryptogenic stroke accounts for around 40%
  in younger patients
              PFO and Stroke
– Paradoxical embolism via a PFO should be
  entertained in the differential diagnosis, especially
  patients under 55 years with cryptogenic stroke.
– The average prevalence of PFO in patients under 55
  years with cryptogenic stroke is around 50%,
– Currently there is no proof for a cause-effect
  relationship, however
– several studies have confirmed a strong association
  between the presence of a PFO and the risk of
  paradoxical embolism or stroke.
             PFO and Stroke
When compared with control subjects, the relative risk
of suffering a thrombo-embolic event is four times as
high in patients with PFO, and 33 times as high with
both PFO and an atrial septal aneurysm.

(an atrial septal aneurysm is formed by a flimsy and
redundant septum primum)
Prevention of thrombo-embolic
        complications
-   Antiplatelet therapy
-   Warfarin
-   Surgery
-   Device closure
Stroke Recurrence rate and PFO
Table 2 Cardiology rounds paper
• Percutaneous closure of PFOs
• Non surgical closure of PFOs; became possible with
  advent of umbrella devices, initially developed for
  closure of ASDs.
• Devices include: Sideris buttoned device
                   Sideris self-centering device
                   Angel wings device
                   Cardioseal device
                   Amplatzer occluder
         Device closure of PFO:
         Where is the Evidence?
• While there is good evidence for an association between
  the presence of PFO and the risk for paradoxical
  embolism, a cause-effect relationship has not been
  conclusively established.
• There are no comparative trials comparing medical
  treatment (anti coagulant and antiplatelet treatment),
  with device closure
• There is an ongoing trial comparing the efficacy of
  percutaneous PFO closure with medical treatment with
  presumed paradoxical embolism.
       Amplatzer Septal Occluder

•   Self expandable, double disc device
•   Nitinol (Nickel-titanium Alloy)
•   Two discs linked together by a short waist
•   Discs and waist filled with polyester
    patches.
               Technique
General anaesthesia
TOE guidance
Access: Right Femoral Vein
Multipurpose Catheter to cross PFO
0.035 inch exchange wire
Balloon sizing of PFO
Heparin 5000 IU
Antibiotic
Delivery Catheter
Amplatzer PFO Device
  Indications for Closure of PFO
• History of unequivocal and unexplained systemic
  embolism
• Non-paradoxical source of embolism excluded by
              ultrasound of cerebral arteries
              echocardiogram
              24 hour tape
              screening for hypercoagulability syndromes
• PFO documented by echocardiogram
PFO Clinical Results - Device Closure
250 consecutive patients in Swiss Study
• Rate of recurrent TIA’s or peripheral
  embolism 1.6% per year
• Mortality Rate 0%
• CVA 0%
• Occasional residual leak
• Complete closure fares better than
  incomplete
     PFO Device - Aftercare
• Aspirin for 6 months

• Clopidogrel for 4 weeks

• Antibiotic prophylaxis for 6 months
PFO Clinical Results - Device Closure
Comparison with a control group treated
medically (non-randomised)
 – Lower incidence of recurrent events after two
   years
 – No major strokes v 2.3% per year medically
   treated group
 – Significant advantage for patients with two or
   more prior events, and for those with
   complete closure.
PFO: Does size matter?
               Summary
• Clearly, a PFO can have clinical importance
• Risk of paradoxical embolism increases with age
• Paradoxical embolism may recur
• Randomised clinical trial is at present ongoing
• Current matched and unmatched comparisons
  with conventional treatment and device closure
  appears to favour PFO closure.
• Closure yields better results if it is complete
• Surgical closure can be kept in reserve.

				
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