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.