Fig. 6.1
Cartoon schematic of the foetal circulation. There are two shunts that provide shortcuts for most of the pulmonary circulation system (circled in green). Connection between the right and left atria via the foramen ovale. Connection between the truncus pulmonalis and the aorta via the ductus arteriosus
PFOs have been linked with several different conditions, cryptogenic cerebrovascular accidents (CVA) being the most reported. There are also suggested associations with decompression sickness (DCS), paradoxical embolization and migraine. The incidence of PFO in cryptogenic CVA is as high as 40 %, predominantly via paradoxical emboli, specifically thrombi from the venous circulation into the arterial circulation. Many people with PFO remain asymptomatic and the defect is found after specific investigations are undertaken to look for aetiology of a systemic complication. The most commonly employed imaging modality is transthoracic echocardiography (TTE) with agitated saline solution – “Bubble Contrast Echocardiogram”. The defect can then be further investigated with transoesophageal echocardiography (TOE) and cardiovascular magnetic resonance (CMR) to further assess cardiac structure and calculate degree of shunt, avoiding the need for right heart catheterization.
PFO defects can be closed surgically or using a percutaneous device. Due to the associated morbidity, surgical closure is chosen for individuals with other cardiac defects requiring operative intervention. One example of a percutaneous PFO closure device is the AmplatzerTM PFO Occluder (St Jude Medical Inc; Fig. 6.2). Other devices include the AmplatzerTM Septal Occluder (St Jude Medical Inc) and Helex® Septal Occluder (WL GORE, Newark, DE), which are predominantly used in atrial septal defect closure (Fig. 6.3).
Fig. 6.2
St Jude AmplatzerTM PFO Occluder. This is a self-expandable, double disc device made from a nitinol wire mesh and thin polyester fabric. The two discs are linked together by a short, connecting waist which allows free motion of each disc (Amplatzer and St. Jude Medical are trademarks of St. Jude Medical, Inc. or its related companies. Reproduced with permission of St. Jude Medical, © 2016. All rights reserved)
Fig. 6.3
Helex® Septal Occluder (WL GORE, Newark, DE). (a) Occluder and the delivery system. The occluder is designed as a single piece of ePTFE attached throughout its length to a nitinol frame wire. This leaves very little metal exposed to bloodstream (From Circulation. 2001;104: 711–6.)
Case Study
A 29 year old male was referred to our tertiary cardiac intervention centre for consideration of percutaneous PFO closure. His had presented to his local cardiology department with dizziness and headache in combination with right sided upper and lower limb weakness. Following a diagnosis of CVA, a series of investigations were undertaken to establish an aetiology. Routine haematological and biochemical investigations were unremarkable. Thrombophilia and auto-immune screens were negative. Computed tomography angiogram of his neck and cerebral vessels did not demonstrate dissection or other significant pathology. Brain magnetic resonance imaging (MRI) demonstrated multiple areas of infarction in the left posterior cerebral artery territory. Twenty-four hour holter monitor recorded sinus rhythm throughout with no paroxysmal arrhythmia. A TTE study was undertaken, baseline images demonstrated an aneurysmal inter-atrial septum and bubble contrast echocardiography was performed. At rest, no bubbles were seen to cross the septum but following Valsalva, bubbles were clearly evident within the left atrium, suggestive of a clinically significant PFO.
PFO closure was performed under conscious sedation using a combination of midazolam and fentanyl with antibiotic and anticoagulant cover. Local anaesthetic was administered to the right groin and sequential punctures of the femoral vein were performed. Two sheaths were inserted into the femoral vein (6 French [6 F] and 8 French [8 F]). Via the 6 F sheath, a multi-purpose A2 (MP-A2) catheters was passed on a standard length (150 cm) J tip wire. The 8 F sheath was used to pass an intracardiac echocardiogaphy (ICE) device up to the right atrium. With the ICE catheter in place, an on-table contrast study was performed, confirming the presence of an aneurysmal inter-atrial septum and septal defect following intermittent increases in right heart pressures (Video 6.1; Fig. 6.4a, b). The MP-A2 catheter was then used to cross the defect and cannulate the left upper pulmonary vein (Video 6.2; Fig. 6.5). Using a long exchange wire (260 cm straight tip) an 8 F TorqVueTM delivery system was placed in the left atrium. A 25 mm AmplatzerTM PFO Occluder was deployed into the left atrium and pulled into position under both echocardiography and fluoroscopy guidance (Video 6.3a, b; Fig. 6.6). Stability of the occluder was confirmed (Video 6.4 – Fluoroscopy) and once the operator was satisfied with its position, the device was released from the delivery shaft (Video 6.5 – Fluoroscopy). A final fluoroscopy image was acquired with the device in situ (Video 6.6; Fig. 6.7) and a final ICE image was obtained with colour flow Doppler across the occlusion device to demonstrate no residual shunt immediately post deployment (Video 6.7; Fig. 6.8). All the equipment was then removed and manual pressure was applied to achieve haemostasis.
