CARDIOVASCULAR JOURNAL OF AFRICA • Volume 34, No 1, January–April 2023 36 AFRICA It is highly recommended that the above work-up of a stroke is done in conjunction with disciplines that have the relevant expertise, such as neurology, radiology and haematology. If these investigations yield a probable cause, it is less likely that the cause of the embolism was a PFO. The decision to proceed with further PFO work-up with a view to closure will then depend on the assessment of the likelihood that an event is PFO related. What is the likelihood that a stroke is related to a PFO? The risk of paradoxical embolism (RoPE) score and some other clinical variables are helpful to assist in this decision. The RoPE score (Table 2) is a useful tool to determine the likelihood that a stroke of unknown cause is related to a PFO.4 The maximum number of points scored is 10. The likelihood that a PFO is the cause of a cryptogenic stroke for a RoPE score of seven, eight and nine to 10 is 72, 84 and 88%, respectively. Additional findings that strengthen the case for a PFO to be the cause of the stroke are: • Presence of an atrial septal aneurysm (protrusion of atrial septum at least 15 mm beyond level surface of atrial septum). • Presence of Eustachian valve or Chiari network.5,6 • Hypermobility of atrial septum (phasic septal excursion into either atrium > 10 mm). • Large right-to-left shunt (large PFO = maximum separation of the septum primum from secundum during Valsalva manoeuvre > 2 mm). • Documentation of a venous source of thrombus (pulmonary embolus or deep venous thrombosis). • Activity at the time of stroke: straining, Valsalva manoeuvre. How is a PFO diagnosed? In order to detect the presence of a PFO, a reasonable initial screening test is a transthoracic echocardiogram (TTE). A bubble study with agitated saline and timely Valsalva manoeuvre must be performed to detect the presence of a right-to-left shunt. Without adequate Valsalva (specifically, hold Valsalva on bubble entry, septum moves to the right; release Valsalva and septum bulges to the left), up to 20% of PFOs are missed.7 The sensitivity of TTE to detect a PFO is very variable depending on the quality of the study that can be performed (Fig. 1).8 There is frequently diagnostic uncertainty after TTE and for this reason a transoesophageal echocardiogram (TOE) is recommended either ab initio or if the TTE is negative. A TOE provides better visualisation of the interatrial septum and colour Doppler evaluation for flow across it. The sensitivity and specificity of TOE with a bubble study to detect a PFO is 89 and 91%, respectively.9 Contrast-enhanced transcranial Doppler ultrasound is a further useful screening tool to detect a possible PFO, as well as extracardiac right-to-left shunts. Its usefulness depends on operator experience and this modality is not widely available in South Africa.10,11 Regardless of the imaging modality used to confirm the presence of a PFO, a TOE is recommended to define the precise anatomy to plan the closure. This includes the size and location of the PFO, the site of the PFO in relation to its surrounding structures, atrial septal anatomy [especially the presence of an Table 2. The RoPE score Characteristics Points No history of hypertension 1 No history of diabetes mellitus 1 No history of stroke or TIA 1 Non-smoker 1 Imaging shows cortical infarct 1 Age (years) 18–29 5 30–39 4 40–49 3 50–59 2 60–69 1 > 70 0 TIA, transient ischaemic attack. Signs and symptoms of CVA on history and clinical examination Multidisciplinary team discussion Radiology and neurologist consultation Other specialists if needed Imaging interventional cardiologist and cardiothoracic surgeon consultation Confirm with CT scan of the brain or MRI evidence of ischaemic CVA Determine aetiology of CVA Carotid artery occlusion/stenosis Atherosclerotic plaque/ dissection in the aorta extending into great vessels Auto-immune antibody and hypercoagulability screen Atrial fibrillation Other cardioembolic source Lacunar stroke No obvious aetiology found Assess for PFO Only indicated if further information needed after TTE/TOE examination or TOE contraindicated A PFO ± ASA confirmed on bubble study with adequate Valsalva manoeuvre and PFO likely cause of stroke (RoPE score) Consider PFO closure particularly in patients < 60 years or recurrent cryptogenic stroke Cardiac CT/MRI TOE TTE Fig. 1. Diagnostic algorithm for assessment and management of a patient with acute cryptogenic stroke and patent foramen ovale. PFO, patent foramen ovale; CVA, cerebrovascular accident; CT, computed tomography; MRI, magnetic resonance imaging; TTE, transthoracic echocardiology; TOE, transoesophageal echocardiography; ASA, atrial septal aneurysm.
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