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Background Transthoracic echocardiography (TTE) with bubble study remains the first-line investigation for patent foramen ovale (PFO) detection, despite limitations in sensitivity (73–85%) compared to transoesophageal echocardiography with bubble contrast. We evaluated real-world performance, focusing on indication appropriateness, diagnostic accuracy, and clinical outcome.Methods All TTE bubble studies performed in adults ≤65 years between June 2023 and July 2024 were retrospectively analysed. Referral forms were cross-referenced with clinical records to validate indication appropriateness. Two BSE-accredited echocardiographers independently reclassified negative studies as true negative, positive (>5 bubbles in the left ventricle within 5 cardiac cycles), or equivocal (incomplete storage, absent Valsalva despite interatrial septal movement, or <5 bubbles). Clinical data, including RoPE scores and PFO closure decisions, were extracted from electronic records.Results Ninety-five unique TTE bubble studies were analysed. Of these, 46 (48%) were appropriate referrals, while 49 (52%) were inappropriate; most inappropriate cases had an alternative stroke aetiology ( table 1). Thirteen studies (14%) were performed before infarct confirmation, representing premature investigation.Thirty-seven of the 46 appropriately indicated studies were initially reported as negative and were reviewed. Three were reclassified as positive and 5 as equivocal, leaving 29 confirmed negative.Of the 37 initially reported negative, 4 (10.8%) proceeded to further evaluation with TOE, 2 from the reclassified equivocal group and 2 from the reclassified positive group. Three of these 4 proceeded to closure. Reasons for non-closure and not proceeding to TOE are summarised in figure 1.Of the 12 patients with confirmed PFO, 8 were identified on initial TTE bubble study, whereas 4 required further evaluation with TOE before confirmation.Conclusions This study demonstrates that, when used in the appropriate clinical context, TTE bubble study is a suitable first-line investigation for PFO detection. Following expert review, only 10.8% of cases required further evaluation with TOE. However, more than half of referrals were inappropriate, with some performed prematurely. These findings highlight the need for stricter referral triage to optimise resource use and ensure appropriate patient selection.Abstract 85 Table 1Referral indications for TTE bubble studies (N=95) Category Indication subtype n % of total Appropriate Indication≤60 years old cryptogenic stroke with confirmed infarction3942%Platypneoa Orthodeoxia / Hepatopulmonary Syndrome22%Systemic embolism55%Inappropriate Indication>60 years old stroke, RoPE Score <71415%Large-vessel disease (carotid/vertebral)1818%TIA without infarction on MRI66%Haemorrhagic Stroke33%Intracranial mass22%Other/No clear indication66%Abstract 85 Figure 1