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Introduction Whilst Primary Percutaneous Coronary Intervention (PPCI) is the preferred reperfusion strategy for ST-elevation myocardial infarction (STEMI), thrombolytic therapy is a class Ia guideline-recommended therapy when PCI cannot be delivered within 120 minutes. Our centre serves 2.5 million people across 46,000km 2, including remote areas where thrombolysis remains a crucial therapeutic option. Although door-to-balloon times are often reported, pain-to-balloon times are lengthening due to emergency service pressures. With this in mind, we audited patient characteristics, lysis timings and transfer metrics, and safety across our lysis cohort, in which contemporary acute coronary syndrome (ACS) pharmacology and PCI techniques were utilised.Methods Retrospective cohort study of consecutive STEMI patients receiving thrombolysis (January 2018-January 2020) who underwent subsequent PCI as part of a pharmacoinvasive strategy. Baseline characteristics, lysis/transfer metrics, safety, and long-term outcomes were assessed. Procedural and revascularisation data were compared between those achieving successful clinical reperfusion, defined as ≥50% ST-segment elevation resolution 90 minutes after lysis, and those who did not.Results Eighty patients were identified (age 63±10 years, 71% male), with characteristics as shown in table 1. 89% presented within 6 hours of symptom onset. A DANCAMI score ≥ 4 and an SCAI stage of cardiogenic shock D-E were seen in 21 (26%) and 9 (11%), respectively, indicating a multimorbid population with a high incidence of shock. Time and distance metrics according to different catchment areas are summarised in figure 1. Median lysis-to-tertiary-centre distance was 142km (IQR 137-307), 60% required air transfer, and 69% achieved clinical reperfusion at 90 minutes. Time from lysis to catheterisation was longer in patients with clinical reperfusion (673 vs 206 minutes, p=0.002), reflecting a routine early-invasive versus emergent rescue strategy. Initial TIMI 3 flow (table 2) was strongly associated with ST-resolution (71% vs 17%, p<0.001). However, final TIMI 3 flow grade following intervention did not differ (92% vs 78%, p=0.12). Thrombus aspiration and GPIIbIIIA infusions were more commonly deployed in cases that failed to clinically reperfuse (17% vs 9.6%, p=0.4). There were 3 TIMI major bleeding events (2 overt haemorrhage and 1 haemorrhagic stroke) and 5 inpatient deaths (3 cardiogenic shock, 1 hypoxic brain injury, and 1 haemorrhagic stroke).Conclusions This cohort is multimorbid, with a higher incidence of shock compared with a typical STEMI cohort, suggesting that lysis decision-making reflected not only patient location but also the urgency to reperfuse. Despite this high-risk subgroup, we show that lysis is effective and safe, with over two-thirds achieving TIMI 3 flow at initial angiography at a cost of major bleeding in less than 5%. With system pressures increasing, clinicians are reminded that thrombolysis remains appropriate for STEMI when timely transfer to PCI-capable centres is uncertain.Abstract 512 Table 1Demographics & outcomesCharacteristicN = 801Age63 (±10)Male57 (71%)Anterior STEMI.31 (39%)DANCAMI score: Mod-severe burden (≥4)21 (26%)SCAI sgage C-E at transfer9 (11%)Tenecteplase dose/weight ratio (unit/kg, n=52))105 (±10);Missing: 28Time from onset to thrombolysis (mins)160 (108, 275)Time from thrombolysis to tertiary centre (mins)217 (141, 310)Estimated distance of travel (km)142 (137, 307)Transfer by air48 (60%)1Mean (±SD); n (%); Median (Q1, Q3)Abstract 512 Table 2Comparison according to the initial TIMI flow grade ≥50% ST elevation resolution at 90 minutes CharacteristicNo N = 231Yes N = 521p-value2Time from thrombolysis to cath lab (mins)206 (218, 315)673 (241, 1,229)0.002LMWH administered within 30 minutes of lysis2 (10%); Missing: 38 (17%); Missing: 60.7Revascularisation strategy 0.042 DES18 (78%)49 (94%) DEB/POBA4 (17%)1 (1.9%) Initial TIMI 3 flow in culprit vessel4 (17%)37 (71%)<0.001TIMI 3 flow at final angiography18 (78%)48 (92%)0.12Adjunctive therapy used (thrombus aspirationor GPIIb/IIIa inhibitor4 (17%)5 (9.6%)0.4TIMI Major bleeding event3 (3.8%)5-year MACE; 5-year mortality20 (20%); 12 (15%)1n (%); Median (Q1, Q3)2Pearson’s Chi-squared test; Wilcoxon rank sum test; Fisher’s exact testAbstract 512 Figure 1Illustration of catchment area and associated time metrics