This study evaluated the most effective strategy for delivering extracorporeal cardiopulmonary resuscitation (ECPR) in refractory out-of-hospital cardiac arrest (OHCA) within a dense urban emergency system using Monte Carlo simulations. Investigators applied 2,000 geospatial simulations using 2-15-2019 OHCA data from a single metropolitan EMS based in Montreal (~1,240 cases/iteration) to compare six ECPR strategies: in hospital (2,3, 4 sites), a rendezvous team, and two prehospital teams (hospital based, optimally located). Eligibility required witnessed arrest, bystander CPR, and age ≤70 years, yielding 255 eligible OHCA cases per iteration. Simulations evaluated survival with favorable neurological status at 6 months (CPC 1–2), the proportion achieving flow recovery ≤60 minutes (ROSC or ECMO), and low flow time. Expanding in-hospital sites from 2 to 4 increased CPC 1–2 from 25.3% (95% CI 25.2-25.4) to 28.0% (27.9-28.1)–about 65 to 71 cases in the 255 iteration–and increased flow ≤60 minutes from 69.2% (69.1-69.3) to 75.1% (75.0-75.3). Low flow was reduced by ~2.4 minutes. The rendezvous model achieved 28.8% (28.7-29.0) CPC 1–2 and 77.3% (77.1-77.4) ≤60 minutes flow, with ~2.9 minutes less low flow. Prehospital strategies produced the largest gains: the hospital-based team achieved 39.5% (39.3-39.6) CPC 1–2 and 99.7% (99.6-99.7) flow, with ~7.8 minutes less low flow,while the optimally located team achieved 42.0% (41.8-42.1) CPC 1–2 and 100.0% flow, with ~12.0 minutes less low-flow. These findings suggest prehospital teams could increase equitable access to sub-60-minute ECPR in urban settings, if staffing and mobile ECMO resources are available.