Ticagrelor pretreatment and angiographic no-reflow in STEMI: a multicentre observational study

We examined the association between ticagrelor pretreatment and angiographic no-reflow in ST-segment elevation myocardial infarction (STEMI), with in-hospital mortality as a secondary outcome and clinical phenotyping as an exploratory objective. In a retrospective multicentre registry (2018-2021), 623 patients referred for percutaneous coronary intervention were compared by loading strategy: pretreatment at first medical contact or deferred before PCI. Cohort-wide inverse probability of treatment weighting (IPTW), using a clinical covariate-balancing propensity model and 50 imputations, estimated adjusted risk ratios (RRs). Outcome-blind latent class analysis preceded a treatment-weighted comparison of class-specific no-reflow risks. No-reflow occurred in 28/464 pretreated patients versus 27/159 comparators (6.0% versus 17.0%); the crude RR was 0.36 (95% CI 0.22-0.58), and the IPTW-adjusted RR was 0.43 (95% CI 0.24-0.74; P = 0.003). Ten patients died (adjusted RR 0.46, 95% CI 0.13-1.67). Three classes comprised 328, 231 and 64 patients, but their pretreatment-standardised no-reflow risks did not establish prognostic separation. Ticagrelor pretreatment was associated with lower angiographic no-reflow after propensity weighting. The adjusted mortality and exploratory class-risk findings did not reach statistical significance. Residual confounding and uncertain covariate timing limit causal interpretation, and prospective validation is required.