Did inter-hospital transfer reduce mortality in patients with acute myocardial infarction in the real world? A nationwide patient cohort study

Introduction: Inter-hospital transfer (IHT) and primary percutaneous coronary intervention (PCI) are preferred over onsite thrombolysis when provided expeditiously. On the other hand, its benefit has not been evaluated in a real-world situation. This study examined the effects of IHT on the short- and long-term mortality in patients with acute myocardial infarction (AMI) and compared the reperfusion treatments and resources between the referring and receiving hospitals. Methods: Patients newly diagnosed with AMI and admitted to hospital were selected from the national health insurance database from 2004 to 2018. The 30-day and one-year mortality in the transferred and non-transferred patients were estimated and compared using stabilized inverse probability of treatment weighting to account for confounding bias. Results: Of the 258,291 participants, 10,158 were transferred to one or more hospitals. IHT was more likely to occur to older or more comorbid people, patients in rural areas, and those whose insurance was medical aid. The 30-day and one-year mortality of the non-IHT group was 9.7% and 15.8%, respectively, whereas the figure was 11.4% and 20.5% in the IHT group. After balancing the baseline characteristics, the transferred patients were 1.12 (95% CI: 1.06–1.20) and 1.25 (95% CI: 1.20–1.31) times more likely to die during the subsequent 30 days and one year, respectively, than those treated solely at the presenting hospital. In ST-segment elevation myocardial infarction (STEMI), the hazard ratios of the 30-day and 1-year mortality were 1.14 (95% CI: 0.97–1.35) and 1.31 (95% CI: 1.15–1.49) in the transferred patients after balancing cardiogenic shock and cardiac arrest. On-site thrombolysis was rarely performed in the referring hospitals. Conclusion: Patients transferred for the treatment of AMI experienced higher short- and long-term mortality. Therefore, onsite thrombolysis and the estimated time delay to PCI should be considered in regional hospitals to reduce mortality with the organization of STEMI treatment networks.