Background: ST-segment elevation myocardial infarctions (STEMI) is a significant cause of morbidity and mortality in the United States. Inter-hospital transfers (IHT) are becoming the standard for treatment of ST-elevation myocardial infarctions (STEMIs) as specialized care is often concentrated at tertiary centers. The American Heart Association and the American College of Cardiology (AHA/ACC) recommends door-to-balloon time within 90 minutes or 120 minutes if transferred.
Methods: We conducted a retrospective study using data from the NCDR and the ACTION Registry for a large, PCI capable academic medical center in central Texas. There were 268 patients that met these criteria who had an inter-hospital transfer for a STEMI between January 1, 2012 to December 31, 2017. All statistical analysis was performed in SAS 9.4.
Results: A univariate logistic regression with a set p-value of <0.25 was used to assess which variables should be considered in the multivariate logistic regression model for mortality: LDL (p=0.0469), HDL (p=0.1856), TC (p=0.1903), smoking status (p=0.0344), dialysis (p=0.1989), prior CABG (p=0.0597), prior PAD (p=0.0552), and P2Y12 inhibitor (<0.0001) met this criteria. Model selection methods were used to identify the final multivariate logistic regression model and found only LDL and P2Y12 inhibitor (defined as those that presented or were discharged with a P2Y12 inhibitor including clopidogrel, ticagrelor, and prasugrel) to be statistically significant predictors of mortality. This model’s c-statistic of 0.981 indicated that this model did a significantly better job predicting death than chance (c-statistic 0.50). Comparing patients with the same LDL value, the odds of death for those without a P2Y12 inhibitor are 99.7% higher than the odds for those who do have a P2Y12 inhibitor.
Conclusions: AMI remains a major cause of morbidity and mortality in the United States despite significant advancement in detection and treatment. In our study, no significant difference was noted in mortality between transferred and non-transferred patients, despite a significant number of patient deaths (9% or 7 of 72 transferred and 6% or 12 of 196 non-transferred patients). This was an unexpected result as transfers generally result in increased total ischemic time in STEMI patients. These positive results are likely a result of highly efficient transfer times of the transferred patients. Amongst, all the variables extracted from the NCDR/ACTION registry, only LDL and P2Y12 inhibitor were predictors of mortality with almost a perfect c-statistic of 0.981. P2Y12 inhibitors were routinely given post-PCI unless otherwise contraindicated. In conclusion, we found that LDL level and appropriate utilization of P2Y12 are excellent in hospital mortality predictors of STEMI patients.