Long-term Mortality Following Interhospital Transfer for AMI
Background Interhospital transfer of patients admitted with an acute myocardial infarction for specialised care is common and costly. However, the long-term mortality of transferred patients compared with patients solely treated at the presenting hospital has not been evaluated. Here, we assess the long-term mortality of patients who undergo interhospital transfer during their acute myocardial infarction admission.
Methods We evaluated 40 482 patients with a ICD10-AM diagnosis of acute myocardial infarction admitted to hospitals in New South Wales, Australia, from 2004 to 2008, of whom 10 107 (25%) were transferred. We compared in-hospital and mortality up to 5.5 years postdischarge among transferred and non-transferred patients. We created a 1:1 propensity score matched cohort (n=16 854; 8427 per group) to account for selection bias.
Results In the matched cohort, transferred patients were more likely to undergo revascularisation (55.6% vs 13.7%, RR 4.05; 95% CI 3.83 to 4.29) and had lower mortality at 30 days (3.5% vs 5.7%, HR 0.60; 95% CI 0.52 to 0.70), 1 year (7.5% vs 12.6%, HR 0.58; 95% CI 0.52 to 0.64) and at the end of follow-up (15.3% vs 22.5%, HR 0.65; 95% CI 0.61 to 0.70) than patients treated in presenting hospitals. With the exception of transfers originating from revascularisation capable hospitals, these findings were consistent across a range of subgroups, including patients of all ages, ST-elevation myocardial infarction and non ST-elevation myocardial infarction patients, and transfers originating from hospitals in regional and major city areas. Sensitivity analyses showed that these findings are unlikely to be due to survival bias or to confounding by unmeasured variables.
Conclusions Patients hospitalised for an acute myocardial infarction who are transferred to one or more hospitals for specialised care have higher rates of coronary revascularisation and experience lower long-term mortality.
Interhospital transfer (IHT) of patients hospitalised for acute myocardial infarction (AMI) is common in contemporary AMI care. Indeed, 28%–45% of patients hospitalised for AMI are now transferred to another hospital during their AMI event with practice driven by clinical guidelines that suggest patients with AMI benefit from highly specialised services and interventions, most notably early coronary angiography and revascularisation by percutaneous coronary intervention (PCI). These specialised services are not universally available among hospitals, and IHT is the primary means for accessing these services for many hospitalised patients with AMI.
Recent observations, however, have questioned whether IHT leads to improved patient outcomes. Prior studies have shown that transferred AMI patients have a lower risk profile compared with non-transferred patients. This observation has raised concerns that patients who undergo IHT may not necessarily have improved outcomes from such intervention because high risk patients generally derive greater benefit from specialized care such as PCI. However, the absolute risk profile and outcomes of transferred patients have not been previously described. Furthermore, a recent US study showed no difference in hospital level, risk-standardised 30-day mortality between hospitals with a high versus low transfer rate for patients with AMI. While this was a hospital-level rather than a patient-level analysis, it nevertheless suggested that transfer was not beneficial as an intervention in AMI care to improve patient outcomes.
Existing observational studies of transferred patients with AMI have limited ability to address these concerns. Although many studies have evaluated emergent transfer of ST-elevation myocardial infarction (STEMI) patients, relatively few have evaluated transfer of admitted patients, most of whom have a non-ST-elevation myocardial infarction (NSTEMI), and who are further along in their illness. The few studies that have evaluated admitted patients report lower 30-day mortality among transferred patients, yet these studies are often from selected populations and rarely report risk-adjusted outcomes. Most importantly, prior studies have not reported long-term patient mortality.
Accordingly, we assessed whether hospitalised patients with AMI who are transferred for specialised care during their AMI event have lower long-term mortality compared with similar patients solely treated at the presenting hospital using data from a large population cohort from Australia. We specifically sought to assess patient mortality based on the risk profile of transferred patients and the consistency of findings among various population subgroups.
Abstract and Introduction
Abstract
Background Interhospital transfer of patients admitted with an acute myocardial infarction for specialised care is common and costly. However, the long-term mortality of transferred patients compared with patients solely treated at the presenting hospital has not been evaluated. Here, we assess the long-term mortality of patients who undergo interhospital transfer during their acute myocardial infarction admission.
Methods We evaluated 40 482 patients with a ICD10-AM diagnosis of acute myocardial infarction admitted to hospitals in New South Wales, Australia, from 2004 to 2008, of whom 10 107 (25%) were transferred. We compared in-hospital and mortality up to 5.5 years postdischarge among transferred and non-transferred patients. We created a 1:1 propensity score matched cohort (n=16 854; 8427 per group) to account for selection bias.
Results In the matched cohort, transferred patients were more likely to undergo revascularisation (55.6% vs 13.7%, RR 4.05; 95% CI 3.83 to 4.29) and had lower mortality at 30 days (3.5% vs 5.7%, HR 0.60; 95% CI 0.52 to 0.70), 1 year (7.5% vs 12.6%, HR 0.58; 95% CI 0.52 to 0.64) and at the end of follow-up (15.3% vs 22.5%, HR 0.65; 95% CI 0.61 to 0.70) than patients treated in presenting hospitals. With the exception of transfers originating from revascularisation capable hospitals, these findings were consistent across a range of subgroups, including patients of all ages, ST-elevation myocardial infarction and non ST-elevation myocardial infarction patients, and transfers originating from hospitals in regional and major city areas. Sensitivity analyses showed that these findings are unlikely to be due to survival bias or to confounding by unmeasured variables.
Conclusions Patients hospitalised for an acute myocardial infarction who are transferred to one or more hospitals for specialised care have higher rates of coronary revascularisation and experience lower long-term mortality.
Introduction
Interhospital transfer (IHT) of patients hospitalised for acute myocardial infarction (AMI) is common in contemporary AMI care. Indeed, 28%–45% of patients hospitalised for AMI are now transferred to another hospital during their AMI event with practice driven by clinical guidelines that suggest patients with AMI benefit from highly specialised services and interventions, most notably early coronary angiography and revascularisation by percutaneous coronary intervention (PCI). These specialised services are not universally available among hospitals, and IHT is the primary means for accessing these services for many hospitalised patients with AMI.
Recent observations, however, have questioned whether IHT leads to improved patient outcomes. Prior studies have shown that transferred AMI patients have a lower risk profile compared with non-transferred patients. This observation has raised concerns that patients who undergo IHT may not necessarily have improved outcomes from such intervention because high risk patients generally derive greater benefit from specialized care such as PCI. However, the absolute risk profile and outcomes of transferred patients have not been previously described. Furthermore, a recent US study showed no difference in hospital level, risk-standardised 30-day mortality between hospitals with a high versus low transfer rate for patients with AMI. While this was a hospital-level rather than a patient-level analysis, it nevertheless suggested that transfer was not beneficial as an intervention in AMI care to improve patient outcomes.
Existing observational studies of transferred patients with AMI have limited ability to address these concerns. Although many studies have evaluated emergent transfer of ST-elevation myocardial infarction (STEMI) patients, relatively few have evaluated transfer of admitted patients, most of whom have a non-ST-elevation myocardial infarction (NSTEMI), and who are further along in their illness. The few studies that have evaluated admitted patients report lower 30-day mortality among transferred patients, yet these studies are often from selected populations and rarely report risk-adjusted outcomes. Most importantly, prior studies have not reported long-term patient mortality.
Accordingly, we assessed whether hospitalised patients with AMI who are transferred for specialised care during their AMI event have lower long-term mortality compared with similar patients solely treated at the presenting hospital using data from a large population cohort from Australia. We specifically sought to assess patient mortality based on the risk profile of transferred patients and the consistency of findings among various population subgroups.