MedicalResearch: What are the main findings of the study?
Dr. Lambert: Patients with ST-elevation myocardial infarction (STEMI) are frequently transferred for percutaneous coronary reperfusion from a hospital without this capability. Favourable outcomes depend on minimizing delays to treatment. A major component of delay is the time from the patient’s arrival at the first hospital’s emergency department to departure to the hospital where percutaneous reperfusion will be performed, the ‘door-in-door-out’ time or DIDO. We characterized this component of delay in a systematic field evaluation of STEMI treatment over a large and populous geographic area.
The major contributors to DIDO time were the delays
- (1) from the initial in-hospital ECG acquisition to transfer activation by the emergency physician and
- (2) from arrival of the transfer ambulance at the first hospital to departure of the ambulance for the primary percutaneous coronary intervention center. When the DIDO interval was timely (30 minutes or less as recommended by guidelines), reperfusion treatment was far more frequently within guideline-recommended delays (90 minutes or less). In fact, this benchmark of DIDO time was met in only 14% of cases. We identified a number of factors associated with untimely DIDO, an important one being an ambiguous presenting ECG. DIDO times were faster when patients arrived at the first hospital by ambulance particularly when retransfer to the second hospital was with the same ambulance that had remained on standby.
MedicalResearch: Were any of the findings unexpected?
Dr. Lambert: Although we anticipated that DIDO times would generally exceed the recommended delay, we were surprised that the maximum 30-minute benchmark for this delay was met in just 14% of cases. We were also surprised at the length of the delay in the emergency department between arrival of the transfer ambulance (or its readiness for service if already on site) and departure of the ambulance for the second hospital (median 14 minutes). That as many as 40% of presenting ECGs did not have a clear cut interpretation of STEMI and how this appeared to substantially contribute to longer DIDO times were also unexpected findings.
MedicalResearch: What should clinicians and patients take away from your report?
Dr. Lambert: Despite increasing use of prehospital ECGs and a policy of direct routing of patients with presumptive STEMI to centers with the capability to perform percutaneous reperfusion, an important proportion of patients in large geographic regions such as Canada and the United States will receive initial evaluation at centers without this capability. Therefore, DIDO time is likely to remain a crucial determinant of overall delay to reperfusion in a substantial proportion of patients with STEMI.
Facilitation of the transfer decision, particularly when emergency physicians are faced with difficult-to-interpret ECGs (i.e., not a clear-cut STEMI on the ECG), is likely to have the most favorable impact on reducing DIDO time, followed by keeping the door-in ambulance on standby for transfer. Our results point to the importance of increasing support for emergency physicians for the interpretation of difficult ECGs, especially in lower-volume STEMI settings, as well as clear, standardized protocols and corridors of service.
MedicalResearch: What recommendations do you have for future research as a result of this study?
Dr. Lambert: It is crucial to reduce delays to treatment to a minimum in order to improve outcomes in patients with STEMI. Contemporary real word data such as that generated by this systematic field evaluation provides clinicians and policy decision-makers with the information and clues needed to optimize treatment strategies. Studies such as this one that reveal substantial underperformance point to the need for continued monitoring of STEMI treatments and delays. Future research should determine whether significant improvement is possible within current strategies and treatment algorithms, failing which other approaches such as prompt fibrinolysis at first medical contact or at the first non-tertiary cardiac center may better meet delay benchmarks and improve outcomes.