Causes of delay and associated mortality in patients transferred with ST-segment-elevation myocardial infarction

Regional ST-segment-elevation myocardial infarction systems are being developed to improve timely access to primary percutaneous coronary intervention (PCI). System delays may diminish the mortality benefit achieved with primary PCI in ST-segment-elevation myocardial infarction patients, but the specific reasons for and clinical impact of delays in patients transferred for PCI are unknown.

This was a prospective, observational study of 2034 patients transferred for primary PCI at a single center as part of a regional ST-segment-elevation myocardial infarction system from March 2003 to December 2009. Despite long-distance transfers, 30.4% of patients (n=613) were treated in ≤ 90 minutes and 65.7% (n=1324) were treated in ≤ 120 minutes. Delays occurred most frequently at the referral hospital (64.0%, n=1298), followed by the PCI center (15.7%, n=317) and transport (12.6%, n=255). For the referral hospital, the most common reasons for delay were awaiting transport (26.4%, n=535) and emergency department delays (14.3%, n=289). Diagnostic dilemmas (median, 95.5 minutes; 25th and 75th percentiles, 72-127 minutes) and nondiagnostic initial ECGs (81 minutes; 64-110.5 minutes) led to delays of the greatest magnitude. Delays caused by cardiac arrest and/or cardiogenic shock had the highest in-hospital mortality (30.6%), in contrast with nondiagnostic initial ECGs, which, despite long treatment delays, did not affect mortality (0%). Significant variation in both the magnitude and clinical impact of delays also occurred during the transport and PCI center segments.

Treatment delays occur even in efficient systems for ST-segment-elevation myocardial infarction care. The clinical impact of specific delays in interhospital transfer for PCI varies according to the cause of the delay.