Reducing Door-in Door-out Intervals in Helicopter ST-segment Elevation Myocardial Infarction Interhospital Transfers

Many health systems rely on helicopter EMS (HEMS) to transfer ST-elevation myocardial infarction (STEMI) patients for percutaneous coronary intervention (PCI) to a hospital with a catheterization laboratory. Mortality rates increase with the time to reperfusion, so reducing delays is imperative. For interhospital STEMI transfers, the time spent in the initial hospital from arrival until departure (door-in to door-out interval or DIDO) should be minimized.

To evaluate the impact of a series of process improvements to reduce DIDO intervals for STEMI patients transferred via a hospital based HEMS program.

Changes made to the STEMI transfer protocol in March 2011 were: (a) allowing transferring facilities to request HEMS before identifying an accepting cardiologist or hospital, with one hospital serving as a default PCI center in the case of delays, (b) limiting continuous infusions to those absolutely necessary for the transfer flights and (c) training flight crews to minimize time at bedside. Trained dual abstractors conducted structured medical record reviews for all STEMI patients 18 years and older, transferred to a PCI facility by HEMS from March 2011 to December 2012. Discrepancies were adjudicated. We compared DIDO intervals to a historical control cohort from 2007. We used the Mann-Whitney U test to compare times, and calculated differences with 95% confidence intervals.

Of 244 patients identified, six were excluded due to incomplete data. The historical cohort included 179 cases. Mean age was 59 (SD 14) years, 81% were white and 66% male. There were no differences in patient characteristics or door to EKG times between the cohorts. Median door-in to door-out interval decreased from 83 minutes (IQR 43) to 68 minutes (IQR 31) (difference 15 minutes, 95% CI 8 to 21, P <.0001). EKG to HEMS request decreased 21 minutes (95% CI 17 to 25, P <.0001), and HEMS ground time decreased 3 minutes (95% CI 2 to 4, P <.0001). There was a 32% absolute increase in the proportion of patients with EKG to helicopter request interval <35 minutes (83% vs 51%, difference 32%, 95% CI 24% to 41%, P <.0001).

HEMS-focused process improvements can significantly reduce the DIDO interval times for STEMI patients transferred for PCI.