Helicopter emergency medical service for patients with acute coronary syndrome: selection validity and impact on clinical outcomes.

Helicopter emergency medical service (HEMS) has the potential to improve prognosis for acute coronary syndrome (ACS). However, adequacy and effectiveness of HEMS have not been fully evaluated. A total of 862 ACS patients transferred by emergency medical services were divided into two groups: patients transferred by HEMS (n = 171) or by ground ambulance (GA; n = 691). Among them, angiography images for 718 patients (149 in HEMS and 569 in GA group) and optical coherence tomography (OCT) images for 374 patients (75 in HEMS and 299 in GA groups) were analyzed. Additional analysis to compare 2-year cardiac mortality between groups was conducted following propensity score matching to adjust for inter-group differences. ST-segment elevation myocardial infarction (81% vs. 66%, p < 0.001) and cardiogenic shock (Killip IV; 20% vs. 10%, p < 0.001) at admission were more prevalent in HEMS than GA group. Time from admission to balloon angioplasty was shorter in HEMS group (median 54 min vs. 69 min, p < 0.001). Antegrade coronary flow was worse in HEMS group (TIMI flow grade 0 or 1; 68% vs. 51%, p < 0.001). Plaque rupture was more frequently detected by OCT in HEMS group (68% vs. 49%, p = 0.029). Following propensity score matching, the incidence of cardiac death was significantly lower in HEMS group (6.3% vs. 14.9%, p = 0.019). In conclusion, severe ACS patients requiring early reperfusion were appropriately triaged and transferred more rapidly by HEMS. Lower mortality in HEMS group after propensity score matching suggests that HEMS may improve cardiac mortality in ACS patients.