Association between emergency medical services' response times, low socioeconomic status, and poorer outcomes in out-of-hospital cardiac arrest: the MEDIC multicenter retrospective cohort study for disparities in access to prehospital critical care in the Paris metropolitan area.

Background And Importance: Prolonged emergency medical services' response times (EMS-RT) are associated with poorer outcomes in out-of-hospital cardiac arrest (OHCA). The patient access time interval (PATI), from vehicle stop until contact with patient, may be increased in areas with low socioeconomic status (SES).

Objectives: The objective of this study is to identify predictors of prolonged EMS-RT intervals, and to evaluate associations with clinical outcomes in OHCAs occurring in the largest metropolitan area in France.

Design: Using the Utstein-style, prospectively implemented, population-based SDEC registry for OHCAs, we conducted a multicenter, region-wide, retrospective cohort study of EMS dispatches for OHCA cases occurring in the 124 cities of the Greater Paris area, France, between January 1, 2017 and December 31, 2018.

Settings And Participants: Adult, nontraumatic, EMS-assessed, non-EMS witnessed OHCAs.

Exposure: Geographic location and scene-level SES.

Outcome Measures And Analysis: The primary outcome was the EMS-RT interval, from activation until arrival at patient's side. As secondary outcomes, we evaluated patient access outcomes of: (1) dispatch-to-patient contact interval ('EMS-RT'); and (2) vehicle scene arrival-to-patient contact interval (PATI); and patient clinical outcomes of: (1) death; and (2) unfavorable neurological status, both at 30 days. Area-level SES was assessed at census tract level using the European Deprivation Index (EDI; continuous, and divided into quintiles, Q5 = most deprived). We fitted multilevel mixed-effects regression models to identify predictors of patient access outcomes, and their association with clinical outcomes.

Main Results: We included 4082 cases; the median EMS-RT was 10.85 min (interquartile range [8.87-13.15]), and 138 (3.4%) survived to hospital discharge. Independent predictors of increased EMS-RT and PATI were age >65, female sex, residential location, occurrence at elevated floors, arrest unwitnessed by a bystander, and low EDI (all P < 0.018). After multivariable analysis, an overall EMS-RT interval >8 min was associated with higher mortality and poorer neurological status at hospital discharge (both P < 0.001).

Conclusion: In OHCA cases occurring in the Greater Paris metropolitan area, after adjustment for scene characteristics, EMS delays until patient contact were longer in neighborhoods of low SES, and were associated with poorer clinical outcomes.