Emergency Medical Services Remains Underutilized in STEMI Patients

November 13, 2007 By Grendel Burrell [mailto:grendel.burrell@gmail.com]

Almost 30 years after Seattle’s landmark Myocardial Infarction Triage and Intervention (MITI) Trial, emergency medical services (EMS) within a Minnesota regionalized STEMI care system are not maximized. While access to EMS has improved, only 34% of males < 65 years, living in rural Minnesota, utilize EMS transport for STEMI.

The results were recently presented as a poster at AHA 2007 in Orlando by Katie Menssen, a first year medical student, and co-authors from the Minneapolis Heart Institute Foundation. They assessed the prevalence of Emergency Medical Services (EMS) use by ST-segment myocardial infarction (STEMI) patients and its impact on door to balloon times in a regional STEMI network by stratifying the use of EMS in STEMI patients from urban and rural communities by age and gender.

Data was obtained from a prospective registry of 1464 consecutive STEMI patients in the “Level 1 MI” program, a regional network that includes the Minneapolis Heart Institute/Abbott Northwestern Hospital and 30 community hospitals in Minnesota. All patients were directly admitted or transferred to a regional PCI center. The Level 1 MI Protocol consists of STEMI (ST elevation or new left bundle branch block) with symptoms <24 hours, including those with cardiac arrest, cardiogenic shock, and advanced age. The emergency physician at the presenting hospital makes the diagnosis and decision to activate the cath lab. Transferred patients bypass the emergency department and go directly to cath lab for primary or facilitated PCI.

EMS use by STEMI patients was stratified by gender, age, and rural vs. urban location. For this analysis, urban patients were defined as those who presented directly to the PCI center, and rural patients were those transferred directly to the tertiary PCI center from a community hospital outside of Minneapolis. There were disparities in the use of EMS in both gender and age groups. 64.8% of males living in an urban area and 37.0% of rural males used EMS. Furthermore, 64.6% of urban females were transported by EMS compared to 49.1% of rural females.

When the authors considered age and setting, 62% of urban males <65 years used EMS compared to only 34.6% of rural men in the same age group. The numbers slightly improved for those patients >65 years. In this group, 68.9% of urban males and 48.3% or rural males used EMS.

Overall, only 40% of rural STEMI patients utilized EMS compared to 65% of urban patients. Patients in a rural location, male gender (p<0.0001) and age <65 (p<0.0001) were less likely to use EMS.

In the urban setting where 64.7% of patients arrived by EMS, there were no significant age group (p=0.50) or gender (p=0.64) differences. Current smoking history was found in 42.7% of rural patients and in 36.8% of urban patients. Median door to balloon times were shorter for those using EMS in both urban (60 vs. 77 minutes, p<0.0001) and rural settings (103 vs. 107 minutes, p=0.006).

Significant gender and age differences are present in rural EMS utilization. Door to balloon times are faster when STEMI patients use EMS in both settings. These results should alert physicians practicing in rural settings to remind all of their patients with cardiovascular risk factors to call 911 when signs and symptoms of myocardial infarction are present. Involving family members in the discussion so there is an advocate for EMS may also be helpful.

Asked to comment on the results, Tim Henry, MD, Director of Research, Minneapolis Heart Institute Foundation, stated, “We know that pts who use EMS have faster times to treatment and better outcomes. Unfortunately, EMS utilization continues to be too low for a number of reasons. Understanding utilization patterns may help us to target underserved populations. Our results indicate there are significant disparities in rural vs. urban utilization and should therefore help focus attention on ways to improve the EMS systems in rural areas of the US.”