Objectives: A 10-month direct mail campaign was implemented to increase use of emergency medical services via 911 calls and to reduce prehospital delay for individuals experiencing acute myocardial infarction symptoms.
Methods: This prospective, randomized, controlled trial involved three intervention groups (receiving brochures with informational, emotional, or social messages) and a control group.
Results: Intervention effects were not observed except for individuals who had a history of acute myocardial infarction and who were discharged with a diagnosis of acute myocardial infarction; their 911 use was meaningfully higher in each intervention group than in the control group.
Conclusions: The mailings affected only the individuals at greatest risk.