Dyspnea, a high-risk symptom in patients suspected of myocardial infarction in the ambulance? A population-based follow-up study

Morten Thingemann Bøtker, Carsten Stengaard, Mikkel Strømgaard Andersen, Hanne Maare Søndergaard, Karen Kaae Dodt, Troels Niemann, Hans Kirkegaard, Erika Frischknecht Christensen, Christian Juhl Terkelsen

Systematic management of patients suffering high-risk symptoms is essential in emergency medical services. Patients with chest pain receive algorithm-based work-up and treatment. Though dyspnea is recognized as an independent predictor of mortality, no generally accepted prehospital treatment algorithm exists and this may affect outcome. The objective of this study was to compare mortality in patients suspected of myocardial infarction (MI) presenting with dyspnea versus chest pain in the ambulance. Follow-up study in patients undergoing electrocardiogram-based telemedical triage because of suspected MI in an ambulance in the Central Denmark Region from 1 June 2008 to 1 January 2013. Primary outcome was 30-day mortality. Secondary outcomes were 4-year mortality and mortality rates in subgroups of patients with and without a confirmed MI. Absolute risk differences adjusted for comorbidity, age, systolic blood pressure and heart rate were calculated by a generalized linear regression model. Of 17,398 patients, 12,230 (70 %) suffered from chest pain, 1464 (8 %) from dyspnea, 3540 (20 %) from other symptoms and 164 (1 %) from cardiac arrest. Among patients with dyspnea, 30-day mortality was 13 % (CI 12-15) and 4-year mortality was 50 % (CI 47-54) compared to 2.9 % (CI 2.6-3.2) and 20 % (CI 19-21) in patients with chest pain. MI was confirmed in 121 (8.3 %) patients with dyspnea and in 2319 (19 %) with chest pain. Patients with dyspnea and confirmed MI had a 30-day and 4-year mortality of 21 % (CI 15-30) and 60 % (CI 50-70) compared to 5.0 % (CI 4.2-5.8) and 23 % (CI 21-25) in patients with chest pain and confirmed MI. Adjusting for age, comorbidity, systolic blood pressure and heart rate did not change these patterns. Patients suspected of MI presenting with dyspnea have significantly higher short- and long-term mortality than patients with chest pain irrespective of a confirmed MI diagnosis. Future studies should examine if supplementary prehospital diagnostics can improve triage, facilitate early therapy and improve outcome in patients presenting with dyspnea.