Pre-hospital transthoracic echocardiography for early identification of non-ST-elevation myocardial infarction in patients with acute coronary syndrome

BACKGROUND: Non-ST elevation myocardial infarction (NSTEMI) is a common manifestation of acute coronary syndrome (ACS), but delayed diagnosis can increase mortality. In this proof of principle study, the emergency physician performed transthoracic echocardiography (TTE) on scene to determine whether NSTEMI could be correctly diagnosed pre-hospitalization. This could expedite admission to the appropriate facility and reduce the delay until initiation of correct therapy. METHODS: Pre-hospital TTE was performed on scene by the emergency physician in patients presenting with ACS but without ST-elevation in the initial 12-lead electrocardiography (ECG) (NSTE-ACS). A presumptive NSTEMI diagnosis was made if regional wall motion abnormalities (RWMA) were detected. These patients were admitted directly to a specialist cardiac facility. Patient characteristics and pre-admission and post-admission clinical, pre-hospital TTE data, and therapeutic measures were recorded. RESULTS: Patients with NSTE-ACS (n = 53; 72.5 ± 13.4 years of age; 23 female) were studied. The 20 patients with pre-hospital RWMA and presumptive NSTEMI, and two without RWMA were conclusively diagnosed with NSTEMI in hospital. Percutaneous coronary intervention was performed in 50% of the patients presumed to have NSTEMI immediately after admission. The RWMA seen before hospital TTE corresponded with the in-hospital ECG findings and/or the supply regions of the occluded coronary vessels seen during PCI in 85% of the cases. The diagnostic sensitivity of pre-hospital TTE for NSTEMI was 90.9% with 100% specificity. CONCLUSIONS: Pre-hospital transthoracic echocardiography by the emergency physician can correctly diagnose NSTEMI in more than 90% of cases. This can expedite the initiation of appropriate therapy and could thereby conceivably reduce morbidity and mortality. TRIAL REGISTRATION: Deutsche Register klinischer Studien, DRKS00004919 . Registered on 29 April 2013.