High Detectability of Prehospital 12-Lead Electrocardiogram in Diagnosing Spasm-Induced Acute Coronary Syndrome

Background: The importance of prehospital (PH) electrocardiograms (ECG) recorded by emergency medical services (EMS) for diagnosing coronary artery spasm-induced acute coronary syndrome (CS-ACS) remains unclear. Methods and Results: We enrolled 340 consecutive patients with ACS who were transported by EMS within 12 h of symptom onset. According to Japanese Circulation Society guidelines, CS-ACS (n=48) was diagnosed with or without a pharmacological provocation test (n=34 and n=14, respectively). Obstructive coronary artery-induced ACS (OC-ACS; n=292) was defined as ACS with a culprit lesion showing 99% stenosis or >75% stenosis with plaque rupture or thrombosis observed via angiographic and intravascular imaging. Ischemic ECG findings included ST-segment deviation (elevation or depression) and negative T and U waves. In CS-ACS, the prevalence of ST-segment deviation decreased significantly from PH-ECG to emergency room (ER) ECG (77.0% vs. 35.4%; P<0.001), as did the prevalence of overall ECG abnormalities (81.2% vs. 45.8%; P<0.001). Conversely, in OC-ACS, there was a similar prevalence on PH-ECG and ER-ECG of ST-segment deviations (94.8% vs. 92.8%, respectively; P=0.057) and abnormal ECG findings (96.9% vs. 95.2%, respectively; P=0.058). Patients with abnormal PH-ECG findings that disappeared upon arrival at hospital without ER-ECG or troponin abnormalities were more frequent in the CS-ACS than OC-ACS group (20.8% vs. 1.0%; P<0.001). Conclusions: PH-ECG is valuable for detecting abnormal ECG findings that disappear upon arrival at hospital in CS-ACS patients.