Chest pain CT in the emergency department: Watch out for the myocardium

RATIONALE AND OBJECTIVES: To evaluate the frequency and relevance of hypodense myocardium (HM) encountered in patients undergoing chest-pain CT in the emergency department (ED). MATERIAL AND METHODS: In this IRB-approved retrospective study, ECG-gated chest-pain CT examinations of 300 consecutive patients (mean age 60 ± 17 years) presenting with acute chest-pain to our ED were evaluated. Once ST-segment elevation infarction was excluded, chest-pain CT including the coronary arteries (rule-out acute coronary syndrome (ACS), pulmonary embolism (PE) and acute aortic syndrome (AAS): chest-pain CT(coronary), n = 121) or not including the coronary arteries was performed (rule-out PE and AAS: chest-pain CT(w/o coronary), n = 179). Each myocardial segment was assessed for the presence of HM; attenuation was measured and compared to normal myocardium. RESULTS: HM was identified in 27/300 patients (9%): 12/179 in chest-pain CT(w/o coronary) (7%) and 15/121 in chest-pain CT(coronary) (12%). Mean attenuation of HM (40 ± 17 HU) was significantly lower than that of healthy myocardium (103 ± 18 HU, p < 0.001), with a mean difference of 61 ± 19 HU. In 15/27 patients (55.6%) with HM, the final diagnosis was acute MI, and in the remaining 12/27 patients (44.4%) previous MI was found in the patients’ history. Chest-pain CT(w/o coronary) identified HM in 10/15 patients (66.6%) with a final diagnosis of acute MI. CONCLUSION: HM indicating acute MI are often encountered in chest pain CT in the ED, also in chest-pain CT(w/o coronary) when MI is not suspected. This indicates that the myocardium should always be analyzed for hypodense regions even when MI not suspected.