Purpose: AMI can simulate AAD in clinical presentation; we describe the incidence of AMI for patients with acute chest pain suspicious for AAD and its appearance on MSCT.
Methods and Materials: We retrospectively studied MSCT cases performed at our institution for acute chest pain suspicious for AAD over a 7-month period. MSCT image features and ECG/biomarker evidence for possible AMI (ACC criteria) were recorded. Regional myocardial hypodensity (RMH) without myocardial wall thinning was considered indicative of AMI on MSCT. Correlation with ancillary imaging studies (coronary angiogram, echo, SPECT) was performed when available. Two scanner types were employed. A 4-slice MSCT scanner used spiral technique and prospective sequential triggering protocols with 2 separate injections of contrast (100 cc and 80 cc respectively) at 3 cc/s. A 16-slice MSCT scanner used spiral acquisition with retrospectively gated reconstruction using 110 cc of contrast injected at 3 cc/s.
Results: Of a total 64 cases presenting with suspected AAD, 8/64 (13%) had AAD (all Stanford Type B). A separate 10/64 (16%) cases had clinically proven AMI (8 same-day, 2 within 5 days post-infarct). Of this sub-group, 9 cases demonstrated areas of RMH without thinning. Three other cases had areas of RMH but with negative biomarkers (same day, one set) and no ECG evidence. RMH without myocardial wall thinning thus had a high correlation to AMI.
Conclusion: (1) AMI is frequently the cause of symptoms in patients being evaluated for AAD. (2) MSCT is sensitive to the diagnosis of AMI in this patient population.