Abstract 1911: Myocardial Infarction Imaging by Early and Late-Phase 64-Slice CT in Comparison to MRI
Background Knowledge about the size and transmural extent of myocardial infarction has prognostic value and therapeutic consequences. We investigated the accuracy of 64-slice CT to detect and quantify myocardial infarct size by early and late myocardial enhancement, and compared CT findings with MRI.
Methods Cardiac CT and MRI was performed in 21 patients few days after acute ST-elevation myocardial infarction, treated by percutaneous coronary intervention. Cardiac CT (Sensation 64, Siemens) was performed 2.6±1.2 days after myocardial infarction. Early-phase images (EP-CT) were acquired immediately after injection of 83±4 ml of contrast medium (iomeprol). In 15 patients a second acquisition was performed 7 min after contrast injection (DE-CT). MR first-pass perfusion imaging (FP-MR) was performed after injection of 0.1 mmol/kg of Gd-DTPA (CV/i, GE), and delayed images (DE-MR) were acquired 10 minutes after a second contrast bolus.
Results Hypo-enhanced myocardium by EP-CT was identified in all 21 patients, while infarction (hyper- with/without hypo-enhancement) was detected by DE-CT in 12/15 patients. Early acquisitions by CT (3.7±1.7) and MR (3.5±1.4) showed comparable contrast-to-noise, while the contrast-to-noise ratio was significantly better for DE-MR (9.4±3.4) compared to DE-CT (1.8±1.2, P<0.001). The volume of hypo-enhancement as a percentage of the total LV myocardium volume by EP-CT (11±6%) correlated well with FP-MR (7±5%, R2 = 0.72), but was significantly larger (P<0.001). Infarct size by DE-CT 13±9% was similar to DE-MR (15±7%, R2 = 0.68, P=0.37). The amount of hypo-enhancement (microvascular obstruction) in DE-CT and DE-MR correlated well: CT 4±4% vs. MRI 3±2% (R2 = 0.85, P=0.1). Segmental infarction infarction was assessed in all patients at 5 consecutive, anatomically matched short-axis levels. The sensitivity and specificity of EP-CT and DE-CT for detection of segmental infarction was 72% and 97%, and 63% and 96%, respectively.
Conclusion Hypo-enhancement can be detected by CT in all patients after myocardial infarction, although global infarct size is underestimated compared to DE-MR. Infarct size by DE-CT correlates well with DE-MRI, but delayed enhancement could not be demonstrated in a number of patients.