CLINICAL HISTORY
70 year-old woman presented with class III angina symptoms, having had an anteroseptal myocardial infarct three months beforehand. She was examined on a second-generation 128- slice dual-source CT system, using high-pitch acquisition (FLASH mode; pitch factor: 3.2) at 100 kV/320 mAs, with a pulsing window at 60% of the RR interval.
The CT protocol consisted of three scans, each lasting 0.4 secs: postadenosine stress, rest, and delayed enhancement. 1 The effective radiation dose for each scan was 1.37 mSv. The heart was captured within one heartbeat. An iodine(Drug information on iodine) contrast agent was used.
FINDINGS
CT showed a large reversible myocardial perfusion defect during stress, indicating ischemia with transmurality anterior (S7) and inferoseptal (S11), but nontransmurality in the remaining segments at midcavity level (Figure 1A). In the color coding of Hounsfield units (Figure 1B), blue/violet indicates the perfusion deficit, which had a lower HU compared with the normal myocardium.
A small, partially reversible subendocardial defect was observed in the inferior wall and a fully reversible defect in the anterior wall at rest. Figure 2A shows short-axis gray-scale multiplanar reformations. In color encoding of HU, bright colors indicate higher HU, which correspond to normal perfused myocardium (Figure 2B).
Coronary arteries were reconstructed from the rest-CT scan data sets. Maximum intensity projection reconstruction shows right coronary artery (RCA) and left circumflex (CX) artery (Figure 3A). Severe calcification limited exact delineation of lesion sites, in particular in the mid RCA. Black arrow shows falsepositive lesion in proximal RCA. White arrow denotes RCA occlusion site. Figure 3B shows the corresponding angiogram of RCA.
DIAGNOSIS
Angiography showed severe, advanced three-vessel coronary artery disease with occlusion of mid-left anterior descending (LAD) artery, high-grade stenosis in mid-CX, and occlusion in mid-RCA with some collaterals present.
DISCUSSION
Figure 4A shows LAD occlusion (white arrow) on CT. Figure 4B shows mid-CX stenosis (black arrow) on CT, and Figure 4C shows the corresponding angiogram. Note how the proximal CX calcification on CT mimics a high-grade stenosis. The true lesion site was more distal (before the bifurcation, see black arrow), and was caused by a noncalcifying plaque. Delayedenhancement images showed a small scar at the apex, but not in the remaining segments. Coronary artery bypass graft surgery was planned accordingly.
CONCLUSION
Low-dose, adenosine(Drug information on adenosine) stress myocardial CT perfusion imaging is feasible on a dual-source CT system using a high-pitch, spiral- acquisition mode. Future studies will define whether stress myocardial CT perfusion can guide clinical management in patients with suspected or known coronary artery disease.
Case submitted by Gudrun Feuchtner, M.D., of the radiology department at Innsbruck Medical University in Austria, and the Institute of Diagnostic Radiology at the University Hospital Zürich. Ricardo C. Cury, M.D., is a radiologist with Baptist Cardiac and Vascular Institute in Miami, Florida, and Massachusetts General Hospital in Boston, Massachusetts. Andrè Plass, M.D., Hans Scheffel, M.D., Borut Marincek, M.D., Hatem Alkadhi, M.D., and Sebastian Leschka, M.D., are all from the Institute of Diagnostic Radiology at University Hospital Zürich.
REFERENCE
1. Blankstein R, Shturman LD, Rogers IS, et al. Adenosine induced stress myocardial perfusion imaging using dual source cardiac computed tomography. J Am Coll Cardiol 2009;54(12):1072-1084.
