Case: Dual Energy Coronary CTA for Evaluation of Chest Pain after RCA Revascularization
History
A 54-year-old female patient underwent coronary stent PTCA of the RCA four months ago for acute ST-elevation myocardial infarction of the inferioseptal wall. The patient had an event of syncope 3 weeks ago and suffers from reduced physical power and labile blood pressure.
Invasive coronary angiography was performed to assess stent patency. In-stent occlusion of the mid and distal RCA with moderate collateralization from the LAD and LCX and a patent right ventricular (RV) branch was found (Figure 1).
Recanalization was performed with placement of 2 drug-eluting stents in the distal and mid RCA. During intervention, a small contrast material extravasation was seen near the ostium in the proximal RCA. A small intima dissection was suspected and another stent was placed to close the leakage.
Three hours after intervention, the patient developed chest tightness and retrosternal pain. ECG showed signs of the known chronic infarction inferiorseptal (Q waves in II, III and aVF) but no signs of acute ischemia. She was sent to CT to rule out aortic dissection.
Diagnosis
Cardiac CT was performed in Dual Energy mode with retrospective ECG-gating. There was no sign of contrast material extravasation or aortic dissection. Dual Energy CT angiography revealed in-stent thrombosis with occlusion of the RCA 13 mm after its origin (Figure 2). While on cardiac cath the RV branch was still open, DECT showed an occlusion of the vessel due to the thrombus in the proximal RCA explaining the patient’s symptoms. Dual Energy myocardial iodine mapping showed a large hypoperfused area inferoseptal extending from the base down to the apex (Figure 3). Low-dose step-and-shoot late enhancement images 7 minutes after contrast injection showed corresponding delayed contrast material wash-out (Figure 4). On regular anatomical multiplanar reformates a moderate thinning of the left ventricular myocardium was present in that area (Figure 5).
Comments
In this case, Dual Energy coronary CT angiography was used to image a complication of interventional recanalization, i.e. acute in-stent thrombosis, while the initial clinical diagnosis of acute aortic dissection could reliably be ruled out.
Due to the large thrombus formation beginning very proximally in the RCA a further complication was the occlusion of the RV branch, which was patent prior to intervention. The new hybrid reconstruction algorithm for coronary CTA images preserves the high temporal resolution of 75 ms of the Dual Source system and allows for motion-free imaging of the vascular structures. According to the clinical history of the patient, assessment of the myocardium with Dual Energy first-pass perfusion and late enhancement imaging showed signs of chronic infarction in the inferoseptal wall of the left ventricle. Increased tube power as well as improved separation of the spectra by using a tin filter (140 kV + Sn) allow for artifact-free imaging of myocardial perfusion. Complete diagnostic work-up of the coronary arteries and the myocardium was achieved with a total dose length product of only 294 mGycm (227 mGycm CTA + 67 mGycm late enhancement).
Authors: Ralf W. Bauer, MD, J. Matthias Kerl, MD, Thomas J. Vogl, MD
