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Follow-up For Post-MI Stent PatientLow dose cardiac CT scanning with prospective SnapShot Pulse acquisition allows for more regular patient follow-up. Increased spatial resolution permits for better assessment in challenging cases involving stents.
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Courtesy of Dr. J.L Sablayrolles, Centre Cardiologique du Nord, Saint-Denis, France
The Centre Cardiologique du Nord (CCN) was founded in 1973 by a consortium of cardiologists and established in Saint-Denis, 3 km north of Paris. Its specialty, as can be taken by its name, are cardiovascular pathologies. With more than 180 beds and over 1000 cardiac interventions per year, it is renowned as a center of excellence in the diagnosis and treatment of cardiovascular illnesses. The Radiology Service has been active in the cardiac CT scanning field since the year 2000, having used a LightSpeed VCT and a LightSpeed VCT XT scanner to perform these exams. More recently, their cardiac CT-scanning activity has been passed on to the their newly acquired Discovery™ CT750HD, with more than 800 cardiac scans in 4 months of activity.
Patient History
A 59-year-old man suffered an inferior myocardial infarction due to severe stenosis of the right coronary artery. The patient underwent an angioplasty of the RCA and a stent was placed in segment II. Two follow-up CT scans were performed (6 months apart) to evaluate the state of the stent as well as other abnormalities in the heart.
Technique
The first follow-up cardiac CT exam was performed on a LightSpeed VCT XT (GE Healthcare) using cardiac mode with prospective ECG-gating. The heart rate was 42 BPM and the resulting dose was 3.91 mSv* (230 mGy.cm).
The second cardiac CT exam was performed 6 months later on the new Discovery CT750HD (GE Healthcare), using cardiac mode, ASIR reconstruction and High Definition with prospective ECG-gating. The heart rate was 50 BPM and the resulting dose was estimated to be 1.52 mSv* (90 mGy.cm**).
The contrast injection was biphasic, using 90 mL of Omnipaque 350 and 50 mL of saline solution, both injected at 5 mL/s.
* Dose conversion obtained from EUR-16262 EN with chest factor of DLP*0.017** Dose based on phantom estimates of a prospective ECG-gated acquisition with 10 ms padding
Findings
LightSpeed VCT XT
After the first scan was performed, restenosis within the stent was observed, although less than 50% of the lumen’s cross-section was obstructed. A few points of necrosis can also be detected near the apex of the heart where the MI took place.
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Discovery CT750HD
Six months later, with a repeat scan on the Discovery CT750HD, the intra-stent stenosis was re-evaluated to be at 50-60% of the cross-section of the lumen. Furthermore, a new stenotic region was identified within first marginal branch of the left circumflex artery (LCx), obstructing nearly 60% of the vessel’s cross-section.
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