Supervisors info:
Σ. Σπηλιόπουλος, Επίκουρος Καθηγητής, Ιατρική, ΕΚΠΑ
Σ. Αργέντος, Διευθυντής ΕΣΥ, ΠΓΝ ΑΤΤΙΚΟΝ
Χ. Βεργαντής, Επιμελητής Β’ ΕΣΥ, ΓΝΑ Λαϊκό
Summary:
Introduction: Severe aortic stenosis (AS) is the most common valvular disease and is associated with high mortality if untreated. Although aortic valve replacement remains the gold standard for treatment, trans-catheter aortic valve implantation (TAVI) has recently emerged as an alternative technique for patients with high surgical risk. Multi-slice computed tomography (MSCT) is increasingly employed for assessing the size of the vasculature but also for assessing the landing zone of the trans-catheter valve and for the prevention of complications. We prospectively evaluated three different scanning protocols of CT cardiac imaging, CT angiography (CTA) of corresponding vessels, and IV administration of contrast material (CM).
Patients and methods: This is a prospective study in 10 patients (5 males, 5 females, 31-91 years) candidates for TAVI who were referred to our department for pre-procedural assessment, including CT scan of the heart and CTA of the aorta and its branches. All CT acquisitions were conducted using a Siemens Somatom Definition AS 128+™scanner. As per the first protocol, ECG gating was applied for the coronary CTA (CCTA) but not for the CTA and a total volume of CM of 160ml was injected using an automatic injector pump. The acquisition method for the second protocol remained unchanged however the total volume of the CM administered was reduced to 40ml. The third protocol unlike previous acquisitions, was performed with ECG gating for both the CCTA and CTA and an IV injection 90-120ml total volume of CM, depending on patient’s BMI. We comparatively assessed the 3 protocols in respect to the quality of the acquired images and the radiation dose received by the patients. All the measurements were executed during the diastolic cardiac phase, except for the measurement of the size of the 3 sinuses of Valsava, the distance between the orifices of the coronary arteries and the annular sizing, which were completed during the systolic cardiac phase. Characterization and quantification of calcium in the landing zone and the coronary arteries was performed by using the Agatston method.
Results: Regarding the quality of the images and the radiation dose, we found no statistically significant differences among the 3 protocols. The comparison of the parameters of the aortic root calculated with the 3 methods did not reveal significant differences between the systolic and diastolic phase of the cardiac cycle, except for the diameter of the aortic root, which was increased during the systolic phase. When we compared the distance between the lower edge of the coronary arteries and the aortic annulus with or without the stretched projection/view technique, we detected statistical significant difference only in the size of the right coronary artery during the diastolic cardiac phase. Moreover, we found no correlation between the calcium burden of the coronary arteries and that of the aortic root. Concerning the assessment of the vasculature, the usage of the stretched projection/view technique was not feasible for the second protocol. Although this technique was supportive for protocol 1, manual corrections by the physician were necessary. Contrarily, for protocol 3 the implementation of the standard software was sufficient.
Conclusions: By comparing the 3 protocols we believe that for elderly patients with low risk of complications to intravenous contrast material, the ideal option is protocol 3 as it presents the most accurate assessment while maintaining reduced radiation dose. For elderly patients with poor kidney function, we suggest protocol 2, which offers satisfactory heart imaging with a minimal dose of intravenous contrast material. Moreover, in younger patients, where low radiation dose is vital, we suggest the first protocol for superior imaging of the vasculature or the second protocol in cases of renal impairment.
