Dr. Pasquale Perrone-Filardi
Cardiac computed tomography is an emerging technique in cardiovascular imaging that provides an opportunity to look at coronary vessels, cardiac morphology, atherosclerosis burden and myocardial function in several clinical contexts. The symposium covered novel technical and clinical aspects of this imaging modality and also provided new potential clinical applications supported at the moment by experimental data. Prof. Kaufmann presented data on the technical feasibility and clinical application of the technique of prospective ECG triggering for computed tomography coronary angiography. This technique is mainly based on sequential and fast imaging of consecutive myocardial slices covering the entire left ventricle and substantially reducing the radiation exposure in the range of 2 mSv. In clinical studies this technique favourably compared to invasive coronary angiography reducing mean radiation exposure from 8.5 to 2.1 mSv, respectively, with very high (above 90%) sensitivity and specificity. From a personal series of 612 patients studied in his institution, Prof Kaufmann reported a low mean dose of 1.8 mSv with an imaging feasibility in 89% of all coronary segments evaluated. The main limitation remains the need to substantially lower heart rate, preferably below 62 bpm. However, this technical approach will rapidly grow in routine clinical use in the opinion of Prof. Kaufmann. Prof. Schroeder reported on the use of computed tomography coronary angiography in patients with chest pain and suspected coronary artery disease. May such patients ultimately undergo invasive angiography, substantially contributing to the very high number (up to 65%) of invasive studies with normal or not significantly diseased coronary arteries. For these subjects non invasive coronary angiography is, therefore, particularly indicated as test modality in the presence of equivocal or negative stress test. However, as Prof. Schroeder pointed out, a careful selection of candidates is crucial to ensure the most cost-effective use. Such selection should take into account the pre-test probability of coronary artery disease in the single patient and limit non invasive angiography to subjects with intermediate pre-test likelihood of disease. In addition to very high diagnostic accuracy, Prof. Schroeder focused on the incremental prognostic value of non invasive angiography based on the possibility to identify, at variance with calcium scoring, both calcified and non-calcified coronary plaques. Prof. De Feyter gave an overview of the potential usefulness of non invasive angiography for interventional cardiologists in the cath lab. He showed examples of clinical scenarios where the information of CT angiography maybe complementary to that of invasive angiography. Such potential clinical contexts include evaluation of ostial lesions, of anomalous coronary origin, of vessel status down to total occlusions, as well as evaluation of stent implantation and of by-pass grafting. He also cautioned about the limitation of non invasive angiography in the quantification of coronary stenosis being responsible for reduced predictive values in some clinical studies. Finally, Prof. Gerber summarized fascinating potential new applications of CT angiography for the evaluation of coronary plaques. He showed examples of plaque morphology studies demonstrating how the remodelling of the vessel can be imaged. He also presented mainly experimental data about plaque volume quantification and plaque biological composition. This latter aspect has the potential to track relevant steps along the inflammatory process of vessel atherosclerosis including enhanced iron content and neovascularisation that have been linked in clinical studies to the occurrence of plaque instability and acute coronary syndromes. Although these studies remain mostly experimental at this time, they open new research avenues for a versatile technique that has the potential to go well beyond the imaging of coronary lesions.
Cutting edge cardiac computed tomography
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