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The strengths of the imaging modalities in coronary artery disease - changing roles

This session highlighted the strengths and weaknesses of state of the art non invasive imaging modalities for coronary artery disease (CAD) with the specific twist that each presenter reviewed the relative merits and weaknesses with the viewpoint of another discipline (e.g. the value of nuclear imaging through the magnifying glass of a cardiovascular MRI expert or the role of CT scan illustrated by the thoughts of an interventionalist). Thus the audience should get a more objective “birds-eye” view of the consumer rather than the provider.

Non-Invasive Imaging


The session opened with a very valuable contribution from Prof. Pim de Feyter from Rotterdam, Netherlands highlighting the strengths of computed tomography angiography (CTA) as a non invasive technique to assess anatomy. He stressed the complementary roles of anatomy and physiology in assessing the severity and importance of a given lesion or the extent of disease, in general. Specifically, the excellent negative predictive value makes it an important non invasive tool to rule out significant disease in patients with low to intermediate likelihood and risk of CAD and atypical chest pain. The quick assessment of the topographic distribution of coronary calcium also provides a possible new dimension in the improved evaluation of cardiac risk for a given patient. He also clarified that CTA is not yet in the position to replace invasive angiography, due to its limitations in temporal and spatial resolution. However, the combination of luminologic and functional information by ischemia testing (such as by stress echo, nuclear perfusion testing or CMRI) renders the most powerful association of non invasive testing. New roles are also seen in the assessment of coronary artery bypass grafts, whereas the reliable assessment of coronary stents is still in the early phases. Also the stratification of patients with chest pain in the emergency room will have to be measured against the yardstick of proven excellence of invasive angiography and also has to be seen in the full context of the clinical presentation of a given patient.

Next, Prof. Joerg Schwitter (Zurich, Switzerland) presented the clinical value of nuclear imaging. He clearly and convincingly illustrated the solid database and extensive experience to assess prognostic information for a given CAD patient. This is the field where nuclear perfusion imaging is at its best, while sometimes even with state of the art procedures, specificity can be a problem. Cardiovascular magnetic resonance offers unique superiority in spatial resolution, which helps to also assess mild or subendocardial patterns of ischemia. Furthermore, he illustrated how in clinical decision making, the analysis of ROC models can give a more objective impression of the performance of a test. Also the absence of radiation exposure is an important advantage of CMRI. Additionally, nuclear perfusion imaging has a long-standing proven record as a non invasive test for the assessment of presence and extent of ischemia. New developments of faster cameras will furtehr reduce imaging times. He agreed that the combination of CT information with perfusion data, either by nuclear or CMRI, may offer a more comprehensive “package”. He also stressed the importance of reducing radiation exposure, especially when follow-up testing is considered.

In the third contribution, Prof. J.M. Knuuti (Turku, Finland) highlighted the value of echocardiography through the eyes of a nuclear imaging expert, having also experience in hybrid imaging such as PET/CT. The obvious advantages such as the low cost, wide availability and also the absence of radiation have to be balanced against the operator-dependency, the less solid prognostic data, and no information about coronary anatomy for this universally available workhorse of all imaging modalities for the clinician. He also familiarised the audience with new developments in echocardiography, such as 3-D imaging, improvement of border definition by contrast echo, and tissue Doppler imaging. Brand new approaches such as velocity vector imaging (VVI) and automated functional imaging (AFI) may provide additional areas of interest. Frequently – especially in the absence of ultra high tech tomographic imaging equipment and big scanners – a well equipped state of the art echo device will be almost as good as nuclear imaging for many clinical questions. The beauty of nuclear on the other hand, is its huge database, the robustness of the test, and the improved possibilities of quantification.

Finally, Prof. Petros Nihoyannopoulos (London, UK) approached the value of cardiovascular magnetic resonance imaging from the standpoint of an echocardiographer. He also further expanded on the new technological advances in echocardiography development, and the worldwide widespread use of this technique. But he also mentioned some of the limitations of echocardiography (such as limited assessment of the apical area of the heart), and touched on the splendid resolution of CMR for subendocardial ischemia. CMR, although in smaller series as yet, has confirmed excellent accuracy for picking up stress induced ischemia and has shown equally good performance over the range of all coronary arteries. Additional advantages of CMR stress imaging were commented to exist in women, and for the assessment of viability. In the latter scenario, the ability to pick up non-transmural areas of necrosis and superior assessment of the extent of non viable myocardium also provide improved dimensions for viability imaging. Finally, he also mentioned new hope for improved detection of microvascular obstruction detection post acute interventions for myocardial infarction, which might relate also to final outcome. Additionally, the role of CMR for the assessment of hypertrophy cardiomyopathy and iron overload assessment was seen as important.

Conclusion:

All speakers also in short discussions with the audience and the panel, agreed on the importance of an integrated imaging approach, which sometimes may necessitate the application of multiple modalities for an optimal diagnosis and assessment of the clinical question. This new world of “togetherness” also poses new challenges for training, financing and logistical implementation in a given Department. It also became clear that it will be increasingly important to first ask the clinical question, and then choose the appropriate imaging modality. The aid in this decision-making may also be a role of a new breed of cardiac imagers in the field of cardiovascular specialists.

References


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SessionTitle:

The strengths of the imaging modalities in coronary artery disease - changing roles

Notes to editor


This congress report accompanies a presentation given at the ESC Congress 2008. Written by the author himself/herself, this report does not necessarily reflect the opinion of the European Society of Cardiology.

The content of this article reflects the personal opinion of the author/s and is not necessarily the official position of the European Society of Cardiology.