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Noninvasive Coronary Imaging

02.09.2003

ESC Congress 2003: Picture Perfect – Progress in non-invasive imaging

There has been increasing awareness of the importance of composition of athero-thrombotic plaque as a major risk factor for acute coronary syndromes. Several invasive and noninvasive imaging techniques are available to assess athero-thrombotic vessels.

Most of the standard techniques identify luminal diameter or stenosis, wall thickness, or plaque volume (such as multi-slice CT, angiography, IVUS, etc.); however, none are effective in determining the plaques that are unstable and vulnerable to thrombosis and proliferation. In vivo, high-resolution, multi-contrast, magnetic resonance imaging (MRI) holds the best promise of non-invasively imaging vulnerable plaques and determination of the different plaque components such as lipid core, fibrosis, calcifications and thrombosis deposits in all arteries including the coronary arteries.

The MR findings have been extensively validated against pathology in ex vivo studies of carotid, aortic, and coronary artery specimens obtained at autopsy. Subsequent work on imaging carotid arteries in vivo in patients referred for endarterectomy showed a high correlation with pathology and with previous ex vivo results.

A recent study in patients with plaques in the thoracic aorta showed that when compared to transesophageal echocardiography, plaque composition and size are accurately characterized and measured using in vivo MRI. Carotid and aortic athero-thrombotic plaque assessment by MRI may lend itself to use as a screening tool for prediction of future cardiovascular events and for the evaluation of therapeutic intervention benefits.

These MR techniques have been also adapted for the study of plaques in different animal models. Therefore, MRI can be used as an investigative to follow in vivo progression, regression and plaque stabilization in different transgenic and non-transgenic animal models.

The ultimate goal is imaging of plaque in vivo in human coronary arteries. Preliminary studies in a porcine model of athero-thrombosis showed that the major difficulties of MR coronary wall imaging are due to the combination of cardiac and respiratory motion artifacts, the non-linear course of the coronary arteries, as well as their relatively small size and location.

Studies in an in-vivo pig model and in humans suggest that MRI may soon be applicable to study and characterize athero-thrombotic plaques in human coronaries in vivo. We have shown recently the utility of MRI in the study of treatment in humans. MR was used to measure the effect of lipid-lowering therapy (statins) in asymptomatic untreated hypercholesterolemic patients with carotid and aortic atherosclerosis.

In conclusion, the assessment of athero-thrombotic plaques by imaging techniques is essential for the identification of vulnerable plaques. In vivo, high-resolution, multi-contrast, MRI holds the best promise of non-invasively imaging vulnerable plaques and characterizing the different components in all arteries including the coronary arteries. MR allows serial evaluation assessment of the progression and regression of atherosclerosis over time. The use of specific MR contrast agents targeted for athero-thrombotic plaque imaging may enhance the plaque characterization. Application of MRI opens new areas for diagnosis, prevention, and treatment (e.g., lipid-lowering drug regimens) of athero-thrombosis in all arterial locations.

Roberto Corti, MD
Cardiology, University Hospital Zurich
Switzerland

Important: This press release accompanies both a presentation and an ESC press conference given at the ESC Congress 2003. Written by the investigator himself/herself, this press release does not necessarily reflect the opinion of the European Society of Cardiology