Noninvasive evaluation of the prevalence of noncalcified atherosclerotic plaques by multi-slice detector computed tomography: results of a pilot study

Abstract

Background: Multi-slice detector computed tomography (MDCT) not only allows for the determination of coronary calcifications, but also for the noninvasive visualization of noncalcified plaques. Thus, coronary artery disease (CAD) can be detected at a fairly early stage. Since data on the prevalence of potentially rupture prone noncalcified coronary lesions are still missing, it was aim of the present investigation to study this in patients with a distinct cardiovascular risk profile, but without known CAD. Methods: 68 patients with clinical suspicion of CAD and multiple cardiovascular risk factors were included in this prospective study. Calcium scoring, as well as the detection of noncalcified plaques were performed using a Somatom VZ scanner (Siemens™, Forchheim, Germany). Results: Calcium scoring could be performed in all patients on native scans; 63/68 (96%) of contrast enhanced scans showed sufficient image quality to perform a screening for noncalcified plaques. The three scans without diagnostic image quality had been performed at heart rates of 95±18/min. Coronary calcifications were found in 36/65 (55%) patients (Agatston score: 247±358). Additional noncalcified plaques were detected in 16/36 (45%) of these patients; 29/65 (45%) patients had no coronary calcifications (Agatston score: 0), but noncalcified plaques could be detected in 3/29 (10%) of these patients. Conclusions: The prevalence of noncalcified plaques was 29% in the whole study group, and even in 10% of patients without coronary calcifications. Further prospective large scale studies are required to confirm these data, and to evaluate the clinical implication of this finding.

Introduction

Coronary artery disease (CAD) is still one of the leading causes of morbidity and mortality in the western world. Approximately 50% of all acute coronary syndromes (ACS) occur in patients (patients) without prior symptoms [1], [2]. Conventional coronary angiography is limited by its invasiveness and the inability to allow for a precise evaluation of the vessel wall [3]. Furthermore, it is usually only performed in patients who already show clinical signs of disease. Due to significant technical improvements in the last few years, different noninvasive imaging techniques were evaluated in the clinical setting [4], [5], [6], [7], [8].

Initial promising results with regard to detecting coronary atherosclerosis in its early stage have been reported for electron beam computed tomography (EBCT) [9], [10], [11], [12], [13]. A large number of experimental and clinical studies could demonstrate that EBCT is useful in detecting the presence of CAD by determining coronary calcifications [14], [15]. In addition to conventional risk factors, the amount of calcification is considered to be a useful marker for defining a patient’s relative risk for ACS [16].

However, not only EBCT scanners, but also conventional computed tomography scanners with multi-slice technology (MDCT) are nowadays used for noninvasive calcium scoring. Becker et al. could demonstrate the close correlation between EBCT and MDCT calcium scores [17], [18]. Major advantages of MDCT technology are its already broad availability, and the thinner slice-width in the high resolution protocol which is used for noninvasive coronary angiography [19]. By the use of MDCT, not only coronary calcifications, but also noncalcified plaques can be visualized in contrast enhanced coronary arteries noninvasively [20], [21]. We could recently demonstrate that density measurements within atherosclerotic coronary plaques might be used as a surrogate marker for plaque composition [22].

Since noncalcified plaques in particular are considered to play a crucial role in the development of ACS [23], it was aim of the present study to evaluate the prevalence of these plaques in patients without overt CAD, but cardiovascular risk profile.