64 Slice multi-detector row cardiac CT

Efficiency and safety of coronary CT angiography compared to standard care in the evaluation of patients with acute chest pain: a Canadian study

The optimal assessment of patients with chest pain and possible acute coronary syndrome (ACS) remains a diagnostic dilemma for emergency physicians. Cardiac computed tomographic angiography (CCTA) may identify patients who can be safely discharged home from the emergency department (ED). The objective of the study was to compare the efficiency and safety of CCTA to standard care in patients presenting to the ED with low- to intermediate-risk chest pain. This was a single-center before-after study enrolling ED patients with chest pain and low to intermediate risk of ACS, before and after implementing a cardiac CT-based management protocol. The primary outcome was efficiency (time to diagnosis). Secondary outcomes included safety (30-day incidence of major adverse cardiovascular events (MACE)) and length of stay in the ED. We enrolled 258 patients: 130 in the standard care group and 128 in the cardiac CT-based management group. The cardiac CT group had a shorter time to diagnosis of 7.1 h (IQR 5.8-14.0) compared to 532.9 h (IQR 312.8-960.5) for the standard care group (p < 0.0001) but had a longer length of stay in the ED of 7.9 h (IQR 6.5-10.8) versus 5.5 h (IQR 3.9-7.7) (p < 0.0001). The MACE rate was 1.6 % in the standard care group and 0 % in the cardiac CT group. In conclusion, a cardiac CT-based management strategy to rule out ACS in ED patients with low- to intermediate-risk chest pain was safe and led to a shorter time to diagnosis but increased length of stay in the ED.

128-Slice dual source coronary CTA: defining optimal arterial enhancement levels

This study aims to correlate coronary artery enhancement levels with quality of vessel visualization and calcified plaque visualization using a 128-slice dual-source CT (DSCT) scanner. Coronary CT angiography exams from 52 patients, mean age of 55 years (range, 22-90) and mean weight of 184 lbs (range, 120-320 lbs), were reviewed retrospectively. Contrast infusion rates ranged from 4.5 to 7 mL/s (mean, 5.8 mL/s). Postcontrast density of the largest calcified plaque and postcontrast density of the left main (LM) and right coronary arteries (RCA) were recorded. Enhancement quality was graded as 1=suboptimal, 2=adequate for diagnosis, and 3=excellent. Pre- and postcontrast acquisitions were compared for calcified plaque conspicuity. The largest calcified plaque density was a mean of 862 HU (range, 376 to 1,384 HU) on the postcontrast scan. The mean LM and RCA coronary artery enhancement levels for studies of excellent enhancement quality (N=43) were 468 and 457 HU, respectively, higher than mean enhancement levels of 320 and 322 HU for adequate enhancement quality (N=8) (p<0.0001 and 0.009). One study was graded as a nondiagnostic enhancement quality. Twenty-five subjects had calcified plaque, 3/8 with adequate and 22/43 with excellent enhancement quality. At least one calcified plaque measuring <2 mm was isodense to contrast enhancement on axial images in 5/25; all five were in the highest enhancement quality group. High coronary artery enhancement quality using 128-DSCT is associated with mean proximal coronary artery enhancement levels over 400 HU. High levels of enhancement may obscure small, calcified plaques.

X-ray computed tomography of the heart

INTRODUCTION

Cardiac imaging is an emerging application of multidetector computed tomography (MDCT). This review summarizes the current capabilities, possible applications, limitations and developments of cardiac CT.

SOURCES OF DATA

Relevant publications in peer reviewed literature and national and international guidelines are used to discuss important issues in cardiac CT imaging.

AREAS OF AGREEMENT AND CONTROVERSY

There is broad consensus that coronary CT angiography is indicated in patients with an intermediate pre-test probability of coronary artery disease (CAD) when other non-invasive tests have been equivocal. In this context, CT can reliably exclude significant CAD. Cardiac CT also has an established role in the evaluation of bypass grafts and suspected coronary anomalies. Radiation exposure from CT procedures remains a concern, although techniques are now available to reduce the X-ray dosage without significantly compromising the image quality. However, with the current level of knowledge, the cardiac CT examinations are not justified to screen for CAD in asymptomatic individuals. Neither is it considered appropriate in patients with a high pre-test probability of CAD, for whom invasive catheter coronary angiography is usually of more benefit.

GROWING POINTS AND AREAS TIMELY FOR DEVELOPING RESEARCH

The ability to reconstruct the volumetric cardiac CT data set opens up avenues for advanced physiological analyses of the heart. For example, if CT myocardial perfusion assessment becomes a reality, there is potential to revolutionize the practice of MDCT imaging. Research is also ongoing to investigate whether cardiac CT has a role in the appropriate triage of patients with chest pain in the emergency department.

Coronary CTA: stenosis classification and quantification, including automated measures

The development of larger multidetector computed tomography (CT) systems has allowed increased accuracy in quantifying obstructive lesions involving the coronary arteries. This article reviews the accuracy of coronary CT angiography (CTA) in quantifying obstructive lesions, evaluating the extent of coronary artery disease, and classifying the composition of coronary plaques. In addition, several outcomes studies and some promising automated techniques for quantifying coronary CTA are reviewed.