利用CT进行冠状动脉造影并未得到充分应用

Prasad等人并未探讨近期关于心脏计算机断层成像（简称CT）的进展。利用多探头CT进行冠状动脉造影，是几年来无创心脏病学最为重要的进展。作者关于当前应用的无创心脏影像模式的优缺点的评价值得怀疑。     

Prognostic value of coronary multidetector CT angiography in patients with an intermediate probability of significant coronary heart disease

The aim of this study was to determine the prognostic value of coronary multidetector CT angiography (MDCTA) in patients with an intermediate pre-test probability of significant coronary artery disease (CAD). Patients who underwent 64-slice coronary MDCTA and met the selection criteria were identified and assessed for intermediate pre-test probability. Coronary MDCTA scans were preceded by calcium scoring, whereas all MDCTA scans were interrogated for the presence of plaque composition and the distribution and degree of stenosis. Significant stenosis was classified as being >50% of the luminal diameter. All patients were followed up for the occurrence of (i) cardiac death, (ii) non-fatal myocardial infarction, (iii) unstable angina requiring hospital admission and (iv) revascularisation. 138 patients were included (follow-up of 19.9 months); of these, 8 had a cardiac event (all revascularisations) and all had a positive coronary MDCTA. Patients with normal coronary arteries or non-significant stenosis suffered no cardiac events during follow-up. There were significant differences between the two groups regarding the presence of significant stenosis (p<0.001), the presence of plaque (p = 0.011) and a calcium score >10 (p = 0.003); 36.4% of patients with significant stenosis underwent revascularisation. In conclusion, this is the first UK study to investigate survival data in a population of intermediate-risk patients with no prior history of CAD who were investigated with coronary MDCTA. Coronary MDCTA can confidently rule out significant CAD in the intermediate-risk population and guide risk factor modification in patients with demonstrated coronary atheroma.The aim of this study was to evaluate patients with an intermediate pre-test probability of significant coronary artery disease (CAD) using multidetector CT angiography (MDCTA) and to follow them up for cardiac events. The risk factor profile was determined for all patients. In our institution, patients at high risk of significant CAD are frequently referred directly for invasive catheter angiography (ICA); those at low risk do not require imaging. Intermediate-probability patients, however, who represent a large proportion of patients seen in the outpatient setting, need further testing, and risk is determined by clinical review and risk factor assessment [1, 2]. Exercise testing, stress echocardiography and myocardial perfusion with single positron emission CT (SPECT) studies are all well-established non-invasive methods for the investigation of this group. However, the sensitivity and specificity for significant CAD are less than ideal. Meta-analysis of the literature pertaining to these non-invasive methods quotes exercise testing as having a sensitivity and specificity of 68% and 77%, respectively [3], stress echocardiography a sensitivity and specificity of 85% and 77%, respectively, and myocardial perfusion a sensitivity and specificity of 87% and 64%, respectively [4] (the definition of significant CAD varies within these meta-analyses and includes angiographic definitions of both 50% and 75% luminal narrowing being deemed significant). Often, these patents undergo ICA to rule out CAD as a result of an abnormal SPECT or stress echo, thus lengthening the patient journey and resulting in further irradiation. The development of MDCTA has provided an alternative algorithm for the investigation of this patient group. Studies that have compared MDCTA with ICA as the gold standard have shown the sensitivity to be between 93% and 99% and specificity to be between 95 and 98%, with a negative predictive value of 99–100% [5–8], all of whese values are superior to those of the other non-invasive modalities mentioned above. The prognostic outcomes backing up these data have until recently been lacking. However, recent prognostic studies looking at all-cause mortality [9] and cardiac events [10] reinforce the use of coronary MDCTA as a non-invasive diagnostic modality and also indicate that MDCTA data improve the prognostic assessment over baseline clinical risk factor assessment.     

Radiation-reduction strategies in cardiac computed tomographic angiography

Ionizing radiation has long been known to increase the risk of cancer. X-rays and γ-rays are officially classified as a carcinogen by the World Health Organization's International Agency for Research on Cancer.(1) Of the 5 billion imaging investigations performed worldwide two-thirds employ ionizing radiation.(2) Diagnostic x-rays are the largest man-made source of radiation exposure to the general population, and computed tomography (CT) represents the largest proportion of these.(3) Diagnostic CT has seen a dramatic increase in applications in the last two decades, not least in the higher dose applications. Whilst the increased use of CT has undoubtedly been of patient benefit, it inevitably will be associated with an increase in malignancy due to medical exposure. In fact a recent study from the USA has estimated that the CT examinations performed in 2007 could result in 29,000 future cancers based on current risk estimations.(4) Whilst the numbers in the UK will be less (only 4 million examinations are performed compared to 70 million), it is clear that it is the responsibility of all radiologists to carefully examine their CT techniques and protocols with the aim to reduce the dose of examinations without compromising their accuracy. Cardiac computed tomographic angiography (CTA) initially was a very high dose application. However, both clinicians and CT system manufacturers have done a large amount of work to reduce dose. Dramatic changes have been achieved and the aim of this review is to highlight these. However, such developments are not exclusively applicable to cardiac CTA and many can be utilized in CT in general.     

16-detector row computed tomographic coronary angiography in patients undergoing evaluation for aortic valve replacement: comparison with catheter angiography

AIM: To evaluate the diagnostic accuracy of 16-detector row computed tomography (CT) in assessing haemodynamically significant coronary artery stenoses in patients under evaluation for aortic stenosis pre-aortic valve replacement. SUBJECTS AND METHODS: Forty consecutive patients under evaluation for severe aortic stenosis and listed for cardiac catheterization before potential aortic valve replacement underwent coronary artery calcium (CAC) scoring and retrospective electrocardiogram (ECG)-gated multi-detector row computed tomographic coronary angiography (MDCTA) using a GE Lightspeed 16-detector row CT within 1 month of invasive coronary angiography (ICA) for comparative purposes. All 13 major coronary artery segments of the American Heart Association model were evaluated for the presence of > or =50% stenosis and compared to the reference standard. Data were analysed on a segment-by-segment basis and also in "whole patient" terms. RESULTS: A total of 412/450 segments from 35 patients were suitable for analysis. The overall accuracy of MDCTA for detection of segments with > or =50% stenosis was high, with a sensitivity of 81.3%, specificity 95.0%, positive predictive value (PPV) 57.8%, and negative predictive value (NPV) 98.4%. On a "whole-patient" basis, 100% (19/19) of patients with significant coronary disease were correctly identified and there were no false-negatives. Excluding patients with CAC >1000 from the analysis improved the accuracy of MDCTA to: sensitivity 90%, specificity 98.1%, PPV 60%, NPV 99.7%. CONCLUSION: Non-invasive 16-detector row MDCTA accurately excludes significant coronary disease in patients with severe aortic stenosis undergoing evaluation before aortic valve replacement and in whom ICA can therefore be avoided. Its segment-by-segment accuracy is improved further if CAC>1000 is used as a gatekeeper to MDCTA.