Review the MPR images of a coronary artery shown below:
Which one of the following do the images indicate?
The images show mixed-morphology plaque within the LAD causing a significant stenosis.
The proximal plaque is of predominantly lower attenuation, with mild calcification and a further heavily calcified plaque just distal to a tight stenosis. A corresponding orthogonal plane through the stenosis is shown. Non-calcified plaque may represent fatty or fibrous plaque, or often a combination of the two.
Concerning plaque characterization, which one of the following is false?
CT can accurately differentiate between calcified and non-calcified plaque on the basis of the Hounsfield unit attenuation value. Studies have demonstrated a close correlation between plaque morphology as assessed on CT compared with IVUS, but CT cannot reliably differentiate lipid-rich from fibrous plaque given the significant overlap in appearance and limited spatial resolution. In addition, CT cannot yet identify vulnerable or inflammatory plaque, although some work has been done on carotid arteries using nuclear medicine techniques. CT is the best non-invasive modality for the detection of preclinical coronary artery disease as it delineates eccentric or shallow atheroma which has yet to cause significant luminal narrowing. In these cases, functional imaging in the form of stress MRI, stress echo, or nuclear myocardial perfusion would be negative because of the lack of ischaemia. IVUS is the reference standard for plaque detection and characterization, but has the disadvantage of being invasive and expensive. Conventional catheter angiography is essentially a two-dimensional ‘lumenogram’; an artery that has positively remodelled will have an atheromatous burden in the wall and therefore may look entirely normal.
Concerning aortic valve disease, which one of the following statements is true?
Whilst the assessment of valvular heart disease is traditionally the domain of echocardiography, CT can provide useful information regarding valve anatomy and to a degree function. Aortic valve planimetry has been shown to correlate closely with that of TOE. The degree of aortic valve calcification has been shown to correlate with the severity of aortic stenosis, but the relationship is not a simple linear one and as the extent of calcification increases, the correlation becomes less reliable. CT cannot directly or quantifiably assess valvular regurgitation. However, a number of indirect signs can be seen on CT, including a coaptation defect in the valve leaflets in diastole and a differential density of contrast in the left ventricle and left atrium in the presence of aortic regurgitation.
CT can be useful in the setting of aortic valve disease as it can be used to exclude significant coronary artery disease prior to aortic valve surgery and could save up to 50% of patients from needing preoperative catheter angiography. In the setting of aortic valve endocarditis, the presence of vegetations or an associated aortic root abscess may make invasive catheter angiography high risk and technically challenging. In the setting of valvular infection, CT can also delineate aortic root abscess cavities and pseudo-aneurysm formation, providing important anatomical data prior to surgery. Figure below (upper panel) shows a normal aortic valve (left) and a heavily calcified, thickened, and stenotic trileaflet aortic valve (right). The images in the lower panel show indirect signs of aortic valvular regurgitation with a coaptation defect (left) and differential contrast density in the left ventricle and left atrium (right).
A 55-year-old woman presents to the ED with recent-onset central chest pain presenting intermittently at rest, relieved by GTN, but not exacerbated by exertion. Her troponin I level and resting ECG are normal. She has no significant risk factors for coronary artery disease.
According to the NICE guidelines, what is the most appropriate subsequent management?
This patient has atypical angina. Given she has no risk factors for coronary artery disease, her pre-test probability of having coronary artery disease is 10%. The NICE guidelines advise that the management of patients with a pre-test probability of coronary artery disease of 10–29% should have a CT calcium score as the first-line investigation. NICE guidelines for chest pain of recent onset. Assessment and diagnosis of recent onset chest pain or discomfort of suspected cardiac origin, 2010. http://www.nice.org.uk/guidance/CG95.
A 78-year-old male ex-smoker was referred to the cardiology department with a history of COPD, dizziness, syncope, and exertional symptoms suggestive of angina. He had a suboptimal exercise tolerance test due to dyspnoea and could not tolerate dobutamine during stress echocardiography. He was referred for a cardiac CT. A CT coronary calcium score was performed first and this is shown below.
According to NICE guidelines, what is the most appropriate next step in management?
The patient has a high pre-test probability of coronary artery disease and should ideally have gone directly to catheter coronary angiography. His calcium score was >3000.
NICE guidelines suggest that invasive catheter angiography should be offered to patients with a coronary calcium score of >400, if appropriate, and patients who are being considered for revascularization.
A heavy coronary calcium burden predicts significant coronary artery disease and reduces the accuracy of CT coronary angiography because of the partial volume (‘blooming’) artefact.
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