Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3752_Библиотеки_им_академика_М_И_Перельмана

The combination of various methods that limit exposure permit to perform coronary CTA with doses well below 1 mSv (see Fig. 9.3 ). This is clinically possible with high- end hardware in somewhat selected patients (low heart rate and reasonable body weight) [ 17 ]. There are published series that demonstrated high accuracy for stenosis detection using such protocols [ 20 , 21 ]. In a very strictly selected patient cohort, it has even been reported that doses below 0.1 mSv are possible [ 10 ], but image quality at this extreme end of the spectrum is not good and robust enough for routine clinical practice.

In most cases, coronary CT angiography is performed to detect or rule out signifi cant coronary artery stenoses (See Fig. 9.4 ). In most cases, presence of a “signifi cant” luminal stenosis is assumed when the diameter reduction of the coro­nary lumen appears to be more than 70 %. Stenosis severity is usually determined my visual estimation, since quantita­tive approaches are not exact – the spatial resolution of coro­nary CT angiography, approximately 0.5 mm, is not suffi cient to allow for accurate, quantitative stenosis grading. In fact, visual estimation of stenosis degree has no downsides as compared to quantitative approaches [ 26 – 28 ]. Stenosis severity in CT can appear to be less or more than invasive angiography – the typical margin of agreement is approxi­mately ±20 % [ 27 ]. Hence, stenoses that appear to be less than 50 % in CT can be expected to be less than 70 % in invasive angiography with a very high degree of certainty. In most cases, however, there is a tendency to over estimate, rather than underestimate, the degree of luminal stenosis in coronary CT angiography as compared to catheter-based invasive coronary angiography (Fig. 9.5 ). Often, high grade coronary artery stenoses appear as complete or near- complete interruptions of the coronary artery lumen in the CT data set (Fig. 9.6 ). Categories of stenosis severity that are recom- mended for use in coronary CT angiography reports care listed in Table 9.2 [ 24 ]. The differentiation between com- plete coronary artery occlusions and high-grade stenoses can be diffi cult in coronary CT angiography. Very long lesions typically correspond to complete occlusions (Fig. 9.7 ), while shorter lesions can either be secondary to high grade luminal

A large meta-analysis of trials that compared coronary CT angiography to invasive coronary angiography for ste­nosis detection in a total of 3764 patients yielded a patient­based sensitivity of 98 % and specifi city of 82 % to identify

disease, but for clinical reasons require further workup to rule out signifi cant coronary stenoses. A negative coronary CT angiography will obviate the need for further testing. Indeed, several observational trials clearly demonstrated that

Based on the same registry, Shaw et al. analyzed the rela­tionship between coronary CTA results, invasive coronary angiography, and subsequent mortality [ 49 ]. They found that in patients without any obstructive stenosis in coronary CTA, performing invasive coronary angiography was associated with a relative hazard for death of 2.2 (p = 0.011), while in patients with obstructive stenosis in coronary CTA, invasive angiography was associated with a relative hazard for death of 0.61 (p = 0.047). Min et al. reported that a benefi t of revas­cularization was only present in patients with high-risk anat­omy in coronary CTA (at least two-vessel coronary artery disease with involvement of the left anterior descending coronary artery, three-vessel coronary disease or left main stenosis) [ 50 ]. Revascularization was associated with a haz- ard ratio for death of 0.38 (95 % CI: 0.18–0.83) in patients with “high-risk CAD” in coronary CTA, but there was no survival difference in patients without “high-risk CAD” in coronary CTA (hazard ratio 3.24 with a 95 % CI between

0.76 and 13.89). Thus, suffi cient data is available that coro­nary CTA is an excellent prognostic tool and that it is safe to avoid any further testing in chest pain patients if coronary CT angiography demonstrates the absence of coronary artery stenoses.

elevation [ 51 ], and that outcome is excellent if CT demon- strates the absence of coronary stenosis in acute chest pain patients [ 52 – 59 ]. A cost advantage of incorporating CT angi- ography in the workup of low-likelihood acute chest pain patients as compared to the standard of care has been demon­strated [ 54 ]. Most trials of coronary CTA in acute chest pain patients can justifi ably be criticized for including very low­risk patients [ 60 ], but their results can likely be extrapolated to patients with somewhat higher risk. In fact, both US [ 61 ] and European guidelines on acute coronary syndromes incorporate coronary CT angiography as a useful tool to rule out stenosis in patients with low-risk acute chest pain [ 62 ]. As for other applications, coronary CT angiography should be considered in acute chest pain patients only if patient characteristics promise full evaluability and high image quality [ 62 ].

fl uid dynamics are applied to model the fl ow and resistance pattern under adenosine stress and to obtain the FFR value for all segments of the coronary artery tree Initial publica­tions show that this is feasible, and can improve the speci­fi city of CT to identify ischemia causing lesions over a purely anatomic assessment alone. However, further vali­dation will be necessary.