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12 Multislice CT in Coronary Heart Disease KCE Reports 82 Comparable figures are reported in the most recently published ACC/AHA guidelines for the clinical application of echocardiography. 13 From these data, we (crudely) calculated positive and negative LRs of 5.0 and 0.24 respectively. These figures 26, 27 correspond closely to those reported in more recent literature. 2.2.2.5 Summary of diagnostic accuracy of noninvasive diagnostic tests The diagnostic performance of noninvasive tests is summarised in Table 3. One should however be cautious to mutually compare them, because MPS and especially stress- ECG have been more thoroughly studied in larger and less selected populations than MSCT. Moreover the diagnostic value of ECG-stress-tests in clinical practice may be better than suggested in diagnostic studies, because information additional to the mere ECG data (chest pain during the test, maximal workload, blood pressure response) are mostly not taken into account in studies on the diagnostic performance of ECG stress testing. This is confirmed in the AHA/ACC guidelines on exercise testing which state that, taking into consideration age, gender, heart rate, maximum work load, and inducible symptoms, “appears to make exercise ECG and imaging procedures comparable”. 16 Table 3: Diagnostic accuracy of noninvasive tests SENS SPEC pos LR neg LR ref 95%CI 95%CI 95%CI 95%CI stress ECG 0,66 0,42-0,85 0,77 0,58- 0,88 1,83 1,48- 2,26 0,51 0,39- 0,67 14 dipyridamole MPS 0,92 0,76-0,93 0,74 0,54- 0,90 2,29 1,68- 3,12 0,25 0,17- 0,37 14 dobutamine stress ECHO 0,8 NA 0,84 NA 5 3,16- 7,92 0,24 0,16- 0,36 Calculated from 25 Sens: sensitivity, spec; specificity; pos and neg LR: positive and negative likelihood ratio Key points • Diagnosis of CAD can often be made by history taking alone, based on the pain characteristics and taking into account the patient’s age, gender and cardiovascular risk profile. • The aim of the additional noninvasive diagnostic tests discussed so far is twofold: (1) to better estimate the likelihood of CAD when baseline investigation is not decisive and (2) to indirectly estimate the risk for future events. • These tests not so much identify coronary artery stenoses by directly imaging the coronary tree, but rather assess the functional consequence of an impaired blood flow to the myocardium. In this way, they provide information that is additional to pure imaging techniques like coronary angiography and multislice CT. 2.2.3 Invasive testing: conventional coronary angiography (CCA) The only absolute way to anatomically document obstructive CAD is by means of cardiac catheterisation and coronary angiography by which contrast material is injected into the coronary arteries that are subsequently radiologicaly visualised. The invasive diagnostic examination can, if deemed necessary, be further extended by a therapeutic intervention during which the culprit coronary stenosis is dilated by means of a balloon (mostly combined with the insertion of a supporting stent) mounted on a catheter, i.e. the percutaneous coronary intervention or PCI. If PCI is not feasible, patients are referred for coronary artery bypass grafting (CABG). Although conventional coronary angiography (CCA) is considered the gold standard for assessing coronary stenosis, it is not a reliable indicator of the functional significance of a coronary stenosis and it is ineffective in determinating which plaques are likely to lead
KCE Reports 82 Multislice CT in Coronary Heart Disease 13 to an acute coronary event. 28 Therefore, and owing to the high cost and the potential complications, routine use of CCA without prior noninvasive testing is not advisable. 14 If noninvasive functional testing is not feasable, functional testing can be done invasively by means of pressure-derived fractional flow reserve (FFR) measurements. 28 This can be done immediately after the imaging procedure by intravascular pressure recordings through the catheter that was used for contrast injection into the coronary arteries. CCA is an invasive procedure, carrying a certain risk that is related to radiation exposure, the direct access of the heart and vascular structures and the administration of contrast media. The most serious complications of CCA are death (0.1–0.2%), nonfatal MI (0.1%) and cerebrovascular accidents (0.1%). 24 Allergic contrast reactions and renal failure may result from contrast medium exposure. Bleeding from vascular access sites (groin) may result in substantial bleeding, requiring transfusion and sometimes, vascular surgery is needed to repair the damage to the femoral artery. In addition, patients are temporarily subjected to bed rest, often staying overnight in hospital and delayed in returning to work. The composite rate of major complications associated with routine diagnostic catheterisation is between 1 and 2%. 4 It has been a matter of concern that in some series up to 50% of CCAs reveal normal coronary arteries or do not lead to revascularisation. Consequently, in order to try to avoid these “unnecessary” invasive procedures, there has been increasing interest in noninvasive imaging techniques. Some of the inconveniences and complications of CCA, related to the intravascular access by means of a catheter, can be avoided by using CT scanning for coronary artery imaging, which is the topic of further discussion in this report. Key points • Conventional coronary angiography (CCA) is considered the gold standard for assessing coronary anatomy. • It is however not a reliable indicator of the functional significance of a coronary stenosis indicating that the results of a functional test are necessary before proceeding to revascularisation. • Another limitation is that it carries risks related to radiation exposure, the direct access of the heart and the administration of contrast media. The most serious complications of CCA are death (0.1–0.2%), non-fatal MI (0.1%) and cerebrovascular accidents (0.1%) 2.3 DIAGNOSIS OF CAD IN ACUTE CONDITIONS Based on history taking and an electrocardiogram (ECG), a qualified physician must be able to assign a diagnosis of “ACS” or “highly unlikely ACS” within 10 minutes after the first medical contact. 29 In patients with an atypical history, negative clinical findings and a non-evolutive ECG, serum biomarkers are useful in diagnosing the cardiac origin of the patient’s complaints and in assessing prognosis. Troponins are the best biomarkers to predict short and long-term outcome (beyond 1 year) with respect to MI and death. 29 Even minor myocardial damage can be excluded based on two repetitive troponin measurements, one on admission and a second between 6 and12 hours later. Patients fulfilling the following criteria may be considered at low risk for future events and should not be submitted to early invasive evaluation: no recurrence of chest pain, no heart failure, no abnormalities on the first and a subsequent ECG and no elevation of troponins (at arrival and after 6 to12 hours). Patients who cannot be excluded by the above criteria should go on to cardiac catheterisation.
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KCE reports 33 Effects and costs of
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