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<strong>KCE</strong> Reports 82 Multislice CT in Coronary Heart Disease 63<br />
insight in <strong>the</strong> functional importance of <strong>the</strong> coronary lesion thus documented. Some<br />
studies indicated that less than half of <strong>the</strong> significant lesions on MSCT have<br />
hemodynamic consequences. 111, 159 The lack of functional information being provided by<br />
both CCA and MSCT is a major limitation. Ideally, any patient with (atypical) chest pain<br />
in whom diagnostic imaging is deemed appropriate (i.e. a patient in whom one expects -<br />
if CAD is present - that revascularisation will improve symptoms or prognosis), should<br />
undergo a functional test before proceeding to an anatomic imaging test. 160 If <strong>the</strong><br />
functional examination leads to <strong>the</strong> decision that revascularisation is appropriate, one<br />
should go for invasive CCA, enabling immediate <strong>the</strong>rapeutic intervention, and obviating<br />
<strong>the</strong> need for MSCT. If <strong>the</strong> functional exam leads to a decision that revascularisation is<br />
not appropriate, no fur<strong>the</strong>r diagnostic imaging steps are needed. If noninvasive<br />
functional tests are impossible to be performed or inconclusive, MSCT may be<br />
efficacious, but <strong>the</strong>se populations have not been studied so far. Yet, invasive functional<br />
evaluation (functional flow reserve) will often be needed. 28<br />
In summary, because MSCT has limited ability to define myocardium jeopardized by<br />
ischemia, its potential for predicting benefit from revascularisation is limited. 111<br />
8.5 PATIENT OUTCOMES<br />
The real issue of diagnosing CAD is not to correctly identify coronary artery stenoses<br />
but to help in predicting and improving patients’ outcome. In this respect, coronary<br />
artery imaging may be misleading: significant though prognostic benign lesions may be<br />
identified and lead to inappropriate interventions, because <strong>the</strong>y do not affect blood<br />
supply to <strong>the</strong> myocardium or <strong>the</strong>y can be left untreated (i.e. not revascularised). In<br />
patients with stable angina pectoris, PCI as <strong>the</strong> first <strong>the</strong>rapeutic option does not reduce<br />
<strong>the</strong> risk of death, myocardial infarction or o<strong>the</strong>r major cardiovascular events when<br />
added to optimal medical <strong>the</strong>rapy. 2 This means that myocardial revascularisation (and<br />
hence both invasive or noninvasive angiography) can be safely deferred in <strong>the</strong>se patients<br />
and can be restricted to those in whom medical <strong>the</strong>rapy does not lead to symptom<br />
control. In <strong>the</strong> latter event, cardiologists will immediately proceed to CCA, enabling<br />
<strong>the</strong>m to intervene during <strong>the</strong> same procedure, obviating <strong>the</strong> need for a preliminary<br />
MSCT.<br />
Coronary artery imaging can also be misleading because low grade stenoses may be<br />
prone to plaque rupture and may lead to serious clinical events, yet <strong>the</strong>y may be<br />
2, 152<br />
regarded as innocent.<br />
8.6 COST-EFFECTIVENESS<br />
Economic evaluations of interventions with unproven clinical effectiveness are not very<br />
useful. An intervention should prove clinically effective first before it can be considered<br />
cost-effective. Several researchers, however, have attempted to build an economic<br />
model to assess <strong>the</strong> cost-effectiveness of MSCT relative to a suitable comparator. All of<br />
<strong>the</strong>se models suffer from lack of evidence about <strong>the</strong> relevance of MSCT for improving<br />
patient outcomes. Therefore, <strong>the</strong>y are necessarily limited to an assessment of <strong>the</strong> costper-case<br />
detected. And even <strong>the</strong>se results can be questioned, as sensitivity and<br />
specificity of MSCT has not yet been tested in real-world populations where <strong>the</strong><br />
prevalence of clinically significant CAD is low.<br />
Never<strong>the</strong>less, a cost-outcome description by Goldstein et al. is frequently cited to<br />
demonstrate <strong>the</strong> technology’s cost-effectiveness. While this study did include clinical<br />
parameters about <strong>the</strong>rapeutic impact, <strong>the</strong>se were not taken into account in <strong>the</strong> costeffectiveness<br />
analysis. A simple exercise, extending <strong>the</strong> cost and outcome (QALY)<br />
calculation to include treatments following <strong>the</strong> diagnosis of CAD showed that from<br />
hospitalisation up to 6 months of follow-up, a diagnostic strategy with MSCT was more<br />
costly and led to a higher loss in QALYs than a standard diagnostic strategy without<br />
MSCT. The results need to be interpreted with caution, as this RCT was actually<br />
underpowered to draw <strong>full</strong> economic conclusions.<br />
Fur<strong>the</strong>r studies on <strong>the</strong> diagnostic efficacy of MSCT are needed. Until <strong>the</strong>n, results of<br />
cost-effectiveness analyses remain inconclusive.