Non-invasive imaging of coronary artery disease and its functional consequences- The Hybrid SPECT and CCTA approach

For several decades invasive coronary angiography (CA) has been the reference standard in the assessment of coronary artery disease (CAD) severity. Patients with high pre-test likelihood of CAD, receive a Class 1 indication for CA. Several factors, however, motivate the need for a reliable non-invasive imaging modality, especially in patients with a high pre-test likelihood. Not only to rule out, but also to reliably diagnose coronary stenosis with functional consequences (significant CAD) and guide therapeutic decision making. Performance of CA in all patients with high pre-test likelihood of CAD has undeniable drawbacks. First of all, the prevalence of angiographically significant CAD in patients with high pre-test likelihood may be as low as 44-46%. In real life, the prevalence of significant CAD in patients referred for CA is even lower at only 36.7%, according to the national cardiovascular data registry of the United States . Secondly, angiographic severity of CAD does not reliably predict its main functional consequence: myocardial ischemia 6-8. Because evidence of myocardial ischemia is needed before deciding whether revascularization is necessary, additional (non- ) invasive tests are needed . Finally, CA comes with high costs as a result of the need for admission to a hospital or day-care facility and a low risk (0.1%) of serious adverse events . With the advent of computed tomography coronary angiography (CCTA) and the known reliability of single photon emission computed tomography myocardial perfusion imaging (SPECT-MPI) a combination of non-invasive imaging modalities became available that potentially could reliably diagnose significant CAD. The high diagnostic accuracy of this combination has previously been shown in highly selected patient populations. Nevertheless, data demonstrating the applicability of hybrid SPECT and CCTA in diagnosing significant CAD in stable patients with an intermediate to high pre-test likelihood of CAD are still lacking. Furthermore, the contribution of these tests to therapeutic decision making in these patients is unknown. Providing evidence on both of these issues is the main objective of this thesis.

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