The purpose of this study is to compare the diagnostic accuracy of hybrid imaging combining CTCA with low-dose stress-only SPECT vs. coronary angiography for detecting haemodynamic relevant coronary lesions; and second to determine the effects of PCI on cardiac perfusion, cardiac function and quality of life in patients with CTO lesion in left anterior descending (LAD) coronary artery.

Noninvasive imaging modalities have shown high diagnostic accuracy in the detection of coronary artery lesions, and for the estimation of their hemodynamic relevance.Thus, noninvasive assessment of myocardial perfusion defects may be preferred for patients with chronic total occlusion (CTO).

In particular, myocardial perfusion is measured with single photon emission CT (SPECT).Multislice coronary CT angiography (CCTA) with dual-source scanners reveals the anatomic location of coronary artery disease (CAD). These two techniques assess distinct aspects of heart morphology and function parameters of the heart, and should therefore be regarded as complementary rather than competing methods.Taking this into consideration, decisions regarding whether invasive revascularization therapy is adequate or not and which strategy is the best for long-term survival cannot be supported by anatomic information alone. Therefore, noninvasive complementary imaging of structure and perfusion, in conjunction with three-dimensional (3D) image fusion, has emerged as a technique for reliable allocation of perfusion defects to their supplying coronary artery.

Inclusion Criteria:

• Patients were eligible for enrolment in this study if coronary angiography showed a CTO (at least for 3 months and confirmed by angiography and/or history of earlier MI).

Exclusion Criteria:

• Hypersensitivity to iodinated contrast agent, cardiomyopathy, non-sinus rhythm, severe valvular heart disease, NYHA functional class IV heart failure at baseline, previous coronary bypass surgery, renal insufficiency, severe lung and liver disease or cancer.