The role of advanced cardiac imaging methods in coronary artery disease

Abstract

Evaluation of the myocardial perfusion and the structures of coronary arteries with the use of various high technologies, such as advanced echocardiography, magnetic resonance tomography, spiral computed tomography as well as large spectrum of techniques of nuclear cardiology, gains more and more important significance in the diagnosis and management of coronary artery disease. Detection of coronary atherosclerosis and evaluation of early signs of myocardial hypoperfusion provide to select effective treatment modality. Nuclear cardiac studies are being frequently used in this field. In asymptomatic and intermediate likelihood patients, assessment of myocardial perfusion by single photon emission computed tomography (SPET) or positron emission tomography (PET) appears to be valuable even when coronary arteries are normal. Different imaging protocols and radiopharmaceuticals allow us to evaluate ventricular functions and myocardial metabolic state besides of myocardial perfusion. In this plane, definite successes are being achieved by PET and combined acquisitions by PET/CT and SPET/CT hybrid systems. Coronary computed tomography angiography (CTA) and myocardial perfusion imaging provide complementary information on vascular structure and myocardial perfusion. However, CTA with fast 16-slice or greater scanners may emerge as the initial test of choice. Myocardial perfusion studies would then be used if the CTA is not available or to assess how a stenosis defined by CTA effects coronary supply. Spiral computed tomography which allows to reveal calcium depositions in blood vessels has an important role in the detection of the severity and extent of atherosclerotic lesions. The use of multislice computed tomography in perspective might partially replace coronary angiography especially for assessing the degree of stenosis and patency of grafts. Magnetic resonance imaging (MRI) also has provided noticeable success in this era. Cardiac MRI clearly has the potential for this application and has already emerged as a highly effective method for assessing ventricular function, myocardial mass and myocardial viability. There is an increasing use of this approach for clinical rest and stress perfusion measurements. While cardiac MRI angiography (CMRA) has great promise as a radiation-free, it currently lags behind CTA for noninvasive coronary angiography. Further perfection of equipment and methodological approaches with the use of novel contrasts is necessary. In patients with coronary artery disease, multimodality applications covering both morphological and functional assessment are helpful for diagnosing and planning of therapeutic strategy. Recent developments in the field of ultrasonography have allowed us objectively quantify global and regional ventricular function, and to get real-time evaluation of coronary walls and lesions. While we achieve more knowledge about atherosclerotic lesions by using intravascular ultrasound technique, tissue Doppler imaging has given us attempt to provide a more objective assessment of myocardial function. Finally, although CTA and CMRA are likely to grow considerably in diagnostic evaluation over the next several years, myocardial perfusion studies with SPET and PET equipments will continue to be very valuable techniques for this purpose.