Abstract
Development of cardiac imaging has empowered clinical practice with powerful tools for the management of coronary artery disease (CAD). While stress ECG, echocardiography and invasive coronary angiography maintain their well established positions in daily routine, a number of contemporary cardiac imaging methods reveal new horizons for minimally or non-invasive diagnosis of patients with coronary artery disease. This article gives a short overview of the role of coronary CT angiography (CTA), cardiac MRI, and nuclear medicine studies (hybrid single photon emission tomography with CT – SPET/CT and hybrid positron emission tomography with CT – PET/CT) in patients with different probabilities and forms of coronary artery disease. Based on our recent experience the advantages of each technique are reviewed and recommendations are given for appropriate use of any of these methods in our clinical settings.
In patients with suspected CAD the pretest probability of disease is the most important factor in selection of the imaging modality. CTA, MRI and SPET techniques are mostly recommended for patients with intermediate pretest probability of CAD. CTA provides information about coronary artery wall, lumen and plaque composition and enables reliable detection of significant coronary artery stenosis. Due to a very high negative predictive value, the major impact of CTA in the management of suspected CAD lies in reliable elimination of the possibility of coronary artery stenosis. MRI and SPET are useful techniques for detection of myocardial perfusion abnormalities, enabling early detection of stress-induced ischaemia. For patients with high pretest probability of CAD (with typical chest pain) invasive coronary angiography remains the initial method of choice.
In patients with known CAD myocardial SPET is recommended for the assessment of myocardial perfusion abnormalities and patient prognosis. In this group the high proportion of patients with extensive calcified coronary plaques complicates the accurate assessment of coronary artery stenosis in CTA. However, CTA enables reliable visualization of coronary bypass grafts, thus providing reliable detection of significant stenosis or graft occlusion and is the method of choice for this indication.
Myocardial perfusion SPET and MRI are recommended to assesshaemodynamic significance of coronary artery stenosis defined by CTA or invasive coronary angiography, because the presence of obstructive coronary artery lesion does not always result in myocardial ischemia. For viability assessment and prognostic evaluationMRI, SPET and PET are valuable techniques. They are particularly useful for identifying patients who would benefit most from revascularization. MRI is recommended due to its high spatial resolution that enables to detection of subendocardial infarcts and assessment of the transmural extent of myocardial damage. PET enables evaluation of myocardial metabolism and is considered a non-invasive “gold standard” for assessment of myocardial viability.
The role of SPET and PET in the management of CAD is emphasized in patients with renal impairment, because these techniques do not assume any use of nephrotoxic contrast agents.
The integration of PET and CT techniques (hybrid PET/ CT technology) provides an opportunity for defining the anatomic extent of coronary atherosclerosis and for evaluating myocardial damage during single examination. CTA, MRI, SPECT and PET techniques occupy an important position in the diagnostic work-up of patients with known or suspected CAD either by revealing the degree and location of stenosis or by assessing myocardial perfusion abnormalities and consequent myocardial damage. For the optimal benefit of the patient, close collaboration between imaging specialists and cardiologists remains an ultimate necessity.