Myocardial Perfusion and Function: Comparative assessment by ECG, SPECT and MRI
Abstract: Evaluation of myocardial perfusion and function is important in management of patients with suspected or known coronary artery disease. This thesis focuses on the use of common diagnostic methods, myocardial perfusion single-photon emission computed tomography (MPS) and electrocardiography (ECG), to enhance and validate the diagnostic information. Cardiac magnetic resonance imaging (MRI) was used as the gold standard in 2 of the 4 studies. In the first 2 studies, MPS was performed during percutaneous transluminal coronary angioplasty (PTCA). The perfusion territories of each artery extended outside the typical borders (Paper I). This is important knowledge for correct interpretation of single- or multivessel disease. Summed ST-segment deviations during artery occlusion correlated with perfusion defects quantified by MPS (Paper II). The largest ST-segment deviation during occlusion of the left circumflex coronary artery was depression in lead V2. It is therefore essential to also consider ST-segment depression when diagnosing myocardial infarction. ECG-gated SPECT measures left ventricular volumes in addition to myocardial perfusion. Study III showed good agreement between gated SPECT and MRI for ventricular volumes and ejection fractions, indicating that the method is robust enough to guide clinical management. MPS is sometimes complicated by attenuation artifacts that mimic infarction. Its specificity was increased by performing prone imaging in addition to the traditional supine imaging (Paper IV), given that none of the patients whose defect disappeared in prone positioning had myocardial infarction by MRI.
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