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A Journal on Nuclear Medicine and Molecular Imaging
Affiliated to the and to the International Research Group of Immunoscintigraphy
Indexed/Abstracted in: Current Contents/Clinical Medicine, EMBASE, PubMed/MEDLINE, Science Citation Index (SciSearch), Scopus
Impact Factor 2,413
Christophe VAN DE WIELE 1, 2, 3, Adriana RIMBU 3, Tarik BELHOCINE 4, Bart DE SPIEGELEER 5, Mike SATHEKGE 6, Alex MAES 1, 7
1 Department of Nuclear Medicine, AZ Groeninge, Kortrijk, Belgium; 2 Department of Radiology and Nuclear Medicine, University Ghent, Ghent, Belgium; 3 Centre André Dutreix, NUCLERIDIS, Dunkerque, France; 4 Biomedical Imaging Research Centre (BIRC), Western University, London, Ontario, Canada; 5 Department of Pharmaceutical Analysis, University Ghent, Ghent, Belgium; 6 Department of Nuclear Medicine, University of Pretoria, Pretoria, South-Africa; 7 Department of Morphology and Medical Imaging, University Hospital Leuven, Leuven, Belgium
In approximately 10-30% of patients presenting with angina complaints, normal or non- obstructive coronary arteries are found on angiography. In this review paper, available literature on the underlying pathophysiological substrate explaining these discrepancies is reviewed. Both histological studies as well as studies using intravascular ultrasound e.g. the PROSPECT trial, show that epicardial coronary vessel significant lumen stenosis may be delayed until a plaque occupies 40% of the internal elastic lamina area. Limited available data suggest that these angiographically undetectable plaques are associated with an abnormal vasodilation capacity of the coronary circulation and may results in reversible perfusion defects on MPI. Organic non-atherosclerotic causes of epicardial coronary artery disease such as anomalous coronary arteries that course between the aorta and pulmonary artery, myocardial bridging and coronary vasospasm may also contribute to MPI results suggesting the presence of ischemia in the presence of normal coronary arteries on coronary angiography. Additional causes of reversible perfusion defects on MPI in the presence of a normal coronary angiogram are intra-ventricular conduction disturbances. The existence of reversible perfusion defects in the anteroseptal region in most of the patients suffering from LBBB on MPI following physical exercise as stressor is well documented. As the observed reduced septal uptake of both 201Tl and 99mTc-sestamibi/tetrofosmin in LBBB reflects coronary autoregulation in response to lower oxygen demands, not surprisingly, dipyridamole which uniformly exploits flow reserve, has proven more accurate for the diagnosis of CAD in patients suffering from LBBB. Although patients with a permanent ventricular pacemaker have a similar conduction abnormality as patients presenting with a LBBB, most of the defects found on MPI imaging in this patient population ( in up to 78% of patients with a normal coronary angiogram that area continuously paced) are localized in the inferoposterior (71%), apical(50%) and inferoseptal (28%) wall; coronary flow velocities in the LAD and dominant coronary artery and coronary flow reserve are also significantly lower when compared to a control group. Contrary to what is seen in LBBB patients, dipyridamole stress does not significantly reduce the incidence of abnormalities found but limits the defects to the inferior wall. Furthermore, the frequency of abnormalities found on MPI increases over time with right ventricular outflow tract pacing. Previous histologic studies have shown that microvessel disease is often accompanied by a slow-flow phenomenon reflecting decreased resting flow velocity. Thus, not surprisingly, MPI reversible abnormalities in the presence of a normal coronary angiogram have been reported in a wide variety of diseases characterized by microvessel disease such as diabetes, systemic lupus erythematosus, Behçet’s disease and metabolic syndrome. In these patients, low adiponectin and high lipoprotein(a) levels are found which are known to be associated with endothelial dysfunction, atherosclerosis and coronary artery disease. Furthermore, in these patients , limited available data suggest that reversible perfusion defects on MPI confer a significantly poorer prognosis both in terms of hard event rate (MI and cardiac death) and total event rate (MI, cardiac death or late revascularization). It is thus suggested that MPI could discriminate patients with a more severe prognosis. Finally, physical training in patients with primary microvascular angina appears to be associated with reduction of myocardial perfusion abnormalities.