Background: Coronary filtration devices showed inadequate protection during PCI due to the inability to filter microemboli <120 μm in diameter. The purpose of this study was to determine the impact of two volumes of <120 μm microemboli on LV function, perfusion and viability using magnetic resonance imaging (MRI).
Methods: Under X-ray guidance, pigs (n = 18) received two different volumes (16 mm(3) or 32 mm(3)) of 40-120 μm microemboli (intracoronary). At 3 days, regional myocardial perfusion and LV function were assessed using first pass perfusion and cine MRI. Viability MRI was performed in beating and non-beating hearts to delineate microinfarcts and compare with histochemical triphenyltetrazolium chloride stain, using semi-automatic threshold method. Histology and cardiac injury enzymes were used to confirm the presence of microinfarcts and characterize cellular and vascular changes.
Results: Microinfarcts were visible as enhanced specks on DE-MRI in all animals that received 32 mm(3), but only two-third of the animals that received 16 mm(3), volume. The decline in ejection fraction and increase in LV volumes and microinfarcts were volume dependent. Regional perfusion and contractility were significantly reduced in the LAD territory compared with remote myocardium. Histology showed apoptosis, edema, inflammation and vascular thrombosis.
Conclusions: Microemboli of <120 μm have deleterious effects on LV function, perfusion and viability and the effects are dependent on microemboli volume. Microinfarct visualization is crucial to ensure that myocardial dysfunction is related to dislodged microemboli and not only to pre-procedural stunning or hibernation. This noninvasive MRI method may help in evaluating the effectiveness of coronary filtration devices in protecting myocardium from microemboli.
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