Abstract Objectives. To investigate whether coronary microemboli have long-term effects on left ventricular (LV) function in an experimental model. Furthermore, to determine if first-pass perfusion and late gadolinium enhancement (LGE) patterns differs between small- and large-sized microemboli. Design. Six pigs underwent left anterior descending (LAD)-coronary microembolization with small-sized (40-120 μm, n∼250 000) microemboli using a combined x-ray and MRI-system. MR-images before, one hour after and 7-8 weeks after microembolization were obtained. Results were compared to MRI obtained by large-sized (100-300 μm, n∼7200) microemboli. Results. Cine MRI showed an acute drop in ejection fraction (from 49.5 ± 2.6% to 32.5 ± 2.8) that substantially recovered at 7-8 weeks (47.5 ± 3.2%). Regional LV-function assessed as circumferential, longitudinal and radial strain declined in both microinfarcts and remote regions followed by partial recovery at 7-8 weeks. The decline in LV function and the severe perfusion deficit from the small microemboli was similar to the large microemboli at one hour. There was a significant recovery in perfusion at 7-8 weeks in the microinfarcts. LGE demonstrated the microinfarcts at 7-8 weeks but not at one hour and the microinfarcts were confirmed by histopathology. Conclusion. Microembolization causes long-term, regional LV dysfunction and this study confirmed the need of a comprehensive MRI-protocol for the detection of microinfarcts. These findings suggest that even small microemboli (40-120 μm in diameter), which may escape the distal protective devices influence cardiac function.
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