Microembolization is common after coronary interventions, and therefore this MRI study aimed to quantify the effect of coronary microembolization on left ventricular (LV) function. The left anterior descending artery (LAD) was selectively catheterized in an XMR suite (Philips Medical Systems, Best, The Netherlands) in eight pigs to deliver MR contrast media to measure the LAD territory using first-pass perfusion and for intracoronary delivery of the embolic agent. Cine, tagged, and delayed contrast-enhanced MRI (DCE-MRI) was performed to assess LV volumes, ejection fraction, radial and circumferential strain, and viability at baseline, 1 h, and 1 week after microembolization. Histopathology and histochemical staining were used to characterize and measure the extent of microinfarction. The LAD territory was 35% +/- 2% LV mass. Patchy microinfarction on DCE-MRI at 1 week was 22.0% +/- 3.6% LAD territory (7.5% LV mass). Microembolization caused persistent decline in ejection fraction (baseline = 49% +/- 1%, 1 h = 29% +/- 1%, P = 0.02 and 1 week = 36% +/- 1%, P = 0.03) and increased end-diastolic (79.6 +/- 3.9 ml, 85.5 +/- 4.5 ml, P = 0.03 and 92.4 +/- 6.2 ml, P = 0.06, respectively) and end-systolic (40.8 +/- 2.1 ml, 60.2 +/- 3.4 ml, P = 0.02 and 59.3 +/- 4.8 ml, P = 0.03, respectively) volumes. The microembolized territory was manifested as dysfunctional regions for 1 week on cine and tagged MRI. Histopathology revealed occlusive microemboli surrounded by necrotic tissue undergoing repair. Microinfarction was visualized after coronary microembolization and caused LV dysfunction disproportionate to the size of myocardial damage. It also changed LV geometry and decreased radial and circumferential strain over the course of 1 week.