Acute hyperenhancement on delayed contrast-enhanced magnetic resonance imaging is the characteristic sign after coronary microembolization.

BACKGROUND Detection of coronary microembolization is of clinical importance for patient management and prediction of long-term outcome. However, there are few studies of the changes of magnetic resonance imaging after coronary microembolization. This study was designed to investigate the imaging of the left ventricle using delayed contrast enhanced magnetic resonance imaging as well as the left ventricular ejection fraction after coronary microembolization in animal models. METHODS Eight miniswine, of either sex (body weight 21-25 kg), were used to make the coronary microembolization model. After coronary angiography, a 2.8F infusion catheter was placed in the left anterior descending artery with the tip located between the second and third diagonal branches. Microspheres with the diameter of 42 microm and mean dosage of 1.2 x 10(5) were selectively infused into the left anterior descending artery. First pass and stressed first pass perfusion scan were performed after cine images were acquired. Then a second bolus of 0.15 mmol/kg gadolinium DTPA was given at a rate of 2 ml/s. Ten minutes later, delayed contrast enhanced magnetic resonance images of the left ventricular wall were evaluated. Serum changes of tumor necrosis factor alpha (TNF-alpha) were evaluated by enzyme-linked immunosorbent assay (ELISA). RESULTS Hypoenhancement was not observed at first pass perfusion at the anterior wall of the left ventricle. Hyperenhancements of the anterior-septal and anterior wall of the left ventricle was in evidence on delayed enhancement images 6 hours after microembolization and disappeared one week later. The characteristic change of coronary microembolization on delayed contrast enhanced magnetic imaging was non-enhanced regions within the hyperenhancement zone. Left ventricular ejection fraction measured by magnetic resonance imaging decreased significantly from 0.451 +/- 0.063 at baseline to 0.362 +/- 0.070 at the sixth hour (P < 0.01), and recovered to 0.431 +/- 0.053 one week later (P < 0.01 vs 6th hour). Compared with baseline values, the left ventricular end systolic volume enlarged significantly at 6th hour and at one week after microembolization (P < 0.05 and P < 0.01 respectively). Serum TNF-alpha increased significantly at 6th hour (22.62 +/- 6.96) pg/ml compared with baseline (16.83 +/- 3.45) pg/ml (P < 0.05) and it further increased to (27.44 +/- 3.97) pg/ml at one week after coronary microembolization and was significantly higher than that at baseline (P < 0.01). CONCLUSIONS On delayed contrast enhanced magnetic resonance imaging, hyperenhancement of the anterior-septal and anterior wall of the left ventricle show at 6th hour but not at one week after coronary microembolization. This might represent the characteristic imaging after coronary microembolization. The left ventricular ejection fraction decreased at 6th hour and recovered one week later after coronary microembolization. Although impairment of left ventricular function could be recovered at 1 week after coronary microembolization, the left ventricular remodeling process still continued in concert with continuously elevation of serum TNF-alpha.