Necrosis-avid Contrast Agent Assessment Of Myocardial Viability In Experimental Study

Objective To compare intracoronary administration of ECIII-60, a necrosis-avid contrast agent (NACA) with standard extracellular agent Gd-DTPA(Magnevist) for determination of myocardial viability (MV) in a swine model of reperfused acute myocardial infarction (AMI) with MRI.Methods Twelve pigs underwent 90 minutes of occlusion and 120 minutes of reperfusion of the left circumflex coronary artery. To establish a pig model of reperfused acute myocardial infarction. In 6 dogs each, Gd-DTPA at 0.1 mmol/kg or Gadophrin-2 at 0.005 mmol/kg was administered into coronary artery. Serial ECG-triggered cardiac MRI of T1-weighted IR-FAST sequence was conducted. After the dogs were killed, the heart was excised and embedded in agar, and postmortem MRI was performed. The agar block was then cut perpendicular to the long axis into 6-mm-thick short axial slices starting from the apex. The contrast ratio on the delayed contrast enhanced MRI of the infarct area was compared with that of the normal area. The extent of delayed enhanced area on contrast enhanced MRI was compared with the extent of the infarct area on TTC stained sections.Results1. After administration,ECIII-60 induced a strong (CR≥2.1) and persistent(≥6h) contrast enhancement of infracted region. the infarct size defined with ECIII-60 was the same as the size of infarct myocardium with TTC staining.2. Immediately after injection of Gd-DTPA, a strong infarct-to-normal contrast was created(CR=2.232±0.008),however, contrast enhancement steadily diminished with time, CR=2.151±0.019 in 30 min, CR=1.698±0.027 in 60 min, CR=1.147±0.69 in 120min. The enhanced region overestimated infarct size (21%) at the 10 min after the injection of Gd-DTPA, the enhanced region gradually receded to match the size of the infarct about 30 min, and rapidly diminished in size.Conclusions1. MR images with ECIII-60 provide accurate sizing of infarct myocardium with a strong and persistent signal enhancement in the reperfused infarction myocardium.2.Gd-DTPA imaging display a transient unstable enhancement,cardiac MRI should be performed within 1h after contrast.3. Contrast-enhanced MRI in conjunction with intracoronary administration may prove feasible for post-procedural myocardial viability assessment.