Assessment of myocardial viability in a reperfused porcine model: evaluation of different MSCT contrast protocols in acute and subacute infarct stages in comparison with MRI.

OBJECTIVE

To assess myocardial viability in acute and subacute infarcts using different multislice spiral computed tomography contrast protocols with magnetic resonance imaging (MRI) correlation.

METHODS

Seven pigs were studied with 64-multislice spiral computed tomography and MRI (1.5 T) at a median of 1 and 21 days after temporary occlusion of the second diagonal branch. Computed tomography was performed at 3, 5, 10, and 15 minutes after injection of contrast medium. Contrast agent was applied either as a bolus (protocol 1; n = 7 for the first; n = 5 for the second scan) or as a bolus plus 30 mL of subsequent 0.1 mL/s low-flow (protocol 2; n = 7 for the first; n = 6 for the second scan). Finally, histological sections were obtained. Volumes of infarcted myocardium were assessed as the percentage of the left ventricle. Computed tomography attenuation values were obtained, and image quality was assessed.

RESULTS

When compared with protocol 1, protocol 2 provided greater Hounsfield unit attenuation difference between viable and nonviable myocardium at 5, 10, and 15 minutes (P = 0.19; 0.003; 0.0006) and an additional significant contrast between nonviable myocardium and ventricular blood at 3 and 5 minutes (P < 0.001). Image quality was rated significantly higher with the use of protocol 2 at 5, 10, and 15 minutes (P < or = 0.027) and for all time points use of protocol 2 resulted in improved correlation of acute and subacute infarct size with MRI.

CONCLUSIONS

Good correlation of infarct zones with MRI was achieved for both acute and subacute infarcts. With the use of a bolus/low-flow protocol, image quality was substantially improved by means of a higher tissue contrast.