Acute infarct selective MRI contrast agent.

Abstract

To determine the infarct affinity of a low molecular weight contrast agent, Gd(ABE-DTTA), during the subacute phase of myocardial infarct (MI). Dogs (n = 7) were examined, using a closed-chest, reperfused MI model. MI was generated by occluding for 180 min the left anterior descending (LAD) coronary artery with an angioplasty balloon. DE-MRI images with Gd(ABE-DTTA) were obtained on days 4, 14, and 28 after MI. Control DE-MRI by Gd(DTPA) was carried out on day 27. T2-TSE images were acquired on day 3, 13 and 27. Triphenyltetrazolium chloride (TTC) histomorphometry validated postmortem the existence of infarct. Gd(ABE-DTTA) highlighted the infarct on day 4, but not at all on day 14 or on day 28, following MI. On day 4, the mean &#xb1; SD signal intensity (SI) of infarcted myocardium in the presence of Gd(ABE-DTTA) significantly differed from that of healthy myocardium (45 &#xb1; 6.0 vs. 10 &#xb1; 5.0, P < 0.05), but it did not on day 14 (11 &#xb1; 9.4 vs. 10 &#xb1; 5.7, P = NS), nor on day 28 (7 &#xb1; 1.5 vs. 7 &#xb1; 2.4, P = NS). The mean &#xb1; SD signal intensity enhancement (SIE) induced by Gd(ABE-DTTA) was 386 &#xb1; 165% on day 4, significantly different from mean SIE on day 14 (9 &#xb1; 20%), and from mean SIE on day 28 (12 &#xb1; 18%), following MI (P < 0.05). The last two mean values did not differ significantly (P = NS) from each other. As control, Gd(DTPA) was used and it did highlight the infarct on day 27, inducing a mean SIE value of 312 &#xb1; 40%. The mean SIE on day 3, 13, or 27 did not vary significantly (P = NS) on the T2-TSE images (114 &#xb1; 41%, 123 &#xb1; 41%, and 150 &#xb1; 79%, respectively). Post mortem, the existence of infarcts was confirmed by TTC staining. The infarct affinity of Gd(ABE-DTTA) vanishes in the subacute phase of scar healing, allowing its use for infarct age differentiation early on, immediately following the acute phase.