Magnetic Resonance Characterization of the Peri-Infarction Zone of Reperfused Myocardial Infarction With Necrosis-Specific and Extracellular Nonspecific Contrast Media

Abstract

Background-Because ischemically injured myocardium is frequently composed of viable and nonviable portions, a method to discriminate the two is useful for clinical management. Methods and Results-Ischemically injured myocardium was characterized with extracellular nonspecific (Gd-DTPA) and necrosis-specific (mesoporphyrin) MR contrast media in rats. Relaxation rates (R1) were measured on day 1 and day 2 by inversion-recovery echoplanar imaging. Spin-echo imaging was used to define contrast-enhanced regions and regional wall thickening. Gadolinium concentration, area at risk, and infarct size were measured at postmortem examination. ⌬R1 ratio (⌬R1 myocardium /⌬R1 blood ) after administration of Gd-DTPA was greater in ischemically injured myocardium (1.20Ϯ0.15) than in normal myocardium (0.47Ϯ0.05, PϽ0.05), which was attributed to differences in gadolinium concentration and water content. The Gd-DTPA-enhanced region on day 2 was larger (32.8Ϯ0.9%) than true infarction as demonstrated by triphenyltetrazolium chloride (TTC) (24.6Ϯ1.4%, PϽ0.001, rϭ0.21). Bland-Altman analysis revealed that the Gd-DTPA-enhanced region overestimated true infarct size by 7.8Ϯ5.9%. On the other hand, the mesoporphyrin-enhanced region (26.9Ϯ1.8%, PϭNS, rϭ0.87) and true infarct size were identical. The difference in the areas demarcated by the 2 agents is the peri-infarction. Systolic and diastolic MR images revealed no wall thickening in the mesoporphyrin-enhanced region (0.3Ϯ3.3%) but reduced thickening in the Gd-DTPA-enhanced rim (8.5Ϯ5.5%, PϽ0.05). Conclusions-The Gd-DTPA-enhanced region encompasses both viable and nonviable portions of the ischemically injured myocardium. The Gd-DTPA-enhanced area overestimated infarct size, but the mesoporphyrin-enhanced area matched true infarct size. The salvageable peri-infarction zone can be characterized with double-contrast-enhanced and functional MR imaging; the mismatched area of enhancement between the 2 agents shows residual wall thickening.

Accuracy of Contrast-Enhanced Magnetic Resonance Imaging in Predicting Improvement of Regional Myocardial Function in Patients After Acute Myocardial Infarction

“…4 As a result, it has been postulated that hyperenhanced myocardium detected clinically could also include significant amounts of damaged noninfarcted tissue and, thus, would reflect viable rather than nonviable myocardium. 6,13,14 In support of this, Dendale et al 15 reported inotropic response in 41% of hyperenhanced segments, suggesting viability. Rogers et al 6 also reported that regions presenting delayed hyperenhancement alone or in combination with early hypoenhancement improved circumferential shortening between 1 and 7 weeks after acute MI and would, therefore, be viable.…”

Low-intensity late gadolinium enhancement predominates in hypertrophic cardiomyopathy

“…Namely, low-intensity LGE, approximately 2-3 S.D. above remote myocardium, corresponds to a border zone around infarcts comprised of viable myocytes interspersed within fibrosis [24][25][26], where as more the intermediate/high-intensity LGE corresponds to completely necrotic or fibrotic tissue. Given the entirely different pathophysiology of HCM, the significance of different intensities of LGE cannot be inferred from the MI literature.…”

Correlation of Electrocardiogram and Regional Cardiac Magnetic Resonance Imaging Findings in ST‐Elevation Myocardial Infarction: A Literature Review

“…35 With the combination of the inversion recovery technique described by Simonetti et al, 36 it became possible to maximize the contrast between viable and 37,38 There is significant decrease in the total extent of LGE between day 1 and day 7 post-MI. [39][40][41] CMR can be used in assessing MI size up to 1 week after the acute ischemic event. With time, the size of the infarct decreases as a result of resolution of tissue edema and gradual contraction of the resultant scar tissue by as much as 25% over a period of 4-8 weeks.…”