Ultrasmall superparamagnetic particles of iron oxide (USPIO)-enhanced magnetic resonance imaging (MRI) detected myocardial macrophage activity within the first 2 weeks after an acute myocardial infarction (MI), according to data published in Heart.
The DECIFER (Detection of Cellular Inflammation With Ferumoxytol in the Heart ClinicalTrials.gov identifier: NCT02319278) was an open-label observational cohort study. Patients (n=31; mean age 58.4years) were recruited within 7 days of an acute MI and followed for 3 months with repeated T2 and USPIO-enhanced T2-mapping MRI. Investigators focused on infarct, peri-infarct, and remote myocardial zones and compared these with control tissues.
Nearly half of the study patients had hypertension as well as a family history of premature coronary heart disease. A total of 25 patients had ST-segment elevation MI and 5 patients had non-ST segment elevation MI; 25 underwent percutaneous coronary intervention and 4 underwent coronary artery bypass grafting surgery.
As investigators pointed out, T2-weighted MRI is currently used to assess myocardial edema after MI, but it can only detect “myocardial free water content and not active cellular inflammation.” Therefore, they conducted this study to determine whether cellular inflammation could be tracked over the course of 3 months following acute MI using USPIO-enhanced MRI.
During the course of the study, 147 MRI scans and 54 infusions of ferumoxytol were completed.
USPIO enhancement was detected in the myocardium for up to 24 hours following a single dose (P <.001); uptake in the infarct zone peaked at 2 to 3 days and greater USPIO uptake was detected in the infarct zone vs remote myocardium until days 10 through 16 (P <.05). Meanwhile, myocardial edema as defined by T2-mapping peaked at 3 to 9 days and remained higher in the infarct zone through the follow-up period (P <.01).
This time course of USPIO uptake illustrates a pattern of macrophage inflammation that is specific to tissue edema caused by loss of capillary integrity, researchers noted. “This suggests that while capillary integrity may take several months to resolve, cellular inflammation and specifically macrophage activity predominates in the first 2 weeks following MI.”
“This imaging technique holds promise as a noninvasive method of assessing and monitoring myocardial cellular inflammation with potential application to diagnosis, risk stratification, and assessment of novel anti-inflammatory therapeutic interventions,” the researchers concluded.
Stirrat CG, Alam SR, MacGillivray J, et al. Ferumoxytol-enhanced magnetic resonance imaging assessing inflammation after myocardial infarction [published online June 22, 2017]. Heart. doi:10.1136/heartjnl-2016-311018