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Published on: August 17, 2022
Gadomer-enhanced MR imaging in the detection of microvascular obstruction: alleviation with nicorandil therapy
Gabriele A Krombach1, Charles B Higgins, Mitsuaki Chujo
1Department of Radiology, University of California, San Francisco, 505 Parnassus Ave, HSW 207B, San Francisco, CA 94143-0628, USA.
Purpose:
To evaluate Gadomer-enhanced magnetic resonance (MR) imaging in the quantification of small microvascular obstruction regions and determine if nicroandil alleviates the formation of microvascular obstruction.
Materials And Methods:
Approval of the institutional committee on animal research was obtained, and this study complied with guidelines for care and use of animals. Rats underwent coronary artery occlusion and reperfusion. After 24 hours, Gadomer-enhanced T1-weighted spin-echo MR imaging was used to define microvascular obstruction in animals in control and nicorandil groups. Sequential MR images obtained at two midventricular levels were acquired to measure microvascular obstruction and ischemically injured regions and monitor diffusive and/or convective transport of Gadomer in microvascular obstruction regions. Two investigators working in consensus and using threshold signal intensity measured differentially enhanced regions. Left-ventricular (LV) end-systolic and end-diastolic MR images obtained at the same two midventricular levels were used to measure regional wall thickening and systolic reduction in LV relative volumes. Agreement and correlation between MR imaging and postmortem data were determined with Bland-Altman and linear regression analyses. Animals were sacrificed 3 minutes after intravenous injection of blue dye.
Results:
On Gadomer-enhanced MR images, two differentially enhanced regions were observed in ischemically injured myocardium, namely, the hypoenhanced region and the surrounding hyperenhanced region. Hypoenhanced regions at MR imaging and unstained regions at blue dye administration were identical 3 minutes after administration (17% +/- 1 and 17% +/- 2; P = .6; r = 0.98). In the control group, Gadomer provided a prolonged imaging window (eg, 6 minutes) for accurately quantifying small microvascular obstruction regions. Microvascular obstruction was observed in all animals in the control group and 27% of animals in the nicorandil group. Microvascular obstruction regions were smaller in the nicorandil group (eg, 3% +/- 1) than in the control group (eg, 17% +/- 2) (P < .001). Hyper- and hypoenhanced regions were also smaller (eg, 20% +/- 2) in rats in the nicorandil group than in those in the control group (37% +/- 4, P < .001). Improvement in LV function in the nicorandil group is likely related to alleviation and reduction in infarct size.
Conclusion:
Gadomer-enhanced MR imaging can be used to quantify small microvascular obstruction regions 24 hours after reperfusion. Intravenous therapy with nicorandil reduces formation of microvascular obstruction regions.
Insights
Gadomer-enhanced MRI accurately quantifies microvascular obstruction post-reperfusion. Nicorandil treatment significantly reduces microvascular obstruction formation and infarct size in rats, improving left-ventricular function.
Area of Science:
- Cardiovascular Imaging
- Myocardial Infarction Research
- Pharmacological Interventions
Background:
- Microvascular obstruction (MVO) is a key determinant of infarct size and adverse remodeling after myocardial infarction.
- Accurate quantification of MVO is crucial for evaluating therapeutic strategies.
- Gadomer, a contrast agent, has shown potential for enhancing MR imaging of cardiovascular structures.
Purpose of the Study:
- To assess the efficacy of Gadomer-enhanced magnetic resonance (MR) imaging in quantifying small microvascular obstruction regions.
- To determine if nicorandil alleviates the formation of microvascular obstruction following myocardial ischemia-reperfusion injury.
Main Methods:
- Rats underwent coronary artery occlusion and reperfusion.
- Gadomer-enhanced T1-weighted spin-echo MR imaging was employed 24 hours post-reperfusion to define MVO in control and nicorandil-treated groups.
- MR imaging quantified MVO and ischemically injured regions, monitoring Gadomer transport.
- Left-ventricular (LV) function was assessed via regional wall thickening and relative volume changes.
Main Results:
- Gadomer-enhanced MR imaging identified distinct hypoenhanced and hyperenhanced regions in the ischemic myocardium, correlating with blue dye unstained areas.
- Microvascular obstruction was present in all control animals but only 27% of nicorandil-treated animals.
- Nicorandil treatment significantly reduced the size of MVO regions (3% +/- 1 vs. 17% +/- 2, P < .001) and overall enhanced regions (20% +/- 2 vs. 37% +/- 4, P < .001).
Conclusions:
- Gadomer-enhanced MR imaging is a reliable method for quantifying small microvascular obstruction regions 24 hours after reperfusion.
- Intravenous nicorandil therapy effectively reduces the formation of microvascular obstruction regions.
- The observed reduction in MVO and infarct size in the nicorandil group is associated with improved LV function.
