Collateral circulation formation determines the characteristic profiles of contrast-enhanced MRI in the infarcted myocardium of pigs

Simulation of the Perfusion of Contrast Agent Used in Cardiac Magnetic Resonance: A Step Toward Non-invasive Cardiac Perfusion Quantification

This work presents a new mathematical model to describe cardiac perfusion in the myocardium as acquired by cardiac magnetic resonance (CMR) perfusion exams. The combination of first pass (or contrast-enhanced CMR) and late enhancement CMR is a widely used non-invasive exam that can identify abnormal perfused regions of the heart via the use of a contrast agent (CA). The exam provides important information to the diagnosis, management, and prognosis of ischemia and infarct: perfusion on different regions, the status of microvascular structures, the presence of fibrosis, and the relative volume of extracellular space. This information is obtained by inferring the spatiotemporal dynamics of the contrast in the myocardial tissue from the acquired images. The evaluation of these physiological parameters plays an important role in the assessment of myocardial viability. However, the nature of cardiac physiology poses great challenges in the estimation of these parameters. Briefly, these are currently estimated qualitatively via visual inspection of images and comparison of relative brightness between different regions of the heart. Therefore, there is a great urge for techniques that can help to quantify cardiac perfusion. In this work, we propose a new mathematical model based on multidomain flow in porous media. The model is based on a system of partial differential equations. Darcy's law is used to obtain the pressure and velocity distribution. CA dynamics is described by reaction-diffusion-advection equations in the intravascular space and in the interstitial space. The interaction of fibrosis and the CA is also considered. The new model treats the domains as anisotropic media and imposes a closed loop of intravascular flow, which is necessary to reproduce the recirculation of the CA. The model parameters were adjusted to reproduce clinical data. In addition, the model was used to simulate different scenarios: normal perfusion; endocardial ischemia due to stenosis in a coronary artery in the epicardium; and myocardial infarct. Therefore, the computational model was able to correlate anatomical features, stenosis and the presence of fibrosis, with functional ones, cardiac perfusion. Altogether, the results suggest that the model can support the process of non-invasive cardiac perfusion quantification.

Correlation between GDF 15 gene polymorphism and the collateral circulation in acute non-ST segment elevated myocardial infarction

OBJECTIVE

To investigate the correlation between growth differentiation factor 15 (GDF 15) + 157 A/T polymorphism and the formation of collateral circulation in acute non-ST segment elevated myocardial infarction in Han population of Shandong province.

METHOD

The medical records of 200 cases of patients undergoing selective coronary angiography were analyzed, and the arterial blood specimens of included patients were collected before coronary angiography. Based on the results of coronary angiography, patients were divided into acute myocardial infarction (AMI) group and normal control group; AMI group was divided into collateral group and non-collateral group by Rentrop's grading method; polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and DNA sequencing methods were used to analyze the GDF 15 + 157 A/T polymorphism in the two groups.

RESULTS

There were statistically significant differences in GDF 15 + 157 A/T AA and AT distribution between AMI group and the control group (P = 0.002); and there was statistically significant difference in allele frequencies between the two groups (P = 0.006); for AMI group, there were statistically significant differences in GDFAA and AT genotype distribution between patients with and without collateral (P = 0.014), and there was statistically significant difference in allele frequencies between the two (P = 0.025).

CONCLUSION

There was correlation between GDF 15 + 157 A/T polymorphism and the formation of collateral circulation in patients with non-ST-segment elevated myocardial infarction.