Invited Commentary

Abstract

By using a combination of magnetic resonance imaging (MRI), catheterization, computational modeling, and numeric optimization, McGarvey and his colleagues responsible for this paper serially quantified the in vivo material properties and fiber orientation of infarcted myocardium over a 12-week period in a porcine model of myocardial infarction (MI) [1McGarvey J.R. Mojsejenko D. Dorsey S.M. et al.Temporal changes in infarct material properties: an in vivo assessment using magnetic resonance imaging and finite element simulations.Ann Thorac Surg. 2015; 100: 582-590Abstract Full Text Full Text PDF PubMed Scopus (24) Google Scholar]. This is an elegant work that utilizes a well-established animal model and a multidisciplinary approach. Specifically, properties were determined by minimizing the difference between in vivo strains and volume calculated through MRI and the finite element model predicted strains and volume. These novel findings in the in vivo model are consistent with previously described ex vivo biaxial studies of infarct material properties and the circumferential change of collagen orientation in the infarcts. It would be quite helpful to use the postmortem left ventricle (LV) specimens harvested at the end of the 12-week experiment to assess the altered microstructure of the LV tissues for tissue stiffness, collagen deposition, and myofiber orientation. Hopefully, the in vitro study on the tissue microstructure will correlate with or further confirm the in vivo findings of the current study. It will also be imperative to serially quantify the in vivo material properties of remote and border-zone myocardium during the remodeling period. The current study definitely represents a significant advance in that the multiple approaches employed allow for the serial assessment of an individual infarct in vivo overtime. These diagnostic techniques may be used in the future to accurately assess the potential therapeutic efficacy of LV restraint devices, biomaterials, stem cells, and other new medications on the infarct material properties during the remodeling period in vivo overtime. Obviously, these novel approaches may be applied to quantify the in vivo material properties and fiber orientation of infarcted myocardium in patients with LV remodeling. Clinically, patients often suffer from multiple coronary artery occlusions with a more complicated MI. It can be assumed that the LV remodeling developed in patients with MI will be more complicated than that of the animal models with either left anterior descending artery (anteroapical infarcts) or left circumflex artery occlusion (posterolateral infarcts). Taken together, the current study supports the notion that the inhibition of infarct expansion is an important therapeutic target in the prevention of adverse LV remodeling after MI. The application of a multidisciplinary approach, such as a combination of MRI and computational cardiac modeling for assessing LV remodeling, is still in its infancy in cardiac surgery. It continues to be a challenge for cardiac surgeons to use the multiple diagnostic tools to improve efficiency in assessing the development of LV remodeling after MI and therapeutic efficacy in vivo overtime. This challenge would best be met through improved multidisciplinary collaboration and cooperation from other specialists, including those specializing in computational modeling, MRI, ultrasound, bioengineering, pathology, cardiology, and basic research. Temporal Changes in Infarct Material Properties: An In Vivo Assessment Using Magnetic Resonance Imaging and Finite Element SimulationsThe Annals of Thoracic SurgeryVol. 100Issue 2PreviewInfarct expansion initiates and sustains adverse left ventricular (LV) remodeling after myocardial infarction (MI) and is influenced by temporal changes in infarct material properties. Data from ex vivo biaxial extension testing support this hypothesis; however, infarct material properties have never been measured in vivo. The goal of the current study was to serially quantify the in vivo material properties and fiber orientation of infarcted myocardium over a 12-week period in a porcine model of MI. Full-Text PDF