Scar shape analysis and simulated electrical instabilities in a non-ischemic dilated cardiomyopathy patient cohort

This paper presents a morphological analysis of fibrotic scarring in non-ischemic dilated cardiomyopathy, and its relationship to electrical instabilities which underlie reentrant arrhythmias. Two dimensional electrophysiological simulation models were constructed from a set of 699 late gadolinium enhanced cardiac magnetic resonance images originating from 157 patients. Areas of late gadolinium enhancement (LGE) in each image were assigned one of 10 possible microstructures, which modelled the details of fibrotic scarring an order of magnitude below the MRI scan resolution. A simulated programmed electrical stimulation protocol tested each model for the possibility of generating either a transmural block or a transmural reentry. The outcomes of the simulations were compared against morphological LGE features extracted from the images. Models which blocked or reentered, grouped by microstructure, were significantly different from one another in myocardial-LGE interface length, number of components and entropy, but not in relative area and transmurality. With an unknown microstructure, transmurality alone was the best predictor of block, whereas a combination of interface length, transmurality and number of components was the best predictor of reentry in linear discriminant analysis.Author summary: Non-ischemic dilated cardiomyopathy is a disease in which the lower left chamber of the heart is abnormally large. The cause of the disease can be anything that is not a loss of blood supply to the heart. Many patients with non-ischemic dilated cardiomyopathy have scars in their hearts which can be detected with magnetic resonance imaging. These scars are thought to disrupt the flow of electricity through the heart and cause deadly rhythm disorders. In our study we look at various ways to quantify the shapes and textures of the scars with MRI images, and relate these metrics to rhythm disturbances that we simulate in image-based biophysical models of electrical activity. The exact electrical properties of scars in non-ischemic dilated cardiomyopathy are unknown, so our simulations account for a variety of possible properties. Our findings suggest new ways of examining scar shapes which work well with all of the properties we tested. This makes our shape metrics potentially valuable for determining which non-ischemic dilated cardiomyopathy patients are at risk of future heart rhythm disorders.