The Veterinary Teaching Hospital at the University of Illinois recently installed a new 3T MRI (Skyra, GE) for clinical and research cases. This imaging modality has software and hardware capabilities that allow for high-resolution, multi-planar, dynamic imaging of the heart.
In human medicine, cardiac MRI (CMR) is the reference standard for assessing ventricular systolic function and cardiac anatomy. CMR is the only imaging modality that can identify myocardial fibrosis and inflammation, and it is widely used in the assessment of congenital heart disease, cardiomyopathies, and myocardial infarctions. The advantages of CMR over echocardiography and CT are accuracy, reproducibility, unrestricted field of view, non-ionizing radiation, and the ability to characterized myocardial tissue. It allows cardiologists to view the heart in all planes and can be used to reconstruct a heart in 3D.
CMR is the reference standard for evaluating heart size and function. With the new, large-bore MRI, Drs. Kara Lascola, Ryan Fries, and Stuart Clark-Price created a CMR protocol for assessing cardiac function in healthy neonatal foals. Cardiovascular evaluation and monitoring are frequently required in hospitalized neonatal foals presenting with thoracic trauma, suspected congenital cardiac defects, or dysrhythmias and are especially important in critically ill neonatal foals, in which hemodynamic derangements associated with sepsis or SIRS are very common.
There is a need for the identification of reliable, noninvasive, and clinically useful mechanisms for cardiovascular monitoring in neonatal foals as this will improve detection of abnormalities and thus allow for earlier institution of goal-directed therapy. Using CMR as the reference standard, the team evaluated multiple non-invasive modalities for assessing cardiac function. The availability of CMR as a reference standard has significantly improved our ability to objectively evaluate the accuracy of other modalities and increased confidence in our recommendations to practicing veterinarians.
In addition to visualizing the chambers of the heart, CMR can determine the composition of heart muscle based on the proton density of substances. This is an exciting area of research in people, as the makeup of the heart muscle can predict which people are more like to develop fatal arrhythmias or heart failure with certain types of heart disease. CMR can detect diffuse fibrosis by quantitative myocardial mapping. Cardiac mapping measures the relaxation time, determined by how rapidly protons re-equilibrate their spins after an excitation radiofrequency pulse.
All tissues have inherent relaxation times that are based on a composite of their cellular and interstitial components (e.g., water, protein, fat, and iron content). In human medicine, CMR mapping is a vitally important prognostic tool. Dr. Ryan Fries has begun evaluating the composition of heart muscle in normal cats and cat with hypertrophic cardiomyopathy (HCM). This research sets out to establish a better protocol for predicting outcomes including congestive heart failure, arterial thromboembolism, and sudden death in cats with HCM. Currently, there is no reliable way to predict these outcomes in cats.
If you have questions about CMR or any heart-related issues, please do not hesitate to contact our service for more information at (217) 300-1643 or VTHCardiology@vetmed.illinois.edu.
—Dr. Ryan Fries, DVM, DACVIM (Cardiology)
Feature photo: The University of Illinois is at the forefront of advancing CMR technology, an established imaging modality in human patients with heart disease, in veterinary medicine. The cardiology service at the University of Illinois is pictured above. Back row: resident Dr. Jon Stack and board-certified cardiologist Dr. Ryan Fries. Front row: board-certified cardiologist Dr. Jordan Vitt, technician Candice Simpson, resident Dr. Saki Kadotani, and technician Katie McConnell.