Cardiac MRI in diagnosis and management

Cardiac magnetic resonance imaging (CMR) is an essential tool in the diagnosis, risk stratification and treatment of patients with hypertrophic cardiomyopathy (HCM). CMR works by manipulating protons found in myocytes and contrast agents such as Gadolinium, using magnetic pull to create and then detect energy differences and thus obtain images. CMR is ideal for detecting the location and extent of hypertrophy, presence or absence of membranes, the distribution of fibrosis and the anatomy and physiology of the mitral valve, all of which are crucial for diagnosis of HCM, which can be missed on standard echocardiography. This is especially true for hard to see areas of the heart such as the apical area as well as atypical presentations such as focal segmental hypertrophy or mass-like HCM. Additionally, extremely accurate assessments of the left ventricular volumes, mass and function are prognostic as well as diagnostic. Magnetic resonance tagging and delayed-enhancement with Gadolinium allow for strain and perfusion analysis, further increasing the utility of CMR to detect regional function and cardiac microvascular ischemia, of which HCM patients are particularly susceptible. Delayed enhancement distribution and extent may also impact risk stratification for sudden cardiac death. Limitations of CMR include assessment of the left ventricular outflow tract gradient and highly mobile structures on the mitral valve, although newer protocols and improved technology may be able to compensate for these deficits in the future.