Myocardial hypertrophy and extracellular volume by cardiovascular magnetic resonance imaging

Abstract

Cardiovascular disease contributes greatly to the disease burden in many developed countries. Cardiovascular magnetic resonance (CMR) is a powerful imaging modality that can diagnose a vast range of these diseases. When combined with an extracellular contrast agent, CMR can not only diagnose the function and size of the heart but also provide detailed information on the myocardial tissue. CMR T1 and extracellular volume (ECV) mapping can be used to quantitatively characterise the tissue properties of the myocardium. The main objective of this work was to determine how to use these and other imaging capabilities of CMR imaging in order to maximise the diagnostic abilities and predict adverse outcomes.

Study I examined whether T1 and ECV mapping could be useful for detecting myocarditis when acquired early after contrast administration. Study II looked at the prevalence of diffusely increased ECV in a clinical population. Study III presents a novel way of calculating global wall thickness (GT), i e the average thickness of the whole left ventricle. GT can easily be calculated from the left ventricular mass and volume which are measured as a part of a normal CMR examination. Study IV examined the feasibility of determining the myocardial cell size using early T1 mapping and calculating the intra-cellular lifetime of water (tau).

Study I found no benefit of performing early compared to late post-contrast imaging when detecting myocarditis. Study II found that found that 8 % of a clinical population had diffusely increased ECV, that increased ECV was more common in patients with a dilated left ventricle and that focal lesions were more common in patients with decreased systolic function. Study III derived and validated a new measure for global wall thickness (GT) that can be easily calculated from the left ventricular mass (LVM) and volume. GT was highly prognostic in patients with otherwise normal findings and can be used together with LVM to classify different types of hypertrophy. Study IV found that measuring the size of cardiomyocytes using contrast-enhanced CMR in a clinical setting was not reliable using the slow exchange model of transcytolemmal water exchange.