Assessment of subclinical cardiac changes in structure and function by cardiovascular magnetic resonance

Background:
The early identification of disease can benefit patients clinically and provide a powerful research tool. This thesis aims to identify subclinical cardiac change using cardiovascular magnetic resonance (CMR) in both disease and health and evaluate its diagnostic and prognostic uses.

Methods:
We have prospectively recruited and conducted multi-parametric CMR in 50 patients with hypertrophic cardiomyopathy (HCM), 40 endurance athletes and 100 asymptomatic patients with type 2 diabetes mellitus.

Results:
Study 1 and 2 evaluated CMR in the early diagnosis of HCM. Study 1 demonstrated the diagnostic accuracy of extracellular volume (ECV) mapping is superior to volumetric methods of differentiating HCM from athletic left ventricular (LV) hypertrophy. Study 2 demonstrated that ECV expansion could be detected prior to overt hypertrophy or impairment of contractile function in patients with HCM. Study 3 demonstrated that LV torsion is lower in endurance athletes than controls and is predominantly influenced by lactate threshold and intensity of training. Study 4 and 5 investigated the role of CMR in identifying patients with type 2 diabetes at risk of heart failure and silent myocardial infarction. Study 4 found that the increased risk of heart failure in patients with type 2 diabetes was mediated by ECV expansion and diffuse fibrosis. There was a high rate of silent myocardial infarction (17 %) which was unrelated to heart failure risk. In study 5 we developed a simple screening tool, using measures that can be carried out in a cardiology clinic, for the detection of silent myocardial infarction in type 2 diabetes.

Conclusions:
CMR is able to detect subclinical change in both tissue characteristics and function of the heart. This can aid the early and appropriate diagnosis of disease and identify those at the highest risk of adverse outcomes.