Abstract
Myositis is the name of a group of rare conditions characterised by inflammation and fibrosis of skeletal muscle leading to pain and progressive weakness [1]. In a proportion of patients, extra skeletal muscle manifestations complicate the clinical course. In particular, cardiac muscle involvement is associated with worse outcomes [2, 3]. The pathophysiology of myocardial involvement is inflammation and fibrosis [4] which has proven difficult to identify by traditional investigations. The new techniques of T1 and T2 mapping in cardiovascular magnetic resonance (CMR) allow for assessment of myocardial fibrosis and oedema. Use of T1 and T2 mapping has been shown to offer improved sensitivity for mild and diffuse inflammation as well as subtle focal and diffuse fibrosis in inflammatory myocardial diseases such as viral myocarditis and sarcoidosis. This could help guide therapy and monitor treatment response [5, 6] in myositis.We scanned healthy volunteers to establish normal T1 and T2 values for our particular scanner. Using both healthy volunteers and patients with myositis we devised and validated a novel method of analysing the ventricle following a multi-segment model. The model was based on the 12 basal and mid-level American Heart Association myocardial segments [7]. The apical segments were excluded due to well documented issues around reproducibility [8, 9].
Using the above method, we found that patients with myositis had significantly higher T1 and T2 than healthy volunteers, independent of blood troponin. We also found that in patients with myositis, a raised troponin was associated with higher myocardial T1 and T2 values than those patients whose troponin was not elevated.
We performed follow -up scans on patients with myositis and demonstrated a reduction in T1 and T2 values over time without any change in overall cardiac function. T2 values returned to baseline over the course of the study whereas T1 values remained significantly higher than that of healthy volunteers.
These studies show that measuring myocardial T1 and T2 values in myositis may have a role in both the identification of inflammation or fibrosis and in monitoring the response to treatment. The sample size of the study did not allow for comparison of different treatments to be made.
We also undertook mapping of skeletal muscle tissue mapping using the same, gated, cardiac specific un-optimised sequences. The purpose was to look for trends in T1 and T2 values that might suggest a benefit in developing specific sequences to allow researchers or clinicians to reproducibly measure skeletal muscle disease activity non-invasively. We found that, despite large variability in the data set, T2 values decrease over time with treatment suggesting there may indeed be a benefit in working towards dedicated skeletal muscle sequences in the future.
| Date of Award | 1 Sept 2023 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Theresa Anne McDonagh (Supervisor) |