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Cardiomyopathy Assessment by T1/T2 Mapping in Clinical Practice (APOLLON)



Moderators: Andrew E. Arai, MD (National Institutes of Health) and James Moon, MD (The Heart Hospital)

This session immediately followed the opening plenary and was very well attended. 5 experts in the field gave an update on the current state of the art in parametric T1 mapping in clinical practice.

Mariana Fontana from The Heart Hospital kicked off the session with a talk on the role of T1 Mapping left ventricular hypertrophy.
We heard how cardiovascular magnetic resonance tissue characterisation techniques are advancing and transforming our understanding of hypertrophy. The late gadolinium technique cannot detect diffuse diseases.
T1 mapping is an emerging technique where the T1 can be visualised on an image with a pixel-wise colour map, the scale of which represents the T1 in msec. Large changes occur in rare diseases (amyloidosis, Anderson-Fabry’s) even at an early stage, while more subtle changes are seen in diffuse fibrosis where the utility T1 is more questionable (figure 1).
T1 has the potential to have a role as surrogate end-point in clinical trials.

Figure 1

From T1 to T2, Subha Raman from The Ohio State University continued with a very balanced talk about the merits of T2 weighted imaging (T2WI) vs T2 mapping.
T2 imaging has applications in clinical assessment of myocardial edema and inflammation. T2WI has been in use for over two decades, with considerable literature supporting its utility in a broad range of cardiac conditions but it has significant problems with artefact and quantification.
Quantitative T2 mapping has emerged more recently with a smaller but growing level of supporting evidence. T2 maps, similar to T1 maps produce a pixel-wise colour map, with the scale representing the T2 in msec. It has the potential and some data to suggest that it is more sensitive and specific and less prone to artifact than T2WI.
Implementation and interpretation of quantitative T2 maps requires attention to quality control and understanding potential artifact.

Next up was Erica Dall’Armellina from Oxford University whos mandate was to tell us the additive value of mapping in ischemic cardiomyopathy.
Mapping techniques allow for absolute quantification of the myocardial tissue composition. While standard techniques such as late gadolinium enhancement or T2 weighted are being widely used, they are hampered by significant challenges due to the fact that the signal intensity is displayed on arbitrary scale and the postprocessing requires reference ROIs placed in the remote myocardium.
Native T1 and T2 mapping techniques may bring additional value in diagnosing diffuse oedema or minor ischemic insult and in guiding therapy by understanding better the underlying pathophysiology. 
Furthermore, first results of post contrast T1 mapping techniques to assess extracellular volume indicate the potential to provide new insights in remodelling processes post myocardial infarction, and to improve the prediction of long term outcome.

Andrew Arai from the National Institute of Health talk us through the role of novel techniques in genetic disease. We heard how T2* imaging has reduced the burden of heart disease and death in thalasemia population – one of the few examples of the holy grail of where a test has influenced outcome. He showed a variety of early data of how quantitative CMR may influence diagnostic decisions – from the fractal dimension in left ventricular non compaction, to the potential to calculate the fat fraction in arrythmogenic right ventricular cardiomyopathy.
We finished with Matthias Friedrich from the Montreal Heart Institute and his talk entitled: What Constitutes a Good Biomarker and Can Native T1 or ECV Fit the Bill?
Biomarkers include all a naturally occurring molecules, genes, or characteristics by which a particular pathological or physiological process, disease can be identified. Imaging-derived markers can be used as biomarkers. A “good” biomarker should however also be safe, accurate, reproducible, accessible and cost-efficient.
Importantly, its use should have a positive impact on outcome. This is an important but challenging criteria. Large-scale studies are required to prove this. Native T1 and ECV have shown great potential as markers for regional and diffuse myocardial changes such as edema and fibrosis. Yet, several of the criteria required for good biomarkers are not met yet and therefore, more research is required for making native T1 and ECV fit this bill.

References


Cardiomyopathy Assessment by T1/T2 Mapping in Clinical Practice (APOLLON)
The content of this article reflects the personal opinion of the author/s and is not necessarily the official position of the European Society of Cardiology.