Investigating Myocardial Infarct Scars as a Focal Arrhythmogenic Substrate Using Advanced Computational Modelling Based-On High-Resolution Imaging

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Although an increasing number of people survive heart attacks, the scar left in their heart muscle leaves them at an increased risk of developing lethal cardiac 'arrhythmias' (abnormal beating of the heart) following the initial attack. Little is known about the underlying processes linking the presence of scars to increased death from cardiac arrhythmias. Specifically, it is not well understood whether the scar is involved in the actual generation of the arrhythmia, or whether it just helps to stabilise an arrhythmic episode generated by another mechanism, unrelated to the scar itself. As a result, diagnosis and therapy planning is non-optimal for these patients, and the rate of sudden death due to arrhythmic events is still high within this population.Current clinical tools can provide useful information regarding scars within patients who have suffered prior heart attacks. Clinical magnetic resonance (MR) imaging gives an important non-invasive means of analysing the location and shape of scars in patients. In addition, analysis of clinical electrocardiogram (ECG) recordings during arrhythmia can suggest not only the type of arrhythmia, but also the role the scar may play in such episodes. In particular, careful analysis of the shape of the ECG trace in the first few arrhythmic beats has suggested that, in many cases, the scar itself is highly likely to be the actual source of the ectopic activity responsible for generating the arrhythmia.Basic science investigations have shown that the structure of the tissue in and around the scar is highly diverse, and that the functional electrical properties are also changed from that of the normal, healthy cardiac tissue. As such, how the scar may act to generate lethal arrhythmia is thought to involve highly complex processes, which are not yet well understood.Our goal is to use computer modelling alongside high-resolution animal and clinical images to gain an in-depth understanding of the underlying processes involved in the generation of lethal arrhythmias directly from within cardiac scars.By using high-resolution animal images of scars, we will generate exceptionally-detailed computational models to investigate how the interaction between structural and functional diversity within a scar may encourage the generation of arrhythmia. This will allow us to understand how the fine-scaled properties of the scar and surrounding tissue make it susceptible to arrhythmias, identifying key 'hot spot' regions which represent the most dangerous potential sources of arrhythmic activity.We will then use this knowledge in comparison with patient MR and arrhythmia incidence data to make an important step towards translating these findings into the clinic, helping provide a mechanistic explanation of the underlying observed relationships uncovered in the clinical data.Overall, the findings from this research will pave the way for improved of risk stratification in patients with cardiac scars, and the development of novel clinically-useful therapies targeting the scar as a source of arrhythmia generation. The potential beneficiaries from this research will be extensive due to the high incidence of heart attacks annually in the UK (124,000), and the significant risk posed by arrhythmia to individuals following a heart attack. Consequently, this work also has the potential to reduce the health and economic costs of associated death and illness.