Multimodality Assessment of Ventricular Scar Arrhythmogenicity.

We aim to improve our understanding of a life-threatening heart rhythm disorder known as ventricular tachycardia (VT). This is a disorder which originates from the lower chamber of the heart and frequently is associated with heart disease. We will use an MRI scan to generate a computer based model of the heart which can predict areas of the heart which are important in generating this rhythm disorder. We intend to assess how accurate this computer model is compared to traditional invasive assessment of the heart muscle. We also aim to assess the electrical characteristics of those areas which were predicted by the computer model in order to see why they were thought to be so important. All patients seen at St George's Hospital with VT will be eligible. As is routine for these patients, they will have an MRI scan of the heart. We will then use this scan to create a virtual reconstruction of the heart from which predictions of the critical areas of the heart which are generating the rhythm problem will be made. Then we will perform a VT ablation (studying the electrical properties and if necessary making a burn to treat the rhythm problem) - as per standard of care, however during the ablation we will spend extra time collecting information comparing the accuracy of the computer-generated model to the traditional invasive signals which guide ablation. We will study the electrical properties of those predicted areas to see what is special about them. The study will last up to three years.

Patients will be eligible for this trial both from referrals as an outpatient, where VT has been detected on a heart rhythm monitor or ECG (electrical heart tracing), or as an inpatient where they have been admitted to hospital with symptoms of VT. Our study investigators will discuss the research with the patient and give them the relevant information in an understandable format as part of a Patient Information Sheet so that they can make an informed decision about whether or not to participate in the research. An MRI scan of the heart is a standard investigation for patients presenting with VT, however if the patient is included in the study, the MRI scan images will be anonymised and sent confidentially to the Institute of Computational Modelling at Johns Hopkins University in USA where the images will be reconstructed into a 3D representation of the patients heart, where the electrical pathways and source of the VT can be seen. This information will be sent back (again confidentially and anonymously) to St George's Hospital in time for their routine VT ablation procedure. During the VT ablation The MRI scan model will be combined with the invasively-obtained information and we will assess the various areas of the heart which are responsible for the VT, particularly relating to areas of scar within the heart, which are frequently seen in these patients. We will assess the electrical properties of the areas highlighted as the cause of the VT from the MRI scan. We will assess the accuracy of the computer model compared to the traditional invasive measurements that we take. We will first ablate those areas of the heart which the model predicted as being important (as long as the invasive characteristics support ablation there) and then see what effect this had on the electrical properties of other areas of the heart. However, we will not ablate any area of the heart based solely on the MRI model; it will only influence the order of ablation and not tell us whether to ablate or not. The procedure can take 4-6 hours in total. The extra information gathered as part of the research protocol may extend this by a maximum of 10%. No extra pieces of equipment, procedures or medications are involved in the research, just the time taken to generate a computer model of the heart as well as a extra time to assess the heart in more detail during the ablation. Following the ablation, the patients will be followed at 3, 6 and 12 months with a heart rhythm monitor and a clinical review as an outpatient as per routine standard of care. From this, we will collect data on frequency of recurrence of rhythm disturbance, therapy from their implantable cardioverter-defibrillators, symptoms and complications following the ablation procedure. The information gathered during the procedure will be analysed and research papers generated from the results.