Magnetocardiography (MCG) Parameters in the Prediction of Future ICD Therapy

Overview

A multi-centre observational cohort trial to identify Magnetocardiography (MCG) parameters in the prediction of future ICD therapy. To show a correlation between Arrhythmogenic features on MCG and future ICD therapies seen on ICD interrogation of patients at risk of SCD.

AIM: To explore if VitalScan MCG parameters are able to predict future ICD therapies in patients who meet the requirements for ICD therapy. Magnetocardiography (MCG) Magnetocardiography (MCG) is a non-invasive, non-contact body-surface method which uses magnetometers to measure and map the magnetic fields generated by the electrical activity within the heart. It offers a better spatial resolution than an ECG recording and opens the possibility of detecting conduction characteristics consistent with arrhythmogenesis. The application of MCG has been limited by feasibility as devices up to now have been based on superconducting quantum interference devices (SQUID) with super cooled sensors. These machines were often operated in a shielded environment, to decrease magnetic field interference (noise) from electrical devices and other sources of magnetic fields. This was a major limiting factor in deploying these devices in a working environment especially considering, that most hospital wards will have numerous devices that can interfere with the device. The investigators will be evaluating the use of a portable magnetometer which measures the change in magnetic fields rather than an absolute magnetic field as measured by SQUID magnetometers used in the trials mentioned above. It has been developed to be more affordable and more feasible than SQUID magnetometers as it is designed to be operated at room temperature in an unshielded environment. The investigators will be evaluating its ability to measure parameters identified in previous literature as well as other novel parameters that may be identified from acquiring the MCG derivative. With the development of this portable magnetometer designed to be used in an unshielded environment, there is real potential for screening a large numbers of patients for SCD risk. Until this trial, this novel tool has not been evaluated in this role. MCG parameters in Sudden Cardiac Death (SCD) Whilst there are limited data on the role of MCG in predicting arrhythmic events, a series of studies involving patients with ischaemic heart disease have shown a correlation between MCG characteristics and the presence of ventricular arrhythmias. Specifically QRS fragmentation and late fields of the QRS have been associated with a higher incidence of ventricular arrhythmia. A trial of 49 patients with dilated cardiomyopathy demonstrated parameters present on MCG scans which were able to distinguish between participants, retrospectively, who had a ventricular arrhythmia in comparison to those who did not. The authors associated the features in the MCG T wave (specifically prolongation of the end part of the T wave) with the presence of ventricular arrhythmias. Kawakami et al prospectively studied ventricular arrhythmia risk in 51 patients with non-ischaemic cardiomyopathy for a mean follow-up of 2.9 years. They found that MCG left intraventricular disorganised conduction described as a deviation from the typical global clockwise LV depolarisation was predictive of major adverse cardiac events.. Proposed trial The aim of this trial is to show a correlation between features consistent with arrhythmogenic substrate from a VitalScan MCG and future ventricular arrhythmias; measured from observed arrhythmic events from ICD interrogation of patients at risk of SCD. The investigators hope therefore to describe MCG features most predictive of future ventricular arrhythmias. To achieve this aim the investigators plan to perform a multi-centre cohort trial in all patients referred to cardiology at University Hospitals Coventry and Warwickshire NHS Trust and University Hospital of North Midlands. In addition to usual care, participants will have lying and standing blood pressure measured, blood samples taken for the measurement of circulating vascular biomarkers and an MCG performed. Participants will then be segregated by whether their usual treatment pathway involves or has involved the implantation of an ICD. Those patients who do not require an ICD will not receive any further follow up, but will be used to form a control group of patients. Participants who have received an ICD will be observed for any arrhythmic events for a minimum of one year. At twelve months participants will be requested to complete a quality of life questionnaire; SF-36 to assess impact of symptoms on their quality of life. Twelve months after the recruitment of the last patient the first phase of the trial will conclude. The second phase of the trial involves long term follow up of participants having ICD implants, for duration of five years. This will be observational and participants will not be expected to be involved in any activity above and beyond standard care. Trial Summary The trial is a dual phase, multi-centre observational cohort trial, attempting to define the parameters of Magnetocardiography (MCG), with an aim to interpret the characteristics of these parameters, which can predict future ventricular arrhythmia and ICD therapies. Phase one will last a total of 30 months: 12 months to recruit patients, further 18 months to complete patient follow up and for analysis of data. If the recruitment target is not met at the 12 month time point, there will be an option to extend this period for a further 6 months. Phase two will involve long term follow up of the cohort of participants who receive an ICD. This will allow longer time for events requiring ICD therapy to occur. This will involve an annual data collection and reporting. This will continue for five years after the recruitment of the last participant. Study population: The investigators plan to recruit 510 prospective participants in total out of which 300 ±10% in the observation arm (as shown in Figure 1) and 210 participants in the control arm. This will ensure sample size integrity assuming a possible 10% loss to follow up. Prospective participants will be recruited from two sites. All trial visit and procedures will be conducted in the University Hospital Coventry and Warwickshire (UHCW) and University Hospital of North Midlands (UHNM) NHS Trusts.

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