A Multi-centre Observational Cohort Trial to Identify Magnetocardiography (MCG) Parameters in the Prediction of Future ICD Therapy

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..