Magnetocardiography (MCG) in Subjects Undergoing CT Angiography (CTA)

Cardiomagnetism refers to the detection, analysis and interpretation of the magnetic fields generated by the electrical activity of the heart. The peak value of the magnetic fields of the heart is more than a million times smaller than the Earth's magnetic field. A major breakthrough in the capability of measuring such small fields came with the invention of the SQUID (superconducting quantum interference device) in the late sixties. The first magnetocardiograms (MCGs) measured with the SQUID were recorded by Cohen et al. in 1970. These earlier measurements were performed in very expensive magnetically shielded rooms, initially utilizing only one or two SQUID probes. In the eighties this technology was tested in several laboratories creating a magnetic field map by moving one SQUID sequentially above the chest to create an image of the whole hearts magnetic field. These maps were then attempted correlated with various pathologies (1).

Since then the technology has been greatly improved and several multi-channel machines are in use across the world for research purpose for arrhythmia localization and ischemia detection. However, at present time, only one company (CardioMag Imaging, Schenectady, New York) has developed a machine that operates outside a shielded room.

The CardiomagImaging (CMI) Magnetocardiograph (MCG) is capable of noninvasive recording of magnetic fields arising from the electrical activity of the heart with very high spatial and temporal resolution. The temporal trace of the MCG is analogous to an ECG, and, similarly, can be recorded in multiple leads. This MCG device has been specifically developed for the general purpose (outside shielded room) of non-contact, non-invasive diagnostics of ischemia.

The CMI MCG device has been approved by the FDA as a safe tool to measure and record the magnetic field arising from the heart's electrical currents. It is awaiting FDA approval for the specific diagnosis of ischemia in chest pain patients (2,3).

We have been using the CMI 9-channel MCG for detection of ischemia in patients admitted to Cedars-Sinai Medical Center for acute chest pain syndrome. The results are very exciting and have been published in abstracts and one manuscript, with another manuscript in submission (4,5). In summary, we studied 75 patients with acute chest pain and 65 healthy volunteers and found a very strong association with an abnormal MCG scan and ischemia (p<0.0001). The sensitivity, specificity, PPV and NPV was 87.1%, 85.7%, 64.3%, and 95.7%, respectively. In comparison, the diagnostic value of the stress SPECT imaging was 91.3%, 75.0%, 75.0%, and 91.3%, for sensitivity, specificity, positive and negative predictive value, respectively. These results were achieved without the use of stress provocation, contrast administration, or any ionizing radiation, and the results were available immediately.