Data Recording Procedure

The subject (patient) is prepared for data recording by removing from his/her garment and body all magnetic, electronic and larger metallic objects (credit cards, watch, keys, bracelets, removable dentures, etc.). Subjects with implanted electronic devices, such as a pacemaker or defibrillator are excluded from MCG testing since signals of such devices may produce significant artifacts in the MCG recordings. The patient is then placed in a supine position on the bed with three (1-lead) EKG electrodes attached to both wrists and the left leg. The 1-lead EKG signal is used as a convenient reference for averaging MCG data. After the subject is properly positioned the operator sets and fastens the two stop keys of the bed, which determine the four measurement positions.

Next, the operator takes MCG and EKG recordings sequentially at the four defined bed positions. During all recordings the subject is breathing normally, but refrains from any conscious change in body position, from talking, etc. Prior to the recordings, the operator lets the MCG software adjust the system automatically, and verifies on its virtual oscilloscope that all channels are operating properly, and that the real-time data observed are sufficiently free from disturbance overloads. The operator shifts the bed manually after each recording. Depending on the electromagnetic environment, the operator can choose a recording time from 30 to 90 seconds for each position to accumulate enough cardiac cycles for averaging. After successful recordings at the four positions, the operator filters and inspects the raw data to eliminate occasional artifacts due to external, transient electromagnetic disturbances. Subsequently, recorded data are averaged over 30 to 90 heart beats using the EKG signal template as a reference†. Typically, the whole test, including patient preparation, lasts between 5 and 15 min. Data processing and analysis require an additional 5 to 15 minutes. Physiological MCG stress testing can be performed either by using pharmacological stress, at a given level of stable heart rate, or by making the recordings shortly after exercise stress, once the heart rate normalizes sufficiently to make signal averaging possible.