From Big Medical Encyclopedia

MAGNETOCARDIOGRAPHY (a magnet + a cardiography) — a method of registration of time histories of a magnetic component of the electromotive force of heart. Unlike an electrocardiography, M. does not demand contact of the sensor of the device with a body inspected i.e. is a contactless method. In some cases M. can give information, new in comparison with an ECG. The method M. is intensively developed in the different countries, however did not find broad application in a wedge, practice yet.

For the first time the magnetocardiogram (MKG) was registered Bol and IAC-Fi (G. M of Baule, R. McFee) in 1963 by means of the induction detector consisting of two big coils and the chart recorder — the recorder. Then as the sensor began to use the toroidal coil with a large number of rounds, at the same time the basic possibility of registration of MKG about a wedge, was shown by the purposes. For registration the sensor of the magnetocardiograph is placed whenever possible closer to a thorax of the patient who is in a prone position or sitting. The signal from the sensor through the amplifier is registered on the recorder, in quality to-rogo it is possible to use the electrocardiograph. An indispensable condition of successful registration of MKG — absence at the patient of magnetic materials (steel teeth, hours, etc.) since the signal from them much more exceeds a signal of a magnetic component of the electromotive force of heart.

The MKG reminds an ECG and therefore at its description the main designations accepted for an ECG (are kept see. Elektrokardiografiya ). The maximum amplitude of the main teeth of MKG is registered at record from an anticardium. Comparative researches MKG and ECG showed that at extrasystoles and blockade of branches of a ventriculonector on MKG changes of a configuration of the QRS complex are quite accurately visible. Apparently, M. allows to register more accurately magnetic signals from close located sites of heart. In particular, it is established that in MKG the condition of a periinfarktny zone is reflected more stoutly, than in an ECG.

Two types of the magnetocardiographs differing on a way of fight against external hindrances are developed. The first type turns on the special shielding cameras where place the patient and the detector of the device. The second type of magnetocardiographs does not demand an ekranirovka; devices work in the mode of a gradiyentometriya, i.e. provide registration of a useful signal due to measurement of a gradient of magnetic field of heart in relation to external magnetic field.

In modern magnetocardiographs two types of converters (detectors) are used. The first of them is based on use of a superconducting contour and demands deep liquid-helium cooling for the work that maintains its superconductivity. The second type of detectors — converters with an optical rating in vapors of alkali metal of caesium — coolings in operating time do not demand.

Bibliography: Livanov M. N., etc. About registration of magnetic fields of the person, Dokl. Academy of Sciences of the USSR, t. 238, No. 1, page 253, 1978, bibliogr.; Cohen D. and. Ms With aug-h ap 13. Magnetocardiograms and their variation over the chest in normal subjects, Amer. J. Cardiol., v. 29, p. 678, 1972, bibliogr.; S an a r i n e n M. o. The mag-netocardiogram in cardiac disorders, Cardio-vasc. Res., v. 8, p. 820, 1974, bibliogr.

V. I. Belkevich.