Noninvasive detection of ventricular wall motion by electromagnetic coupling. Part 2: Experimental: cardiokymography.
The cardiokymograph or displacement cardiograph (DCG) is a noncontacting device which senses movement of the heart throughout the cardiac cycle by the interaction of a radiofrequency (10-20 MHz) electromagnetic field, generated by a sensing coil, with the thorax. In the paper three different techniques of detecting this movement will be discussed: monitoring the changes in sensing resonant frequency (FM modulation), monitoring the changes in impedance of the coil at resonant frequency (AM modulation) and a new technique which monitors the changes in coil impedance at fixed frequency. The sensitivities of these three techniques will be compared. A simplified theory of the mode of coupling between the coil and the thorax will be studied in terms of a transformer model. Preliminary clinical measurements of anterior left and right ventricular motion will be given. The presence of higher-frequency features related to atrial motion and the opening and closing of the aortic and pulmonary values will also be described.
Pepper
M G
MG
Electronic Engineering Laboratories, University of Kent, Canterbury, UK.
Taylor
D J
DJ
Kwok
M C
MC
D004574:Electromagnetic Fields; D006321:Heart / Q000502:physiology*; D006801:Humans; D007734:Kymography / Q000379:methods*; D008433:Mathematics; D008954:Models, Biological; D009068:Movement