The Recording of Cardiac Movements and Sounds by the Roentgen Ray (Kymophonoroentgenography)

Part 1 Our knowledge of the movements of the heart is based on animal experimentation, on transitory observations of the opened chest, and on examination by roentgen-ray methods. Fluoroscopy, technically the simplest of the roentgen methods, throws little light on this subject, because the rapidity and complexity of the movement makes an accurate analysis difficult. Cinematography, either by photography of the fluoroscopic image or by direct serial roent genography, is impractical for routine studies and is complicated both in technic and analysis. There is now available, however, a simple graphic method of obtaining a permanent record of the movements of the heart on a single film. Essentially, this method is roentgenography through a slit diaphragm placed close to the object in motion, the recording film not being at rest as in ordinary roentgenography but moving at a constant rate of speed, at right-angles to the direction of the slit. Thus if the slit is horizontal the film moves in a vertical direction; if the slit is vertical, the film moves horizontally. The motion of the object in front of the slit is recorded on the film in the form of a wave or curve. For the study of the movements of the heart by the single slit method the anterior thorax is placed against a lead plate having a slit several millimeters wide. By the aid of the fluoroscopic screen, the slit is so adjusted that it crosses the cardiac shadow at a desired level. The tube is placed behind the thorax, with its focal spot at the level of the slit. Fluoroscopy will now show the pulsating band-like shadow of a narrow section of the heart (Fig. 1-A). If the fluoroscopic screen is replaced by a film, moving at a regular rate in a direction at right-angles to the slit (Fig. 1-B), the moving cardiac shadow will be projected on the film as a continuous band whose edges bear waves corresponding to the movement of the particular portions of the heart exposed in the slit. The length of a record made in this way is limited only by the length of the film. Such a single slit kymogram can trace the movement of only one or two points of the heart surface. It has the additional limitation of giving neither the general form and contour of the heart, nor the morphology of the other thoracic structures.2 In the multiple-slit method, the lead sheet against which the thorax is placed has many equally spaced slits (Fig.1-C). The length of the record of movement, of the particular part exposed in the various slits, is now necessarily limited in order to avoid overlapping of the records (Fig.1-D). The exposure is, therefore, limited to the time it takes the film to move a millimeter or so less than the distance between the slits. The length of the individual records is limited, therefore, but by making the slits narrow and decreasing the speed of motion of the film, a number of waves of each point sufficient for practical study may be obtained.