[Instrumentation and methods in policardiography (author's transl)].

Although policardiography has been in use for more than a century, only recently attention has been focused on instrumental and methodological problems of the technique. Among these, frequency response and time constant of the equipment are in first place. Time constant must be long enough to allow an accurate recording of the low and ultra-low frequency vibrations which are generated in the cardio-aorto-hemic system, in particular of those constituting the carotid pulse and the apexcardiogram. The authors stress the influence that incidental air leaks in the recording assembly, or type and size of the pickup device, have on the value of the time constant. Kinetocardiography seems preferable to apexcardiography in order to reproduce with higher fidelity absolute movements of the anterior thoracic wall in every single point.