Electrostatic transducer of apexcardiogram

Apexcardiogram by mean of non-invasive method may be more usefull provided that the technique for the transducer attachment was easier and reprodusable. In this report, some attempts on the transducer of apexcardiogram were described. A precordial electrode was placed about 1.5 mm above the chest wall of a patient. The electrostatic capacitance between the electrode and chest wall was transmitted to the CR oscillator and it modulated the frequency of pulse train generated with the oscillator. The signals were led to a conventional D.C. recorder or a cathode ray oscilloscope. There was no remarkable differences of the wave pattern between the apexcardiogram obtained by our method and by conventional piezoelectric transducer in normal cases. In some patients, however, some differences were observed especially in the depth of O-wave. The depth of O-wave increased in accordance with a rise in pressure of the transducer to the chest wall using the conventional method. The observations suggest that the A/E-O ratio might be varied depending on attaching pressure of the transducer to the chest wall.