High-fidelity, infinite time constant calibrated pressure apexcardiogram and its correlation with high-fidelity left ventricular pressure.

A technique of recording the pressure apexcardiogram by means of a high-fidelity piezo- resistive transducer has been developed in our laboratory. It permits the quantification of pressure with which the transducer is applied to the chest wall as well as the pressure changes during a cardiac cycle. In this preliminary report, apexcardiographic pressures were compared with simultaneously recorded high-fidelity left ventricular pressure in 32 patients. There were no significant differences in the timing of the left ventricular systolic upstroke and the "O" point. Peak dP/dt of the apexcardiogram occurred (10 13 ms) significantly earlier than the intraventricular pressure recordings. Though there was a correlation between developed diastolic pressure (end-diastolic minus early diastolic pressure) measured by the apexcardiogram (20 14 mmHg) and intraventricular pressure recordings (116 mmHg), the former was significantly higher. Pressure overshoots in early and late diastole contributed to this overestimation by the apexcardiogram but the relative contribution of each phase varied from patient to patient. There was a similar correlation between systolic pressures, but this index tended to be underestimated by the apexcardiogram.