An analogue computer for pressure-time measurements in valvular heart disease

Accurate measurement of pressure differences across a diseased heart valve involves either laborious planimetry or elaborate digital computing facilities. An analogue device is described, simple and inexpensive to construct, which derives from the recorder input of two pressure signals the time (seconds/minute) of valve opening and the mean pressure difference during this time. Measurements may be repeated over long periods. The importance of using pressure differences as compared with peak or end diastolic gradients is noted; serious errors in assessment of valvular disease may otherwise occur.