The artificial heart: pursuit of a noninvasive method for determining atrial pressures

The use of conventional open-port catheters in total artificial heart (TAH) research shortens the survival time of recipients owing to sepsis and embolism caused from the catheters. Valuable data are lost when an open-port catheter clots off, and transducer position must be keyed to the level of the atria for accuracy. The need for an accurate, easily obtainable, noninvasive method for measuring atrial pressure is of obvious value. Such a method has been developed in vitro using a device that measures the stroke volume of a pneumatic ventricle. The stroke volume is obtained by quantifying the amount of air exiting a pneumatic TAH in diastole. Using this information ventricular filling rates can be calculated by the stroke volume measurement device, and these rates are correlated to measured atrial pressures. There is no need to continually adjust transducer levels in relation to the atria with this system. The data show an average percentage error of 2.4 of full scale (25 mm Hg) or 0.6 mm Hg. The method of measurement is accurate, without limitations on driving parameters. The information is available without any additional prosthetic fabrication or surgical intervention than that already needed for basic TAH implantation. This method of measuring atrial pressures now needs to be proved effective in vivo.