Abstract:

Left ventricular assist devices (LVAD) are implantable mechanical blood pumps providing circulatory assistance for patients in heart failure, and are currently being investigated as a long-term alternative to cardiac transplantation. While effective in short term use as a bridge to transplantation, the durability of the device for extended use has yet to be demonstrated. To prospectively follow the mechanical status of the devices, biweekly transabdominal acoustic readings from a standard microphone and accelerometer are obtained. Time-domain analysis of the recordings allows the timing of ejection (device systole) and passive filling (device diastole) to be measured. Ejection duration was measured at 240 ms in 11 new devices and exceeded 300 ms in two aging devices which subsequently failed within 3 weeks of measurement. Frequency-domain analysis showed the presence of a 230-Hz signal in both failing devices, possibly indicative of bearing wear within the motor. In addition, a 50-Hz signal present in all properly functioning devices was missing in one of the devices which failed. Acoustical analysis will play a vital role in the continuing care of LVAD patients and will allow a more rapid and noninvasive method of assessing device status.