A Blood Pressure Sensor for Long‐Term Implantation

Abstract

An implantable flow-through blood pressure sensor prototype has been developed for use with an implantable left ventricular assist device (LVAD). This sensor incorporates a flat pressure-sensing diaphragm that is designed to be integral with the wall of a titanium tube that may be placed in the inlet or the outlet flow path of any LVAD. The interior tube flow geometry is transitioned from a round to a D-shape such that flow separation is eliminated. Bench testing of 3 sensors was performed to characterize the sensor. The worst-case results showed a maximum nonlinearity of 0.64 mm Hg, a maximum hysteresis of 0.87 mm Hg, and a maximum nonrepeatability of 0.87 mm Hg. Long-term drift studies of 2 sensors at 193 days and 112 days resulted in a projected annual drift rate of 1.4 and 2.0 mm Hg, respectively. The APEX pressure sensors were evaluated in 5 ventricular assist acute calf experiments in which the sensor outputs were compared with Millar pressure catheter sensors. Pressure output comparisons showed similar pressure tracings. No visible evidence of thrombus formation was found on the APEX sensor compared with thrombus formation found on the Millar catheter at the entrance to the flow path. Tests demonstrated that the blood pressure sensor can accurately measure blood pressure and indicate that it has long-term stability.

Advanced Suction Detection for an Axial Flow Pump

“…The direct way to detect the occurrence of ventricular collapse would be through the use of a reliable pressure measurement; one project was reported (12) in which a strain-gauge-bridge which was built into the concave interior wall of a tubing cannula was used. With this system, low drift and no thrombus formations in an acute animal experiment were reported.…”

Management of ventricular arrhythmias in patients with ventricular assist devices

“…Moving forward, additional studies relating the clinical occurrence of ventricular arrhythmias to molecular and physiological shifts within the myocardium will be invaluable in better defining which mechanisms are most strongly implicated in the time-dependent risks of ventricular arrhythmias in VAD-supported hearts. Further device evolution, including inflow cannula modifications [19,63] and inlet pressure control systems that adjust rotor speeds and prevent suction [23,[64][65][66], may reduce the incidence of ventricular arrhythmias among VAD-supported patients. Prospective trials assessing the benefits of de-novo prophylactic ICD placement and the need to replace ICDs in patients free of post-VAD ventricular arrhythmias would be particularly welcome.…”

In Vitro Evaluation of an Axial Flow Pump: Mock-Pump Interaction and an Approach to Control

“…Control algorithms based on pressure indicators have been proposed (9,10). Blood pressure sensors for long-term implantation that could be integrated into the pump or cannula should be developed from recent technologies (32). These sensors have demonstrated stability during acute in vivo studies.…”