Schmitz-Rode T, Schnakenberg U, Pfeffer J G, Piroth W, Vom Bögel G, Mokwa W, Günther R W
Clinic for Diagnostic Radiology, University Hospital, Aachen University of Technology, Aachen, Germany.
Rofo. 2003 Feb;175(2):282-6. doi: 10.1055/s-2003-37232.
Development and experimental evaluation of an intravascular monitoring system for telemetric measurement of blood pressure and heart rate.
The monitoring system consists of an implantable silicone capsule (diameter 2.3 mm), containing a dedicated microchip with pressure sensors and signal-processing circuits as well as an antenna for wireless data and energy transfer using 6.78 MHz transponder technology. Three self-expanding legs at one end of the capsule served as a mechanism to lock the capsule at an arterial branch. A flow model, driven by a ventricular assist system, was used for testing and optimizing the implantation equipment, for checking the anchoring mechanism and for ensuring transmission of the measured pressure to the readout unit. In-vivo experiments were performed in 8 minipigs (weight 25 to 30 kg), with three capsules placed in each minipig via the femoral artery using a dedicated 8-F sheath/pusher system. Follow-up was by CT angiography for up to 6 months after implantation.
Flow model tests revealed a maximum deviation of pressure and heart rate measurements of 5% from the reference measurements. Signal transmission was reliable over a distance of 3 to 4 cm. Fluoroscopically guided in-vivo implantation of the capsules was simple and straightforward. In arteries with a diameter of 5 to 6 mm, the capsules were permanently fixed with one or two legs interlocked in side branches and without occlusion within 6 months. Three capsules developed a small non-occlusive appositional thrombus attached to the downstream (leg) part of the capsule.
Our in-vitro and in-vivo experiments demonstrate the feasibility of wireless transmission from a capsule with a sufficient resolution of the sensor output signals to determine blood pressure and pulse rate. As long as the vessel diameter is wide enough, arterial fixation of the capsule does not induce thrombotic occlusion of the parent artery. With respect to future clinical applications, further refinements of the transmission technology are needed to extend the transmission distance between capsule and reader antenna. The technology of intelligent implants has further implications, such as monitoring of other physiological parameters, and the design of a control loop, which may be used for therapeutic feedback.
开发并实验评估一种用于遥测血压和心率的血管内监测系统。
该监测系统由一个可植入的硅胶胶囊（直径2.3毫米）组成，其中包含一个配有压力传感器和信号处理电路的专用微芯片，以及一个使用6.78兆赫兹应答器技术进行无线数据和能量传输的天线。胶囊一端的三条自膨胀支腿用作将胶囊锁定在动脉分支处的机构。由心室辅助系统驱动的血流模型用于测试和优化植入设备、检查锚定机制以及确保将测量的压力传输到读出单元。在8只小型猪（体重25至30千克）身上进行了体内实验，使用专用的8F鞘管/推送器系统通过股动脉在每只小型猪体内植入三个胶囊。植入后通过CT血管造影进行长达6个月的随访。
血流模型测试显示，压力和心率测量值与参考测量值的最大偏差为5%。信号在3至4厘米的距离内传输可靠。在荧光镜引导下进行胶囊的体内植入操作简单直接。在直径为5至6毫米的动脉中，胶囊通过一两条支腿锁定在侧支内而永久固定，6个月内无阻塞。三个胶囊在胶囊下游（支腿）部分形成了一个小的非阻塞性附着血栓。
我们的体外和体内实验证明了从具有足够传感器输出信号分辨率以确定血压和脉搏率的胶囊进行无线传输的可行性。只要血管直径足够宽，胶囊的动脉固定不会导致母动脉血栓性阻塞。关于未来的临床应用，需要进一步改进传输技术以延长胶囊与读取器天线之间的传输距离。智能植入技术还有其他意义，例如监测其他生理参数以及设计可用于治疗反馈的控制回路。
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