Long-term intravascular blood-pressure monitoring with a novel, wireless sensor system - results from chronic in-vivo studies

Background: Long-term blood-pressure (BP) monitoring is a vital necessity for physicians to prescribe appropriate medical treatment for malign hypertension patients in order to reduce the incidence of secondary consequences such as stroke, kidney failure or heart insufficiency. However, current devices are still not suited for long-term measurement (several weeks to months). Moreover, they usually measure the peripheral blood pressure which significantly differs to the central blood pressure known to be the better indicator for vascular diseases. In order to address this need, we developed and conducted in-vivo tests on a novel, fully-implantable, wireless blood-pressure monitoring system. Methods: The monitoring system was tested for six months in 12 chronic ovine models. The sensor was implanted with X-ray-control in the femoral artery by means of a dedicated sheath (PASIS). Reference measurements were recorded with gold standard pressure sensors after implantation. Position and proper functioning of the sensor were controlled via regular readout measurements and CTs. At the end of each trial, a histological examination was conducted. Results: Chronic in-vivo studies revealed that blood pressure measurement over a period of six months was possible with the novel implantable sensor system. Stable pressure histories were recorded. However, the mechanical resilience of the sensor system requires improvement. The in-vivo tests in the femoral artery of sheep produced high stress on the sensors system. Several implanted systems became inoperative despite efforts to stiffen the sensor-cable. The histological analysis detected no thrombi. Mild inflammatory reactions were found at the vessel insertion site in several cases. Conclusions: The results of the chronic in-vivo tests on the novel fully-implantable blood-pressure monitoring system were encouraging. Improvements need to be made regarding the mechanical resilience of the system and the coating. Additional trials at a modified implantation spot will be conducted in order to reveal further insights regarding system performance.