• Research Initiatives Conference
• Coding & Reimbursement Course
• Vascular Annual Meeting
• CME Mission
• VESAP
• Calendar of Pages

Home > Medical Professionals > Research Initiatives Conference > Poster Abstracts Accepted > Choudry An Implantable Flow Sensor

An Implantable Flow Sensor for In Vivo Bypass Graft Surveillance

Rashad Choudry¹, John Blebea¹, Marat Goldenberg¹, Michael Salvatore¹, Patrick Kelly¹, Krish Soundararajan¹, Thomas Chilipka², David Vilkomerson^2
1Temple University, Philadelphia, PA;²DVX, Princeton, NJ

Objectives: Bypass graft surveillance has historically depended on the use of external duplex ultrasound to measure peak systolic velocity as an indicator of focal stenosis and as a surrogate marker of blood flow. Although useful, this technique is limited by the need for expensive ultrasound units, skilled technologists, and limitations in the frequency of reimbursable examinations. We have successfully developed an implantable Doppler sensor utilizing angle-independent diffraction-grating transducers (DGT) which are small enough to be embedded within the wall of standard synthetic polytetrafluoroethylene (PTFE) vascular grafts and can reliably measure both velocity and blood flow volume in vitro. We studied their in vivo feasibility in iliofemoral bypass grafts in dogs.
Methods: Mongrel dogs (n=6, ages 1-2 years, weight 18-25 kg) underwent ilio-femoral arterial bypass via a transperitoneal approach under general anesthesia. A standard 6 mm PTFE graft (Boston Scientific) was placed in an end-to-side fashion between the common iliac artery and common femoral artery. The distal common iliac and proximal common femoral arteries were ligated so that all flow to the leg was via the implanted graft. Incorporated within the wall of the graft, 6.5cm beyond the proximal iliac anastomosis, was a 20 MHz DGT transducer measuring 3.5 mm long, 1 mm wide, and with a thickness of 275 microns (DVX IIc, Princeton, N.J.) Two micro-coaxial cables from the sensor were tunneled retroperitoneally and cranially exiting to a Universal Serial Bus (USB) port at the back of the neck. Beginning intra-operatively and daily post-operatively, the USB port was connected to a laptop computer and blood velocity and flow in the graft was measured and digitally recorded in both the standing and sitting positions. A standard duplex ultrasound (Logiq 7, GE) was utilized to confirm graft patency and flow intra- and post-operatively.
Results: Bypass grafting was successfully performed with patent grafts in all animals. Blood velocity and flow measurements within the grafts utilizing the DGT transducer demonstrated reproducible measurements in all animals with an expected increase in both velocity and flow seen beginning on the first post-operative day reflective of reperfusion hyperemia (p < 0.001 ANOVA; Graph). There was a significant increase in both velocity and flow in the standing as compared to the sitting position (p < 0.001). Duplex ultrasound confirmed the status of the grafts in all cases.
Conclusion: Implantable in-graft DGT sensors can successfully measure both velocity and blood flow in vivo. They provide the potential for future use in humans to monitor bypass graft status through the use of wireless radiofrequency data transmission.