1. Improving CABG Surgery
Amir Durrani
Ben Hoagland
Santosh Tumkur
Lucas Burton
Advisor: Thomas P. Ryan, Ph.D.

2. Project Goals Improve harvested vessel attachment
Design device to aid in grafting
Reduce suturing difficulty
Improve local stabilization

3. Overview of Off-Pump CABG
Coronary Artery Bypass Graft
Procedure to introduce increased blood flow to occluded coronary arteries
Harvested vessels grafted to coronary arteries

4. Market Potential
150,000 Off-pump CABG surgeries performed worldwide each year
Charge for a CABG procedure ranges from $37,000 and $72,000 per case
$26 Billion spent per year on CABG surgeries
Use of beating heart techniques has grown more than 40% each year since 1997

5. Problems Stabilization is required to perform CABG on a beating heart
Effective vessel-artery contact is imperative
Complex suturing techniques required
Current stabilizers don’t provide adequate local stabilization of graft site
Heart positioning problems
Heart hemodynamics

6. Device Evolution

7. Schematic

8. Anastomosis Device – Final Design
Shaft inserted into vessel that is to be grafted and secured with sutures or glue.
Base will then be inserted into the coronary artery
Device will adhere to the coronary artery at the upper surface of the base,
BioGlue® will be used to secure device to coronary artery
Shaft inserted into vessel that is to be grafted and secured with sutures or glue.
Device will then be inserted into the coronary artery; folding of base allows for easy insertion
Device will adhere to the coronary artery when the upper surface of the base, containing an adhesive, is brought in contact with the upper inside surface of the coronary artery. 

9. Anastomosis Device (cont.)
With vessels in close proximity, suturing is made easier
Lateral sutures can be secured between rings to prevent vessel from dislodging from device
Alternative method of anastomosis would involve application of BioGlue® around vessel junction to seal anastomosis
The two vessels are now stabilized in close contact with one another and can be easily sutured together. 
Alternative method of anastomosis would involve application of bio-glue to the upper surface of the cylindrical base    

10. Anastomosis Device
Upper ring to create a seal to prevent blood flow from escaping outside the device to the thoracic cavity
All of the edges of the device are rounded so as not to puncture the internal wall of the vasculature

11. Proposed Device Materials
Currently, the device will be made entirely of polyetheretherketone (PEEK)
An advanced polymer that can be plastically deformed
Anastomosis will be augmented by BioGlue®, manufactured by CryoLife®, Inc.
BioGlue® can attach vessels and seal suture holes
Designed for use in anastomosis

12. Stabilizer Foot Calculations
Assumption: stabilized site is 2 cm x 3.5 cm
Simplified modeling of heart as fluid filled sphere
Concentrate on quarter sphere

13. Determine Hoop Stress FL = P x ((πd2)/4) Fm = (πdt) x σh
Hoop stress: σh x πdt = P x [(πd2)/4]d
σh = (Pd)/(4t)

14. Localizing the problem

15. Anastomosis Site and Fs
Fm = 2 (l x h)* t * σh
Fp = (l x h) P
Fs = Ps (l x h)
2 (l x h)* t * σh = (l x h) P + Ps (l x h)
Ps ~ 2P or approximately 240 mmHg

16. Vessel Connector Material Calculations
Surface area of the device is mm2 (1.961e-4 m2)
Approximated as a flat plane
Maximum experimental pressure ~560 mmHg
lower limit PEEK tensile strength 52.5e4 mmHg
52.5e4 mmHg/ 560 mmHg = 937.5
Tensile strength well above the 560 mmHg pressure constraint

17. BioGlue® Will replace sutures (or reduce number needed)
Comprised of cross-linked proteinaceous material
High strength
Strong rapid bonding between tissues
Strong rapid bonding between tissue and synthetic materials
Stronger than conventional fibrin adhesives

18. BioGlue® Composition Cross-linking on a surface
Water soluble proteinaceous material (27-53% by weight)
Di- or polyaldehydes (weight ratio: 1 part to every parts of protein
Water insoluble rubbery or leathery proteinaceous solids (free of aldehydes)
Tear strength of at least 75 g/cm^2

19. Stabilizer Improvement
Modification to suction stabilizer
Provides improved lateral stabilization
Implements a turnbuckle
Spreads tissue up to two centimeters beyond closed position
Improved vacuum system which implements four lines in parallel.

20. Stabilizer Foot Images

21. Progress Made Completed SolidEdge® design of our prototype
Finished DesignSafe™ Analysis
Settled on polyetheretherketone (PEEK) as our polymer of choice for our vessel connector device
Contacted Brian Cox of the Vanderbilt Technology Transfer Office concerning licensing and patents

22. Current Status
In the beginning process of obtaining a patent with help from the Tech. Transfer Office
In the process of having our vessel connector prototype built by the University of Pittsburgh
Stabilizer is currently being built by outside machine shop source
Final Report

23. Future Plans Begin design of poster for final presentation
Obtain stabilizer foot from machine shop and prototype from University of Pittsburgh
Continue consultation with surgeons and engineers for feedback
Acquire BioGlue® sample from Cryolife®, Inc.
Finish final report

24. Recommendations
Perform extensive stress and material testing of anastomosis device and foot
Investigate other possible materials for anastomosis device
Explore other possible vessel connector designs or improvements
Obtain further feedback from doctors
Acquire test data with foot and anastomosis device