1. Improving Coronary Artery Bypass Surgery
Lucas Burton1, Amir Durrani1, Benjamin Hoagland1, Santosh Tumkur1
Advisors: Thomas Ryan, Ph.D.2; Jia Hua Xiao, Ph.D.2; Paul King, Ph.D.1
1 Department of Biomedical Engineering, Vanderbilt University, Nashville, TN
2 Ethicon Inc., Johnson & Johnson, Somerville, NJ
Anastomosis Device
Localized Stabilization Device
Overview Of CABG
Device Description
The intravascular vessel connector device consists of a hollow, semi-cylindrical base with a hollow stem attached at 45o. The base is designed to slip into an incised coronary artery with a harvested vessel attached to the stem. The two central rings on the stem are designed to provide a site for securing the harvested vessel using lateral sutures. The top ring is designed to create a seal to prevent blood from escaping outside the device to the thoracic cavity. All edges are rounded so as not to puncture the inner wall of the vasculature.
·        Coronary Artery Bypass Graft
·        Procedure to introduce increased blood flow to occluded coronary arteries
·        Harvested vessels grafted to coronary arteries
·        Complex suturing techniques required
·        Can be done on-pump or off-pump (see figure)
Figure 1. Heart with coronary bypasses. Occlusions in arteries are indicated
Device Description
The improved stabilization device consists of two suction fingers with two chambers each. The fingers are attached to an expandable base made of stainless steel which, in turn, attaches to Ethicon’s FLEXSITE® stabilizer arm. The base is mounted on a track which expands up to 1cm via a turnbuckle mechanism located on the posterior end of the device. The turnbuckle is coated with silicone to promote easy rotation. Additionally, each of the four suction chambers are fed by a separate tube from a main suction source.
Market Potential 
·        150,000 Off-pump CABG surgeries performed worldwide each year
·        25% of all CABG surgeries are off-pump
·        Charge for a CABG procedure ranges from $37,000 and $72,000 per case
·        $26 Billion spent per year on CABG surgeries
·        Beating heart techniques have increased more than 40% each year since 1997
Figure 5. Our improved Stabilization Device (above). Ethicon’s original vacuum stabilizer (below).
Modifications & Improvements
·        Improved vacuum system
    -Places vacuum lines in parallel to prevent dislodging when one chamber loses contact with tissue surface
·        Introduction of lateral stabilization
-Further stabilizes grafting site by placing lateral tension on tissue through use of turnbuckle spreader
Problems To Be Addressed 
·        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
·        Heart positioning problems
·        Heart hemodynamics
Figure 2. Conventional vessel connection technique
How It Works
In this revolutionary technique, the upper shaft is inserted into the vessel to be grafted and secured with BioGlue® from Cryolife Inc. or sutures placed in a circular fashion. The device is then inserted into an incision in the coronary artery, with the base designed to be longer than the incision. Once the device is inserted, an outward force is applied to stabilize the two vessels in close proximity so they can be easily sutured or joined with BioGlue®.
Figure 4. Vessel Connector dimension specifications
Figure 6. Stabilization device closed (above), and fully expanded (below).
Figure 3. View into the chest cavity during CABG
Design Goals 
·        Eliminate or reduce suturing difficulty ·        Design device to promote efficient grafting
·        Improve harvested vessel attachment
·        Maximize local stabilization
Why Is PEEK™ Our Material Of Choice?
Compared with other biocompatible polymers, PEEK™ exhibits superior tensile strength and flexural strength. PEEK’s™ fatigue limit is high, in coordination with its impact strength. Moreover, PEEK™ will not affect MRI studies conducted on patients.   
How It Works
The device will be attached to the Ethicon’s FLEXSITE® stabilizer arm which allows the device to be locked in place on the surface of the heart, around the coronary artery. Once in place, a suction is applied through the device to create a pull tension on the surgical field. The turnbuckle is then rotated away from the surgical field to spread the fingers of the device and create lateral stabilization of the grafting site. Furthermore, if one of the suction chambers should dislodge, the local stabilization will not be affected as the other chambers will maintain suction with the improved vacuum system.
Polyetheretherketone™ (PEEK™) Properties
Figure 4. Calculation of approximate suction pressure necessary for stabilization
Safety Considerations
·        Tissue damage from expansion of base
·        Suction damage on heart’s surface
·        Detachment of harvested vessel from coronary artery
·        Puncture of vasculature by device
·        Biocompatibility
·        Clot Formation
Tensile Strength (73 °F)
Flexural Strength (73 °F)
Compressive Strength (10% Deflection)
Shear Strength (73 °F)
Limiting PV
9.99 x 107 Pa
1.70 x 108 Pa
1.17 x 108 Pa
5.30 x 107 Pa
1.38 x 108 Pa/FPM
Acknowledgments
This project was made possible through the help of the following individuals:
Thomas Ryan, Ph.D.; Jia Hua Xiao, Ph.D.; Paul King, Ph.D.; Duco Jansen, Ph.D.; Walter Merrill, M.D.; James Greelish, M.D.; Bruce Hoagland; Randy Ryan