Closed chest coronary surgery on the beating heart: technical development of an automated bypass grafting method (UGN.4183)

The aim of this project is to develop an automated end-to-side coronary artery bypass grafting method for application to the beating heart.

Atherosclerotic narrowing of the coronary arteries leads to ischemic heart disease. If medical treatment is inadequate, either recanalization by e.g. a balloon dilation catheter is indicated or surgical revascularization by attaching one or more additional supply vessels (bypass grafts) to coronary arteries distal (downstream) to the obstructions.
In the current Coronary Artery Bypass Grafting (CABG) procedure, the heart is globally arrested to allow precise coronary artery bypass surgery on the large coronary arteries which are located at the outside of the heart wall. To permit cardiac arrest, the patient is connected to the heart-lung machine. To reach the heart and the great vessels, the chest is opened by sawing through the breastbone (midsternotomy). CABG surgery is major surgery with inherent risks of complications, morbidity and mortality, which are to be attributed in part to the use of the heart-lung machine.

In 1993, a research and development program on Minimally Invasive Coronary Artery Bypass Grafting (MICABG) was initiated in Utrecht. The ultimate objective of this program is to develop coronary artery bypass surgery on the beating heart (without heart-lung machine) through small key-holes between the ribs (thoracoscopic procedure).
Abolishing the need for the heart-lung machine is of great potential benefit to CABG patients. Reduction of the surgical access opening will further reduce hospital stay and accelerate convalescence. MICABG is likely to yield the earlier return of patients to normal activities (in 2-3 weeks compared to 2-3 months at present) and is expected to reduce the costs of treatment per CABG patient.

A thoracoscopic MICABG procedure requires assist devices for

1. restraining cardiac motion at the coronary anastomosis site,
2. automation of the method to connect the donor vessel (graft) to the recipient coronary artery,
3. diagnostic imaging of coronary arteries from the cardiac surface and
4. optimal access and navigation.

The problem of restraining the motion of the beating heart at the coronary anastomosis site has recently been solved by development of a suction device ('Octopus') which is capable of restricting the surgical target site motion to a cube of 1×1×1 mm. The Utrecht 'Octopus' immobilization method has been introduced in the treatment of coronary bypass patients in September 1995. By June 1996, the 'Octopus' method has been applied successfully in 25 patients.
The present project focusses on the development of a method which will enable automated grafting of the donor artery to the recipient coronary artery of the beatingheart. Three issues need to be addressed:

1. bonding of the donor artery to the recipient coronary artery,
2. making an arteriotomy in the recipient coronary artery and
3. positioning and fixation of grafting devices at the bypass site.

To direct the design process, the tools and elements as well as the resulting mechanical properties of the anastomosis will be modeled. Both analytical simulation and finite element analysis will be used as mathematical tools for this purpose.
In vitro and in vivo animal experimentation will provide immediate feedback after each design modification of grafting devices or its constitutive elements.

Several options for grafting have been evaluated. A modified glue has been examined in vivo using pigs as a model. Compared with conventional techniques, glueing was 5 times faster, whereas the histology of the bond and the angiography are similar.

Measurements on artery models, evaluation of handmade anastomoses and literature studies have resulted in better defined boundary conditions for micro-mechanical bonding. It appeared to be necessary to extend the modelling of arteries from 2D to 3D representation and to include the fine structure of the vessel.

The group succeeded in modelling a 3-D anastomosis. Designs of anastomosis facilitating devices found in patent literature, have been evaluated and compared with own designs.

The first designs for an anastomotic device have been tested. They proved to be fit for patent application.

Er zijn 1 bedrijf, 2 ziekenhuizen, 1 onderzoeksinstelling en 2 andere universiteiten bij dit project betrokken.

Prof.dr. C. Borst
UMC
Afdeling Experimentele Cardiologie
Postbus 85500
3508 GA UTRECHT