A team from the University of Cape Town's Chris Barnard Department of Cardio Thoracic Surgery has developed a clever device to use during Coronary Artery Bypass Graft (CABG) surgery. Last week a patient from Groote Schuur Hospital became the first South African, and only the third in the world, to participate in a worldwide trial - the first step to widespread use of this breakthrough device. His surgery was undertaken at UCT Private Academic Hospital.
Dr Loven Moodley, one of the principal researchers on this project and one of the surgeons in the theatre, explains: “A CABG is an often used, successful surgical procedure that prevents fatal heart attacks. Unfortunately, like any open-heart surgery, it is not one you would want to repeat in a hurry.”
• Why it is needed
Dr Moodley explains why this is: “The first CABG was performed in the USA in 1967. Before that, treatment of blocked (occluded) arteries was limited to dietary and other lifestyle changes, and some medication, but it was often a losing battle. With CABG, surgeons bypass the narrowed arteries, which are narrowed by plaques that prevent blood from reaching the heart muscle in sufficient quantities. To bypass these narrowings, a vein is taken from a leg and sutured to the non-diseased part of the coronary artery on the heart after the obstruction and the other end is sutured to the aorta (the main artery leaving the heart to supply the body with blood).
“Today we know that the preferred bypass vessel is another artery (usually an artery from the chest wall is used), as they are accustomed to take the normal arterial blood pressure. Unfortunately, an artery may not always be useable and is limited to one or two grafts and many patients require four or more bypass grafts. This is the case in most patients, and the surgeons will opt for a vein, usually one taken from the leg.”
“But veins have their limitations. They are not used to the high pressure of blood that arteries have to bear, so in the immediate aftermath of surgery they will dilate. This can cause tearing on the inner walls of the vein - which renders the vein more susceptible once again to plaque build up. Often patients who have received vein grafts need repeat CABG surgery relatively in the years to come. Within one month, 10% of the veins are blocked; at one year, it is 20%, and by ten years, we are looking at almost 50% blockage of the vein grafts”.
The breakthrough device is aimed at preventing repeat CABG surgeries by addressing exactly this problem. Now a worldwide trial involving at least 120 patients is underway to test the results of the device. Every year, more than 1.2 million patients need a bypass operation world-wide. In South Africa alone, this new device has the potential of extending the life of a few thousand CABG patients every year.
• Making veins into arteries
Professor Johan Brink, who was also involved in the operation, says that, about ten years ago, researchers and surgeons of UCT's Chris Barnard Department of Cardiothoracic Surgery were brainstorming this problem. “Prof Peter Zilla, who heads our team and our Department, came up with the idea of reinforcing the vein with an external support to prevent dilatation of the vein graft. The project took off from there, but much basic and laboratory research was necessary to develop the exact elasticity of the external support to mimic that of an artery at physiological blood pressure.”
If the vein is surrounded by a substance which strengthens it and enables it to pulsate - to expand and contract - the way an artery does, researchers thought they would effectively be giving a vein some of the characteristics that make an artery the gold standard of CABG grafts.
Years of modeling, engineering and experimenting followed in Cardiovascular Research at the University of Cape Town. The research also involved collaboration with the Departments of Engineering and Mathematics at the University of Cape Town which did the mathematical modeling and some of the bio-materials research to come up with the ideal external vein support which would allow contraction and expansion exactly as in a normal artery. The team, lead by Prof Zilla, with the principal researchers being Drs Tommy Franz and Loven Moodley, developed a mesh woven of Nitinol (a nickel/titanium alloy) that is incredibly light (the total weight involved is less than a quarter of a gram) but very strong. “It will last forever,” says Professor Brink.
Drs Moodley and Franz said that, after testing the mesh's performance in non-living material, the team took it to animal trials. “We documented a dramatic reduction in the internal damage to the veins equipped with the mesh.” In fact, the Nitinol mesh gave outstanding results, so it is no surprise that a commercial partner with the funding to develop the product was found. With good animal data and rigorous scientific examination behind them, the time was right to do a trial in humans.
Patients are currently enrolled for the trial in Germany, Australia, and Singapore as well, to ensure a wide spread of patients around the world. Each patient will receive at least two grafts - one with the normal vein graft and the other with a Mesh supporting the vein graft. The patients will be monitored at one month, three months, and six months. At 12 months, they will have an angiogram to see if any damage and narrowing has occurred inside the vein walls and if any occlusion has taken place. A comparison between the vein grafts with and without the Mesh will be undertaken to prove or disprove the advantage of the Mesh support.
“We want at least 120 patients in the trial,” says Dr Moodley. “Once we have the numbers, we can analyse the data. If the outcomes are good, the Mesh can be taken to the market.”
• Working together
“It is part of our research initiative, and part of our policy to seek partnership with the public sector in this way,” explains Christo van Wyk Becker, general manager of UCT Private Academic Hospital.
He continues: “It is very fitting that, just over 40 years after the first heart transplant at Groote Schuur Hospital in December 1967, a research orientated heart surgery department bearing his name, and UCT Private Academic Hospital, should once again be doing cutting edge work in this field.
According to Dr Moodley the patient underwent a fairly straightforward CABG. “He received three grafts, one with the Mesh, one an unsupported normal vein graft and the other an arterial graft.”
If this innovative research performs as well in humans as it has done in the laboratory and in animals, it will give patients peace of mind, knowing that they probably would not have to undergo repeat open-heart surgery, and may stay healthy for many years more than they would have otherwise.
Released on behalf of UCT Private Academic Hospital
by Martina Nicholson Associates (MNA).
Martina Nicholson or Petro Lowies on 011 469 3016
