Bioresorbable scaffolds versus metallic stents - interview with Patrick Serruys
Patrick Serruys has been instrumental in developing several key innovations in coronary angioplasty, including drug-eluting stents and quantitative coronary angiography. Furthermore, he became interested in developing bioresorbable scaffolds when he felt guilty about implanting a metallic stent into such “delicate biological structure” as the coronary vessel.
Aside from Andreas Grüntzig, who do you think has been a coronary interventions pioneer in the past 40 years?
I think that A. Grüntzig was the only true pioneer, but there have been several key innovators. For example, we have to mention John Simpson, who introduced the long moveable guidewire. There is also Martin Kaltenbach, who was the fourth person to perform angioplasty after A. Grüntzig; in the USA, we must remember Richard Myler for his work with A. Grüntzig in helping to prove the concept of perioperative angioplasty. There have been so many people who have pushed the envelope in the field of chronic total occlusion (CTO), acute myocardial infarction and multivessel disease.
Why was the introduction of the moveable guidewire so important?
With the initial A. Grüntzig balloon, there was a short (2cm long) guidewire attached to the nose of the balloon. Through a central lumen in the shaft, we could record the gradient across the lesion. Postdilatation, when the gradient had disappeared, we could retrieve the balloon in the shaft. However if there was a dissection, there was practically no chance to recross the lesion. The moveable guidewire enabled us to do that and, therefore, it was one of the key improvements. If it were not for this innovation, balloon angioplasty may have potentially disappeared.
What have the other important innovations in equipment been?
I think the key change in equipment has been the miniaturisation; being able to go from an initial 10Fr catheter to a 4Fr or 5Fr guiding catheter has been instrumental in enabling the switch from transfemoral to transradial.
Better equipment, along with more experience, means that it is extremely rare to see a patient going from the cath to the operating room. We have gone from a failure rate of 15–20% to maybe half a per cent. The other point is that the procedure has almost become an outpatient procedure; just a few hours in the hospital and that is it.
What was your contribution in helping to develop the field of angioplasty?
In 1982, we were very proud to present the first CTO angioplasty. Looking back, it is amazing that we dared to open a CTO given the equipment at the time. I, in 1983, published a report of using angioplasty immediately after thrombolysis in a patient with acute myocardial infarction and, together with Pim de Feyter, showed the difficulties of using angioplasty in unstable angina.
Also, with Eduardo Souza, I introduced the concept of drug-eluting stents to the world. Drug-eluting stents, according to the studies we did, completely eliminated the restenosis that was seen with bare metal stents. Please don’t wake me up from the dream that I am having that it was completely eliminated in the long term!
Furthermore, I was instrumental in developing quantitative coronary angiography. When I started work at the Erasmus University Medical Center in Rotterdam, I worked with a young engineer called Hans Reiber to develop quantitative angiography. It was not a simple task but we did it because I was irritated by people talking about restenosis while using different visual criteria to identify it. Therefore, quantitative angiography introduced some objectivity in the assessment of the long-term results of angioplasty and in identifying late lumen loss; it has now been used for more than 25 years.
Why did you decide to try to develop a bioresorbable scaffold?
When I first started implanting metallic stents and saw, with the angioplasty, the reflection of the light on metal implanted in the vessel wall, I felt terribly guilty for what I had done. How could we implant a piece of metal into such a delicate biological structure? Therefore, I became obsessed with the idea of developing something that would disappear.
A coronary vessel has its own metabolism; it needs to have motion and to have some cyclic strain to stay healthy; therefore, you should not cage it with metallic stents. The story of the bioresorbable scaffold is not complete. New challenges come along and we have to find out how to address them in this present era of drug-eluting stents that—while not approaching perfection—are associated with a high degree of efficacy.
What are the next steps in the field of bioresorbable scaffolds?
In my mind, it is very simple. The polylactide material used for the scaffold does not have much strength or much radial force; therefore, we have to use bulky and thick struts to ensure that a scaffold has enough radial force to expand the vessel and counteract the natural recoil. However the beauty of this material is that the molecules can be manipulated by stretching and by warming and cooling. With this process, you can increase both the strength and the force of the scaffold. Eventually, we will have thin and strong struts that are similar to those of metallic stents. Also, we will have to change the shape of the struts to make them more circular and less quadratic, which disturbs the laminar flow in the vessel. Once we have made the struts thinner and circular, we need to determine what the optimal resorption time is.