The story of the stent starts with a discarded piece of metal plucked from the floor of Julio Palmaz's garage in the late 1970s; that errant piece of metal was the wellspring of one of the most successful -- and debated -- devices in the therapeutic armamentarium for managing cardiovascular disease.
Julio Palmaz, MD, creator of the first commercially available stent, attended the recent 29th Annual Meeting of the Society of Interventional Radiology (SIR) in Phoenix, Arizona, where he was sat down with Medscape's Pippa Wysong to reflect upon the impact of his work on the specialty of endovascular interventions.
Dr. Palmaz is Stewart R. Reuter Professor and Chief of Cardiovascular and Interventional Radiology at the University of Texas Health Science Center in San Antonio, Texas.
(The first stent to be approved by the US Food and Drug Administration [FDA] was on display at the Smithsonian Institute in 2003 as part of Hispanic Heritage Month.)
This is the first part of a 2-part interview.
Medscape: Could you tell me the story of when you first came up with the idea for a stent?
Dr. Palmaz: The story of the stent is actually a story of serendipity and it goes back to my early days in medicine. I started off training in diagnostic angiography in Argentina, then moved to the States so I could do a residency in diagnostic radiology at UC Davis. Dr. Reuter was co-chair of the department then. Around that time I went to my first SIR meeting, in New Orleans, where I heard Andreas Gruentzig the inventor of balloon angioplasty, speak. It was February 1978, and he described this amazing new technique of balloon angioplasty. It was exciting -- a way to open vessels through a catheter. He could have dazzled us with the novelty of the technique, but instead he actually dwelled on the limitations, showing us x-rays and microscopic images showing how vessels could still occlude.
Medscape: And this got you thinking of a solution?
Dr. Palmaz: I think it was his explanation that elicited in my mind the idea of why not put a scaffold in the vessel. I left the conference in a cab I shared with Dr. Reuter, and I mentioned my idea. He said it sounded like a nifty idea, and that I should write it up -- start learning how to write a paper.
Medscape: So you wrote it up back in 1978?
Dr. Palmaz: I wrote a sort of a report on the idea and that helped to expand the idea in my mind. How could you put a scaffold on a balloon, drive it through, and expand it in the artery at the same time with a balloon? I made drawings, too, which was good because it left a written document of the concept.
Medscape: What happened next?
Dr. Palmaz: I sent the report in, and Dr. Reuter and other faculty members looked at it and encouraged me to continue. I read about implantable metals and delved more into the subject. I played at home with wires and pliers and solder material, making prototypes in the garage.
Medscape: What sort of prototypes?
Dr. Palmaz: We started buying balloons and doing angioplasty, but I was washing the balloons afterwards and taking them home. I was making my own nets there, playing with them, expanding them inside rubber tubes. I started having a feel for the mechanical problems that making a stent would impose.
Medscape: Sounds like quite a process.
Dr. Palmaz: I started by trying to weave cylindrical nets using pencils and pins, weaving copper wiring in and out. Then I realized that the net didn't have plasticity; the cross-points of the weave needed to be fixed. So I tried welding those spots, using just an iron solder, around the circumference. I was also reading about implants and got the notion that implants needed to be made of one material, otherwise there would be electromechanical corrosions. The stumbling block was how to make the device in one piece if the cross-points needed to be welded.
Medscape: What did you do?
Dr. Palmaz: It was total serendipity. I found a piece of metal lathe on my garage floor -- the kind that masons use to put plaster on. This material is made in a pattern that has staggered openings. I looked at it and thought, "This looks like what I'm trying to do here." I grabbed it, cut out a small piece, then closed it by pushing it together and bouncing it on the table with a hammer. I realized that the staggered openings were staggered slots when it was closed. I thought, "Well, if I make this pattern in a tube, then, when a balloon expands, it will become a mesh." And it's made of a single material. This was the inspiration for the slotted stent.
Medscape: But you were still in the early stages?
Dr. Palmaz: I started making large cardboard models. I could put my hands inside the cardboard tubes and expand then -- see how much the thing would shorten and how much the configuration of the slots would change into diamond-shaped spaces. I learned a lot doing this. After playing with these things for years in my garage, I realized that more sophisticated techniques were needed. It was time to go to a company and get them interested.
Medscape: How did that work out?
Dr. Palmaz: I went to a couple of companies, but they turned me down. The third company directed me to a retired biotechnologist they said could help me out. I went to see him and he gave me all sorts of ideas on how to make the stent, including asking a shop to make a better prototype than something out of cardboard. I got a renewed enthusiasm.
Medscape: What happened next?
Dr. Palmaz: Dr. Reuter had moved to San Antonio, Texas, as chief of vascular procedures and invited me to take a position there. I did. I got guaranteed research time and space and technical aid for building my prototypes. In 1983 we started working really hard and intensely on the stent. We spent a couple of years doing bench work and animal testing. Slowly we transitioned into the clinical phase using this in patients. We even got $250,000 of funding from the founder of the Fuddruckers hamburger chain, Philip Romano. Richard Schatz introduced us, and Dr. Schatz was eventually my collaborator in the stent. The stent for the coronaries was eventually called the Palmaz-Schatz stent.
Medscape: When did a company get involved?
Dr. Palmaz: When we got the money we completed the basic research and had working prototypes. The project was then licensed to Johnson & Johnson who designed the clinical trials. In October 1987 I put the first peripheral stent placement in a patient at Freiburg University in West Germany. Later that same year we did the first coronary, in Sao Paolo, Brazil. Both procedures were very successful.
Medscape: Almost 10 years from idea to the first patient. So, I suppose it was all downhill from there...
Dr. Palmaz: We did some other feasibility cases in Europe, both in coronaries and in the periphery, then a multicentered trial got approved by the FDA. Those were the years of the trials; I was on the road a lot. Richard Schatz was doing the same thing on the coronary side of things.
Medscape: When was the stent finally approved?
Dr. Palmaz: In 1991, the FDA approved -- for the first time ever -- a stent for the treatment of atherosclerotic obstructive disease. The peripheral stent got approved and started being used by the interventional radiology community everywhere in the world. But the coronary trials were still ongoing. Coronary stents didn't get approved until 1994 after the BENESTENT and STRESS trials. The FDA wanted to see a randomization between stents and balloon angioplasty.
Medscape: Sounds like things moved pretty quickly.
Dr. Palmaz: Yes, and there was a big chore for Johnson & Johnson. They had to scale up to the rapidly increasing use of stents, plus there was the enormous task of training everybody to use them. Then it hit us that the stent was going to have a far bigger role than we had anticipated. We thought that maybe 20% of all patients would receive stents, but then it was 30%, then 40%. Next we knew it was 75% to 80%. It became really crazy.
Medscape: And they were the only supplier back then?
Dr. Palmaz: In 1994-1995 Johnson & Johnson was the only supplier. By mid-1996, three competitors came on the scene: Boston Scientific, Medtronic, and Guidant. These companies featured balloon expandable stents, but they had new features that the cardiologists liked. The share of Johnson & Johnson dropped from 95% to 5% of the market. Their business collapsed from being the ones who developed the market to almost zero market share at the time.
Medscape: But you held the patent, correct?
Dr. Palmaz: That's right. And then Johnson & Johnson started a systematic approach to try to defend the patents in courts. In Europe we lost our patent protection. Then there was a big trial in the US, which started slowly in 1998 or 1999. It was in 2001-2002 that we got to the courts in Delaware arguing over the patent. In those years there were a lot of legal efforts over this.
Medscape: What happened? What was the outcome?
Dr. Palmaz: I think the initial lawsuits favored Johnson & Johnson, and there was an arbitration with Medtronic. Eventually Johnson & Johnson started to recoup some of the revenues lost as a result of competition. This is an ongoing issue and they are still fighting things out. However, I think things are finally settling down.
Coming soon...Part II of Medscape's interview with Dr. Julio Palmaz.
Medscape Radiology. 2004;5(1) © 2004 Medscape
Cite this: An Expert Interview With Dr. Julio Palmaz: Part I -- Serendipity and the Stent - Medscape - May 07, 2004.