Developments in percutaneous coronary stentin

Developments
in percutaneous coronary stentin
Adel Imam M.B.BCH.,D.CV.D.M.M.D.F.A.C.C
prof. of cardiology national heart institute imbaba
Coronary artery disease (CAD) is the leading cause of cardiovascular mortality worldwide, with >4.5 million deaths occuring in the developing world. Despite a recent decline in developed countries, both CAD mortality and the prevalence of CAD risk factors continue to rise rapidly in developing countries. i
Werner Forssmann usually is credited with being the first person to pass a catheter into the heart of a living person - himself. At age 25 while receiving clinical instruction in surgery at Eberswalde (1929), near Berlin he passed a catheter 65 cm through one of his left antecubital veins, guiding it by fluoroscopy until it entered his right atrium. ii
Better radiographic imaging techniques and less toxic radiographic contrast agents have been developed progressively, as the number of diagnostic catheterizations has exceeded 2,000,000 per year.
In 1977 the technique of balloon angioplasty had been introduced, generally known as percutaneous transluminal coronary angioplasty (PTCA). iii
Angiograms of the first patient to undergo successful angioplasty. Top, The diagnostic angiogram (September 14, 1977) and appearance at the time of angioplasty (September 16, 1977). Bottom, The 1- month restud
(October 20, 1977) and the 10-year repeat study (September 16, 1987)). iv
Encouraged by the success of PTCA but challenged by its shortcomings. physician and engineer inventors have developed and introduced into clinical practice a lot of new percutaneous interventional devices over the past decade.
This includes various forms of catheter-based atherectomy, bare metallic stents, and drug-eluting stents, which together have largely solved earlier problems relating to elastic recoil, dissection, and restenosis of the treated segment.
These techniques are usually subsumed (along with conventional balloon angioplasty) under the broader designation of
percutaneous coronary intervention (PCI).
In the early 1990’s bare metal stents were developed. This was pioneered by Julio Palmaz, a physician-inventor.v
Stents are differing with respect to composition (eg, stainless steel, cobalt chromium, or nickel chromium), architectural design, and delivery system.
The bare metal stent was a huge leap forward in treating the problem of restenosis. Like angioplasty, the stent is inserted percutaneously through the femoral artery and then is expanded in the coronary vessel. Having the stent in place, holding open the artery, decreased the restenosis rate to roughly 20-25% instead 0f 40%. vi
Percutaneous coronary intervention (PCI) has seen a tremendous increase and tends to be the most frequently used method for myocardial revascularizatioh.
An impressive array of stent improvements, newer drug regimens and technological advances have emerged and broadened the therapeutic spectrum for interventional cardiologists worldwide.
More recently, drug-eluting stents, which slowly release anti-clotting drugs in addition to physically propping open the artery, have been shown to be effective and
efficient in the treatment of coronary artery disease.
The use of metal drug-eluting stents presents some potential drawbacks. These include a predisposition to late stent thrombosis, prevention of late vessel adaptive or expansive remodeling, hindrance of surgical revascularization, and impairment of imaging with multislice CT.
To overcome some of these potential drawbacks, several companies are pursuing the development of bioresorbable or bioabsorbable stents. Like metal stents, placement of a bioresorbable stent will restore blood flow and support the vessel through the healing process. However, in the case of a bioresorbable stent, the stent will gradually resorb and be benignly cleared from the body, leaving no permanent implant.
Studies have shown that the most critical period of vessel healing is largely complete by approximately three months. Therefore. the goal of a bioresorbable or “temporary” stent is to fully support the vessel during this critical period, and then resorb from the body when it is no longer needed.vii
Local application of antiproliferative substances with drug-eluting balloons (DEB) is an emerging approach for the treatment of coronary disease especially instent restenosis Without the shortfalls of implanting an additional metal scaffold.
These devices are increasingly being used by clinicians based on a number of
encouraging studies.
i) Okrainec K, Banerjee DK, Eisenberg MJ. Coronary artery disease in the developing
countries. '
AHJ,2004;148:7-15
ii) Bourassa MG. The history of cardiac catheterization Can J Cardiol. 2005 Oct;21(12);10l1-4. ‘
iii) grantzig A, Senning A, Siegenthaler WE. Nonoperativ dilatation of coronary artery stenoses. Percutaneous transluminal coronary angioplasty. N Engl J Med 1979;301:61.
iv) Angioplasty from Bench to Bedside to Bench Spencer B King. Circulation 1996; 93 : 1621-29.
v) The Story of the Stent: An Interview with Julio Palmaz“, In Vivo Magazine, March 2003, page 67.
vi) Zimmer, S., “MedTech 101: The Medical Device Handbook”, Deutsch Bank Securities, lnc., September 2002.
vii) Serruys, PW; Luijten HE, Beatt Kj, et al. (February 1988). “Incidence of restenosis after successful coronary angioplasty: a time-related phenomenon. A quantitative angiographic study in 342 consecutive patients at 1, 2, 3, and 4 months". Circulation 77(2): 361-71. doi:10.1161/01.ClR.77.2.36l. PMID 2962786.