Recent Advances in Percutaneous Coronary Intervention
Percutaneous Coronary Intervention (PCI) is also known as balloon angioplasty is a minimally-invasive procedure that is recommended in patients diagnosed with coronary artery disease or patients who have suffered a heart attack.
The procedure involves the compression of cholesterol deposits within the coronary arteries in order to increase the size of the blocked arteries and improve blood flow to the heart. One of the most common complications of PCI is blood clotting, which occurs in spite of the use of blood thinners.
Most PCI procedures are successful, but about 1-2% of procedures may require emergency coronary artery bypass graft surgery. In patients undergoing PCI, the risk of heart attack is 1-2%. Based on the clinical update recently published in the Journal of the American Medical Association, research, and technological advances have greatly improved the use of PCI.
Coronary artery balloon angioplasty was first introduced in the 1970s as an alternative to coronary artery bypass surgery. Over the years, the PCI procedure has been made more safe and effective. Technologic advances including different types of stents have reduced the risk of complications and the need for repeated procedures. The introduction of bare metal stents (BMS) in the 1990s reduced the rate of acute vessel closure and revolutionized PCI, but also led to two major complications such as stent thrombosis and in-stent restenosis. Studies involving the first generation BMS reported restenosis rates of about 22-32%. The development of stent scaffold designs, local delivery of antiproliferative agents (sirolimus), and the use of dual antiplatelet therapy have helped reduce the rates of stent thrombosis and restenosis. However, a recent large scale randomized trial, which compared clinical outcomes of two contemporary drug-eluting stents (DES) after 2 years revealed that about 1-2% patients had a stent thrombosis and 5% of patients needed repeat revascularization. Apparently, these complications are driving factors for advances in coronary stent design and technology.
Recent Developments in Coronary Stent Technology
- Bioabsorbable stent scaffolds: The first bioabsorbable stent that was commercially available was the bioabsorbable vascular solutions (BVS) everolimus-eluting stent from Abbott Vascular. It is made up of a bioabsorbable polymer backbone of poly-L-lactic acid (PLLA) and a polymer coating of poly-D, L-lactide that contains everolimus, an antiproliferative drug. This stent has yielded clinical and imaging outcomes similar to that of the conventional DES.
The only bioresorbable metallic stent to undergo clinical evaluation in humans is the DREAMS bioresorbable stent from Biotronik. It is coated with a bioabsorbable polymer and the antiproliferative drug, paclitaxel. This stent possesses mechanical properties comparable to that of conventional metallic stents. Recent trials with DREAMS stent showed low rates of target lesion failure at the end of 6 and 12 months.
Another fully absorbable sirolimus-eluting stent that can release salicylic acid is called the IDEAL BDS stent from Bioabsorbable Therapeutics. It is comprised of a polyanhydride ester and salicylic acid and possesses both anti-inflammatory and antiproliferative properties.
- Self-expanding stent scaffolds: The Cardiomind Sparrow from Biosensors International is a self-expanding nitinol stent and was developed for the treatment of small vessels. It is delivered using a 0.014-inch guide wire based platform instead of the traditional balloon expandable technique. It has been developed in both the variants -bare metal stent and drug-eluting scaffold that is coated with a biodegradable polymer, polylactic acid that can release the antiproliferative agent, sirolimus.
- Micromesh covered stent: The MGuard stent from InspireMD is a novel bare metal stent covered with a polyethylene terephthalate micronet mesh designed to trap the thrombus and limit distal embolization. This was developed primarily for patients with myocardial infarction having an acute ST elevation.
Drug Eluting Balloons - An Alternative to Stents
In order to rectify in-stent restenosis, drug-eluting balloons have been introduced to perform balloon angioplasty. Drug-eluting balloons are suitable for the treatment of small diameter coronary vessels and can allow local application of an antiproliferative agent, especially at the time of barotrauma. This avoids the use of a persistent metal scaffold, which can act as a nidus for inflammation and subsequent restenosis. Paclitaxel is the most commonly applied drug applied to drug-eluting balloons.
A recent meta-analysis that included five studies revealed that balloon angioplasty procedure using a drug-eluting balloon was as effective as Paclitaxel-eluting DES and much superior compared to the conventional balloon angioplasty.
Advantages of Drug-Eluting Balloons
The advantages of drug-eluting balloons over DES include:
- Lower risk of stent thrombosis
- Shorter duration of dual antiplatelet therapy is sufficient
Undoubtedly, there has been enormous development in the field of percutaneous coronary intervention over recent years.