Intricate medical devices are required for interventional procedures performed today on the coronary arteries. The most common interventions involve angioplasty with or without subsequent stents and/or surgical coronary artery bypass grafting.
Angioplasty and Stents
Percutaneous transluminal coronary angioplasty is a procedure during which a balloon catheter is introduced into the narrowed portion of the coronary artery lumen and inflated to reopen the artery to allow the return of normal blood flow: some of the newer stents may also be used for the target delivery of drugs. Currently during such procedures, often a coronary stent is also placed such that restenosis of the artery is significantly delayed. A stent is a medical device made up of wire mesh that provides scaffolding to support the wall of the artery and keep its lumen open and free from the buildup of plaque. Balloon angioplasty and coronary stents have prevented numerous patients from having to undergo coronary artery bypass graft surgery, which can be more costly and painful. Additionally, such stents have been produced with a variety of drug coatings in further attempts to minimize or eliminate the possibility of restenosis: i.e., drug eluting stents [1].
Movie showing a stent being placed in an isolated heart. The movie shows a catheter cannulating the left anterior descending artery, then switches to an
arterial view of the catheter with the corresponding fluoroscopic view of the heart. A balloon inflates the stent to its desired position.
Aides in Stent Delivery
While these drug eluting stents have been considered as a great advancement over the clinical use of angioplasty [2], it is generally considered that success rates could be even further improved via applying additional new techniques. For example, the STAR - Subintimal Tracking and Reentry - technique utilizes a small wire to dissect into the obstruction [3]. Further, it has been proposed that radiofrequency signals can warn the user when the wire tip is too close to the vessel wall to prevent perforation and can be pulsed to facilitate passage through a coronary artery obstruction [4]. Another approach employs pulses that face of the obstruction so to create a path into the obstruction [4]. Finally, proteolytic enzymes can be applied so to digest parts of the obstruction and thus aid in the eventual mechanical passage of a guidewire [4].
Bifurcation Stents
In some patients, there is significant narrowing of the arteries at locations where the artery branches or bifurcates. There are several different techniques that have been developed for stenting these locations. If the side branch is small (< 2.25mm diameter), only the main branch is typically stented. If the side branch is larger, there is an option to deploy a second stent. There are several different techniques to deploying two stents for bifurcated arteries as demonstrated in the figure [5,6]
Coronary bifurcation stenting techniques. A) V stenting technique: a stent is deployed in each of the branching arteries. B) The Y stenting technique: a stent is deployed in each of the branching arteries. Next, a stent crimped over two balloons is deployed proximally in the parent branch. The balloons are inflated to deploy the proximal stent. The distal end of each balloon is positioned in each stented daughter branch during inflation. C) The simultaneous kissing balloon technique: two stents are deployed by inflating both balloons simultaneously at the same pressure. D) The T stenting technique: the main branch is stented first. Next, angioplasty is performed on the side branch to create an opening in the first stent and a second stent is placed in the side branch. E) The culottes technique: similar to the T stenting technique, except that the proximal end of the second stent is positioned in the main branch. F) The crush technique: the first stent is deployed in the side branch. The main branch is then stented, which "crushes" the proximal end of the first stent against the wall of the main branch.
Coronary Bypass Surgery
Coronary Bypass is a surgical method used to treat coronary artery disease. When a coronary artery is narrowed or obstructed, a vessel (typically from elsewhere in the patients) can be used to bypass the narrowed artery. One end of the vessel is typically attached to the aortic root or left subclavian artery. The other end is attached distal to the narrowed portion of the artery so that oxygenated blood can reach that given part of the myocardium, hence the occluded coronary region is bypassed.
References
Anderson S, Lahm R, Iaizzo, P (2009) The Coronary Vascular System and Associated Medical Devices. Handbook of Cardiac Anatomy, Physiology , and Devices. Springer, New York: 109-123
Prasad A, Rihal CS, Lennon RJ, Wiste HJ, Singh M, Holmes DR, Jr. Trends in outcomes after percutaneous coronary intervention for chronic total occlusions: a 25-year experience from the Mayo Clinic. J Am Coll Cardiol 2007;49:1611-1618
Colombo A, Mikhail GW, Michev I, et al. Treating chronic total occlusions using subintimal tracking and reentry: the STAR technique. Catheter Cardiovasc Interv 2005;64:407-11; discussion 412
Weisz G, Moses JW. New percutaneous approaches for chronic total occlusion of coronary arteries. Expert Rev Cardiovasc Ther 2007;5:231-41
Baber U, Kini AS, Sharma SK. Stenting of complex lesions: an overview. Nature Reviews Cardiology 2010:7:236-245
Iakovou I, Ge L, Colombo A (2005) Contemporary Stent Treatment of Coronary Bifurcations JACC 46:1446-1455
