The Classification, Comparison and Behavior of Coronary Stents: A Focused Review on Materials and Clinical Studies & Complications

Abstract

In the past two decades, cardiovascular disease has become one of the leading causes of death in the world. For treatment of these diseases, according to the patient’s conditions, methods such as drug therapy, balloon angioplasty, stent implantation, and bypass surgery are used. Stent implantation can be considered the most common way to treat these diseases. In this article, considering the special importance of stents, we examine them. We classify the stents based on their design and point out the effect of the design on some of the properties of the stents. Also, we introduce the different generations of stents and compare them. Finally, we will examine some of the features of the artery wall and the behavior of the stent in the arteries. And we talk about the bad effects the stents can have on the body.

Introduction

The main task of the circulatory system is to provide the materials needed by all the biological cells of the body and to dispose of waste from cellular metabolism. Circulatory system consists of the heart and blood vessels. The heart is a muscular pump that pumps blood into the body. Blood vessels are a network of tubes that carry blood throughout the body and provide oxygen, nutrients, water and hormones, therefore; the presence of any disorder in blood supply can cause serious problems.

In recent decades, due to the progress of the industry, the life style of many people around the world has changed, which hazarded the health of people and made cardiovascular disease the world’s leading cause of mortality. Cardiovascular diseases effect on function and structure of the heart and blood vessels. Coronary artery disease is one of the most common cardiovascular diseases, that it affects more than five million Americans each year.

The heart muscle requires a constant supply of oxygen and nutrients for the proper and healthy functioning of the heart; this is the responsibility of coronary arteries. In normal state, the arteries have a smooth, elastic inlay that allows blood to flow freely. Blood consists of fatty substances that are stick to the internal walls of the arteries. The onset of this disease is a gradual process that can begin before a person’s adolescence and at older ages can cause the formation of fat masses on the walls of the arteries and, consequently, damage to the walls of the blood vessels. Cells release a kind of white blood cells for repair, but the process itself over time makes the walls of the vessels more sticky; therefore, other substance such as proteins, calcium and inflammatory cells-that are suspended in bloodstream- stick to the walls of the vessels and combine with the fat, the product substance, called plaque. Over time, plaque continues to build upon the walls of the arteries. As the plaque expands, the arteries become narrow and hard. This process is called Atherosclerosis. This process is commonly known as hardening of the vein, because the builds up of plaque, makes the walls of the artery thicker and restricts blood flow through the area that is supplied by the artery, so; the heart can’t receive blood, oxygen and nutrients it needs.

There are various therapeutic options for treating coronary artery disease. The doctor’s recommended treatment depends on the symptoms of patient and degree of damage to his heart. Treatment options can include:

• Drugs

Blood diluents such as Aspirin, Beta blockers and etc. can prevent arterial occlusion.

• Balloon angioplasty

Coronary balloon angioplasty is a process used to open blocked heart arteries. This method, involve the temporary placement of a small balloon in the artery obstructing area and inflate it to help expand the arteries.

• Coronary stent implantation

About one third of patients who have been using balloon angioplasty to open their vascular obstruction have been restenosis within six months, therefore; in most people undergoing angioplasty, during a process similarly, a tool called a Stent is also placed in the blocked artery. The stent is usually inserted into the artery after expansion of the artery by inflating the balloon. A stent is a latticed, metal scaffold that keeps the artery open and stays there permanently. Stent also reduces the odds of heart attack.

• Bypass surgery

Another treatment for the narrowing of the arteries is Bypass surgery; this involves the graft of a blood vessel from the chest, leg, or forearm to the coronary artery to redirect the blood around the blockage area. As result of this surgery, blood will reach the heart.