Radiologists and Their Stents of Choice:

Why are bare metal stents still used?

Will Hargis

East Tennessee State University

Abstract

This study is to being designed to obtain information about why physicians continue to incorporate the use of bare metal stents in heart catheterization procedures.  Any information collected from this study will show any results that would promote the continued use of bare metal stents instead of drug-eluting stents.  The data will be gathered via two surveys that will be completed before the heart catheterization and then after the allotted time period post treatment.  Three hospitals in the East Tennessee will take place in the study, and their input will yield the results for the study.  Percentages of each type of stent per hospital will be recorded and an answer will be determined to why physicians continue to use bare metal stents when the option is available for drug-eluting stents.  

Chapter 1 Introduction

Background

            Radiology has made several advancements recently, specifically advances related to the care for cardiovascular ailments.  Blockages in heart arteries have become a common problem and hundreds seek medical treatment daily.  These blockages can come from a variety of things including genetics and lifestyle behaviors.  Treatments for these coronary symptoms include: medication, surgery, or a catheter based treatment involving metal stents (Maisel & Laskey, 2007).  The treatment used for opening blocked arteries with angioplasty and stenting is as recent as the 1960-70s, with the first stent used in a heart as recently as the 1980s. The addition of stents to regular angioplasty greatly improved the continued dilation of blocked arteries, and the procedure has been advanced and perfected of the course of nearly thirty years. Heart catheterization and stent placement is more immediately effective than medication for severe blockages, and less invasive than a coronary bypass surgery.  People that receive heart catheters are often awake during the procedure, and feel only slight pain and discomfort as the balloon is inflated.  After a visit to the heart catheterization lab, patients often show instant signs of improved blood flow (Elhendy & Hamby, 2007).

            Angioplasty involves placing a catheter into the blocked artery and inflating it.  A stent is then left in place to act as a new support system for the artery.  It is comparable the framework of a house because it sets a structure for the artery to follow. There is a one in five chance that the artery will re-narrow, a term called restenosis (Maisel & Laskey, 2007).  Restenosis is caused by tissue growth around the stent.  Until recently, bare-metal stents have been the only option, but now physicians have the choice to use drug-eluting stents.  These new stents release a drug that inhibits restenosis by preventing tissue growth.

            Patients that have stents placed in their arteries are often prescribed anti-clotting medication.  Things that improve blood flow are critical after stent placement.  Stents introduce a new metal into your blood stream, and the risk of thrombosis is higher than previously without a stent (Maisel & Laskey, 2007). 

Purpose

            The purpose of this study is to gain some understanding as to why radiologists continue to promote use of bare metal stents when they have the option to use the newer drug-eluting stents.  Once enough information and data is collected on the types stents, an obvious better choice of a stent should be revealed.  Also, a better understand of why radiologists refuse to move towards using drug-eluting stents. 

Significance

             The choice between stents is made by radiologists and hospitals across the world.  If the newer drug-eluting stents offer more benefits, and are available for use, then radiologists should not be hesitant to make the transition.  The main summary of the Hippocratic Oath is to not cause harm to patients, so every step should be made in order to provide the most effective and long lasting care.  If a valid reason to stay with bare metal stents is available, then it should be made public to other physicians.    

Research Questions

            A single research question guided this study: Why do radiologists continue to use bare metal stents when they have the option of drug-eluting stent?  Other questions will be answered to support the main question.  These questions include:

·         What percentages of stents are used at each hospital?

·         Does either stent produce immediate adverse effects?

Assumptions

            The data found in this study is recorded assuming that the radiologic technologists and radiologists have properly placed the stent, and there has been no malpractice at all.  The study assumes that responses to follow up surveys are truthful, and completed within the allotted timeframe.

Limitations

The study follows these limitations:

1.      Radiologists have preferences with regards to stenting.

2.      This study is limited to patients presenting for cardiac caths during the months of Jaunary-May in 2010.

3.      This study is limited to patients from the following hospitals: Blount Memorial Hospital, Johnson City Medical Center, and Unicoi County Memorial Hospital

Radiologists and Their Stents of Choice:

Are drug eluting stents superior?

Chapter II Literature Review

            Stenting has become a second nature procedure that more than 2 million people worldwide have done (Rihal, 2008).  Balloon angioplasty involves the use of a catheter that is inserted into the heart, usually via the femoral artery.  The catheter is then inflated and a stent is embedded into the artery wall to maintain its dilation.  Patients are usually discharged within 24 hours of a procedure, and often show instant signs of improved blood flow (Elhendy & Hamby, 2007). 

            Several studies have been conducted talking about the severity of restenosis.  Restenosis is the re-closing of a once opened artery, and is the main factor in stent effectiveness.  After percutaneous coronary intervention (PCI), restenosis has often shown itself in the form of exertional angia (Chen et al., 2006).  Angia is chest pain or occurs when part of the heart muscle doesn't get enough oxygen-rich blood, and often creates a great deal of problems for the patient.  PCI cases were recorded from May of 1999 to September 2003 and divided into these three categories:

·         Myocardial infarction

·         Unstable angia requiring hospitalization before angiography

·         Exertional angia

Of the 984 patients, 1186 bare-metal stents had been used.  More than one third of bare-metal in-stent restenosis turned into heart attacks or unstable angia, and aggressive efforts such as drug-eluting stents were recommended (Chen et al., 2006)

Drug-eluting stents have been tested to see if they are more capable of maintaining an open artery as opposed to regular balloon angioplasty.  One test sought to find the effectiveness of sirolimus-eluting stents in patients that had re-closing arteries.  In this test, 150 patients that had already taken part in balloon angioplasty, upon return visit, were given stents coated in sirolimus or retreated with balloon angioplasty (Alfonso et al., 2006).  Of the two groups, sirlolimus was shown to slow the restenosis of arteries and provided a superior long-term outcome than balloon angioplasty. 

Studies have been done to compare the different types of drug-eluting stents to determine the adverse and beneficial effects of each.  Sirolimus-eluting and paclitaxel-eluting stents were compared to find what exactly, if any, the differences are between the two.  They are both polymer-encapsulated to ensure slow a release of their drugs.  Sirolimus-eluting stents have been shown to reduce the rate of angiographic and clinical restenosis in previous trials, and paclitaxel-eluting stents also slowed restenois rates and lowered the needs for additional future treatments (Windecker et al., 2005).  According to Windecker, et. al “sirolimus-eluting and paclitaxel-eluting stents, as compared with bare-metal stents, reduce the risk of restenosis” (Windecker et al., 2005).  This study was conducted to directly compare the types of drug-eluting stents to see which one would prove more effective in restenosis.  1012 patients, with a total of 1401 lesions, took part in this study with 503 of them given the sirolimus stent, and the other 509 got the paclitaxel stents.  People with acute coronary syndrome or stable angina were eligible to participate if they had at least one site of restenosis of 50 percent of vessel diameter. 98.4 percent of lesions were located in the native coronary artery. Both types of drug-eluting stents had the same range of diameters, from 8 to 33 millimeters, to suite the various locations of blockages and lesions to be treated.  Any adverse events were assessed at one, six, and nine-month intervals to be recorded fairly (Windecker et al., 2005).  The results of the study showed that the two types of drugs yielded similar characteristics in early data collections; however, there was one number that stood out above the rest when the final numbers had been achieved: the number of deaths due to cardiac causes.  With sirolimus-eluting stents there were no patients to die, but paclitaxel stents had four patients die within the time frame of the study (Windecker et al., 2005).  Sirolimus was also shown to have greater outcomes including:

·         Fewer major adverse cardiac advents

·         Less target revascularization of both lesions and vessels

·         Less target vessel failures

The safety of drug-eluting stents has received a great deal of publicity over the past few years, mainly concerning the number of blood clots that have been recorded to develop within stents after their placement, but the U.S. Food and Drug administration stands behind the use of stents as an appropriate means of treatment for coronary blockages (Maisel & Laskey, 2007).  Some hospitals have discontinued use of drug-eluting stents and only use bare-metal stents for their procedures.  A magazine called Radiology Today published an article that claimed the mortality rate for drug-eluting stents is not significantly higher than bare-metal stents.  The risk of repeat revascularization had dropped 18 percent from the bare-metal stent era to the drug-eluting stent era (Dartmouth, 2008).

The FDA claims that when stents are used on-label they are completely effective, but roughly 60 percent of the time stents are used for “off-label” problems such as cases that involve multiple blockages or other complications (Rihal 2008).  In these cases that involve more complex circumstances, the FDA admitted there is a small risk to develop a blood clot that can lead to a myocardial infarction or death.  Stents introduce a foreign material into the blood stream, and naturally increase the likelihood of clotting (Maisel & Laskey, 2007).  After a patient has been given a stent, the physicians will usually prescribe them medications to prevent clotting such as clopidogrel, that will usually be taken up to a year after the stent is placed (Rihal, 2008).  There are basically four options to choose from when faced with coronary blockages:

·         Bare-metal stents

·         Drug-eluting stents

·         Coronary bypass surgery

·         Lifestyle changes and medications

Each of the options has both good and bad outcomes that are possible, so the patient should be informed to the different paths available (Rihal, 2008).  Coronary bypass surgery is a highly invasive surgery, and should only be used when it is absolutely necessary. 

Chapter III Research Method

Research Design

            This study is designed to determine why radiologists choose to use bare-metal stents instead of drug-eluting stents when the choice is available.  To find the answer, a series of tests will be conducted to observe the medical effects of each type of stent in their appropriate patients.  The data will be collected and recorded to determine if drug-eluting stents are a hazard to patients’ standards of living, or if the physicians that choose to continue using bare-metal stents do so for a non-medical reason.  Surveys will be given to the physicians on duty for the procedures, and a follow-up survey will be conducted nine months after treatment.  The surveys will be taken by physicians, so validity and honesty will be expected in their answers.  Data will be collected from the heart catheter lab or special procedures area of two separate hospitals and the time frame will include any applicable shift the physicians may be working.  Radiologic technologists will be allowed to perform the balloon angioplasties and stent placements, but only under the direct supervision of the radiologist. In order to reach a proper number of procedures to record, the project will last several weeks to get the initial data and then an additional nine months to record the follow up visit. The data will show if there is a valid reason to continue use of bare-metal stents when drug-eluting stents are available.

Research Questions

            The two surveys are designed to reveal vital information about the different types of stents from the radiologists that have observed/performed the stent placement.  Questions that will be answered by these surveys include:

·         Where has the stent been placed?

·         What is the vessel diameter before/after the procedure?

·         Does the patient have any pre-existing risk factors that may sway results?

On the follow up visit, a different set of questions will need to be answered.  They include:

·         How much in-stent restenosis has occurred since the previous visit?

·         Any adverse effects directly related to stent placement?

·         Will another balloon angioplasty be needed now or in the near future?

·         Has the patient’s quality of life improved or declined since the procedure?

Participants

            The participants of this study will be a percentage of the population that visits the hospital for balloon angioplasty and stent placement for any blockages in their hearts.  A total of 80 different patients will be selected and assigned to different groups to receive the different types of stents.  The participants will come from three hospitals in the East Tennessee area.  Background information will be gathered to maintain fairness in the results that follow the study.  The age range will vary due to the necessity of stent work on different parts of the population.  Physician and technologist skill levels will be taken into account, and only stents that have been properly placed will be recorded in the study.

Data Collection Methods

            Surveys will be used to obtain patient and physician information for the study.  The two surveys will be completed by the on call physician to record patient statistics.  The first questionnaire will be filled out immediately following a successful angioplasty and stent placement, and will record all levels of heart health.  Nine months after the procedure, the physicians will fill out the second survey to check to see which had the most favorable results.  All aspects of patient health will be questioned, and the results will show if a valid reason exists for physicians to continue the use of bare metal stents over drug-eluting stents.   The surveys are as follows:    

Survey #1 Initial examination

Name of Physician:______________________________

Date of Procedure:_______________________________

1.      Patient Sex:

            Male    □        Female    □

2.      Patient Age:

            Under 18      18-25     26-35     36-45     46-55   56-65   70+

3.      Does the patient have pre-existing risk factors?   Yes____  No_____

            If yes then which? (check all that apply)

Diabetes □  hypertension □ frequent smoker □ hyperlipidemia □ other  □ please list:____

4.      Type of stent used for treatment: bare-metal □ drug-eluting □

5.      Where was/were the stent/s placed? Check all that apply.

L anterior descending□  L circumflex □  R coronary □  saphenous vein graft  □  other □ list_______  

6.      Blood vessel diameter before procedure:_______

7.      Blood vessel diameter following procedure:_______

8.      Is the patient currently taking or being prescribed medications other than blood thinners? Yes_____ No____

a.       If yes, then please list___________

Survey #2 Nine month follow-up examination

Name of Physician:______________________________

Date of Initial Procedure:_________________________

Current Date:__________________________________

1.      Type of stent used in initial treatment: bare-metal □ drug-eluting □

2.      Has patient died since the first treatment? Yes_____ No_____

If yes, was it due to cardiac causes? Yes_____ No_____

3.      Has the patient suffered a myocardial infarction since stenting? Yes_____ No_____

4.      Blood vesssl diameter after initial stenting:_____

5.      Current blood vessel diameter post-stenting:_____

6.      Will a follow-up procedure be necessary now or in the near future? Yes_____ No_____

If yes, then what type?

more BA w/ stenting □   bypass surgery □  drastic lifestyle changes □ 

Data Analysis

Once the surveys have been collected and recorded, the information provided will allow the determination of the following:

·         Benefits of each type of stent

·         Adverse effects of each type of stent

·         The age range most commonly seeking stent related treatments

·         The percentage of in-stent restenosis in the different treatment options

·         A reason physicians and hospitals continue to practice with bare-metal stents

This data will prove if physicians have a valid reason to still use bare-metal stints or simply a bias against the newer ones.

References

Alfonso, F., Perez-Vizcayno, M., Hernandez, R., Bethencourt, A., Martí, V., Mínguez, J., et al. (2006). A randomized comparision of sirolimus-eluting stent with balloon angioplasty in patients with in-stent restenosis. Jounral of the American College of Cardiology, 47(11) 2153-2160.

Chen, M. S., John, J.M., Chew, D. P., Lee, D.S., Ellis, S.G., Bhatt, D.L. (2006).  Bare Metal stent restenosis is not a benign clinical entity.  American Heart Journal 151(6) 1260-1264.

Dartmouth medical school.  Drug-eluting stent study: fewer procedures, same mortality rate.  Radiology today. (August 11, 2008).

Elhendy, A. & Hamby, R. (2007, January).  Balloon Angioplasty.  Retrieved March 1, 2009, from http://yourtotalhealth.ivillage.com/balloon-angioplasty.html

Maisel, W.H., & Laskey, W.K. (2007).  Drug-eluting stents. Circulation: Journal of the American Heart Association, 115-117.

Rihal, C. (2008, July).  Drug-eluting stents: do they increase heart attack risk?.  Retrieved February 23, 2009, from http://www.mayoclinic.com/print/drug-eluting-stents/HB00090/METHOD=print

Windecker, S., Remondino, A., Elberli, F., Jüni, P., Räber, L., Wenaweser, P., et al. (2005). Sirolimus-eluting and paclitaxl-eluting stents for coronary revascularization. The New England Journal of Medicine, 343(7) 653-662.