Archive for June, 2009

From the Associated Press:

Heart attack survivors are again being enrolled in a controversial federal study of an alternative treatment while the government investigates whether they were told enough about possible health risks.

The $30 million study, with 1,500 participants so far, is one of the largest alternative medicine experiments ever launched. It tests high doses of vitamin and mineral supplements and chelation, a treatment used for lead poisoning that has not been proved safe or effective for heart disease.

Researchers suspended enrollment last August, when the federal Office of Human Research Protections began a probe into whether the people in the study were being fully informed of risks and adequately protected.

Chelation (pronounced kee-LAY-shun) involves intravenous doses of a drug, in this case disodium EDTA. Proponents claim it can flush out calcium that has built up in artery walls. Stiff or clogged arteries can lead to heart problems. There already are several conventional treatments for heart disease, including medicines, surgery and artery-clearing angioplasty.

When the study began in 2002, it aimed to enroll 2,400 people at more than 100 sites in the United States and Canada. But recruitment has lagged, and study leaders now hope to enroll at least 1,700.

Around a long time, IV Chelation therapy has is detractors and proponents. My wife works for an eye doctor whose father and grandfather had major blockages in their corotid arteries. After undergoing this therapy, both blockages were substantially reduced. It is also practiced in some countries in Europe. The time for a study of this technique is long overdue in the United States. Should chelation therapy prove effective, there won’t be too many patients walking around with 25 stents or bypass surgery scars. Of course, there will also be a great loss of cash flow for both surgeons and interventionalists.

Hmmm.

From PTCA.org comes an excellent article converning the use of IVUS (emphasis mine):

A study, published in the current issue of JACC Interventions, details 120 drug-eluting stent cases as viewed by intravascular ultrasound (IVUS) in order to examine characteristics that may lead to in-stent restenosis (ISR) or stent thrombosis.

Underexpansion of stents, both drug-eluting and bare metal, has been long identified as a significant predictor of adverse clinical events. Prominently discussed by Dr. Antonio Colombo in the early days of stenting, inadequate expansion of the stent struts is known to increase these problems.

This latest examination studied whether there was a difference in the type of underexpansion that caused thrombosis (blood clotting) versus in-stent restenosis (the growth of excess tissue inside the stent) in drug-eluting stents (DES). Dr. Akiko Maehara and a team from the Cardiovascular Research Foundation and Columbia University Medical Center in New York looked at 20 definite DES thrombosis patients, which represented all definite thromboses from 1,407 consecutive DES patients who underwent intravascular ultrasound imaging. These were compared to 50 risk-factor-balanced ISR patients with no evidence of stent thrombosis and 50 risk-factor-balanced “no-event” patients with neither thrombosis nor ISR.

Using IVUS allows the cardiologist to see not only the amount of blockage, as in a 2D angiogram, but the spatial and volumetric relationship of the blockage to the actual arterial wall in three dimensions. An issue with inadequate stent expansion is that, using angiography alone, the operator may not be sure that the stent struts are pressed up against the interior surface of the coronary artery. Additionally, by using a 3D real-time reconstruction of an IVUS “pull-back” (the right image above), the interventionalist can see immediately after stent implantation any eccentricities of the arterial segment and can ensure that full expansion has occurred. If the stent is not adequately expanded, the placement can be “touched-up” with a high-pressure balloon expansion in all or part of the stent. Incomplete expansion allows a space to exist between the stent struts and arterial wall, a space where thrombus can form and can also promote unwanted tissue growth which then blocks the stent.

85% of the thrombosis studied in this report occurred within 30 days of the stent procedure, pointing up the fact that inadequate placement, not the drug or polymer or other characteristics of the drug-eluting coating, was the prime predictor. The study concluded, however, that there is a difference between underexpanded stents that thrombose versus underexpanded stents that restenose: the underexpansion in DES that thrombose is more severe, more diffuse, and more often proximal in location. The researchers found that in cases of thrombosis, the proximal parts of many of the stents were inadequately expanded, possibly because stents are usually sized more for the center and distal ends of blockages where there is more disease.

The 85% statistic is all the ammunication necessary to demand the use of IVUS in your own procedure. If you cardiologist is not able to perform IVUS due to lack of exposure to the technique or lack of the proper equipment, I would strongly recommend finding another cardiologist. Ask your doctor if he/she uses IVUS and what level of expertise they possess. Although we all hope a visit to the emergency room is not in our future, if you are a heart patient, talking to your cardiologist now and possibly switching doctors before your next procedure makes sense.

Fractional Flow Reserve, or FFR, is a guide wire-based procedure. Its utilility is that it can accurately measure blood pressure and flow rate through a specific part of the coronary artery. Is is performed through a standard diagnostic catheter during the actual coronary cathaterization. Using Fractional Flow Reserve, the interventinalist can assess whether or not to perform angioplasty or stenting on “intermediate” blockages – blocakges that may or may not cause angina symptoms or lead to serious ischemic events.

The entire point of using a stent in the coronary arteries is to increase blood flow to the heart. However, a number of studies have shown that if a “functional measurement”, such as Fractional Flow Reserve, indicates the flow is not significantly obstructed, the blockage or lesion does not need to be revascularized (angioplasty) and the patient can be treated safely with medical therapy.

The Interventinalist’s tendency to stent is well documented. Some more aggressive than others. In the case of my cardiologist, if he notices a blockage of 75% or greater, he will stent it. Some cardiologists will stent a 50% blockage. But what if FFR indicated that an intervention won’t have a significant impact on a particular blockage? Being able to better select cases not only saves health care costs, but contributes to more appropriate patient care.

The recent COURAGE trial has only re-emphasized what all current medical guidelines recommend: that for low risk patients, even those experiencing angina, optimal medical therapy should be the initial treatment. For those patients whose disease progresses, or for whom chest pain is not alleviated, revascularization, either through angioplasty and stenting or surgery, should be performed. Fractional Flow Reserve can be a significant tool to help physicians in deciding whether to intervene or not. Here are some results of some additional studies:

• DEFER study: Patients who have been screened out of angioplasty by using FFR have not experienced an increase in adverse outcomes. And in these studies, two-thirds of the patients were judged not to need an intervention with balloons or stents.
• FAME study: FFR allowed elimination of a third of the lesions that might have been stented using angiography alone, with better outcomes for patients.

In the next post we will be talking about Intravascular Ultrasound (IVUS) and why you should insist your cardiologist use this technology if you are going to get a stent.