Who Needs a Coronary Artery Stent?
Presented by: William Fearon, MD
Director, Interventional Cardiology Research
Stanford University Medical Center
June 9, 2009
Lecture Overview:
- Stents are a minimally invasive alternative to bypass surgery to treat coronary artery disease, but is not appropriate for all patients.
- Cath lab tests can determine the extent of the vessel damage.
- While an angiogram is the gold standard of to diagnose blockage, other tests are being used that may be more accurate.
- Fractional flow reserve (FFR) measures coronary pressure to pinpoint spots of reduced oxygen delivery to the heart.
Coronary artery disease—the narrowing or blockage of arteries resulting in decreased blood supply to the heart—is the most common cause of mortality in the United States. More than 1.26 million Americans have a coronary attack each year, and it’s estimated that more than 7 million more have symptoms.
Coronary artery disease (CAD) occurs when the major blood vessels that supply the heart with blood become damaged or diseased—usually due to a buildup of fatty deposits of plaque. Over time, diminished blood flow may cause chest pain (angina), shortness of breath, or other symptoms. Because coronary artery disease often develops over decades, it can go unnoticed until it manifests as a heart attack.
While studies have shown that stents improve longevity and quality of life, and reduce the chance of heart attack, a question still remains as to which patients most benefit from a stent rather than coronary bypass surgery. While bypass surgeries in the U.S. have dropped by about a third in the past decade, the number of patients receiving stents has grown to nearly a million a year, in part because patients may be averse to major surgery.
“A bypass may be better in cases where the several vessels are damaged or if the main left coronary is affected,” said Dr. Fearon, “since there are still options in case something goes wrong.”
Assessing the Damage
Some of the problems in determining the benefit of a stent stems from a large-scale study called COURAGE, which compared outcomes in patients who received stents and patients who received medication to treat CAD. The study found that stents do not reduce death, heart attack, or other major cardiovascular problems when used on top of drugs; although they did reduce chest pain, the reduction was less than expected. Screening for participation was very selective for the trial, said Dr. Fearon, which eliminated high-risk patients and may have skewed the results.
The first step in diagnosing the extent of CAD is usually an electrocardiogram in a catheterization lab (cath lab) to track changes in the heartbeat, blood pressure, and other cardiovascular activity. However, more accurate tests are now available, said Dr. Fearon at a presentation sponsored by The Health Library. These include nuclear perfusion scans that show how well blood is flowing to various portions of the heart muscle by tracking the accumulation of radioactive substances that are injected into the bloodstream. A coronary angiography is another test that uses a catheter to insert dye into the coronary arteries that are then detected by a special kind of X-ray. Once physicians have an accurate map of the damage, they can proceed to repair the damaged artery with a stent or balloon angioplasty.
“An angiogram is the still the gold standard but does have some limitations,” he said. “There may be better ways to see who would most benefit from a stent.”
New Diagnostic Tests
New methods include intravascular ultrasound, which uses specially designed catheter to use sound waves to measure the interior of the blood vessels, which shows exactly where vessels are narrowed. Optical coherence tomography (OCT), which is still under clinical investigation, is similar in concept but uses light waves but provides 10 times greater resolution that ultrasound. “OCT may allow us to see the histology of plaque, which may allow us to identify patients at higher risk for rupture before an event takes place,” said Dr. Fearon.
Another promising diagnostic test is called fractional flow reserve (FFR), which measures coronary pressure to determine the likelihood of reduced oxygen delivery to the heart muscle. This new approach allows “on the spot” diagnosis of where a vessel is compromised and whether a stent is warranted.
“The pressure buildup is like a pipe that’s clogged up with rust,” said Dr. Fearon. “It helps us with the dilemma we often face: Does the patient really need a stent? Will it help prevent future adverse events?”
He described a case of a 50-year-old patient with high blood pressure and high cholesterol, who experienced chest pain. His EKG was normal, but he was admitted and further tests showed that he was having a heart attack. The FFR in the cath lab test showed narrowed vessels: the right vessel showed that 89 percent of the blood was still getting through, so the physicians left that one alone. However, the left vessel showed that only 59 percent of the blood was getting through the narrowed spot, so they placed a stent at that site.
“The benefit of the test was that it showed us that we could use just one stent, not two,” Dr. Fearon said. “The symptoms were relieved, and the patient was sent home. Our studies show that we can rely on this technique: If the FFR is low, it means the patient is at higher risk for an event later on and we should respond.”
Compared to angiography-guided percutaneous coronary intervention, FFR shows better outcomes, lower costs because fewer stents are placed and the use of less contrast materials, which can be hard on the kidneys. It also does not delay interventional procedures, said Dr. Fearon.
“We are learning more about coronary artery disease every day,” he said. “We know that some patients do need stents but now there are more refined techniques to determine who will most benefit.”
About the Speaker
William Fearon, MD, is an assistant professor of medicine (Cardiovascular Medicine) and director of Interventional Cardiology Research at Stanford. His work focuses on evaluating the significance of coronary artery disease to identify the best treatment and in determining the cause of chest pain in patients with normal appearing coronary arteries. Dr. Fearon received his MD from Columbia University, College of Physicians and Surgeons and completed a residency in Internal Medicine at Stanford, where he served as medical chief resident. He completed a cardiology fellowship and interventional cardiology fellowship at Stanford, where he has been on the faculty since 2002.
For More Information:
Request a free information packet on this topic from Stanford Health Library
About Dr. Fearon
http://med.stanford.edu/profiles/William_Fearon
Stanford Heart Center
http://www.stanfordhospital.com/clinicsmedServices/COE/heart/default
Department of Cardiothoracic Surgery
http://ctsurgery.stanford.edu/
American Heart Association
www.americanheart.org/
