Transcatheter Therapy for Aortic Valve Stenosis

Presented by: William Fearon, MD
Assistant Professor, Cardiovascular Medicine
Stanford University Medical Center
October 7, 2009

Lecture Overview:

• Aortic stenosis is a condition in which the valve between the heart and the aorta becomes narrowed, affecting the flow of blood
• It is most common in people over age 65, and symptoms often don’t manifest until age 70 or older
• While open heart surgery is still the gold standard to repair a damaged valve, new minimally invasive options are being studied for certain high-risk patients
• Stanford is involved in a national study to refine a promising technique called transcatheter aortic valve replacement

Aortic valve stenosis occurs when the heart’s aortic valve becomes narrowed, which obstructs blood flow from the heart into the aorta and to the rest of the body. The obstruction causes the heart to work harder to pump blood, eventually weakening the organ and causing symptoms like fatigue, shortness of breath, dizziness, and chest pain. The condition may not produce warning signs at first, making it difficult to detect.

Aortic valve stenosis is most often caused by calcium buildup. Over time, the mineral can be deposited as blood flows over the valve and cause the valve to stiffen and narrow. Lipid deposits can also be a source of obstruction. Because this accumulation takes many years to develop, aortic stenosis is most common in people over age 65, and symptoms often don’t manifest until age 70 or older. In the past, and in many developing countries today, stenosis was often a result of rheumatic fever.

“Once symptoms develop, the average survival time is less than two years when treated medically,” said William Fearon, MD, and assistant professor of cardiovascular medicine, at a presentation sponsored by the Stanford Hospital Health Library. “And because aortic stenosis affects older people, many patients are unable to undergo the stress of open heart surgery.”

The condition appears to be increasing, in part because people are living longer. About 3 percent of the population older than 75 has moderate to severe aortic stenosis, he said, while about 5 to 7 percent of people older than 85 have a severe condition. Because there are no truly effective medications available, many of these people forego treatment because they are too ill or frail to withstand open heart surgery-the gold standard for treating the disease. In fact, he added, one study showed that more than one third of patients with aortic stenosis were not referred for surgery because of the high risk of mortality. Another study showed that about 9 percent of patients between age 80 and 89 don’t survive the surgery; for people over age 90, about 13 percent don’t survive.

“These tend to be older, high-risk patients and mortality is unacceptably high,” said Fearon. “Open heart surgery is very risky for these patients, so there is great interest in developing new techniques.”

Dilating the aortic valve is one option. Balloon aortic valvuloplasty involves the use of a thin catheter tipped with a balloon that is guided through a blood vessel in the groin up to the heart. Once in position, the balloon is inflated, stretching the valve opening to improve the blood flow. This approach is considered a temporary measure because the valve tends to narrow again (restenosis) in about half the patients, and so is reserved for only the very ill, Fearon said.

However, recent improvements to both the technology and the technique of the surgery are showing significant improvements in outcomes. Stanford is involved in studies using a smaller balloon that appears promising, but the longevity of this approach remains a concern, he said.

Another promising option is called a transcatheter aortic valve replacement. Using a catheter or a small incision in the chest, surgeons insert a stent to open the valve and position a bioprosthetic valve in place, usually from a cow or a pig. The procedure can be performed in the catheterization lab under local anesthesia, without major surgical incisions, or the use of a heart-lung bypass machine. First performed in 2002, about 10,000 of these procedures take place each year, mostly in Europe.

In the United States, two types of devices are being tested, and the procedure is still being refined and simplified. Stanford is involved in a national, multi-site study called PARTNER (Placement of AoRTic TraNscathetER Valves) to evaluate the safety of one of the devices. A web-based risk calculator is used to determine whether a patient meets the criteria to participate in the trial. Initially, patients were randomly assigned to either traditional surgery or transcatheter aortic valve replacement, but now the randomized study has concluded and there is an ongoing registry. Results from the randomized portion of the study will be compiled by next year, Fearon said.

He described a case of a 75-year-old patient with critical aortic stenosis, who had a history of kidney problems and chronic obstructive pulmonary disease from years of smoking. With no symptoms for many years, she suddenly showed severe heart problems, including poor valve function. Because she was at high risk for surgery, doctors were able to include her in the PARTNER study.

“She was stented and received a new valve that started working immediately,” said Fearon. “She went home five days after her surgery.”

The procedure does have some limitations: Leakage is still a drawback, and if the new valve is misplaced it cannot be repositioned. Another question that remains is how durable and long-lasting the new valves will be.

“Despite the limitations, transcatheter aortic valve replacement is really taking off,” Fearon said. “Companies are looking at new and better ways to address the potential problems of the two valves currently available, and interventional cardiologists are improving the techniques and technology.”

About the Speaker
William Fearon, MD, is an assistant professor of medicine (Cardiovascular Medicine) and director of Interventional Cardiology Research at Stanford. He 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:

Stanford Health Library can do the searching for you. Send us your medical questions.

About Dr. Fearon
http://med.stanford.edu/profiles/William_Fearon

About the PARTNER clinical trial
http://med.stanford.edu/clinicaltrials/detail.do?studyId=1263

Stanford Heart Center
http://www.stanfordhospital.com/clinicsmedServices/COE/heart/default

Department of Cardiothoracic Surgery
http://ctsurgery.stanford.edu/