Imaging tests for CHF patients could lead to cure
Revascularization reverses heart dysfunction
Scenario No. 1: A patient comes in with severe heart failure, and it seems that a majority of his heart muscle is dead. He becomes a candidate for heart transplant, and if he’s like 30% of transplant candidates, he dies on the waiting list.
Scenario No. 2: A patient comes in with coronary artery disease and less severe heart failure. She becomes a candidate for coronary artery bypass graft (CABG) surgery and has a 10% chance of dying in the operating room. She, like the transplant candidate, also has a significant chance that the procedure will not improve her condition.
If an expensive risky procedure has the potential to leave the patient at best in the same condition and at worst, dead, then how can you determine whether it’s worth the risk and the cost? The answer, according to cardiology experts and supporting data, is not as tricky as it may seem. In fact, it may be as simple as ordering all patients with evidence of heart failure and even a hint of coronary artery disease to undergo standard imaging tests that determine the amount of heart muscle that’s still living. Find the right patients, and you’ll greatly increase the possibility that revascularization either CABG or angioplasty will improve their heart function or possibly even cure the heart failure.
The key is ordering the tests thallium or sestamibi imaging or positron emission tomography (PET) scanning for each patient, even if their condition is improving with standard medical therapies, says James Udelson, MD, director of nuclear cardiology and co-director of the Heart Failure and Transplant Center at the New England Medical Center Hospitals in Boston. That’s because a subpopulation of patients with heart failure has reversible dysfunction of the heart that can be fixed with revascularization.
"They have a chronic state of low blood flow due to severe blockages of the heart arteries, which has been referred to as hibernation," Udelson says. "It’s like when a bear in winter slows down its metabolism and can’t really do anything and goes to sleep. Essentially, that’s what the heart does. The heart can compensate for low blood flow by a wall not moving. If it’s not moving, it needs minimal blood flow and oxygen, and so you’ve created a match between low supply and low demand."
In thallium and sestamibi imaging and PET scanning, materials are injected intravenously and taken up by the heart in proportion to how much blood flow and living tissue there is. Images then are taken that show tissue viability or metabolism of the heart. Thallium and sestamibi imaging are widely available, and PET scanning, while more complex and expensive, is becoming more available.
In the past, if a scan or echocardiogram showed a wall not moving, it was thought that wall had been permanently damaged by a heart attack. But now it is known that for many patients, that area of the heart is alive but hibernating. Such a patient is a perfect candidate for revascularization, which will improve blood flow and cause that area of the heart to start contracting again. "The overall function of the heart improves," Udelson says, "and you may cure the heart failure state completely."
Most patients could benefit from imaging tests. "The test defines whether it’s worth it to go on to revascularization," Udelson says. "If the walls are dead, then there’s no benefit, only a cost and a risk. But if they’re predominantly alive, there’s a tremendous benefit that’s worth the cost."
This information isn’t just an idea that sounds good; it’s been backed up by research done at the University of California at Los Angeles (UCLA). UCLA researchers directed by Jamshid Maddahi, MD, professor of nuclear medicine and radiologic science, did several studies on PET scanning in 1994. They found that before PET scanning, 70% of patients referred for heart transplantation went on to have the transplant, and 30% continued on medical treatment. After instituting PET scanning, only 29% had a transplant, while 26% were found to have enough living heart muscle to benefit from CABG. The other 45% had medical treatment. After five years, the survival rate for those who had a transplant and those who had CABG was virtually the same.
"The survival rate for CABG is as good as with transplantation for one-fifth the cost," Maddahi says.
Improved quality of life
But it’s not just the cost that’s important; it’s the quality of life, Udelson says. Correctly identifying patients who can benefit from revascularization means those people will avoid chronic heart failure therapy and multiple hospitalizations. They may not have to be on drugs forever, and they’re going to feel much better.
If the tests are widely available and have the potential to save so much money and lead to dramatically improved heart function, why aren’t they done on every patient? Maddahi says the equipment needed for PET scans is expensive, and the glucose solution needed for the test had not been easy to produce. Now, however, costs are coming down, and the glucose can be ordered instead of produced on-site. The test also has not been approved for Medicare reimbursement, but Maddahi says he thinks that will come soon.
But perhaps the main problem is lack of knowledge, Maddahi says. "The information has not caught on yet, but it will become an important issue in the near future. There is always a lag between data and practice. We have proven this since 1994, but there usually is not widespread application in the first three or four years. It’s so critical that every patient who has evidence of heart failure and coronary disease be tested. It’s almost malpractice if you don’t do it."
Udelson agrees that many physicians don’t know about the concept of hibernation or the right tests to order. "A patient comes in with shortness of breath and fluid in the lungs, and they are given a diuretic," Udelson says. "They feel better, but then they’re on those pills forever, and that’s all the physician will do. The patients are not investigated further for the underlying cause."
For many patients, the actual amount of the heart that has been damaged may be small, and those are the people who would benefit greatly from revascularization. If the tests show a majority of the heart is indeed scarred, then the physician can cross CABG or angioplasty off the list of potential treatments. Either way, you save money. Udelson says.
[For more information on revascularization, contact: James Udelson, MD, director of nuclear cardiology and co-director of the Heart Failure and Transplant Center at the New England Medical Center Hospitals, Box 70, 750 Washington St., Boston, MA 02111. Telephone: (617) 636-8066. Jamshid Maddahi, MD, professor of nuclear medicine and radiologic science, UCLA School of Medicine, 100 Medical Plaza #410, Los Angeles, CA 90095-7064. Telephone: (310) 206-9896.]
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