Heal the heart, hurt the mind?
When former President Bill Clinton underwent quadruple coronary bypass surgery on Labor Day, he spent 73 minutes hooked up to a heart-lung machine while surgeons rerouted blood vessels to his heart.
At 58 and in relatively good health, Clinton stands a good chance of fully rebounding from the bypass surgery, in which doctors replace clogged arteries to the heart with veins and arteries taken from elsewhere in the body.
But many people who undergo the procedure -- as 305,000 Americans did in 2001, the latest year for which figures are available -- find that their brains don’t function as well as they did before. These effects can dissipate in a few days or continue for months or years.
In the medical world, this effect is commonly referred to as “pump head,” reflecting the widespread, though unproven, belief that the condition is caused by the heart-lung machine. The machine is used when the heart is stopped during surgery, and the theory is that this results in small blood clots, air bubbles and other debris traveling to the brain and disrupting memory.
Nobody really knows how common “pump head” is because, outside of research studies, most cardiac patients aren’t tested on intellectual function before and after surgery. Detecting all but the most subtle cognitive changes “depends on how hard you look,” said Dr. William Cohn, director of minimally invasive surgical technology at the Texas Heart Institute in Houston.
Nonetheless, it has been “convincingly demonstrated that measurable cognitive dysfunction is actually a common complication of CABG [coronary artery bypass graft] surgery, with an incidence of 80% to 90% at hospital discharge,” as Duke University researchers Dr. Daniel B. Mark and Dr. Mark F. Newman put it in an editorial in the Journal of the American Medical Assn. in 2002. Even five years after discharge, 42% of patients still show measurable cognitive decline, Mark and Newman found in their own study, published in 2001 in the New England Journal of Medicine.
Many cardiologists, among them Dr. Christopher Cannon of Brigham and Women’s Hospital in Boston, say that deficits are most likely to occur in older patients who, in addition to having clogged arteries to the heart, may have blockages in blood vessels in the brain as well. In other words, what some see as a consequence of heart surgery may be a consequence of generalized atherosclerosis.
At the moment, there is no cure for “pump head.” Doctors do not understand why some patients who get it improve over time and others do not.
Though it’s not clear today that the heart-lung machine is the real culprit in “pump head,” many doctors for years assumed it was and focused their prevention efforts on the machine itself.
Older heart-lung machines were fairly crude, said Dr. Irv Kron, chairman of the department of surgery at the University of Virginia. “There were no filters; the technology was terrible,” he said, allowing bits of particulate matter to travel to the brain.
Now the machine’s tubing is coated with material that reduces the body’s inflammatory response, which can be triggered as blood cells course through the machine. Historically, this inflammatory response was believed to cause some of the cognitive problems after surgery, said Dr. William Baumgartner, chief of cardiac surgery at Johns Hopkins Hospital in Baltimore. A better solution, some doctors say, would be to get rid of the pumps altogether and operate on still-beating hearts using special devices.
But off-pump surgery, though it has been increasing in recent years, is used in only about 22% of bypass procedures, said Dr. John Puskas, an associate professor in the division of cardiothoracic surgery at Emory University in Atlanta. “I think it’s clear that off-pump is better, but proving it with scientific rigor is challenging,” he added. In general, off-pump patients leave the hospital a day or so sooner, have less blood loss and may have fewer kidney problems.
One study by Dutch researchers in 2002 found that although the off-pump group had better cognitive outcomes right after surgery, by one year later, the difference was negligible -- a 31% decline in the off-pump group versus a 34% decline in the on-pump group.
Other doctors question how valuable off-pump surgery is because, despite the name, “pump head” can occur occasionally after operations in which heart-lung machines are not used, perhaps because of the sheer stress of surgery, the duration of anesthesia, postoperative infections or respiratory problems.
At Johns Hopkins, Baumgartner’s team compared heart patients who underwent on-pump bypass surgery with equally sick patients who did not have bypass surgery. One year later, there was no difference in cognitive function between the two groups.
Patients may find comfort in knowing that many cardiologists, including Dr. Frank Sellke, chief of cardiothoracic surgery at Beth Israel Deaconess Medical Center in Boston, believe the operations are “fairly equivalent.”
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