No clear winner in traditional vs. off-pump bypass surgery

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No clear winner in traditional vs. off-pump bypass surgery

A panel of experts commissioned by the American Heart Association says that on-pump and off-pump bypass surgery are equivalent, though each has its advantages and disadvantages.

Fifty years ago, fixing a narrowed or blocked coronary artery was part science fiction and part fantasy. Today, such repairs are almost run-of-the-mill, giving second chances to a million or so hearts a year in the United States alone.

The first “fix” was coronary artery bypass surgery, a major operation to reroute blood around blocked vessels. Then came angioplasty, which opens an artery with a tiny balloon that flattens the cholesterol-filled bulges that block blood flow. Each has been modified and improved, making for a multitude of choices.

Which is right for you? That depends on your preferences, heart, and surgeon. Weighing the risks and benefits of angioplasty, bypass and medical therapy is an important consideration. So is making sense of what the American Heart Association (AHA) calls “one of the most hotly debated and polarizing issues in cardiac surgery” — whether either traditional bypass surgery or the newer off-pump bypass outshines the other.

An AHA panel co-chaired by Dr. Frank Sellke, chief of cardiovascular surgery at Harvard-affiliated Beth Israel Deaconess Medical Center, concluded the two procedures are equally effective, though each has its advantages and disadvantages. This is reassuring for anyone contemplating bypass surgery, but it isn’t likely to quell the controversy.

Anatomy lesson

The muscle and nerve cells that make up the heart can’t get nourishment from the blood that flows through the heart. That would be like trying to drink from a fire hydrant. Instead, these cells get oxygen-rich blood from a network of smaller vessels called the coronary arteries.

They begin at the aorta, the main pipeline for oxygenated blood. The right coronary artery and left coronary artery are each about as wide as a drinking straw. Like branches on a tree, they subdivide into progressively smaller vessels. Some hug the surface of the heart; others burrow into it.

The inner walls of the larger coronary arteries are prime places for the buildup of cholesterol-filled plaque. When these fatty deposits jut into the open space through which blood moves, they curtail blood flow.

At rest, this reduction is often unnoticeable — the narrowed artery provides enough oxygenated blood to meet the needs of its section of heart mus­cle. Let demand outstrip the supply, though, such as when you climb the stairs or run after a grand­child, and the heart complains with the chest pain or tightness known as angina.

A totally blocked coronary artery gives rise to a different and more serious problem — a heart attack.

Conventional bypass surgery Traditional on-pump bypass surgery starts with splitting the ster­num (breastbone). This opens the chest cavity and reveals the heart. Once blood flow has been routed through the heart-lung machine, the surgeon stops the heartbeat. If a vein from your leg or an artery from your arm is used for the bypass graft, the surgeon sews one end to the aorta and the other end to the problematic coronary artery just below the blocked section. If the left or right internal mammary artery is used, the “free” end is sewn to the diseased artery.

Off-pump bypass surgery An off-pump bypass begins much like the traditional version, by splitting the sternum and opening the chest. Instead of stopping the entire heart, a special stabilizer holds still the portion of the heart containing the diseased coronary artery. This lets the surgeon sew together blood vessels on a nearly motionless section of the muscle. The rest of the heart continues to beat and pump blood to the body. The bypass grafts are made much as they are during a traditional bypass.

Grand detour

The introduction in 1953 of a machine that temporarily takes over the work of the heart and lungs paved the way for coronary artery bypass surgery. The heart-lung pump made it possible to stop the heart for an hour or so without depriving the body of a steady supply of oxygenated blood. It allows a surgeon to work on a motionless muscle, instead of one that contracts and relaxes once a second. A motionless, bloodless operating field is useful, since the blood vessels involved in a bypass graft can be as thin as cooked spaghetti and just as slippery, while the thread for sewing them together is finer than a human hair.

As with almost everything in medicine, the heart-lung pump has drawbacks as well as advantages. It forces blood to touch something other than the specialized layer of cells lining blood vessels. Contact with the foreign surface of the pump touches off a riot of inflammation and generates a shower of tiny particles.

Connecting the aorta to the heart-lung pump can also be a problem. This large, curved artery can be loaded with atherosclerotic plaque. Poking and prodding it can shake loose small chunks of this fatty material.

The heart-lung pump circulates these tiny blood clots, bits of plaque, and other debris to the brain and the rest of the body. They can cause a stroke. They have also been implicated in the mental fog that sometimes follows bypass surgery.

Pump-free alternative

In an effort to avoid the possible complications linked with the heart-lung machine, surgeons have been working on pump-free alternatives since the early 1960s. Off-pump bypass surgery took off in the mid-1990s, sparked by new devices that immobilize only the section of the heart with the diseased coronary artery while allowing the rest of the heart to beat and circulate blood.

Today, about 1 in every 5 bypass operations is done without using a heart-lung machine. An off-pump bypass may be a bit easier on the body, especially the kidneys, and may get you out of the hospital and back home a tad sooner than the traditional bypass.

A June 2005 report from the National Heart, Lung, and Blood Institute, however, cautions that the adoption of the off-pump technique has spread in a haphazard manner. There are some concerns that beating-heart grafts may be more prone to failure than those done on a motionless heart. It is also possible that people who have off-pump bypass may not always have as many arteries bypassed as they need, since it can be harder to get at some parts of the heart with the off-pump technique.

Apples and oranges

Competition spurs improvement, so the thinking goes. It can also lead to overly enthusiastic claims. Some heart surgeons and medical centers aggressively promoted off-pump bypass as a safer, simpler operation with a faster re­­covery and fewer complications than traditional on-pump bypass.

To cut through the claims, the AHA convened heart surgeons, cardiologists, anesthesiologists, and neurologists — some advocates of conventional bypass and others advocates of the off-pump approach — to review the evidence.

What the panel was able to glean from the few high-quality studies is that both types of bypass are equally safe and effective. (The report appeared in the May 31, 2005, Circulation.) With both procedures, surgery-related death rates range from less than 1% to more than 6%. According to the panel, this means that other things are more important for your long-term outcome than the type of procedure you pick. These factors include

• your surgeon’s skill and experience with the operation

• the care you get from other members of the team, such as anesthesiologists, doctors and nurses in the intensive care or recovery unit, and the nurses on the floor where you’ll spend a few days after the operation

• the quality of the hospital where you’ll have the operation.

If you’ve been advised to have bypass surgery, ask your surgeon if one type is better for you than the other. If it’s a toss-up, work together to choose one. Then ask the hard questions, like how many bypasses he or she does each year (more than 100 is good), and how many are done in your hospital (more than 200 is good). These are what really matter.

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Last updated:	August 21, 2006