This article originally appeared in the May 2004 Harvard Health Letter and is provided courtesy of Harvard Health Publications.

Off-pump vs. conventional bypass: Which is better?

So far there’s no clear winner. It may depend on the type of patient and the surgeon’s ability.

The heart-lung machine is a remarkable device that pumps blood through the body like the heart and restocks it with oxygen like a pair of lungs. It allows heart surgeons to stop the heart while they’re operating, so instead of working on a pulsating muscle, blood still coursing through its four chambers, they have a still one, with the blood largely rerouted around it. The heart-lung machine has made coronary artery bypass grafts and heart valve operations safer/more effective.

But progress tends to have a price. Stopping the heart may cause some subtle harm to the heart itself. Sometimes blood cells seem to get damaged as they go through the heart-lung machine. The surgeon clamps off the aorta during a conventional bypass operation. If the inside of the aorta is lined with atherosclerotic plaque, small pieces of it may break off, travel to the brain, and cause tiny blood clots.

Off-pump coronary artery bypass was developed to avoid cognitive impairment and other problems possibly caused by the heart-lung machine and the stopping of the heart. “Off-pump” means no heart-lung machine: The surgeon operates on a beating heart with blood still flowing through it. Medical device companies have come up with ingenious “cardiac stabilizers,” some with tiny suction cups on the bottom, that allow surgeons to hold small areas of the heart steady while they sew blood vessels to coronary arteries. It’s a bit like holding a fork against the top of an undulating bowl of Jell-O.

Not a home run
In the United States, about 20% of coronary artery bypass operations are now performed off-pump. Randomized trials comparing off-pump with conventional bypass haven’t uncovered the kind of large or consistent differences in mortality rates or serious consequences (like strokes and heart attacks) that demonstrate superiority hands down. It may be a little easier on the heart: Immediately after the operation, off-pump patients have lower levels of enzymes released by damaged heart muscle. The blood may suffer less damage, too, and as a result, off-pump patients tend to require fewer transfusions.

On the other hand, the off-pump procedure has not shown any decided advantage in protecting the brain. In one of the largest studies of cognitive outcomes, Dutch investigators found that off-pump patients scored better than conventional patients three months after the operation, but the advantage faded after a year.

Another crucial question is whether the operations are equally effective in restoring blood flow to the heart — which, after all, is the whole point of coronary artery bypass. One way to assess that is to see whether the blood vessels grafted to the coronary arteries to restore blood flow stay open (patent). A British study published in the New England Journal of Medicine in 2004 compared the patency of off-pump and conventional bypass grafts. Three months after the operation, 98% of conventional bypass grafts were open, compared with 88% of those completed using the off-pump procedure.

Advisable for some, but for whom?
Surgeons who champion the off-pump operation recommend it for elderly patients (“elderly” is not terribly well defined) and, sometimes, people who’ve had strokes. Others would limit it to those most at risk from the heart-lung machine — in particular, people who have lung or liver problems, a tendency to bleed, or significant atherosclerosis in the aorta. The latter might be the clearest indication for an off-pump procedure because of the stroke risk that accompanies the conventional operation.

If you or someone you know is faced with a choice between on-pump and off-pump bypass surgery, keep in mind that off-pump is technically difficult. Surgeons say the operation has a steep learning curve. You don’t want to be operated on by someone at the bottom of that curve.