The Heart Beats On: Use of “Off-Pump” Coronary Artery Bypass Surgery—Commentary

Coronary artery bypass surgery (CABG) is used to treat coronary artery disease, a condition in which the blood supply to the heart is blocked. In a CABG procedure, doctors take an artery or vein from another part of the body to connect the aorta (the major artery that takes blood from the heart to the rest of the body) to a coronary artery past the point of its blockage. Blood flow is thus rerouted, skipping over (bypassing) the narrowed or blocked area.  

There are two main types of CABG procedure:

• The traditional on-pump procedure in which the heart is stopped during surgery and a heart-lung machine is used to circulate blood
• A newer off-pump procedure in which the heart continues to beat during the surgery

In the traditional on-pump CABG procedure, the person’s heart is stopped during surgery and blood is circulated to the body using a heart-lung machine. This procedure keeps the heart still while surgeons work on it.

CABG improves the quality of life for people with coronary artery disease. After the surgery, people have a lower risk of heart attacks and may be able to exercise more easily. But CABG surgery is not without risks. People who undergo CABG procedures are at risk of sustaining cognitive deficits and strokes. Doctors have thought that the heart-lung bypass machine may have contributed to these complications.

So, in an effort to reduce the risk of complications, doctors began using a surgical technique that does not require use of a heart-lung bypass machine. Not using the machine means that the person’s heart must continue to beat during surgery—which makes the surgery technically more difficult to do. So researchers wanted to ensure that results with the newer technique were better before abandoning the traditional procedure.

Studies comparing the types of procedure

A recent large multicenter randomized trial published in the New England Journal of Medicine examined the 5-year outcomes after bypass surgery. The results support using on-pump coronary artery bypass grafting as the preferred surgical technique.

 Results from prior research that had more limited follow-up periods did not show a reduction in complications with the off-pump procedure, and one review of the data surprisingly found increased risk of death in patients who underwent off-pump CABG.

What did this study show?

The 5-year follow-up results of this trial further clarify best practice regarding on-pump versus off-pump CABG. Patients who underwent on-pump procedures were more likely to be alive 5 years after the procedure than patients who had an off-pump procedure. They were also less likely to have a heart attack or to need an additional procedure to open a blocked artery in the heart.

Should off-pump CABG still be used?

So, should off-pump CABG be relegated to surgical text books? This large, well-designed study, especially when combined with the results of previous studies, should decrease surgeons’ enthusiasm for the more technically challenging off-pump bypass. The mounting evidence of improved outcomes supports the use of on-pump CABG for the majority of patients. Nevertheless, there are exceptions.  Patients who have a heavily calcified aorta, sometimes called a porcelain aorta, have a high risk of stroke when the aorta is manipulated during bypass surgery. In these patients, the risk of stroke due to aorta manipulation offsets the potential benefits of on-pump CABG. In these patients, the off-pump procedure remains a reasonable approach as long as the surgeon has experience with the technique.

Future studies may well identify other groups of patients at high risk of complications from on-pump CABG who may benefit from off-pump CABG. In the meantime, on-pump CABG appears to be the best option for most people. And people who are undergoing CABG procedures may want to discuss the type of procedure with their surgeon.