Coronary bypass surgery (or coronary artery bypass grafting [CABG]) is a procedure that treats potentially life-threatening heart disease by creating new routes for blood to reach the heart muscle (myocardium). The surgery involves taking arteries or veins from other parts of the body—called grafts—and using them to reroute blood around clogged coronary arteries.

There are two types of coronary bypass surgery: on-pump and off-pump. With on-pump surgery, a mechanical pump, called a cardiopulmonary bypass machine performs the functions of your heart and lungs during the operation. This allows the surgeon to work in a motionless, bloodless surgical field, which is optimal for placing the grafts. Off-pump surgery involves stabilizing only the portion of the heart where the graft will be placed, and is performed without the use of a cardiopulmonary bypass machine.

Past research has suggested that off-pump surgery may decrease the incidence of serious adverse events that can occur at the time of on-pump surgery, such as damage to the heart, kidneys, or brain. However, there is also evidence that off-pump surgery may increase the rate of long-term complications, such as recurrent angina (chest pain) and the need for a second coronary artery surgery, compared to the on-pump approach.

To address this issue, a group of researchers decided to conduct a study comparing the quality and stability of grafts performed during off-pump surgery with those performed during on-pump surgery. The results of their study were published in the January 1 issue of the New England Journal of Medicine . The researchers found that although off-pump surgery appeared to be just as safe as on-pump surgery, the stability and quality of the grafts were better as a result of on-pump surgery.

About the study

A total of 104 participants, all of whom were scheduled for first-time coronary artery surgery and expected to receive at least three grafts, enrolled in the study. The researchers randomly assigned fifty of these participants to undergo on-pump surgery and 54 to undergo off-pump surgery.

After three months, all of the participants in the study underwent coronary angiography (an x-ray examination of the vessels and chambers of the heart) to determine the quality and stability of their grafts.

The findings

The researchers found that on-pump and off-pump surgery was equally safe: there were no significant differences between the two groups in terms of length of hospital stay, number of adverse events, or degree of cardiac damage. However, the researchers also found that after three months, 98% (127 of 130) of the grafts performed with on-pump surgery were stable and operating correctly, while only 88% (114 of 130) of the grafts performed with off-pump surgery were stable and operating correctly.

How does this affect you?

The researchers offer several possible reasons for their findings. For example, off-pump surgery is technically more demanding than on-pump surgery because the operative field is less stable and less visible. And although other studies have demonstrated a comparable degree of stability and quality for grafts performed during off-pump surgery, most of these patients were receiving only one or two grafts, not three, which is more representative of true multivessel disease in the population.

This important study questions the long-held assumption that less invasive is better than more invasive cardiac surgery. Although the more complex and risky on-pump surgery may have a higher rate of adverse events, it still may be a better choice for long-term cardiac health. It is quite likely, however, that as surgeons gain more experience with the off-pump technique, post-surgical outcomes will improve. Until then, the off-pump approach is probably best left for selected patients who have fewer vessels in need of bypass and who can tolerate a second procedure if the need arises.