American College of Surgeons 90th Annual Clinical Congress

NEW ORLEANS—Patients at high risk for complications after heart surgery may benefit from an operation that does not place them on the heart-lung machine, according to a study reported at the 2004 annual Clinical Congress of the American College of Surgeons (ACS). The researchers found that high-risk patients had a lower rate of mortality than expected and overall positive outcomes. Based on his experience with such patients, John C. Chen, MD, FACS, believes that so-called off-pump coronary revascularization may be done successfully on patients with a history of stroke, calcification of the aorta (calcium deposits on the aorta that can break off and cause an end organ damage) or renal dysfunction (a precursor to kidney failure). Dr. Chen is a professor at the University of Hawaii and chief of cardiothoracic surgery at Kaiser Permanente, Honolulu, HI.

The standard on-pump procedure, which allows surgeons to operate on the heart at rest while blood pumps through a heart-lung machine, generates a systemic inflammatory response because the patient's blood comes in contact with artificial surfaces. This response may precipitate lung insufficiency, bleeding, kidney insufficiency, or stroke in high-risk patients, he said.

The on-pump operation also minimizes pulsatile blood flow. Unlike in a normally beating heart, there is no systolic (contraction) and diastolic (relaxation) blood flow during this procedure. The absence of normal heart movement is correlated with a high incidence of renal failure in patients with renal insufficiency. In addition, because the on-pump operation requires the aorta to be clamped, it can further compromise a calcified aorta, Dr. Chen added.

Despite these potential adverse effects, high-risk patients have routinely undergone on-pump coronary artery bypass graft (CABG) surgery because operating on a beating heart was not feasible until a number of surgical advancements were approved by the US Food and Drug Administration in 2000. One new surgical tool was the apical suction device, which is placed on the apex of the heart to hold it steady during surgery. Another was a stabilizing device that is placed on the coronary artery that is being revascularized to hold it relatively steady. "The artery is not completely still, but it is still enough so experienced surgeons can do the anastomosis (surgical connection) with good results," Dr. Chen said. Also making off-pump coronary surgery possible is a skilled team of surgeons, anesthesiologists, and nurses who can respond quickly and effectively if a patient's condition becomes unstable, he added.

Since 2000, Dr. Chen and his surgical team have performed 191 off-pump coronary artery bypass operations on high-risk patients. The observed mortality for these patients was less than expected. For 97 patients who underwent the procedure in 2002, the expected mortality as calculated by the Northern New England Cardiovascular Disease Study Group database, which includes a nationwide CABG registry, was 7.68 percent. But the observed mortality was only 4.17 percent. In 2003, the expected mortality for 54 patients who underwent off-pump surgery was 7.85 percent, while the observed mortality was only 1.85 percent.

The ratio of observed to expected mortality for patients who underwent off-pump surgery compared favorably with patients who had standard on-pump coronary revascularization. In 2002, the observed to expected mortality ratio was 1.01 for patients having on-pump surgery and 0.54 for patients having an off-pump operation. In 2003, the ratio was 0.45 for on-pump patients and 0.24 for off-pump patients. There was no difference between on-pump and off-pump groups in length of stay or in the incidence of postoperative atrial fibrillation (rapid heart motion), stroke, or acute onset tubular necrosis (loss of tubules within the kidney) over the course of the study.

On-pump surgery is still indicated for certain groups of patients, such as those who are having repeat CABG surgery or those who are having valve surgery in association with bypass graft surgery, Dr. Chen said. However, patients at high risk as well as those with low risk and concomitant diseases, such as renal insufficiency, will be better served by off-pump surgery, he added. Shelley A. Johnstone, RN, BSc, BSN; John Y. Lee, PA-C; Jamie S. Eng, MS; Kevin D. Murray, MD, FACS; and Lynne M. Grieco, MD, also participated in the study.

News from the 2004 Clinical Congress