Improving outcomes for coronary artery bypass surgery
by Joseph Sabik, M.D.
Cardiovascular & Thoracic Surgery
Miller Family Heart & Vascular Institute at Cleveland Clinic
If you have coronary artery disease (CAD), in which one or more of the main blood vessels feeding your heart is blocked, you may be facing coronary artery bypass surgery. A desire to improve outcomes after surgery and advances in technology have led surgeons to perform coronary artery bypass surgery without cardiopulmonary bypass, called off-pump bypass (also called "beating heart") surgery.
Traditionally, coronary artery bypass surgery is performed with the assistance of cardiopulmonary bypass. The heart-lung machine allows the heart’s beating to be stopped, so that the surgeon can operate on a surface which is blood-free and still. The heart-lung machine maintains life despite the lack of a heartbeat, removing carbon dioxide from the blood and replacing it with oxygen before pumping it around the body. The heart-lung machine has saved countless lives.
perfusionist next to heart-lung bypass machine
Off-pump coronary artery bypass surgery differs from traditional coronary artery bypass surgery, because the heart-lung machine is not used. Rather than stopping the heart, technological advances and new kinds of operating equipment now allow the surgeon to hold stabilize portions of the heart during surgery. With a particular area of the heart stabilized, the surgeon can go ahead and bypass the blocked artery in a highly controlled operative environment. Meanwhile, the rest of the heart keeps pumping and circulating blood to the body.
Off-pump coronary artery bypass surgery may be performed in certain patients with coronary artery disease. With present technology, all arteries on the heart can be bypassed off-pump. It may be ideal for certain patients who are at increased risk for complications from cardiopulmonary bypass, such as those who have heavy aortic calcification, carotid artery stenosis, prior stroke, or compromised pulmonary or renal function. Not all patients are a candidate. The selection of patients who undergo off-pump surgery is made at the time of surgery when the patient's heart and arteries are evaluated more closely.
Off-pump coronary artery bypass surgery is now possible, but is it better?
The aims of off-pump bypass surgery is to decrease the morbidity of coronary artery bypass surgery, such as stroke, renal failure and need for blood transfusion. Also of great interest is the possibility that the off-pump approach may lessen the risk of what are called cognitive changes that have been seen in many patients who underwent CABG with cardiopulmonary bypass. These short-term changes include memory loss, difficulty thinking clearly and problems concentrating for lengthy periods. They usually improve over the months following surgery. But a study in the February 8, 2001 New England Journal of Medicine raised the question of whether these short-term changes may affect long-term cognitive function. 1
Although the reason for these cognitive changes is not yet definitely known, many physicians believe the changes are related to the fact that emboli (tiny particles, most commonly atherosclerotic plaque) are dislodged into the bloodstream when the heart-lung bypass machine is used. As they travel throughout the circulation, the emboli may affect the brain, resulting in cognitive dysfunction.
Surgeons at The Cleveland Clinic recently completed a study 2 to date comparing the results of on- and off-pump coronary artery bypass surgery. The researchers matched 406 off -pump and 406 on-pump patients for comparison.
Both on- and off-pump surgery had low rates of death, stroke, or heart attack (MI) during surgery
They found that the results of both on- and off-pump surgeries were excellent. The risk of stroke, heart attack during surgery, and death were similar and low in patients undergoing both on- and off-pump CABG. There were fewer cognitive side effects in the off-pump patients, less renal (kidney) failure requiring dialysis, less red blood cell usage, and fewer infections of chest incisions in the off-pump patients. One concern is that off-pump patients had more incomplete revascularization, meaning that less patients had blood flow fully restored than on-pump patients. However, study author Joseph Sabik, M.D. states that with present day technology, patients should not worry. "We should be able to completely revascularize almost all patients."
"It’s important to remember that the results of both on- and off-pump coronary bypass operations are excellent," states Dr. Sabik. "Both have a very low risk of death, stroke, and myocardial infarction (heart attack)." He adds, " It is exciting to find with off-pump surgery, we can significantly reduce the morbidity of coronary artery bypass patients." The end result equals better outcomes for patients.
Are there patients who might benefit from off-pump surgery?
Off-pump surgery had a significantly lower rate of encephalopathy, dialysis, sternal wound infection (SWI) & need for red blood cell transfusions (PRBC)
Dr. Sabik and his co-authors believe there are. Since morbidity is reduced with off-pump revascularization, most patients should benefit from CABG performed without cardiopulmonary bypass. Patients at high risk for complications from cardiopulmonary bypass, such as people with vascular (blood-vessel) disease, previous strokes or mini-strokes (transient ischemic attacks), and those in their 70’s or older, should benefit the most from off-pump revascularization.
Surgeons are continually looking at ways to improve the outcomes in both kinds of surgery. For example, in on-pump surgery, improvements are being made to the heart-lung machine, and a filtration device that can capture tiny emboli before they do any damage has been designed and is being tested. In off-pump surgery, different ways of stabilizing small portions of the heart are being researched.
The good news for heart patients: Coronary bypass surgery is already extremely safe and effective, and becoming even more so.
Mark F. Newman, Jerry L. Kirchner, Barbara Phillips-Bute, et al. Longitudinal Assessment of Neurocognitive Function after Coronary-Artery Bypass Surgery, NEJM, 344 (6)*
Sabik J, Gillinov M, Blackstone E, Vacha C, et al. Do Off Pump Techniques Reduce the Morbidity and Mortality of Coronary Artery Bypass Surgery, J Thorac Cardiovasc Surg 2002 Oct;124(4):698-707*
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