The P&S Journal: Spring 1998, Vol.18, No.2
"Keyhole" Surgery for Hearts
Minimally invasive heart surgery has become increasingly popular in the past few years, with more and more patients requesting the so-called "keyhole" bypass surgery and more and more hospitals offering doctors who perform the technique. Yet despite all the hoopla, the benefits of the operation have not yet been fully demonstrated by clinical trials. At P&S, Drs. Mehmet Oz, Irving Assistant Professor of Surgery, and Windsor Ting, instructor in clinical surgery, are helping to fill in the knowledge gap with clinical studies of the technique. And to help other physicians learn the new skills required for the innovative procedure, they have established a training program.
In conventional bypass surgery, the surgeon makes a foot-long incision in the chest, breaks the sternum to gain access to the heart, and places the patient on a heart-lung bypass machine. MIDCAB (for minimally invasive direct coronary artery bypass) surgery potentially avoids all three of these steps. The surgeons perform part of the operation through endoscopes, so the typical incision is about three to four inches long. Because the incision is made either between the ribs or in the lower part of the sternum, surgeons do not have to break the entire sternum. Plus, the operation is done while the heart is still beating, eliminating the need for a heart-lung bypass machine. Patients are given beta blockers to slow their hearts, and a specially designed metal device pushes against the heart, stabilizing it during surgery.
MIDCAB seems to offer several advantages, says Dr. Ting. Many patients don't need transfusions during surgery, and most can be extubated immediately after leaving the operating room. Patients spend less time recovering in intensive care and in the hospital-often as little as three days, as opposed to the five days that generally follow conventional bypass surgery.
Surprisingly, the small incision of MIDCAB is not the main benefit of the surgery, according to a P&S study published in the November 1997 issue of Chest. The study, by Drs. Oz, Michael Argenziano, and Eric Rose, found that the main benefit came from avoiding the use of a heart-lung bypass machine, which causes injuries to the heart, lungs, kidneys, and, most important, the brain in approximately 6 percent of all conventional bypass surgeries. "With a heart-lung machine, there is a risk that particulate matter will not be filtered out and will wind up in the vessels of the head," says Dr. Oz. "Also, heart-lung bypass requires placement of a tube in, and manipulation of, the aorta and may knock off tiny plaques, which can then make their way to the head." Because of these factors, the most fulfilling use of MIDCAB is in high-risk patients who are more likely to develop complications from heart-lung bypass. Dr. Oz and colleagues-including collaborators from Cornell-are now working to develop a study of MIDCAB in low-risk patients to quantify the benefits of the technique.
Because the surgery is so new-and the techniques involved are so different from what most surgeons are used to-Drs. Oz and Ting have put together a two-day continuing medical education program on MIDCAB. The course uses a model of a heart that actually beats to teach doctors to operate on a moving heart. Doctors learn to operate with endoscopes by practicing on a special toolbox that has holes for the endoscopes but that completely blocks the surgeon's view of the "body" being operated on. This forces doctors to look at a screen that projects what a camera on the endoscope "sees."
Despite the popularity of MIDCAB, the operation still poses major questions that need to be answered, says Dr. Oz. No one knows, for instance, whether the long-term results are as good as conventional surgery. "The technique has not been around long enough for those sorts of studies to have been done," he says. "I think it's incumbent upon academic medical centers to study these questions. The operation shouldn't be done willy-nilly."