Minimally Invasive Cardiac Surgery

William R. Mayfield, M.D.

Peachtree Cardiovascular and Thoracic Surgeons, P.A.

Rationale

The rationale for Minimally Invasive Cardiac Surgery is to decrease the morbidity of cardiac operations. To decrease morbidity, we mean that the impact on a patient of a given operation will be reduced over the impact of using conventional methods.

Definition

Minimally Invasive Cardiac Surgery is defined as cardiac surgery without the use of the heart lung machine, or without the use of the large breast bone incision (called a sternotomy.) Some patients can have cardiac surgery without either one.

Means

There are several ways that the impact of the surgery is reduced.

One way is to avoid the use of the sternotomy, the incision down the center of the sternal bone. By avoiding sternotomy, the patient typically returns to work or normal activity sooner, usually has less pain than by sternotomy, and avoids the risk of mediastinitis, a dangerous infection behind the sternum. The sternotomy can be avoided in most valvular operations, and in some coronary bypass operations.

Another way to reduce the impact of the cardiac surgery is to avoid the use of the heart lung machine, known as the cardiopulmonary bypass machine. The use of the heart lung machine is associated with some complications, such as stroke, memory loss, kidney failure, lung failure, and bleeding. Although the heart lung machine is indispensable for many heart operations, such as valve replacement, it is no longer necessary for other operations, such as some coronary artery bypass operations, the most common cardiac operation.

Cardiac surgery without the use of the heart lung machine requires operating on the beating heart. We have developed new technology and techniques that now make surgery on the beating heart safe and effective.

Results

The result of applying minimally invasive techniques to cardiac surgery has improved several outcomes. The intensive care unit stay is shortened, the hospital stay is shortened, the pain is reduced, cosmesis is improved, the return to work and play is shortened, and the overall cost of the operation and recovery is reduced.

Technology Development

Several areas of cardiac surgery have come under intense development.

Cardiac Regional Stabilization

In order to do coronary bypass surgery on the beating heart, the area of the heart to undergo surgery must be immobilized. Devices that lie against the heart and stabilize the target area have been developed. These stabilizing devices are held by hand, or attached to retractors that expose the target area. The stabilizing devices quiet the cardiac motion in a small area, just enough to safely sew the mammary artery onto the coronary artery, completing what is known as a coronary artery bypass. With the use of current technology, up to three bypasses could be performed on a single patient. The bypasses are done only on the front surface of the heart, so this surgical technique is not appropriate for every patient needing coronary bypass surgery. Development is underway to enable surgery on the backside of the heart as well.

Atraumatic Coronary Occlusion

In order to do coronary bypass surgery on the beating heart, the coronary artery to be bypassed must be cut open to prepare it for the bypass. Because arteries are filled with blood under pressure, the blood flow in the coronary artery must be briefly stopped by occluding the coronary artery. The occlusion of flow must be done without damaging the coronary, damage which has been documented in previous studies of these techniques. We have developed several devices and surgical techniques which assist in temporarily stopping the blood flow in the coronary artery, without damaging the artery. The simplest devices are elastic strings that loop around the coronary artery. The technique of placing the loops is as important as the loop itself. Large bites of the cardiac muscle, associated with gentle traction on the loops, is an effective, atraumatic means of temporarily stopping coronary blood flow.

Other devices are under development which will give both atraumatic coronary occlusion and some cardiac stabilization.

Five Millimeter Endoscopy

The endoscope size used for most gynecological and general surgery is the ten millimeter endoscope. The ten millimeter endoscope has been used for many years in thoracic (chest) surgery, but with limited success. The diameter of the endoscope, and the port that is used to introduce it, is so large that the endoscope injures the intercostal nerve, resulting in pain that can be as severe as a thoracotomy (large incision used to get into the chest.) The space between the ribs is so limited that the small space restricts the movement of the endoscope, thereby limiting what the surgeon can see.

We have developed and validated the use of the five millimeter endoscope for thoracic and cardiac surgery. The five millimeter endoscope, and the ports used to introduce it, are very small compared to the space between the ribs, so that there is very little pain associated with the placement and use of the endoscope. The small size of the endoscope makes it easy to maneuver between the ribs, so that the surgeon can see more. In fact, the use of the newly engineered digital camera and digital processing make the picture from the five millimeter endoscope superior to that of the larger ten millimeter scopes. The incisions are so small as to not even require closure, but just a small Band-Aid.

Three Millimeter Instrumentation

Just as the endoscopes of the past were large for the rib space, the instruments to do surgery in the chest were also large. Technology has now taken a leap beyond even the five millimeter endoscopes, and has yielded endoscopic surgical instruments that are only three millimeters in diameter (1/8 inch in diameter.) These instruments are introduced very easily between the ribs.

Not only are the new instruments small, but they are designed for the very fine work that cardiac surgeons do: sewing coronary arteries, sewing heart valves, and removing small arteries and veins for use in bypass surgery. New operations require different hand and finger motions, and a new generation of instruments was required. The new three millimeter instruments are ergonomically designed to feel and work like the standard instruments that cardiac surgeons use, not like the old instruments used by gynecologic and general surgeons, or those formerly used for chest surgery.

The combination of the technologies above has yielded operations that improve results over former techniques, and has led to the development of entirely new operations.

Surgical techniques and operations

Video Assisted Coronary Bypass Surgery

LIMA to the LAD

LIMA to the LAD is an abbreviation for Left Internal Mammary Artery to the Left Anterior Descending Coronary Artery. The purpose of this operation is to attach the left internal mammary artery, (an artery on the inside of the chest wall) to the large artery on the front of the heart, the left anterior descending coronary artery. Previously, the sternum was routinely split, and the patient was placed on the heart lung machine. The hospital stay was typically 4 to 7 days. The patient was usually not allowed to return to work for 6 to 12 weeks. The incidence of stroke was up to 3%, and bleeding up to 10%.

Utilizing minimally invasive techniques, the sternum is not split, and the patient is not placed on the heart lung machine, but the same operation is done. The hospital stay is generally 3 to 4 days, the patient can return to work in 10 days to 2 weeks, (we have seen two days!) the incidence of stroke is minimized, and usually there is very little bleeding. Sometimes a branch of the LAD artery can be bypassed at the same time, yielding a two vessel bypass.

A mirror image operation can be done to the right coronary artery. That is, the right internal mammary artery can be sewn to the right coronary artery, off bypass, without sternotomy.

Selected patients are candidates for these operations. Up to ten percent of patients undergoing coronary bypass may eventually receive this type of surgery.

Endoscopic Repeat Sternotomy

Fifteen to twenty per cent of patients undergoing cardiac surgery are having their second operation. There is a known risk of reoperation, some of the risk being related to re-entering the chest through the same sternotomy incision as the first operation. At the time the sternum is cut the second time, there is risk of injury to the heart, the old bypass vessels, the aorta, and other structures inside the chest.

A new endoscopic device has been developed which makes re-entry into the chest safer, by allowing the surgeon to visualize the structures behind the sternum before the sternum is cut. By being able to see behind the sternum, the surgeon can cut adhesions between the heart and the sternum before he cuts the sternum in two. Releasing the heart from the sternum lowers the risk of injury to the heart.

Endoscopic Pericardiectomy

Fluid can build up around the heart as a result of some disease processes. This fluid can adversely affect heart function. The fluid can usually be drained with a needle. However, sometimes the fluid returns, and the sac around the heart should be surgically removed. Most surgeons remove the sac through a sternotomy, some through an incision on the side of the chest called a thoracotomy. A few surgeons use endoscopic surgery to remove the sac around the heart, but by using large endoscopes, the resulting pain is nearly as severe as a thoracotomy. The development of the 5 millimeter endoscope and 3 millimeter instruments has allowed the sac around the heart to be removed more painlessly than before. There is very little pressure on the nerves between the ribs when the small endoscope is used, so the pain is significantly decreased.

Minimally Invasive Cardiac Operations Requiring Cardiopulmonary Bypass

Mitral valve replacement

The mitral valve is the valve that lies between the upper and lower chambers of the heart, on the heart's left side. This valve is subject to two major problems: being too tight to allow blood to pass through it, or being too leaky and allowing blood to go backwards through the valve.

Surgery on the mitral valve, and any other surgery done inside the heart, requires the use of the heart lung machine to take over for the function of the heart while surgeons are operating inside the heart. That means that mimmally invasive surgery for mitral valve problems would involve smaller sternal incisions than usual, or a different approach to the valve than through the sternum.

In fact, both approaches are now being used. Mitral valve surgery can be done through a three inch incision on the upper sternum, or can be done through an incision on the right chest, near the arm pit. In both cases, the usual surgery on the valve an be performed, and it is believed that the recovery time will be shorter than if a full sternotomy is done. Not enough cases have been done yet to confirm that hypothesis.

Video Assisted Atrial Septal Defect Closure

Some patients are born with a hole between the upper chambers of the heart. The presence of the hole allows blood to mix abnormally inside the heart, and can eventually lead to permanent damage to the heart and lungs if not detected and corrected. The repair of the defect, called an Ostium Secundum Atrial Septal Defect repair, is usually done through a sternotomy, and is a very safe operation. The new approaches to repair of this defect are similar to the approach for mitral valve surgery. Very few have been done, but the results are promising.

Other Cardiac Related Minimally Invasive Operations

Endoscopic Patent Ductus Arteriosus Ligation

All of us have a patent ductus arteriosus when we are developing in the womb. However, the ductus, a connection between the arteries of the lung and the aorta, should close soon after birth. If it does not close, there can eventually be heart failure, or permanent damage to the lungs and the heart. In the past, the treatment to close, or ligate, the ductus, involved a thoracotomy, a sizable incision on the left chest wall. Now the instruments have been developed to close the ductus endoscopically, avoiding the need for a thoracotomy. Again, the use of the 5 millimeter endoscope to see inside the chest decreases the pain of the surgery.

Minimally Invasive Saphenous Vein Harvest

The saphenous vein is the vein in the leg that is removed and used for coronary bypass surgery. Typically, the patient has a very long incision down the inside of the thigh, across the knee, and/or on the lower leg.

The vein can actually be removed from under the skin by making tunnels beneath the skin. The vein can then be dissected out using endoscopy, or by using special lighted retractors that light up the inside of the tunnel. Either way, the incisions are smaller when done this way, and there is less pain associated with the operation.

Summary

In conclusion, new technology is available to surgeons, and therefore to patients, that can significantly reduce the pain and recovery time for selected patients undergoing heart surgery. There are new approaches to old surgery, and there are completely new operations, that have the potential to improve the outcomes of thousands of patients every year. This trend will continue, and will parallel the development of new technology and new ideas applied to old problems.

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