Minimally invasive direct coronary artery bypass (MIDCAB) is a minimally invasive version of the traditional coronary artery bypass graft (CABG). Like CABG, MIDCAB creates a detour for blood to flow around a blocked coronary artery. Unlike conventional CABG surgery, however, the patient’s chest is not fully opened. Instead, the surgeon works through a smaller incision in the side of the chest. MIDCAB surgery may be performed with or without the use of the heart-lung machine.
MIDCAB surgery is used to treat the symptoms of coronary artery disease. By bypassing blockages in diseased coronary arteries, surgeons are able to reestablish blood flow to the heart. This will relieve such symptoms as angina (chest pain, pressure or discomfort) and lower the risk of heart attack or other potentially fatal events.
MIDCAB was developed as a less-invasive approach toward bypass surgery. Because a smaller incision is used, patients recover more quickly, with less trauma and lost time as compared to conventional CABG. Recovery time after MIDCAB is comparable to the recovery time after balloon angioplasty (3 to 7 days) versus the two weeks that are common after conventional CABG. Within two weeks, many MIDCAB patients can return to normal activities.
However, there are a number of drawbacks to MIDCAB. Because the surgeon is working through a smaller incision, the technique is only available for coronary artery disease that occurs in one artery. Multi-vessel disease cannot usually be treated with MIDCAB alone. This shortcoming has been addressed to some extent by the development of hybrid techniques that use MIDCAB surgery in conjunction with balloon angioplasty. In addition, MIDCAB is more technically demanding.
About MIDCAB
MIDCAB (minimally invasive direct coronary artery bypass) surgery was developed as a less-invasive alternative to conventional coronary artery bypass graft (CABG). During a conventional CABG, the surgeon “cracks” the patient’s chest by making an incision through the breastbone and spreading the ribs. This gives the surgeon excellent access to the heart, but it results in a long recovery for the patient. Also, the incision is more prone to infection and other complications.
MIDCAB addresses these concerns by using a smaller incision in the side of the chest. Working through this smaller incision, the surgeon is able to sew bypass grafts onto diseased coronary arteries. This technique reestablishes blood flow to the heart with much less trauma to the patient and a reduced risk of infection at the site of the surgical wound. On average, patients who undergo MIDCAB may be released from the hospital within 3 to 7 days and can often return to normal activities within two weeks. By contrast, patients undergoing CABG often spend two weeks in the hospital and several months in recovery.
MIDCAB surgery may be performed with or without use of the heart-lung machine. If it is performed with the heart–lung machine, the surgeon stops the heart through use of cardioplegia solution, then uses a special system of clamps and shunts to redirect blood flow around the heart. This may be called port access surgery, after the device that is used to reroute blood flow. This technique gives the surgeon the ability to work on a still, empty heart, which increases the level of control over the operation.
If the surgery is performed without the heart-lung machine, the surgeon uses a special system of clamps and stabilizers to hold the heart still while the bypass grafts are sewn into place.
MIDCAB is used to treat the symptoms of coronary artery disease, including angina(chest pain and pressure). By reestablishing blood flow to the heart, the risk of heart attack is also reduced. Compared to conventional CABG, MIDCAB has a number of advantages and disadvantages. It offers the following advantages:
It is less costly.
The risk of serious complications, including infection, can be minimized because of the smaller incision.
It does not require the trauma of “cracking the sternum” and opening the entire chest. Because much smaller surgical incisions are used, there is less pain and trauma to the patient.
It usually requires a shorter operation, hospital stay and recovery period.
There are also some limitations to the MIDCAB:
MIDCAB techniques can only be used in a very small subset of patients. To date, MIDCAB has been performed only in either very high-risk patients who could not withstand balloon angioplasty or conventional CABG, or very low-risk patients whose coronary artery disease was limited to the left anterior descending coronary artery (LAD), which lies on the front of the heart. In some cases, MIDCAB can be used on the right coronary artery or for multiple bypasses, but these procedures are far less common.
Several studies have noted that MIDCAB may not be as effective over the long term as the standard CABG. Follow-up data revealed that patients who had undergone MIDCAB were more likely to have blockages in their new grafts than patients who had undergone CABG. It must be noted when interpreting this data that MIDCAB requires greater skill of the surgeon, and these studies were done when MIDCAB was still a new technique.
Difficulty in accessing the LAD or an inability to use the mammary artery as the graft may disqualify the use of this procedure in some patients.
Efforts have been made to address MIDCAB’s main limitation, which is its limited usefulness in patients with multiple vessel disease. In some cases, it has been used successfully in conjunction with a catheter-based procedure such as balloon angioplasty. In this case, disease of the LAD will be corrected with a MIDCAB graft, while blockages in other arteries may be treated with balloon angioplasty and stenting. Results for these hybrid procedures are comparable to classic CABG for multi-vessel disease.
Not all surgeons are qualified to perform minimally invasive techniques, which require greater skill and experience. Patients interested in determining their eligibility for these techniques and/or finding a qualified surgeon to perform the surgery may wish to seek a second opinion.
Before the MIDCAB procedure
Patients should prepare in advance for a hospital stay of about three days. The patient is usually admitted on the scheduled date of the minimally invasive direct coronary artery bypass (MIDCAB). In the hospital, the patient will undergo a pre-operative assessment that includes:
Urine and blood tests. These are done to ensure that the patient is in good overall health for undergoing surgery. Blood tests to assess blood clotting (coagulation tests) include an INR or prothrombin time (PT), partial thromboplastin time (PTT), bleeding and clotting times, and a platelet count.
Electrocardiogram (EKG). A recording of the heart’s electrical activity as a graph on a moving strip of paper or video monitor.
Echocardiogram. This test uses sound waves to visualize the structures and functions of the heart. A moving image of the patient’s beating heart is played on a video screen, where a physician can study and measure the heart’s thickness, size and function. The image also shows the motion pattern and structure of the four heart valves, revealing any potential leakage (regurgitation) or narrowing (stenosis).
Chest x-ray. A radiation-based imaging test that offers the physician a picture of the general size, shape, and structure of the heart and lungs.
Eight hours before surgery, all patients are placed on NPO (non per os; nothing by mouth) status. That means that they are not permitted to eat, drink or take anything by mouth until after their surgery. Smokers will have been instructed to completely avoid smoking for at least two weeks before their surgery to prevent problems in breathing, reduce secretions and facilitate necessary coughing. Certain medications may need to be reduced or stopped temporarily, so patients should discuss their medication schedules with their cardiologist before surgery.
Immediately before surgery, the patient will be given specific pre-operative medications and then “prepped” for surgery. First, the chest area is shaved. Next, the surgical team creates a sterile environment by swabbing the patient’s chest with an antiseptic solution and covering the operative area with sterile surgical drapes. An intravenous (I.V.) line will also be started, usually in the forearm or back of the hand.
The patient is then given a sleep-inducing medication through the I.V. line. Once asleep, the patient will continue to breathe a mixture of oxygen and anesthetic gas (general anesthesia) to make sure that he or she remains asleep throughout the entire surgery.
During the MIDCAB procedure
After the patient is asleep, a device called the Swan-Ganz catheter is often inserted into the jugular vein (in the neck) and threaded to the pulmonary artery (which goes from the heart to the lungs). The catheter can be used to give medication, to measure the oxygen levels in the blood and to measure pressures in the heart. A breathing tube (endotracheal tube) will also be inserted into the mouth and down the windpipe (trachea) to maintain an airway.
The surgeon will then make an incision about 4 to 6 inches long on the left side of the chest. Through this incision, the surgeon can identify the mammary artery (also known as the internal thoracic artery), which will be used for the graft. The artery is located and part of it is retrieved for use (harvested). If the surgeon finds the mammary artery to be unusable for this purpose, or if other complications are revealed (e.g., the LAD shows severe calcification), then the surgeon may proceed with a standard bypass surgery from that point.
Whether the heart is stopped or not depends on the particular patient and the surgeon. If the heart is stopped, a cardioplegia solution is administered and special incisions (ports) are made to accommodate the port access system. The ports are held open during surgery with 1.5-centimeter (1-inch) tubes that provide a workspace for tools and scopes to access the heart and coronary arteries. A catheter is inserted through the groin and fed through the femoral vein and/or femoral artery to assist with the diversion of the blood flow to the heart-lung machine. During the surgery, the heart is still and empty of blood. This enables the surgeon to reach more of the heart than during a “beating heart” surgery.
If the heart is not stopped, specialized clamps and stabilizers are used to hold the heart in place. To prevent ischemia, or lack of blood flow to the heart, a temporary shunt is put in place. Once this has been accomplished, blood flow to the left anterior descending artery (LAD) is temporarily clamped off. The mammary artery is then attached directly to the LAD beyond the blockage.
Once the procedure is finished, blood can flow freely through the LAD beyond the blockage, restoring blood flow to the heart muscle. When the surgeon is satisfied that complete blood circulation has been restored to the heart, the chest incisions are closed (sutured). The procedure takes approximately two hours.
After the MIDCAB procedure
Following the minimally invasive direct coronary artery bypass (MIDCAB), the patient will spend some time in the recovery room, where simple exercises will be performed to restore normal breathing, circulation and movement. Heart and blood flow will be continuously monitored. Within 24 hours, the patient will be transferred to a regular hospital room. Routine medications and additional pain medications may be administered and food will be given as tolerated by the patient.
An average hospital stay after a MIDCAB procedure is approximately three days. After discharge, patients are encouraged to engage in light exercise, such as walking. Strenuous exercise is discouraged.
Benefits and risks of the MIDCAB procedure
Clinical tests have shown that minimally invasive direct coronary artery bypass (MIDCAB) is a highly successful procedure with a lower risk of serious complications than a conventional bypass surgery. A successful MIDCAB will result in the resumption of normal blood flow through the left anterior descending coronary artery (LAD). A segment of the LAD will still be blocked, but the blood will be able to flow freely through the detour and around the damaged area via the newly grafted mammary artery. However, it is worth noting that observational studies comparing MIDCAB have not been long-term. These are ongoing.
Lifestyle considerations following MIDCAB
After undergoing a minimally invasive direct coronary artery bypass (MIDCAB), patients are strongly encouraged to make lifestyle changes that can prolong the effectiveness of the procedure as well as the patient’s overall health. These changes include:
Eating a heart-healthy diet. Modern research has consistently supported the idea that health is largely determined by what people choose to eat. While certain vitamins and minerals have been shown to be helpful to heart health, fats and oils such as saturated fat, trans fats and tropical oils (palm and coconut oil) have been shown to be particularly harmful because they can speed up the development of coronary artery disease (CAD), atherosclerosis and obesity.
Improving your cholesterol ratio. A person’s total cholesterol ratio (which includes LDL cholesterol, HDL cholesterol and triglycerides) should be no more than 200 milligrams per deciliter and no more than five times the HDL level. Key strategies for reducing levels of total cholesterol, LDL cholesterol and triglycerides are to eat a heart-healthy diet and to exercise regularly. If these strategies do not reduce total cholesterol levels, a physician may prescribe cholesterol-reducing drugs. Strategies for increasing levels of HDL cholesterol include eating monounsaturated fats in moderation, decreasing the amount of saturated fat, limiting alcohol use and starting an exercise program.
Controlling homocysteine levels. Homocysteine is an amino acid produced as a normal byproduct of meat metabolism. High homocysteine levels have been linked to damage of the arteries, which may increase the risk of heart attack, stroke or other cardiovascular problems. Researchers are currently trying to determine whether high homocysteine levels are an actual cause of those conditions, or are simply associated with them for some other reason. The American Heart Association recommends testing homocysteine blood levels in patients with known risk factors for heart disease (e.g., a family history of heart disease). Homocysteine can be kept at moderate, healthy levels if the body has adequate levels of three important B-vitamins: vitamin B-6, vitamin B-12 and folic acid (the synthetic and more easily absorbed version of folate). Therefore people are encouraged to make sure they get enough B-vitamins every day.
Managing your stress. Stress can lead to overeating, smoking, high blood pressure (hypertension) and a failure to exercise. In addition, chronic stress may be a direct contributor to poor heart health because it produces increases in blood pressure that could become permanent.
Quitting smoking (or not starting to smoke). Tobacco smoking is a major cause of coronary artery disease and cardiac arrest. A 1990 study by the Centers for Disease Control and Prevention (CDC) shows heart disease as the leading smoking-related cause of death in the United States among men and women. The CDC also suggests that the average smoker dies nearly seven years before a nonsmoker.
Maintaining a regular program of exercise. Exercise can be an excellent tool in both the prevention of heart disease and improving quality of life for heart patients. Physically, it can slow or even reverse the process of atherosclerosis, as well as lower blood pressure and reduce cholesterol levels. Emotionally, it can reduce levels of stress and depression. The increased risk from not exercising has been compared to the risk from smoking a pack of cigarettes per day.
Controlling diabetes. Persons with diabetes are more likely to develop heart-related diseases. Preventative care and a balanced diet are crucial to the overall health and heart function of diabetic patients.
Controlling high blood pressure (hypertension). Individuals with high blood pressure are at greater risk of cardiovascular problems resulting from CAD. This is because a buildup of plaque in the arteries can lead to an even greater increase in blood pressure in the damaged areas of those arteries. Hypertension can be controlled through blood pressure medications, self-monitoring, eating a heart-healthy, low-salt diet and engaging in regular exercise. People are also encouraged to have regular check-ups with their physician.
Controlling weight. obesity and being overweight are major risk factors for a host of serious health conditions, including coronary artery disease, high blood pressure, diabetes, heart attack and stroke. Some weight control methods include limiting fat in a patient’s diet, increase activity levels, counseling, medication and surgical interventions.
Controlling chronic depression. Depression has been linked with a higher risk of developing high blood pressure, heart disease and having a heart attack.
Variations of the MIDCAB procedure
A variant of the minimally invasive direct coronary artery bypass (MIDCAB) is the use of robotic visualization techniques. This strategy involves a voice-activated robot at the operating table and a cardiac surgeon one room away. The hand motions of the surgeon are processed and digitized from the controls to a computer. The computer, in turn, directs the robot where to cut and sew inside the chest. The surgeon directing the operation can view the procedure via an endoscope (a slim optical tube with an attached camera that is positioned inside the chest cavity).
The advantage of using a robot is that the “hands” are smaller than human hands and require a much smaller incision. These techniques are reported to be safe and reliable, causing less pain to the patient, less surgical trauma and a shortened recovery time. Tele-robotic heart surgery is still in the embryonic stage and is only available in limited centers worldwide.
Other minimally invasive methods of coronary artery bypass are continually being explored. A recent study reported the success of the first non-surgical bypass operation in Germany. Named percutaneous in situ coronary venous arterialization (PICVA), the procedure basically redirects blood flow around a blocked artery by diverting it to an adjacent vein. An ultrasound catheter system guides a needle into the blocked artery and through the artery wall into a nearby vein. This creates a channel into the vein, redirecting the flow of blood around the blockage. The procedure had been performed in 1999 on a patient with severe chest pain and coronary artery disease who was not a candidate for traditional bypass surgery or balloon angioplasty. A year after the procedure, the patient was still free of heart-related chest pain. Further studies are needed to determine the safety and long-term effectiveness of this procedure.
Questions for your doctor
Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their treatment options. The following questions related to minimally invasive direct coronary artery bypass (MIDCAB) surgery may be helpful:
Am I a candidate for the MIDCAB procedure?
Am I better off undergoing a MIDCAB procedure or a coronary artery bypass graft?
Why do you recommend the MIDCAB procedure for someone in my condition?
What sorts of risks will I be exposed to during the MIDCAB procedure?
How long will my recovery be?
Will I need to stay in the hospital following the surgery? For how long?
Are there any medications that I am currently taking that could interfere with the surgery?
Will I need to take any medications prior to the surgery? Could any of these interfere with my current medications?
What sort of results can I expect from this surgery? Will the surgery impact my day-to-day life in any way?
Can I still undergo this procedure if I am pregnant?
