Overview of Coronary Artery Bypass Graft Redo
Medical advancements in surgeries that aim to unblock the heart’s arteries, known as percutaneous coronary interventions, have greatly cut down the need for repeat operations to bypass blocked heart arteries (known as coronary artery bypass grafting). However, as people get older, the risk associated with these surgeries also increases. This makes the situation more complex for the surgeon and the team involved. Repeated chest bone (sternum) surgeries raise the risk of death due to the increased chances of damaging the graft – the blood vessel used to bypass a blocked artery – and causing injuries to the heart muscle during the surgery.
Performing surgery to repair or replace the blood vessels supplying the heart (redo coronary revascularisation) poses particular difficulties to heart surgeons. This type of surgery is linked with one of the highest death rates among all repeat heart surgeries, whether performed alone or in combination with surgery to treat other conditions. Therefore, the decision to perform this surgery is weighed carefully, especially when there are no other alternatives. A detailed assessment is essential to precisely understand the heart’s structure, including the status and location of the previously grafted vessels.
In this situation, another hurdle for the surgeon is to ensure the heart muscle’s preservation when there is a functioning (patent) coronary artery graft. During the bypass surgery, the most common method to protect the heart muscle involves diverting blood from the artificial heart-lung machine away from the heart and towards the body. This is done by temporarily blocking the main artery ascending from the heart (aorta). A cold solution rich in potassium is then infused directly into the heart’s arteries to stop the heart from beating and slow down its metabolism.
Yet, the presence of a functioning graft can disrupt this process, as it continuously supplies the heart with normal, warm blood low in potassium. This interferes with the protective effects of stopping the heart and can cause the heart to start beating again – this is not ideal for carrying out the surgery. Therefore, isolating any functioning grafts is vital to the success of a redo coronary artery bypass graft, allowing for a safer procedure.
Anatomy and Physiology of Coronary Artery Bypass Graft Redo
Coronary artery disease is a condition that can get so severe that it needs medical intervention. There are a few ways this can be managed, but two common ones are percutaneous coronary intervention (a procedure that uses a catheter to place a small structure called a stent to open up blood vessels in the heart) or bypass grafting (a surgical procedure used to improve blood flow to the heart).
Our hearts have two main arteries (left and right) that stem from areas called the sinuses of Valsalva. They move along the surfaces of the heart. Typically, the left artery divides into the left anterior descending and circumflex arteries, while the right one continues along the right side of the heart, evolving as a posterior descending artery in about half the people. Understanding this setup is crucial for redo surgery as it helps determine different areas of the heart which are exposed to potential harm due to insufficient blood supply, also known as ischemic heart disease.
During heart bypass grafting, previous grafts (healthy blood vessels taken from other parts of the body) often pass through the pericardial cavity (space around the heart), mainly in the pericardial sinuses, to connect the upper part of the aorta (huge artery coming out of the heart) to the coronary targets. In most cases, the left internal mammary artery (an artery that supplies blood to the chest and abdomen) is used to revascularize (restore blood flow) to the anterior surface of the heart and the wall that separates the heart’s chambers. It’s favored because it remains open and functioning better than other types of grafts. However, it’s also in close proximity to the breastbone (sternum), and this makes it risky during redo sternotomy (repeating the operation where the chest is cut open).
If a patient who has undergone a bypass grafting surgery comes back with signs of heart diseases and effects of restricted blood flow to the heart due to coronary artery disease, multiple diagnostic processes are needed. Coronary angiography (a test that uses dye and special X-rays to see the inside of your coronary arteries), echocardiography (a test that uses sound waves to produce live images of your heart), and in some instances, cardiac MRI (heart imagery using magnetic fields and radio waves) are used to measure the patient’s heart’s capability of contraction, the function of the valves and to determine the advantage of revascularization. If coronary angiography is not recommended, the doctor might use echocardiography with an ECG to monitor the patient’s heart.
Additionally, in patients with heart valve infection, doing a coronary angiography can be high-risk because of potential clot formation during the procedure, as it involves manipulating the catheter (long, thin tube) within the aorta. In these cases, using a CT scan is safer and it also helps to clearly visualize the relationship of the heart structures to the breastbone when planning another surgery.
Why do People Need Coronary Artery Bypass Graft Redo
If a patient has had a previous coronary artery bypass graft (CABG), they might need to consider having a similar procedure or another one called percutaneous coronary intervention (PCI). These treatments help to improve symptoms or lifespan the same way they would in patients with heart disease. The treatment a patient requires depends on how soon they show symptoms after the first procedure.
There’s a chance of graft failure shortly after the patient undergoes a CABG. This complication occurs in about 12% of patients. It can be hard to detect because its symptoms are quite common and aren’t always noticed on scans like ECG and echocardiography.
If the patient shows clear signs and symptoms of ischemia—or inadequate blood flow—a PCI is typically done to limit the effects. Your doctor might consider placing a stent, which is a tube that’s inserted into a blocked passageway to keep it open, in the heart arteries or a graft called the Left Internal Mammary Artery (LIMA). However, a redo CABG might be needed if there’s narrowing or a blood clot at the site of the graft.
The guidelines state that a primary CABG may be needed if the patient has a 50-70% blockade of the left main coronary artery or certain other arteries. It may also be required for patients with heart disease affecting all three major heart arteries, among others. This typically depends on the severity of the patient’s symptoms, their overall heart function, and the results of non-invasive tests.
The considerations for redo CABG at a later stage tend to be similar. But remember, a redo CABG is more complex than the first one, and it carries a higher risk of death. In fact, death rates are generally three to four times higher compared to the primary CABG. However, with improvements in PCI, redo CABGs are becoming less common.
If a patient with a past CABG starts experiencing steady chest pain, doctors usually consider PCI first. This is particularly true if there is a suitable area for this procedure and the patient has a working LIMA graft. Redo CABG might not be recommended if the patient has other severe health conditions, considering its high-risk nature and typically minute or no lifespan benefit.
However, redo CABG might still be necessary if PCI is not possible due to technical issues. For instance, a patient with a new significant narrowing in the left anterior descending artery may benefit from a redo CABG, where a new graft is placed. But if it’s thought redo CABG would be too risky, doctors would normally go for PCI instead.
In general, the decision is best made by a heart team. This team is made up of general cardiology, cardiac surgery, and interventional cardiology professionals. These specialists can review the different treatment options in line with the patient’s overall health and affected areas of the heart. This way, they can determine the best solution for treating the heart disease.
When a Person Should Avoid Coronary Artery Bypass Graft Redo
Sometimes, a surgery might be too risky or not beneficial to a patient. A healthcare team will avoid surgery if it’s possible to use less invasive treatments instead, such as PCI (a procedure that opens blocked arteries). Surgery might also be avoided if a person doesn’t have a long life expectancy, or if the surgery itself is very risky and could lead to the patient’s death.
Generally, a surgery called redo CABG (another heart bypass surgery) isn’t recommended if a person has a severe heart attack and their heart is extensively damaged with no chances of recovery. Patients who have many other health problems and a short life expectancy might also not do better in the long run from this surgery. The healthcare team will typically talk to these patients to decide the best course of treatment, which may not always involve surgery.
Equipment used for Coronary Artery Bypass Graft Redo
The medical team for this procedure includes a surgeon, surgical assistants, an anesthesiologist, nurses and technicians who work in the operating room, and a specialist called a perfusionist who helps with blood circulation for surgeries. In addition to these experts, various specialized tools and equipment are required for a successful operation.
1. Pads used for defibrillation, a treatment that helps restore a normal heart rhythm, are placed on the patient as soon as the operation begins. Because of the nature of this procedure, internal defibrillation pads (usually placed directly on the heart) cannot be used.
2. Blood for transfusion (transfer of blood into a patient’s body) should be prepared and ready, in case it is required during the surgery.
3. Various types of arterial and venous cannulae (tubes used to channel liquid or gas) should be present to allow peripheral access, this is essential to establish Cardiopulmonary Bypass (CBP), a technique that temporarily takes over the function of the heart and lungs during surgery.
4. This procedure involves a secondary (redo) sternotomy, a surgical incision made through the breastbone, using an oscillating saw which helps to cut bone in a safe and controlled manner.
Preparing for Coronary Artery Bypass Graft Redo
Before surgery, patients lie on their back with their whole body exposed from neck to ankle. The choice of blood vessels to use for the surgery is made before anesthesia is applied and it might be necessary to map out the veins in the body to pick the best ones. Normally, a vein in the leg called the saphenous vein would have been used in a previous surgery, but in some cases, a blood vessel from the arm called the radial artery might be needed.
Special pads, called defibrillator pads, are placed on all patients who need to have their chest bone (sternum) reopened. It’s also necessary to prepare the area around the upper thigh (groin) for quick access in case of an emergency.
In preparation for surgery, some doctors might choose to expose or even insert a tube into blood vessels located in the thigh before opening the chest. This is done for two main reasons. The first is to allow for rapid connection to a heart-lung machine, which takes over the work of the heart and lungs during surgery. The second reason is to cool down the patient’s brain and heart, which can help protect them in the event of unexpected bleeding or if the previous surgical grafts are harmed during the operation.
How is Coronary Artery Bypass Graft Redo performed
Two methods for performing a bypass surgery, known as “on-pump” and “off-pump”, have both been found to work well. The choice between these methods depends on how the surgeon needs to access the heart. Even though a redo bypass operation can take longer than the first bypass surgery, a lot of this time is spent getting ready and setting up the equipment for the bypass.
For the initial stage of the operation, most surgeons perform what is called a median sternotomy, which involves cutting through the breastbone. Often, surgeons will use the same scar from a patient’s previous surgery. They also have to remove the wires that were used to hold the breastbone together after the previous surgery, which can sometimes be challenging due to the presence of scar tissue. Unlike with a first-time sternotomy (the cutting of the breastbone), surgeons usually keep the lungs inflated during a redo operation since more time is needed for this step.
Nowadays, surgeons are increasingly using less invasive techniques to do bypass surgery, such as the Minimally-Invasive Direct Coronary Artery Bypass (MIDCAB) techniques. These include procedures that access arteries in the chest and stomach via smaller incisions.
The method of access for the surgery will depend on which vessels need to be bypassed. There are many approaches written about in the field including the on and off-pump methods. Usually, the surgeon makes an incision down the middle of the chest, making sure to not cut into the old scar. Sometimes, they might choose to leave the old wires in place to keep the saw from going too deep. During the opening of the chest, the anesthesiologist may inflate the lungs more than normal, using them as a cushion between the heart and the chest wall.
After opening the chest, surgeons carefully separate any attachments between the heart and the breastbone to release pressure. They pay particular attention to the left side where an older graft may be located. The surgeon will only start using a retractor, a device used to hold the chest open, after the breastbone has been detached from the heart.
Once the chest is safely opened and the heart is free of scar tissue, a blood-thinning medication called heparin is given to the patient. This is done before putting in thin tubes to divert blood away from the heart during the operation.
The surgeon always ensures there’s enough space to safely apply a clamp to the aorta, the large artery leaving the heart. This clamp is used to stop blood flowing to the heart during the operation. They then choose which sites to graft, and perform the bypass surgery using well-known techniques. If there isn’t enough space on the large artery for additional grafts, tubes could be attached in sequence or the shape of a Y. In the final stages of the operation, monitoring wires are attached to the heart, and the process of coming off the heart-lung bypass machine begins. Once the blood thinners have been reversed and the bleeding controlled, the tubes diverting the blood are removed, and the operation is completed as the patient’s blood pressure stabilizes.
Possible Complications of Coronary Artery Bypass Graft Redo
One of the biggest risks of having a second open-heart surgery, or redo CABG (coronary artery bypass graft), is related to reopening the chest, a process called repeat sternotomy. Scaring, scars and sticky tissue that form after the first chest opening, can make it difficult to identify the normal layers and clear structure that were present during the first surgery. This can lead to complications such as damage to the heart itself, the blood vessels attached to the heart, including the previously grafted ones, the large blood vessels, the lungs, and surrounding nerves, especially the phrenic nerve that controls the diaphragm.
Additionally, second-time CABG surgeries are typically associated with longer times on a heart-lung machine (bypass). This is likely due to the more detailed preparation and the need to deal with an area where blood supply has been temporarily cut off (ischemic myocardium). As a result, the body’s defense system might kick in (increased inflammatory response), infection risk might increase and more problems with blood clotting (coagulopathy) might occur. Plus, there might be a more significant need for blood donation during surgery, which can increase the likelihood of adverse reactions to blood transfusion.
Another risk involves the heart surgery itself if previous grafts are present. Dislodging a blood clot during handling of vein grafts can trigger a condition known as intraoperative myocardial infarction, essentially a heart attack during surgery. This complication is more likely with vein grafts because they carry a higher chance of clotting compared to artery grafts.
What Else Should I Know About Coronary Artery Bypass Graft Redo?
Having a second heart bypass surgery, or “redo CABG,” is a big deal for both you and your healthcare team. As our population gets older, more people are likely to need this type of surgery because heart disease usually becomes more complex as we age.
This kind of surgery does carry some risks and potential complications. So, it’s very important for your medical team to carefully check your health beforehand. This usually involves detailed checks and requires the expertise of your surgeon and the whole medical team.
Before the surgery, you’ll likely have special CT scans of your chest and aorta to help your healthcare team plan the procedure. The aorta is the main blood vessel that carries blood from your heart to the rest of your body. This scan helps your surgeon see the state of your blood vessels and set up the best path for heart-lung bypass, a machine that temporarily does the work of your heart and lungs during surgery.
Your surgeon will share their strategy for your surgery with the whole medical team. This might include plans to handle any problems during the administration of anesthesia or exposure of the femoral vessels (large blood vessels in your legs) for emergency use if needed, deciding the correct tools to use during the surgery, and figuring out the number and type of grafts (replacement blood vessels) needed for your heart.
Even though these plans are a regular part of any heart surgery, having a clear strategy for complex cases like a second bypass surgery gives your medical team the confidence they need to handle any complications that may occur. Your safety and well-being are their number one priority.
