Overview of Cardioplegia
Cardioplegia is a special type of medical treatment given during heart surgery. The purpose is to purposely and temporarily stop the heart’s activity. This technique was first used during a procedure called cardiopulmonary bypass back in the 1950s by Dr. Melrose. He found that high amounts of a substance called potassium citrate could be used to safely stop and then restart the heart.
The way it works is a bit technical. Basically, when potassium enters the heart cell, the cell becomes more neutral (less negative), causing the cell to contract and release calcium ions, leading to the heart stopping in a relaxed state. Normally, heart cells have a negative voltage, around -85 mV. During normal heart activity, sodium ions enter the heart cells, making them more positive and creating a flow of electricity which makes the heart contract. Cardioplegia targets this mechanism to cause the heart to stop.
Over time, the substances in the cardioplegia treatment gradually get washed out of the heart cells, and the heart’s electrical activity starts to return. If necessary, the doctors can give another dose of cardioplegia. Potassium isn’t the only substance used in cardioplegia. Other substances such as calcium, sodium, and magnesium, as well as lidocaine (a local anesthetic), bicarbonate (to balance pH), and even glucose (a type of sugar) may be added to further support and safeguard the heart during surgery.
The main goal of using cardioplegia during cardiopulmonary bypass – a procedure where a machine takes over the functions of the heart and lungs – is to limit the amount of oxygen the heart needs by stopping its activity and cooling it down. This reduces harm to the heart caused by reduced blood supply during the procedure. Benefits of cardioplegia also include providing a bloodless and steady surgical field. There are different types of cardioplegia methods and the substances used, the temperature, and factors like when and how it is administered, side effects, how it is broken down and works in the body can all vary.
Anatomy and Physiology of Cardioplegia
Cardioplegia is a technique used in heart surgery to protect the heart by temporarily stopping or slowing down its activity. It can be administered in two ways – anterograde and retrograde. Anterograde cardioplegia is when the solution is inserted into the aorta, the large artery that supplies oxygenated blood to the body. The special tube used in this method has three channels: one for administering the solution, one for suction, and another one to measure pressure within the tube.
Monitoring of the pressure during this procedure is necessary to prevent potential damage to the blood vessel cells and avoid complications related to high infusion pressures. After the patient is treated with a medication to prevent blood clotting, their body temperature is lowered, and when necessary, they are placed on a machine to take over the functions of the heart and lungs (called a cardiopulmonary bypass). A clamp is placed on the aorta near the tube used for anterograde cardioplegia, and then the solution is carefully administered at set doses and intervals as directed by the heart surgeon.
The term “anterograde” means that the solution flows down the right and left arteries that supply the heart muscle. This mimics the normal flow of blood to the heart. Sometimes, this method may not be enough due to factors like a leaky aortic valve, significant blockages in the heart arteries, prior heart surgery, or damage to the openings of the heart arteries. In such cases, the retrograde cardioplegia approach is used in addition to the anterograde method.
During the retrograde method, the solution is inserted into a large vein of the heart through an opening in the right upper chamber of the heart, and the flow of solution is reversed. A special type of ultrasound scan, known as intraoperative transesophageal echocardiography, is used to ensure that the placement of the tube is correct. However, using only the retrograde method may not always provide sufficient protection to the right lower chamber of the heart. Also, placing the tube in the large vein of the heart has a risk of causing a hole, which, although rare, can cause severe complications and is challenging to repair due to its location at the back. In a specific type of heart surgery, called minimally invasive robotic cardiac surgery, the anesthesiologist places the tube in the large vein of the heart with the guidance of the special ultrasound scan.
Why do People Need Cardioplegia
Cardioplegia is a method used to protect the heart during certain types of heart surgery. It helps to keep the heart safe and still, while also making the surgeon’s work area clear of blood. In many cases, the technique used is called anterograde cardioplegia. However, there’s another technique called retrograde cardioplegia that can be used in certain situations.
Retrograde cardioplegia could be used in the following conditions: serious hardening or narrowing of the arteries (severe coronary artery stenosis), previous heart bypass surgery where the bypass is still working (a patent graft like the internal mammary artery), when there’s an expected long surgery time (like in the repair of the aortic root or valve), or if there’s a moderate to severe backward flow of blood from the aorta into the left ventricle (aortic regurgitation).
If cardioplegia isn’t properly distributed, it could potentially cause damage to the heart cell due to restricted blood flow (ischemia), especially after a procedure where a clamp is applied to the aorta to stop blood flow and cardiopulmonary bypass, which is a technique used to temporarily take over the function of the heart and lungs during surgery, is initiated.
When a Person Should Avoid Cardioplegia
There are different ways a doctor can approach heart surgery, and sometimes the unique structure of a patient’s heart can make it more challenging. In some cases, certain techniques or tools like the anterograde or retrograde cardioplegia catheter (tubes to deliver a special solution to protect the heart during surgery) might be hard to place. Alternatively, an aortic cross-clamp (a tool used to stop blood flow to the heart during surgery) might not be safe to use at all.
For example, if the main artery of the heart (ascending aorta) has a lot of hardening (calcification) or unstable plaques (atheromas), there is a risk of serious complications such as a tear in the aorta (dissection) or a stroke when the aortic cross-clamp is removed. In these cases, the doctor might use different arteries like the subclavian (under the collarbone) or femoral (in the leg) for the cannulation (inserting a tube to deliver or drain fluids).
Also, if the patient’s veins are formed in an unusual way, the doctor needs to assess this before the surgery to ensure the safe use of the coronary sinus cannulation (inserting a tube into the vein that drains blood from the heart). For instance, some people have a persistent left superior vena cava (PLSVC), an extra vein in the chest, which can make the coronary sinus look enlarged on an ultrasound image (TEE). This can make the use of retrograde cardioplegia (putting the protective solution into the heart backwards) unsafe.
There have been cases where a child’s vein leading to the heart (coronary sinus) was closed off (atresia) along with a PLSVC. Usually, these children also have other birth defects and these problems are found when they’re being checked for heart surgery.
Equipment used for Cardioplegia
A ‘cardioplegia cannula’, a type of tube, is needed to deliver a special fluid during heart surgery. It’s also important to have more equipment ready to use. This includes an ‘aortic cross-clamp’, which is a tool to stop the blood flow in the aorta, and other tubes for accessing the arteries and veins. These are essential for starting and maintaining a process known as ‘cardiopulmonary bypass’, which takes over the function of the heart and lungs during the surgery.
There are also monitors that need to be showing information at all times for everyone in the surgery team. This includes the anesthesiologist (who is responsible for pain management and patient unconsciousness), the perfusionist (who operates the heart-lung machine), and the heart and lung surgeon. These monitors show important details like the average pressure of the blood in the arteries, and the pressure inside the tube delivering the special fluid used during the surgery.
Who is needed to perform Cardioplegia?
A perfusionist is a medical professional who plays a crucial role in heart surgeries. Their primary duty is to manage the delicately balanced process of stopping and restarting the heart – also known as cardioplegia. They are in charge of controlling how fast, how much, and at what temperature the special liquid used to stop and restart the heart (cardioplegia solution) is given. The perfusionist needs to adjust these factors throughout the surgery for the best outcome.
During heart surgery, the perfusionist works closely with the heart surgeon before, during, and after the heart has been stopped and restarted. They also monitor and adjust the pressure inside the blood vessels where the cardioplegia solution is being given, making changes as needed.
A special type of anesthesiologist who focuses on heart surgeries also supports the process. They help confirm the correct placement of a tube (the retrograde cardioplegia catheter) that the heart surgeon uses in the procedure. This anesthesiologist also assists in checking the condition of the main artery leaving the heart (the ascending aorta) to make sure it can be safely clamped and cannulated (have a tube inserted) during the surgery.
Preparing for Cardioplegia
When it comes to heart surgery, a key aspect is use of a special kind of solution called cardioplegia. These solutions vary widely from adults to pediatric patients and also from one hospital to another. This is due to the absence of a globally accepted standard method for using these solutions during a heart surgery. Essentially, cardioplegia helps to safely stop the heart during surgery. They need to contain a very specific set of elements, such as potassium chloride and other electrolytes, which help to control heart activity.
Using a cardioplegia solution just once during the procedure is becoming more common, especially for less invasive heart surgeries. Two commonly used one-time solutions are Bretschneider and del Nido. The Bretschneider solution has a variety of components that help maintain the balance of electrolytes and energy production in the heart. The del Nido solution was initially created for newborns and pediatric patients. It contains similar elements to Bretschneider but also includes lidocaine, a medication used to control irregular heart rhythms.
When these solutions were compared, it was found that the del Nido solution had some benefits such as a reduction in certain heart damage markers after surgery and reducing the need for insulin. However, in patients with thickened heart walls or severe narrowing of the heart arteries, the del Nido solution might need to be used more than once due to the risk of inadequate protection.
In high-risk heart surgeries, cardioplegia may need to be given multiple times for better protection of the heart. Such cases usually use other types of cardioplegia solutions which include crystalloid cardioplegia and blood cardioplegia.
Crystalloid cardioplegia helps to reduce injury to the heart during surgery by using a special balance of elements. Blood cardioplegia is a method that uses a combination of blood and a crystalloid solution. It is seen as ideal because it provides natural buffering, better oxygen delivery and carries away harmful substances.
However, there is still much debate in the medical community as to which type of cardioplegia is better or if there’s a certain temperature that provides the most benefit. Basically, there’s no globally accepted standard as of now. What we do know is, for effective heart protection during surgery, the dose of cardioplegia must be carefully calculated and may need to be given multiple times, depending on the length of the procedure and type of cardioplegia used. For newborns and children, the del Nido cardioplegia is given at a specific temperature, and in a certain way depending on the surgery’s duration.
Possible Complications of Cardioplegia
After a heart operation, the use of a specific technique called cardioplegia can lead to several changes in the body that might affect the heart’s recovery. Cardioplegia is a process that temporarily stops the heart during surgery to protect it. However, it can sometimes cause a disturbance in the balance of salts in the body (electrolytes), affect normal heart rhythm, or lead to pH imbalances. These changes can hinder the heart’s function (a condition called myocardial stunning), lead to irregular heartbeats (arrhythmias), or even cause injury to the heart muscle due to lack of blood supply, making it difficult for the patient to be taken off the heart-lung bypass machine after surgery.
Before a patient can be safely disconnected from the heart-lung bypass machine after cardiac surgery, it’s important to ensure that several factors in their blood are within healthy ranges. These includes salts or minerals (electrolytes), body temperature, blood sugar (glucose), pH (a measure of acidity or alkalinity), level of hemoglobin (which carries oxygen in the blood), and hematocrit (the ratio of the volume of red cells to the total volume of blood).
To prevent complications related to cardioplegia, certain steps are taken. This includes regular blood testing during surgery to monitor any abnormalities, and informing the surgeon and anesthesiologist about these so they can act swiftly to treat these issues as they arise.
What Else Should I Know About Cardioplegia?
Cardioplegia is a crucial method used to protect the heart during certain heart surgeries. It involves temporarily stopping the heart and preserving it to prevent damage. This process is critical when the aorta, the main blood vessel in the heart, is clamped off, and a heart-lung machine is used during surgery. It’s important to understand that there are different types, methods of giving, and possible side effects of cardioplegia in order to decrease potential harm and health risks in patients undergoing heart surgery. Not administering cardioplegia correctly could cause damage when normal blood flow and oxygen supply (reperfusion) returns to the heart, and this could result in the heart not getting enough blood (myocardial ischemia).
