Aortic Valve Replacement/ Mitral Valve Replacement (AVR/MVR)
There are four types of cardiac valves that control the flow of blood to and fro the heart. Over a period of time, the heart valves may get diseased or damaged because of several reasons. A reduction in the functioning of the valves can cause serious complications.
The aortic and the mitral valve are most commonly affected by the heart valve disease. Aortic valve replacement (AVR) and mitral valve replacement (MVR) are the two types of valve replacement surgeries in which the diseased aortic or the mitral valve are replaced. Sometimes, both the valves are replaced in the same surgery. Such a surgery is known as double valve replacement surgery.
Types of Valves
The following types of valves may be used to replace the diseased or damage valve:
Tissue valves: These valves are created from animal tissue, wither heart valve tissue or pericardial tissue. These types of tissue valves reduce the risk of rejection and calcification. In some of the cases, a homograft may be used to replace the diseased valve. The homograft is either retrieved from a deceased donor or the patient’s own pulmonary valve.
Mechanical valves: These are made up of flexible and durable material and they tend to last for an entire lifetime of the patient. However, there is an increased risk of blood clotting in patients who receive mechanical valves. This is the reason why they may have to take blood-thinners for their entire life.
Immediately after the procedure, the patient is shifted to intensive care for at least 12 to 36 hours. This is followed by a day or two of hospital stay. The patient is discharged after four to six days of the surgery. Total recovery may take around four to six months.
There are four types of valves in the human heart – the mitral, aortic, tricuspid, and pulmonary valve. The mitral and the tricuspid valve are present between the upper and the lower chambers of the heart. On the other hand, the aortic and the pulmonary valve are present in the two arteries that leave the heart.
Most often, it is the mitral and the aortic valve that undergoes certain pathologic changes due to degenerative valve diseases, rheumatic heart diseases, or infective endocarditis. This may result in problems associated with the valve opening and closure.
These dysfunctions can be treated with either valve repair or valve replacement surgery. Aortic valve replacement or mitral valve replacement is carried out when just one of the valve is diseased or damaged. However, when both the valves are diseased or damaged, a double valve replacement surgery is conducted.
The heart valves present in the heart are responsible for permitting the flow of nutrient-laden blood through the heart chambers. After allowing the ushering of blood, each valve is expected to close completely. The diseased or damaged valves are not able to open and close properly, thus allowing the mixing and backflow of blood (regurgitation).
A double valve replacement surgery mainly aims at correcting the problem of valvular heart disease and involves both aortic valve replacement and mitral valve replacement. The mitral valve is situated between the left atrium and the left ventricle while the aortic valve is located in between the aorta and the left ventricle.
Some of the causes of heart valve disease include the following:
Some of the symptoms of valvular heart disease include the following:
Double valve replacement surgery is a complicated procedure as compared to single valve replacement surgery. Aortic valve replacement and mitral valve replacement involves the replacement of just one valve but during double valve replacement surgery, both the diseased valves are removed at the same time and replaced with a synthetic (mechanical) or a biological valve.
In the case of mechanical valves, the components used are not of organic or natural origin. They are created from a combination of polyester and carbon material that the human body can tolerate and accept. Blood-thinning medications are given to patients who get mechanical valves to prevent blood clot formation.
Bioprosthetic valves or the biologic valves are either created from animal or human tissues and can be of the following types:
The choice of a particular type of valve depends on the age, overall fitness, and the ability to metabolize anticoagulant medications. The only problem associated with a bioprosthetic valve is that it may not last a lifetime and one may have to undergo a replacement again later.
For the purpose of hemodynamic monitoring, the peripheral arterial and venous access are installed. The patient is anaesthetized in a supine position with a single lumen endotracheal tube.
In the jugular vein, two percutaneous sheath introducers are placed for central venous pressure monitoring and drug administration. Another similar one is placed in the same right jugular vein for the purpose of introducing endocavitary pacemaker leads if required. External defibrillator pads are placed on the patient’s back and on the anterior left chest.
TEE or transesophageal echocardiography probe is used for an assessment of cardiac function, percutaneous venous cannulation guidance, and valve assessment. The skin is sterilized with iodine solution and an aseptic strip is applied on areas exposed. The double valve replacement procedure is very similar to isolated aortic valve replacement or mitral valve replacement, which is conducted via a single access right anterolateral minithoracotomy.
Before systemic heparinization, the venous introducer sheath is positioned in the femoral vein to prevent any unwanted bleeding. In the third intercostal space, an incision of 6 to 8 cms is made. Minithoractomy is made and in the 3rd and 5th intercostals spaces, two auxiliary working ports are placed. The first is for video assistance and the second is for gas insufflation, cardiotomy vent, and pericardial stay sutures. The pericardium is opened upwards and downwards after removal of the pericardial fat, which is 3 to 4 cm above the phrenic nerve. The pericardium is retracted using silk sutures.
In a standard way, two aortic purse strings are placed for direct arterial cannulation after the aorta has been exposed. The operation is continued with venous cannulation under the guidance of TEE. A guidewire in moved through the venous introducer and positioned in the superior vena cava.
With the central cannulation of the ascending aorta, arterial inflow is established. The cannula has an obturator and an advanced tip to aid aortic insertion within the thorax. With cannula rings, the tip is secured and with two tourniquets the cannula is secured. They allow maximum space to work during thoracotomy access.
Carbon dioxide flow keeps running and when the heart gets arrested, the aorta is opened in an oblique way with an incision like a hockey stick, k which is further extended to the non-coronary sinus Valsalva. After this, aortotomy is made far away from the cross-clamp and from the main pulmonary artery trunk; for the closure of aortotomy, enough aortic tissue must be kept. Now the problematic valve is excised. The annulus size is measured and calibrated with a sizer and then prosthesis is implanted. The aortic prosthesis is lowered and made to remain above the final plane of implantation.
Now focus shifts to the left atrium. It gets dissected in a Sondergaard’s plane, and with the help of one single silk suspension stitch and an atrial retractor, the mitral valve is exposed. If now required the left atriotomy can be further extended behind upwardly behind the superior vena cava or along the inferior vena cava downwardly. In right minithoracotomy the visualization of the mitral valve is very good and allows valve and subvalvular repairs easily.
The procedure starts with synthetic braided sutures being placed in the mitral annulus whose diameters are measured using suitable valve sizes. For the mitral valve, reductive annuloplasty is performed. The sutures are passed and the retractor is removed and then attention is again diverted towards the aortic valve prosthesis. This is lowered into the annular plane and thereafter knotted.
For the assessment of the results of the repair, the atrial retractor is again positioned in the left atrium. To estimate the competence of the valve, a water probe is applied with an implanted open mitral ring. After successful completion, the left atrium is closed leaving behind the ventricular vent via the mitral valve in the left ventricle. Aortic cross-clamp is removed and aortotomy suture is further knotted. The aortic vent is positioned in the ascending aorta. A polypropylene purse-string suture is hand-knotted after aortic vent is removed. After confirmation by the TEE, the procedure moves to the final stage where the aortic cannula is removed and a percutaneous cannula is also withdrawn with the femoral vein temporarily placed under compression, the skin incision is closed with a single silk stitch.
After the surgery, the patient is shifted to ICU for close monitoring for several days. Blood pressure, ECG tracing, breathing rate, and oxygen levels are closely studied. You may require staying in the hospital for several days after heart valve replacement surgery. With the help of the ventilator, breathing is assisted via a tube inserted in the throat. The breathing machine will be further adjusted as the patient keeps growing stable and once the patient is able to breathe and cough on their own, the tube is removed. Along with this, the stomach tube is also removed.
In every two hours, a nurse would help the patient take deep breaths and cough. This feels sore but is vital to prevent accumulation of mucus in the lungs and prevent pneumonia. The patient is taught to hug a pillow tightly while coughing to ease out any discomfort. The patient must express discomfort felt at coughing and medications are suggested accordingly. Slowly fluid intake is initiated and you can gradually increase your daily activities such as walking around the room. After a few days, the patient is shifted to the recovery room where the rest of the recovery takes place before discharge.
Notify your doctor if you feel swelling and redness around incision area, fevers and chills, or pain in the area of the incision. You should rest and keep the surgical area as clean as possible at home.
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