Overview of Aortic Stenosis
Globally, 3% of elderly patients, aged 65 and above are affected by Aortic Stenosis, according to one of the article by Mayo clinic. It is one of the most significant valvular heart disease across the globe. Its mechanism of occurrence includes similar as in atherosclerosis, including lipid and calcium deposition and inflammation. The development of significant Aortic Stenosis inclines to earlier occurrence in individuals with congenital bicuspid aortic valves and in patients suffering from disorders of calcium metabolism, such as kidney failure. Survival in Aortic Stenosis patients decreases rapidly after symptoms appear.
Causes of Aortic Stenosis
A) Genetic Defects in Valves
The aortic valve normally comprises of 3 flaps of tissues. However, some individuals are born with an aortic valve comprising of only one or two flaps. Such a condition may lead to problems such as leaking or narrowing of valve in adulthood
B) Hardening or Calcium Deposition on Valve
Aortic Stenosis occurs when your aortic valve of the heart becomes narrow as a result of fat and/or calcium deposition due to which it cannot open entirely, reducing or blocking flow of blood from the heart to other organs of the body. As the blood flow gets reduced, your heart has to work with more power to provide blood to the body. This extra effort gradually restricts the efficiency of the heart, leading to symptoms of valvular heart disease and eventually weakens your heart.
Aortic Stenosis is a product of an inflammatory process caused by damage to the inner lining of the blood vessels (endothelium), lipid penetration causing fibrosis, thickening of valve leaflets and ultimately, calcium deposition. Calcific Aortic Stenosis causes elevated leaflet stiffness and narrows the orifice of the aortic valve orifice, resulting in a pressure difference across the valve. Aortic Stenosis consists of an extended subclinical period, where calcium build-up does occur on the valve, but there is absence of pressure difference across the valve.
Worsening aortic valve narrowing and subsequent loss of efficiency of heart’s left chamber lead to the characteristic triad of Aortic Stenosis symptoms: heart failure, fainting and chest pain.
C) Certain Infections
A complication of simple throat infection, known as rheumatic fever may lead to formation of scar tissue on the aortic valve, narrowing the valve and result in Aortic Stenosis. Formation of scar tissue may also serve as a centre for calcium deposition, contributing to worsening of Aortic Stenosis.
This risk factor is more prevalent in developing countries like India.
Risk Factors for Aortic Stenosis
- Advanced age (> 70 years)
- Congenital defects of the heart
- Certain infections
- Co-morbidities like diabetes, high blood pressure, high cholesterol or chronic kidney disease
- Prior radiation therapy in the chest region
Symptoms of Aortic Stenosis
Symptoms of Aortic Stenosis range from mild to severe forms. Signs and symptoms of Aortic Stenosis normally develop at a stage of severe narrowing of the valve. Some people with Aortic Stenosis may not experience symptoms for several years. Signs and symptoms of aortic valve stenosis may include:
- Abnormal heart sound (heart murmur) evident through a stethoscope exam
- Chest pain or tightness in chest upon activity
- Dizziness or fainting upon heavy exertion
- Shortness of breath (dyspnea), especially upon activity for prolonged intervals
- Feeling of a rapid, fluttering heartbeat
- Reduced hunger, especially evident in children
- Reduced body weight (mainly in children)
The heart-weakening effects of Aortic Stenosis may cause heart failure leading to related symptoms including fatigue, dyspnea, and swelling in the ankles and feet.
Diagnosis of Aortic Stenosis
The doctor may advise a number of following tests to detect the presence of Aortic Stenosis or determine its stage.
This test uses sound waves to produce series of X-ray images of your heart during activity. Doctors may utilize this test to assess your heart chambers, the aortic valve and the flow of blood through your heart’s chambers. A doctor usually uses this test to identify your condition a heart valve condition is suspected in your case.
This evaluation can help doctors thoroughly observe the condition of the aortic valve, and detect the presence of causative risk factors and severity of your condition. It can also aid doctors define whether you have other heart valve conditions.
Doctors may conduct another type of echocardiogram called a transesophageal echocardiogram to get a closer look at the aortic valve. In this test, a small transducer attached to the end of a tube is inserted down the tube leading from your mouth to your stomach (esophagus).
B) Electrocardiogram or ECG
In this examination, wires attached to pads on your skin quantify the electrical activity of your heart. An ECG can identify enlarged chambers of your heart, heart disease or abnormal rhythm of the heart.
C) X-ray of the chest
A chest X-ray can benefit your doctor to decide if your heart is enlarged, which happens in Aortic Stenosis. It can also demonstrate if your blood vessels are enlarged (especially the aorta) or any deposits of calcium on your aortic valve. A chest X-ray can also aid in determining the condition of your lungs.
D) Exercise tests or stress tests
Exercise tests help doctors understand if you demonstrate signs and symptoms of aortic valve disease during exercise, which can help to conclude the severity of your condition. Medications that produce results resembling exercise on your heart may be used in case you are unable to exercise due to any reason.
E) Cardiac computerized tomography (CT) scan
A CT scan uses a series of X-rays to generate comprehensive images of your heart and heart valves. Doctors may use this test to measure your aorta’s size and study your aortic valve more thoroughly.
F) Cardiac MRI
A cardiac MRI uses magnetic fields and radio waves to produce in depth images of your heart. This test may be used to decide the severity of your condition and estimate your aorta’s size.
G) Cardiac catheterization
This test is not routinely used to diagnose Aortic Stenosis, but it may be used if other tests are unable to clearly define the underlying condition or to determine its severity. In this procedure, your doctor passes a thin tube (catheter) through a blood vessel in your arm or groin and guides it to an artery in your heart. Doctors may also insert a dye through the catheter, which aids to visualize your arteries on an X-ray, providing your doctor with a complete image of your arteries of the heart arteries and the working of your heart. It can also quantify the pressure inside your chambers of the heart.
Treatment of Aortic Stenosis
Current strategy for treating Aortic Stenosis rests on how severe the patient’s condition is and whether he/she is suffering from any symptoms or his/her condition is progressive in nature. Contemporary treatment options for Aortic Stenosis includes watchful waiting, balloon valvuloplasty, surgical aortic valve replacement or transcatheter aortic valve replacement.
If you are asymptomatic or are feeling mild symptoms, your doctor may simply recommend regular monitoring of your condition through periodic follow-ups. He/she may advise you to make some healthy modifications in your routine (heart-healthy diet, regular exercise, weight control, reducing stress and avoiding tobacco consumption) and prescribe some medications to prevent complications or worsening of present condition). Medicines can be of help only if the disease is diagnosed in initial stages without any major visible symptoms.
However, sooner or later, Aortic Stenosis treatment does require surgical intervention in majority of cases. A surgery for Aortic Stenosis treatment can be of various types, depending on each patient’s unique requirements and factors responsible for their condition. Two of such major surgical treatment options for Aortic Stenosis treatment include aortic valve replacement and balloon or surgical valvuloplasty.
Surgical options for treating Aortic stenosis include:
A) Aortic Valve Repair
In routine practice, an aortic valve repair is not preferred for Aortic Stenosis. On rare occasions, surgeons may repair a diseased aortic valve through separation of fused valve flaps.
B) Balloon Valvuloplasty
Though, it can treat Aortic Stenosis in infants and pediatric patients, balloon valvuloplasty is just a temporary solution to manage Aortic Stenosis, as the valve gets narrowed again after the procedure in adults. Hence, it is normally performed in elderly patients who are awaiting surgical valve replacement or those who are very ill. The interventionalists carry out the procedure by using a catheter containing a balloon and threads the apparatus to the aortic valve. As the balloon reaches the narrowed valve, the doctor inflates the balloon, expanding the orifice of the aortic valve. Then, the balloon and catheter are removed from the patient’s body.
C) Surgical Aortic Valve Replacement (SAVR)
Traditional SAVR procedures are performed by an open heart surgery, exposing the chest bones through an elongated incision across the chest. Once, the heart is exposed, the surgeon will replace the diseased aortic valve with an artificial mechanical or tissue valve. Since, this procedure is a major procedure; it is associated with a significant risk for complications like Infection, stroke, blood clots or irregular heartbeats.
D) Transcatheter Aortic Valve Replacement
TAVR or Transcatheter Aortic Valve Replacement is a minimally invasive surgery to replace your aortic valve in the heart which has become inefficient due to diseases such as aortic stenosis. A TAVR can be performed by making small openings leaving all the bones of the chest intact contrary to the surgical aortic valve replacement (SAVR), which involves an open heart surgery. In an open heart surgery, the chest is separated surgically to replace the valve. TAVR valves are exclusively designed to be implanted using a long, narrow tube (catheter). The catheter could be threaded through any of the routes as stated below: 1) Via the femoral artery (large artery present in the groin). 2) Via a large artery in the chest (Transapical). The valve is made of a natural tissue from the heart of either a cow or pig. The natural tissue is re-treated and attached to a flexible balloon-expandable or self-expanding frame. For inserting the catheter into the femoral artery (the most commonly used route), surgeon will make an incision in your groin area to locate the femoral artery which carries blood from the heart down into the leg. He/she will place a catheter into that artery and thread it to your heart and through the aorta, to reach your aortic valve. TAVR places a new artificial valve in place of the inefficient/diseased native aortic valve. Initially, it is positioned on a tube with a balloon tip at one end, and is then crimped to an extent which fits through a hollow tube which is priorly placed in a cut on your leg. As soon as the tube gets inserted and reaches the native diseased valve, the balloon is inflated and in turn, the new valve gets expanded and takes its place. It pushes the leaflets of the original valve and secures itself into its place. After confirming the proper working of the new valve, the balloon is removed after deflating it. The surgeon will also place other catheters in the heart to take measurements and X-ray pictures during the procedure.