TAVR or TAVI refers to a procedure where an artificial bio-prosthetic valve is implanted into the human heart using a catheter in a suture-less fashion.
To read about heart valves, click here
To read about Aortic Stenosis, click here
Trans-catheter Heart Valve (THV) is an artificial valve made from the outer covering of animal hearts. Such tissue is cut precisely to suit human heart needs, undergoes chemical treatment to make it more durable, and is stitched on a specialized metal alloy frame. Evolut R (depicted in this image) is one of such THVs extensively studied in humans and found to be safe and effective in treating Aortic Stenosis.
TAVR introduction:
TAVR (also known as TAVI) stands for Transcatheter Aortic Valve Replacement (in term TAVI, ‘I’ stands for ‘implantation). TAVR is used for the treatment of severe Aortic Stenosis. As the name implies, this procedure involves implanting a new valve in place of old aortic valve using plastic tubes called catheter by a minimal invasive (suture-less) approach.
What is a heart valve?
Valve is a "device that regulates, directs, or controls the passage of fluid or air by virtue of opening and closing". We all have encountered valves in our lives. Tire valve is one such example which allows air to be injected into the tire and doesn't allow air to escape unless the valve is tampered with or is leaky. The human heart has four such valves which allow unrestricted unidirectional blood flow from one chamber to another. When open, heart valves allow unrestricted blood flow and when closed, they prevent blood from leaking back into the previous chamber. When valves don’t open properly (a condition called ‘stenosis) they put undue stress to the heart by adding resistance to the blood flow. On the other hand, when valves don’t close properly, blood may leak back which makes flow dynamics within the heart less efficient. This condition is called ‘regurgitation’.
The four heart valves are named as Aortic, Mitral, Tricuspid, and Pulmonic. The current discussion is related to the Aortic valve.
Aortic valve and Aortic Stenosis
The Aortic valve (AV) can be regarded as the most important valve of the human heart. It is located between the main pumping chamber of the heart (called Left Ventricle) and the main conduit that carries blood to rest of the body (called Aorta). The human heart beats about 1,00,000 (1 lakh) times a day and with each heartbeat, the Aortic valve opens to allow unrestricted blood flow from Left Ventricle to Aorta. The blood now travels to the rest of the body organs supplying necessary oxygen and nutrients. More than 7000 litres of blood flow across the Aortic valve per day. Heart valves get functional even before birth and, in most situations, are able to withstand this high demand for more than 50 years without any issues.
In some situations, altered flow dynamics across the Aortic valve leads to micro-injury of the valve tissue. As with any injury, the body heals by depositing extra tissue on it. Over the period of time (usually years), continued micro-injury and healing lead to significant tissue/calcium deposition over the valve. This renders the valve stiffer, less mobile, leading to a restricted opening, hence ‘stenosis’. This is more commonly seen in people with:
• Increasing age
• Diabetes or high cholesterol
• Radiation treatment of the chest
• Previous infection of the valve
• Valve deformity by birth
Aortic Stenosis (AS) is a condition where Aortic valve gets narrowed making it difficult for blood to pass through it. Heart muscle has to work harder to overcome this resistance. The heart is able to compensate for this additional workload for many months to years during which a person may not notice any symptoms. When the ‘stenosis’ gets severe, the heart gives up eventually by becoming weak. This leads to heart failure and eventual demise.
Symptoms of Aortic Stenosis
People with a mild or moderate degree of aortic stenosis typically don’t have any symptoms. Severe aortic stenosis may have the following symptoms:
• Chest discomfort
• Difficulty breathing, particularly during walking or while lying down
• Dizziness/giddiness, or fainting
• Decreased exercise capacity
• Leg swelling
Many of the times, symptoms of severe aortic stenosis may not be very obvious. Patients typically slow down in their life to adjust to the disease. They find themselves getting tired too early in activities which they were able to do a few months back. Such limitations are easily attributable to normal ‘ageing’ process. For these reasons, symptoms largely get unnoticed or ignored.
Prevention and treatment of Aortic Stenosis
Unfortunately, most of the preventative strategies which work for coronary blockages (the one that causes a heart attack) like controlling diabetes, cholesterol etc. don’t seem to work in prevention of Aortic stenosis. Still, it is recommended that people should engage in a healthy lifestyle that includes:
* Balanced diet with fewer carbohydrates
* Control of Diabetes and Cholesterol
* Regular exercise and weight management
* Avoid Smoking
Aortic stenosis is a mechanical problem and needs to be fixed mechanically. Medications may improve symptoms by altering the body’s blood flow dynamics but have no effect on the degree of stenosis. Replacing the diseased valve with a new one is the best way to resolve this problem. Standard treatment for severe AS had been replacing the diseased valve with a new artificial valve via open heart surgery.
Heart surgery involves opening the chest, putting the patient on a heart-lung machine, removing the old valve, and stitching a new bioprosthetic valve in place. Patients typically spend 2-4 days in the intensive care unit and another 3-5 days in the general ward. There is 6 weeks rehabilitation period post-surgery. Open heart surgery is highly effective in resolving most of the issues related to severe AS. But as many as 40% of patients for whom surgery is indicated don’t go for surgery due to the increased risk associated with open heart surgery. 10 years ago, these patients were left with no viable alternative, until recently.
TAVR is an effective alternative to surgery for patients with severe AS. Using TAVR therapy, a cardiologist is able to implant a new valve in place of the old diseased aortic valve, all without surgery.
Aortic stenosis can also be treated by balloon valvuloplasty, a procedure where a balloon is inflated within the diseased Aortic valve. As the balloon inflates, it produces cracks and tears within the Aortic valve. While this procedure increases the valve opening, the benefit is short lasting (usually 3-6 months) as the body heals off the injury by that time leading to restenosis.
Who should opt for TAVR?
While TAVR is an attractive minimally invasive alternative to open-heart surgery for the treatment of severe Aortic stenosis, patients should be selected based on certain criteria to ensure a good clinical outcome. Here is a simple checklist that one can follow to determine candidacy for TAVR. The list below is intended to provide basic guidance and by no means is complete. One should always seek the opinion of an expert before making a decision.
1. Diagnosis of severe aortic stenosis should be confirmed, AND
There should be evidence that severe aortic stenosis is affecting the heart function, or is likely to cause a major issue in the future
2. There should be some reason to choose TAVR over open heart surgery:
Patients who are either older than 60 years of age or have other medical issues that put them at higher risk for open heart surgery can be taken up for TAVR
TAVR, pre-procedure
Patients with severe aortic stenosis are screened by the heart team to determine their candidacy for TAVR. This involves confirming the diagnosis of severe aortic stenosis, looking at other medical problems, and doing specific investigations to plan the procedure.
Necessary investigations are obtained beforehand to ensure appropriate therapy options are chosen. Such tests can be:
• Routine blood and urine tests
• ECG
• Chest X-ray
• Echocardiogram
• CT scan of chest/abdomen
• Dental Evaluation
• Tests pertaining to lung function, as needed
• Tests pertaining to brain function, as needed
• Coronary angiography and angioplasty, as needed
TAVR, the procedure
TAVR is a minimally invasive procedure which means no major incision is required. The doctors' team typically comprise of interventional cardiologist, cardiac anaesthetist, cardiac imaging expert, and a cardiac surgeon. The procedure is typically carried out in Cardiac Catheterization Laboratory (same laboratory where coronary angiography and angioplasty is done). The procedure is mostly done under local anaesthesia, but general anaesthesia can also be used based on the patient’s clinical profile. A small incision is made in the upper thigh through which a plastic tube carrying an artificial heart valve is inserted. The valve is taken to its designated spot and implanted. TAVR obviates any need of opening the chest, putting on a heart-lung machine, prolonged anaesthesia or intensive care etc. The procedure takes about 1 hour to perform and is done with x-ray and echocardiogram guidance. The procedure, to some degree, is similar to getting a stent placed in the heart.
TAVR, post-procedure
A typical patient is able to talk to family members immediately after the procedure, is able to sit and eat within 4-6 hours of the procedure, and can walk that evening itself. The patient is typically observed in intensive care for 24 hours after which he/she is transferred to a regular room. Patients are typically discharged home within 3-4 days. They are able to resume their routine activities within a week and are able to enjoy a scar-free life without any major physical restriction. Many patients were able to go shopping by the second week, and travel abroad within a month.
Majority of patients do not require blood thinners or any other special medicines after the procedure. In fact, they might be able to get off some of their previous heart medicines.
TAVR, the valve (THV)
The TAVR valve (or THV) is made from animal pericardium (human or animal heart is covered by a thin rim of tissue called ‘pericardium’). The pericardial tissue is laser-cut into small pieces that are sewed together on a metal platform to take shape of a valve. The metal platform helps the valve anchor at its designated place. The THV is pre-treated with chemicals to increase its longevity and withstand continuous blood flow across it. These valves undergo rigorous testing outside the human body before they are brought into the market. Since they are tissue valves (as compared to metal valves that can only be placed by open heart surgery), they are expected to degenerate over time. Since TAVR is a new technique, studies are ongoing regarding their average lifespan. So far, these valves are shown to be functioning very well 8 years after the implantation and are expected to last about 15 years.
TAVR, the science behind
TAVR has been extensively studied in over 10,000 patients to evaluate its efficacy and safety. In the majority of the studied population, TAVR has performed similar or better than open heart surgery. TAVR offers similar benefits of implanting a new valve as in open heart surgery, minus the surgical risk.
TAVR, potential complications
While TAVR is a much safer alternative compared to open heart surgery in a patient with higher surgical risk, just like any other procedure TAVR is not free of complications. Few of the potential complications may include:
• Bleeding
• Infection
• Peri-procedural stroke/paralysis
• Peri-procedural death
• Need for emergent open heart surgery
• Blood vessel injury
• Anaesthesia-related complications
• Valve dysfunction
• Kidney injury
• Heart rhythm disturbances requiring pacemaker and others
TAVR, the bottom-line
TAVR can easily be regarded as the most disruptive innovation in cardiovascular medicine in the past decade. First TAVR was successfully performed in humans in the year 2002 in France. Since then, more than 2 lakhs valves have been implanted across the world with excellent success. TAVR is not for everyone. A thorough discussion between patient/family and treating physician is necessary to understand a patient’s health condition and eligibility for TAVR. As it stands today, TAVR is a life-saving treatment alternative for many patients with severe AS who till now had no option other than to undergo open heart surgery.
Contact for more information
You can call/SMS/WhatsApp at +91 800 807 4242, or email at tavr@carehospitals.com.
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