TAVR/TAVI: How Transcatheter Aortic Valve Replacement Works

A severely diseased aortic valve can eventually make it difficult for the heart to push blood from the left ventricle into the aorta.

For many years, replacing the valve meant open cardiac surgery. Today, selected patients can undergo transcatheter aortic valve replacement (TAVR), also called transcatheter aortic valve implantation (TAVI).

Instead of removing the native aortic valve through conventional open-heart surgery, a replacement valve is delivered through a catheter and positioned inside the diseased valve.

The existing valve is displaced by the new prosthesis, allowing blood to flow through the newly implanted valve.

TAVR has transformed treatment for selected patients with severe aortic stenosis, particularly those in whom conventional surgery carries substantial risk. Harrison’s describes the development of TAVR as extending aortic valve replacement to patients who were previously considered at high or prohibitive surgical risk.

However, TAVR is not simply a less invasive version of surgical valve replacement.

Patient selection, valve anatomy, vascular access, age, life expectancy, associated disease and long-term considerations all matter.

What is TAVR or TAVI?

TAVR and TAVI refer to essentially the same type of procedure.

• TAVR = transcatheter aortic valve replacement
• TAVI = transcatheter aortic valve implantation

The terminology varies between institutions and countries.

The basic concept is straightforward:

A replacement valve is delivered through a catheter and implanted within the diseased native aortic valve.

The new valve is mounted within a supporting metal frame. Depending on the valve system, the frame may be expanded using a balloon or may be self-expanding.

Harrison’s describes both balloon-expandable and self-expanding transcatheter valve systems.

What problem does TAVR treat?

TAVR is primarily used to treat aortic stenosis.

Aortic stenosis occurs when the aortic valve becomes narrowed and cannot open normally.

The left ventricle must generate greater pressure to eject blood through the narrowed valve.

Over time, the increased pressure load can cause the left ventricular muscle to become thickened and eventually dysfunctional.

Severe aortic stenosis can produce symptoms such as:

• breathlessness
• chest discomfort
• dizziness
• fainting
• reduced exercise capacity
• fatigue
• eventually, symptoms of heart failure

Harrison’s describes severe symptomatic aortic stenosis and deterioration of left ventricular systolic function as important indications for valve intervention.

Modern treatment decisions, however, should use current guideline definitions of severe aortic stenosis rather than relying solely on thresholds from an older textbook.

Why is severe aortic stenosis treated?

A severely narrowed aortic valve creates a mechanical obstruction between the left ventricle and systemic circulation.

As the obstruction progresses, the heart must work harder to maintain forward blood flow.

Eventually, patients may develop:

• progressive exercise limitation
• heart failure
• reduced ventricular function
• syncope
• angina
• increased risk of cardiovascular complications

Medication can help manage associated conditions and symptoms, but it does not mechanically open a severely calcified aortic valve.

Once severe aortic stenosis reaches the point where valve replacement is indicated, the definitive treatment involves replacing the valve through an appropriate surgical or transcatheter strategy.

Who may be considered for TAVR?

TAVR is not determined by age alone.

A specialist valve team considers a combination of factors, including:

• severity of aortic stenosis
• symptoms
• left ventricular function
• valve and aortic anatomy
• vascular access
• surgical risk
• frailty
• other medical conditions
• previous cardiac surgery
• life expectancy
• anticipated durability of the prosthesis
• patient preferences

Harrison’s specifically describes the importance of a Heart Team in difficult treatment decisions and notes that severe comorbidity and frailty can make TAVR inappropriate in some patients.

The role of TAVR has expanded substantially since the Harrison’s edition used for this article was published.

Therefore, the historical distinction of “inoperable,” “high risk” or “intermediate risk” should not be treated as a complete modern eligibility rule.

TAVR vs surgical aortic valve replacement

The two approaches have the same broad objective:

replace a severely diseased aortic valve.

But the way they accomplish this is different.

Surgical aortic valve replacement

During surgical AVR, the chest is opened and the diseased native valve is surgically removed and replaced with a prosthetic valve.

TAVR

During TAVR, a replacement valve is delivered through a catheter and deployed within the existing native valve.

The native valve is not routinely removed.

This means that TAVR can avoid the sternotomy and cardiopulmonary bypass associated with conventional surgical valve replacement.

But avoiding open surgery does not mean that TAVR is risk-free.

How is a TAVR procedure performed?

The exact technique varies according to the valve system and access route, but the basic sequence is relatively consistent.

1. Planning and imaging

Before the procedure, the valve team needs detailed information about:

• the aortic valve
• aortic root
• aortic annulus
• coronary arteries
• aorta
• peripheral arteries
• potential catheter access routes

Imaging is therefore an important part of planning.

The objective is to determine whether the anatomy can accommodate the chosen prosthesis and whether the delivery system can safely reach the heart.

2. Vascular access

The catheter must enter the arterial circulation.

The transfemoral route, through the femoral artery, has become the principal catheter route when suitable vascular anatomy is present.

Harrison’s describes transfemoral access as the most commonly used route and also discusses alternative access routes.

3. Crossing the aortic valve

A guidewire and catheter are advanced toward the heart and across the diseased aortic valve.

The system must be carefully positioned so that the replacement valve can be accurately deployed.

4. Preparing the valve

Balloon aortic valvuloplasty may be used to enlarge the opening and prepare the site for prosthesis deployment.

Harrison’s describes balloon valvuloplasty under rapid right-ventricular pacing as part of the procedure described in its edition.

The exact procedural strategy depends on the valve platform and current practice.

5. Positioning the replacement valve

The replacement valve is advanced across the native aortic valve.

Precise positioning is essential.

The prosthesis must sit securely within the aortic annulus while allowing unobstructed blood flow and avoiding interference with nearby structures, particularly the coronary arteries and conduction system.

6. Deploying the valve

Depending on the valve system, the prosthesis is either:

• expanded using a balloon, or
• released using a self-expanding mechanism.

Harrison’s describes both balloon-expandable and self-expanding systems.

Once deployed, the prosthetic valve pushes the diseased native leaflets aside.

7. Checking the result

The team evaluates:

• valve position
• prosthetic valve function
• residual aortic regurgitation
• pressure gradients
• coronary blood flow
• vascular access complications
• conduction abnormalities

If necessary, additional balloon expansion or other intervention may be performed.

What are the different access routes?

Transfemoral

The catheter is introduced through the femoral artery in the groin.

This is generally the preferred access route when the peripheral arteries are suitable.

Transapical

The catheter is introduced through the apex of the heart.

Bailey & Love describes this as an antegrade approach performed through a small left anterolateral thoracotomy.

Subclavian or other arterial approaches

Alternative arterial routes can be considered when the femoral arteries are unsuitable.

Harrison’s describes subclavian, carotid and ascending aortic routes among alternative approaches used for TAVR.

The availability of alternative approaches means that unsuitable femoral access does not automatically exclude transcatheter treatment, although the patient’s anatomy determines whether another route is appropriate.

Why does vascular anatomy matter?

TAVR delivery systems must travel through an artery to reach the heart.

Severe peripheral arterial disease can therefore create an important technical challenge.

Factors that may affect access include:

• vessel diameter
• calcification
• tortuosity
• previous vascular surgery
• aortic disease
• previous aortic operations

Bailey & Love specifically notes that peripheral vascular disease, small vessels, tortuous vessels and aortic disease can make transluminal approaches unsuitable.

This is why detailed pre-procedure imaging is so important.

Balloon-expandable vs self-expanding valves

Transcatheter valves broadly fall into two mechanical categories.

Balloon-expandable valves

A balloon is inflated to expand the valve frame within the aortic annulus.

Self-expanding valves

The valve frame expands by its own mechanical properties after release from the delivery system.

Harrison’s describes both types and illustrates their different deployment mechanisms.

The choice of valve depends on the patient’s anatomy and the characteristics of the available prosthesis.

It should not be reduced to a simple “which valve is better?” question.

What are the advantages of TAVR?

For appropriately selected patients, TAVR can avoid some of the major components of conventional open-heart surgery.

Potential advantages include:

• no median sternotomy
• no surgical removal of the native valve
• less invasive access
• potentially shorter recovery
• avoidance of conventional cardiopulmonary bypass in the transcatheter procedure

The clinical benefit depends on the patient and the indication.

TAVR was initially developed for patients at very high surgical risk but subsequently became an important option in progressively broader groups of patients.

Harrison’s describes trials demonstrating favourable outcomes in patients who were considered inoperable and comparable outcomes with surgery in selected higher-risk groups.

Those historical trial results helped establish TAVR but should not be interpreted as current treatment thresholds.

What are the risks of TAVR?

TAVR is less invasive than conventional open surgery, but serious complications can occur.

Potential complications include:

• bleeding
• vascular injury
• stroke
• coronary obstruction
• aortic injury
• cardiac perforation
• cardiac tamponade
• acute kidney injury
• valve malposition
• prosthetic valve dysfunction
• residual or paravalvular aortic regurgitation
• conduction abnormalities
• need for permanent pacemaker
• need for emergency surgery
• death

Bailey & Love describes vascular complications, stroke, aortic regurgitation, atrioventricular block and the possibility of conversion to open surgery among complications of TAVI.

The frequency of these complications varies with patient selection, anatomy, valve platform and operator/centre experience.

Why can TAVR cause a heart block?

The aortic valve sits close to the heart’s electrical conduction system.

During valve deployment, the prosthetic frame can exert pressure on nearby conduction tissue.

This can interfere with electrical conduction between the atria and ventricles.

The result may be:

• new conduction abnormalities
• bundle branch block
• atrioventricular block
• need for permanent pacemaker implantation

Harrison’s identifies heart block requiring permanent pacemaker implantation as a recognised complication of TAVR.

This is one reason electrical monitoring is an important part of post-procedure care.

What is paravalvular aortic regurgitation?

A prosthetic valve should form an effective seal within the aortic annulus.

If there is a gap between the prosthetic frame and surrounding tissue, blood can leak around the outside of the valve.

This is called paravalvular aortic regurgitation.

The severity can range from clinically insignificant to important.

Harrison’s identifies paravalvular aortic regurgitation as an important complication associated with TAVR and notes its relationship with outcomes.

Modern valve design and implantation techniques have reduced this problem compared with early-generation devices, but it remains an important consideration.

Can TAVR cause a stroke?

Yes.

Stroke is an important potential complication.

Manipulation of catheters and prosthetic devices within the aorta and calcified aortic valve can potentially dislodge material that travels to the cerebral circulation.

Harrison’s identifies an early hazard of stroke following TAVR, while Bailey & Love also lists stroke among recognised TAVI complications.
The absolute risk depends on patient characteristics, anatomy and procedural factors.

Can TAVR damage the coronary arteries?

The coronary arteries originate close to the aortic valve.

During implantation, the displaced native valve leaflets can potentially interfere with coronary blood flow.

Coronary obstruction is uncommon but potentially catastrophic.

This is one reason detailed pre-procedure imaging is required.

The valve team evaluates the relationship between:

• aortic annulus
• native valve leaflets
• coronary arteries
• aortic root

before deciding whether TAVR is technically suitable.

What is valve-in-valve TAVR?

A transcatheter valve can sometimes be implanted inside a previously implanted surgical bioprosthetic valve that has deteriorated.

This is known as a valve-in-valve procedure.

Instead of performing another open surgical valve replacement, a transcatheter prosthesis is positioned within the failing biological valve.

Harrison’s describes valve-in-valve treatment for structural deterioration of bioprosthetic aortic valves as an alternative to repeat valve replacement in selected patients.

Patient anatomy and the characteristics of the original surgical valve determine whether this approach is feasible.

Is TAVR permanent?

The intention is for the implanted prosthetic valve to provide durable valve function.

However, no prosthetic valve should be described as guaranteed to last for life in every patient.

Durability is particularly important when TAVR is considered in younger patients with a long expected lifespan.

The long-term durability evidence available to Harrison’s was more limited because the technology was relatively new at the time of publication. Harrison’s specifically noted that longer-term outcomes beyond the available follow-up remained an area of uncertainty.

This is an area where modern evidence is essential when counselling individual patients.

TAVR vs surgical AVR

Neither column represents an automatic recommendation.

The appropriate approach depends on the individual patient’s anatomy, clinical condition, expected longevity, surgical risk and preferences.

What happens after TAVR?

After the procedure, patients are monitored for:

• rhythm disturbances
• bleeding
• vascular complications
• neurological symptoms
• kidney function
• valve function
• residual regurgitation
• changes in blood pressure
• access-site complications

An echocardiographic assessment is generally used to evaluate the new valve.

The patient may also need monitoring for conduction abnormalities because heart block can develop around the time of the procedure.

Recovery is generally focused on gradually returning to normal activity while monitoring for complications.

What should patients expect long term?

A successful TAVR does not mean that cardiovascular follow-up ends.

Patients generally require ongoing assessment of:

• prosthetic valve function
• ventricular function
• symptoms
• blood pressure
• rhythm
• coronary disease and other cardiovascular conditions

The implanted valve also becomes part of the patient’s permanent medical history.

Patients should inform healthcare professionals about the prosthetic valve before future procedures.

What questions should you ask before TAVR?

A patient considering TAVR may want to ask:

1. How severe is my aortic stenosis?
2. Why is valve replacement recommended now?
3. Why is TAVR being considered instead of surgical AVR?
4. Is my vascular anatomy suitable for transfemoral TAVR?
5. If not, what alternative access route would be considered?
6. Which valve system is being recommended and why?
7. What is my individual risk of stroke, vascular injury and pacemaker implantation?
8. What is the expected durability of the prosthesis for someone with my age and circumstances?
9. Would valve-in-valve treatment be possible if the prosthesis deteriorates later?
10. What follow-up will I need after the procedure?

The key point

TAVR/TAVI replaces a diseased aortic valve without conventional surgical removal of the native valve.

A prosthetic valve mounted within a metal frame is delivered through a catheter—most commonly through the femoral artery when the vascular anatomy permits—and deployed within the diseased aortic valve. Harrison’s describes both balloon-expandable and self-expanding systems and the use of alternative access routes when transfemoral access is unsuitable.
The procedure has expanded the treatment options for patients with severe aortic stenosis, but TAVR is not appropriate simply because it is less invasive.

The decision requires assessment of aortic valve disease, anatomy, vascular access, surgical risk, frailty, associated conditions, expected longevity and long-term prosthetic considerations.

For this reason, TAVR is best viewed as part of a broader valve-treatment pathway rather than as a universal replacement for surgical aortic valve replacement.

Written and Reviewed By Dr. Munaf Ahmad Ansari

Medical information note: This article is written for information purpose only. Individual treatment decisions should be based on contemporary clinical guidelines and assessment by an appropriately qualified medical team.