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Transcatheter aortic valve implantation: Work up and indications for intervention


Background

Aortic stenosis is the most common valvular heart disease in the elderly population, with a prevalence of approximately 3% in patients over 75 years old. The prognosis of symptomatic severe aortic stenosis is poor, with a 50% mortality rate at 2 years; therefore valve replacement is usually recommended once symptoms of shortness of breath, heart failure, or angina occur.

In the majority of patients, the aortic valve is trileaflet. Patients with severe aortic stenosis below the age of 65 usually have a congenital bicuspid aortic valve. In both cases, the aortic valve becomes progressively calcified with age and leaflet movement is restricted.

TAVR for aortic stenosis

Transcatheter aortic valve replacement (TAVR) has emerged as an alternative to surgical aortic valve replacement (SAVR) in patients with severe symptomatic aortic stenosis. The last decade has seen a steep rise in the number of TAVR procedures performed, as well as improvements in valve design, technology, and procedural techniques.

Decisions regarding the type of valve and approach to valve implantation are best made through a heart valve team and performed in a center with appropriate experience and infrastructure. In low-risk patients, the current American Heart Association/American College of Cardiology (AHA/ACC) guidelines recommend SAVR via a midline sternotomy. Patients at high and intermediate risk may have TAVR recommended ( Box 7.1 ). TAVR in low-risk patients is feasible, but requires further data on prosthesis durability before it is offered in younger patients.

BOX 7.1 ■
AHA Guidelines

I C For patients considered for TAVR, a heart valve team, including experts in valvular heart disease, cardiac imaging, interventional cardiology, cardiac anesthesia, and cardiac surgery, should collaborate to provide optimal patient care
I A SAVR or TAVR is recommended for symptomatic patients with severe aortic stenosis (AS) and high risk for SAVR, depending on patient-specific procedural risks, values, and preferences
I A TAVR is recommended for symptomatic patients with severe AS and a prohibitive risk for SAVR who have a predicted post-TAVR survival greater than 12 months
IIa B-R TAVR is a reasonable alternative to SAVR for symptomatic patients with severe AS and an intermediate surgical risk, depending on patient-specific procedural risks, values, and preferences
III B TAVR is not recommended in patients in whom existing comorbidities would preclude the expected benefit from correction of AS

Assessment and risk stratification of patients

The Society of Thoracic Surgeons (STS) score and other factors may be used to stratify patients into low, intermediate, and high risk ( Table 7.1 ). The STS score is based on age, gender, comorbidities (including hypertension, peripheral arterial disease, cerebrovascular disease, diabetes, and lung disease), and immediate preoperative condition (including presence of cardiogenic shock and whether the patient currently has heart failure). Scores are best assessed using the online calculator found at http://riskcalc.sts.org/stswebriskcalc/ . The Euroscore uses similar criteria and is found at http://www.euroscore.org .

TABLE 7.1 ■
Assessment of Procedural Risk for TAVR
From Otto CM et al 2017 ACC Expert Consensus Decision Pathway for TAVR JACC 2017. STS PROM: Society of Thoracic Surgeons Predicted risk of mortality
Low risk
  • ■

    STS-PROM <4%

  • ■

    No frailty

  • ■

    No comorbidities

  • ■

    No procedure-specific impediments

Intermediate risk
  • ■

    STS-PROM 4%-8%

  • ■

    Mild frailty

  • ■

    One major organ system compromise not to be improved postoperatively

  • ■

    A possible procedure-specific impediment

High risk
  • ■

    STS- PROM >8%

  • ■

    Moderate-severe frailty or >2 major organ system compromise not to be improved postoperatively

  • ■

    A possible procedure-specific impediment

Prohibitive risk
  • ■

    STS PROM >50% at 1 year

  • ■

    ≥3 major organ compromise not to be improved postoperatively

  • ■

    Severe frailty

  • ■

    Severe procedure specific-impediments

Other risk factors may make patients high risk for SAVR despite a low STS score. These would include prior chest radiation, porcelain aorta, and previous coronary artery bypass graft (CABG) with patent grafts. These patients may be offered TAVR if the heart team consider this to be the optimal strategy.

Contraindications to TAVR

  • ■

    Active endocarditis

  • ■

    Patient with poor life expectancy or comorbidities that would preclude likely benefit from a valve-in-valve TAVR procedure

  • ■

    Anatomic unsuitability for either self-expanding or balloon-expandable prosthesis (covered in the following chapters), for example, aortic annulus too large for largest currently available valves

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