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Page 2 of 12 Verolino et al. Vessel Plus 2018;2:17 I http://dx.doi.org/10.20517/2574-1209.2018.32
[1]
the outflow obstruction is removed by aortic valve intervention . Surgical aortic valve replacement (SAVR)
has been the gold standard treatment for a long time; however, with ageing and increasing multimorbidity of
AS population, the need for a less invasive approach was clearly identified in the first European Heart Sur-
[2]
vey, where a significant number of patients, about 42%, were not referred or accepted for surgery . The in-
troduction of percutaneous treatment for severe AS with transcatheter aortic valve implantation (TAVI) re-
[2]
mains one of the latest and greatest achievements in interventional cardiology. Since Cribier et al. reported
the first “proof-of-concept” case of TAVI in 2002, more than 200,000 patients have undergone this procedure
in approximately 65 countries. Starting off as a new approach for high-risk patients, TAVI has nowadays
proved to be the best strategy in frail patients and is becoming increasingly seen as a very interesting option
for those with intermediate risk. Recently, increased operator experience and improved device systems have
led to consider the extension of this therapeutic strategy also to low-risk patients. Thus, in this intriguing
setting, this review summaries the present and future indications of TAVI.

CURRENT GUIDELINES RECOMMENDATIONS
The current guidelines of the European Society of Cardiology (ESC)/European Association for Cardio-
Thoracic Surgery (EACTS) on valvular heart diseases established that the choice for intervention, SAVR vs.
TAVI, should be based on a careful evaluation of patients’ procedural risk and technical suitability, thus a
[3]
precise assessment of risks/benefits balance of each modality . Importantly, local expertise and outcomes
data for both surgical and percutaneous intervention must be carefully evaluated and the Heart Team has to
play a fundamental role in the final therapeutic decision of AS patients. Thus, the selection of TAVI vs. SAVR
should involve a multidisciplinary discussion between cardiologists, surgeons, imaging specialists, anesthe-
[3]
siologists, and other specialists if necessary .

In view of this, according to ESC guidelines, TAVI is recommended in all patients with severe symptomatic
[3]
AS and a predicted survival greater than one year who are not eligible for SAVR (Class IB) . Data support-
ing this indication has been presented in many European registries such as the CoreValve Extreme Risk Reg-
[4-7]
istry and from the randomized Placement of AoRTic TraNscathetER valves (PARTNER I B) study . How-
ever, in this setting, the definition of “inoperable patient” has been problematic because it comes from score
systems usually used for surgical population (Society of Thoracic Surgeons - STS or EuroSCORE II), that are
not able to capture all comorbidities that make a patient an inadequate candidate for conventional surgery.
Over the last few years, it has become clear that other factors such as frailty and anatomical features (porcelain
aorta, “hostile chest”, liver disease, substernal location of a mammary graft) needed to be considered. Thus,
the central element to evaluate whether patients are at high risk for surgery remains clinical judgment: the
ability to integrate a quantitative assessment based on the traditional surgical risk scores and other impor-
tant clinical features observed in the “real world” AS population but not included within score systems.

The current ESC guidelines also recommend that TAVI should be considered an alternative to SAVR in
severe AS patients who are at high risk for mortality and complications after conventional surgery, thus
[3]
those with STS or EuroSCORE II ≥ 4% or logistic EuroSCORE I ≥ 10% . Of note, TAVI should be favored
in elderly patients eligible for transfemoral access as suggested by registries and two important randomized
controlled trials comparing TAVI vs. SAVR: the PARTNER I A trial, using a balloon-expandable device,
[8,9]
and the CoreValve High-Risk study with a self-expandable valve . Similar recommendations are reported
by the American Heart Association/American College of Cardiology (AHA/ACC) Guidelines for the man-
[10]
agement of patients with valvular heart disease . They recommend a global risk assessment resulting in a
4-group classification (low, intermediate, high and prohibitive risk) according to STS score value (< 4% in
low risk, between 4% and 8% in intermediate risk, > 8% in high risk), presence or not of frailty, impairment
in 1 or more major organ systems (no comorbidity in low risk, 1 organ system in intermediate risk, 2 in high