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Page 4 of 13 Cangemi et al. Mini-invasive Surg 2022;6:3 https://dx.doi.org/10.20517/2574-1225.2021.99

further increase during physical exercise (thus explaining discrepancy angina) and when vasodilators are
[35]
administered during FFR assessment. Pesarini et al. , measuring FFR before and after TAVI, revealed that
after prosthesis implantation negative baseline values became even more negative and positive ones became
even more positive. Only 6% of lesions exhibited such a variation that resulted in a change of indication to
treat. Despite the risk of FFR to underestimate some intermediate coronary lesions, in a single-center Italian
[36]
registry , FFR-guided revascularization was superior to angio-guided revascularization at two-year follow-
up. It has been shown that coronary flow during the wave-free period of diastole remains unchanged after
[37]
TAVI . Instantaneous wave-free ratio (iFR), an index independent of vasodilatation, is calculated during
this period and does not vary significantly before and after TAVI . However, in patients with severe AS,
[37]
there is an increased resting coronary blood flow, which could affect currently validated thresholds for iFR.
Yamanaka et al. compared iFR and FFR with myocardial perfusion scintigraphy in patients affected by
[38]
CAD and severe AS. They showed a good correlation between FFR/iFR and perfusion scintigraphy in
identifying myocardial ischemia. Moreover, an optimal cut-off of 0.82 for the iFR was identified to indicate
an FFR < 0.75 and myocardial ischemia on perfusion scintigraphy. The optimal cut-off of 0.82 for iFR in this
setting of patients has been confirmed in other studies . Recently, revascularization based on a “hybrid
[39]
iFR-FFR” strategy has been proposed . This strategy uses iFR as the primary choice to evaluate coronary
[40]
[40]
stenosis and FFR evaluation for iFR values between 0.83 and 0.93 . The ongoing trials FAITAVI
(Functional Assessment in TAVI), NOTION-3 (Revascularization in Patients Undergoing Transcatheter
Aortic Valve Implantation), and TAVI-PET (Correlation of FFR and iFR With Cardiac PET Perfusion in
Patients With Severe Aortic Valve Stenosis) will provide information to comprehend the role of FFR in this
group of patients.

THE OPTIMAL TIMING OF REVASCULARIZATION
[21]
American guidelines recommend PCI before TAVI in the case of left main disease and significant
proximal CAD. Instead, European guidelines do not recommend specific timing for coronary
[20]
revascularization but suggest basing a decision on the clinical presentation, coronary anatomy, and extent of
myocardial at risk. While performing PCI before TAVI reduces any ischemic events in the case of
periprocedural complications and avoids difficult coronary engagement after implantation of the prosthesis,
performing TAVI before PCI allows evaluating symptoms and hemodynamic significance of coronary
lesions after the resolution of the aortic stenosis [Table 1]. Severe aortic stenosis was initially considered a
contraindication for PCI. Instead, Goel et al. showed that this was feasible without an increase in
[41]
mortality. A recent multicenter study highlighted that PCI before TAVI is currently performed successfully
in most cases even in multivessel disease, left main disease, and calcific stenosis . In the same study, the
[42]
[42]
two-year rate of target vessel failure was low . Regarding the disadvantages of performing PCI before
TAVI, there is an increased risk of acute kidney injury, bleeding, and vascular complications [24,43,44] .
Therefore, PCI before TAVI should be performed in the case of complex coronary stenosis with large
myocardial area at risk, acute coronary syndromes, and even in the case of difficult coronary re-access after
prosthesis implantation. With the improvement of techniques and experience of the operators, routinely
performing PCI and TAVI in the same session has been proven to be safe and reduce hospitalization
length [Figure 2]. According to the literature, PBAV (percutaneous balloon aortic valvuloplasty) and PCI
[45]
can be safely performed during the same procedure [46,47] . This approach can be used as a bridge to TAVI in
patients with temporary TAVI contraindication. Small case series have shown the possibility of using
Impella as an assistance during PBAV or PCI procedures in patients with severe aortic stenosis [48,49] .

The strategy of performing PCI after TAVI is a recent approach [Figure 3]. The revascularization of
coronary disease was an inclusion criterion of the first trial due to the fear of ischemic events during the
procedure and the lack of knowledge regarding the possibility of selective cannulate coronary arteries ostia