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Page 4 of 13 Mauri et al. Mini-invasive Surg 2022;6:49 https://dx.doi.org/10.20517/2574-1225.2022.34

Data on thrombosis of the bioprosthesis are currently the most debated: thrombus can present as hypo-
attenuated thickening (HALT), as HALT with reduced leaflet motion (RLM), or as clinical thrombosis with
increased transvalvular gradients. In the Evolut Low Risk trial analysis, including patients treated with
surgical or transcatheter procedures, at one-year follow-up, HALT and RLM were detected with CT scan in
30.9% and 31% of cases treated with self-expanding transcatheter bioprosthesis, respectively . The clinical
[10]
effects of these findings are uncertain and controversial; in some studies, it was associated with an increased
rate of cerebrovascular events .
[11]

[12]
Conversely, patients undergoing TAVR are at a concomitant increased risk of bleeding . However, the rate
of major bleeding in clinical trials has decreased over time with an incidence of about 20% in inoperable
[14]
patients and 7.7% in patients at low surgical risk . The reduction of sheath size, the improved
[13]
experience of operators, and the treatment of younger patients have led to a decrease in procedural bleeding
events. Female sex, Society of Thoracic Surgeons (STS) score, chronic kidney disease, low hemoglobin at
baseline, atrial fibrillation or flutter at baseline or 30 days, post-procedural moderate/severe paravalvular
leak at 30 days, and a greater left ventricular mass have been reported as independent predictors of bleeding
complications [12,15] .

Later major bleeding complications (> 30 days after procedure) occurred in about 6% of patients undergoing
[12]
TAVR, with a gastrointestinal event in more than half of the cases .
In real world, the incidence of bleeding was not different between access-site and non-access-site events, but
the latter occurred later (> 30 days after procedure) in more cases. Even though both were associated with
adverse outcomes, mortality was higher in patients who experienced a non-access-site event .
[15]
Table 2 summarizes rates of death, myocardial infarction, stroke, and bleeding events from the main
randomized clinical trials according to surgical risk and type of bioprosthesis (i.e., self-expandable vs.
balloon-expandable valves).

REVIEW OF CURRENT EVIDENCE
The first recommendation to administer a DAPT with ASA plus clopidogrel for 3-6 months after TAVR
was extrapolated from the experience with coronary stents. Multiple subsequent studies and metanalyses
have questioned this approach due to the increased bleeding risk associated with the use of DAPT [16-18] .

However, as many patients undergoing TAVR present a concomitant AF or received a prior percutaneous
coronary intervention (PCI) and are already receiving a tailored SAPT, DAPT, or OAC before a
[19]
procedure, any further choice about antithrombotic therapy is challenging. Several trials have been designed
to evaluate the best treatment regimen in these different settings.

Patients without indication for long-term OAC [Table 3]
[20]
Ussia et al. first questioned the risk-benefit ratio of DAPT after TAVR . Two small following randomized
trials, the SAT-TAVI (single antiplatelet therapy for transcatheter aortic valve implantation) and ARTE
studies (aspirin versus aspirin + clopidogrel following transcatheter aortic valve implantation), failed to
show the benefit of DAPT compared to SAPT; furthermore, the use of DAPT was associated with an
increased risk of major or life-threatening bleeding. Similar results have been obtained in subsequent meta-
analyses , and in one of them, DAPT was associated with increased mortality at 30 days (RR: 0.57; P =
[21]
[22]
0.014) .