The only curative treatments for aortic valve defects are valve repair or valve replacement using either a mechanical or a biological prosthesis. An aortic valve replacement can be performed via transcatheter aortic valve implantation (TAVI) or open-heart surgery. Outcomes following a surgical aortic valve replacement (SAVR) are generally favorable; however, the procedure carries inherent risks.

Atrial fibrillation (AF) is the most common complication following SAVR, occurring in approximately 32.9% to 74.0% of patients during the index hospitalization and in 18.5% to 44.5% later postoperatively. Among patients undergoing a mechanical aortic valve replacement, stroke remains one of the most feared complications, with an estimated annual incidence ranging from 0.4% to 1.8%. Due to the thrombogenic nature of mechanical valves, lifelong anticoagulation therapy is required. However, this therapy increases the risk of major bleeding events.

This thesis investigated the complications following a bioprosthetic and a mechanical SAVR, with a focus on new-onset atrial fibrillation (NOAF), major stroke, and bleeding events, as well as their associations with antithrombotic therapy.

The findings indicate that NOAF occurs in a substantial proportion of patients after both a bioprosthetic and a mechanical SAVR. Furthermore, patients who develop NOAF during their initial hospitalization are at high risk of recurrent AF later in life and all-cause mortality in both bioprosthetic and mechanical SAVR cohorts.

In addition, the incidence of early postoperative major bleeding is significantly higher than that of a major stroke following a bioprosthetic and a mechanical SAVR. The risk of major bleeding remains higher during both early and late periods in patients with a mechanical aortic valve prosthesis, while in patients with bioprosthesis, the risks of stroke and bleeding are nearly equal.

In the future, the guidelines should account for bleeding risk in addition to thrombotic complications in patients undergoing SAVR.