Aspirin Therapy After Aortic Valve Replacement
For bioprosthetic AVR, aspirin 75-100 mg daily is reasonable for all patients long-term, with consideration of warfarin (INR 2.0-3.0) for the first 3 months in those at low bleeding risk. 1
Bioprosthetic Aortic Valve Replacement
First 3 Months Post-AVR
Warfarin (INR 2.5, range 2.0-3.0) may be reasonable for the first 3 months after bioprosthetic AVR, as patients face highest thromboembolic risk during this period before complete valve endothelialization. 1
A large Danish registry (4,075 patients) demonstrated that warfarin therapy reduced stroke rates from 7.00 to 2.69 per 100 person-years (HR 2.46) and cardiovascular death from 6.50 to 2.08 per 100 person-years, with benefits persisting up to 6 months without significantly increased bleeding risk. 1
However, aspirin 75-100 mg daily alone is also reasonable during this period, particularly in patients at higher bleeding risk or those in sinus rhythm with normal LV function and no history of thromboembolism. 1
After 3 Months (Long-term)
Aspirin 75-100 mg daily is reasonable for all patients with bioprosthetic aortic valves as lifelong therapy (Class IIa recommendation). 1
The annual thromboembolic risk with bioprosthetic valves averages 0.7% in patients with sinus rhythm, with aortic prostheses having lower rates than mitral prostheses (1.9% vs 2.4% per patient-year). 1
Transcatheter Aortic Valve Replacement (TAVR)
Standard Regimen
Aspirin 75-100 mg daily lifelong plus clopidogrel 75 mg daily for 3-6 months is the established regimen for TAVR patients without anticoagulation indications. 2
This dual antiplatelet approach was used in original TAVR trials, though recent evidence questions whether dual therapy provides benefit over aspirin alone. 2, 3
Meta-analysis of 1,086 patients showed DAPT increased bleeding risk at 6-12 months (RR 1.67) without reducing mortality, stroke, or MI compared to aspirin alone. 3
Patients Requiring Anticoagulation
For patients with atrial fibrillation or other anticoagulation indications, use warfarin (INR 2.0-2.5) for the first 3 months, then may transition to a DOAC after 3 months. 2
Warfarin use after TAVR was associated with lower stroke rates and reduced valve gradient increases in the PARTNER 2 registry. 1
Mechanical Aortic Valve Replacement
Standard Mechanical Valves
Warfarin (INR 2.0-3.0) plus aspirin 75-100 mg daily is recommended for bileaflet mechanical or Medtronic Hall aortic prostheses in patients without additional risk factors. 1
Patients with risk factors (AF, prior thromboembolism, LV dysfunction, hypercoagulable state) require higher INR targets (2.5-3.5). 1
The addition of aspirin to warfarin reduces major embolism or death from 8.5% to 1.9% per year (p<0.001) and stroke from 4.2% to 1.3% per year (p<0.027), with only modest increase in minor bleeding. 1
On-X Mechanical Valves
For On-X aortic valves specifically, lower-intensity warfarin (INR 1.5-2.0) plus aspirin 81 mg daily may be used after the first 3 months (during which standard INR 2.0-3.0 is maintained). 1
An RCT demonstrated significantly less major bleeding with low-intensity INR (1.48% vs 3.26% per patient-year, p=0.047) without increased thromboembolic events or mortality. 1
Recent registry data (510 patients, median follow-up 3.4 years) showed INR target of 1.8 (range 1.5-2.0) plus aspirin reduced the composite endpoint by 57% and major bleeding by 85% compared to standard-dose warfarin. 4
Critical Caveats
Never use DOACs (dabigatran, rivaroxaban, apixaban) for mechanical valve thromboprophylaxis—the RE-ALIGN trial showed increased thromboembolic and bleeding complications with dabigatran versus warfarin. 1
The benefit of aspirin addition to warfarin must be weighed against bleeding risk, particularly in elderly patients or those with GI bleeding history. 1
Patients with mitral bioprostheses have higher thromboembolic risk than aortic bioprostheses and warrant more aggressive anticoagulation consideration. 1