Frequency of prosthetic valve-related complications with very low level warfarin anticoagulation combined with dipyridamole after valve replacement using St. Jude Medical prostheses

Anticoagulation and Antiplatelet Strategies After On-X Mechanical Aortic Valve Replacement

BACKGROUND

The burden oral anticoagulation is a limitation of mechanical valve prostheses.

OBJECTIVES

The aim of this study was to test whether patients could be safely managed with dual-antiplatelet therapy (DAPT) (aspirin 325 mg and clopidogrel 75 mg) or lower warfarin after On-X mechanical aortic valve replacement (mAVR).

METHODS

PROACT (Prospective Randomized On-X Anticoagulation Trial) (n = 576) is a multicenter (41 sites) noninferiority trial. From June 2006 through February 2014, 201 patients ≥18 years of age without thromboembolic risk factors undergoing mAVR were randomized to receive DAPT (n = 99) or standard warfarin plus aspirin (n = 102) 3 months after mAVR (low-risk arm). From June 2006 through October 2009, 375 patients with 1 or more thromboembolic risk factors were also randomized to lower intensity warfarin plus aspirin (international normalized ratio 1.5 to 2.0; n = 185) or standard warfarin plus aspirin (international normalized ratio 2.0 to 3.0; n = 190) 3 months after mAVR (high-risk arm).

RESULTS

The low-risk arm was terminated for excess cerebral thromboembolic events (3.12% per patient-year vs. 0.29% per patient-year, p = 0.02) in the DAPT group at up to 8.8-year follow-up (631.6 patient-years), with no differences in bleeding or all-cause mortality. High-risk arm patients experienced significantly lower major (1.59% per patient-year vs. 3.94% per patient-year, p = 0.002) and minor (1.27% per patient-year vs. 3.49% per patient-year, p = 0.002) bleeding up to 8.7-year follow-up (2,035.2 patient-years), with no differences in thromboembolism (0.42% per patient-year vs. 0.09% per patient-year, p = 0.20) and all-cause mortality.

CONCLUSIONS

DAPT was associated with higher rates of thromboembolism and valve thrombosis compared with control in the low-risk arm. International normalized ratios were safely maintained at 1.5 to 2.0 in high-risk patients, without differences in mortality or thromboembolic complications. (Randomized On-X Anticoagulation Trial [PROACT]; NCT00291525).

Antithrombotic Therapy in Valvular Heart Disease—Native and Prosthetic

This chapter about antithrombotic therapy in native and prosthetic valvular heart disease is part of the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy: Evidence Based Guidelines. Grade 1 recommendations are strong and indicate that the benefits do, or do not, outweigh risks, burden, and costs. Grade 2 suggests that individual patients' values may lead to different choices (for a full understanding of the grading see Guyatt et al, CHEST 2004; 126:179S-187S). Among the key recommendations in this chapter are the following: For patients with rheumatic mitral valve disease and atrial fibrillation (AF), or a history of previous systemic embolism, we recommend long-term oral anticoagulant (OAC) therapy (target international normalized ratio [INR], 2.5; range, 2.0 to 3.0) [Grade 1C+]. For patients with rheumatic mitral valve disease with AF or a history of systemic embolism who suffer systemic embolism while receiving OACs at a therapeutic INR, we recommend adding aspirin, 75 to 100 mg/d (Grade 1C). For those patients unable to take aspirin, we recommend adding dipyridamole, 400 mg/d, or clopidogrel (Grade 1C). In people with mitral valve prolapse (MVP) without history of systemic embolism, unexplained transient ischemic attacks (TIAs), or AF, we recommended against any antithrombotic therapy (Grade 1C). In patients with MVP and documented but unexplained TIAs, we recommend long-term aspirin therapy, 50 to 162 mg/d (Grade 1A). For all patients with mechanical prosthetic heart valves, we recommend vitamin K antagonists (Grade 1C+). For patients with a St. Jude Medical (St. Paul, MN) bileaflet valve in the aortic position, we recommend a target INR of 2.5 (range, 2.0 to 3.0) [Grade 1A]. For patients with tilting disk valves and bileaflet mechanical valves in the mitral position, we recommend a target INR of 3.0 (range, 2.5 to 3.5) [Grade 1C+]. For patients with caged ball or caged disk valves, we suggest a target INR of 3.0 (range, 2.5 to 3.5) in combination with aspirin, 75 to 100 mg/d (Grade 2A). For patients with bioprosthetic valves, we recommend vitamin K antagonists with a target INR of 2.5 (range, 2.0 to 3.0) for the first 3 months after valve insertion in the mitral position (Grade 1C+) and in the aortic position (Grade 2C). For patients with bioprosthetic valves who are in sinus rhythm and do not have AF, we recommend long-term (> 3 months) therapy with aspirin, 75 to 100 mg/d (Grade 1C+).

The effects of lower intensity anticoagulation therapy on coagulation system in patients with mechanical prosthetic valves

To evaluate the effect of lower intensity anticoagulation therapy in patients with mechanical prosthetic valves, laboratory-based hematological assays including prothrombin time (PT), activity of factor X, antithrombin III (AT III), D-dimer, fibrinogen (Fg) and platel et al pha-granular membrane protein (GMP-140) were performed in 65 patients who had been on warfarin treatment for over one month. The patients were assigned to 3 groups on the basis of their International Normalized Ratios (INR), ranging from 2.00 to 2.50; 2.51 to 3.00; 3.01 to 4.50, respectively. The results showed that the D-dimer, Fg, GMP-140 levels were higher after mechanical valve replacement than those before operation, indicating the activation of coagulation and fibrinolysis system and the damage of platelets. Lower intensity anticoagulation therapy (INR 2.00 to 2.50) could effectively inhibit the activity of factor X and increase the level of AT III. There were no appreciable differences among D-dimer, Fg, GMP-140 and AT III in the 3 anticoagulation intensity groups. These results suggest that in patients with new generation mechanical prosthetic valves, target anticoagulation level (INR 2.00 to 2.50) may result in good protection from thrombo-embolism.

Anticoagulant therapy in Japanese patients with mechanical mitral valves

There are no guidelines for the optimal therapeutic range of anticoagulant therapy in Japanese patients with mechanical heart valves. A total of 214 patients were followed retrospectively after mitral mechanical valve replacement (mean duration of follow-up, 4.8 years; total duration of follow-up, 1,027 patient-years). The target range of the international normalized ratio (INR) for oral anticoagulation was between 1.5 and 2.5. For all patients 10,416 measurements of the INR were obtained during the follow-up period and approximately 76% of the intensity measurements were within the target range. Thromboembolism occurred in 8 patients (0.8 per 100 patient-years) and major bleeding in 5 patients (0.5 per 100 patient-years). There was no correlation between the distribution of the INR and the occurrence of thromboembolic or bleeding complications. In the univariate analysis of the various risk factors, patients who had a tilting valve or did not receive antiplatelet therapy had an increased risk of thromboembolism. However, there were no risk factors with respect to bleeding complications. A target range of 1.5 to 2.5 INR appears to be the optimal range and is safe for thromboembolism or bleeding complications. Thromboembolism may be reduced by additional antiplatelet therapy, and a tilting valve needs more intense anticoagulation.

Bileaflet mechanical prostheses performance in mitral position

OBJECTIVE

The experience with the Carbomedics (CM) and the St. Jude Medical (SJM) bileaflet mechanical prostheses was evaluated to determine thromboembolic and hemorrhagic complications and predictive risk factors.

METHODS

From 1989 to 1994, a total of 625 patients had mitral valve replacement (CM, 240; SJM, 385); 32.5% (203), concomitant procedures and 32.8% (205), previous cardiac surgery, primarily valve replacement procedures.

RESULTS

The pre-operative variables did not distinguish the populations, except for previous surgery CM 37.9% and SJM 29.6% (P < 0.05). The pre-operative variables (type of prostheses, cardiac rhythm, coronary artery bypass, NYHA III/IV, advancing age, gender, urgency status and previous surgery) were not predictive of overall thromboembolism (TE), major TE, minor TE, prosthesis thrombosis and hemorrhage (P not significant; P = NS). The linearized rate of total TE events for overall MVR was 5.0%/patient-year (CM 4.4; SJM 5.4). The < or = 30 day major crude rate was 0.44%, while the > 30 day late major event rate was 2.0%/patient-year. Of the total TE events 91% of < or = 30 days and 75%, > 30 days had an INR < 2.5 at or immediately prior to the event. The thrombosis rate (included in TE events) was 0.63%/patient-year (ten events, four managed successfully with thrombolysis, five successfully with reoperation, and one fatality identified at autopsy). The freedom, at 5 years, from major/fatal TE, thrombosis and hemorrhage from anticoagulation was 88.2%, and 89.5% exclusive of early events.

CONCLUSIONS

This non-randomized prospective observational evaluation of the CarboMedics and St. Jude Medical prostheses has not revealed any differentiation in performance of the prostheses. The study serves as a single institution experience with the potential for future comparative evaluation.

Antithrombotic therapy in patients with mechanical and biological prosthetic heart valves

Permanent therapy with oral anticoagulants offers the most consistent protection in patients with mechanical heart valves. Antiplatelet agents alone do not consistently protect patients with mechanical prosthetic heart valves, including patients in sinus rhythm with St. Jude valves in the aortic position. Levels of oral anticoagulants that prolong the INR to 2.0 to 3.0 appear satisfactory for patients with bileaflet mechanical valves in the aortic position, provided they are in sinus rhythm and the left atrium is not enlarged. Oral anticoagulant levels that prolong the INR to 2.5 to 3.2 are satisfactory for patients with bileaflet mechanical aortic valves and atrial fibrillation. Oral anticoagulant levels that prolong the INR to 2.5 to 3.5 are satisfactory for tilting disk valves and bileaflet prosthetic valves in the mitral position. Experience is sparse in patients with caged ball valves who had prothrombin time ratios reported in terms of INR. It has been suggested that the most advantageous INR level in patients with caged ball or caged disk valves should be as high as 4.0 to 4.9. However, others have shown a high rate of major hemorrhage with an INR that is even somewhat lower (3.0 to 4.5). The problem is self-limited, however, because few such valves are being inserted. Aspirin, in addition to oral anticoagulants, in patients with mechanical heart valves has been shown to diminish the frequency of thromboemboli. The risk of bleeding may not be increased if the INR is low. A low rate of both thromboemboli and bleeding has been shown with an INR of 2.5 to 3.5 in combination with aspirin at a dose of 100 mg/d. There are no investigations in which an aspirin dose of 81 mg/d in combination with oral anticoagulants was evaluated. Dipyripdamole may be effective in reducing the rate of thromboemboli without increasing the rate of bleeding, but data are insufficient to recommend dipyridamole over low doses of aspirin. Patients with bioprosthetic valves in the mitral position, as well as patients with bioprosthetic valves in the aortic position, may be at risk for thromboemboli during the first 3 months after surgery. Among patients during the first 3 months after surgery with bioprosthetic valves in the mitral position, oral anticoagulants administered at an INR of 2.0 to 2.3 were as effective as at an INR of 2.5 to 4.5: additionally, fewer bleeding complications were seen.

Long-term follow-up of St. Jude Medical prosthesis in a young rheumatic population using low-level warfarin anticoagulation: an analysis of the temporal distribution of causes of death

This study assesses the long-term (mean 52+/-24 months) performance of the St. Jude Medical (SJM) valve in 200 young (mean age 31+/-13 years) rheumatic patients on low-level warfarin anticoagulation combined with dipyridamole. Follow-up was 95% complete and comprised 867 patient-years. There were 33 deaths (3.8%/patient-year). Death was valve related in 12 cases and due to left ventricular dysfunction in 10. Death due to left ventricular dysfunction occurred earlier after surgery than death due to other causes (10+/-7 vs 29+/-18 months, p <0.005); these patients had larger preoperative left ventricular dimensions than the rest of the group (end-systolic diameter 51+/-13 vs 37+/-16 mm, end-diastolic diameter 66+/-13 vs 50+/-19 mm, p = 0.006). Actuarial probability of survival was 81% at 86 months and probability of event-free survival was 71%. The median international normalized ratio was 1.88+/-0.54. Thromboembolism (13 events) occurred at a linearized rate of 1.5%/patient-year. There were 11 major bleeding episodes (1.3%/patient-year), 4 cases of prosthetic valve endocarditis (0.8%/patient-year), and 12 paraprosthetic leaks (1.4%/patient-year). No valve obstructions or reoperations occurred. Thus, the SJM valve performs well on low-level anticoagulation combined with dipyridamole. Left ventricular dysfunction was a common cause of death in the early postoperative period.