The Spanish Monostrut Study Group: a ten-year experience with 8,599 implants

Major hemorrhagic and thromboembolic complications in patients with mechanical heart valves receiving oral anticoagulant therapy

INTRODUCTION

Patients with mechanical heart valve prostheses are obligated to receive lifelong oral anticoagulant therapy to prevent thromboembolic complications; however, this treatment is associated with an increased risk of bleeding. The aim of this study was to evaluate the frequency of major hemorrhagic and thromboembolic complications in patients with mechanical heart valves who received oral anticoagulant therapy.

MATERIALS AND METHODS

The analysis involved 225 patients who underwent successful surgery in 2000; the mean (+/-SD) follow-up period was 43.3 +/- 9.2 months. Aortic, mitral, and double valve replacement was performed in 128 (56.7%), 70 (31.1%), and 27 (12.1%) of the patients, respectively. There were 128 men (57.3%), and the mean patient age was 57.9 +/- 18.8 years. The following data were assessed: rate of major hemorrhagic and thromboembolic complications, frequency of international normalized ratio (INR) rate measurements, and percentage of results within the therapeutic range.

RESULTS

Major hemorrhagic and thromboembolic complications occurred in 25 patients (11.1%). Seventeen patients (7.5%) survived, and 8 (3.6%) died of the complications. Major hemorrhagic and thromboembolic complications occurred in 17 patients (7.6%) and 8 patients (3.6%), respectively. The mean time between sequential measurements was 4.3 +/- 3.0 weeks, and of all the INR values collected, 42.4% were within, 31.3% were below, and 26.3% were above the target ranges.

CONCLUSIONS

Patients with a mechanical heart valve prosthesis receiving acenocoumarol are susceptible to major hemorrhagic and thromboembolic complications, some of which lead to death. Despite the danger related to these complications, patients receiving anticoagulant therapy still have difficulty achieving INR values within the therapeutic range.

Mechanical heart valve performance in a pulsatile pediatric ventricular assist device

A pulsatile pediatric ventricular assist device with a dynamic stroke volume of 12 ml is currently under development at the Pennsylvania State University. A monoleaflet valve (Björk-Shiley Monostrut) and a bileaflet valve (CPHV, CarboMedics Prosthetic Heart Valve) were examined in this study. A high-speed video and data acquisition system was used to simultaneously record video images, pressure waveforms, and flow waveforms for an array of in vitro test conditions that varied heart rate and systolic duration. The CPHV in both the horizontal and vertical orientations have larger regurgitant volumes than the Monostrut valves at all operating conditions in both the inlet and outlet positions. However, the CPHV has higher stroke volumes and cardiac outputs than the Monostrut valve at higher heart rates and longer systolic durations. In addition, the hydrodynamic performance of the Monostrut valve is more sensitive to changes in operating conditions for the pulsatile pediatric ventricular assist device than the CPHV in both orientations. Additional testing is under way to identify the optimal operating conditions for each type of valve.

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 optimal intensity of vitamin K antagonists in patients with mechanical heart valves: a meta-analysis

OBJECTIVES

The purpose of this study was to compare two different intensities of vitamin K antagonists (VKA) among patients with mechanical heart valves using meta-analytic techniques.

BACKGROUND

Patients with mechanical heart valves are at increased risk for valve thrombosis and systemic embolism, which can be reduced by VKA. The range of optimal intensity of VKA is still a matter of debate.

METHODS

A computerized search in the PubMed database was made for relevant articles. A meta-analysis was performed of all eligible studies with data on the incidences of thromboembolic and bleeding complications in patients with mechanical heart valve prostheses during different intensities of VKA therapy. The studies were classified into low-intensity VKA therapy (mean target international normalized ratio [INR] of 3.0 or lower) or high-intensity VKA therapy (mean target INR above 3.0).

RESULTS

Thirty-five eligible studies were identified, including in total 23,145 patients, who were studied for 108,792 patient-years. For patients with an aortic valve, high intensity resulted in a lower incidence of thromboembolic events (risk ratio [RR] = 0.73, p < 0.0001); however, the incidence of bleeding was increased (RR = 1.23, p < 0.0001). In the mitral valve group, the incidence rate for thromboembolism was lower in the high-intensity group (RR = 0.74, p < 0.0001), without a significantly increased bleeding incidence (RR = 1.08, p = 0.0524). The total number of thromboembolic and bleeding events was decreased in the high-intensity group compared with low-intensity VKA therapy for both aortic and mitral valve prostheses (RR = 0.94 [p = 0.0067] and 0.84 [p < 0.0001]), respectively.

CONCLUSIONS

This meta-analysis shows that both aortic and mitral valves will benefit from a treatment strategy with a target INR higher than 3.0.

Mechanical heart valves: 50 years of evolution

The past 50 years have witnessed remarkable progress in the development of safe, hemodynamically favorable mechanical heart valves. Starr-Edwards aortic and mitral ball valves introduced in the mid-1960s, continue to be used successfully worldwide. More than 100,000 Omniscience and Omnicarbon tilting-disc valves have been implanted since 1978 with essentially no mechanical failure; similar results have been obtained with more than 300,000 Hall-Kaster and Medtronic-Hall tilting-disc valves over the past 25 years. Pyrolytic carbon, originally used to encapsulate nuclear fuel rods, has been adapted for the fabrication of discs, leaflets and the housings for more than 2 million mechanical valves. The St. Jude bileaflet valves, totally fabricated from pyrolytic carbon, have remained virtually unchanged in design since their introduction in 1977. More than 1.3 million of these valves have been implanted worldwide with virtually no reported failures of the carbon leaflets or housings. Similarly, pyrolytic carbon bileaflet Carbomedics valves have been implanted in more than 500,000 patients since 1986. Now, 50 years after Dr Gibbon's seminal achievement, patients with debilitating valve disease can have elective valve replacement (mechanical or tissue) with an operative mortality approaching 1% to 2% and a low lifetime complication rate.

Antithrombotic therapy in patients with mechanical and biological prosthetic heart valves

1. Permanent therapy with oral anticoagulants offers the most consistent protection in patients with mechanical heart valves. 2. Antiplatelet agents alone do not consistently protect patients with mechanical prosthetic heart valves, including patients in sinus rhythm with St. Jude Medical valves in the aortic position. 3. Levels of oral anticoagulants that prolong the INR to 2.0 to 3.0 appear satisfactory for patients with St. Jude Medical bileaflet and Medtronic-Hall tilting disk mechanical valves in the aortic position, provided they are in sinus rhythm and the left atrium is not enlarged. Presumably, this is also true for the CarboMedics bileaflet valve, based on the observation of no clinically important difference in the rate of systemic embolism with this valve and the St. Jude Medical bileaflet valve. 4. Levels of oral anticoagulants that prolong the INR to 2.5 to 3.5 are satisfactory for tilting disk valves and bileaflet prosthetic valves in the mitral position. 5. Experience in patients with caged ball valves who had prothrombin time ratios reported in terms of the INR is sparse, because few such valves have been inserted in recent years. The number of surviving patients with caged ball valves continues to decrease. It has been suggested that the most advantageous level of the INR 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, 3.0-4.5. The problem is self-limited, however, because few such valves are being inserted. 6. In patients with mechanical heart valves, aspirin, in addition to oral anticoagulants, has been shown to diminish the frequency of thromboemboli. The risk of bleeding is somewhat increased if the INR is 2.0 to 3.0 or 2.5 to 3.5. However, if the INR is 3.0 to 4.5, the risk of bleeding becomes excessive with aspirin. There are no investigations in which aspirin 80 mg/d in combination with oral anticoagulants was evaluated. 7. Data are insufficient to recommend dipyridamole over low doses of aspirin in combination with warfarin. Whether dipyridamole plus aspirin is more effective than aspirin alone when used with warfarin is undetermined. 8. 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 operation. 9. Among patients with bioprosthetic valves in the mitral position, oral anticoagulants at an INR of 2.0 to 2.3 were as effective as an INR of 2.5 to 4.0 and were associated with fewer bleeding complications during the first 3 months after operation.10. Aspirin may reduce the long-term frequency of thromboembolism in patients with bioprosthetic valves.

Long-term clinical experience with the Omnicarbon prosthetic valve

BACKGROUND

From February 1985 to December 1994, 781 Omnicarbon valve prostheses were implanted in 647 patients. These were 357 male and 290 female patients with a mean age of 53.5+/-10.5 years (range, 4 to 78 years). Before operation, 81% of the patients were in New York Heart Association class III or IV, 16% were in class II, and only 3% were in class I.

METHODS

There were 227 aortic valve replacements (AVR) (35%), 286 mitral valve replacements (MVR) (44%), and 134 double-valve replacements (DVR) (21%) (AVR + MVR). Follow-up was 96.3% complete and consisted of 2,746 patient-years (mean follow-up, 4.6 years, and maximum follow-up, 10.7 years).

RESULTS

Hospital mortality rates were 7.0% for AVR, 8.0% for MVR, and 8.2% for DVR. The annualized rate of anticoagulant-related hemorrhage was 0.8% per patient-year, and thromboembolism occurred at a rate of 0.7% per patient-year. No structural failure was observed during 10-year follow-up. Twenty-one instances of nonstructural dysfunction (two, pannus growth, and 19, dehiscence) of the Omnicarbon valve occurred in 20 patients, an incidence of 0.8% per patient-year. Hemolytic anemia was observed only in the presence of valvular dehiscence (6 of 19). Eight patients (0.3% per patient-year) had development of prosthetic valve endocarditis (4, AVR; 2, MVR; and 2 DVR). At the end of 10 years of follow-up, 91% of the survivors were in New York Heart Association class I or II. The overall survival rate at 10 years was 82.5%+/-2.6% (85.0%+/-3.9%, AVR; 81.0%+/-4.1%, MVR; and 82.5%+/-2.6%, DVR). Considering only valve-related deaths, the survival rate at 10 years was 91.9%+/-2.4% (90.0%+/-2.7%, AVR; 93.1%+/-3.8%, MVR; and 90.0%+/-1.8%, DVR).

CONCLUSIONS

Clinical results over a 10-year follow-up are excellent with the Omnicarbon prosthesis.

Thromboembolism and mechanical heart valves: a randomized study revisited

BACKGROUND

This study was designed to revise and substantiate previous inferences, based on short-term follow-up, about differences in the incidence of anticoagulant-related events after heart valve replacement among patients who had been randomly assigned to receive either a Björk-Shiley, Edwards-Duromedics, or Medtronic-Hall mechanical heart valve prosthesis.

METHODS

Intermediate-term follow-up to January 1995 was completed in 418 of 419 patients randomized to receive one of three types of heart valve prostheses between January 1982 and January 1987. Median follow-up was 98.5 months. Multivariable analysis in the hazard function domain was performed to identify factors that influenced the incidence of time-related thromboembolism and bleeding. These findings were compared with those made previously after a median follow-up of 37.5 months.

RESULTS

No differences were found among the three prostheses in rates of anticoagulant-related hemorrhage. However, the incidence of thromboembolism was higher after mitral valve replacement among patients who had received the Medtronic-Hall prosthesis (linearized rate, 5.4% per patient year; 70% confidence interval, 4.0% to 7.1%), compared with Edwards-Duromedics (1.3%; 70% confidence interval, 0.4% to 3.0%) and Björk-Shiley prostheses (1.2%; 70% confidence interval, 0.6% to 2.2%).

CONCLUSIONS

At long-term follow-up, in contrast to the findings at short-term follow-up, patients with either Björk-Shiley or Edwards-Duromedics prostheses had low rates of thromboembolism, whereas higher rates occurred in patients with a Medtronic-Hall prosthesis in the mitral position.