Aspirin or Coumadin as the drug of choice for valve replacement with porcine bioprosthesis

Long-term Outcomes and Anticoagulation in Mitral Valve Surgery-A Report From The Society of Thoracic Surgeons Database

BACKGROUND

Anticoagulation after bioprosthetic mitral valve (MV) replacement (BMVR) and repair (MVrep) is controversial. We explore outcomes among BMVR and MVrep patients in The Society of Thoracic Surgeons Adult Cardiac Surgery Database based on discharge anticoagulation status.

METHODS

BMVR and MVrep patients aged ≥65 years in The Society of Thoracic Surgeons Adult Cardiac Surgery Database were linked to the Centers for Medicare and Medicaid Services claims database. Long-term mortality, ischemic stroke, bleeding, and a composite of the primary end points were compared as a function of anticoagulation. Hazard ratios (HRs) were calculated using multivariable Cox regression.

RESULTS

A total of 26,199 BMVR and MVrep patients were linked to the Centers for Medicare and Medicaid Services database; of these, 44%, 4%, and 52% were discharged on warfarin, non-vitamin K-dependent anticoagulant (NOAC), and no anticoagulation (no-AC; reference), respectively. Warfarin was associated with increased bleeding in the overall study cohort (HR, 1.38; 95% CI 1.26-1.52) and in the BMVR (HR, 1.32; 95% CI, 1.13-1.55) and MVrep subcohorts (HR, 1.42; 95% CI, 1.26-1.60). Warfarin was associated with decreased mortality only among BMVR patients (HR, 0.87; 95% CI, 0.79-0.96). Stroke and the composite outcome did not differ across cohorts with warfarin. NOAC use was associated with increased mortality (HR, 1.33; 95% CI 1.11-1.59), bleeding (HR, 1.37; 95% CI, 1.07-1.74), and the composite outcome (HR, 1.26; 95% CI, 1.08-1.47).

CONCLUSIONS

Anticoagulation was used in fewer than half of mitral valve operations. In MVrep patients, warfarin was associated with increased bleeding and was not protective against stroke or mortality. In BMVR patients, warfarin was associated with a modest survival benefit, increased bleeding, and equivalent stroke risk. NOAC was associated with increased adverse outcomes.

Plasminogen activators and ischemic stroke: conditions for acute delivery

Appropriate acute treatment with plasminogen activators (PAs) can significantly increase the probability of minimal or no disability in selected ischemic stroke patients. There is a great deal of evidence showing that intravenous recombinant tissue PAs (rt-PA) infusion accomplishes this goal, recanalization with other PAs has also been demonstrated in the development of this treatment. Recanalization of symptomatic, documented carotid or vertebrobasilar arterial territory occlusions have also been achieved by local intra-arterial PA delivery, although only a single prospective double-blinded randomized placebo-controlled study has been reported. The increase in intracerebral hemorrhage with these agents by either delivery approach underscores the need for careful patient selection, dose-appropriate safety and efficacy, proper clinical trial design, and an understanding of the evolution of cerebral tissue injury due to focal ischemia. Principles underlying the evolution of focal ischemia have been expanded by experience with acute PA intervention. Several questions remain open that concern the manner in which PAs can be applied acutely in ischemic stroke and how injury development can be limited.

Antiplatelet therapy in patients receiving aortic bioprostheses: A report of clinical and instrumental safety

OBJECTIVE

The main advantage of bioprostheses, avoidance of anticoagulant therapy, is compromised during the early postoperative period; in fact, warfarin is often administered during the first 3 postoperative months.

METHODS

We analyzed 250 patients undergoing tissue aortic valve replacement between January 2002 and December 2005. The patients received either aspirin (group 1) or oral anticoagulation (group 2) during the first 3 months. In a subgroup of these patients, we investigated the possible presence of clinically silent microembolization by means of transcranial Doppler for microembolic signal detection.

RESULTS

Thirty-day mortality was 0%. No major neurologic events occurred. Two episodes of bleeding were observed in both groups. Follow-up time was 24 +/- 14 months. Overall late mortality rate was 0.8% in group 1 versus 12% (mainly cancer related) in group 2. In group 2, 2 deaths were due to major ischemic neurologic events; overall, 3 major neurologic episodes occurred (international normalized ratio was within therapeutic range). There were no neurologic events in group 1 (P = .12). Stroke-free survival did not reach statistical significance between the 2 groups. Transcranial Doppler was performed after a mean interval of 55 +/- 19 days, with no detection of microembolic signals in patients receiving either aspirin or warfarin. There were no episodes of bleeding or neurologic events.

CONCLUSIONS

Aspirin therapy appears to be the appropriate response to both cardiac surgeons' and patients' needs in the early postoperative course after aortic valve replacement with tissue valves, demonstrating adequate antithromboembolic efficacy with no added risk for bleeding as well as ease of administration.

Bioprosthetic mitral valve thrombosis: clinical profile, transesophageal echocardiographic features, and follow-up after anticoagulant therapy

Cardiac bioprosthetic valve thrombosis is frequently found on pathologic examination, but preoperative diagnosis is rarely performed. Four hundred six patients with mitral porcine xenograft bioprostheses were examined by transthoracic echocardiography. Transesophageal echocardiography (TEE) was performed in 161 of the patients, with clinical or echocardiographic criteria of prosthetic malfunction. Fairly homogeneous and echodense masses, attached to the ventricular surface of the mitral bioprosthetic cusps, were detected by TEE in 15 patients. Only 10 patients, in whom diagnosis of bioprosthetic thrombosis was confirmed, are included in this study. After TEE, two patients underwent prosthetic replacement and eight patients received anticoagulants. A new TEE was performed 85.6 +/- 29.8 days after anticoagulation in these eight patients. Clinical follow-up was continued for 13.6 +/- 8.6 months, and one additional patient underwent surgery during the follow-up. Pathologic examination of removed grafts (three cases) identified these masses as being thrombotic tissue. TEE examination after therapeutic anticoagulation demonstrated complete disappearance of the echogenic masses on bioprosthetic cusps and normal mobility of all leaflets in six cases. In the other two cases, cusp masses were notably reduced, but partially restrictive mobility of affected leaflets persisted, suggesting incomplete resolution of thrombi. Mitral valve prosthetic mean gradient decreased from 11.8 +/- 4.5 to 7.6 +/- 3.7 mm Hg (p < 0.001), and mitral valve area increased from 1.13 +/- 0.3 to 1.72 +/- 0.6 cm2 (p < 0.001). Long-term symptomatic improvement after anticoagulation was obtained in seven patients. Thus this study shows that mitral bioprosthetic thrombosis is a relatively frequent cause of valve dysfunction, TEE is useful for detecting thrombus in relation to mitral bioprosthetic valves, and oral anticoagulation is effective in resolving thrombosis on bioprostheses.

The Hancock II bioprosthesis at ten years

The Hancock II bioprosthesis was used for heart valve replacement in 843 patients from 1982 to 1993. Aortic valve replacement (AVR) was performed in 536 patients, mitral valve replacement (MVR) in 250, and aortic and mitral valve replacement (DVR) in 57. The mean age was 64 +/- 12 years. Before operation, 80% of the patients were in New York Heart Association functional class III or IV; approximately one-third of the patients had coronary artery disease, and 60 patients had ascending aorta aneurysm. There were 47 operative deaths (AVR, 4%; MVR, 7%; DVR, 10%) and 147 late deaths. Follow-up was complete in 98.6% of the patients and extended from 3 to 140 months (mean, 59 months). At the last follow-up, 84% of the patients were in New York Heart Association class I or II. The actuarial survival at 10 years was 63% +/- 4% for AVR, 55% +/- 5% for MVR, and 53% +/- 9% for DVR. At the end of 10 years, the freedom from thromboembolic complications was 80% +/- 4% for AVR, 88% +/- 3% for MVR, and 86% +/- 5% for DVR; the freedom from endocarditis was 95% +/- 2% for AVR, 96% +/- 1% for MVR, and 87% +/- 5% for DVR; the freedom from primary tissue failure was 92% +/- 3% for AVR, 81% +/- 6% for MVR, and 65% +/- 16% for DVR; and the freedom from reoperation was 89% +/- 2% for AVR, 81% +/- 6% for MVR, and 61% +/- 15% for DVR. The durability of this bioprosthetic valve was affected by the patient's age and by the position where it was implanted. The clinical results of the Hancock II bioprosthesis at 10 years are comparable to those of other current porcine and pericardial valves.

Antithrombotic treatment of cerebrovascular disease

The most common type of cerebrovascular disease is ischaemia or infarction from atherothrombosis or cardiac embolism. Antithrombotic treatment with an antiplatelet agent or anticoagulant assumes a prior clinical classification into categories of transient ischaemic attack (TIA) or minor stroke, acute partial stable stroke, stroke-in-progression, and completed stroke. Aspirin reduces the risk of stroke, myocardial infarction, and death after TIA or minor stroke secondary to atherothrombosis. Aspirin is effective in both sexes at a dose of 300 or 1200 mg/day. Ticlopidine (500 mg/day), a new antiplatelet agent, is more effective than aspirin in preventing stroke and death in patients with TIA or minor stroke. Ticlopidine (500 mg/day) is effective in preventing recurrent stroke, myocardial infarction, or vascular death in patients with completed stroke. Aspirin has not been directly shown to be effective after completed stroke. No clear evidence exists for the use of anticoagulants in atherothrombotic cerebral vascular disease in patients presenting with TIA or minor stroke, acute partial stable stroke, stroke-in-progression, or completed stroke. Anticoagulation for rheumatic valvular heart disease is effective in preventing recurrent embolism. Long-term anticoagulation of patients with mechanical prosthetic valves protects against initial embolism and prevents recurrent embolism. The addition of aspirin (500-1000 mg/day) to warfarin reduces the rate of cerebral embolism from mechanical prosthetic heart valves but is associated with increased bleeding. The addition of dipyridamole (400 mg/day) to warfarin may be more effective than aspirin in reducing the rate of cerebral embolism from mechanical prosthetic heart valves and has fewer bleeding side-effects. Anticoagulation during the hospital phase of myocardial infarction reduces the incidence of systemic embolism/stroke. Long-term anticoagulation of patients after the hospital phase of myocardial infarction reduces the incidence of systemic embolism/stroke, recurrent myocardial infarction and death. Prophylactic anticoagulant treatment of patients with non-valvular atrial fibrillation reduces the incidence of embolism, but the optimal duration of treatment is not known. Immediate anticoagulation of patients with completed cardioembolic stroke is safe and effective in preventing recurrent embolism.

Leukocytes, platelets, and surface microstructure of spontaneously degenerated porcine bioprosthetic valves

The microstructure of 33 spontaneously degenerated porcine bioprosthetic valves was assessed by scanning electron microscopy in order to gather insight regarding the degenerative process. Twenty-four mitral and 9 aortic valves were removed from 32 patients. The duration of insertion was 7.7 +/- 2.4 years (mean +/- SD). All valves showed denudation of endothelial cells and exposure of the subendothelial fibrous tissue. Fibroblastlike cells were occasionally seen. Platelet deposits were observed on 22 of 33 valves (67%). Leukocytes were observed on the surface of 27 of 33 valves (82%). Mononuclear leukocytes were the most common category of cells (66%). Crystalline material was present on the surface of some leukocytes, suggesting that they may serve as a nidus for calcification. Transmission electron microscopy showed leukocytes in the process of phagocytizing collagen fibers. Macrophages, by exerting their scavenger function seem to contribute to destruction of the collagen framework of the valves. Whether the observed lymphocytes and plasma cells reflect an immunological involvement is unclear.

Thrombotic and bleeding complications of prosthetic heart valves

A review of articles published since 1979 indicates that thrombotic and bleeding complications account for about 50% of valve-related complications in patients with bioprosthetic aortic and mitral valves and for approximately 75% of the complications in patients with mechanical valves. Although compromised by lack of standard definitions and by variability in reporting and follow-up, the data suggest that the linearized rate of both thrombotic and bleeding complications in patients with aortic bioprostheses is approximately half that for aortic mechanical prostheses (2% versus 4%), but is approximately equal for both bioprostheses and mechanical valves in the mitral position (approximately 4%), and for mechanical and bioprosthetic aortic and mitral valves in combination. However, linearized rates for fatal thrombotic and bleeding events are two to four times higher in patients with mechanical prostheses. The adequacy of warfarin anticoagulation is the most important factor affecting thrombotic and bleeding complications in patients with mechanical valves and over shadows the dubious importance of other phenomena such as atrial fibrillation and left atrial thrombus. Short-term warfarin anticoagulation or the use of long-term platelet inhibitors, or both, do not appear to reduce the incidence of thrombotic complications in patients with aortic bioprostheses but increase bleeding. For mitral bioprostheses, the postoperative use of warfarin for three months or aspirin indefinitely is as effective in preventing thromboembolism as long-term warfarin. Acute prosthetic valve endocarditis is associated with a 13 to 40% incidence of thrombotic complications. Likewise, the recurrence rate of cerebral emboli is high (20-30%) in patients with prosthetic valves who are not anticoagulated. Bioprostheses are strongly preferred for women who wish to bear children; fetal wastage occurs in 25 to 30% of pregnant women with mechanical heart valves who receive either warfarin or heparin, or a combination of the two. Heparin, however, greatly increases the risk of maternal bleeding. In children, the efficacy of platelet inhibitors without warfarin anticoagulation is unproven; nearly all serious strokes occur when warfarin is omitted; and permanent disability from warfarin-related bleeding is rare. All prosthetic cardiac valves initiate coagulation and affect the dynamic equilibrium between activated procoagulants and endogenous anticoagulants. Warfarin is the only available oral exogenous anticoagulant.(ABSTRACT TRUNCATED AT 400 WORDS)

Thromboembolism in patients with aortic porcine bioprostheses

Thromboembolism was prospectively studied in 215 patients who survived aortic valve replacement with porcine bioprostheses. All patients were anticoagulated with warfarin sodium during the first 3 postoperative months. Thereafter, 80 patients received aspirin (325 or 650 mg per day) and 135 received no antiplatelet or anticoagulant drugs. The two groups of patients were similar. Thromboembolic complications were carefully searched for during the follow-up interviews. Patients were removed from the study after a thromboembolic event unless there was no change in their management. The follow-up ranged from 6 to 80 months (mean, 36 months). The linearized thromboembolic rate in patients on a regimen of aspirin was 1.3% per patient-year and in patients not taking aspirin, 5.2% per patient-year (p less than 0.02). Replacement of the ascending aorta and patch enlargement of the aortic annulus with a Teflon graft were identified as significant risk factors for thromboembolism in patients with aortic porcine bioprostheses. These findings indicate that patients with aortic porcine bioprostheses should receive aspirin, especially if they also had replacement of the ascending aorta or patch enlargement of the aortic annulus with a Teflon graft.

Thromboembolism and bleeding after mitral valve replacement with porcine valves: influence of thromboembolic risk factors

The risk of postoperative thromboembolism (PTE), anticoagulant related hemorrhage (ARH), and the influence of thromboembolic risk factors ( TERF ) were assessed retrospectively in 206 unselected patients undergoing mitral valve replacement (MVR) with porcine xenobioprotheses ( PXBP ). Other aims were to identify the "high-risk" group with respect to PTE and to assess the effectiveness of long-term anticoagulant therapy (AT) in this subset, as well as to elucidate the most adequate method of AT and ascertain if AT is strictly necessary in patients undergoing MVR with PXBP . Patients were divided in two groups: Group I (N = 115) received long-term AT; there were 22 PTE. Group II (N = 91) with only 8 weeks of AT had 2 PTE (P less than 0.01). ARH was the same in both groups. Actuarially , 71.7% of the patients in group I and 96.3% of the patients in group II were free of PTE at 6 years. Long-term AT proved ineffective in preventing PTE and carried a significant incidence of ARH. ARH surpassed PTE (3.5:1) in patients on short-term AT. Patients without TERF have a low incidence of PTE, and AT is not indicated. The "high-risk" group were patients in postoperative atrial fibrillation and left atrial enlargement. One week heparin therapy and 3 months oral AT is suggested for patients with TERF . PXBP for MVR in patients with TERF is significantly thrombogenic. Early operation is advocated to avoid development of TERF that will affect patient outlook after MVR with PXBP due to the significantly increased risks of PTE and (if placed on AT) ARH.

Prevention of thromboembolism using aspirin after mitral valve replacement with porcine bioprosthesis

The thromboembolic rate of 768 patients who were treated only with aspirin after mitral valve replacement or mitral plus aortic valve replacement with porcine bioprostheses was evaluated. We analyzed the thromboembolic rate for the whole series and for subgroups of patients categorized by atrial fibrillation, giant left atrium, left atrial thrombosis, and dosage of aspirin (1 gm daily or 0.5 gm every 48 hours). The total embolic rate was 1.4% (11/768). No patient in sinus rhythm had an embolic event. The embolic rate for patients in atrial fibrillation was 1.9% (11/583). There were no embolic events in 31 patients with a giant atrium. An embolic event occurred in 1 of 42 patients with atrial thrombosis (2.4%). Patients treated with 1 gm of aspirin daily had a 3% embolic rate (9/295) while the incidence was 0.4% (2/473) in those treated with 0.5 gm every 48 hours (p less than 0.01). Administration of aspirin after mitral valve replacement with a bioprosthesis is a very effective treatment for prevention of thromboembolism. In our experience, this treatment provides protection equal to or better than that offered by oral anticoagulants for patients in atrial fibrillation as well as for patients with a giant atrium or atrial thrombosis at operation. The dosage and timing of aspirin administration may markedly affect the result of this type of treatment. Oral anticoagulation with coumarin derivatives may not be appropriate after mitral valve replacement with a bioprosthesis, and platelet antiaggregates should be used for this purpose in the future.

Pregnancy in 20 patients with bioprosthetic valve replacement

We studied twenty women who became pregnant after porcine bioprosthetic valve replacement. Six patients had aortic valve, seven mitral, and seven aortic plus mitral valve replacement. All women were treated with aspirin (1 g daily or 500 mg every 48 hours) during pregnancy, delivery, and the postdelivery period. Thirteen patients experienced atrial fibrillation. There were 27 pregnancies with three ending in abortion. Twenty five normal babies were delivered. There was no maternal mortality or morbidity from thromboembolism or hemorrhage. Comparison of the pregnancy course of these women and the general population shows no difference with respect to fetal or maternal morbidity and mortality. Pregnant women with bioprosthetic valve replacement treated with aspirin had normal pregnancies without the risk of thromboembolism. Fetal and perinatal morbidity and mortality was also within normal limits.