Five-year follow-up after heart valve replacement with the CarboMedics bileaflet prosthesis

Low-Dose Warfarin in Patients with Carbomedics Heart Valve Prostheses

All patients who received a Carbomedics heart valve prosthesis were assessed retrospectively by interview regarding thromboembolic, hemorrhagic, or other valve-related events. In cases of such events, the patient's practitioner or cardiologist was interviewed. Hospital records were reviewed in cases of hospital admission. Included in the study were patients who had isolated replacement of the aortic or mitral valve in whom it was possible to collect all International Normalized Ratio values from discharge through follow-up. There were 148 patients with isolated aortic valve replacement and 56 with isolated mitral valve replacement. Bleeding events were 3 times more frequent than thromboembolic events. Based on our results we will apply an International Normalized Ratio between 2 and 2.5 for patients with a Carbomedics heart valve prosthesis in aortic position and ratios between 2.5 and 3 for those with a mitral valve prosthesis.

Early postoperative bridging anticoagulation after mechanical heart valve replacement: a systematic review and meta-analysis

OBJECTIVE

To perform a systematic review and meta-analysis of studies evaluating anticoagulation during the early postoperative period following mechanical heart valve implantation.

METHODS

Five literature databases were searched to assess the rates of bleeding and thromboembolic events among patients receiving oral anticoagulation (OAC), both with and without bridging anticoagulation therapy with unfractionated heparin (UFH) or subcutaneous low molecular weight heparin (LMWH). The studies' results were pooled via a mixed effects meta-analysis. Heterogeneity (I(2) ) and publication bias were both evaluated.

RESULTS

Twenty-three studies including 9534 patients were included. The bleeding rates were 1.8% (95% confidence interval CI 1.0-3.3) in the group receiving OAC, 2.2% (95% CI 0.9-5.3) in the OAC + UFH group, and 5.5% (95% CI 2.9-10.4) in the OAC + LMWH group (P = 0.042). The thromboembolic event rate was 2.1% (95% CI 1.5-2.9) in the group receiving OAC, as compared with 1.1% (95% CI 0.7-1.8) when the bridging therapy groups were combined as follows: OAC + UFH and OAC + LMWH (P = 0.035). Most of the analyses showed moderate heterogeneity and negative test results for publication bias.

CONCLUSIONS

Bridging therapy following cardiac valve surgery was associated with a lower thromboembolic event rate, although the difference was small, with considerable overlap of the CIs. Direct comparisons are missing. Bridging therapy with UFH appears to be safe; however, this observation has a risk of bias. Early bridging therapy with LMWH appears to be associated with consistently high bleeding rates across multiple analyses. On the basis of the quality of the included studies, more trials are necessary to establish the clinical relevance of bridging therapy and the safety of LMWH.

Mechanical aortic valve prostheses in the small aortic root: Top Hat versus standard CarboMedics aortic valve

BACKGROUND

The purpose of this study was to evaluate outcome in patients with a small aortic root receiving either a standard CarboMedics mechanical aortic valve or a Top Hat CarboMedics valve (CarboMedics, Austin, TX), specifically designed for the small aortic root.

METHODS

Between 1986 and 2006, 316 consecutive patients underwent 19- or 21-mm mechanical aortic valve replacement, receiving either a CarboMedics Top Hat bileaflet valve (n = 56; mean age, 66 +/- 14 years) or a standard CarboMedics aortic valve replacement (n = 260; mean age, 60 +/- 13 years) at our institution based on institutional indications for the choice of type of valve prostheses. Median follow-up time was 83.5 months. We studied survival, valve-related and non-valve-related events, and hemodynamic performance by serial echocardiographic follow-up studies.

RESULTS

In-hospital mortality was 8.9% in the Top Hat group and 10.0% in the standard group (p = 0.354). Five- and ten-year survival in patients in the Top Hat group was 83% and 67%, respectively. Five- and ten-year survival in the standard group was 73% and 59%, respectively (log-rank = 0.331). There were no differences in regard to valve-related and non-valve-related events. Cox regression analysis revealed age (hazard ratio, 1.045; 95% confidence interval, 1.026 to 1.066), previous cardiac surgery (hazard ratio, 1.812; 95% confidence interval, 1.101 to 2.982), additional procedures at the time of valve replacement (hazard ratio, 2.604; 95% confidence interval, 1.651 to 4.108), New York Heart Association class IV (hazard ratio, 3.645; 95% confidence interval, 1.214 to 10.945), and severely impaired left ventricular ejection fraction (hazard ratio, 2.253; 95% confidence interval, 1.289 to 3.941) to be independent predictors of survival.

CONCLUSIONS

Mechanical aortic valve replacement in the small aortic root is associated with substantial perioperative mortality, in particular in the subset of patients requiring additional cardiac surgical procedures. Nevertheless, long-term outcome is satisfying. Because the type of prosthesis does not predict outcome in the multivariate Cox model, we conclude that use of the smaller Top Hat prosthesis can be recommended for the challenging cohort of patients with a small aortic root.

Multicentered European Study on Safety and Effectiveness of the On-X Prosthetic Heart Valve: Intermediate Follow-Up

BACKGROUND

This study was performed to determine the safety and effectiveness of the On-X valve, a novel mechanical valve substitute.

METHODS

Eleven centers participated in a European, multicentered, longitudinal, nonrandomized study of the On-X valve performance. Isolated aortic or mitral valve replacement with an On-X valve was studied in 301 patients. Aortic valve replacement was performed in 184 patients (average follow-up, 5.0 years), whereas mitral valve replacement was performed in 117 patients (average follow-up, 4.4 years).

RESULTS

In patients with aortic valve replacement, mean transvalvular pressure gradients ranged from 8.3 to 4.7 mm Hg and effective orifice areas from 1.5 to 2.7 cm2, for 19-mm through 25-mm valves, respectively. After mitral valve replacement, mean gradient was 4.2 mm Hg and effective orifice area by pressure half-time was 2.6 cm2 regardless of valve size. Hemolysis was low, with postoperative serum lactate dehydrogenase at 225 +/- 41 IU (mean +/- standard deviation) or 253 +/- 65 IU, after aortic valve replacement or mitral valve replacement, respectively (upper normal value, 250 IU). At 1 year or greater postoperatively, 91.6% of patients after aortic valve replacement and 84.6% after mitral valve replacement were in New York Heart Association functional class I or II. Adverse event rates in percent per patient-year after aortic valve replacement or mitral valve replacement were thromboembolism, 0.88 or 1.76; thrombosis, 0.11 or 0.20; bleeding, 0.77 or 1.96, respectively. Late mortality was 1.97% or 2.55%, respectively.

CONCLUSIONS

At the intermediate follow-up, the On-X valve exhibited improved hemodynamics, low hemolysis with in-range lactate dehydrogenase, and low adverse event rates, particularly in the aortic position.

Early postoperative anticoagulation after mechanical valve replacement: a systematic review

The optimal approach to early postoperative anticoagulation after mechanical valve implantation remains controversial. This review article examines the pathogenesis of thrombus formation and the different strategies for early postoperative anticoagulation. The most commonly reported anticoagulation regimens had the after estimates of early postoperative thromboembolism and hemorrhage: oral anticoagulation alone (0.9%, 3.3%); oral anticoagulation with intravenous unfractionated heparin (1.1%, 7.2%); and oral anticoagulation with low molecular weight heparin (0.6%, 4.8%). Although intravenous heparin may be associated with a higher incidence of hemorrhage, a randomized trial is needed to provide the best evidence regarding early postoperative anticoagulation after mechanical valve implantation. Nearly four decades have passed since the first mechanical prosthetic valves were implanted. Frequent thromboembolic complications with the first mechanical valves led to recommendations of universal anticoagulation for these patients. Since then, several design changes and modifications have been made to improve the longevity, hemodynamics, and thrombogenicity of newer generation mechanical valves. With improved blood flow, less stasis, and less thrombogenic materials, lower rates of thromboembolism have been reported. Despite these advances however, thromboembolism and anticoagulant-related bleeding continue to account for 75% of all complications after mechanical valve replacement. Occurring most commonly within six months after implantation, these complications can adversely affect mortality and quality of life. Furthermore, the threat of their occurrence creates a psychological burden for each patient with a mechanical valve. The need for life-long anticoagulation in patients with mechanical valves is not in dispute, and the perioperative management of anticoagulation during non-cardiac surgery has been reviewed extensively. However, the approach to early postoperative anticoagulation after mechanical valve implantation is still a matter of debate. The optimal intensity and timing of anticoagulation to prevent early thromboembolism after valve replacement surgery without postoperative bleeding complications is unknown. Hence, many anticoagulation protocols have been proposed, but a lack of consensus remains. The objectives of this study were (1) to reexamine the pathogenesis of thrombus formation and the need for anticoagulation; (2) to critically review the literature on early postoperative anticoagulation strategies; and (3) provide an estimate of the incidence of bleeding and thromboembolism for each approach to early postoperative anticoagulation.

The CarboMedics prosthetic heart valve: experience with 180 implants

At Jichi Medical School Hospital, three types of mechanical prosthetic valves (CarboMedics, Omnicarbon, Bicarbon) were used without randomization from 1991 to 2000. A retrospective study of valve replacements done between June 1991 and November 2000 utilizing 180 CarboMedics valves in 145 patients who had not previously undergone prosthetic valve replacement or aortic root and/or arch replacement was conducted to evaluate midterm patient outcomes to assess the future continuous use of CarboMedics valves. Women made up 47.6% of the patients and the mean age was 57.5 years (range 12-80 years). Preoperative New York Heart Association functional class was III or IV in 92.4% (134/145) of patients. Mean follow-up of 4.5 years (range 0-10.0 years) was 95.9% complete, with a total of 628 patient-years (PY). Early (within 30 postoperative days) mortality was 5.5% (8 of 145): 3 from hemorrhage, 3 from nonvalve-related heart failure, 1 from infection, and 1 from arrhythmia. There were 16 late deaths (2.54%/PY): 1 from hemorrhage, 4 from unknown causes/sudden death, 4 from nonvalve-related heart failure, and 7 from other noncardiac causes. A total of 121 patients (83.0%) were alive at the last follow-up, done in November 2000. The linearized death rate was 3.82%/year (including 1.11%/year for valve-related deaths). Linearized death rates from various causes were: bleeding, 0.96%/year; thromboembolism, 1.11%/year; thrombosis, 0.39%/year; perivalvular leak, 0.96%/year; endocarditis, 0%/year; hemolysis, 0%/year; and reoperation, 0.63%/year. No structural valve failure was observed. Comparative early mortality rates of valve replacement without aortic root replacement or arch replacement, excluding repeat valve replacement operations, in our institute, were 3.5% (12/307) for all valve types used contemporaneously, 2.6% (2/76) for Omnicarbon valves, and 2.3% (2/86) for Bicarbon valves. Although the CarboMedics valve had a rather high mortality rate of 5.5% (8/145) compared with the total early mortality rate of 3.5%, the low incidence of valve-related complications might support the continued use of the CarboMedics valve for valve replacement.

Long-Term Result of 1144 CarboMedics Mechanical Valve Implantations

BACKGROUND

It has been reported that the CarboMedics mechanical valve has acceptable valve-related complication rates. The aim of this study was to evaluate the long-term performance of the CarboMedics valve.

METHODS

Between August 1988 and September 1999, we implanted 1144 CarboMedics valves in 850 patients (aortic, 179; mitral, 385; double-valve, 234; tricuspid, 52). Mean patient age was 44.5 +/- 12.5 years. Follow-up was completed in 95.3% and the median follow-up period was 7.9 years (6753 patient-years). Patients were divided into four groups according to implanted valve location and number (aortic, mitral, double, and tricuspid valve groups).

RESULTS

The overall hospital mortality rate was 3.4%, and the mortality rates in these groups were 1.7% in the aortic, 2.6% in the mitral, 4.7% in the double, and 9.6% in the tricuspid valve. The tricuspid valve group revealed a significantly higher mortality rate than the aortic and mitral valve groups (p < 0.05). Overall 10-year survival was 87.1% +/- 2.6%, 88.9% +/- 1.7%, 82.4% +/- 2.9%, and 77.5% +/- 7.0% in the aortic, mitral, double, and tricuspid valve groups, respectively. Age and tricuspid valve replacement were identified as significant risk factors of long-term survival by multivariate analysis (p < 0.05), and 99.4% +/- 0.6%, 98.2% +/- 0.8%, 99.2% +/- 0.8%, and 87.6% +/- 0.5% in the aortic, mitral, double, and tricuspid valve groups were free of valve thrombosis at 10 years. The tricuspid valve group demonstrated a significantly higher rate of valve thrombosis (p < 0.05).

CONCLUSIONS

This long-term study of patients that received CarboMedics valve implantation demonstrates that the CarboMedics prosthetic valve has an acceptable incidence of valve-related complications. However, it should be noted that tricuspid valve replacement indicated a higher level of overall mortality and valve thrombosis.

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+).

"Our complication rates are lower than theirs": statistical critique of heart valve comparisons

OBJECTIVES

From the widely differing complication rates published for every heart valve, is it possible to determine a true rate for each valve and to compare the rates of two different valves? We investigated this question for the two most popular bileaflet valves.

METHODS

Aortic valve data were abstracted from 14 St Jude Medical (St Jude Medical Inc, Minneapolis, Minn; 33,125 patient-y) and 11 Carbomedics (Sulzer Carbomedics Inc, Austin, Tex; 19,141 patient-y) series, and mitral valve data were abstracted from 11 St Jude Medical (21,553 patient-y) and 8 Carbomedics (8368 patient-y) series. Regression analysis was used to accommodate heterogeneity among rates with the same valve model, to estimate hazard ratios and 95% confidence intervals for the valve model effect, and to incorporate other series-level risk factors.

RESULTS

Most of the complication rates with both valve models exhibited significant heterogeneity. For thromboembolism and bleeding, the relative risks for valve model were not significantly different from unity. Valve thrombosis rates exhibited less heterogeneity: the Carbomedics valve had a lower rate in the aortic position (hazard ratio 0.2, 95% confidence interval 0.1-0.6) and a higher rate in the mitral position (hazard ratio 1.9, 95% confidence interval 1.0-3.8).

CONCLUSIONS

Unlike simple weighted averages of valve complication rates, regression methods can incorporate heterogeneity related to center effects and allow for inclusion of other risk factors. Thromboembolism and bleeding rates were not significantly different with St Jude Medical and Carbomedics valves. Valve thrombosis appeared to differ between the two valves, but the absolute differences in rates were small. Because of the variability among rates with the same valve, statistical comparisons must be interpreted cautiously.

Up to 8-year follow-up of valve replacement with carbomedics valve

BACKGROUND

The aim of this study was to report midterm valve replacement (VR) results with the Carbo-Medics valve (Sulzer Carbomedics, Austin, TX).

METHODS

From 1991 to 1999, 468 patients aged 13 to 76 years (mean 56 years) underwent VR with CarboMedics valve: 239 aortic (A), 167 mitral (M), and 62 A+M or double valve replacement (DVR). Mean follow-up time was 4.4 years; follow-up was 99.1% complete for 2,016 patient-years (PY). The anticoagulation level was targeted to an international normalized ratio of 1.47 to 2.8.

RESULTS

The hospital mortality rate was 1.2%. Actuarial analysis for the entire group at 7 years for survival was 87%+/-2.3%. Freedom from valve-related death was 94%+/-1.9%. Freedom from thromboembolic and bleeding events, respectively, were as follows: for AVR, 82%+/-4.9% (2.4%/PY) and 88%+/-2.9% (1.6%/PY); for MVR, 95%+/-2.1% (0.8%/PY) and 91%+/-3.1% (1.3%/PY); and for DVR, 96%+/-3.2% (0.7%/PY) and 85%+/-9.7% (1.0%/PY). Actuarial freedom from reoperation was 98%+/-1.4%.

CONCLUSIONS

The CarboMedics valve can be implanted with satisfactory early mortality and a low incidence of valve-related events even under low-intensity anticoagulation, as shown in a Japanese population.

Microembolic signal counts increase during hyperbaric exposure in patients with prosthetic heart valves

BACKGROUND

Patients with prosthetic heart valves have an increased risk of thromboembolic events, and transcranial Doppler sonography reveals microembolic signals. Whereas microembolic signals were initially assumed to be of particulate matter, recent studies suggest that they are partially gaseous in origin. If this is true, alteration of environmental pressure should change microembolic signal counts. We undertook this study to evaluate the influence of hyperbaric exposure on microembolic signal counts in persons with prosthetic heart valves.

METHODS AND RESULTS

Microembolic signal counts were monitored by transcranial Doppler sonography of both middle cerebral arteries under normobaria (normobaria 1), 2 subsequent periods of hyperbaria (2.5 and 1.75 bar), and a second period of normobaria (normobaria 2) in 15 patients with prosthetic heart valves. Each monitoring period lasted 30 minutes. Compression and decompression rates were 0.1 bar/min. Microembolic signal counts increased from 20 (12-78) at normobaria 1 to 79 (30-165) at 2.5 bar (P <.01 vs normobaria 1 and 2), decreased to 44 (18-128) at 1.75 bar (P <.01 vs normobaria 1 and 2.5 bar; P <.001 vs normobaria 2), and returned to 20 (8-96) at normobaria 2 (values are medians and 95% confidence intervals).

CONCLUSIONS

Our results strongly suggest that gaseous bubbles are underlying material for part of the microembolic signals detected in patients with prosthetic heart valves.

Fourteen year experience with the omnicarbon prosthetic heart valve

The Omnicarbon prosthetic valve was implanted in 168 patients (mean age, 53 years); 84 had aortic valve replacement (AVR), 57 had mitral valve replacement (MVR), and 27 had both aortic and mitral valve replacement (DVR). The mean follow-up period was 6.8 years, with a maximum of 13.7 years. Three patients (1.8%) were lost to follow-up. There were 4 (2.4%) early deaths and 26 late deaths. Survival at 10 years was 76% in the AVR and MVR groups, and 85% in the DVR group. Freedom from thromboembolism at 10 years was 94% in the AVR group, 80% in the MVR group, and 92% in the DVR group. Freedom from hemorrhagic complications at 10 years was 86% in the AVR group and 92% in the MVR group. At 10 years, 97% in the AVR group and 96% in the MVR group were free from endocarditis. One patient in the DVR group suffered a paravalvular leak. At 10 years, 97% in the AVR group and 95% in the MVR group had not needed reoperation. Elevation of the postoperative serum lactate dehydrogenase levels were acceptable in the three groups. In conclusion, the Omnicarbon prosthetic valve has shown excellent long-term clinical results.

Intermediate-term results with 1,019 carbomedics aortic valves

BACKGROUND

A retrospective study was conducted to evaluate the intermediate-term outcome in patients with the Carbomedics aortic valve prosthesis.

METHODS

The study included 1,019 primary valve replacements between 1989 and 1997. Seventy-two percent of patients were men; mean (standard deviation) age was 61 (10) years. The preoperative New York Heart Association functional class was III or IV in 70% of patients. Follow-up at 9 years was 99.6% complete, comprising 2,730 patient-years (mean, 2.7 years).

RESULTS

Patient survival, including operative deaths, was 80% at 7 years. The linearized death rate was 2.9%/year. Statistically significant risk factors for mortality were diabetes, pure valve insufficiency, advanced age at operation, and advanced preoperative functional class. Linearized rates were thrombosis, 0.1%/year; thromboembolism, 1.0%/year; hemorrhage, 1.7%/year; endocarditis, 0.1%/year; paravalvular leak, 0.1%/year; reoperation, 0.1%/year; and all events, 3.0%/year. The 7-year estimates of freedom from complications were thrombosis, 99%; thromboembolism, 93%; hemorrhage, 89%; endocarditis, 99%; paravalvular leak, 99.7%; reoperation, 99%; and all events, 82%. No structural valve failure was observed.

CONCLUSIONS

The low incidence of valve-related complications favors the continued use of the Carbomedics valve in the aortic position.

A single-center experience with 1,378 CarboMedics mechanical valve implants

BACKGROUND

The CarboMedics bileaflet prosthetic heart valve was introduced in 1986. We first implanted it in March 1991. The purpose of this study was to analyze our clinical experience with this valve.

METHODS

Between March 1991 and December 1997, 1,378 valves were implanted in 1,247 patients, 705 men (56.5%) and 542 (43.5%) women with a mean age of 62 +/- 11.9 years (+/- the standard deviation). Follow-up is 99% complete and totals 3,978 patient-years.

RESULTS

The early mortality rate was 4.4% (55/1,247). The survival rates at 1 year and 5 years were 91.8% +/- 0.8% (+/- the standard error of mean) (n = 1,062) and 79.2% +/- 1.4% (n = 281), respectively. Freedom from valve-related complications (linearized rate, 4.9% per patient-year) at 1 year and 5 years was 90.6% +/- 0.8% (+/- the standard error of the mean) (n = 996) and 80.6% +/- 1.4% (n = 243), respectively. Linearized rates for various complications were as follows: bleeding events, 1.73% per patient-year; embolic events, 1.76% per patient-year; operated valvular endocarditis, 0.18% per patient-year; valve thrombosis, 0.10% per patient year; and nonstructural dysfunction, 1.21% per patient-year. Freedom from reoperation at 1 year and 5 years was 98.6% +/- 0.3% (+/- the standard error of the mean) (n = 1,070) and 97.7% +/- 0.5% (n = 285), respectively.

CONCLUSIONS

Midterm results demonstrate that the CarboMedics prosthetic heart valve exhibits a low incidence of valve-related complications.

Outcome analysis of 245 CarboMedics and St. Jude valves implanted at the same institution

BACKGROUND

Thromboembolism and valve-related death are major complications associated with prosthetic valve implants, but it is difficult to evaluate the relative incidence of these complications based on studies in which the implantation of only one valve is reported from any given institution. We therefore report the outcome of patients implanted at our institution during the same time period with either the recently released CarboMedics (CM) or the St. Jude Medical (SJ) valve prostheses.

METHODS

Between October 1994 and January 1996, 245 consecutive patients received either SJ (116 patients) or CM (129 patients) valves at our institution. Follow up of these patients was 99.6% complete, for a total of 318.5 cumulative patient-years (median follow-up, 1.4 years).

RESULTS

The 30-day mortality rates for SJ and CM implants were 3.4% and 3.1%, respectively. Actuarial survival and freedom from valve related mortality rates at 1.5 years for SJ and CM valves were 94%+/-2% versus 86%+/-3% (p = 0.03) and 100% versus 94%+/-2% (p = 0.005), respectively. There was no structural valve failure for either implant, but there were five thrombosed valves in the CM group and none in the SJ group (p = 0.04). All thrombosed valves were mitral (four mitral valve replacement, one aortic and mitral valve replacement). Two of the thrombosed valves were successfully explanted, whereas the three remaining patients died. Freedom from a thromboembolic event in the mitral position at 1.5 years, including thrombosed valves was 97%+/-3% and 83%+/-5% for SJ and CM valves, respectively (p = 0.04).

CONCLUSIONS

The results of this study suggest that further evaluation of thromboembolic outcomes after CM compared with SJ valve implantation is warranted.

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.