Pregnancy after heart valve replacement

Thirty-two women, aged 21 to 44 years, who had undergone single (25) or multiple (7) heart valve replacement conceived 46 times and gave rise to 33 live-born infants. There were 12 abortions and one stillborn; a premature baby died 24 hr post-partum. Twenty-eight patients had mechanical prostheses and 4 had porcine xenografts, 29 patients being anticoagulated with acenocoumarol during the pregnancy. Cardiac status remained clinically satisfactory under medical treatment in all but one patient who developed heart failure. Fetal complications included cerebral hemorrhage in 1 premature infant, low birth weight in 3 newborns and 1 case of nasal hypoplasia. The incidence of abortion has decreased significantly during the latter part of our experience. It was significantly greater in patients with mitral prostheses. This review suggests that inadequate cardiac function, excessive anticoagulation and a history of primary infertility may increase the risk of abortion. Better control of anticoagulant therapy (accepting an elevation of the therapeutic limit) and improved prevention of pregnancy in high-risk patients are considered responsible for the improved results seen in recent years.     

Thromboembolism in patients with prosthetic heart valves. An adequately controlled intense anticoagulant therapy and its influence on the occurrence of thromboembolism in relation to valve type

This study was designed to evaluate the efficacy of carefully controlled treatment with oral anticoagulants in patients with different mechanical heart valve prostheses. One hundred eighty-one patients with various types of prosthetic valves (mitral 89, aortic 87, combined 5) received oral anticoagulation aiming at Thrombotest (TT) values between 5% and 12%. Median follow-up was 46 months; 80.8% of all TT determinations were below 12%. The thromboembolic rate was 0.25%/year in patients with aortic valve replacement (AVR) and 4.87%/year in patients with mitral valve replacement (MVR). There was a strikingly lower incidence of thromboembolism with newer types of valves (Bj?rk-Shiley convex-concave) in the mitral position under exactly the same intensity and stability of anticoagulant treatment. Clinically overt valve occlusion could be almost completely prevented (0.12%/year) in prostheses at both sites. Severe hemorrhage occurred at a rate of 1.71%/year and fatal bleeding at a rate of 0.37%/year. Our results indicate that carefully controlled anticoagulation is effective in the reduction of thromboembolic complications at a reasonable risk of bleeding.     

Mechanical heart valves: an insight into thrombotic complications.

The purpose of this retrospective analysis was to improve the follow-up care of patients with mechanical heart valves. Clinical data of 88 patients who had undergone valve replacement surgery in various cardiothoracic centres in the country and followed up in Tata Main Hospital, Jamshedpur, India were analysed. The incidences of thrombotic complications with Starr-Edwards, St. Jude and Medtronic-Hall valves placed in mitral, aortic or both the sites were studied. In the single valve replacement group, St. Jude valve in mitral position had the highest thromboembolic risk of 12.5 per 100 patient-years. In the double valve replacement group, all the three prostheses had high thrombotic risk: St. Jude 22.2, Medtronic-Hall 12.5 and Starr-Edwards 8.6 per 100 patient-years. The high thrombotic incidence with St. Jude and Medtronic Hall in this series was correlated with early post-operative period. Subtherapeutic antiocoagulation was the key factor for thrombotic complications. Some of the commonly used drugs and diet rich in vitamin K interfere with anticoagulation, causing thrombosis in those who were more prone. Education of patients as well as the primary care physician is required to reduce life threatening thromboembolic complications, as more centres are replacing damaged valves with prostheses in patients who return to their hometown for follow-up care.     

Is aortic valve replacement with bileaflet prostheses still contraindicated in the elderly?

BACKGROUND: Prolonged survival in the Western world has increased the number of elderly patients referred for open-heart surgery during the last decade. Aortic valve disease is the most common heart valve disease in aged patients. Which aortic valve substitute is best employed in the elderly is still a debated matter. The main concern is about the thromboembolic and hemorrhagic risks related to mechanical valves and anticoagulation. OBJECTIVE: The study aimed at reviewing clinical results after isolated aortic valve replacement with bileaflet prostheses in patients over 70 years and at retrospectively comparing them with those of a group of otherwise comparable patients under 50 years of age who underwent isolated aortic valve replacement with a mechanical device. METHODS: The study population included 118 consecutive elderly patients (group A) operated on between January 1988 and January 1999 and 122 young patients (group B) who underwent aortic valve replacement during the same time period. Patients with associated coronary artery disease, mitral stenosis or regurgitation, type A aortic dissection, and infective endocarditis were excluded from the study. Preoperative clinical data, early and late postoperative mortality, all valve-related complications, and all data concerning the anticoagulation status - including the mean international normalized ratio (INR) and the mean time interval between each INR assay - were compared between the two groups. RESULTS: The hospital mortality was significantly lower in group B (2.45%) than in group A (9.3%; p = 0.022). The mean follow-up period was 50.98 +/- 2.23 months. The 12-year actuarial survival was significantly lower (69.6 +/- 0.08%) in group A than in group B (94.4 +/- 0.02%; p < 0.001). No significant difference was found in terms of valve-related and anticoagulation-related complication rates and actuarial freedom as well as mean interval between consecutive INR checks (p = 0.219) and mean INR value (p = 0.914). CONCLUSIONS: Bileaflet prostheses in elderly patients can achieve excellent early and late clinical results, with a low incidence of anticoagulation-related complications and an extremely low risk of a reoperation. Older age can no longer be considered a contraindication to bileaflet prosthesis implantation in the aortic position.     

老年人单纯二尖瓣病变不同术式疗效的临床观察

目的观察机械瓣置换、生物瓣置换及瓣膜成形手术对≥60岁单纯二尖瓣病变患者远期疗效的影响。方法 2006年1月至2008年12月116例≥60岁的单纯二尖瓣手术出院患者,风湿性二尖瓣病变76例,二尖瓣退行性病变40例。人工机械瓣膜置换62例,生物瓣膜置换34例,二尖瓣成形术20例。门诊或电话随访,记录死亡、再次手术、感染性心内膜炎、瓣周漏、心功能分级、抗凝情况、出血事件、血栓栓塞等事件。结果 116例患者随访24～60月,平均(48.4±10.7)月。20例瓣膜成形的患者,随访期间无死亡病例,二尖瓣功能良好,未出现中度以上返流、再次住院、再次手术及其他不良事件。34例生物瓣膜置换的患者,均口服阿司匹林抗凝,随访期间未出现瓣膜衰败现象,瓣膜功能正常,心功能均明显改善。62例机械瓣置换的患者,均服用华法林抗凝,机械瓣膜功能良好,心功能明显改善。可见感染性心内膜炎、瓣周漏、出血事件及血栓栓塞等事件发生。结论手术治疗≥60岁二尖瓣病变患者的疗效显著,能明显改善患者心功能,延长生存时间。但不同术式的远期效果有一定差异。瓣膜成形术后避免抗凝药物的应用,可避免抗凝并发症。生物瓣膜置换可达到瓣膜成形术的效果,但因其存在生物衰败,可能需要再次手术,在年龄相对低的患者中根据情况选择。机械瓣膜置换需要终生抗凝治疗,影响远期效果的主要因素为出血和血栓并发症,严格规律地监测凝血指标,可最大程度减少抗凝并发症的发生,提高治疗效果。     

Ten year clinical evaluation of Starr-Edwards 2400 and 1260 aortic valve prostheses.

The long term performance characteristics of the 2400 and 1260 series of Starr-Edwards aortic prostheses were investigated by a follow up study of clinical outcome of 327 patients discharged from hospital with isolated aortic valve replacement. Follow up lasted for up to 10 years and was based on 1616 patient-years. The 2400 series cloth covered tracked valve was implanted in 182 patients from 1974 to 1980 and the 1260 series bare strut silastic ball valve was inserted in 145 patients from 1979 to 1983. Total 10 year mortality and valve related morbidity were low and no cases of mechanical valve failure were recorded. There were no significant actuarial differences in mortality or valve related morbidity between the 2400 and 1260 valves. Starr-Edwards models 2400 and 1260 aortic valve prostheses showed excellent durability without any mechanical failures over a 10 year period. The long term outcome of isolated aortic valve replacement with these models is associated with a low frequency of valve related complications.     

Prospective evaluation of frequency and nature of transcranial high-intensity Doppler signals in prosthetic valve recipients.

BACKGROUND AND AIM OF THE STUDY: In asymptomatic prosthetic valve recipients, high-intensity transient signals (HITS) observed with transcranial Doppler (TCD) are a phenomenon of obscure clinical relevance which nature has not yet been elucidated convincingly. METHODS: Eighty-three patients without carotid disease, history of cerebrovascular accidents, and with negative preoperative TCD undergoing either valve replacement (mitral, n = 11; aortic, n = 56; mitral + aortic, n = 6; 40 mechanical prostheses, 29 biological prostheses, 10 homografts) or mitral repair (n = 10) were evaluated prospectively by means of TCD at discharge, three months and one year after surgery, to analyze the presence, incidence and characteristics of HITS. Furthermore, in 12 patients positive for HITS, TCD was repeated during a 30-min period of 100% O2 inhalation. RESULTS: Twenty-five patients (30%) were positive for HITS at all postoperative controls, although no neurological symptoms were observed. Mechanical prostheses showed a significantly higher incidence of HITS (85%) than biological prostheses (10%, p <0.001), repaired mitral valves (0%, p <0.001) and homografts (0%, p <0.001). At multivariate analysis the presence of a mechanical prosthesis was the only significant predictor of detection of HITS after valve replacement. During O2 inhalation, a significant decrease in the number of HITS per hour (55 +/- 79 versus 22 +/- 31, p = 0.002) occurred, which returned to initial values when room-air breathing was resumed. CONCLUSIONS: Prosthetic valve replacement, particularly when mechanical devices are used, is associated with the generation of HITS which persist throughout the follow up period, but remain clinically silent. The decrease of HITS during O2 inhalation strongly supports the hypothesis of the gaseous nature of such signals and confirms the validity of this method in helping to differentiate gaseous microemboli from solid microemboli in prosthetic valve recipients.     

Prosthesis-related complications: first-year annual rates

The rates of valve-related complications determine the clinical performance of biological and mechanical heart valve prostheses by valve position. The crude rates of valve-related complications within the first year after implantation have not been previously reported. The Food and Drug Administration (FDA) of the United States guidance document for the performance of new heart valve prostheses uses objective performance criteria (OPC) as target values for valve-related complications. The FDA requirement for each valve-related complication is that the rate cannot be greater than twice the OPC. This report provides the first-year rates of valve-related complications from a university database of over 7,000 implants, followed longitudinally between 1982 and 1999, of currently marketed biological and mechanical heart valve prostheses. The aim of this report was to provide an additional method for consideration by regulatory authorities in determination of the standards of performance for pre-market approval of new prosthetic valves for heart valve replacement surgery.     

Porcine valves

To date, the glutaraldehyde porcine aortic valve xenograft has proved a good choice for valve replacement in both the aortic and mitral positions. Late thromboembolisms in the absence of long-term anticoagulation is virtually nonexistent in aortic valve replacement and very low in mitral valve replacement patients without a predisposing history. The hemodynamic performance of the porcine xenograft is adequate and comparable to that of mechanical prostheses. The potential for improved hydrodynamic function, particularly of very small sized valves, is great and already being realized. In spite of over 8 yr of xenograft experience, long-term durability remains the primary concern. Histologic study suggests that these valves undergo progressive postimplantation morphological alteration. However, to date, the incidence of tissue failure is very low. Although detailed reports of long-term valve series are surprisingly few, at present, there is no valve replacement device with a 10-yr experience proven structural integrity and a negligible incidence of valve-related morbidity. It will be 3-4 yr before a significant number of porcine xenograft patients either reach this point or experience valve failure. While this review of the valve literature does not permit a statistical comparison of valve types, we feel that it does allow us to attempt a general projection. On the basis of combined survival and valve-related complication rates, at 4 yr, the porcine xenograft appears to be a better choice than the mechanical prosthesis. Excessive tissue failure during the next 3-4 yr might reverse this opinion. However, even if an increase in valve failure does occur, the advantage of noncatastrophic disfunction and decreased valve-related complications may balance the risk of reoperative morbidity and mortality and continue to favor the porcine exnograft. Thus we could speculate that: (1) The tissue valve would be the valve of choice if (A) durability of 10 yr or more is proven, and valve complications with the xenograft remain as presently reported; (B) the incidence of valve complications with the mechanical prostheses at 10-yr follow-up continues to increase. (2) Mechanical prostheses would be the valves of choice if (A) xenograft valve failure is greater than 20% at 10 yr of follow-up; (B) the incidence of valve complications with the mechanical prostheses remains unchanged. (3) The choice of xenograft versus mechanical prosthesis will remain an open issue if valve failure and related complications with both types of device remain below 20% at 10-yr follow-up...     

Aortic and mitral prosthetic valve replacement in age groups 61-65 & 66-70 years

Prosthesis choice for aortic and mitral valve replacements in patients aged 61-70 years is difficult. We evaluated prostheses in age groups 61-65 and 66-70 years. Freedom from major thromboembolism and hemorrhage was greater for bioprostheses than mechanical prostheses in both age groups after aortic valve replacement, but only in the younger age group after mitral valve replacement. Freedom from valve-related re-operation was greater after mitral valve replacement with mechanical prostheses in both age groups, but no difference after aortic valve replacement. Valve type was predictive of major thromboembolism and hemorrhage, except in older patients undergoing mitral valve replacement. Bioprostheses are favored for aortic valve replacement in both age groups, but the risk of re-operation with a bioprosthesis in the mitral position in patients aged 61-65 years favors a mechanical prosthesis. Prosthesis choice is less definite in those aged 66-70 years.     

Ten year clinical evaluation of Starr-Edwards 2400 and 1260 aortic valve prostheses

The long term performance characteristics of the 2400 and 1260 series of Starr-Edwards aortic prostheses were investigated by a follow up study of clinical outcome of 327 patients discharged from hospital with isolated aortic valve replacement. Follow up lasted for up to 10 years and was based on 1616 patient-years. The 2400 series cloth covered tracked valve was implanted in 182 patients from 1974 to 1980 and the 1260 series bare strut silastic ball valve was inserted in 145 patients from 1979 to 1983. Total 10 year mortality and valve related morbidity were low and no cases of mechanical valve failure were recorded. There were no significant actuarial differences in mortality or valve related morbidity between the 2400 and 1260 valves. Starr-Edwards models 2400 and 1260 aortic valve prostheses showed excellent durability without any mechanical failures over a 10 year period. The long term outcome of isolated aortic valve replacement with these models is associated with a low frequency of valve related complications.     

Long-term follow-up of aortic or mitral valve replacement. Comparison of results following implantation of a mechanical or biological artificial valve

The prognosis of valvular heart disease is favorably influenced by surgical treatment in spite of the possible incurrence of early or late postoperative complications. The hemodynamic properties of currently implanted bioprostheses and mechanical prostheses are essentially similar. It can be assumed that the fate of the patient, after having survived the early-postoperative phase, is predominantly dependent on the underlying disease and on complications of the prosthetic valve, itself, or the inherent necessity for chronic anticoagulation. To characterize the longterm course more closely, in this study in patients with prosthetic aortic or mitral valves, analysis of the survival rate as well as incidence of valvular dysfunction, late endocarditis, thromboembolism and bleeding associated with anticoagulant therapy was performed separately for patients with Bj?rk-Shiley prostheses and for those with bioprostheses. The study encompasses 407 patients after isolated aortic valve replacement, 226 with Bj?rk-Shiley prosthesis and 181 with bioprosthesis, as well as 269 patients after isolated mitral valve replacement, 142 with Bj?rk-Shiley prosthesis and 127 with bioprosthesis (Table 2). All patients had valve replacement between 1975 and 1983 which was performed in the Department of Cardiovascular Surgery at the German Heart Center in Munich under comparable conditions, since 1977 with employment of cardioplegia. The preoperative characteristics of the groups compared did not differ significantly from each other (Table 1). Continuous follow-up was obtained in 95% of the patients. The mean observation period of all four compared patient groups ranged between 52.1 and 61.3 months. The term "major complication" was used to designate late-postoperative death, hemodynamic derangement due to prosthetic dysfunction, late endocarditis as well as major thromboembolism or bleeding. Prosthetic dysfunction in the case of Bj?rk-Shiley valves was designated as mechanical or due to thrombosis, in the case of bioprostheses as valve degeneration or thrombosis. Late endocarditis was diagnosed only on documentation of - with a minimum interval of 30 days between valve implantation and onset of symptoms - changes in auscultatory findings and a morphological substrate on the implanted valve. Thromboembolism was assumed, after ruling out bleeding, only if a definitive or highly-probable transient or permanent neurologic deficit or a well-established suspicion of acute ischemia in an extremity or visceral organ was present. A bleeding complication was considered as such only if treatment by a physician was required.(ABSTRACT TRUNCATED AT 400 WORDS)     

Aortic allograft (homograft) for the treatment of valvular disorders in adults with focus on treatment of infective aortic valve endocarditis

Still after 40 years of heart valve prostheses intensive development ideal valve substitute still does not exist. Aortic allograft represents one alternative which could be used for aortic and/or pulmonary valve replacement. This type of biological heart valve prosthesis is being currently discussed from the point of view of Tissue Banking, as well as from clinical aspects--e.g. surgical implantation technique and long term results. Live issue remains particularly the aortic allograft implantation into the aortic position. The authors discuss the aortic allograft role in the aortic valve infectious endocarditis treatment, which was widespread worldwide and accepted. Aortic allograft implantation is considered as a method of choice in that particular indication, especially in prosthetic aortic valve endocarditis and in left ventricle outlet tract destruction cases. The method is considered to be more technically demanding than routine heart valve surgery (heart valve replacement by means of mechanical or commercial biological prostheses), but literary and authors own experience in that particular group of patients looks encouraging. Aortic allografts permanent supply in our country is secured.     

In vitro investigation of prosthetic heart valves in magnetic resonance imaging: evaluation of potential hazards

BACKGROUND AND AIM OF THE STUDY: Magnetic resonance (MR) imaging is used in an increasing number of patients, and not only after cardiac valve replacement. However, ferromagnetic biomedical implants are often considered a contraindication for MR imaging because of the potential hazards with respect to their movement, dislodgement, or heating effects during the procedure. The purpose of this study was to assess ferromagnetism, attraction forces, heating effects, and artifacts associated with prosthetic heart valve implants. METHODS: Seventeen common heart valve prostheses (12 mechanical, five biological) were examined in vitro using a high-field-strength 1.5 Tesla (T) MR system. Attractive forces, temperature changes and the amount of artifacts were assessed by applying turbo-spin and gradient-echo sequences. RESULTS: The maximal calculated corresponding ferromagnetic force was (0.22 x 10(-3) N) in the static magnetic field. The temperature changes ranged from 0 to 0.5 degrees C maximum. Artifacts produced by the presence of the heart valve prostheses were less evident using a spin-echo sequence than a gradient-echo sequence. CONCLUSION: MR imaging exerted no significant force on the examined heart valve prostheses, and did not result in significant biological relevant temperature increase. None of the associated artifacts is considered to pose a substantial risk on MR imaging. MR procedures performed with a 1.5 T MR system can be applied safely in patients with heart valve prostheses evaluated in this study.     

Valve replacement in children: early and late results

In order to analyze the problems associated with prosthetic valve replacement (PVR) in the pediatric population, we have reviewed 29 children, 3.5 to 15 years of age, who were operated upon from 1970 to 1986. The indications were congenital valve malformations in 16 patients, rheumatic valve disease in 7, degenerative disease in 2 and bacterial endocarditis in 4. Ten children underwent aortic valve replacement (AVR), 14 mitral valve replacement (MVR), 1 tricuspid valve replacement and 4 double valve replacement (mitral-aortic in 3 and mitral-tricuspid in 1). Twenty-one mechanical (11 aortic and 10 mitral) and 12 biological prostheses (8 mitral, 2 aortic, and 2 tricuspid) were implanted. There was 1 hospital death (3.4%). Follow-up data were available for all survivors from 3 to 184 months. There were 8 late deaths (5.9% patient-year), 4 among children with mechanical and 4 among those with biological prostheses. Overall actuarial survival at 14 years is 62.5 +/- 10.2% with no significant difference in survival between AVR (77.8 +/- 14%) and MVR (44.4 +/- 16%) (p = 0.31) at 10 years and between recipients of mechanical (65.7 +/- 13%) or biological prostheses (60.0 +/- 15%) (p = 0.62) at 6 years. No documented embolic or anticoagulant-related complications occurred in the entire series.(ABSTRACT TRUNCATED AT 250 WORDS)     

Surgical treatment of prosthetic valve thrombosis: ten years' experience

BACKGROUND AND AIM OF THE STUDY: Prosthetic valve thrombosis (PVT) is a rare, but serious, complication of heart valve replacement with a mechanical substitute. Herein is presented the authors' surgical experience of 18 patients with PVT. METHODS: A total of 1,584 heart valve operations was performed in 1,365 patients at the authors' institution between June 1995 and September 2005. Surgical reports of prosthetic valve reoperations over the same period were screened. Preoperative, operative and postoperative data were collected from the patient cohorts. RESULTS: Since July 1997, 18 patients (12 females, six males; mean age 35.9 +/- 11.3 years; range: 22-60 years) presented with PVT. The subtherapeutic anticoagulation level was the major etiologic factor involved in the pathogenesis of PVT. Thrombosis occurred in the mitral position in 14 patients (78%), and in the aortic position in four (22%). All mechanical valves implanted were bileaflet (1,097 St. Jude Medical, 324 CarboMedics, and 163 Sorin). The mean duration from valve replacement to PVT was 48.3 +/- 15.4 months. The majority of patients presented with poor functional status (56% in NYHA class IV) and poor anticoagulation (INR < or = 2 in 72% of cases). Valve re-replacement was performed for all patients. The 30-day mortality was 16.7%. CONCLUSION: PVT is a potentially fatal complication of heart valve replacement. These acceptable results suggest that early surgical intervention might be a safe and effective treatment of choice in patients with PVT. Patients with mechanical valve prostheses should be informed adequately about the need for, and the importance of, an effective anticoagulation regimen.     

Exercise evaluation of prosthetic heart valves by Doppler echocardiography: comparison with catheterization studies

Although valve replacement remains the cornerstone of treatment for critical heart valve dysfunction, problems including thromboembolism, infection, and primary failure of the prosthesis remain. Resting studies of valve hemodynamics are sometimes insufficient to reveal valve dysfunction. Early studies using cardiac catheterization focused on changes in prosthetic function seen with various types of exercise or drug-induced stress. These studies suffered from an inability to adequately stress catheterized patients and were cumbersome to the patient and the investigator. With the introduction of Doppler echocardiography, however, studies could be performed after significant exercise with low risk and increased ease. Using echocardiography, reports of exercise-induced changes in aortic and mitral valve hemodynamics have appeared. Over 600 patients have been studied using Doppler echocardiography. In the aortic position, all prostheses studied have a mild peak instantaneous gradient (18-26 mmHg) at rest, which increases with exercise (35-63 mmHg). No significant differences between the four models of mechanical prostheses studied are found. The gradients achieved with exercise do not appear to be related to the heart rate achieved or duration of exercise. Smaller prostheses are associated with larger gradients; however, the correlation was not strong. All mitral valve prostheses studied are also mildly stenotic at rest (range of mean gradients 2.3-7.1 mmHg) and become moderately stenotic with exercise (range 5.1-16.5). Although the lowest gradients are seen with St. Jude Medical and Medtronic Hall prostheses, their gradients are not significantly less than with other valves.(ABSTRACT TRUNCATED AT 250 WORDS)     

Replacement of an immobile prosthetic mitral valve: a case report.

A mechanical prosthetic heart valve can become acutely obstructed despite anticoagulation therapy. This can be a life-threatening complication. We report the case of a 38-year-old woman who survived obstruction of her Sorin prosthetic mitral valve. She was admitted to the hospital because of severe pulmonary edema. On auscultation, mechanical valve sounds were absent. Transthoracic echocardiography showed an immobile mechanical valve. The patient suffered a cardiac arrest while being prepared for surgery, but she underwent successful mitral valve replacement after cardiopulmonary resuscitation. When patients with prosthetic mitral valves present with acute dyspnea, the possibility of an obstructed prosthetic valve must be considered in the differential diagnosis.     

Anticoagulation of valvular prostheses

Prosthetic valve replacement has transformed the outcome of patients with severe or poorly tolerated valvular heart disease. Between the two main families of prostheses, only mechanical prostheses require indefinite anticoagulant therapy to lower the thromboembolic risk. National and international guidelines have been published within the past decade. They have outlined how anticoagulation, essentially oral anticoagulant therapy and transient heparin, should be used. The intensity of anticoagulation depends on the type of prosthesis, its position, the presence of atrial fibrillation and the individual's risk of thromboembolism. Monitoring is based on the INR. Temporary recourse to heparin therapy is necessary for all situations in which the risk of major hemorrhage requires more flexible treatment (postoperative period, extracardiac surgery, stroke, severe hemorrhage) or when warfarin is contraindicated because of its risk of inducing malformation (pregnancy). Low molecular weight heparins are not yet authorized for use in prosthesis bearers. Nonetheless, they are being prescribed by more-and-more teams, seduced by the facility of their use, their more stable action and, usually, no need for biological monitoring. And their use is supported by the most recent guidelines, several favorable publications, and the excellent results obtained with them in treating other thromboembolic pathologies. Indispensable to lower the rate of thromboembolic events, anticoagulant therapy bears a hemorrhagic risk that is higher for prolonged and marked anticoagulation. On the other hand, despite effective anticoagulation, the occurrence of thromboemboli can lead to considering the adjunction, in certain cases, of anti-platelet aggregating agents, particularly favored in North America, and recommended in Europe for patients with a predilection for atheromas.     

Choosing a prosthetic heart valve

Although most of the available prosthetic heart valves function remarkably well, the variety of available designs attests to the inability of any single one to fulfill the requirements of the ideal valve substitute. The mechanical prostheses include the caged-ball, tilting-disc, and bileaflet valves. Tissue valves available in the United States are the Carpentier-Edwards and Hancock porcine heterograph valves. Review of several large comparative studies on valve performance reveals that the overall results with tissue and mechanical valves are about equal at the end of 10 years. The characteristics of each type of valve substitute dictates the selection of one prosthesis in preference to others for a particular patient. Mechanical prostheses are recommended for patients without contraindications for anticoagulants. Tissue valves are reserved for patients over 70 years of age or for patients in whom anticoagulation is contraindicated. Multiple other patient-related factors need to be considered in selecting the appropriate valve, including the psychosocial situation and patient preference.