Is the tricuspid position suitable for testing replacement bioprosthetic valves in the sheep model?

BACKGROUND AND AIM OF THE STUDY: Glutaraldehyde may promote calcification in xenograft tissue by the action of toxic aldehyde group residues involved in the cross-link process. Post-fixation treatment with homocysteic acid (HA) neutralizes this toxicity by bonding aldehyde groups, and enhances biocompatibility on the basis of strongly electronegative sulfonic groups. Previous studies in a rat subcutaneous model showed significant long-term mitigation of mineralization of glutaraldehyde-fixed pericardium treated with HA. This study aimed to assess the anticalcific efficacy of HA in a valvular implant in growing sheep, and establish if the tricuspid position is suitable for testing replacement bioprosthetic valves. METHODS: Eleven stented 25 mm Pericarbon bioprostheses (seven HA-treated, four standard) were implanted in the tricuspid position of growing sheep. Infective endocarditis occurred in four prostheses. Among the remaining seven, three (two HA-treated, one standard) were explanted at 91 days (mid-term), and four (two HA-treated, two standard) at 140-141 days (long-term). All explants were studied by gross, X-ray, light, transmission and scanning electron microscopy, as well as by atomic absorption spectroscopy. RESULTS: No histological and ultrastructural difference in tissue preservation were observed between HA-treated and standard Pericarbon bioprostheses, either in the mid or long term. The mean calcium content of mid-term HA-treated explants was 9.55 mg/g compared with 16.26 mg/g in mid-term standard explants. Only one late standard explant failed as a result of severe stenosis caused by massive dystrophic calcification. Among four late explants, two showed significant increase in mineralization (HA-treated, 87.45 mg/g; standard, 181.20 mg/g), while two showed calcium contents similar to those in mid-term explants (HA-treated, 11.96 mg/g; standard, 17.32 mg/g). CONCLUSION: Post-fixation treatment with HA preserves structural properties after tricuspid implantation in growing sheep. The tricuspid implant in the sheep model failed to reproduce remarkable accelerated progressive calcification in all xenografts so as to demonstrate a significant difference between HA and standard explants. The tricuspid position for testing replacement bioprosthetic valves should be abandoned, and investigations repeated with the prosthesis in the mitral position.     

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.     

Tricuspid valve replacement: bioprosthetic or mechanical valve?

Significant morbidity and mortality is associated with tricuspid valve replacement, and controversy still exists as to the ideal prosthesis in this position. This study aimed to identify the risk factors for low cardiac output and mortality, and whether bioprosthetic or mechanical valves perform better in the tricuspid position. Results of 121 tricuspid valve replacements in 104 patients between January 1966 and December 2002 were reviewed. Most patients were in New York Heart Association functional class III or IV. Perioperative mortality was 19%. On multivariate analysis, age and preoperative jaundice were significant predictors of low cardiac output; age, jaundice, atrial fibrillation, and bypass time were significant predictors of mortality. Mechanical valves were significantly more prone to thromboembolism, whereas bioprostheses suffered structural valve deterioration. There were no significant differences in anticoagulation or bleeding episodes between the two groups, nor in valve-related events, deaths, and long term survival. There was no significant difference in performance so as to recommend one type over the other, but bioprosthetic valves may be more favorable as they fail predictably.     

Stentless valves for aortic valve replacement: where do we stand?

PURPOSE OF REVIEW: Following more than a decade's experience with stentless valves and the development of better profiled stented valves, the article discusses the advantages of stentless valves regarding hemodynamic performance, left ventricular mass regression, durability and survival. RECENT FINDINGS: Recent studies show that stentless valves remain hemodynamically superior compared with modern porcine stented valves. This superiority is, however, rarely reported in comparison with modern pericardial stented valves. In general, patient-prosthesis mismatch is less frequent in stentless vs. stented valves. Recent randomized trials comparing stentless valves and modern stented valves show equivalent left ventricular mass regression at 1 year. At 10 years, stentless valve durability is excellent and comparable with that of stented valves. Recent comparative studies do not confirm the previously reported midterm survival advantages of stentless valves. SUMMARY: Improvement of stented valves has significantly reduced the hemodynamic differences between them and their stentless counterpart. Patients with small aortic annulus, however, should benefit from a stentless valve due to the better expected gradients and lower risk of patient-prosthesis mismatch. Midterm results suggest equivalent durability and survival for both prosthesis types but additional and longer-term trials are necessary to confirm these results.     

Heart valve replacement: Which valve for which patient?

The ideal heart valve substitute would show no deterioration or thrombogenicity, offer no resistance to blood flow, and be easy to implant. However, such a valve does not exist and we must accept compromises in some of these qualities based on our patients' needs. In selection of cardiac valve prosthesis, valve-related factors such as durability, thrombogenicity, and fluid dynamics should be carefully matched to patient-related factors such as age, size, life expectancy, comorbidities, plans for pregnancy, and lifestyle. In addition, surgeon- or operation-related factors should be considered. Technical aspects of implantation, ease of reoperation, and operative mortalities may tip the risk and benefit balance in a particular direction. We review currently available heart valve prostheses and the clinical factors that are involved in selection of a heart valve substitute.     

Patients' selection for transcatheter tricuspid valve interventions: Who will benefit?

Tricuspid regurgitation (TR) is a common valvular pathology and is associated with significant morbidity and mortality. However, there is no currently defined optimal management strategy: medical therapy is limited to diuretics, and tricuspid valve surgery is rarely performed and associated with high risks. This has led to the emergence of numerous transcatheter therapies that are showing promising early results but are faced with multiple challenges. The tricuspid valve anatomy is complex and variable, imaging of tricuspid valve by echocardiography can be difficult, and current grading of TR severity and right ventricular size and function is mostly subjective. Also, the optimal timing of the intervention and appropriate selection of patients who will benefit remain topics of debate with limited supporting data. In this review, we present the current challenges and considerations in patients' selection and propose a trial design and selection criteria aimed to address these limitations.     

What is the proper threshold for platelet transfusion in patients with chemotherapy-induced thrombocytopenia?

Platelet transfusion therapy is an integral part of modern oncological practice and is used to treat hemorrhage associated with thrombocytopenia. More commonly, platelets are transfused to prevent hemorrhage in thrombocytopenic patients. Conventional wisdom has suggested a threshold for prophylactic transfusion of <20x10(9)/l. Many studies now support the safety of more conservative transfusion regimes that reduce patient exposure to donors and conserve precious resources, without an increase in risk of hemorrhage. This review presents the data to support the use of a prophylactic transfusion threshold of <10x10(9)/l in patients without risk factors for hemorrhage and who have ready access to emergent medical care.     

Prosthetic valve endocarditis: what is the evidence for anticoagulant therapy?

The use of anticoagulant therapy in prosthetic valve endocarditis is a controversial management issue. Some authorities believe that anticoagulation increases the potential risk of cerebral haemorrhage after a thromboembolism whereas others, however, affirm that cessation of anticoagulation itself increases the risk of thromboembolism and subsequent morbidity and mortality. We reviewed the association of anticoagulant therapy and cerebral complications in patients with prosthetic valve endocarditis. Our results suggest that anticoagulant therapy reduces the risk of thromboembolism and is not associated with increased risk of intracranial haemorrhage.     

Porcine or human stentless valves for aortic valve replacement? Results of a 10-year comparative study

BACKGROUND AND AIM OF THE STUDY: Stentless porcine valves in the aortic position exhibit similar excellent hemodynamic performance to homografts, but have the advantage of availability. Their performance was compared over a 10-year period in a single-surgeon and single-institution series. METHODS: Demographic, operative and mortality data were obtained retrospectively. Survivors were interviewed by telephone according to a defined protocol. Definitions and analyses were in accordance with joint STS/AATS guidelines. RESULTS: A total of 408 stentless porcine and homograft aortic valve replacements (AVR) was performed between 1991 and 2001. Five patients were excluded due to incomplete data, in addition to 82 patients who underwent AVR with a free-standing root replacement technique. Hence, 321 patients (217 males, 104 females; mean age 67 +/- 12 years) had a subcoronary implant. The median time to follow up was 4.9 years (range: 2.9-6.6 years). No differences were noted between homograft and stentless porcine valves in one- and five-year freedom from structural valve deterioration (99.1 versus 97.2% and 95.7 versus 93.1%; p = 0.10), reoperation (99.2 versus 99.4% and 97.8 versus 96.7%; p = 0.45) and endocarditis (98.3 versus 99.4% and 97.4 versus 99.4%; p = 0.14). Overall one- and five-year survival comparing homograft to stentless porcine valve was 90.4 versus 92.3% and 80.8 versus 73.7%, respectively; p = 0.23. Independent predictors of mortality on multivariate analysis were: ventricular function (p < 0.0001), increasing age (p < 0.001), increasing serum creatinine (p < 0.001) and concomitant coronary surgery (p = 0.05). Treated hypercholesterolemia was independently protective against mortality, with an odds ratio of 0.26 (CI 0.10 to 0.66; p = 0.005). CONCLUSION: The porcine stentless valve, when implanted in the subcoronary position, is an excellent alternative to the homograft and shows excellent clinical performance and durability at mid term.