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PubMedDate not supplied

"Bridging" therapy with low molecular weight heparin in pregnant patients and patients with mechanical prosthetic heart valves.

A substantial body of published, peer-reviewed, trial and cohort study-based evidence, institutional data sets and expert clinical experience/opinion supports the safe and effective use of enoxaparin for anticoagulation management of non-pregnant patients with prosthetic mechanical heart valves. A comparable body of data and trial results exists, also supported by a significant and authoritative base of expert opinion, for enoxaparin-based VTE prevention and treatment of at-risk pregnant patients who do not have mechanical heart valves. In pregnant women with prosthetic mechanical heart valves, no recommendations on the use of LMWHs can be made until the availability of more data (Lovenox Injection (package insert). Available at www.aventis-us.com/PIs/lovenox. Accessed July 30, 2003. Aventis Pharmaceuticals 2003).

Clinical Trials as Topic↗
PubMed1986

Penetration of pefloxacin in human heart valves.

Pefloxacin concentrations were measured by HPLC in serum, subcutaneous tissue, heart muscle and heart valves of 41 patients receiving a one hour infusion of 800 mg iv 4, 8, 12, 18, or 24 h before open heart surgery for prosthetic cardiac valve insertion. In all but three of the 46 valvular samples, pefloxacin concentrations were higher than the mode MIC of Staphylococcus, Enterobacteriaceae and Pseudomonas microorganisms causing infections following open heart surgery. Pefloxacin therefore has good penetration of heart valves and is present for up to 24 h. It could be considered as a useful drug in the prophylaxis of cardiac surgery and in therapy of bacterial endocarditis due to susceptible micro-organisms.

Adolescent↗
PubMed1998

Up to eight years' follow-up of 997 patients receiving the CarboMedics prosthetic heart valve.

BACKGROUND: The aim of the study was to evaluate our clinical experience with the CarboMedics Heart Valve Prosthesis. METHODS: Nine hundred ninety-seven consecutive patients underwent mechanical valve implantation (aortic, 771; mitral, 169; double, 52; tricuspid, 5) with this prosthesis from September 1987 through December 1993. The mean age was 62.3+/-13.7 years (range, 0.4 to 84 years); 56.6% (564 patients) were men. Four hundred seventy patients (47.1%) underwent additional surgical procedures. Mean follow-up was 4.1+/-2.2 years (range, 0 to 8.3 years) with a total of 4,040 patient-years. RESULTS: Early mortality was 5.0% (50/997; aortic, 4.4%; mitral, 6.4%; double, 9.6%). Late mortality was 14.8% (140/947). Survival at 7 years was 75.9%+/-1.8% (aortic, 78.4%+/-2%; mitral, 70.7%+/-4.5%; double, 60.8%+/-7.4%). When matched for sex and age and compared with the normal Norwegian population, our patients had an increased standard mortality ratio in both men (1.9+/-0.4) and women (2.9+/-0.6). The linearized rate of major thromboembolism was 0.9% per patient-year, valve thrombosis 0.2% per patient-year, major bleeding event 0.6% per patient-year, paravalvular leak needing reoperation 0.5% per patient-year, prosthetic valve endocarditis 0.1% per patient-year, and of all reoperations 0.6% per patient-year. CONCLUSIONS: The CarboMedics Heart Valve Prosthesis has incidences of morbid events comparable with or better than reported for other mechanical valves.

Adolescent↗
PubMed1993

Cytotoxicity of amphotericin B for fibroblasts in human heart valve leaflets.

The cytotoxicity of amphotericin B (Fungizone, containing deoxycholate) was investigated for human heart valve leaflet fibroblasts. Leaflets were obtained from human aortic and pulmonic valves and incubated in culture medium containing amphotericin B. Upon completion of incubation, some leaflet sets were analyzed immediately, and others were cryopreserved and stored below -135 degrees C. Quantitative fibroblast viability assays were performed. The results can be summarized by consideration of the data obtained from autoradiographic analysis of [3H]proline incorporation into collagen. Incubation with 10 micrograms/ml amphotericin B at 37 degrees C resulted in approximately 11% loss of fibroblast viability. After cryopreservation, the leaflets incubated with amphotericin B experienced an additional 42% loss of fibroblast viability. These results indicate that use of amphotericin B, in this form, is ill advised for treatment of human heart valves prior to cryopreservation.

Amphotericin B↗
PubMed1977

[Blood traumatization after heart valve replacement (author's transl)].

Blood traumatization after heart valve reconstruction or replacement was checked in 47 patients. Among the types of prostheses tested the Beall-valve caused the highest subclinical hemolysis, the Björk-Shiley-valve the lowest. In the aortic position the values for the Björk-valve were better than those for the Starr-valve. In cases with double valve replacement (Starr in aortic, Beall in mitral position) hemolysis was not much higher than in cases with single Beall mitral valve replacement. Clinical hemolytic anemia was only observed in 3 patients, 2 of them being affected with paravalvular leakage. In cases of paravalvular leakage parameters of hemolysis was very high and became normalized after successful repair in 2 patients.

Adult↗
PubMed1996

Comparison of high-dose with low-dose aspirin in patients with mechanical heart valve replacement treated with oral anticoagulant.

BACKGROUND: There are no reported studies on the safety and efficacy of low-dose aspirin with low-intensity oral anticoagulation in patients with heart valve replacement. In this study, we compared the use of 100 mg/d aspirin with 650 mg/d aspirin in the prevention of systemic embolism and vascular death in patients with heart valve replacement who were being treated with oral anticoagulants with a target international normalized ratio (INR) of 2.0 to 3.0. METHODS AND RESULTS: Four hundred nine of 416 consecutive patients who had cardiac valve replacement were randomized in open allocation into one of two groups; both groups were treated with oral anticoagulant therapy with a target INR of 2.0 to 3.0. Two hundred seven patients who received 100 mg/d aspirin for an average of 24.1 months were compared with 202 patients who received 650 mg/d aspirin for an average of 21.7 months in a randomized-treatment, open-allocation study. There were no significant differences in systemic embolism, vascular death, or total death rates between the low- and high-dose aspirin treatment groups (0.5 and 1.1, 1.2 and 0.5, and 4.6 and 2.5 per 100 patients/y, respectively). The total number of hemorrhagic events was 13.4 per 100 patients/y in the high-dose aspirin group and 7.9 per 100 patients/y in the low-dose aspirin group (P = .035), but the rate of bleeding was influenced by dipyridamole in the 650-mg aspirin group. CONCLUSIONS: In patients with mechanical heart valve replacements, low-dose aspirin (100 mg/d) in conjunction with oral anticoagulants at an INR of 2.0 to 3.0 is as effective as the use of high-dose aspirin (650 mg/d) in the prevention of systemic embolism.

Administration, Oral↗
PubMedDate not supplied

Two-component laser Doppler anemometer for measurement of velocity and turbulent shear stress near prosthetic heart valves.

The velocity and turbulent shear stress measured in the immediate vicinity of prosthetic heart valves play a vital role in the design and evaluation of these devices. In the past hot wire/film and one-component laser Doppler anemometer (LDA) systems were used extensively to obtain these measurements. Hot wire/film anemometers, however, have some serious disadvantages, including the inability to measure the direction of the flow, the disturbance of the flow field caused by the probe, and the need for frequent calibration. One-component LDA systems do not have these problems, but they cannot measure turbulent shear stresses directly. Since these measurements are essential and are not available in the open literature, a two-component LDA system for measuring velocity and turbulent shear stress fields under pulsatile flow conditions was assembled under an FDA contract. The experimental methods used to create an in vitro data base of velocity and turbulent shear stress fields in the immediate vicinity of prosthetic heart valves of various designs in current clinical use are also discussed.

Blood Flow Velocity↗
PubMed2002

The pulmonary bioprosthetic heart valve: its unsuitability for use as an aortic valve replacement.

BACKGROUND AND AIM OF THE STUDY: The porcine pulmonary bioprosthetic heart valve represents an alternative means of aortic valve replacement (AVR), though knowledge of its biomechanical function and characteristics is limited. The valve has potential advantages over the aortic bioprosthesis; notably, it lacks the muscular shelf of the right coronary cusp of the latter bioprosthesis. The study aim was to investigate the suitability of the porcine pulmonary bioprosthetic valve for AVR. METHODS: Porcine pulmonary and aortic roots were zero pressure-fixed with 0.5% buffered glutaraldehyde, characterized, and compared with fresh porcine pulmonary and aortic roots. The in-vitro analysis included assessment of mechanical properties, hydrodynamic function, geometry of the pulmonary root, and durability. RESULTS: The fixed pulmonary roots and fresh aortic roots were similar in certain aspects of mechanical response, notably leaflets in the radial direction and the root wall. The fixed pulmonary root was slightly more compliant than the fixed aortic root, and this led to an improvement in forward flow hydrodynamic function. The reverse flow hydrodynamic function of the pulmonary roots was poor; fresh pulmonary roots exhibited a trivial closed valve regurgitant volume. On fixation, this characteristic was aggravated, leading to a gross closed valve regurgitant volume in 50% of all fixed pulmonary roots. The cause of leakage was identified as a prolapsed anterior leaflet. Durability of the fixed pulmonary root was also inferior to that of the fixed aortic root; three fixed pulmonary roots subjected to accelerated fatigue testing showed signs of leaflet macroscopic damage. CONCLUSION: Overall, the performance of the porcine pulmonary bioprosthesis was far inferior to that of the currently used porcine aortic bioprosthesis. Hence, the porcine pulmonary bioprosthetic valve was deemed unsuitable for AVR.

Animals↗
PubMed1986

Present status of thromboembolic complications in patients with prosthetic heart valves.

When the incidence of thromboembolism (TE) as a complication was investigated in 171 patients with prosthetic heart valves using pyrolytic carbon, 10 cases were identified in a mean follow-up period of 2.43 years. Of these 10, two patients had died. The incidence of TE as a percentage per patient--year was 2.41 on the whole, 2.15 in patients with aortic valve replacement (AVR), 2.48 in patients with mitral valve replacement (MVR) and 2.52 in patients with double valve replacement (DVR). It is evident that TE is still an important complication following prosthetic heart valve surgery and the patient's return to society. TE tended to occur somewhat more often in cases of MVR and DVR than in those of AVR. TE was apt to appear early in the postoperative period, often within a year, and was often seen in the brain. To prevent TE, it is necessary to carefully control blood coagulation by the administration of anticoagulants.

Adult↗
PubMed1989

[Late results of the treatment of mitral valve defects by implantation of an artificial heart valve].

The authors analyzed a group of 50 patients with an implanted artificial mitral valve. Group I consisted of 20 patients with an isolated left venous ostial stenosis. Group II consisted of 23 patients with a complex mitral disease, and group III--of 7 patients with mitral incompetence. Depending on the degree of improvement, the first two groups were divided into two subgroups: group Ia (13 patients) and group IIa (15 patients) with full clinical improvement, and group Ib (7 patients) and group IIb (8 patients) still requiring cardiological drugs and from time to time--dehydrating drugs. The observation time was from 1.5 to 4 years (on the average 39 months). In all the patients the artificial valve functioned properly. Before and after surgery the clinical state was evaluated according to NYHA, heart volume index (WOS), cardiopulmonary index (WSP) by a radiological examination, left-ventricular diastolic dimension (WRLK), left-ventricular systolic dimension (WSLK), left-ventricular end-diastolic volume index (WOKRLK), left-ventricular end-systolic volume index (WOKSLK), right-ventricular diastolic dimension (WRPK) and left atrium were evaluated by means of echocardiographic examination. Before surgery all the patients underwent the measurements of pressures in the pulmonary circulation, pulmonary resistance and heart index. The authors found a correlation between a degree of improvement after surgery and a functional group before surgery. Eleven patients from functional group III according to NYHA had been (before surgery) in a state of advanced circulatory failure (IV functional group). Clinical improvement was confirmed by statistically significant decrease in heart dimension evaluated by radiological and echocardiographic examinations. In group I left atrium dimension (LP) was significantly statistically larger in patients with incomplete clinical improvement. The authors also found a dependence of a distant result on a degree of hypertension in pulmonary artery, increased pulmonary resistance and decrease in stroke volume.

Adolescent↗
PubMed2003

INR self-management permits lower anticoagulation levels after mechanical heart valve replacement.

BACKGROUND: The Early Self Controlled Anticoagulation Trial (ESCAT I) showed that anticoagulation self-management after mechanical heart valve replacement decreased complication rates by maintaining INR levels closer to the target range than International Normalized Ratio (INR) home doctor management. The therapeutic range for the INR in that study was between 2.5 and 4.5 for all positions of prosthetic valves. ESCAT II should find out whether lowering the target range for INR self-management would further reduce complication rates. METHODS: ESCAT II is a prospective controlled randomized (valves: St. Jude Medical Standard or Medtronic Hall, treatment: conventional/low-dose) multicenter study with 3,300 patients. We present interim results of 1,818 patients. 908 were categorized as having a low-dose target range, which was INR 1.8 to 2.8 for prostheses in aortic position and 2.5 to 3.5 for prostheses in mitral position or in combined valve replacement. The control group (conventional group) with 910 patients aimed at an INR of 2.5 to 4.5 for all valve positions. RESULTS: In the conventional group, 74% of INR values measured were within the therapeutic range. In the low-dose group, 72% of the values were within that range. The linearized thromboembolism rate (% per patient year) was 0.21% for both groups. The bleeding complication rate was 0.56% in the low-dose regimen group versus 0.91% in the conventional group. CONCLUSIONS: Early onset INR self-management under oral anticoagulation after mechanical heart valve replacement enables patients to keep within a lower and smaller INR target range. The reduced anticoagulation level resulted in fewer grade III bleeding complications without increasing thromboembolic event rates.

Anticoagulants↗
PubMedDate not supplied

The evolution of bioprosthetic heart valve design and its impact on durability.

Bioprosthetic heart valves have evolved over the years into remarkably useful and predictable devices. During this process, a number of specific designs have come and gone, and a few have remained. Many design changes were successful, and many were not. This article will describe the successes and failures of the various bioprosthetic valve designs and will detail the specific reasons why a particular design change succeeded or failed to improve bioprosthetic valve performance.

Animals↗
PubMed1990

Relative survival of patients after heart valve replacement.

Long-term results after prosthetic heart valve replacement are usually presented in actuarial terms, which do not take into account the background mortality of the general population. The calculations of the relative survival, which is the ratio between the observed survival in a group of patients during a specified time interval and the survival expected from the general population experience, permit correction for important demographic variables. We have analysed the long-term relative survival rates in a consecutive series of 841 Norwegian patients who, on the basis of clinical symptoms, underwent aortic (AVR, n = 617), mitral (MVR, n = 146), and double (AVR + MVR, n = 78) valve replacement between June 1977 and January 1985. The follow-up was closed on May 1st 1986, was 100% complete and included 2056 patient-years. The actuarial survival data for the total cohort was 75.1%, and for AVR, MVR and DVR, 77.9, 69.7 and 63.0%, respectively. The corresponding figures for the relative survival were 83.5, 87.0, 76.6 and 69.1%, respectively. Within the subgroup undergoing AVR, our analysis demonstrated a poor prognosis in those who were operated for pure aortic regurgitation or endocarditis, as well as in those who received the smallest valve size prosthesis due to a narrow aortic root. In this analysis, as in the analysis of the total material, we observed that the differences between survival in the patients and in the general population were of smaller magnitude when based on relative survival rates than when analysed in the standard (actuarial) way.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1997

[Prosthetic heart valve thrombosis: a 3-year experience].

A series of 12 patients with 16 episodes of prosthetic heart-valve thrombosis over 3 years is presented. Most episodes affected mitral or tricuspid bileaflet prostheses. All patients were inadequately anticoagulated at the time of thrombosis. The clinical presentation was acute and severe in 6 patients, and subacute or chronic in the rest. Physical examination was suggestive of stuck valves in most cases. Transthoracic echocardiography revealed increased transvalvular gradients in most. However, clearer evidence of valve thrombosis was obtained from transesophageal echocardiography or fluoroscopy. 9 patients eventually had their valves re-replaced successfully, and the preoperative diagnosis was confirmed in all. 5 patients were operated as soon as the diagnosis was established. and an additional 4 were operated after failure of anticoagulation. In 4 patients the valve leaflets became completely mobile after a course of thrombolysis. Prosthetic valve thrombosis is a severe and potentially fatal complication in patients with mechanical heart valves. Alertness of physicians at all levels- the general practitioner, the internist and the cardiologist- to the possibility of valve thrombosis and to its clinical presentation may lead to prompt and earlier diagnosis and to comprehensive therapy.

Adolescent↗
PubMed1997

Wear patterns in the Sorin Bicarbon mechanical heart valve: a clinical explant study.

BACKGROUND AND AIMS OF THE STUDY: Mechanical heart valve prostheses are subject to wear due to impact and friction between the occluder(s) and valve housing. Reference data on the extent of wear in vivo is lacking. Therefore, the aim of this study was to describe the wear pattern in Sorin Bicarbon valves explanted from humans for comparison with the findings established in an earlier in vitro study. METHODS: We investigated eight valves explanted from seven patients, which had been functioning for more than six months and were returned to the Sorin Company for investigation. The protocol comprised: (i) initial visual inspection on receipt; (ii) stereomicroscopy after cleaning and disassembly; (iii) computed planimetry of the worn areas in the housing; (iv) pivot surface profilometry; and (v) scanning electron microscopy. RESULTS: All wear depths and exposed areas of titanium were less than that predicted from in vitro figures. No valves were explanted due to mechanical failure and none of the patients had reported peripheral embolic events which could be attributed to valve wear. The extent of wear was comparable with that of other valves. CONCLUSIONS: This descriptive study did not indicate any association between the Bicarbon valve wear characteristics and clinical complications. Clinical studies on valve performance are of paramount importance for elucidating this issue. The establishment of an independent body for studying explanted valves in collaboration with the manufacturers may promote the publication of findings which are of interest for the entire medical community.

Adult↗
PubMedDate not supplied

An instrument for the measurement of in vitro velocity and turbulent shear stress in the immediate vicinity of prosthetic heart valves.

The measurements of velocity and turbulent shear stress in the immediate vicinity of prosthetic heart valves play a vital role in their design and evaluation. In the past, hot-wire/film and one-component laser Doppler anemometer (LDA) systems have been used extensively. Hot-wire/film anemometers, however, have some serious disadvantages, such as not being able to measure the directionality of the flow, disturbing the flow field with the probe, and requiring frequent calibration. One-component LDA systems do not have these problems, but they cannot measure turbulent shear stresses directly. Since these measurements are essential, and are not available in the open literature, a two-component LDA system was assembled to measure velocity and turbulent shear stress fields under pulsatile flow conditions. The experimental methodology used to create an in vitro data base of velocity and turbulent shear stress fields in the immediate vicinity of various designs of prosthetic heart valve in current clinical use is also discussed in this paper.

Aortic Valve↗
PubMed2001

Stentless bioprosthetic heart valve research: sheep versus primate model.

BACKGROUND: The mild inflammatory response against stented bioprosthetic heart valves in the sheep model is often opposed by a more distinct response in failing human implants. With the emergence of stentless root prostheses with their significantly larger proportion of tissue interacting with the immune system of the host, a more relevant animal model than the sheep may be needed. METHODS: Valved, porcine aortic roots of 5 cm length were fixed in 0.2% glutaraldehyde and implanted in the upper descending aorta of Merino sheep (n = 5; 43+/-3 kg) and Chacma baboons (n = 5; 17+/-3 kg). After 6 weeks of tissue calcification, pannus outgrowth and inflammation were assessed by atomic absorption spectrophotometry, histologic damage scoring (0 to 3), image analysis, and transmission electron microscopy. RESULTS: The main difference between the two animal models was in aortic wall calcification (64.8+/-39.8 microg/mg in the sheep model versus 4.1+/-5.9 microg/mg in the primate model; p > 0.005). In both models, leaflet calcification was negligible (2.6+/-2.4 microg/mg in the sheep versus 2.5+/-1.9 microg/mg in the primate), and the overall extent of inflammation was comparable (1.2+/-0.8 versus 0.98+/-0.7; p = 0.18 in the sheep and the primate, respectively). Qualitatively, the sheep demonstrated a macrophage-dominated reaction whereas the inflammatory demarcation often resembled a granulocyte-dominated xenograft response in the primate. Pannus outgrowth was comparable in length (8.4+/-2.3 mm versus 9.1+/-4.3 mm proximally and 7.1+/-3.4 mm versus 7.4+/-5.1 mm distally, in the sheep and baboon, respectively; p > 0.05). CONCLUSIONS: Our results confirm the sheep as a significantly stronger calcification model for stentless aortic heart valves than the primate. Remaining antigenicity of porcine tissue as a result of incomplete cross-linking, however, elicits a distinctly stronger xenograft-type reaction in the primate model.

Animals↗