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PubMed2005

Effect of L-carnitine on cardiomyocyte apoptosis and cardiac function in patients undergoing heart valve replacement operation.

The effects of L-carnitine, as an ingredient of cardioplegia solution, on cardiac function and cardiomyocyte apoptosis in patients undergoing heart valve replacement operation were investigated. Twenty-three cases undergoing heart valve replacement with cardiopulmonary bypass (CPB) were randomly allocated into two groups: L-carnitine group (n = 12, 12 g/L L-carnitine was put in the ST. Thomas cardioplegia) and control group (n = 11, identical to the L-carnitine group except that normal saline was administered instead of L-carnitine). Serum cardial troponin I (cTnI) levels, the left ventricular ejection fraction (LVEF), and cardiac index (CI) were measured perioperatively. A bit of myocardial tissue obtained from right atria was taken before CPB and by the end of intracardiac procedure to undergo electron microscopy examination and estimate apoptosis by terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL). From the end of CPB to 3 days after operation, the serum levels of cTnI in the L-carnitine group was significantly lower than that in the control group (P < 0.05). Heart color ultrasonogram showed that the CI index and LVEF at 7th day postoperatively in the L-carnitine group were significantly higher than in the control group (P < 0.05). Compared to the control group, L-carnitine significantly alleviated the morphologic changes of cardiac muscle cells (electron microscopy examination) and decreased the amounts of apoptotic cardiac muscle cells (TUNEL). Furthermore, the dosage of vasoactive drugs used after operation was significantly less in the L-carnitine group (P < 0.01). It was concluded that L-carnitine cardioplegia solution could improve cardiac function in patients undergoing heart valve replacement operation and alleviate CPB-mediated apoptosis of cardiac muscle cells.

Adult↗
PubMed1997

Nineteen-millimeter aortic St. Jude Medical heart valve prosthesis: up to sixteen years' follow-up.

UNLABELLED: BACKGROUND; Prosthetic valve replacement in a small aortic root without annulus enlargement raises concern about its long-term benefits. METHODS: Between July 1979 and June 1994, 104 (18%) of 593 patients underwent aortic valve replacement using the 19-mm St. Jude Medical heart valve prosthesis. There were 93 women and 11 men, with a mean age of 66.2 +/- 10.6 years. Forty-four patients (42%) were 70 or more years old. The mean body surface area was 1.61 +/- 0.16 m2 (range, 1.2 to 2.1 m2). Forty-nine patients (47%) underwent concomitant procedures; 23 patients (22%) required coronary artery bypass grafts and 25 patients (24%), mitral valve replacement. Ninety-eight patients (94%) presented in New York Heart Association class III and IV. RESULTS: The operative mortality was 7.6% (8 patients). Follow-up was 100% with a mean of 5.48 +/- 3.73 years (range, 1 to 16 years) and a total of 708 patient-years. There were 18 late deaths, with a mortality of 2.5% patient-years. The incidence of thromboembolism was 0.4% patient-years (3 patients) and anticoagulant-related morbidity was 0.85% patient-years (6 patients). Long-term survival in the two groups with a body surface area of less than 1.7 m2 and 1.7 m2 or more was not statistically different (p = 0.30). The univariate analysis with body surface area as a predictor of mortality showed that a larger body surface area had no effect on the long-term mortality (chi2 p value = 0.36). Survival for 5 and 10 years with the 95% confidence interval was 80.6% +/- 8.3% and 61.6% +/- 15%. Freedom from thromboembolism was 96.3% +/- 4.2% and anticoagulant-related hemorrhage was 91.8% +/- 6.8% at the end of 16 years. Cox proportional hazards model, with time-dependent covariates, showed that events of thromboembolism, anticoagulant-related hemorrhage, and myocardial infarction during follow-up increased the risk of late death (risk ratio, 9.5, 10.3, and 32.8, respectively). The age at operation was an independent risk factor, with decreased survival with age 70 or more years (p = 0.0002). However, body surface area (p = 0.97) and concomitant cardiac procedures (p = 0.86) were not statistically significant predictors of death. CONCLUSIONS: The long-term performance of the 19-mm St. Jude Medical heart valve prosthesis in the small aortic root is satisfactory irrespective of the body surface area, and it is a viable alternative for such patients.

Adult↗
PubMed1992

Problems associated with mechanical heart valve sounds.

A cross-sectional study of 50 randomly selected patients 12-36 months following mechanical heart valve replacement with Bjork-Shiley tilting disc valves was undertaken to investigate the factors which affect perception of, and reaction to, sounds generated by mechanical heart valves implanted in patients. Numerous problems were generated by the valves, including annoyance (68%), sleep disturbance (52% in patients; and 46% in patients' partners), interference with concentration (36%) and social embarrassment (28%). These findings are not affected by the measured level of sound or any variation in the number or anatomical position of the valve(s), though age and sex do seem to matter, more problems being reported by younger patients and those of the female sex. Aspects of the patient's personality did not seem to alter the difficulties experienced, though a high level of psychological morbidity was identified in the group as a whole. Most patients experience problems due directly to the noise generated by their valve and should be adequately warned of this before operation. This should also be taken into consideration in designing and evaluating new valve prostheses.

Adaptation, Psychological↗
PubMed1993

Mapping of glutaraldehyde-treated bovine pericardium and tissue selection for bioprosthetic heart valves.

Glutaraldehyde-crosslinked bovine pericardium is widely used in bioprosthetic heart valve fabrication. In an attempt to set a scientific basis for more reproducible tissue selection, we produced and analyzed topographical maps of glutaraldehyde-treated bovine pericardium. Whole pericardia were divided into specific anatomical areas and their thickness was measured and mapped on templates. In each area, the suture holding power was determined in both parallel and perpendicular (to the base-apex line) directions; analyses of the tearing patterns in each fragment were used to evaluate predominant fiber orientation, and observations were confirmed by polarized light microscopy. Complete maps were superimposed graphically to aid in the selection of certain areas that would have known fiber orientation, high suture holding power, and suitable thickness. Our results describe regional heterogeneity of bovine pericardial structure and mechanical properties, specifically demonstrating variations in thickness, suture holding power, and collagen fiber orientation. Two areas of choice (representing about 35% of the total) were described as suitable for use in bioprosthetic heart valve fabrication.

Animals↗
PubMed2004

Flow-induced platelet activation in mechanical heart valves.

BACKGROUND AND AIM OF THE STUDY: A study was conducted to measure in vitro the procoagulant properties of platelets induced by flow through mechanical heart valves. METHODS: The procoagulant activity of platelets was measured using a real-time assay of platelet activation state (PAS), which was based on a modification of the prothrombinase method. Acetylated prothrombin was used instead of normal prothrombin in this assay in order to eliminate the positive feedback effect of thrombin. This enabled a direct comparison between thrombin generation rates in the assay and the flow stresses that induce platelet activation. Gel-filtered platelets (10(5) per microliters) were circulated through a left ventricular assist device with two Björk-Shiley mono-leaflet mechanical heart valves mounted in opposition, and platelet activation state was measured over 30-min time courses. The results were compared with two configurations in which the leaflet motion of one of the valves was restricted (severely restricted and mildly restricted), mimicking defective function of a compromised valve in vivo, and with a control lacking valves. RESULTS: The severely restricted valve activated the platelets at a rate eight-fold higher than with unrestricted valves, and three-fold higher than with mildly restricted valves. Both restricted valves activated platelets at rates significantly higher than either the control (no valves) or the unrestricted valve. CONCLUSION: Flow through compromised mechanical heart valves causes platelet activation, which can be measured with a modified prothrombinase assay system. The ability to perform sensitive quantitative measurements in cardiovascular devices in vitro may have a significant impact on the design and development of these devices.

Heart Valve Prosthesis↗
PubMed1981

[Studies of interventricular septal motion after heart valve replacement by two-dimensional echocardiography and thallium 201 scintigraphy (author's transl)].

Etiology of abnormal interventricular septal motion detected by M-mode echocardiography after heart valve replacement was studied by two-dimensional echocardiography and thallium 201 scintigraphy in three patients with valvular heart disease (two with mitral regurgitation, and one with aortic regurgitation). M-mode and two-dimensional echocardiograms were recorded before and after heart valve replacement, using Aloka SSD-800. After intravenous injection of 2.0 mCi of ionic thallium 201, myocardial images were recorded with a scintillation camera (Searle PHO Gamma V) with converging collimator. Abnormal interventricular septal motion (systolic anterior motion) was observed echocardiographically in all of three patients after mitral or aortic valve replacement. Two-dimensional echocardiogram showed systolic anterior motion of the whole heart towards the anterior chest wall, though the left ventricle itself contracted normally. Thallium 201 scintigram showed no significant perfusion defects of the left ventricular wall including ventricular septum. No findings showing conduction disturbance, right ventricular volume overload or pericardial effusion were observed after heart valve replacement.

Adult↗
PubMed1995

The epidemiology of prosthetic heart valves in the United States.

The Center for Devices and Radiological Health of the Food and Drug Administration, in collaboration with the National Center for Health Statistics, conducted the Medical Device Implant Supplement to the 1988 National Health Interview Survey, generating the 1st available population-based estimates of the use of prosthetic heart valves in the United States. The 1988 National Health Interview Survey was a massive, nationally representative cross-sectional survey that encompassed 47,485 households and 122,310 individuals. Data from the Medical Device Implant Supplement indicate that an estimated 253,283 persons with 279,175 heart valves were present in the civilian, non-institutionalized US population (population prevalence of 1.1/1,000, 95% CI 0.8-1.3). Prevalence of valve prostheses ranged from 0.2 per 1,000 in those age 44 and under to 5.3 per 1,000 in those 75 years of age and older. Age-adjusted prevalence of valve prostheses did not differ significantly according to sex, race, region of residence, education, or income of recipients. Two thirds of aortic valve recipients identified by the survey were male, compared with only one third of mitral valve recipients. Approximately two thirds of both aortic and mitral valve implants were reported as mechanical. Reported use of anticoagulative agents was significantly more common in recipients of mechanical than of bioprosthetic valves. The single most common reported reason for prosthetic valve implantation was rheumatic heart disease. These data provide useful epidemiologic and public health planning information on prosthetic heart valve use.

Adult↗
PubMed1978

Heart valve replacement in the elderly.

From January 1973 to December 1976, 70 operations for heart valve replacement were performed on 68 patients aged 65--75 years. These comprised 40 aortic valve replacements, 27 mitral valve replacements, and three aortic and mitral valve replacements. Three patients died within 30 days of operation (early mortality 4.3%), and five died 12 weeks to three years after operation. Four patients showed no improvement. The results were excellent or good in the remaining 56 patients. Valve replacemnt can restore to a useful independent life elderly patients who would otherwise be a burden on costly social and medical domiciliary services. The indications for valve surgery in the elderly should therefore be the same as in any other age group.

Aged↗
PubMed1999

Low-dose oral anticoagulation and antiplatelet therapy with St. Jude Medical heart valve prosthesis.

BACKGROUND AND AIM OF THE STUDY: Since 1986, the St. Jude Medical (SJM) mechanical heart valve prosthesis has been implanted in patients at the authors' institution. We present our experience of low-dose oral anticoagulation and antiplatelet therapy following SJM valve implantation. METHODS: Among 2,585 patients (mean age 40.3 +/- 13.5 years) living in a rural environment, 865 underwent aortic valve replacement (AVR), 1,231 mitral valve replacement (MVR) and 489 double valve replacement (DVR). All patients received 2.5 mg/day warfarin and a combination of antiaggregation therapy (dypridamole 3 x 75 mg/day plus aspirin 100 mg/day), irrespective of their prothrombin time and cardiac rhythm. RESULTS: Postoperatively, 139 adverse events occurred (51 in AVR patients, 58 in MVR, 30 in DVR). Operative mortality rate was 5.9%, 4.7% and 6.1%, respectively, in the three groups (overall mortality rate 5.4%). The most frequent cause of operative mortality was low cardiac output. During follow up, there were 88 anticoagulant hemorrhages (1.2%/patient-year (pt-yr)), 11 paravalvular leaks (0.2%/pt-yr), 52 thromboembolisms (0.7%/pt-yr), 60 mechanical valve thromboses (0.8%/pt-yr) and 78 reoperations (1.1%/pt-yr). These complications occurred in 101 patients after AVR, in 125 after MVR, and in 63 after DVR (4.2%, 3.7% and 4.6% per pt-yr, respectively). Patient age (p = 0.0004), concomitant surgery (p = 0.0017) and late valve-related complications (p = 0.0159) were statistically significant mortality factors after AVR. Previous surgery was a significant risk factor for operative mortality after MVR (p <0.05). Female gender (p = 0.0059) and age (p = 0.017) were significant risk factors for operative mortality after DVR (p <0.01). CONCLUSIONS: Following implantation of the St. Jude Medical mechanical heart valve prosthesis, a fixed dose of 2.5 mg/day warfarin and combined dipyridamole/aspirin provided satisfactory results in terms of thrombosis, embolism and bleeding.

Administration, Oral↗
PubMed1998

Retrieval analysis of mechanical heart valves: impact on design and clinical practice.

Explanted mechanical heart valves were examined nondestructively, and the findings were related to guidelines, technical reports, and other information to judge the risk of failure and its possible impact on valve design and clinical practice. Diagnoses for single valves could be made, but risks and rates of failure for patient populations could not be predicted due to insufficient information concerning the manufacturing process and valve and patient numbers. Based on the results of this study and the principle that decisions on recalls and patient counseling must be based on scientific knowledge rather than on wait and see policies, the following is recommended: registration of all implanted valves, follow-up of a large cohort of valve carriers, comparison of wear test results of preimplant and postretrieval valves, maintenance of a reference stock of valves and materials, and submission of failure scenarios to certifying bodies.

Guidelines as Topic↗
PubMed2003

Thoracic Surgery Directors Association Award. Bone marrow as a cell source for tissue engineering heart valves.

BACKGROUND: This study was designed to assess the feasibility of using ovine bone marrow-derived mesenchymal stem cells to develop a trileaflet heart valve using a tissue engineering approach. METHODS: Bone marrow was aspirated from the sternum of adult sheep. Cells were isolated using a Ficoll gradient, cultured, and characterized based on immunofluorescent staining and the ability to differentiate down a specific cell lineage. Two million cells per centimeter squared were delivered onto a polyglycolic acid (PGA), poly-4-hydroxybutyrate (P4HB) composite scaffold and cultured for 1 week before being transferred to a pulse duplicator for an additional 2 weeks. The tissue-engineered valves were assessed by histology, scanning electron microscopy, and biomechanical flexure testing. RESULTS: Cells expressed SH2, a marker for mesenchymal stem cells, as well as specific markers of smooth muscle cell lineage including alpha-smooth muscle actin, desmin, and calponin. These cells could be induced to differentiate down an adipocyte lineage confirming they had not fully committed to a specific cell lineage. Preliminary histologic examination showed patchy surface confluency confirmed by scanning electron microscopy, and deep cellular material. Biomechanical flexure testing of the leaflets showed an effective stiffness comparable to normal valve leaflets. CONCLUSIONS: Mesenchymal stem cells can be isolated noninvasively from the sternum of sheep and can adhere to and populate a PGA/P4HB composite scaffold to form "tissue" that has biomechanical properties similar to native heart valve leaflets. Thus, bone marrow may be a potential source of cells for tissue engineering trileaflet heart valves, particularly in children with congenital heart disease.

Animals↗
PubMed1978

Simultaneous morphological and stress-strain studies of the fibrous components in wet heart valve leaflet tissue.

Simultaneous morphological and stress-strain studies have been carried out on heart valve leaflet tissue maintained in its unaltered functional condition. A microtensile tissue testing device is described which inserts directly into the stage of an optical microscope fitted with a Nomarski interference contrast facility. Glutaraldehyde fixation of tissue subjected to different levels of loading reveals that the current stressed state of the collagen fibers is "frozen" in by crosslinking process, and as a consequence marked alterations in the preserved tissue properties are produced. This is shown to be relevant to the preparation of the glutaraldehyde treated heterograft heart valve. The mechanical roles of the collagen and elastin components are investigated and a "complementation" mechanism is postulated whereby the widely different mechanical properties of the two types of fibers are combined in a non-competing manner to produce a diversity of composite tissue characteristics.

Animals↗
PubMedDate not supplied

Structural evaluation of porcine heart valve prostheses with radiofrequency ultrasound.

BACKGROUND: Bioprosthetic heart valve use is limited by progressive degeneration. Early degenerative changes are often occult, making assessment of tissue integrity difficult. Ultrasound tissue characterization may detect alterations in tissue structure and allow early detection of leaflet degeneration. METHODS: Using a modified echocardiographic unit (Acuson), radiofrequency (RF) integrated backscatter amplitude (IBA) (integral/RF/dt) was measured in 38 leaflets from nine explanted and six control porcine valves. Regions of interest in each leaflet were studied using four ultrasound frequencies. Radiographic gray scale mean and leaflet thickness were measured at each region of interest. Percent collagen and mineral were calculated for each region of interest using color-image processing of histologic sections and compared to IBA. RESULTS: IBA values for control vs. explanted leaflets were (mean value+/-standard deviation): 8.2+/-4.69 dB vs. -4.7+/-4.64 dB at 7.0 MHz; -5.8+/-4.34 dB vs. -3.1+/-5.34 dB at 5.0 MHz; -3.8+/-3.38 dB vs. -2.1+/-3.18 dB at 3.5 MHz; and -9.0+/-4.58 dB vs. -7.1+/-4.25 dB at 2.5 MHz. Collagen content was 27.7+/-8.50% vs. 33.2+/-10.90%, mineral content was 0.1+/-0.10% vs. 2.1+/-4.30%, and radiographic gray scale mean was 150.6+/-1.96 vs. 145.3+/-5.14 for control vs. explanted leaflets, respectively. For control and explanted leaflets IBA, collagen content, mineral content, and radiographic gray scale mean were different (control vs. explanted P<0.05). Leaflet thickness was also noted to be different between the two groups. IBA was different among explanted leaflets with low, medium, and high mineral content. CONCLUSION: IBA was found to be a useful technique to differentiate normal from explanted porcine prosthetic valves in vitro. This method may be useful in the serial assessment of bioprosthetic leaflet degenerative properties in vivo.

Adult↗
PubMed1996

Transcranial Doppler detection of microemboli in prosthetic heart valve patients: dependency upon valve type.

Transcranial Doppler ultrasound has revealed the existence of cerebrovascular microemboli in asymptomatic patients with prosthetic heart valves. We investigated the relation between the presence and number of emboli signals and valve type. Patients with six types of prosthetic valves (Björk-Shiley monostrut, Medtronic-Hall, Carbomedics, ATS, Carpentier-Edwards standard, Carpentier-Edwards supraannular) were examined using transcranial Doppler ultrasound in two centers. The monitoring time was 30 min over the right middle cerebral artery. All patients were stabilized on warfarin at the time of study. Microemboli signals were identified by their characteristic audiovisual signal and on subsequent spectral analysis, based on accepted criteria. A standard neurologic questionnaire was completed by all patients. The prevalence of microemboli signals varied between 49% (Medtronic Hall) and 97% (Björk-Shiley monostrut), while their number varied between 1 [0-3] (Carpentier-Edwards standard) and 187 [136-240] (Björk-Shiley monostrut) per hour (median and 95% CI). Both parameters were significantly higher in patients with Björk-Shiley monostrut valves compared to the other patient groups. There were no significant differences in the prevalence of neurologic complications among the groups examined (overall 16%), or in emboli numbers between symptomatic and asymptomatic patients. The prevalence and quantity of microemboli signals in patients with prosthetic heart valves, as detected by transcranial Doppler, is dependent upon valve type. The clinical significance of these microemboli signals remains to be further evaluated.

Aged↗
PubMed1987

[Criteria for the optimal time of heart valve surgery].

The timing for heart surgery in mitral and aortic stenosis is still determined by the clinical situation such as NYHA-classification III and IV (or II in exceptional cases). In symptomatic patients with aortic incompetence surgery should be performed quickly. Patients with slight symptoms should only be operated if there are sings of left ventricular insufficiency at rest. There is still a discussion about patients with signs of left ventricular dysfunction on exercise; in such patients controls at short intervals are recommended. As long as left ventricular function is normal patients with aortic incompetence have a good prognosis. In patients with mitral incompetence the same criteria can be used but there are no sufficient studies on patients with normal left ventricular function which were operated. Non-invasive diagnostic techniques seem to be sufficient for the follow-up-examinations.

Aortic Valve↗
PubMed1998

[Effect of pre-existing lipids on calcinosis of swine heart valve bioprostheses. A study of a dynamic in vitro model].

Calcification is one of the main causes of failure of porcine bioprosthetic heart valves, a problem which has not been satisfactorily solved to date. Previous studies have shown that calcification is decreased in porcine heart valves that have undergone treatment for lipid extraction. The relation between lipid distribution and calcification of seven new commercially available porcine bioprosthetic heart valves (St. Jude Medical, Bioimplant) is assessed by Sudan red III staining to show preexisting lipids. All porcine bioprosthetic valves contained lipids to different degrees. Five valves were subjected to the pulsatile accelerated calcification process for 4 weeks. Distribution and level of calcification were evaluated by radiography and compared to the Sudan red-stained fatty areas. Comparison of the calcifications detected by radiography and the macroscopically detected lipids showed a coincidence of 57-66%. Two porcine bioprosthetic valves were histologically prepared and stained with Hematoxylin and von Kossa's stain, respectively. By light microscopy, the von Kossa staining revealed microcalcifications and polarizing microscopic investigation showed birefractive substances in areas with lipid deposits. These preexisting substances in porcine valve tissue may play a determinative role in the calcification of the tissue. Substantial studies are necessary to further determine the role of preexisting lipids in calcification.

Animals↗
PubMed1988

Do heart valve bioprostheses degenerate for metabolic or mechanical reasons?

Although heart valve bioprostheses provide a normal quality of life, their durability is still of great concern. Their durability failure is defined as "degeneration," which is considered to be a consequence of metabolic factors. In this study, we demonstrate that mechanical and design factors can also be responsible for bioprosthesis failure. Large numbers of porcine and pericardial bioprostheses were tested in a fatigue-testing system in which the test conditions were proved to be reproducible and accurate by a laser Doppler anemometer. The results have allowed us to define causes of failure, previously insufficiently stressed, in each type of valve tested. There is a clear difference in factors influencing tissue disruption between porcine and pericardial valves. We have compared these in vitro results with in vivo clinical findings. The main inferences are as follows: (1) Bioprostheses rupture and fail in the same fashion in both in vitro and in vivo studies. (2) Mechanical and design factors are involved in tissue failure. (3) The in vitro/in vivo durability ratio is not 1:1. This ratio depends on the test conditions. (4) Pericardial valves fail because of damage during closure, whereas porcine valves are damaged during both opening and closing (mostly opening) because of design features. (5) Once one cusp fails and prolapses, the other cusps will fail in an accelerated fashion. (6) In vitro durability of 100 X 10(6) cycles can be considered excellent and is an achievable goal. (7) Variability is the key impediment to predicting the durability of bioprostheses. Valves can fail within 2 to 3 million cycles or can last more than 100 million cycles. Similarly, bioprostheses may require explantation within a few months or can last 10 to 13 years in patients. (8) Fatigue testing is an excellent and valuable tool to elucidate the mechanical factors responsible for this variability.

Bioprosthesis↗