Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “HEART VALVES”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 415 records · Page 23Linked to original sources
PubMed1994

FDA's requirements for in-vivo performance data for prosthetic heart valves.

The Food and Drug Administration (FDA) has recently revised its "Replacement Heart Valve Guidance". That document lists the data FDA deems necessary to support the approval of new prosthetic heart valves of all designs, and which should be contained in Premarket Approval Applications for these devices. The guidance covers detailed data requirements for in vitro, animal, and clinical data. This paper is intended to briefly summarize FDA's requirements for in vivo and clinical data. The clinical study must establish that the device is both safe and effective, as compared to currently marketed replacement heart valves. It is possible to achieve this goal using hypothesis testing to compare the results of an observational study against a set of Objective Performance Criteria (OPC) which have been established by the FDA. The establishment of the OPCs was facilitated by a standardized set of definitions of complications published by the American Association of Thoracic Surgery and Society of Thoracic Surgeons (AATS/STS) in 1987/1988. Papers published in peer reviewed journals have utilized this set of definitions for data analysis, providing an ample pool of data from which to establish OPCs. The number of patients required to establish the safety and efficacy of a replacement heart valve, using this approach, is 800 valve years, 400 in the aortic and 400 in the mitral position. Advantages of this approach are reduction in the number of patients and duration of the study.

Animals↗
PubMed2005

Assessment of magnetic field (4.7 T) induced forces on prosthetic heart valves and annuloplasty rings.

PURPOSE: To assess the magnetic field interactions on 11 heart valve prostheses and 12 annuloplasty rings subjected to a 4.7 T MR system. MATERIALS AND METHODS: Ex vivo testing was performed to evaluate translational and rotational forces using previously described techniques. RESULTS: Seventeen out of 23 prostheses showed zero interaction with the magnetic field. Translational forces with deflection angles of 2-20 degrees were demonstrated in six prostheses. Only two heart valves and two annuloplasty rings demonstrated rotational forces. The Carpentier Edwards (CE) Physio Ring, which contains Elgiloy, demonstrated deflection angles three times greater than those previously measured at 1.5 T. Furthermore, there was a direct relationship between increasing prosthesis size and increasing translational force. All heart valve prostheses attracted to the magnetic field were slightly paramagnetic/weakly ferromagnetic. CONCLUSION: Twenty-three heart valve prostheses evaluated for MRI are considered safe in static fields up to 4.7 T based on current safety criteria. However, the CE Physio Ring appeared to develop an increasing magnetism upon re-entry into the MR system. We conclude that prostheses made from Elgiloy may not be acceptable for patients in an MR environment of > or =4.7 T. Further investigations are required to confirm the safety of Elgiloy.

Bioprosthesis↗
PubMed2003

Dynamics of cryoprotectant permeation in porcine heart valve leaflets.

Valve replacement is a common cardiovascular procedure for the treatment of a variety of congenital and acquired defects. Many surgical programs rely on cryopreserved heart valves from regional tissue bank programs to meet clinical demands. Current cryopreservation strategies for heart valves are empirically derived. The aim of this study was to use proton nuclear magnetic resonance spectroscopy (NMR) to monitor changes in cryoprotectant concentration in isolated heart valve leaflets. Porcine aortic valves were locally obtained, freshly isolated, and allowed to equilibrate at various experimental temperatures (22 degrees C, 10 degrees C, 4 degrees C) for 1 h prior to immersion in 1 M Me2SO solution. At defined intervals (0, 0.25, 0.5, 1, 2, 6, and 24 h) the valves were removed from the Me2SO and the leaflets were rapidly dissected and equilibrated in deuterium oxide (D2O). Using previously described techniques the Me2SO concentration in the heart valve leaflets was determined by NMR and the diffusion coefficient was calculated as a function of time and temperature. Heart valve leaflets were fully equilibrated with Me2SO after approximately 2 h of exposure at 22 degrees C while equilibrium was not reached >6 h or more at 10 degrees C and 4 degrees C. These results indicate that that permeation of Me2SO in heart valves is strongly temperature dependent Furthermore, this study provides a quantitative measure of Me2SO permeation and cryoprotectant at equilibration in heart valve leaflets. The clinical applications of these findings may help to optimize the balance between the protective and toxic effects of cryoprotectants and lead to improved methods of preservation of heart valves.

Animals↗
PubMed2002

Research on biological and mechanical heart valves: experimental studies in chronic animal models.

In the total pre-clinical evaluation of new heart valve substitutes, there is an absolute need for chronic experimental valve testing in different animal models. Also fundamental research towards mechanisms of calcification, tissue degeneration and valve thrombosis requires standardized and well-controlled animal models. Possible clinical use of a new experimental valve type and/or future developments and improvements in prosthetic heart valves, all depend on such research activities. Our recent studies concerning prosthetic heart valves resulted in following conclusions. 1. Photo-oxidation, a new tissue treatment, seems to have many possible advantages over currently existing valve fixation techniques (glutaraldehyde-fixation). The stentless porcine photo-fixed valve shows, in contrast to standard stentless valves, no aortic wall mineralization together with a good preservation of cuspal function. 2. For clinical right-sided valve implantations, the presence of a stent, together with the fixation pressure of the valve, can have its influence on the long-term behaviour of the valves in this low-pressure environment. Both stented valves, as valves fixed under pressure, seem to suffer more from fibrous tissue overgrowth 3. Mechanical stress is an important factor in the degeneration and calcification of biological valve tissue, mainly when an unfavourable stress pattern is present. Not all currently used animal models are equally reliable for valve testing and evaluation. 4. Implantation of aortic wall samples in the jugular vein of juvenile sheep is a simple, reliable and cost-effective model of aortic wall calcification. Calcification of glutaraldehyde-fixed aortic wall tissue is initiated at the level of cellular remnants, with little or no contribution from elastic fibers. Acellularization can avoid this cell-mediated calcification, but an additional treatment will be necessary to avoid the inflammation leading to elastolysis and consequent calcification of elastic fibers. 5. Mechanical valve implantation in pulmonary position delivers a reliable and reproducible test of mechanical valve thrombosis. The model allows us to compare the thrombogenic potential of different mechanical valve types, while it can also serve as a test for new therapeutic or diagnostic tools for mechanical valve thrombosis.

Animals↗
PubMed1978

[Evaluation of the antigenicity of heart valve leaflets using inbred rat strain combinations (author's transl)].

Experiments with large, non-inbred animals yield no reliable evidence in the antigenicity of heart valves. With inbred strains of rats, however, it is possible to obtain evidence on the immunological reactions of heart valve leaflet transplants. Our experiments were undertaken on the inbred rat strains (CDR, LEW, CAP and BD5, using combinations as follows: syngeneic strain combination (CDF leads to CDF), weakly allogenic (RtH-1-identical) strain cimbination (LEW leads to CDF), strongly allogeneic (RtH-1-incompatible) strain combination (CAP leads to CDF). Strain BD5 was used for the control skin grafts. Either one or two heart valve leaflets were heterotopically intra-aortally transplanted. Sensitization was verified humorally by transplantation antibody titers and cellularly by subsequent donorspecific skin transplants. The following results were achieved: Allogeneic heart valve leaflets are antigenic. Intravascular grafting of one heart valve leaflet induces the same degree of sensitization as the grafting of two leaflets. In the RtH-1-identical system, sensitization is revealed only by subsequent skin grafting, whereas in the RtH-1-incompatible system, sensitization is humorally demonstrated as well. This indicates that in heart valve leaflet transplantation cellmediated reactivity is a more sensitive indicator than the humoral one. The greater the immunological difference is, the clearer the sensitization will be. In the strongly allogeneic system, the sensitization is even demonstrated humorally; skin grafts are rejected as "white grafts". Improved long-term results may be expected in allogeneic vital heart valve transplants if consideration is given to the HLA compatibility between donor and recipient; the appearance of delayed insufficiency could be greatly lessened or even deferred.

Animals↗
PubMed2000

Development and evaluation of a swine model to assess the preclinical safety of mechanical heart valves.

BACKGROUND AND AIM OF THE STUDY: The current standard of in vitro and in vivo preclinical heart valve testing has recently been questioned because of its failure to reveal the thrombogenic potential of the Medtronic Parallel prosthetic valve. The aim of this study was to develop a swine model for the in vivo preclinical evaluation of mechanical heart valves, and to assess the ability of this model to identify mechanical heart valve design features that result in valve-related thrombosis. METHODS: Twenty-two swine underwent mitral valve replacement (MVR) using three different bileaflet mechanical valve designs (St Jude Medical, CarboMedics, Medtronic Parallel). Each animal was placed in an anticoagulation protocol (group I, INR 3.0-3.5; group II, INR 2.0-2.5; group III, no anticoagulation) and followed for up to 20 weeks. Terminal studies were performed on all animals surviving for more than 30 days. RESULTS: Twenty-one animals survived the immediate postoperative period. Four of six group I animals died from hemorrhagic (large wound hematoma; hemopericardium) complications early in the study. In the two long-term (61 and 89 days) survivors, INRs of 3.0 to 3.5 were never achieved (61-day survivor, mean INR 2.0 +/- 1.03; range: 0.8-5.4; 89-day survivor, mean INR 1.92 +/- 1.34; range: 1.0-7.9). Pathological analysis of explants from group I survivors revealed minimally obstructive fibrous sheathing on the inflow orifice without restriction of bileaflet motion (61 and 89 days), and two large perivalvular defects (61 days). Six of seven group II animals died from early hemorrhagic complications (hemopericardium) (mean INR 2.32 +/- 1.84; range: 0.8-8.2). Vegetations resulting in obstruction of both sides of the valve orifice and restriction of bileaflet motion were observed in a group II survivor (mean INR 2.33 +/- 1.58; range: 0.9-7.0). Group III animals (n = 8) survived for a mean of 106 +/- 60 days (range: 1-177 days). In group III, fibrous sheathing was present on all explanted valves and organized thrombi in six valves; orifice obstruction (seven valves) and restriction of bileaflet motion (three valves) were also observed. CONCLUSION: The use of MVR in swine as a preclinical model to evaluate the safety and performance of mechanical heart valves is limited by: (i) difficulty in maintaining safe levels of anticoagulation with warfarin, resulting in a high incidence of hemorrhagic complications; (ii) marked fibrous sheath formation and associated thrombosis; and (iii) an increased incidence of perivalvular defects, believed to result from normal somatic growth occurring in young swine.

Animals↗
PubMed1996

Pitfalls and outcomes from accelerated wear testing of mechanical heart valves.

In 1990 Sorin Biomedica introduced a new bileaflet heart valve called the Bicarbon valve. This design was reported to eliminate wear in the hinge mechanism. Clinical quality Sorin Bicarbon, CarboMedics, St. Jude Medical, Duromedics and Jyros valves were obtained to test this claim and to compare the wear in the pivot of this new valve to other available heart valves. The valves were visually inspected then subjected to 4,000 cycles at a physiological beat rate in vitro. The valves were re-inspected then subjected to 400 million cycles in a Reul type accelerated wear tester. Scanning electron microscope photographs were taken of all contact areas at 40, 80, 120, 160, 200, 240, 280 and 400 million cycles. Wear marks on the inflow side of the Sorin, CarboMedics and St. Jude leaflets were measured and compared. Orifice wear was not quantified because of difficulty with measuring inside complex depressions. After 4,000 cycles of testing at a physiological beat rate the CarboFilmTM coating on the Sorin orifice showed signs of erosion. The other valve components only exhibited minor burnishing after 4,000 cycles. Following completion of 400 million cycles in an accelerated wear tester, approximately ten years in vivo, all valves showed significant wear. The inflow face of the pivot on the Sorin Bicarbon leaflets exhibited the deepest wear marks. The CarboFilm coating on the Sorin Bicarbon orifices was removed from most areas of leaflet contact. The transition between the remaining coating and the eroded areas created a rough edge. The tips of the Sorin leaflets contacted the bottom of the orifice pivot, in contrast to the St. Jude Medical and CarboMedics designs, which had minimal contact between the leaflet and the orifice.

Biocompatible Materials↗
PubMed2003

Role of inflammation in allogeneic and xenogeneic heart valve degeneration: immunohistochemical evaluation of inflammatory endothelial cell activation.

BACKGROUND AND AIM OF THE STUDY: Biological heart valve prostheses undergo degenerative changes which lead ultimately to dysfunction or even complete destruction. The study aim was to evaluate immunological factors and their potential role in biological heart valve destruction. METHODS: Allogeneic (n = 10) and xenogeneic (n = 3) aortic valve prostheses, as well as aortic valves retrieved from transplanted human hearts which had to be replaced due to chronic graft rejection (n = 4), were analyzed. Aortic valves from human donor hearts (n = 4) served as controls. Evaluated adhesion molecule expression included: selectin family ELAM-1, CD62; integrin family VLA-1, -2, -3, -4, -5 and -6; immuoglobulin supergene family PECAM-1, ICAM-1 and -2, and class I heavy chain proteins; complementary adhesion molecules CD34, CD44 and von Willebrand factor. RESULTS: ELAM-1, ICAM-1 and -2, CD34, CD44 and class I heavy chain proteins, which play significant roles during inflammatory processes, showed stronger expression patterns in allogeneic and xenogeneic aortic heart valve prostheses compared to native or chronically rejected valves. Furthermore, allogeneic and xenogeneic valves showed a strong thrombogenicity which stained positive for von Willebrand factor outside endothelial cells on these valves. Integrin molecules as well as CD62 showed only mild differences. CONCLUSION: Immunological reactions play a pivotal role in the degeneration of biological heart valve prostheses. As immunosuppressive therapy after heart valve replacement is not a viable option, novel approaches in 'tissue engineering' may help to avoid tissue degeneration while preserving the advantage of biological tissue origin.

Adult↗
PubMed2003

Degeneration of bioprosthetic heart valve cusp and wall tissues is initiated during tissue preparation: an ultrastructural study.

BACKGROUND AND AIM OF THE STUDY: Chronic tissue degeneration is a major factor in the failure of porcine bioprosthetic heart valves. Stabilization with glutaraldehyde (GA) has become the standard in preparation of bioprosthetic heart valves, but there is increasing evidence that GA does not effectively stabilize all tissue structures, specifically glycosaminoglycans (GAGs). The study aim was to establish the status of GAGs in bioprosthetic heart valves and to ascertain whether degeneration of the extracellular matrix (ECM) is initiated during preparation of porcine tissues for use as bioprosthetic heart valves. METHODS: Stentless porcine bioprosthetic heart valves were prepared by tissue harvesting, 24 h of storage in cold saline, and 14 days' fixation in buffered 0.6% GA. Tissue samples obtained from fresh and fixed aortic cusps and wall conduit were analyzed for ECM integrity and GAG localization by transmission electron microscopy combined with toluidine blue staining. RESULTS: Major degenerative changes occurred in the ECM ultrastructure of both porcine cusp and wall during tissue preparation for use as bioprosthetic heart valves. Modifications in the aortic cusp included loss of GAGs from the interfibrillary space and from the surface of the collagen fibers. In the aortic wall, GAGs were lost from the interfibrillary space and from the surface of collagen fibers. In addition, the surface of wall elastic fibers exhibited marked paucity of GAGs and elastin-associated microfibrils. CONCLUSION: The typical steps involved in the preparation of porcine aortic bioprosthetic heart valves induce, or cannot fully prevent, degeneration of some components of the ECM. Controlling the extent of this pre-implantation deterioration will open new gateways for improvement of the quality and durability of future cardiovascular bioprostheses.

Animals↗
PubMed1984

Amyloid deposits in aortic and mitral valves. A clinicopathological investigation of material from 100 consecutive heart valve operations.

The material from 100 consecutive aortic and mitral valve operations has been studied histologically with particular reference to the presence of amyloid deposits. Sixty seven per cent were positive (aortic 88%, mitral 45%). The simultaneous occurrence of calcification of the valves and amyloid degeneration as well as of calcification and hyalinization was significant. Similarly there was significantly more amyloid in the older age groups, as well as a significant correlation between the degree of hyalinization of the valve and amyloid. Thirty-two patients had previously suffered from rheumatic fever. The heart valves of these patients did not differ histologically from the others, whereas significantly more amyloid was observed in the stenotic mitral valves than in the mitral valves which were insufficient.

Adolescent↗
PubMedDate not supplied

A bovine model for detecting high intensity transient signals originating from mechanical heart valves.

In patients with mechanical heart valves (MHVs), transcranial Doppler methods commonly detect high intensity transient signals (HITS) representing microemboli. These microemboli, which are presumably gaseous, may cause stroke and cognitive deterioration. A bovine model was therefore developed for studying the relationship between mitral MHV induced HITS and potential etiogenic factors. We placed an 18 mm, 4 MHz Doppler probe in the brachiocephalic artery to detect MHV induced microbubbles at baseline (rest) and under 9 other conditions. To elucidate the gas composition (CO2 or N2) of the microbubbles, we administered 1%, 3%, and 5% CO2, and 100% O2. To determine effect of the heart rate, we paced the heart at 120, 160, and 180 bpm. To alter the myocardial contractility, we gave dobutamine and esmolol. Two independent, blinded observers counted the HITS from recorded doppler spectra. HITS were defined by an initial unidirectional spectral deviation, a signal power of >8 dB relative to the background power, and lack of a cyclic appearance. The electrocardiogram, aortic and LV pressures, and LV dP/dt were obtained telemetrically. The calves were studied 4 to 6, 8 to 10, and 12 to 14 weeks postoperatively, after which the animals were sacrificed at an approximate 4 month study duration, and a postmortem evaluation of the heart and the main viscera was performed. In all, 27 HITS recordings were made in 10 calves. Myocardial contractility was the only factor to significantly affect HITS frequency; the heart rate and blood gas concentrations had minimal effect on HITS frequency. Our bovine model will be useful for assessing valve designs, as well as the mechanism of HITS, the composition of the microemboli, and their possible pathophysiologic effects on the kidneys and brain.

Adrenal Glands↗
PubMed1995

Laser profiling: a technique for the study of prosthetic heart valve leaflet motion.

A detailed understanding of the stresses and strains developed in functioning flexible-leaflet valves is necessary if a durable, non-thrombogenic heart valve replacement is to be realized. A new experimental tool, laser profiling, is presented for the study of flexible-leaflet heart valve dynamics. Profiles of moving leaflet surfaces are obtained by projecting parallel sheets of laser light onto valve leaflets as the valves open and close in a mock circulatory loop. Two versions of laser profiling have been developed. In two-dimensional mode multiple profiles are generated on a fixed plane in space but at discrete intervals in time, whereas in three-dimensional mode multiple profiles are generated across the leaflet surface at (effectively) a single instant in time. Highlighted leaflet profiles are captured by camera and transferred to an image processing system for analysis. A simple algorithm permits digitized profiles to be reconstructed within a computer-aided design software package, providing detailed visualization and quantification of valve motion. Extensive validation studies have been performed using the Medtronic-Hall mechanical prosthetic heart valve. Laser profiling enables computer reconstruction of the rigid occluder to an accuracy of +/- 200 microns from a 0.7 ms exposure taken during the period at which the occluder moves with greatest velocity. The technique has been applied to investigate the leaflet dynamics of a bovine pericardial heart valve prosthesis.

Acoustic Stimulation↗
PubMed1995

Ventricular flow dynamic past bileaflet prosthetic heart valves.

To characterise hydrodynamic properties of prosthetic heart valves in mitral position, ultrasonic velocity measurements were performed using a cardiovascular simulator. A Duromedics and a Saint-Jude Medical bileaflet heart valve were tested. The Saint-Jude valve was oriented first in an anatomical position, i.e. the tilt axis parallel to the septal wall, and then in an anti-anatomical position. In the anti-anatomical position, from mid diastole to mid systole, two contrarotative vortices are generated in the ventricle by the interaction between the flow directed by the leaflets downstream from the lateral orifices and the ventricular wall motions. In the anatomical position, the mitral flow penetrates the ventricle principally through the lateral orifice proximal to the septal wall, due to the vortex in the atrial chamber. The mitral inflow then circulates along the septal wall to the apex, and produces a large ventricular vortex during systole. In the anatomical position, the Saint-Jude thus provides a better ventricular washout during this phase. The mitral inflow through the Duromedics in the anti-anatomical position produces two contrarotative vortices in the ventricle, but in the opposite sense than downstream the Saint-Jude valve; the flows that penetrate through the lateral orifices are directed to the ventricular walls and then recirculate to the centre of the ventricle, providing a very fluctuating flow near the apex. Thus, a slight difference in valve design produces a significant difference in the ventricular flow fields.

Blood Flow Velocity↗
PubMed2006

Low-molecular-weight heparin for thromboprophylaxis in pregnant women with mechanical heart valves.

BACKGROUND: Pregnancy in a woman with a mechanical heart valve is a life-threatening situation. Due to the inability of unfractionated heparin to prevent valvular thromboses, warfarin or other vitamin K antagonists have been the preferred anticoagulants for the mother. They are, however, potentially harmful to the fetus. With the advent of low-molecular-weight heparins, clinicians were hopeful for an alternative that was safe for the fetus, but more effective than unfractionated heparin, which carries a 29-33% risk of life-threatening thromboses and a 7-15% chance of mortality. Unfortunately, fatal thromboses have occurred with low-molecular-weight heparin as well. METHODS: We searched the MEDLINE database and other sources to identify cases of the use of low-molecular-weight heparin for thromboprophylaxis in women with mechanical heart valves. RESULTS: We found 73 cases and added three of our own for a total of 76. There were 17 thrombotic events (22%). Thirteen were valve thromboses, two were strokes, and two were myocardial infarctions. There were three deaths (4%). CONCLUSIONS: While pregnant women with mechanical heart valves who receive low-molecular-weight heparin for thromboprophylaxis are at extremely high risk of life-threatening thromboses, there is no evidence that low-molecular-weight heparin is inferior to unfractionated heparin.

Anticoagulants↗
PubMed1999

Viability and enzymatic activity of cryopreserved porcine heart valve.

Fibroblast viability of a natural tissue valve for replacing a defective heart valve through allograft or xenograft has been suggested to affect its clinical durability. In this study, the cell viability and enzymatic activity of porcine heart valve leaflets were examined in regard to concerning to the preservation process [variable warm ischemic time (WIT), cold ischemic time (CIT), and cryopreservation]. Porcine heart enblocs were obtained and valve dissection was performed after 2, 12, 24, or 36 hours, in respective groups A, B, C, and D, as WIT. Each group was stored for 24 hours as CIT and cryopreserved. Leaflets were dissected from a valved conduit after each process, and cell viability and enzymatic activity in the leaflet were investigated using trypan blue staining and API ZYM kits. WIT extension significantly decreased fibroblast viability (p < 0.05, 92.25 +/- 2.7% at 2 hours, 84.9 +/- 6.7% at 12 hours, 57.0 +/- 10.2% at 24 hours, 55.9 +/- 7.9% at 36 hours), while CIT for 24 hours was also influenced significantly (p < 0.05), whereas cryopreservation demonstrated no effect on cellular viability. In enzyme activity observation, several enzymes related to lipid or nucleotide degradation (esterase, esterase lipase, particularly phosphatase, phosphohydrolase) were remarkably changed following the valve-fabrication process. After 24 hours CIT, these enzymatic activities in groups B, C and D significantly increased, but the activities decreased after cryopreservation. Particularly, both the viability and enzymatic activity showed remarkable changes after CIT in group B (WIT = 12 hours). These results suggest that WIT is more important than CIT in maintaining viability of the valve, and that completing all the cryopreservation process within 12 hours after acquisition is recommended.

Animals↗
PubMed1984

Immunological reactivity to a new glutaraldehyde tanned bovine pericardial heart valve.

The presence of pericardial specific antibodies directed against prosthetic bovine tissue heart valves was quantified by use of an indirect immunofluorescence technique. Serum samples containing antibodies displayed bright fluorescence when tagged with a secondary layer conjugated to FITC. Specific antibody production was undetectable in dogs or sheep who had undergone heart valve replacement (mitral or tricuspid) with a new unicusp prosthesis (Meadox Medicals Inc., NJ), as long as 17 mos following implantation. Similarly, anti-pericardial IgG was not detected in the serum of patients grafted with an analogous commercially available tissue heart valve, although in one patient the presence of low affinity IgM was suggested. This study documents the low immunological reactivity of this new tissue heart valve. Clinically valvular dysfunction due to an immunological response is not expected.

Animals↗
PubMed1999

Assessment of perceived mechanical heart valve sound level in patients.

BACKGROUND AND AIM OF THE STUDY: When mechanical heart valves close, they generate an impulse that is transmitted to the patient's inner ear by two routes: (i) As acoustically transmitted sound waves; and (ii) as vibrations transmitted through bones and vessels. The aim of this study was to quantitate what patients perceive as sound from their mechanical heart valve prostheses - including both air-transmitted sound waves and bone-transmitted vibrations. METHODS: Thirty-four patients with implanted mechanical bileaflet aortic and mitral valves (St. Jude Medical and On-X) were included in the study. Measurements were performed in a specially designed sound-insulated chamber equipped with microphones, accelerometers, preamplifiers and a loud-speaker. The closing sounds measured by an accelerometer on the patient's chest were delayed 400 ms, amplified and played back to the patient through the loudspeaker. The patient adjusted the feedback sound to the same level as the 'real-time' clicks they perceived directly from their valve. In this way the feedback sound energy includes both the air- and bone-transmitted energies. Sound pressure levels (SPL) were quantitated in both dB(A) and in loudness units (sones) according to ISO 532B (Zwicker method). RESULTS: The mean air-transmitted SPL measured close to the patient's ear was 23 +/- 4 dB(A). The total air-and bone-transmitted sounds and vibrations were perceived by the patients as a SPL of 34 +/- 5 dB(A). There was no statistically significant difference in perceived sound from the two bileaflet valves investigated, and no difference between aortic and mitral valves. CONCLUSIONS: The study showed that the presented feedback method is capable of quantitating the perceived sounds and vibrations from mechanical heart valves, if the patient's hearing is not too impaired. Patients with implanted mechanical heart valve prostheses seem to perceive the sound from their valve two to four times higher than nearby persons, because of the additional bone-transmitted vibrations.

Adaptation, Psychological↗