An analysis of autopsy findings in 108 patients who died after valve replacement

The pathological findings and the causes of death were reviewed in 108 patients who had received 142 heart valve prostheses (52 mechanical and 90 bioprostheses) at the National Cardiovascular Center in Osaka, Japan, from 1977 to 1991. Rheumatic heart disease was the major underlying disease (60.2%), and the age distribution at death ranged from 21 to 80-year-old. Survival duration after the surgery extended from 0 day to 9 years. Thirty-three patients (30.6%) died of perioperative complications such as myocardial haemorrhage and damage, or from heart failure which had been evident prior to the operation, a cause of death which predominated in patients who died within 1 week of surgery (15/17; 88.2%). Thirty-eight patients (35.2%) died of prostheses-related problems such as prosthetic valve failure (cuspal tears and calcifying destruction of the xenograft), thromboembolism, and prosthetic valve endocarditis. Endocarditis was frequent in patients who had survived longer than 1 year (25/33; 75.8%). None of the patients died of prostheses-related problems within 1 week. Non-infectious valve failure was more common in patients with bioprostheses than in those with mechanical valves; thromboembolism showed the opposite association. Prosthetic valve infective endocarditis was nearly equal in frequency in both types of valve.     

猪主动脉生物瓣远期损坏的病理学观察

对３６ 例植入人体内１０７ 个月以上的损坏瓣膜作病理学观察。基本病损：９４－４４ ％ 为钙化、３６－１１％ 为撕裂、１３－２９％ 为穿孔。结果表明,首先瓣叶应力集中区胶原纤维变性产生钙化,新的应用集中区的形成,导致瓣叶撕裂与穿孔,相互促进。早期损坏以钙化为主,而后期常以钙化和撕裂、钙化和穿孔等多种病损因素的复合结果为主。     

Novel "biomechanical" polymeric valve prostheses with special design for aortic and mitral position: a future option for pediatric patients?

In children, systemic heart valve replacement with bioprostheses is associated with accelerated valve degeneration, and mechanical prostheses require permanent anticoagulation. Novel "biomechanical" polymeric valve prostheses ("bio" = flexible, "mechanical" = synthetic), solely made of polycarbonate urethane (PCU), were tested in vitro and in a growing animal (calf) model with the aim of improved durability without permanent anticoagulation. The trileaflet aortic prosthesis has diminished pressure loss and reduced stress and strain peaks. The asymmetric bileaflet mitral valve mimics natural nonaxial inflow. The valves underwent long-term in vitro testing and in vivo testing in growing calves for 20 weeks [mitral (7), aortic (7)] with comparison to different commercial bioprostheses [mitral (7), aortic (2)]. In vitro durability of PCU valves was proved up to 20 years. Survival of PCU valves versus bioprostheses was 7 versus 2 mitral and 5 versus 0 aortic valves, respectively. Two animals with PCU aortic valves died of pannus overgrowth causing left ventricular outflow tract obstruction. Degeneration and calcification were mild (mitral) and moderate (aortic) in PCU valves but were severe in biological valves. There was no increased thrombogenicity of the PCU valves compared to bioprostheses. The novel polymeric valve prostheses revealed superior durability compared to current bioprostheses in growing animal model without permanent anticoagulation and thus, may be a future option for pediatric patients.     

Transient, three-dimensional flow field simulation through a mechanical, trileaflet heart valve prosthesis

Thromboembolic complications are one of the major challenges faced by designers and researchers in development of artificial organs with blood-contacting devices such as heart valve prostheses, especially mechanical valves. Besides increasing the thrombogenic potential, these valves change the hydrodynamic performance of the heart. In this study, the flow through a trileaflet, mechanical heart valve prosthesis was modeled with transient computational fluid dynamics to analyze flow patterns causing thrombus formations on valves. The valve was simulated under conditions of a test rig (THIA II), which was specially designed to analyze different valves with respect to thrombosis. The main goal of this study was to mimic the exact conditions of the test rig to be able to compare numerical and experimental results. The boundary conditions were obtained from experimental data as leaflet kinematics and pressure profiles. One complete cycle of the valve was simulated. Numerical flow and pressure results were analyzed and compared with experimental results. Shear stress and shear rates were determined with respect to thrombogenic potential, especially in the pivot regions, which seem to be the main influence for activation and deposition of thrombocytes. Approximately 0.7% of the blood volume moving through the fluid domain of the valve was exposed to shear rates high enough to cause platelet activation. However, shear rates of up to 20,000 s?1 occurred in pivot regions. The pressure differences between the simulation and experimental data were approximately 2.5% during systole and increased up to 25% during diastole. The presented method, however, can be used to gain more information about the flow through different heart valve prostheses and, thus, improve the development process.     

Origin and appearance of HITS induced by prosthetic heart valves: an in vitro study

Patients with mechanical heart valve prostheses show significantly enhanced numbers of HITS detected by transcranial Doppler ultrasound. In order to assess the origin of HITS formation, an in vitro study was set out to quantify valve induced microemboli for mechanical and bioprosthetic valves under various circulatory conditions by means of Ultrasound-Doppler-Sonography. At the same time the influence of CO2 partial pressure on HITS rate vas investigated. It can be summarised that for mechanical heart valve prostheses a strong correlation exists between left ventricular dp/dtmax and the detected HITS rates. It was also demonstrated that a bioprosthesis generates significantly less HITS than a mechanical valve. The origin of HITS is gaseous since the tests were carried out using a cell-free filtered water-glycerol test fluid. The HITS rate could be increased by increasing the amount of dissolved gas within the test fluid. The results support the hypothesis that cavitation is the key factor in the appearance of gaseous microemboli at heart valve prostheses.     

Cavitation potential of mechanical heart valve prostheses

Just like technical check valves, the function of mechanical heart valve prostheses may presumably also lead to cavitation effects during valve closure. Due to the waterhammer effect, cavitation may primarily occur in the mitral position leading to high mechanical loading of the valve itself and of corpuscular blood elements. Ten different types of commercial mechanical heart valves were investigated in the mitral position of a pulsatile mock loop, to detect cavitation thresholds under physiologically similar conditions by cinematographic techniques. Almost all these valve prostheses show cavitation up to a ventricular pressure gradient of 5000 mmHg/s. The threshold depends on valve type and size and is sometimes within the physiological range below 2000 mmHg/s. Visible cavitation bubbles with a diameter of up to 1.8 mm and a collapse time of less than 0.1 ms suggest that vapour cavitation may play an important role for material and blood damage in mechanical heart valve prostheses.     

Clinical Outcomes of Transcatheter Aortic Valve Implantation for Native Aortic Valves in Patients with Low Coronary Heights

PurposeAcute coronary occlusion is a rare but fatal complication that may occur during trans-catheter aortic valve implantation (TAVI) and appears more frequently in patients with low coronary heights. We evaluated the feasibility of self-expanding valves in patients with low coronary heights undergoing TAVI.Materials and MethodsTAVI for native aortic valve stenosis was conducted in 276 consecutive patients between 2015 and 2019 at our institute. Using multi-detector computed tomography (MDCT), information on the aortic valve, coronary arteries, and vascular anatomy in 269 patients was analyzed. Patients with low coronary heights were defined as those with coronary heights of 10 mm or less during MDCT analysis.ResultsAmong the 269 patients, 29 (10.8%) patients had coronary arteries with low heights. The mean coronary height was 8.9±1.2 mm in the left coronary artery. These patients with low coronary heights were treated with self-expandable (n=28) or balloon-expandable (n=1) valves. Prophylactic coronary protection with a guidewire, balloon, or stent prepositioned down at-risk coronary arteries was not pursued in all patients. No acute coronary occlusion occurred in any of these patients during TAVI. Five patients (17.9%) died during follow-up (average of 553.8 days), including four from non-cardiogenic causes and one from a cardiogenic (aggravation of heart failure) cause.ConclusionA considerable number of patients with low coronary heights were observed among TAVI candidates in this study. Use of a self-expandable valve may be feasible for successful TAVI without acute coronary occlusion in patients with low coronary heights.     

Anatomic analysis of removed prosthetic heart valves: causes of failure of 33 mechanical valves and 58 bioprostheses, 1980 to 1983

The details of heart valve prosthesis-associated problems are not widely known. This study investigated the etiologies of the failures of 91 valves, 33 mechanical prostheses and 58 bioprostheses, obtained at reoperation (83) or autopsy (eight) at the Brigham and Women's Hospital during the 42-month period from mid- 1980 through 1983, one to 264 months (mean, 72 months) after valve replacement. Analysis was by gross, histologic, radiographic, and microbiologic examination, as well as review of clinical records. Overall causes of failure included paravalvular leak (15 per cent), thrombosis (7 per cent), tissue overgrowth (8 per cent), degeneration or mechanical failure (43 per cent), and endocarditis (19 per cent). Endocarditis and paravalvular leak were equally frequent with mechanical prostheses and bioprostheses. In addition, thrombosis (18 per cent), tissue overgrowth (21 per cent), and structural failure (12 per cent) were all important failure modes for mechanical prostheses. Sterile degeneration was the overwhelming cause of failure for bioprostheses, accounting for the failure of 35 of 58 (60 per cent) of those recovered. Sterile degeneration took several forms: calcification, with or without cuspal tears (27 cases, 47 per cent of bioprostheses; mean, 77 months, range, 44 to 108 months) and cuspal defects without calcification (eight cases, 14 per cent; mean, 59 months, range, eight to 122 months). In general, calcification increased with time after implantation, but the propensity for the mineralization of bioprostheses varied widely among patients. Four torn valves that had been in place for more than six years had radiographically undetectable calcific deposits. The results of this study indicate that paravalvular leak and endocarditis are frequent causes of failure for all valve types. No clear failure mode predominates with mechanical valve prostheses, although some designs have specific inherent limitations. In contrast, degeneration, especially that related to mineralization, is the most important cause of the late failure of contemporary bioprostheses.     

The CarboMedics prosthetic heart valve: experience with 180 implants

At Jichi Medical School Hospital, three types of mechanical prosthetic valves (CarboMedics, Omnicarbon, Bicarbon) were used without randomization from 1991 to 2000. A retrospective study of valve replacements done between June 1991 and November 2000 utilizing 180 CarboMedics valves in 145 patients who had not previously undergone prosthetic valve replacement or aortic root and/or arch replacement was conducted to evaluate midterm patient outcomes to assess the future continuous use of CarboMedics valves. Women made up 47.6% of the patients and the mean age was 57.5 years (range 12–80 years). Preoperative New York Heart Association functional class was III or IV in 92.4% (134/145) of patients. Mean follow-up of 4.5 years (range 0–10.0 years) was 95.9% complete, with a total of 628 patient-years (PY). Early (within 30 postoperative days) mortality was 5.5% (8 of 145): 3 from hemorrhage, 3 from nonvalve-related heart failure, 1 from infection, and 1 from arrhythmia. There were 16 late deaths (2.54%/PY): 1 from hemorrhage, 4 from unknown causes/sudden death, 4 from nonvalve-related heart failure, and 7 from other noncardiac causes. A total of 121 patients (83.0%) were alive at the last follow-up, done in November 2000. The linearized death rate was 3.82%/year (including 1.11%/year for valve-related deaths). Linearized death rates from various causes were: bleeding, 0.96%/year; thromboembolism, 1.11%/year; thrombosis, 0.39%/year; perivalvular leak, 0.96%/year; endocarditis, 0%/year; hemolysis, 0%/year; and reoperation, 0.63%/year. No structural valve failure was observed. Comparative early mortality rates of valve replacement without aortic root replacement or arch replacement, excluding repeat valve replacement operations, in our institute, were 3.5% (12/307) for all valve types used contemporaneously, 2.6% (2/76) for Omnicarbon valves, and 2.3% (2/86) for Bicarbon valves. Although the CarboMedics valve had a rather high mortality rate of 5.5% (8/145) compared with the total early mortality rate of 3.5%, the low incidence of valve-related complications might support the continued use of the CarboMedics valve for valve replacement.     

Fulminant diffuse systemic sclerosis following aortic valve replacement

We present a case of fulminant diffuse systemic sclerosis (dSSc) developed after the aortic valve replacement followed by fatal congestive heart failure within the 6 months from the initial symptoms. A 61-year-old male developed rapidly progressive diffuse systemic sclerosis following aortic valve replacement due to stenosis of bicuspid aortic valve. He presented with diarrhoea, weight loss, mialgia and arthralgia after cardiac surgery. Heart failure, due to myocardial fibrosis, was noted as a cause of death. We hypothesize that artificial materials like the ones used in mechanical valves or silicon materials in breast implants may induce fulminant course of pre-existing systemic sclerosis or create a new onset in predisposed individual.     

Mechanical heart valve prostheses:: identification and evaluation (erratum)

Mechanical heart value prostheses have been in use since the 1950s. Many prostheses have been used for a while and then discontinued. Today, there are a large number and variety of prostheses in use and an even larger variety that are in place in patients. These may be explanted at any time for a number of reasons. It is essential for the practicing pathologist to be able to identify the prosthesis and be aware of some of its reported complications and modes of failure. This article, and a second one on bioprosthetic heart valves, is designed as a ready reference guide to heart valve prostheses, their important identifying features, their common complications, and modes of failure. It should help in the accurate identification of explanted prosthetic valves and more definitive reports. This accuracy of identification as well as tracking of abnormalities noted will, we hope, permit the identification of new failure modes and the recording of causes of failure of new (or even modified) prosthetic heart valves.     

Prosthetic heart valves: catering for the few

Prosthetic heart valves epitomize both the triumphant advance of cardiac surgery in its early days and its stagnation into a retrospective, exclusive first world discipline of late. Fifty-two years after the first diseased heart valve was replaced in a patient, prostheses largely represent the concepts of the 1960s with many of their design-inherent complications. While the sophisticated medical systems of the developed world may be able to cope with sub-optimal replacements, these valves are poorly suited to the developing world (where the overwhelming majority of potential valve recipients reside), due to differences in age profiles and socio-economic circumstances. Therefore, it is the latter group which suffered most from the sluggish pace of developments. While it previously took less than 7 years for mechanical heart valves to develop from the first commercially available ball-in-cage valve to the tilting pyrolytic-carbon disc valve, and another 10 years to arrive at the all-carbon bi-leaflet design, only small incremental improvements have been achieved since 1977. Similarly, bioprosthetic valves saw their last major break-through development in the late 1960s when formalin fixation was replaced by glutaraldehyde cross linking. Since then, poorly understood so-called 'anti-calcification' treatments were added and the homograft concept rediscovered under the catch-phrase 'stentless'. Still, tissue valves continue to degenerate fast in younger patients, making them unsuitable for developing countries. Yet, catheter-delivered prostheses almost exclusively use bioprosthetic tissue, thereby reducing one of the most promising developments for patients of the developing world into a fringe product for the few first world recipients. With tissue-engineered valves aiming at the narrow niche of congenital malformations and synthetic flexible leaflet valves being in their fifth decade of low-key development, heart valve prostheses seem to be destined to remain an unsatisfying and exclusive first world solution for a long time to come.     

Pathomorphosis of Erythrocytes in Patients with Acquired Valvular Heart Diseases and under Conditions of Their Correction

Scanning electron microscopic study of the morphology and surface architectonics of erythrocytes in patients with acquired aortic and mitral valve diseases showed signs of morphological restructuring of the erythrocyte population. Reversibly transformed transitional red blood cells and irreversibly changed prehemolytical and degenerative erythrocytes were much more incident in these patients than in donors. The number of functionally intact biconcave discocytes notably decreased in comparison with donors. Morphological heterogeneity of the erythrocyte pool increased during the immediate period after replacement of heart valves with mechanical disc prostheses. Disorganization of the surface relief of red blood cells persisted 12-24 months after surgery.     

Artificial valves “up to date” in Japan

We have many choices when selecting artificial valves for valve replacement surgery. It is necessary to know the characteristics of the various prosthetic valves to make an appropriate decision for each valvular heart disease patient. In this review paper, we describe the features and benefits of the artificial valves available in Japan. Standard and new generation bioprostheses and mechanical prostheses are reviewed. The new technology of the catheter-delivery heart valve is also mentioned in this paper.     

Development of artificial neural network-based algorithms for the classification of bileaflet mechanical heart valve sounds

Objectives: As is true for all mechanical prostheses, bileaflet heart valves are prone to thrombus formation; reduced hemodynamic performance and embolic events can occur as a result. Prosthetic valve thrombosis affects the power spectra calculated from the phonocardiographic signals corresponding to prosthetic closing events. Artificial neural network-based classifiers are proposed for automatically and noninvasively assessing valve functionality and detecting thrombotic formations. Further studies will be directed toward an enlarging data set, extending the investigated frequency range, and applying the presented approach to other bileaflet mechanical valves. Methods: Data were acquired for the normofunctioning St. Jude Regent valve mounted in the aortic position of a Sheffield Pulse Duplicator. Different pulsatile flow conditions were reproduced, changing heart rate and stroke volume. The case of a thrombus completely blocking 1 leaflet was also investigated. Power spectra were calculated from the phonocardiographic signals and used to train artificial neural networks of different topologies; neural networks were then tested with the spectra acquired in vivo from 33 patients, all recipients of the St. Jude Regent valve in the aortic position. Results: The proposed classifier showed 100% correct classification in vitro and 97% when applied to in vivo data: 31 spectra were assigned to the right class, 1 received a false positive classification, and 1 was "not classifiable." Conclusion: Early malfunction detection is necessary to prevent thrombotic events in bileaflet mechanical heart valves. Following further clinical validation with an extended patient database, artificial neural network-based classifiers could be embedded in a portable device able to detect valvular thrombosis at early stages of formation: this would help clinicians make valvular dysfunction diagnoses before the appearance of critical symptoms.     

Autopsy-determined causes of death following cardiac transplantation. A study of 81 patients and literature review.

The principal and contributory causes of death in 81 autopsied heart transplant patients who died at Groote Schuur Hospital, Cape Town, South Africa, were investigated and subdivided according to the immunosuppressive regimen used as well as the postoperative survival period. Mean graft survival was 488 days. Chronic rejection (30%), infection (23%), and acute rejection (20%) were the most common principal causes of death. Both fatal and nonfatal infections involved the lung predominantly. A review of the literature revealed 198 other autopsied heart transplant patients whose principal cause of death could be analyzed; infection accounted for almost half of these latter deaths, followed by acute and chronic rejection. Contributory causes of death in the 81 patients were as follows: infection (17%), acute rejection (16%), chronic rejection (14%), miscellaneous conditions (14%), embolism (14%), pancreatitis (11%), peptic ulcer (9%), inadequate donor heart (3%), and malignancy (1%). We conclude that infection, together with acute and/or chronic rejection, are still the major causes of death in heart transplant patients.     

Fatal pulmonary embolism in hospitalised medical patients.

This study aimed to determine the frequency of fatal pulmonary emboli in hospitalised medical patients by a retrospective necropsy review and prospective non-interventional patient follow up study. The main outcome measure, necropsy proven fatal pulmonary embolism, was determined from 400 consecutive necropsy records and 200 consecutive medical inpatient episodes. Fatal pulmonary embolism was recorded in 29 of 400 necropsies; 17 were medical patients. Thirty one of 200 consecutive medical patients died. Fourteen necropsies were performed and revealed pulmonary embolism as the cause of death in five patients. The incidence of necropsy proven fatal pulmonary embolism was therefore 2.5% (95% confidence intervals 0.8% to 5.7%). Therefore, one in 40 medical patients had pulmonary embolism recorded as the cause of death at necropsy. As the necropsy rate was only 45% the incidence of fatal pulmonary embolism may be greater. There is, therefore, a need to perform more large prospective studies to confirm the incidence of fatal pulmonary embolism in medical patients and to identify risk factors and effective antithrombotic prophylaxis.     

Mechanical valve replacement in congenital heart defects in the era of international normalized ratio self-management

As the number of patients with congenital heart defects requiring heart valve replacement increases, the need for durable valve substitutes with good hemodynamic performance and a low incidence of complications becomes more apparent. The use of porcine xenografts is burdened with early fibrocalcific degeneration, whereas the use of mechanical heart valves led to an increased number of thromboembolic events, especially when implanted in the right side of the heart. We report on our experiences implanting bileaflet heart valves in congenital heart defects since the introduction of international normalized ratio (INR) self-management. The data of 68 long-term survivors (33 males, 35 females) who underwent mechanical heart valve replacement in congenital heart defect were reviewed. Patient age at the time of valve replacement ranged from 5 months to 61 years (mean 21 years). Underlying diagnoses were tetralogy of Fallot (n=33), morbus Ebstein (n=4), atrioventricular canal (n=13), truncus arteriosus communis (n=5), transposition of the great arteries (n=10), and congenitally corrected transposition of the great arteries (n=3). In all patients, bileaflet valves were implanted (St. Jude Medical n=40, Carbomedics n=28). Anticoagulation was performed using dicumarol (Marcumar) and INR self-management in all cases. The mean follow-up was 72 months (range 6-132 months; 409 patient-years). Valve thrombosis developed in 3 of 68 patients (4.4%, all three had tetralogy of Fallot, mean age 9.8 years) after a mean follow-up of 3.5 years. In two of these three patients, re-pulmonary valve replacement was necessary, whereas the third patient was treated by thrombolysis. From our experience, we conclude that mechanical heart valve replacement is a good therapy option with a low complication rate for patients with congenital heart defects requiring valve replacement, especially when INR self-management is performed.     

Observation of cavitation in a mechanical heart valve in a total artificial heart

Recently, cavitation on the surface of mechanical heart valves has been studied as a cause of fractures occurring in implanted mechanical heart valves. The cause of cavitation in mechanical heart valves was investigated using the 25 mm Medtronic Hall valve and the 23 mm Omnicarbon valve. Closing of these valves in the mitral position was simulated in an electrohydraulic totally artificial heart. Tests were conducted under physiologic pressures at heart rates from 60 to 100 beats per minute with cardiac outputs from 4.8 to 7.7 L/min. The disk closing motion was measured by a laser displacement sensor. A high-speed video camera was used to observe the cavitation bubbles in the mechanical heart valves. The maximum closing velocity of the Omnicarbon valve was faster than that of the Medtronic Hall valve. In both valves, the closing velocity of the leaflet, used as the cavitation threshold, was approximately 1.3-1.5 m/s. In the case of the Medtronic Hall valve, cavitation bubbles were generated by the squeeze flow and by the effects of the venturi and the water hammer. With the Omnicarbon valve, the cavitation bubbles were generated by the squeeze flow and the water hammer. The mechanism leading to the development of cavitation bubbles depended on the valve closing velocity and the valve stop geometry. Most of the cavitation bubbles were observed around the valve stop and were generated by the squeeze flow.