Approach to the analysis of cardiac valve prostheses as surgical pathology or autopsy specimens

Pathologists are likely to encounter substitute heart valves with increasing frequency. Informed evaluation of such valves provides valuable information that contributes to both patient care and our understanding of the pathobiology of host interactions with mechanical devices. This article summarizes the most important considerations underlying such analyses—including valve identification, common morphologic features and modes of failure, technical details of evaluation, and potential pitfalls.     

Cardiac involvement in Wegener granulomatosis diagnosed at autopsy

Wegener granulomatosis (WG) is a systemic vasculitis classically involving the lungs, kidneys, and upper respiratory tract. Involvement of other sites does occur but is less frequent. Clinically evident cardiac involvement is uncommon. There are only a few cases in the literature with documentation of the histologic appearance of cardiac involvement in WG. We report a case of a previously healthy 37-year-old man who presented with a one-week history of cough and weakness and a one-day history of shortness of breath. At presentation, he was hypoxic and required intubation. Upon hospitalization, he deteriorated rapidly, became bradycardic and expired the same night. Infection was suspected clinically as the cause of illness and death. At autopsy, the lungs showed diffuse alveolar hemorrhage with capillaritis, diffuse alveolar damage, and parenchymal necrosis with necrotizing granulomas. The heart was enlarged and showed a mixed inflammatory infiltrate composed of neutrophils, eosinophils, and histiocytes, with focal myocyte necrosis. Granulomas, giant cells, and vasculitis were absent. The esophagus showed submucosal vasculitis. A diagnosis of WG was made. Postmortem serology for c-ANCA was positive, and all cultures were negative, confirming the diagnosis. Cardiac involvement is an underrecognized and potentially fatal complication of WG. The histologic findings in the heart may consist of a non-specific inflammatory infiltrate without granulomas or vasculitis, raising a wide differential diagnosis.     

Cardiac botryomycosis: an autopsy report

Visceral botryomycosis is rare, and documented sites are lung, brain, kidney, liver and prostate. This report describes a rare autopsy case of disseminated visceral botryomycosis, with bulky, grape-like botryomycotic vegetations in the heart, and similar abscesses in the lungs and bone marrow. This is the first such report in the literature to the best of our knowledge.     

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.     

Pulsatile flow experiments on heart valve prostheses

In vitro fluid dynamic characteristics of aortic valve prostheses were experimentally measured for physiological relevant pulsatile flows using hot-film velocimetry. The prostheses studied were (i) centrally occluding ball-in-cage and (ii) tilting disc valves. The valves sewn to a plexiglass ring were placed in a specially designed valve chamber. The valve chamber was mounted in a mock circulatory system in which glycerol solution was used as the blood analogue fluid. Physiological pulsatile flow experiments were conducted at a time-averaged flow rate of 86·7 cm³s^?1, (mean Reynolds number of 1320 based on the cross-sectional averaged velocity with a tissue annulus, diameter, of 27 mm). With the aid of a three-sensor probe, the instantaneous values of the three velocity components (component along the axis, as well as radial and tangential velocity, components in a cross-section) were measured and used to compute the mean velocity profiles as well as turbulent normal stresses. The results showed that peak turbulent normal stresses were obtained at 108 ms after the opening of the valves with maximum magnitudes of 110 Pa, 45 mm downstream from the silastic ball valves, compared to about 35 Pa for the stellite ball valve. The largest turbulent normal stresses of about 150 Pa were obtained behind tilting disc valves in the minor flow region parallel to the tilt axis.     

Results of valve replacement surgery with mechanical prostheses

The clinical study is reported of the results of heart valve replacement surgery with a new pyrolytic carbon tilting disc prosthesis manufactured in Italy. From March 1977 to January 1981, at the "De Gasperis" Cardiosurgery Center, this prosthesis has been implanted in 644 patients: 283 for mitral valve replacement, 240 for aortic valve replacement, and 121 for the replacement of both mitral and aortic valves. To have a sufficiently long period of post-surgery follow-up, we considered the results of 207 patients (124 cases of isolated mitral valve replacement and 83 cases of isolated aortic valve replacement), who underwent surgery consecutively from March 1977 to December 1979. The hospital mortality was 10.5% for mitral valve replacement and 4.8% for aortic valve replacement. All patients who were discharged from hospital, except 2, were subjected to clinical, electrocardiographic, phonocardiographic, echocardiographic and radiological checks. The average follow-up period was approximately 20 months: clinical results were satisfactory. The probability of survival, expressed by actuarial curve, was, three years after surgery, 94% for patients who underwent mitral valve replacement and 97.5% for those who underwent aortic valve replacement. The probability of embolism was, three years after surgery, 8.5% for patients with mitral replaced and 5% for aortic. Even if further confirmations are needed the mortality rate and the probability of embolism related to this new prosthesis, are lower, over the same period of follow-up, than that found in the groups of patients who underwent valve replacement surgery, at the same Center, with Starr-Edwards and Bj?rk-Shiley prostheses. The phonocardiographic and echocardiographic characteristics of this new prosthesis were also investigated.     

Pathogenesis of fungal infection on heart valve prostheses

Four patients with heart valve prostheses developed Candida endocarditis. At autopsy the foci of infection were confined to patches of neoendocardium that appeared to have developed as ingrowths of host endocardium onto the sewing cloth of the artificial valve. This suggested that one mechanism of fungal infection is related to the presence of the neoendocardium rather than to the cloth or metallic substances of the valve itself. Future studies might be directed toward inhibiting the development of the neoendocardium or to agents preventing its susceptibility to infection.     

Cardiac sarcoidosis: two cases with autopsy findings

Cardiac sarcoidosis is a disease of young adults. In most cases it presents with sudden death, arrhythmias, conduction disorders, heart failure or cardiomyopathy. The authors describe two cases of myocardial involvement by sarcoidosis that lead to death of the patients. Case one was a 26-year-old Indian man who was previously well and presented with sudden death. Autopsy showed nodules of sarcoid granuloma involving the heart, lungs and lymph nodes. Case two was a 47-year-old Indian lady who complained of reduced effort tolerance. Echocardiography showed that she had restrictive hypertrophic cardiomyopathy with heart failure. Seven months after initial presentation, she developed worsening of heart failure and died. Autopsy revealed involvement of the heart, lungs and liver by sarcoidosis.     

Chemical stabilization method for bionics series heart valve prostheses

Conclusions 1. Chemical treatment of heart valve bioprostheses utilizing sodium dodecylsulfate is, according to experimental findings, the optimum at the present time since this treatment inhibits the development of calcification, increases hemocompatibility, and reduces immunogenicity of the biotissue as compared with the standard method (treatment with 0.625% glutaric aldehyde). 2. Treatment of bioprostheses with sodium dodecylsulfate does not solve the root problem of biotissue calcification. A. N. Bakulev Institute of Cardiovascular Surgery, Academy of Medical Science of the USSR. Scientific Research Institute of Transplantology and Artificial Organs, Ministry of Health of the USSR, Moscow. Translated from Meditsinskaya Tekhnika, No. 4, pp. 30–33, July–August, 1990.     

The closing behavior of mechanical aortic heart valve prostheses

Mechanical artificial heart valves rely on reverse flow to close their leaflets. This mechanism creates regurgitation and water hammer effects that may form cavitations, damage blood cells, and cause thromboembolism. This study analyzes closing mechanisms of monoleaflet (Medtronic Hall 27), bileaflet (Carbo-Medics 27; St. Jude Medical 27; Duromedics 29), and trileaflet valves in a circulatory mock loop, including an aortic root with three sinuses. Downstream flow field velocity was measured via digital particle image velocimetry (DPIV). A high speed camera (PIVCAM 10-30 CCD video camera) tracked leaflet movement at 1000 frames/s. All valves open in 40-50 msec, but monoleaflet and bileaflet valves close in much less time (< 35 msec) than the trileaflet valve (>75 msec). During acceleration phase of systole, the monoleaflet forms a major and minor flow, the bileaflet has three jet flows, and the trileaflet produces a single central flow like physiologic valves. In deceleration phase, the aortic sinus vortices hinder monoleaflet and bileaflet valve closure until reverse flows and high negative transvalvular pressure push the leaflets rapidly for a hard closure. Conversely, the vortices help close the trileaflet valve more softly, probably causing less damage, lessening back flow, and providing a washing effect that may prevent thrombosis formation.