Cytomegalovirus infection and the postperfusion syndrome. Recognition of primary infections in four patients

Cytomegalovirus as a cause of immunosuppression following aortic valve replacement

The postperfusion syndrome, haemolytic anaemia and thrombocytopenic purpura following open heart surgery have all been attributed to acute cytomegalovirus (CMV) infection,'-3 usually acquired from perioperative transfusions of whole blood. Increased susceptibility of bacterial infections has been described,4 but only in patients who have undergone cardiac transplantation and consequently received immunosuppressive therapy. Studies have shown that CMV can suppress cell-mediated immunity in vivo and in vitro5 and impairment of neutrophil migration has been demonstrated in CMV infected mice.6 We describe a patient with impaired polymorph function associated with an acute CMV infection following aortic valve replacement.

Post-transfusion cytomegaloviremia and persistence of cytomegalovirus in blood

Cytomegaloviremia was documented in seven patients. Three patients were renal transplant recipients and two were liver transplant recipients. One was a postcardiac surgery patient, and one had acute myelogenous leukemia. The transplant patients had received only banked blood or fresh frozen plasma and developed evidence of infection about 1 month after surgery. Illness varied from no apparent signs to fever alone, fever and a morbilliform rash, hepatitis and an infectious mononucleosis syndrome. The virus was isolated from the blood erythrocyte layer, the leukocyte layer, and the plasma and serum, in that order of frequency. In vitro studies demonstrated persistence of inoculated cytomegalovirus in the presence of erythrocytes (and tissue culture media) for up to 21 days. In whole blood under banking conditions, inoculated virus was recovered after 28 days and, in fresh frozen plasma, after 97 days.

Incidence of cytomegaloviremia in blood-bank donors and in infants with congenital cytomegalic inclusion disease

During a 15-month period, cytomegalovirus (CMV) isolations were attempted from leukocytes derived from 290 healthy blood-bank donors. The major proportion of the specimens were tested 2 to 5 hr after donation. However, CMV was not recovered from any of the specimens examined. At the time of donation, 75% of donors had CMV complement-fixing antibodies demonstrable in titers of 10 to >/=320. The age of the study group ranged from 17 to 57 years. During the same time period and with the use of identical isolation techniques, postnatal cytomegaloviremia was demonstrated in four infants with cytomegalic inclusion disease. Failure to detect cytomegaloviremia in 290 normal blood donors questions its occurrence outside pathological conditions. These results do not support the concept that CMV infection, concurrent with post-transfusion mononucleosis syndrome, is transmitted through the blood donor's leukocytes.

Primary cytomegalovirus infection following open heart surgery

Among 674 patients undergoing open heart surgery in 1981-82, 86 (13%) were cytomegalovirus (CMV) antibody-negative when tested by an enzyme-linked immunosorbent assay prior to operation. At follow-up, 54 (67%) of 80 patients restudied had seroconverted after the operation, and 35 of the 54 seroconvertants had been ill with fever and elevated liver enzymes. Among the latter 35 patients, 26 demonstrated a significant rise in CMV antibody titre, most often detected in the third week following the onset of illness. The older patients were more susceptible to illness and seroconversion, and there was a positive correlation between age and the number of blood units given. Thus, at least one third of the seronegative patients developed symptomatic CMV illness after open heart surgery. This is a much higher incidence than earlier reported.

Epidemiology of transmission of cytomegalovirus from mother to preterm infant by breastfeeding

BACKGROUND

Breastfeeding practices strongly influence the epidemiology of human cytomegalovirus infection. By contrast with term neonates, few data are available on transmission of infection from mothers to preterm infants during breastfeeding.

METHODS

151 mothers and their 176 preterm infants (gestational age at birth <32 weeks or birthweight <1500 g) were prospectively screened for cytomegalovirus infection by serology, virus culture, and PCR. The roles of cell-free and cell-associated cytomegalovirus excretion during lactation were analysed longitudinally in relation to transmission, by maximum-likelihood estimates.

FINDINGS

Of the 69 seronegative breastfeeding control mothers, none had detectable cytomegalovirus DNA in breastmilk and none of their 80 infants shed the virus in urine. The proportion of cytomegalovirus reactivation in seropositive breastfeeding mothers was 96% (73 of 76). The early appearance of viral DNA in milk whey (median 3.5 days post partum in transmitters; 8 days in non-transmitters; p=0.025) and infectious virus in milk whey (10 days and 16 days, respectively; p=0.005) were risk factors for transmission. The cumulative rate of transmission was 37% (27 of 73 mothers; 33 infants). The infection of the neonates had a mean incubation time of 42 days (95% CI 28-69). About 50% of the infected infants had no symptoms, but four had sepsis-like symptoms.

INTERPRETATION

The proportion of cytomegalovirus reactivation during lactation almost equals maternal seroprevalence. Breastfeeding as a source of postnatal cytomegalovirus infection in preterm infants has been underestimated and may be associated with a symptomatic infection.

Cytomegalic colitis after total colectomy in ulcerative colitis: report of a case

A 58-year-old man with ulcerative colitis underwent total colectomy and ileorectal anastomosis. Steroid suppositories were administered postoperatively, and he had had no exacerbation in the residual rectum for 12 years. He suddenly presented with frequent bloody stools and anal pain. An intensive intravenous regimen of prednisolone was ineffective. Cytomegalic inclusion bodies were identified in biopsy specimens. Administration of ganciclovir reduced the ulcers remarkably. The clinical course suggested that this deterioration was caused by cytomegalovirus infection from the beginning. Cytomegalovirus colitis should be recognized as an exacerbating factor, even in ulcerative colitis patients who have undergone surgery, especially when the residual bowel inflammation is resistant to steroid therapy.

Progressive encephalopathy associated with cytomegalovirus infection without immune deficiency

Slowly progressive encephalopathy caused by cytomegalovirus is an unusual disorder, and its pathogenesis remains unknown except for cases associated with the acquired immune deficiency syndrome and organ transplantation. We report a case who showed clinical features of progressive encephalopathy. Cytomegalovirus was repeatedly isolated from urine, and cytomegalovirus-infected cells were detected in bone marrow. Serial computed tomographic head scan revealed periventricular calcification and its progression to the thalamus, cerebellum, and brain stem. On autopsy, there were multiple calcifications and diffuse glial proliferation in the gray and white matter. Perivascular inflammation was only minimal. There was no evidence of immune deficiency. This case suggests that progressive encephalopathy can be caused by cytomegalovirus infection without immune deficiency. This type of cytomegalovirus infection may be unusual, but its serious outcome should remind us to detect it accurately.

Transfusion-acquired cytomegalovirus infection in children in a hyperendemic area

Thirty-nine children without previous cytomegalovirus (CMV) infection received blood transfusion in the National Taiwan University Hospital. The overall transfusion-acquired CMV infection rate was 36% (14/39). Donor CMV seropositive rate was 70%. None of the nine children who had received seronegative blood became infected, in contrast to 14 of the 21 children (67%) who had received seropositive blood (P = 0.002). Another significant risk factor associated with CMV infection was the use of fresh blood: 13 of 15 (87%) with fresh seropositive blood were infected, in contrast to one of six (17%) with "old" seropositive blood (P = 0.01). Most of the fresh blood was used within 24 hours. This blood processing method was shown to account for the extremely high rate of CMV infection in those who had received fresh seropositive blood. The results indicated that the incidence of CMV infection can be reduced by avoiding the use of fresh blood, especially blood less than 24 hours old. For such a population in Taiwan with high prevalence of positive CMV antibody, this approach was more applicable than screening donor blood for CMV antibody.

Detection of human cytomegalovirus DNA in human tonsillar lymphocytes

The human cytomegalovirus (HCMV) was first isolated in cell cultures from the oropharynx, which is thought to be a site of primary infection. Although HCMV can be recovered from the oropharynx during reactivation phases, its exact site of latency is not known. In the present study we demonstrated evidence suggesting the presence of latent HCMV in this anatomic region--in the palatine tonsils. Samples from 30 tonsils obtained by tonsillectomy were screened for the presence of HCMV. Out of the 30 tonsil donors, 23 were seropositive for HCMV. Three methods were used in attempts to demonstrate HCMV's presence in the tonsils: (1) viral isolation attempts on various cell cultures, (2) immunohistochemical staining--immunoperoxidase method--designed to detect viral antigens, and (3) DNA dot hybridization with a HCMV-DNA probe designed to detect viral DNA. Neither infectious HCMV nor other viruses were isolated in cell cultures. No viral antigens were detected by immunoperoxidase staining in the tonsillar tissue. Four out of the 30 tonsils studied were found to contain viral DNA. In one case in which the tonsillar mononuclear (MN) fraction was separated from the polymorphonuclear (PMN) fraction, only the first fraction contained the viral DNA.

Transfusion-associated viral infections

Viral infections are a frequent occurrence following transfusion of blood products. While generally benign, these infections are capable of causing significant morbidity and mortality. Therefore, it is prudent to follow several general approaches diligently to reduce the risks of these infections in patients undergoing transfusions of blood products. These suggested measures include the following: 1. Prescribe and administer blood and blood products only when absolutely needed. 2. Use volunteer blood donors only. 3. Avoid use of pooled blood products when possible. 4. Use only blood and blood products that have been appropriately tested for HBsAg and HIV. 5. Use ALT determinations to screen blood products and eliminate those with high level. 6. Avoid the use of clotting-factor concentrates but, if necessary, use only those which have been heat-treated. 7. Limit use of leukocyte transfusion. 8. Use only CMV seronegative blood and blood products or frozen deglycerolized red cells in patients at high risk for posttransfusion CMV infection.

Neonatal cytomegalovirus infections due to blood

Infants with very low birthweights (less than 1250g) are immunocompromised and have immature hematopoietic systems. They require frequent blood transfusions and have an increased susceptibility to infection. These very low birthweight infants who lack passively acquired antibody against CMV, acquire transfusion-associated CMV infections with a frequency of approximately 30%. These infections are associated with significant morbidity and mortality. The source of these postnatally acquired CMV infections are seropositive blood donors. These infections can be prevented by appropriate donor selection and/or blood processing. Recent but limited data suggests that all infants (regardless of birthweight or the presence of antibody against CMV) should receive CMV seronegative blood products if they are likely to receive multiple transfusions from multiple donors.

An update on the acquired immunodeficiency syndrome (AIDS). Associated disorders of the alimentary tract

The pandemic, acquired immunodeficiency syndrome (AIDS) has been described in 40 nations throughout the world. This paper describes the wide spectrum of gastrointestinal tract manifestations seen in this syndrome, with particular attention to the epidemiology, etiology, and measurement of these problems. Discussion of candidiasis, herpes simplex, "hairy" leukoplakia, Kaposi's sarcoma, cytomegalovirus, anal warts and carcinoma, chlamydial proctitis (LGV), coccidiosis, and mycobacterial diarrhea, as well as "gay bowel syndrome," demonstrates the complex management problems associated with this condition.

Detection of human cytomegalovirus in peripheral blood lymphocytes in a natural infection

In situ hybridization was used to detect human cytomegalovirus (HCMV) in the peripheral blood mononuclear cells of some naturally infected (seropositive) individuals. A subpopulation of cells hybridized specifically to a portion of the HCMV genome that is heavily transcribed during the immediate-early period of infection. The hybridization signal was markedly reduced by base hydrolysis and ribonuclease, and therefore the probe appears to be detecting viral RNA. A fluorescence-activated cell sorter was used to select lymphocytes bearing the OKT4 and OKT8 markers. Hybridization with the HCMV probe revealed a higher proportion of positive cells in the OKT4 than in the OKT8 subset. This observation specifically identifies lymphocytes as a cell population involved in natural HCMV infection and suggests that lymphocytes may be a reservoir for maintaining infection and may also serve as a vehicle for its spread by blood transfusion.

Studies of latent cytomegalovirus infection: the macrophage as a virus-harboring cell

During chronic infection of mice with mouse cytomegalovirus (MCMV), the virus was isolated from various tissues by cocultivation with allogeneic mouse embryonic fibroblasts (MEF). Infectious virus was recovered from over 15% of the pancreases, salivary glands, kidneys, lacrimal glands, and spleens. When activated macrophages were obtained by intraperitoneal injection of peptone into mice infected 3 months earlier, they harbored MCMV. Macrophages or lymphocytes were infected with MCMV in vitro and injected into normal mice intravenously. The peritoneal cavities of these mice were then stimulated by peptone injection 3 months after the transfer, and peritoneal or splenic macrophages and lymphocytes were cocultured with allogeneic MEF. MCMV was recovered from the peritoneal and splenic macrophages and not from the lymphocytes.

Cytomegalovirus infection with acute erosive esophagitis

A healthy young adult is described in whom acute erosive esophagitis developed four weeks after undergoing splenectomy and receiving six units of blood because of trauma. Cytomegalovirus inclusion bodies were identified in esophageal mucosa, and cytomegalovirus was cultured from blood and throat. Within three weeks, the patient's anticytomegalovirus antibody had increased four-fold. The patient was initially anergic and had a titer of antinuclear antibody of 1:10,240. His symptoms and histopathologic findings disappeared over five weeks, and his immunologic abnormalities were partially corrected. It is suggested that cytomegalovirus was the primary cause of gastrointestinal disease in this nonimmunocompromised patient.

Immunity to human cytomegalovirus measured and compared by complement fixation, indirect fluorescent-antibody, indirect hemagglutination, and enzyme-linked immunosorbent assays

The complement fixation test is currently the test employed most frequently to determine the presence of antibody to human cytomegalovirus. Several other techniques have been adapted for this purpose. A comparison of cytomegalovirus antibody titers was made between the complement fixation test, a commercially available enzyme-linked immunosorbent assay, an indirect immunofluorescent technique, and a modified indirect hemagglutination test. Forty-three serum samples were tested for antibodies by each of the above procedures. The enzyme-linked immunosorbent, immunofluorescent, and indirect hemagglutination assays were in close agreement on all samples tested; the titers obtained with these methods were all equal to or greater than the complement fixation titer for 38 of the 41 samples (92.6%). Two samples were anticomplementary in the complement fixation test but gave readable results in the other tests. The complement fixation test was the least sensitive of the procedures examined. The commercial enzyme-linked immunosorbent assay system was the most practical method and offered the highest degree of sensitivity in detecting antibodies to cytomegalovirus.

Drug therapy. Treatment of herpesvirus infections

Guidelines for the prophylaxis or therapy of herpesvirus infections are shown in Table 1. Progress is so rapid in this area that frequent revisions of such guidelines will be necessary. Newer drugs or new formulations of older agents are constantly being developed. Combination therapies--e.g., interferon plus acyclovir--appear promising in laboratory models of herpesvirus infections and will undoubtedly receive clinical investigation in the years ahead. The problem of dealing with latent virus infections still eludes us, and major breakthroughs will be necessary before we can discuss cure of recurrent infections. Nevertheless, important strides have been made in the past few years, and further progress is predictable in the years ahead.

Specific IgM class antibody production following infection with cytomegalovirus

Specific IgM class antibody production was studied in different groups of patients with characterized cytomegalovirus (CMV) infections using a radioimmunoassay (RIA). In pregnant women, IgM antibodies were detected only following primary infection and generally persisted less than 4 months. The demonstration of CMV-specific IgM during pregnancy is therefore diagnostic of recent primary CMV infection. In patients with symptomatic CMV infections, the appearance of IgM antibody was shown to be closely related to the onset of symptoms and coincided with production of complement fixing (CF) antibody. IgM antibodies were at maximum levels 3-4 weeks after presentation but generally declined to low or undetectable levels by 3-4 months. The significance of the results of testing for CMV-specific IgM in relation to clinical and other serological findings in these patients is discussed. IgM antibody production was also demonstrated in renal transplant patients with primary infections and in 6 of 21 recipients with secondary infections. In both groups the antibodies became detectable 3-6 weeks after transplantation but the titres were much higher following primary infection. IgM antibodies persisted throughout follow-up periods of up to 2 years after transplantation in some cases.

Cytomegalovirus-induced mononucleosis in guinea pigs

The effects of cytomegalovirus (CMV) infection on hematopoietic and lymphoid tissues were studied in guinea pigs. Blood parameters, histopathology, and virus distribution in the bone marrow, spleen, lymph nodes, and thymus were assessed during primary nonlethal acute and chronic guinea pig CMV infection. Transient hematological changes comparable to those seen in human CMV mononucleosis were observed during acute infection. These included anemia and leukocytosis with atypical lymphocytes. Splenomegaly and stimulation of spleen and lymph node T- and B-cell areas were also noted. These changes occurred at the peak of virus recovery from all tissues tested, as well as from macrophages and B- and T- cell-enriched spleen subpopulations. Virus was cleared rapidly from blood and bone marrow; blood counts, spleen size, and histology returned to normal within 1 month after virus inoculation. However, guinea pigs failed to eliminate the virus completely from lymphoid tissues, since virus persisted in splenic macrophage and B-lymphocyte-enriched populations during chronic infection. The data suggest that CMV-infected mononuclear cells play a role in the establishment of generalized acute infection and virus persistence.

Cytomegalovirus myocarditis

A male patient, aged 31 years, with a cytomegalovirus (CMV) myocarditis is described, who showed a high IgM antibody titer for cytomegalovirus infection of 1:1,024 and a rise of the titer for complement-fixing antibody from 1:< 16 to 1:256. CMV could be isolated from the urine. Investigations for other etiological factors were negative, and we assumed a connection between the cytomegalovirus infection and the myocardial involvement.

Demonstration of IgG EA (early antigen) and IgM MA (membrane antigen) antibodies in CMV infection of healthy infants and in those with liver disease

The sequence of antibody production to various virus-specific antigens in CMV infection in infancy was studied. In healthy infants, IgG EA antibody was demonstrated in 18% of cord sera, and disappeared within two months after birth in all cases not shedding virus. The nonmaternal EA antibody was produced following virus excretion and decreased rapidly following cessation of virus excretion. Thus, demonstration of EA antibody in infants after 2 months of age was found to indicate acquired CMV infection, even when CMV could not be isolated. IgM MA antibody did not persist as long as EA antibody, disappearing before cessation of virus excretion. Both IgG EA and IgM MA antibodies were more frequently demonstrated in infants with hepatitis than in healthy infants. These findings suggest the possible association of CMV with hepatitis in infants.

Autologous transfusion in obstetrics and gynecology

Two cases are presented which illustrate the use of autologous blood transfusion for elective surgery in obstetrics and gynecology. The advantages and disadvantages are described and review of the pertinent literature over the past century is summarized.

Cytomegalovirus granulomatous hepatitis

Three patients with granulomatous hepatitis due to cytomegalovirus are described. They are compared to the three previously described patients with this disease, and their clinical and serologic characteristics are discussed. Similarities and differences between infectious mononucleosis (Epstein-Barr virus) and cytomegalovirus infections are adduced. That cytomegalovirus may be a cause of granulomatous hepatitis in the adult is stressed.

Epidemiology of cytomegalovirus infection in end stage renal disease

Since primary cytomegalovirus (CMV) infection is a cause of morbidity among renal transplant recipients, we undertook a prospective study of our maintenance hemodialysis patients and personnel to determine whether these sources posed a risk for transmission of CMV. Our study of 85 patients and 49 personnel showed that CMV was detected in eight nontransplanted, older dialysis patients and 13 patients who had lost their allograft. In spite of the presence of CMV on the unit, no patient or staff member developed primary infection from interpersonal transmission or from transfused frozen red blood cells. All primary infections in renal transplant patients could be accounted for by acquisition from the transplanted kidney, thus eliminating the dialysis unit or frozen blood as a risk to either patients or personnel.

Perinatal cytomegalovirus infection in man

In a prospective study of 148 children from urbanized southern Finland 3 were found to be congenitally and 48 perinatally infected with cytomegalovirus (CMV), while 6 developed "late" infection during the first year of life. During pregnancy and the first year after delivery 23 of the mothers had no CMV antibodies; none of the children of these seronegative mothers developed any type of CMV infection. Fresh blood exchange transfusions did not increase the risk of CMV infection. The data support the hypothesis that the mother is the source of perinatal CMV infection. Children with a low birthweight not due to prematurity, and first children seem to run a greater risk of acquiring perinatal CMV infection. If the child is breast fed up to the age of 2 months the risk seems to be increased. Perinatal CMV infection gave rise to no symptoms or signs and had no effect on growth or on motor and psychosocial development during the first year of life.

Cytomegalovirus-induced haemolytic anaemia after cardiac surgery

A patient, who underwent aortic valve replacement, developed a transient, autoimmune haemolytic anaemia in association with a significant rise in titre of antibodies against cytomegalovirus. A serological survey of blood donors indicated that the source of infection was fresh blood transfused during and shortly after surgery. A number of cases of short-lived haemolytic anaemia after large volume blood transfusion with cardiac surgery may be explained by this mechanism. It may be preferable to use only blood that has been screened for evidence of recent cytomegalovirus infection if post-perfusion complications of this disease are to be avoided.

Blood as a potential vehicle for the cytomegaloviruses

This study analyzed transfused blood as a potential vehicle for infectious cytomegalovirus (CMV) particles. A total of 207 patients who received a total number of 897 units of blood were monitored. A complement-fixing antibody titer of 1:8, as determined by micro-titer technique, was observed in 14.8 per cent of the blood units. A total of 140 individuals in this study were serosusceptible. Eighty-six serosusceptible individuals did not receive blood containing complement-fixing CMV antibodies. In this patient population three instances of seroconversion were identified. Among the 54 serosusceptible individuals who received at least one unit of blood whose complement-fixing titer to the AD-169 strain of CMV was 1:8 or greater, 13 seroconversions were observed.

Cytomegalovirus infection and immunity in renal allograft recipients: assessment of the competence of humoral immunity

Cytomegalovirus (CMV) infections are prevalent in renal allograft recipients. The purpose of this ongoing study is to attempt to elucidate the mechanism(s) responsible for the enhanced susceptibility to CMV infections on the part of transplant patients and for their apparent inability to eradicate the infection once it starts. The present report assesses the competence of humoral immunity to CMV in renal allograft recipients. The total study population was comprised of 41 renal allograft recipients (10 followed prospectively) and 38 age-matched control subjects. The overall CMV infection rate in renal allograft recipients was 90.2%, and in 11 cohort control subjects it was 45.5%. Active infection was present in 61.0% of transplant patients (24.0% of these had CMV disease) and in 18.2% of the cohorts. THESE DIFFERENCES ARE SIGNIFICANT. CMV complement fixation and neutralization antibody prevalence was similar in 10 patients with renal failure undergoing hemodialysis before transplantation and in 23 control subjects. There was similarly no difference in antibody response between allograft recipients in whom the infection was primary (eight subjects) or secondary (17 subjects). We conclude that despite immunosuppressant therapy (with azathioprine and corticosteroids), humoral immunity to CMV is not impaired in transplant patients with either a primary or secondary infection.

Cytomegaloviremia in children with acute lymphocytic leukemia

Leukocyte and urine cultures were done at monthly intervals in 36 children with acute lymphocytic leukemia known to be excreting cytomegalovirus in their or saliva in order to determine the relationship of viremia to clinical cytomegalic inclusion disease. Eleven of 36 (30.5%) patients had viremia. Viremia was related to clinical disease in only three patients; two with chorioretinitis and one with a CMV monomucleosis syndrom. However, the presence of viremia did not serve as a useful means to determine active CID. Viremic patients with CID all had elevated serum levels of IgM and multiple episodes of viremia. Viremia was not related to the duration, type or number of drugs used in immunosuppression, nor to the hematologic status of leukemia. Viremic patients received more blood transfusions than noviremic patients, but the administration of blood products could not be related to the acquisition of infection. Leukopenia, neutropenia, total lymphocyte count, fourfold rise or fall in complement-fixing titer, and viruria had no consistent relationship to viremia or clinical CID.

Diagnosis and management of complications of prosthetic heart valves

Complications after heart valve replacement remain a substantial source of morbidity and mortality despite continuing advances in surgical care and prosthetic design. Infectious endocarditis occurs in about 4 percent of patients and may appear early (within 60 days) or late after operation. Endocarditis of early onset is commonly due to staphylococcal, fungal or gram-negative organisms and is fatal in 70 percent or more of cases. Infection of late onset is more often of streptococcal origin and the mortality rate is lower, about 35 percent. With either type, prompt recognition, vigorous and appropriate antimicrobial therapy and early consideration of surgical intervention are crucial. The postperfusion and postpericardiotomy syndromes are relatively common and relatively benign syndromes associated with postoperative fever. Their recognition is important to prevent confusion with endocarditis or sepsis and thus to reassure the patient and physician. Treatment is primarily symptomatic. Intravascular hemolysis occurs with most prosthetic heart valves but is more common with certain prostheses and with paraprosthetic valve regurgitation, with significant hemolytic anemia in 5 to 15 percent. Oral iron replacement therapy is effective in the majority of patients, but occasionally blood transfusion or reoperation for leak around the prosthesis is necessary. Prosthesis dysfunction due to thrombus may be recognized clinically by recurrence of heart failure, syncope, cardiomegaly and altered prosthetic valve sounds or new murmurs. Hemodynamic studies verify the diagnosis, and prompt reoperation is indicated for this potentially lethal problem. Systemic embolization has decreased markedly with the introduction of cloth-covered prostheses and is frequently related to erratic or ineffective anticoagulant therapy. We continue to recommend anticoagulant therapy for all patients with prosthetic heart valves unless there is a major contraindication.