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PubMed2003

Under-ascertainment of mosaic carriers of balanced homologous acrocentric translocations and isochromosomes.

Acrocentric rearrangements are the most common chromosome abnormalities in humans. Carriers of homologous acrocentric rearrangements (Robertsonian translocations (ROBs) between homologous chromosomes and isochromosomes) are at very high risk of having multiple spontaneous abortions and chromosomally abnormal offspring. Parents of fetuses and children with unbalanced homologous acrocentric rearrangements are rarely found to be carriers or mosaic for the same rearrangement. Even though recurrent miscarriages may indicate a carrier parent, carriers are rarely identified. Comparison of non-chromosome 21 homologous rearrangements to rea(21q21q) culled from the literature revealed a 7-fold decrease in the number of mosaic cases among the parents of non-rea(21q21q) offspring. This under-ascertainment in parents may be due to low level mosaicism confined to the gonads, a true biological difference between chromosome 21 rearrangements and other homologous acrocentric rearrangements, or simply to the lack of rigorous clinical investigation of the parental karyotypes to uncover mosaicism. We recommend that polymorphic marker analysis be applied to apparently de novo acrocentric rearrangements to distinguish those resulting from biparental postzygotic formation from those resulting from meiotic formation; the latter of which may indicate a potential carrier parent. Parental chromosomal constitutions could then be screened in a large number of cells and in more than one tissue type to identify mosaicism. Identification of mosaicism allows for accurate genetic counseling and discussion of reproductive options. However, given that mosaicism may be restricted to the gonads, prenatal testing is likely to be desired by the family whether or not mosaicism is found.

Chromosome Aberrations↗
PubMed2006

Variable outcomes in mosaic trisomy 16: five case reports and literature analysis.

OBJECTIVES: To report five cases of mosaic trisomy 16 with variable outcomes in the context of the literature on mosaic trisomy 16. Complications in these cases include preeclampsia, IUGR, fetal anomalies, and death, with no predictable pattern. METHODS: Observation of five new cases and statistical analysis of 125 reported cases of mosaic trisomy 16 with prenatal detection and outcome data. RESULTS: (1) IUGR, premature delivery, and/or physical anomalies are observed commonly, even when the trisomy is thought to be confined to the placenta; (2) Level II mosaicism for trisomy 16 in amniotic fluid may reflect a true mosaic state with phenotypic consequences; (3) FISH is more sensitive than traditional cytogenetics in detecting mosaicism in all tissue types examined; (4) hCG levels can be extremely elevated, and MS-AFP levels are often elevated; and (5) Uniparental disomy (UPD) increases the rates of IUGR and physical anomalies in CPM cases. CONCLUSION: While there is no obvious mosaic trisomy 16 syndrome, IUGR and heart defects commonly occur, even if the mosaicism appears to be confined to the placenta. A completely normal outcome occurs only in about 20% of the cases; however, complications can often be limited to prematurity, small-for-gestational-age infants, and/or minor or surgically reparable birth defects.

Adult↗
PubMed2004

Clinical, cytogenetic, and molecular analyses of prenatally diagnosed mosaic tetrasomy for distal chromosome 15q and review of the literature.

OBJECTIVES: To present prenatally detected mosaic tetrasomy for distal chromosome 15q and a review of the literature. CLINICAL SUBJECT AND METHODS: Amniocentesis was performed at 17 weeks' gestation because of advanced maternal age. Cytogenetic analysis revealed mosaicism for an analphoid supernumerary marker chromosome (SMC). The parental karyotypes were normal. Fluorescence in situ hybridization (FISH) and polymorphic DNA marker analysis were applied to study the origin of the SMC. Level II ultrasound revealed gastric dilation. The pregnancy was terminated, and a malformed fetus was delivered with characteristic dysmorphism. Multiple samplings of fetal and extraembryonic tissues were performed to investigate the mosaicism. RESULTS: Initial amniocentesis revealed mos 47,XY,+ mar[20]/46,XY[1], and repeat amniocentesis revealed 47,XY,+ mar[28]/46,XY[8]. FISH and polymorphic DNA marker analysis determined an origin from the distal 15q and an inverted duplication of 15q25.3 --> qter for the SMC. Karyotype of the fetus was designated as 47,XY,+ ace i(15) (qter --> q25.3::q25.3 --> qter)/46,XY de novo. The levels of tetrasomy for distal 15q were 28/40 in cord blood, 13/40 in liver, 14/40 in lungs, 27/40 in skin, 0/40 in placenta, and 40/40 in umbilical cord. The placenta showed an equal biparental inheritance (1:1). The umbilical cord inherited one copy of a paternal allele and three copies of a maternal allele (1:3) at distal 15q. Diallelic patterns with dosage ratios (paternal allele: maternal allele) of 1:2.5 in amniocytes, 1:2.3 in amnion, 1:2.2 in cord blood, 1:2.1 in skin, 1:1.4 in liver, and 1:1.4 in lungs. A maternal origin of the mosaic SMC(15) was determined. CONCLUSIONS: A diagnosis of mosaic analphoid SMCs in amniocytes should alert mosaic mirror-image duplication of euchromatin from some distal chromosomal segment such as distal 15q or distal 13q, and a risk for fetal abnormalities. Fetuses with mosaic tetrasomy for distal 15q may be associated with fetoplacental chromosomal discrepancy. Postnatal samplings of umbilical cord, placenta and amniotic membrane may provide additional clues to the cytogenetic discrepancy between fetal and extraembryonic tissues in prenatally detected mosaic analphoid SMCs.

Abnormalities, Multiple↗
PubMed1998

Germ line mosaicism.

Mosaicism in germ cells has been recognized, over the past few years, as an important and relatively frequent mechanism at the origin of genetic disorders. There are two possibilities for the existence of such a mosaicism: one is that the mutation occurs in a germ cell that continues to divide. The other possibility is that the mutation occurs very early in a somatic cell before the separation to germinal cells and is therefore present both in somatic and germinal cells. Depending on various factors, such as the gene involved and/or the degree of mosaicism, the carrier of a somatic and germline mosaicism may be asymptomatic or may present with various symptoms of the disease. There are still relatively few reports in the literature in which the origin of germ-line mosaicism has been analyzed; nevertheless, they allow for a better insight into the mechanisms involved. In some diseases, such as osteogenesis imperfecta, new mutations are often present as asymptomatic somatic and germline mosaicism in one of the parents of the propositus. In other disorders, such as neurofibromatosis, somatic mosaicism is very rare in the parents of the propositus, perhaps since such mosaicism causes clinical symptoms. These differences are particularly important for genetic counseling in order to evaluate the risk for another affected child after the birth of the propositus.

Female↗
PubMed1996

A program for analyzing the morphological organization of tessellated cellular mosaics.

We have constructed a computer program that allows sequential sets of data from tessellated cellular mosaics to be evaluated such that the presence and position of abnormal cells in the mosaic can be easily, quickly, and quantitatively identified. Conventional parametric analysis of the global morphological organization of large tessellated cellular mosaics does not provide the necessary granularity of analysis to allow for rapid identification of such atypical cellular structures. Our program, written in C using structured programming techniques, provides the needed analytical granularity for detailed studies of subsections of large cellular mosaics, while also providing conventional statistical evaluation of the data set. The architecture of the program is modular and designed as a set of procedures and subprocessess that can either analyze the entire mosaic or discrete sets of cells within the larger sample. The types of morphological heterogeneity (or dishomogeneity) that the program can investigate occur in a variety of biological mosaics where there is a continuum of the structural features, including fairly regular linear stacked arrays of cells or tissue partitions, to less regular mosaics of epithelial or endothelial cell layers, to heterogeneous patterns found on tissue surfaces, such as fluorescein dye-highlighted features on the human conjunctiva. The program has been used to successfully evaluate several different types of mosaics.

Body Patterning↗
PubMedDate not supplied

Cytogenetics and fluorescence in situ hybridization assessment of sex-chromosome mosaicism in Klinefelter's syndrome.

A retrospective study was carried out in 152 infertile men to determine the prevalence of sex chromosome abnormalities among non-obstructive azoospermic and severe oligospermic men (n = 51) and to evaluate the feasibility of fluorescence in situ hybridization (FISH) techniques to assess mosaicism in Klinefelter's patients in comparison with conventional cytogenetics. Cytogenetic analysis were performed for 51 infertile men and among 14 chromosomal abnormalities found, nine were compatible with Klinefelter's syndrome. FISH staining with a CEP X/CEP Y probes were performed for Klinefelter's patients and for five of them; testes were biopsied for histopathologic examination. Six Klinefelter's patients showed a non-mosaic 47,XXY and three showed a 47,XXY/46,XY mosaic by G or R banding analysis of 20 cells with a ratio of 17%, 20% and 33%, respectively. FISH analysis confirmed mosaicism in only one patient (the first) in whom a third cells population was found. There was no relationship between the ratios of mosaicism by banding and FISH analysis. Conventional histopathologic findings in five non-mosaic Klinefelter's patients confirm the diagnosis of Sertoli Only Cells syndrome. FISH is recommended in Klinefelter's syndrome to define exactly the cytogenetic statute as mosaic or non-mosaic and then discussing prognosis and decision regarding fertility counseling.

Humans↗
PubMed1988

Fetal blood sampling in investigation of chromosome mosaicism in amniotic fluid cell culture.

41 pregnancies in which mosaicism had been found on amniotic fluid culture (AFC) were investigated by fetal blood and repeat AFC karyotyping. Results of both investigations, and the infants, were normal in 15 of 16 cases of autosomal trisomy (including trisomies 8, 9, 13, 18, and 21) and in the 8 cases of sex chromosome mosaicism. In 1 case of trisomy 20 mosaicism the fetal blood karyotype and the infant were normal but the repeat AFC showed mosaicism. Abnormality was confirmed in 5 of 11 cases of mosaicism for structural chromosomal rearrangements and in 4 of 6 cases with de-novo supernumerary marker mosaicism. These findings indicate the potential danger of terminating pregnancies because of trisomic mosaicism in AFC, and the importance of identifying the clinical significance of certain chromosome rearrangements which, even in mosaic form, might lead to severe mental and developmental handicap.

Adult↗
PubMed1996

Bypass of lethality with mosaic mice generated by Cre-loxP-mediated recombination.

BACKGROUND: The analysis of gene function based on the generation of mutant mice by homologous recombination in embryonic stem cells is limited if gene disruption results in embryonic lethality. Mosaic mice, which contain a certain proportion of mutant cells in all organs, allow lethality to be circumvented and the potential of mutant cells to contribute to different cell lineages to be analyzed. To generate mosaic animals, we used the bacteriophage P1-derived Cre-loxP recombination system, which allows gene alteration by Cre-mediated deletion of loxP-flanked gene segments. RESULTS: We generated nestin-cre transgenic mouse lines, which expressed the Cre recombinase under the control of the rat nestin promoter and its second intron enhancer. In crosses to animals carrying a loxP-flanked target gene, partial deletion of the loxP-flanked allele occurred before day 10.5 post coitum and was detectable in all adult organs examined, including germ-line cells. Using this approach, we generated mosaic mice containing cells deficient in the gamma-chain of the interleukin-2 receptor (IL-2R gamma); in these animals, the IL-2R gamma-deficient cells were underrepresented in the thymus and spleen. Because mice deficient in DNA polymerase beta die perinatally, we studied the effects of DNA polymerase beta deficiency in mosaic animals. We found that some of the mosaic polymerase beta-deficient animals were viable, but were often reduced in size and weight. The fraction of DNA polymerase beta-deficient cells in mosaic embryos decreased during embryonic development, presumably because wild-type cells had a competitive advantage. CONCLUSIONS: The nestin-cre transgenic mice can be used to generate mosaic animals in which target genes are mutated by Cre-mediated recombination of loxP-flanked target genes. By using mosaic animals, embryonic lethality can be bypassed and cell lineages for whose development a given target gene is critical can be identified. In the case of DNA polymerase beta, deficient cells are already selected against during embryonic development, demonstrating the general importance of this protein in multiple cell types.

Alleles↗
PubMedDate not supplied

Chromosome mosaicism in cleavage-stage human embryos: evidence of a maternal age effect.

The present study evaluated mosaicism in a large series of cleavage-stage human embryos analysed by fluorescence in-situ hybridization. Only embryos with at least three cells analysed were included (n = 1235), of which 556 were mosaics. The most common types of mosaicism were chaotic (48%), diploid/polyploid (26%), and those caused by mitotic non-disjunction (25%). The number of abnormal cells per embryo ranged from 44% in diploid/polyploid to 84% in chaotic mosaics. Chromosome 16 was most commonly involved in mitotic non-disjunction mosaics. While overall mosaicism did not increase with maternal age, the average maternal age of the embryos that had mosaics caused by mitotic non-disjunction was significantly higher than that for normal or other mosaic embryos (P < 0.001). During the cleavage stage, the embryonic genome is not yet fully activated and consequently the mRNA and protein pools are still similar to those found in the oocyte. We therefore propose that the malfunctioning of the meiosis apparatus, which is similar to the mitotic one, may cause either meiotic errors or mitotic non-disjunction at cleavage-stage embryo development.

Analysis of Variance↗
PubMedDate not supplied

Impact of parental gonosomal mosaicism detected in peripheral blood on preimplantation embryos.

This study evaluated the chromosomal condition of embryos generated by patients with an altered karyotype due to gonosomal mosaicism and the clinical outcome after preimplantation genetic diagnosis (PGD) for aneuploidy. Thirty-six patients aged 34.6 +/- 3.6 years performed 54 treatment cycles and had 295 embryos diagnosed by fluorescence in-situ hybridization (FISH). Thirty-seven per cent of the embryos were chromosomally normal and generated 19 clinical pregnancies after replacement in 39 cycles. Only one pregnancy miscarried, yielding a take-home baby rate of 33.3%. Autosomal monosomy and trisomy contributed 36.1% of total abnormalities and gonosomal aneuploidy 5.9%, similar to the results detected in patients who undergo PGD for increased maternal age. Reanalysis was performed on 114 non-transferrable embryos: 41 were found to be mosaics, which were grouped in three different types, chaotic mosaics (56%), aneuploid mosaics (29%) and diploid/haploid/polyploid mosaics (15%). The incidence of aneuploid mosaics was higher than expected compared with PGD patients of the same age and resembled the condition observed in patients of advanced maternal age. These findings suggest that constitutional carriers of sex chromosome mosaicism are predisposed to autosomal mosaicism of embryos, possibly due to errors of cell division. There is an indication that this tendency is higher in female than male carriers.

Adult↗
PubMed1998

Frequency of somatic and germ-line mosaicism in retinoblastoma: implications for genetic counseling.

Although mosaicism can have important implications for genetic counseling of families with hereditary disorders, information regarding the incidence of mosaicism is available for only a few genetic diseases. Here we describe an evaluation of 156 families with retinoblastoma; the initial oncogenic mutation in the retinoblastoma gene had been identified in these families. In 15 ( approximately 10%) families, we were able to document mosaicism for the initial mutation in the retinoblastoma gene, either in the proband or in one of the proband's parents. The true incidence of mosaicism in this group of 156 families is probably higher than our findings indicate; in some additional families beyond the 15 we identified, mosaicism was likely but could not be proven, because somatic or germ-line DNA from key family members was unavailable. Germ-line DNA from two mosaic fathers was analyzed: in one of these, the mutation was detected in both sperm and leukocyte DNA; in the other, the mutation was detected only in sperm DNA. Our data suggest that mosaicism is more common than is generally appreciated, especially in disorders such as retinoblastoma, in which a high proportion of cases represent new mutations. The possibility of mosaicism should always be considered during the genetic counseling of newly identified families with retinoblastoma. As demonstrated here, genetic tests of germ-line DNA can provide valuable information that is not available through analysis of somatic (leukocyte) DNA.

DNA↗
PubMedDate not supplied

Transgenic tobacco plants expressing a coat protein gene of tobacco mosaic virus are resistant to some other tobamoviruses.

Transgenic tobacco plants expressing the coat protein (CP) gene of tobacco mosaic virus were tested for resistance against infection by five other tobamoviruses sharing 45-82% homology in CP amino acid sequence with the CP of tobacco mosaic virus. The transgenic plants (CP+) showed significant delays in systemic disease development after inoculation with tomato mosaic virus or tobacco mild green mosaic virus compared to the control (CP-) plants, but showed no resistance against infection by ribgrass mosaic virus. On a transgenic local lesion host, the CP+ plants showed greatly reduced numbers of necrotic lesions compared to the CP- plants after inoculation with tomato mosaic virus, pepper mild mottle virus, tobacco mild green mosaic virus, and Odontoglossum ringspot virus but not ribgrass mosaic virus. The implications of these results are discussed in relation to the possible mechanism(s) of CP-mediated protection.

Capsid↗
PubMed1976

Prenatal diagnosis of 45,X/46,XY mosaicism with postnatal confirmation in a phenotypically normal male infant.

Prenatal detection of chromosome mosaicism has always been a diagnostic dilemma. In 21 reported cases of chromosomal mosaicism in cultured amniotic fluid cells, only two cases had cytogenetic confirmation of the mosaicism. All 21 pregnancies resulted in either phenotypically normal liveborns or grossly normal abortuses. We report a case of XO/XY mosaicism detected prenatally and confirmed postnatally in a grossly normal male infant. The indication for prenatal cytogenetic diagnosis was advanced maternal age (38 years). A diagnosis of XO/XY mosaicism was made from two separate culture flasks of amniotic fluid cells, with 45,X cells predominating (86.4%). The Y chromosome was of normal size but carried no fluorescent band. The parents were counseled and were advised that the phenotype of XO/XY mosaicism can range from relative normality to sexual maldevelopment. They decided to continue this pregnancy. The infant was born at term and was a grossly normal male with normal penis and descended, normal-sized testes. Leukocyte culture from the cord blood and a skin fibroblast culture confirmed the mosaicism of XO/XY. The father's Y chromosome was of identical size and carried a small fluorescent band. It appears that an altered Y chromosome may be predisposed to anaphase lag leading to mosaicism.

Amniotic Fluid↗
PubMed2003

Mosaic mutations of the LIS1 gene cause subcortical band heterotopia.

BACKGROUND: Subcortical band heterotopia (SBH) is a neuronal migration disorder. DCX mutations are responsible for almost all familial cases, 80% of sporadic female cases, and 25% of sporadic male cases of SBH, and are associated with more severe gyral and migration abnormality over the anterior brain regions. Somatic mosaicism has previously been hypothesized in a patient with posteriorly predominant SBH and a mutation of the LIS1 gene, which is usually mutated in patients with severe lissencephaly. The authors identified mosaic mutations of LIS1 in two patients (Patients 1 and 2) with predominantly posterior SBH. METHODS: After ruling out DCX mutations, the authors performed sequencing of the LIS1 gene in lymphocyte DNA. Because sequence peaks in both patients were suggestive of mosaic mutations, they followed up with denaturing high-pressure liquid chromatography analysis on blood and hair root DNA and compared the areas of heteroduplex and homoduplex peaks. A third patient showing the same mutation as Patient 2 but with no evidence of mosaicism was used for comparing the phenotype of mosaic vs full mutation. RESULTS: The two patients with posterior SBH harbored a missense (Arg241Pro) and a nonsense (R8X) mosaic mutation of LIS1. The rate of mosaicism in Patient 1 was 18% in the blood and 21% in the hair roots, whereas in Patient 2 it was 24% and 31% in the same tissues. The patient with a full R8X mutation of LIS1 had severe lissencephaly. CONCLUSIONS: Subcortical band heterotopia can occur with mosaic mutations of the LIS1 gene. Mutation analysis of LIS1, using highly sensitive techniques such as denaturing high-pressure liquid chromatography, should be considered for patients with posteriorly predominant subcortical band heterotopia and pachygyria.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed1994

The role of cordocentesis in assessment of mosaicism found in amniotic fluid cell culture.

Chromosomal mosaicism presents one of the most difficult problems in prenatal cytogenetic diagnosis, requiring the differentiation of true mosaicism from pseudomosaicism. To overcome associated problems and to prevent termination of normal pregnancies, we investigated 23 pregnancies in which true mosaicism has been found in amniotic fluid cell culture. A fetal blood sample was obtained by cordocentesis for rapid karyotyping, and meticulous sonographic examinations were carried out for detecting fetal abnormalities. The 23 cases in which mosaicisms were found in amniocytes involved five cases with sex chromosomal abnormalities, twelve with autosomal trisomy, four with autosomal structural defects, one with a supernumerary marker and one with tetraploidy. The karyotype from fetal leukocytes confirmed the diagnosis of mosaicism in only three out of 23 cases. These three included: two autosomal trisomies (47,XY + 13/47,XY + 21 and 46,XY/47,XY + 21) and one sex chromosome mosaicism (45,X/46,XY). These were all selected for elective termination of pregnancies by the parents' request. Post abortion karyotype re-confirmed previous karyotype. The other twenty lymphocyte karyotypes were normal, and of these, 19 patients gave birth at term, and one delivered prematurely due to premature rupture of membranes. All 20 born infants were found normal by both neonatal examination and re-karyotypes. We conclude that finding of mosaicism in amniotic fluid culture requires further investigation. Furthermore, in the presence of amniotic fluid cell true mosaicism and normal karyotype in fetal blood, continuation of the pregnancy is safe and to be recommended.

Abortion, Therapeutic↗
PubMed2002

[Mosaic phenotypes].

1) Mosaicism results from the mutation in part of somatic cells after the fertilization, only a few cases occur due to mutation during meiosis. Mosaicism is characterized by genetic or functional difference of two or more cell lines in one individual from one zygote. 2) Phenotypical variety is high and depends on the proportion of cell lines of individual clones. 3) Clinical prognosis of mosaic individuum is better in comparison to the full mutation in all cells. 4) The genetic prognosis of reproduction in relatives of the mosaic individuum is without increased recurrent risk, genetic prognosis of own offspring depends on the moment of mutation occurrence--wheit occurs before day 16 to 20 when gonadal cells are differentiated, it represents high risk of transmission. 5) Diagnosis of mixoploids in some cases requests investigation of different cells (fibroblasts, lymphocytes). 6) Clinical "signal" features of the mosaic are hemihypertrophy, asymmetry, Blaschko lines, pigmentations. 7) Risk of malignant tumor is increased, similarly to other chromosomal aberrations, chromosomal instability or hamartomatoses. 8) Mosaics of gene mutation have usually normal mental development and are manifested by external abnormalities only. 9) Incidence of mosaic phenotypes is high and therefore the diagnosis of mixoploids and gene mosaic is important for the estimation of clinical as well as genetic prognosis.

Abnormalities, Multiple↗
PubMed2006

Konjak mosaic virus: the complete nucleotide sequence of the genomic RNA and its comparison with other potyviruses.

Konjak mosaic virus (KoMV) belongs to the genus Potyvirus, family Potyviridae. The complete nucleotide sequence of KoMV F isolate (KoMV F) was determined. The genome is 9,544 nucleotides long excluding the 3' terminal poly A tail and encodes a typical potyviral 350-kDa polyprotein of 3,087 amino acids. Phylogenetic analysis using known potyvirus polyproteins shows that KoMV constitutes a branch with yam mosaic virus, close to another branch including Japanese yam mosaic virus, turnip mosaic virus, scallion mosaic virus and lettuce mosaic virus. The 3' terminal 1,842 nucleotides of a different isolate of KoMV, K-2, was also determined, covering the C-terminal 292 amino acids of the nuclear inclusion protein b (NIb), coat protein (CP), and the 3' untranslated region. The amino acid sequences of the KoMV F CP and the nucleotide sequences of the KoMV F 3' untranslated region showed 92.5 and 90.5% identity to the corresponding genes of K-2, 88.7-96.8 and 92.7-94.4% to those of Zantedeschia mosaic virus (ZaMV) isolates, 87.5-89.7% and 85.5-90.3% to those of Japanese hornwort mosaic virus (JHMV) isolates. These results showed that KoMV is a distinct potyvirus and that KoMV, ZaMV, and JHMV are members of the same potyvirus species. Considering that KoMV was the first of these to be described, ZaMV and JHMV may be considered isolates of KoMV.

Amorphophallus↗
PubMed1998

The mosaic bioprosthesis in the aortic position: hemodynamic performance after 2 years.

BACKGROUND: The Mosaic bioprosthesis is a porcine valve combining several new features to improve hemodynamics and durability: a low profile stent for reduced flow obstruction, zero pressure fixation to maintain the natural collagen crimp, and the amino oleic acid antimineralization treatment to enhance durability. METHODS: Fifty-five Mosaic valves were implanted in the aortic position since February 1994. Data from these patients (group 1) were compared with data from 52 patients who had received a Hancock Modified Orifice II aortic valve (group 2). The mean patient age was 72.0 (+/-5.9) years for group 1 and 76.8 (+/-4.7) years for group 2. Clinical examinations including transthoracic echocardiography were performed 6 and 24 months postoperatively. RESULTS: Mild aortic insufficiencies were found in 2 patients in group 1 and in 3 patients in group 2. There were no embolic or bleeding complications. One Mosaic patient required reoperation due to mitral insufficiency. During the reoperation, a small (approximately 3 mm) thrombus was noted on the outflow side of a Mosaic cusp. The valve was removed and replaced prophylactically. In the 2-year follow-up, hemodynamic measurements showed mean pressure gradients of 12.4 mm Hg for the 21 mm, 11.3 mm Hg for the 23 mm, and 15.4 mm Hg for the 25 mm prostheses in the Hancock group. In the Mosaic group, mean pressure gradients were 14.8 mm Hg for the 21 mm, 10.9 mm Hg for the 23 mm, and 11.5 mm Hg for the 25 mm valves. Differences between pressure gradients and effective orifice areas of the Hancock and the Mosaic valves were not statistically significant. Early mortality in group 1 was 3.6% and in group 2 3.8%. Overall mortality was 12.7% and 13.5%, respectively. CONCLUSIONS: The Mosaic valve has low pressure gradients for all sewing ring diameters. Compared with the Hancock Modified Orifice valve, there was no statistically significant gradient difference but a tendency toward better hemodynamics was noted in the Mosaic group after 2 years.

Aged↗