Task force 4: organization of delivery systems for adults with congenital heart disease.
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Biomedical subjects
Publications and source records attributed to J A Jarcho.
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We report the case of a 69-year-old man who had a mixed tumor (pleomorphic adenoma) removed from his parotid gland 3 years after orthotopic heart transplantation. Two years later, he presented with widely metastatic mixed tumor, which resulted in his death within 6 months. Metastatic mixed tumor is histologically identical to a benign mixed tumor, but it inexplicably metastasizes. Such tumors are rare and have not been reported to date in a transplant recipient. This case illustrates the rapid and aggressive course that malignancies can follow in an immunosuppressed population. Mixed tumors are common salivary neoplasms, so transplant recipients should be carefully followed after resection for evidence of metastatic spread.
Familial hypertrophic cardiomyopathy (FHC) is an autosomal dominant disorder manifesting as cardiac hypertrophy with myocyte disarray and an increased risk of sudden death. Mutations in five different loci cause FHC and 3 disease genes have been identified: beta cardiac myosin heavy chain, alpha tropomyosin and cardiac troponin T. Because these genes encode contractile proteins, other FHC loci are predicted also to encode sarcomere components. Two further FHC loci have been mapped to chromosomes 11p13-q13 (CMH4, ref. 6) and 7q3 (ref. 7). The gene encoding the cardiac isoform of myosin binding protein-C (cardiac MyBP-C) has recently been assigned to chromosome 11p11.2 and proposed as a candidate FHC gene. Cardiac MyBP-C is arrayed transversely in sarcomere A-bands and binds myosin heavy chain in thick filaments and titin in elastic filaments. Phosphorylation of MyBP-C appears to modulate contraction. We report that cardiac MyBP-C is genetically linked to CMH4 and demonstrate a splice donor mutation in one family with FHC and a duplication mutation in a second. Both mutations are predicted to disrupt the high affinity, C-terminal, myosin-binding domain of cardiac MyBP-C. These findings define cardiac MyBP-C mutations as the cause of FHC on chromosome 11p and reaffirm that FHC is a disease of the sarcomere.
BACKGROUND: Ribonuclease (RNase) protection has been used to identify beta-cardiac myosin heavy chain (MHC) gene mutations that cause familial hypertrophic cardiomyopathy (FHC). Since more than 10 different mutations within this gene have been demonstrated to cause FHC in unrelated individuals, the genetic diagnosis of this condition will involve screening the beta-MHC gene. The accuracy with which RNase protection identifies such mutations is critical to defining the utility of this methodology in detecting mutations that cause FHC. METHODS AND RESULTS: Twelve unrelated individuals with FHC were selected for further study because their beta-MHC genes had been screened for mutations by use of RNase protection, and no mutation was found. We performed linkage analysis of the families of these 12 probands using polymorphic short tandem repeats within the beta-MHC gene to determine whether FHC was genetically linked to the MHC locus on chromosome 14. FHC was not genetically linked to the MHC locus in 11 families whose beta-cardiac MHC gene did not contain mutations detectable by RNase protection. CONCLUSIONS: We conclude that RNase protection is a sensitive method for screening for mutations within the beta-cardiac MHC gene. Further, mutations in the noncoding regions of the beta-MHC gene and mutations in the alpha-cardiac MHC gene are not a common cause of FHC. Negative RNase protection assays of affected individuals suggest that their FHC is due to mutations at other loci.
BACKGROUND: Acute rejection may be suspected in heart transplant recipients in the setting of new onset of clinical symptoms or alterations in cardiac function. Immediate diagnosis may be obtained by performing a frozen section on endomyocardial biopsy (EMB) specimens. However, little is known about the indications for, and the diagnostic reliability of, this procedure. METHODS AND RESULTS: EMBs with frozen section (n = 98) from 65 of 214 consecutive orthotopic heart transplant recipients were reviewed and divided into early (< or = 45 days; n = 47) and late (> 45 days; n = 51) posttransplant periods. Frozen section diagnoses (means = 1.5 EMB samples) were compared with corresponding permanent section diagnoses (means = 4.4 EMB samples), and clinical indications were analyzed. Comparison of frozen and permanent section interpretation revealed concordant pathological processes-rejection (n = 31) versus no rejection (n = 37) versus ischemic injury (n = 20)-in 88 of 98 (90%) cases. Discordant pathological processes on frozen versus permanent section in 10 of 98 (10%) cases could be attributed to ischemic injury (n = 5), sampling (n = 4), and infection (n = 1). In the 92 cases with defined clinical indications, the indication and number of EMBs positive for rejection early and late after transplantation were arrhythmia: 2 of 12 early, 4 of 10 late; congestive heart failure: 1 of 2 early, 5 of 12 late; fever: 0 of 2 early, 1 of 4 late; echo abnormality: 0 of 5 early, 0 of 1 late; syncope: 1 of 5 early, 0 of 1 late; hypotension: 1 of 3 early, 1 of 2 late; noncompliance: 0 of 0 early, 4 of 5 late; more than one of the above: 3 of 7 early, 2 of 5 late; other: 1 of 7 early, 1 of 9 late; total: 9 of 43 early, 18 of 49 late. CONCLUSIONS: Frozen section on EMB specimens accurately reflected the permanent section diagnosis in 90% of cases. No specific clinical indication predicted EMB rejection positivity with high sensitivity in either the early or late posttransplant periods.
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An alpha/beta cardiac myosin heavy chain (MHC) hybrid gene is coinherited with familial hypertrophic cardiomyopathy (FHC) in one kindred. FHC is a disease of the heart muscle characterized by a thickening of the left ventricular wall with myocyte and myofibrillar disarray that is inherited as an autosomal dominant trait. We demonstrate here and in the accompanying article that the cardiac MHC genes, which encode integral myofibrillar components, are mutated in all affected individuals from two unrelated families with FHC. In one kindred, an unequal crossover event during meiosis may have produced the alpha/beta cardiac MHC hybrid gene that is present in affected individuals. We conclude that mutations in the cardiac MHC genes can cause FHC.
We demonstrate that familial hypertrophic cardiomyopathy (FHC), an autosomal dominant disorder of heart muscle, is a genetically heterogeneous disease. The locus responsible for FHC in members of one large kindred was recently mapped to chromosome 14q11-12 (FHC-1). We have characterized three additional unrelated families in which the gene for FHC segregates as an autosomal dominant trait to determine if these disease loci also map to FHC-1. All family members were clinically studied by physical examination, electrocardiogram, and two-dimensional echocardiography. Genetic studies were performed using DNA probes which are derived from loci that are closely linked to FHC-1. In one family the genetic defect maps to the previously identified FHC-1 locus. However, the loci responsible for FHC in two other families were not linked to FHC-1. We conclude that FHC can be caused by defects in at least two loci and is a genetically heterogeneous disorder.
We report that a gene responsible for familial hypertrophic cardiomyopathy (HC) is closely linked to the cardiac alpha and beta myosin heavy chain (MHC) genes on chromosome 14q11. We have recently shown that probe CRI-L436, derived from the anonymous DNA locus D14S26, detects a polymorphic restriction fragment that segregates with familial HC in affected members of a large Canadian family. Using chromosomal in situ hybridization, we have mapped CRI-L436 to chromosome 14 at q11-q12. Because the cardiac MHC genes also map to this chromosomal band, we have determined the genetic distances between the cardiac beta MHC gene, D14S26, and the familial HC locus. Data presented here show that these three loci are linked within 5 centimorgans on chromosome 14 at q11-q12. The possibility that defects in either the cardiac alpha or beta MHC genes are responsible for familial HC is discussed.
To identify the chromosomal location of a gene responsible for familial hypertrophic cardiomyopathy, we used clinical and molecular genetic techniques to evaluate the members of a large kindred. Twenty surviving and 24 deceased family members had hypertrophic cardiomyopathy; 58 surviving members were unaffected. Genetic-linkage analyses were performed with polymorphic DNA loci dispersed throughout the entire genome, to identify a locus that was inherited with hypertrophic cardiomyopathy in family members. The significance of the linkage detected between the disease locus and polymorphic loci was assessed by calculating a lod score (the logarithm of the probability of observing coinheritance of two loci, assuming that they are genetically linked, divided by the probability of detecting coinheritance if they are unlinked). A DNA locus (D14S26), previously mapped to chromosome 14 and of unknown function, was found to be coinherited with the disease in this family. No instances of recombination were observed between the locus for familial hypertrophic cardiomyopathy and D14S26, yielding a lod score of +9.37 (theta = 0). These data indicate that in this kindred, the odds are greater than 2,000,000,000:1 that the gene responsible for familial hypertrophic cardiomyopathy is located on chromosome 14 (band q1).
Nucleotide sequences necessary to direct transcription of the gene encoding atrial natriuretic factor (ANF) in neonatal and fetal hearts have been defined by using expression of the prokaryotic marker gene chloramphenicol acetyltransferase (CAT) as a functional assay. Hybrid ANF-CAT genes were introduced into primary cultured cardiocytes by electroporation. A 3.4-kilobase (kb) fragment containing sequences on the 5' side of the ANF gene promoted significant CAT activity in atrial but not ventricular cardiocytes derived from 1-day-old rats. Deletion analysis of putative regulatory regions demonstrated that 2.4 kb of 5' ANF sequences were sufficient for high-level atrial transcription, whereas hybrid genes containing less than 700 base pairs of ANF sequences promoted less CAT activity. Cardiocytes derived from embryonic ventricles expressed the 3.4-kb ANF-CAT hybrid gene at levels comparable to atrial cells, suggesting that the nucleotide sequences controlling developmental regulation of ANF expression are contained in this 5' region. Nucleotide sequence analysis of this 3.6-kb region identified segments that may contribute to the regulated expression of the ANF gene.
Progressive multifocal leukoencephalopathy (PML), a subacute and usually fatal demyelinating disease of the brain, is caused by an opportunistic viral infection in immunocompromised patients. Only one case of PML after heart transplantation has been reported; it was discovered at the autopsy of a patient who died of multiorgan system failure. We describe an otherwise asymptomatic heart transplant recipient who had neurologic complaints that could be specifically attributed to PML, demonstrate the pertinent pathologic findings, and review the PML literature germane to heart transplantation. PML may become more prevalent as the population of heart transplant recipients increases.