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Biomedical subjects

B Williamson

Publications and source records attributed to B Williamson.

At least 73 records · Page 4Linked to original sources
PubMed1993

Radiofrequency catheter ablation of atypical atrioventricular nodal reentrant tachycardia.

INTRODUCTION: Published reports of radiofrequency ablation of atypical atrioventricular nodal reentrant tachycardia (AVNRT) have been limited. We present our experience in 10 consecutive patients with atypical AVNRT who underwent radiofrequency ablation of the "slow" AV nodal pathway. METHODS AND RESULTS: There were 9 females and 1 male; their mean age was 44 +/- 19 years (+/- SD). The mean AVNRT cycle length and ventriculoatrial (VA) interval at the His position during AVNRT were 340 +/- 50 msec and 200 +/- 70 msec, respectively. The slow pathway was successfully ablated in all patients with a mean of 10 +/- 7 radiofrequency energy applications in the posteroseptal right atrium near the coronary sinus os. The mean procedure duration was 100 +/- 35 minutes. There were no complications. In 4 patients, target sites were identified during sinus rhythm by mapping for possible slow pathway potentials. In the other 6 patients, target sites were identified by mapping retrograde atrial activation during AVNRT or ventricular pacing. The VA times at successful target sites were a mean of 45 +/- 30 msec less than the VA time at the His catheter during AVNRT. There were no differences in success rate, number of radiofrequency energy applications, or procedure duration between patients in whom mapping was guided by possible slow pathway potentials or by retrograde atrial activation. During 6 +/- 3 months of follow-up, 1 patient had a recurrence of atypical AVNRT and underwent a second ablation procedure, which was successful. CONCLUSION: Radiofrequency ablation of atypical AVNRT can be safely and effectively accomplished when target sites are identified based either on possible slow pathway potentials during sinus rhythm or retrograde atrial activation times during tachycardia.

Adult↗
PubMed1992

Role of ultrasound in medical management of patients with renal stone disease.

Eighty-three patients with radiographically opaque renal stones were evaluated prospectively with ultrasound and compared to KUB (kidneys, ureters, bladder) with tomograms (KUB/T) to further define the use of ultrasound in the evaluation of renal calculi. The presence or absence and the size, number, and location of stones were analyzed and correlated for each modality. Ultrasound detected the presence of renal stones in 77 of 83 (93%) patients. However, all of the stones were detected on ultrasound in only 60% of these patients. Thirty percent (80 of 269) of the papillary-calyceal stones seen on KUB/T were missed on US; 66% of the stones missed measured 2 mm or less. Although ultrasound can be used for detection of intrarenal stones, KUB/T is a more accurate imaging examination for determination of size and number of small stones.

Adolescent↗
PubMed1992

Unstable DNA may be responsible for the incomplete penetrance of the myotonic dystrophy phenotype.

Myotonic dystrophy (DM) is associated with the expansion and instability of a trinucleotide (CTG) repeat in a sequence encoding a cAMP-dependent protein kinase. The normal copy number of 5-35 repeats is exceeded in DM patients, with the size of the expansion broadly correlating with the severity of symptoms experienced. In most families reported, the unstable DNA sequence has increased in size on transmission to affected offspring, thereby providing a molecular explanation for the phenomenon of anticipation in DM, i.e. an increase in the severity of symptoms associated with an earlier age at onset of the disease in successive generations of a family. Here we present the first reported case of a family where the transmission of the affected chromosome from father to son is accompanied by a reduction in the size of the triplet expansion, such that it falls within the normal range. As the son remains asymptomatic, this type of molecular event may provide an explanation for the incomplete penetrance of the disease phenotype reported for this disorder. The implications for genetic counselling of DM families and the mechanistic considerations of the trinucleotide instability are discussed.

Adult↗
PubMed1992

Gene therapy.

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Autoimmune Diseases↗
PubMed1992

Development of a surgical robot for cementless total hip arthroplasty.

The long-term success of cementless total hip arthroplasty (THA) may depend on bone ingrowth into the porous-fixation surfaces of the implant. The ingrowth process is facilitated when the surgeon achieves a satisfactory fit for the prosthesis. Clinically or roentgenographically visible failure and persistent thigh pain after cementless THA remain significant problems, both of which may be alleviated by more precise preparation of the femoral canal and selection of an appropriately sized prosthesis. The objective of this study was to obtain an exact fit for the prosthesis through the use of an image-directed surgical robot for femoral canal preparation.

Arthroplasty↗
PubMed1992

Attitudes towards prenatal diagnosis and carrier screening for cystic fibrosis among the parents of patients in a paediatric cystic fibrosis clinic.

The parents of all children attending the Royal Brompton National Heart and Lung Hospital cystic fibrosis paediatric clinic were asked to complete an anonymous postal questionnaire addressing attitudes towards prenatal diagnosis and population carrier screening for cystic fibrosis (CF); 65% (170/261) of parents responded. Of the respondents, 92% would support the introduction of a population screening test to detect carriers of CF and 19% felt such a test should be mandatory. A total of 64% of CF parents felt they would choose not to have any further children in the knowledge that they were both carriers, 74% would choose to have a prenatal test if they became pregnant, 44% would consider terminating an affected pregnancy, 33% would not, and 23% were unsure. Overall, 72% of respondents indicated they would choose to avoid having a further child with CF either by not having further children or by terminating an affected pregnancy.

Attitude to Health↗
PubMed1991

From linked marker to gene.

An area of increasing importance in human genetics research is the strategy of 'reverse genetics' or 'positional cloning', whereby a gene associated with a genetic disease is isolated on the basis of its approximate chromosomal position. This article and the accompanying centrepage diagram describe the main features of this strategy and outline the techniques involved; they are designed to be used for teaching purposes and as a general reference for those from other fields of genetics research.

Chromosome Mapping↗
PubMed1991

Congenital cystic disease of the seminal vesicle.

Thirteen cases of congenital seminal vesicle cysts with pathologic correlation were diagnosed between 1970 and 1988. Twelve of the 13 patients had ipsilateral renal anomalies. Intravenous urography, performed in 11 of the 13 patients, demonstrated associated renal anomalies. Computed tomography, performed in nine of the 13 patients, demonstrated associated renal anomalies and displayed the cystic seminal vesicles. Transabdominal or endorectal ultrasonography, performed in eight patients, allowed characterization of the seminal vesicle masses as cystic. Magnetic resonance imaging, performed in three of the 13 patients, accurately demonstrated dilated ejaculatory ducts into which ectopic ureters inserted. The fluid in the seminal vesicle cysts had an increased signal intensity on T1- and T2-weighted sequences. Seminal vesiculographic study demonstrated anomalous communications with the seminal tract. Cystic disease of the seminal vesicles can be either congenital or acquired; congenital cysts are associated with anomalies of the ipsilateral mesonephric duct.

Adult↗
PubMed1989

Recombination events that locate myotonic dystrophy distal to APOC2 on 19q.

We previously reported a recombination in an individual with myotonic dystrophy (DM) which placed the markers D19S19 and APOC2 on the same side of the DM locus. Haplotyping of this family with more recently characterized probes which are either tightly linked to DM or distal to the linkage group at q13.2 shows that the DM locus is distal to APOC2. This is confirmed by other recombinants where DM segregates with distal probes. Additional marker to marker recombinations in unaffected individuals are reported and support the order and orientation of the DM linkage group as pter-(INSR, LDLR,S9)-(S19,BCL3,APOC2)-(CKMM,DM)-(S22,+ ++PRKCG)-qter. The data presented here cannot determine whether DM is proximal or distal to CKMM. The consequences of this probe order for antenatal diagnosis and future research aiming to isolate the gene which is affected in DM are discussed.

Chromosome Mapping↗
PubMed1989

Low-osmolality contrast media: a current perspective.

Intravascular radiographic contrast media play a major role in diagnostic imaging. Recently, low-osmolality contrast media (LOCM) have become available in the United States. Because of their lower osmolality, these new agents cause fewer undesirable physiologic effects and fewer adverse reactions than do conventional agents after intravascular administration. Unfortunately, the cost of LOCM is substantially higher than the cost of conventional contrast media. Appropriate use of these newer, more expensive contrast agents must be based on a thorough knowledge and understanding of their chemistry, physiologic features, and relative safety. Some questions remain about these new agents. Further studies are needed to determine the nephrotoxicity of LOCM relative to that of conventional agents. In addition, LOCM have less anticoagulant capacity than do the conventional media; therefore, clotting may occur when the LOCM and blood mix in syringes and small catheters. This potential decrease in anticoagulation and its clinical implications should be further investigated. Finally, the mortality rate associated with use of LOCM needs to be determined in future studies in large numbers of patients.

Contrast Media↗
PubMed1989

Seminal vesicle imaging.

The purpose of this paper is to enhance the understanding of CT, MRI and US images of the seminal vesicles. Accurate interpretation of images requires knowledge of normal anatomy, embryology and pathology. Anatomy and a spectrum of abnormalities are reviewed and discussed. Cases are from an analysis of clinical and surgical files to show the diagnostic features of various cystic diseases of the seminal vesicles. Tissue characteristics of the seminal vesicles on CT, MRI and US images are emphasized.

Adult↗