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Biomedical subjects

R J Lee

Publications and source records attributed to R J Lee.

At least 145 records · Page 8Linked to original sources
PubMed1994

New algorithm for the localization of accessory atrioventricular connections using a baseline electrocardiogram.

OBJECTIVES: In this study, we propose a new algorithm for accessory atrioventricular pathway localization using a 12-lead electrocardiogram (ECG). BACKGROUND: Radiofrequency catheter ablation produces a very discrete lesion, and ECG localization based on surgical dissection is obsolete. METHODS: Stepwise discriminant analysis was used to assess the relation of 18 pre-excited ECG (QRS duration > 100 ms) variables to the site of successful ablation in 93 patients. The most discriminating variables were combined to form rules for each location. The ECGs were retested by these rules to determine predictive accuracy. RESULTS: If the precordial QRS transition was at or before lead V1, the pathway had been ablated on the left side. If it was after lead V2, the pathway had been ablated on the right side. If the QRS transition was between leads V1 and V2 or at lead V2, then if the R wave amplitude in lead I was greater than the S wave by > or = 1.0 mV, it was right-sided; otherwise, it was left-sided (p < 0.0001, sensitivity 100%, specificity 97%). Right-side pathways. If the QRS transition was between leads V2 and V3, the pathway was right septal; if after lead V4, it was right lateral. If it was between leads V3 and V4, then if the delta wave amplitude in lead II was > or = 1.0 mV, it was right septal; otherwise, it was right lateral (p < 0.0001, sensitivity 97%, specificity 95%). In right lateral locations, if the delta wave frontal axis was > or = 0 degrees, or if it was < 0 degrees but the R wave amplitude in lead III was > or = 0 mV, it was anterolateral; otherwise, it was posterolateral (p < 0.0001, sensitivity 100%, specificity 87.3%). Anteroseptal pathways had a sum of delta wave polarities in leads II, III and aVF > or = +2(p < 0.0001, sensitivity 100%, specificity 100%). Posteroseptal pathways (inferior delta wave sum < or = -2) were less well discriminated from right midseptal pathways (inferior delta wave sum < or = 1 > or = -1) (p < 0.0001, sensitivity 76.5%, specificity 71%) [corrected]. Left-sided pathways. Two or more positive delta waves in the inferior leads or the presence of an S wave amplitude in lead aVL greater than the R wave, or both, discriminated left anterolateral pathways from posterior pathways (p < 0.001, sensitivity and specificity 100%). If the R wave in lead I was greater than the S wave by > or = 0.8 mV, and the sum of inferior delta wave polarities was negative, the location was posteroseptal; otherwise, it was posterolateral (p < 0.05, sensitivity 71.4%, specificity 100%). CONCLUSIONS: Using the algorithm derived, a right-sided accessory pathway can be reliably distinguished from one that is left-sided, right free wall from right septal, right anterolateral from posterolateral and anteroseptal from other right septal pathways. Left anterolateral pathways can be distinguished from left posterior pathways and left posterolateral pathways from left posteroseptal pathways.

Algorithms↗
PubMed1994

An audit of occupational medicine consultation records.

There is a need to develop and test methods of audit of the consultation process in occupational medicine and to draw conclusions from the findings. An external audit was carried out on 313 randomly selected consultation records from the occupational health services of three health boards over a 26-month period. Additionally, nine months after the date of the first externally audited sample, a prospective internal audit was commenced within one board. In 58 of the consultations selected (19 per cent), audit was not possible mainly because records could not be found. In an appreciable proportion of the rest, there were shortcomings in the referral record or in the consultation record. The consultation records of 'career' occupational physicians were better than those of 'non-career' physicians, especially in recording specific diagnoses (91 per cent vs. 67 per cent; P < 0.0001) and in conclusions regarding occupational implications (86 per cent vs. 74 per cent; P < 0.0001). Multivariate regressions showed a highly significant improvement associated with prospective internal audit in one item, namely the record of occupational implications. However, the magnitude of this difference before and after audit was smaller than the independent difference arising from the career status of the physicians. The value of medical audit in improving quality of care and education in occupational medicine is discussed.

Adult↗
PubMed1994

The nature of the epithelium in acquired cholesteatoma: Part 3--Cytokeratin patterns in aural epithelial and cholesteatoma cells grown in cell culture.

The nature and origin of the epithelial layers in acquired cholesteatoma is still unclear. Although previous morphological studies comparing external meatal and cholesteatoma epithelium have shown no significant difference, bone resorption is generally much more severe with cholesteatoma than with chronic otitis media without cholesteatoma. It is possible that cholesteatoma epithelium has undergone transformation leading to its enhanced bone destroying role. In this study the cytokeratin patterns of aural and cholesteatoma epithelia grown in cell culture were compared using monoclonal antibodies. No significant difference in staining patterns were found suggesting that there has been no change in cell phenotype which maintains that of external auditory meatus epithelium. This study therefore supports the immigration theory of cholesteatoma genesis.

Antibodies, Monoclonal↗
PubMed1994

Radiofrequency catheter ablation of atrial arrhythmias. Results and mechanisms.

BACKGROUND: Radio frequency catheter ablation is accepted therapy for patients with paroxysmal supraventricular tachycardia and has a low rate of complications. For patients with atrial arrhythmias, catheter ablation of the His bundle has been an option when drugs fail or produce untoward side effects. Although preventing rapid ventricular response, this procedure requires a permanent pacemaker and does not restore the atrium to normal rhythm. Therefore, we evaluated the safety and efficacy of radiofrequency ablation directed at the atrial substrate. METHODS AND RESULTS: Thirty-seven patients with 42 atrial arrhythmias (mean +/- SD age, 41 +/- 24 years) who had failed a median of three drugs were enrolled. Diagnoses were automatic atrial tachycardia in 12, atypical atrial flutter in 1, typical atrial flutter in 18, reentrant atrial tachycardia in 8, and sinus node reentry in 3 patients. Sites for atrial flutter ablation were based on anatomic barriers in the floor of the right atrium. For automatic atrial tachycardia, the site of earliest activation before the P wave was sought. All with reentrant atrial tachycardia had previous surgery for congenital heart disease and reentry around a surgical scar, anatomic defect, or atriotomy incision and our goal was to identify a site of early activation in a zone of slow conduction. At target sites, 20 to 50 W of radiofrequency energy was delivered during tachycardia between the 4- or 5-mm catheter tip and a skin patch, except in 4 patients with atrial flutter, in whom a catheter with a 10-mm thermistor-embedded tip was used. Procedure end point was inability to reinduce tachycardia. Acute success was achieved in 11 of 12 (92%) with automatic atrial tachycardia, 17 of 18 (94%) with typical atrial flutter, 7 of 8 (88%) with reentrant atrial tachycardia, and 3 of 3 (100%) with sinus node reentry but not in the patient with atypical atrial flutter. For tachycardia involving reentry (reentrant atrial tachycardia and atrial flutter), successful ablation required severing an isthmus of slow conduction. For those with atrial flutter, this was between the tricuspid annulus and the coronary sinus os (10) or posterior (4) or posterolateral (3) between the inferior vena cava (2) or an atriotomy scar (1) and the tricuspid annulus. Deep venous thrombosis occurred in 1 patient. At mean follow-up of 290 +/- 40 days, the ablated arrhythmia recurred in 1 (9%) with automatic atrial tachycardia, 5 (29%) with atrial flutter, and 1 (14%) with reentrant atrial tachycardia, all of whom had successful repeat ablation. Previously undetected arrhythmias occurred in 2 patients who are either asymptomatic or controlled with medication. CONCLUSIONS: Ablation of automatic and reentrant atrial tachycardia and atrial flutter had a high success rate and caused no complications from energy application. Repeat procedures may be required for long-term success, especially in patients with atrial flutter. The mechanism by which ablation is successful is similar for atrial flutter and other forms of atrial reentry and involves severing a critical isthmus of slow conduction bounded by anatomic or structural obstacles. Automatic arrhythmias are abolished by directing lesions at the focus of abnormal impulse formation.

Adult↗
PubMed1994

Electrophysiological laboratory, electrophysiologist-implanted, nonthoracotomy-implantable cardioverter/defibrillators.

BACKGROUND: Implantable cardioverter/defibrillators (ICDs) have conventionally been implanted in the operating room by surgeons. However, technological developments have reduced size and increased simplicity, bringing the procedure into the realm of the electrophysiologist. The purpose of this study was to evaluate the safety and efficacy of implantation of the entire ICD system by electrophysiologists in an electrophysiology laboratory. METHODS AND RESULTS: Between July 1993 and February 1994, 23 patients (21 men; age, 64 +/- 11 years) underwent transvenous ICD implantation by electrophysiologists working alone, entirely in the electrophysiology laboratory. Indications for ICD were sudden death in 10 patients, uncontrolled life-threatening ventricular tachycardia in 12, and syncope with cardiomyopathy and familial sudden death in 1. Seventeen patients had coronary artery disease and a past history of acute myocardial infarction. Four patients had idiopathic dilated cardiomyopathy, 1 had coronary ectasia and poor left ventricular function, and another had poor left ventricular function related to valvular dysfunction. The mean left ventricular ejection fraction was 34 +/- 10% (range, 20% to 50%). General anesthesia was administered in 22 cases, and deep sedation was used in 1 elderly patient. After positioning of transvenous leads and subcutaneous patch/array lead positioning, defibrillation testing was performed. After transvenous and subcutaneous lead tunneling, all generators were placed subcutaneously in an abdominal pocket. The mean total time in the electrophysiology laboratory was 254 +/- 68 minutes (range, 150 to 375 minutes), with 104 +/- 42 minutes for anesthetic and other preparation, 159 +/- 45 minutes for implantation, and 8.7 +/- 5 minutes (range, 3 to 25 minutes) of fluoroscopy required for positioning of transvenous and subcutaneous lead systems. Implant times showed a significant improvement when the first 10 cases (188 +/- 44 minutes) were compared with the last 10 in the series (124 +/- 44 minutes, P < .01). The mean defibrillation threshold was 17 +/- 5 J (range, 5 to 25 J). There were 5 complications (22%): 1 patch-site hematoma, 1 pneumothorax related to subclavian venous puncture, 1 pulmonary embolism, and 2 patients requiring overnight ventilation after hemodynamic deterioration following defibrillation testing. There were no deaths, and there were no infections. The mean time to hospital discharge after the implant was 5.1 +/- 3.5 days. After 11.6 +/- 9 weeks of follow-up, all devices were functioning satisfactorily, all patients had successfully defibrillated at postimplant predischarge checkup with 29 +/- 5 J, and there had been no late complications. CONCLUSIONS: This is the first report to show that nonthoracotomy ICD implantation may be successfully carried out by electrophysiologists working alone in the electrophysiology laboratory, with a high rate of success and few complications, even in high-risk patients. This high rate of success and safety probably relates to the availability of high-quality fluoroscopy and familiarity with electrophysiology laboratory equipment and personnel.

Adult↗
PubMed1994

Radiofrequency catheter ablation of atriofascicular and nodoventricular Mahaim tracts.

BACKGROUND: Several mechanisms have been proposed to explain the pathogenesis of tachycardia in patients with Mahaim tracts. The tachycardia may involve antegrade conduction over an atriofascicular pathway with decremental properties or a nodofascicular pathway. METHODS AND RESULTS: We report six patients with recurrent episodes of preexcited tachycardia with findings consistent with "Mahaim tract" conduction. All patients exhibited decremental antegrade preexcited conduction with atrial pacing and a preexcited tachycardia with initial activation of the proximal right bundle branch. In four patients (group 1), atrial premature complexes (APCs) induced at the tricuspid annulus just after the inscription of the septal atrial electrogram and during left bundle branch block preexcited tachycardia advanced the next preexcited ventricular complex. In these patients, discrete Mahaim potentials were inscribed over the right anterolateral or lateral tricuspid annulus. Two patients (group 2) had evidence of dual atrioventricular nodal conduction. APCs during left bundle branch block tachycardia just after inscription of the septal atrial electrogram failed to advance the next ventricular complex with similar preexcited morphology, and no Mahaim potentials could be recorded from the tricuspid annulus. In group 1 patients, application of radiofrequency energy to sites recording the Mahaim potentials resulted in tachycardia cure. For patients in group 2, selective slow atrioventricular nodal pathway ablation in the midseptal region resulted in complete ablation of both the slow atrioventricular nodal pathway and Mahaim conduction in two patients. CONCLUSIONS: Mahaim tachycardia can be due to atriofascicular pathways, which may be ablated over the right tricuspid annulus, or to septal pathways, which may arise from the slow atrioventricular nodal pathway in patients with dual atrioventricular nodal physiology. In the latter circumstance, successful ablation is achieved by placing the lesion in the midseptal region.

Adult↗
PubMed1994

Molecular genetic truncation analysis of filament assembly and phosphorylation domains of Dictyostelium myosin heavy chain.

Conventional myosin ('myosin II') is a major component of the cytoskeleton in a wide variety of eukaryotic cells, ranging from lower amoebae to mammalian fibroblasts and neutrophils. Gene targeting technologies available in the Dictyostelium discoideum system have provided the first genetic proof that this molecular motor protein is essential for normal cytokinesis, capping of cell surface receptors, normal chemotactic cell locomotion and morphogenetic shape changes during development. Although the roles of myosin in a variety of cell functions are becoming clear, the mechanisms that regulate myosin assembly into functional bipolar filaments within cells are poorly understood. Dictyostelium is currently the only system where mutant forms of myosin can be engineered in vitro, then expressed in their native context in cells that are devoid of the wild-type isoform. We have utilized this technology in combination with nested truncation and deletion analysis to map domains of the myosin tail necessary for in vivo and in vitro filament assembly, and for normal myosin heavy chain (MHC) phosphorylation. This analysis defines a region of 35 amino acids within the tail that is critical for filament formation both for purified myosin molecules and for myosin within the in vivo setting. Phosphorylation analysis of these mutants in intact cytoskeletons demonstrates that the carboxy-terminal tip of the myosin heavy chain is required for complete phosphorylation of the myosin tail.

Animals↗
PubMed1994

Consultation patterns in a community survey of men with benign prostatic hyperplasia.

BACKGROUND: The Stirling benign prostatic hyperplasia natural history group have previously reported a prevalence of this condition of 255 per 1000 in a community study of 1610 men aged 40-79 years. AIM: It was decided to examine the consultation patterns of men with benign prostatic hyperplasia in greater detail. METHOD: All participating men were invited to complete a previously validated lifestyle questionnaire including questions on consultations with their general practitioner during the previous year and previous history of prostatic problems. The men who had a urinary symptom score greater than 11, or who had a urinary flow rate of less than 15 ml per second were examined by transurethral ultrasonography for prostate size. RESULTS: Of 364 men with benign prostatic hyperplasia, 89% had not consulted their doctor about urinary symptoms in the year prior to the study. Men with moderate to severe urinary symptoms were six times more likely to have consulted their doctor than those with mild symptoms. Moderate to severe symptoms and greater interference with daily living activities were both associated with a greater likelihood of consultation, independent of age. Of all the men in the study referred to the specialist clinic for assessment of prostate size by transurethral ultrasonography, two thirds were referred because of low urinary flow rate and one third because of high urinary symptom scores. The reported consultation data showed a reverse ratio of one third of those consulting having a low urinary flow rate and approximately two thirds having urinary symptoms. CONCLUSION: While mass screening is unjustified, there is a need for patient education about benign prostatic hyperplasia in general and the recognition of declining strength of urinary flow as a symptom of benign prostatic hyperplasia and not of ageing alone. Furthermore, evaluation of primary care use of urinary flowmeters and the development of local protocols are suggested as elements of a case finding strategy for benign prostatic hyperplasia based on patient led consultation.

Adult↗
PubMed1993

Dictyostelium myosin heavy chain phosphorylation sites regulate myosin filament assembly and localization in vivo.

Three threonine residues in the tail region of Dictyostelium myosin II heavy chain have been implicated previously in control of myosin filament formation. Here we report the in vitro and in vivo consequences of converting these sites to alanine residues, which eliminates phosphorylation at these positions, or to aspartate residues, which mimics the negative charge state of the phosphorylated molecule. Alanine substitution allows in vitro assembly and in vivo contractile activity, although this myosin shows substantial over-assembly in vivo. Aspartate substitution eliminates filament assembly in vitro and renders the myosin unable to drive any tested contractile event in vivo. These results demonstrate that heavy chain phosphorylation plays a key modulatory role in controlling myosin function in vivo.

Actin Cytoskeleton↗
PubMed1993

Similar levels of urological symptoms have similar impact on Scottish and American men--although Scots report less symptoms.

Urinary symptoms and the extent to which they interfere with living activities were compared in 2 community-based investigations that enrolled men 40 to 79 years old who were randomly sampled from Olmsted County, Minnesota (2,119) and the Forth Valley of Scotland (1,385). Both investigations included symptom questions with wording that is nearly identical to that of the American Urological Association (AUA) symptom index. Following AUA scoring conventions we grouped scores into mild (AUA score 0 to 7), moderate (score 8 to 19) and severe (score 20+) categories. Minnesota men had symptoms that were more frequent, more bothersome and caused greater interference with living activities than did Scottish men of comparable age (p < 0.0002). However, within each symptom score category, the extent to which symptoms interfered with living activities was essentially the same in both populations. Although there appear to be important differences in urinary symptom prevalence between Scotland and Minnesota, the AUA symptom index provides a consistent measure of the extent to which urinary symptoms interfere with living activities in both populations. These findings support use of the AUA symptom index in the diagnostic evaluation of men with benign prostatic hyperplasia.

Adult↗
PubMed1993

The importance of width in asbestos fiber carcinogenicity and its implications for public policy.

Evidence from human epidemiology, experimental animal implantation and inoculation studies, and lung burden studies show that fibers with widths greater than 1 micron are not implicated in the occurrence of lung cancer or mesothelioma. Furthermore, it is generally believed that certain fibers thinner than a few tenths of a micrometer must be abundant in a fiber population in order for them to be a causative agent for mesothelioma. These conclusions are fully consistent with the mineralogical characteristics of asbestos fibers, which, as fibrils, have widths of less than 1 micron and, as bundles, easily dissagregate into fibrils. Furthermore, the biological behavior of various habits of tremolite shows a clear dose-response relationship and provides evidence for a threshold between fiber width and tumor experience in animals. Public policy in regulating mineral fibers should incorporate this knowledge by altering the existing federal asbestos fiber definitions to reflect it.

Animals↗
PubMed1993

Occupational physicians and their work: prospects for audit.

An anonymous postal questionnaire was sent to 200 occupational physicians in the UK to determine their activities, the nature of the organizations within which they work and their attitudes and practices with respect to audit. One hundred and sixty-six physicians responded to the questionnaire, of whom 119 (72 per cent) were currently practising occupational medicine. Fifty-seven (48 per cent) of these 119 were engaged in some form of audit but only 21 (18 per cent) were engaged in an audit of structure, process and outcome. Assessment of continuing fitness for work or sickness absence ranked first overall with respect to the proportion of the physician's time engaged. The study revealed a wide diversity in the organization of the practice of occupational medicine, in the qualifications of occupational physicians and in their participation in audit. Needs for the development and wider implementation of methods of audit in occupational medicine have been identified by the study.

Humans↗
PubMed1993

Relationship between prostate specific antigen, prostate volume and age in the benign prostate.

The relationship between prostate specific antigen (PSA) levels, prostate volume and age was examined in 472 men who underwent PSA assay (Hybritech), digital rectal examination (DRE) and transrectal ultrasound (TRUS) as part of a community survey of benign prostatic hyperplasia following exclusion of men with prostate cancer. The mean age of the study population was 60 years (range 40-79). The mean PSA was 2.4 ng/ml and 85% of the men had levels < 4 ng/ml. There was a modest correlation between PSA and both age and prostate volume. The mean prostate and adenoma volumes were 32 ml (SD 13.4) and 15 ml (SD 10.7) respectively. Prostate volume increased with age. Linear regression analysis revealed an independent association between PSA and age when controlling for volume. The mean ratio of PSA per unit of prostate volume was 0.072 ng/ml. This ratio also increased with age. Age and prostate volume influences PSA levels independently. The sensitivity and specificity of PSA adjusted for volume and age in the diagnosis of prostate cancer need to be evaluated in association with DRE and TRUS.

Adult↗
PubMed1993

Ultrasonically determined patterns of enlargement in benign prostatic hyperplasia.

A series of 430 men aged 40 to 79 years underwent transrectal ultrasonography (TRUS) as part of a community survey of benign prostatic hyperplasia (BPH). We describe a reproducible method of prostate volume estimation and discuss the implications of prostate dimension changes in BPH. The mean prostate and adenoma volumes for the group were 32 ml (SD 14) and 15 ml (SD 11) respectively. The antero-posterior dimension of the prostate (APD) had the strongest correlation with gland volume compared with the transverse dimension (TD) and length (L). The mean ratio of adenoma volume to prostate volume was 0.45 (SD 0.13) and this increased with increasing gland volume. There was a modest correlation between the ratio and prostate volume. BPH is characterised by a proportionally greater increase in the APD compared with L and TD and by an increasing adenoma/prostate ratio. TRUS is useful in assessing the type and extent of adenoma and prostate enlargement in BPH.

Adult↗
PubMed1993

Increased seroprevalence of hepatitis B in dental personnel necessitates awareness of revised pediatric hepatitis B vaccine recommendations.

This article presents data regarding occurrence of hepatitis B in health care workers and children living in their households. Also reviewed are recent revisions in pediatric hepatitis B vaccine recommendations. The purpose of this discussion is twofold: to provide information to assist dental personnel in the decision-making process regarding vaccination of infants, children, and adolescents in their households; and to increase knowledge to facilitate educational presentations. In the United States from 1979 to 1989 the prevalence of new acute hepatitis B cases increased by 37 percent. An estimated 1.25 million people with chronic hepatitis B are capable of infecting those within their immediate environment, including their families. Studies indicate that dental health care workers, through occupational exposure, may have a 10 times greater risk of becoming a chronic hepatitis B carrier than the average citizen. The World Health Organizations's Expanded Programme on Immunizations recommends that children receive vaccination in populations where hepatitis B is prevalent. The three-pronged approach for reducing pediatric transmission includes: (1) vaccination of infants born to infected mothers, (2) routine vaccination of children born to hepatitis-seronegative mothers, (3) identification and vaccination of specific groups of adolescents. Comprehension of these changes may increase compliance regarding vaccination of children in our household, as well as enhancing our educational presentations to patients, the community, and professional societies.

Adolescent↗
PubMed1993

Impact of previously unrecognized benign prostatic hyperplasia on the daily activities of middle-aged and elderly men.

To assess the importance of benign prostatic hyperplasia on activities of daily living, a cross-sectional survey of 1627 men aged 40-79 years (representing a 65% response rate) registered with two health centres in central Scotland was carried out, using a urinary symptom questionnaire and uroflowmetry to identify men more likely to have benign prostatic hyperplasia. The condition was defined as a prostate gland of more than 20 g in the presence of symptoms of urinary dysfunction and/or a peak flow rate of less than 15 ml s-1, without evidence of malignancy. Transrectal ultrasonography was used to measure the volume (and by inference weight) of prostate glands. A total of 410 men satisfied the criteria for benign prostatic hyperplasia. Overall, 51% of men with benign prostatic hyperplasia reported interference with at least one of a number of selected activities of daily living as a result of urinary dysfunction, compared with 28% of men who did not have this condition. In 17% of men of working age (40-64 years) with benign prostatic hyperplasia, this interference occurred most or all of the time for at least one activity of daily living compared with only 3% of men in the same age group who did not have this condition. If the criteria of unmet need for treatment of benign prostatic hyperplasia constitutes interference by urinary dysfunction most or all of the time in at least one activity of daily living, then the findings of this survey suggest that a substantial number of middle aged and elderly men living in the United Kingdom may be in need of assessment and treatment for this condition.

Activities of Daily Living↗
PubMed1993

Clinical experience with angiotensin II receptor antagonists.

The new generation of antihypertensive agents, the angiotensin II receptor antagonists, lower blood pressure by intervening in the RAA system. Angiotensin II is the major effector compound in the RAA cascade; therefore, blockade of the angiotensin II receptor represents a particularly effective way of preventing its hypertensive effects. Losartan (DuP 753, MK954) is the first of a new series of non-peptide orally-active angiotensin II receptor antagonists. Preliminary results of ongoing pharmacology and efficacy studies with losartan indicate that it may have an improved clinical profile when compared with other antihypertensive agents. The results of these studies have indicated that the effective antihypertensive dose of losartan is 50 mg once daily.

Angiotensin II↗