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Biomedical subjects

R A Friedman

Publications and source records attributed to R A Friedman.

13 recordsLinked to original sources
PubMed1992

Late ventricular arrhythmia and sudden death following direct-current catheter ablation of the atrioventricular junction.

Early reports of direct-current catheter ablation (DCCA) of the atrioventricular (AV) junction for resistant AV tachycardias documented efficacy of DCCA with little morbidity. Nine patients underwent DCCA at our institution 4 to 9 years ago: 3 patients had DCCA in the coronary sinus for permanent junctional reciprocating tachycardia, 2 patients had His ablation, 2 had coronary sinus and His ablation for permanent junctional reciprocating tachycardia, and 2 had DCCA for congenital tachycardia, and 2 had DCCA for congenital junctional ectopic tachycardia. Shocks (total 1 to 5) ranged from 12.5 to 400 J. Five patients had pacemaker implant at the time of DCCA. During follow-up, 3 patients developed clinical ventricular tachycardia: all 3 had DCCA of the His bundle. One asymptomatic patient with ventricular tachycardia, who had DCCA of the bundle of His, died suddenly 6 years later with ventricular fibrillation. Autopsy revealed 2 ventricular scars: 1 extending from the AV junction and 1 in the outflow tract. No patient with DCCA limited to the coronary sinus developed ventricular tachycardia. DCCA of the His bundle can result in late ventricular arrhythmias, possibly a result of extension of the DCCA lesion into the ventricle. These late findings should be considered in evaluating the safety and efficacy and follow-up for patients undergoing radiofrequency ablation.

Atrioventricular Node↗
PubMed1992

The electrostatic contribution to DNA base-stacking interactions.

Base-stacking and phosphate-phosphate interactions in B-DNA are studied using the finite difference Poisson-Boltzmann equation. Interaction energies and dielectric constants are calculated and compared to the predictions of simple dielectric models. No extant simple dielectric model adequately describes phosphate-phosphate interactions. Electrostatic effects contribute negligibly to the sequence and conformational dependence of base-stacking interactions. Electrostatic base-stacking interactions can be adequately modeled using the Hingerty screening function. The repulsive and dispersive Lennard-Jones interactions dominate the dependence of the stacking interactions on roll, tilt, twist, and propellor. The Lennard-Jones stacking energy in ideal B-DNA is found to be essentially independent of sequence.

Base Sequence↗
PubMed1992

Transgenic mice. Current applications to the study of the auditory and vestibular systems.

Understanding the variety of genetic disorders affecting the inner ear demands that we first comprehend the molecular mechanisms involved in its development. Mechanisms of development can best be understood by the study of mutant organisms. Progress in the study of mammalian development has been hampered by the difficulty inherent in the identification and isolation of mutated genes. Transgenic technology provides a direct experimental approach to the study of the control and tissue specificity of gene expression. Additionally, this technology allows new and exciting methods of human disease modeling. A by-product of this technology is the creation of insertional mutants, which provide a unique approach toward the identification of genes involved in a variety of developmental processes including those of hearing and balance.

Animals↗
PubMed1991

Kinetic ultrasound evaluation of the posterior vitreoretinal interface.

The evaluation of the posterior vitreoretinal interface is important in the study of the natural course and preoperative evaluation of numerous disorders of the retina. The exact status of the posterior vitreous cannot always be reliably determined by ophthalmoscopic examination. The diagnostic value of kinetic contact ultrasonography was investigated to evaluate the status of the posterior vitreous in 70 eyes with clear ocular media. Contact B-scan ultrasound provided an extremely accurate method for evaluating the posterior vitreoretinal interface in 69 of the 70 eyes in this study, when compared with all conventional clinical means of examination including slit-lamp biomicroscopy with the Goldmann contact lens and fundus photography with the El Bayadi-Kajiura lens. Contact B-scan ultrasonography is an important diagnostic adjunct in determining the status of the vitreoretinal interface.

Evaluation Studies as Topic↗
PubMed1991

Clinical course of idiopathic dilated cardiomyopathy in children.

Previous studies in adults with dilated cardiomyopathy suggest that the presence of arrhythmia, especially ventricular tachycardia, correlates with increased mortality. We performed a retrospective analysis of 63 children with idiopathic dilated cardiomyopathy to determine the prognostic significance of arrhythmias and other findings with respect to mortality. The mean age at diagnosis of the cardiomyopathy was 4.96 +/- 5.3 years. The overall mortality rate was 16% over a 10 year follow-up period. Persistent congestive heart failure and ST-T wave changes correlated with increased mortality (p less than 0.05). No other variables affected outcome. Arrhythmias were found in 46% of the patients; of the arrhythmias, 48% were atrial arrhythmias. Ventricular tachycardia was present in six patients. Death occurred in 4 (14%) of 29 patients with known arrhythmia; 1 of the 5 died suddenly. The remaining 6 deaths in the series occurred in the 34 patients without a documented arrhythmia. It is concluded that 1) arrhythmias are frequently seen in children with dilated cardiomyopathy but are not predictive of outcome; 2) sudden death in children with this disease is rare; and 3) persistent congestive heart failure portends a poor prognosis.

Arrhythmias, Cardiac↗
PubMed1991

Polyelectrolyte effects on 9-aminoacridine-DNA binding.

The 9-aminoacridine-DNA binding curve is analyzed in two ways: with polyelectrolyte effects neglected and with polyelectrolyte effects included. It is found that the analysis which includes polyelectrolyte effects is consistent with the violation of neighbor exclusion displayed by diacridine complexes as observed by Atwell et al. and by Zimmerman and coworkers. However the analysis which neglects polyelectrolyte effects is inconsistent with the diacridine results. This comparison supports the necessity of including polyelectrolyte effects in the analysis of drug-DNA binding curves.

Aminacrine↗
PubMed1991

Active fixation of endocardial pacing leads: the preferred method of pediatric pacing.

Pacing system failure due to lead related problems may necessitate repositioning or explantation of the problem lead. Pediatric patients with permanent pacemakers have additional considerations that necessitate revision or explantation of pacing leads. Active fixation type leads appear to offer the physician advantages over passive fixation leads that may make them the lead of choice for use in children. We reviewed our experience with active fixation type leads to determine whether the ease with which these leads could be revised or explanted justified recommending their use in our patients. Eleven patients underwent 13 lead revisions. The time from implant to revision was a mean of 12.3 months. Six patients had previously undergone repair of a congenital heart defect. Modes of pacing were: DDD (seven); AAI (three); and VVI (one). Exposed, isodiametric leads accounted for 11/13 leads. Leads were successfully explanted in nine cases and repositioned in four cases. The only lead that could not be revised and resulted in retention was a nonisodiametric, retractable helix lead at the junction of the subclavian vein and clavicle. We conclude isodiametric active fixation leads can be safely repositioned or explanted in children and should be considered the preferred method for endocardial pacing in children.

Adolescent↗
PubMed1991

Bradycardia and syncope in children not controlled by pacing: beta-adrenergic hypersensitivity.

Cardiac pacing is frequently employed in the therapy of children with syncope and documented bradycardia. This report describes two children, ages 7 and 9 years, who underwent placement of demand ventricular pacing systems for documented bradycardia and syncope. Cardiac catheterization and intracardiac electrophysiological studies failed to show evidence of structural abnormalities, sinus node or conduction system disease, inducible arrhythmias, or VA conduction in each patient. Both patients had persistent symptoms after pacemaker implantation. Autonomic function testing with continuous heart rate and blood pressure monitoring revealed exaggerated beta-adrenergic responses to simple standing and small doses of isoproterenol. Symptoms were completely eliminated with atenolol. In these two children, cardiac pacing alone was not adequate for relief of symptoms. Autonomic mechanisms of bradycardia and hypotension should be considered prior to implantation of permanent pacing systems in children.

Adrenergic beta-Antagonists↗
PubMed1991

Sinusitis.

Paranasal sinusitis is one of the most common diseases treated in outpatient centers across the United States. Improved bacterial culture techniques have revealed the variety of pathogens involved in acute and chronic sinusitis. The growing numbers of antibiotic-resistant bacterial strains and of immunocompromised patients have changed the clinical face of sinusitis. New diagnostic modalities, including magnetic resonance imaging, are facilitating more rapid and accurate disease detection.

Humans↗
PubMed1990

Statistical issues in the identification of risk factors for suicidal behavior: the application of survival analysis.

Studies of suicide risk factors generally examine suicidal behavior as a dichotomous outcome. Survival analytic techniques are discussed in which the time until a suicide attempt from a specific point, such as prior attempt or onset of illness, is also examined. These procedures can incorporate information on those lost to followup or "censored." One survival analytic technique, Cox's proportional hazards model, is a particularly informative statistical technique for the study of suicidal risk factors because several covariates can be incorporated. Illustrative analyses estimate the significance of different risk factors, and demonstrate that there is a 32% increase in the relative risk of a suicide attempt associated with each prior attempt.

Adult↗
PubMed1989

Sulfasalazine-induced hepatotoxicity in children with inflammatory bowel disease.

A case of severe sulfasalazine-induced hepatotoxicity is reported in a 14-year-old girl with Crohn's disease. Fourteen days after beginning sulfasalazine, she developed a systemic reaction characterized by high fever, maculopapular rash, lymphadenopathy, abdominal pain, and malaise, with tender hepatomegaly and elevated liver functions, leukemoid reaction, with eosinophilia, and immune complexes. She responded promptly to high-dose intravenous steroids with complete recovery. This case was compared to the three similar pediatric cases in the literature. The latent period was 11-19 days between sulfasalazine therapy and the onset of high fever, generalized lymphadenopathy, and pruritic maculopapular rash that spared palms and soles and resolved with desquamation. All children had hepatotoxicity indicated by tender hepatomegaly, elevated liver enzymes, and histologic inflammation on liver biopsy. The similarity between these features and those of other sulfa-induced hepatotoxic reactions suggests that the sulfapyridine moiety is the etiologic agent in these hypersensitivity reactions. Those children with circulating immune complexes responded well to steroids. Proper therapy for this rare but severe idiosyncratic reaction includes prompt recognition and discontinuation of sulfasalazine, and high-dose corticosteroid therapy.

Adolescent↗
PubMed1989

Surgical treatment of arrhythmias in children.

Primary surgical treatment of many tachyarrhythmias in children is now possible. In those with life-threatening arrhythmias not responsive to any form of medical treatment, the choice for surgery is clear. These arrhythmias include atrial fibrillation with the Wolff-Parkinson-White syndrome, PJRT, or atrial ectopic tachycardia with severe congestive cardiomyopathy, incessant ventricular tachycardia in infancy, and recurrent sustained ventricular tachycardia in postoperative congenital heart disease. In the majority of patients, however, surgical treatment remains an option to be weighed carefully against chronic medical treatment. Surgery is now possible with very low mortality for infants and children with Kent bundles, atrial ectopic tachycardia, and the permanent form of junctional reciprocating tachycardia. The mortality, morbidity, and likelihood of eventual resolution of the arrhythmia with each type of management plan should be considered. With possible direct surgical ablation of atrial flutter and newer forms of catheter treatment of arrhythmias, the future looks promising.

Arrhythmias, Cardiac↗