PubMed Health⌕ Search

Biomedical subjects

R Goyal

Publications and source records attributed to R Goyal.

At least 127 records · Page 7Linked to original sources
PubMed1994

Analysis of junctional ectopy during radiofrequency ablation of the slow pathway in patients with atrioventricular nodal reentrant tachycardia.

BACKGROUND: Junctional ectopy may occur during radiofrequency (RF) catheter ablation of the slow pathway in patients with atrioventricular nodal reentrant tachycardia (AVNRT). The purpose of the present study was to characterize this junctional ectopy quantitatively. METHODS AND RESULTS: The subjects of this study were 52 consecutive patients with AVNRT who underwent slow pathway ablation and 5 additional patients included retrospectively because they had developed high-degree atrioventricular (AV) block during the procedure. A combined anatomic and electrogram mapping approach was used for slow pathway ablation, and AVNRT was successfully eliminated in all patients. In the group of 52 consecutive patients, the incidence of junctional ectopy was significantly higher during 52 effective applications of RF energy than during 366 ineffective applications (100% versus 65%, P < .001). Compared with ineffective RF energy applications, successful RF energy applications had a significantly longer duration of individual bursts of junctional ectopy (7.1 +/- 7.1 versus 5.0 +/- 7.0 seconds [+/- SD], P < .05), a greater total number of junctional beats during the applications (24 +/- 16 versus 15 +/- 8, P < .01), and a greater total span of time during which junctional ectopy occurred (19 +/- 15 versus 11 +/- 12 seconds, P < .01). Four of the 52 patients plus an additional 5 patients developed transient AV block lasting 34 +/- 37 seconds. In 1 of the 9 patients who had transient AV block, third-degree AV nodal block requiring a permanent pacemaker recurred 2 weeks later. In each of the 9 patients who developed AV block, there was ventriculoatrial (VA) block in association with junctional ectopy during the RF energy application immediately preceding the AV block. Among 48 patients who did not develop AV block, 17 patients had at least one episode of VA block during junctional ectopy. The positive predictive value of VA block during junctional ectopy for the development of AV block was 19% in the consecutive series of 52 patients. Among 31 patients who always had 1:1 VA conduction in association with junctional ectopy, 12 had poor VA conduction in the baseline state, with a VA block cycle length of at least 500 milliseconds during ventricular pacing. CONCLUSIONS: In patients with AVNRT undergoing slow pathway ablation, junctional ectopy during the application of RF energy is a sensitive but nonspecific marker of successful ablation. The bursts of junctional ectopy are significantly longer at effective target sites than at ineffective sites. VA conduction should be expected during the junctional ectopy that accompanies slow pathway ablation, even when there is poor VA conduction during baseline ventricular pacing. VA block during junctional ectopy is a harbinger of AV block in patients undergoing RF ablation of the slow pathway. If energy applications are discontinued as soon as VA block occurs, the risk of AV block may be markedly reduced.

Adolescent↗
PubMed1993

Macrophage-mediated enterocyte damage in BALB/c mice infected with different strains of Giardia lamblia.

The mechanism of mucosal injury in Giardia lamblia-infected animals and humans is not well understood, although the role of gut macrophages in killing the trophozoites is well known. It is speculated, however, that macrophage products have a role in tissue injury and inflammatory response during infection, as in other inflammatory diseases. Therefore, in the present study an attempt was made to examine the mechanism involved in enterocyte damage during giardiasis. This was achieved using co-culture of enterocytes and gut macrophages obtained from infected BALB/c mice. The extent of tissue damage was assessed by measuring the marker enzyme of enterocyte damage, lactate dehydrogenase. To investigate the role of the various proteases and free oxygen radicals released by activated macrophages on enterocyte damage, inhibitors of various proteases and free oxygen radicals were used. Superoxide radical and certain proteases were found to have important roles in bringing about enterocyte damage during this infection in mice. Parasite load, lactate dehydrogenase release, and extent of lipid peroxidation were more pronounced in mice infected with symptomatic strains than in asymptomatic ones. The theory of inflammatory cell-mediated enterocyte damage in Giardia lamblia infection is proposed.

Animals↗
PubMed1993

Chemotherapy and combination therapy in anaplastic thyroid carcinoma.

The majority of patients with anaplastic thyroid carcinoma will achieve local tumour control with a combination of pre- and postoperative chemotherapy and radiotherapy. A few patients may even be cured with this regime. Chemotherapy alone for advanced thyroid carcinoma cannot, however, be routinely recommended. The chemotherapeutic agents in current use are discussed. Multimodality treatment remains the treatment of choice for undifferentiated thyroid carcinoma.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1992

Current hypotheses of structural pattern formation in the somatosensory system and their potential relevance to humans.

Current hypotheses of structural pattern formation in the mammalian somatosensory system are modeled on experimental findings from the trigeminal system of rodents. The present results show that, like rodents, the trigeminal nucleus principalis of humans contains a parcellated pattern of cytochrome oxidase dense patches. These results provide an indication of the potential usefulness of rodent-based hypotheses for understanding pattern formation in human somatosensory connections.

Adult↗
PubMed1992

Conversion of typical to "atypical" atrioventricular nodal reentrant tachycardia after radiofrequency catheter modification of the atrioventricular junction.

Typical atrioventricular (AV) nodal reentry tachycardia (AVNRT) is characterized by anterograde activation over a slowly conducting pathway and by retrograde activation through a rapidly conducting pathway. Preliminary reports suggest that radiofrequency catheter modification can eliminate typical AVNRT while preserving anterograde conduction. Radiofrequency catheter modification was used to treat 88 patients with typical AVNRT. After baseline electrophysiologic evaluation, the ablation catheter was positioned proximal and superior to the site of maximal His deflection. Radiofrequency energy was applied until there was significant attenuation of retrograde conduction, and elimination of AVNRT inducibility. Eighty-one patients were successfully treated and form the basis of this report. A new paroxysmal supraventricular tachycardia with RP greater than PR interval was induced at electrophysiologic testing after successful ablation in 9 patients (11%). Mean atrial-His activation time was 140 +/- 31 ms, and the ventriculoatrial activation time was 170 +/- 46 ms. This arrhythmia was induced only with ventricular pacing during isoproterenol infusion and appeared to be mediated by AV nodal reentry. New retrograde dual AV nodal physiology after modification was more frequent in patients with atypical tachycardia than in those without (4 of 9 vs 2 of 72; p less than 0.0001). Although none of the patients were treated, only 1 of 9 had an episode of spontaneous atypical tachycardia during a mean follow-up of 12 months. Results of this study confirm that typical AVNRT can be rendered noninducible without the complete destruction of reentrant pathways. Because induction of "atypical" AVNRT was not predictive of spontaneous arrhythmia recurrence, it should not be an indication for additional ablation sessions or long-term drug therapy.

Adult↗
PubMed1991

Assessment of left ventricular function in chronic severe anaemia. An echocardiographic study.

Left ventricle (LV) performance was assessed by echocardiography (2-D and M-mode) in 30 patients with chronic severe anaemia and an equal number of age and sex matched healthy controls. Patients with anaemia were divided into two groups: those with tachycardia (pulse rate more than 100 per min) and those without. LV performance indices computed were LV ejection fraction (LVEF), % fractional shortening (FS), cardiac index (CI) and stroke volume index (SVI). In patients of anaemia with tachycardia, LVEF was 48.6 +/- 8.41 (mean +/- SEM) vs 71.6 +/- 4.96 among controls. Percentage FS was 19.93 +/- 4.21 vs 36.0 +/- 4.5, CI 5.46 +/- 1.2 vs 3.1 +/- 0.78 l/min/m2, and stroke index 48.6 +/- 12.2 vs 41.5 +/- 10.7 ml/beat/m2. In patients without tachycardia, LVEF was 55.1 +/- 8.86, percentage FS 23.6 +/- 5.42, CI 2.87 +/- 0.526 and stroke index 41.34 +/- 12.1. These findings suggest that LV performance was depressed in both groups of patients with anaemia but LV function was better in patients without tachycardia.

Adolescent↗
PubMed1991

Aneurysmal bone cyst of the mandible.

The clinical features, radiological findings, microscopic examination and treatment of a case of aneurysmal bone cyst have been discussed. The histopathological examination is the only way to confirm the diagnosis of this interesting bone lesion which rarely affects the jaws.

Bone Cysts↗
PubMed1989

Can two-dimensional echocardiography and Doppler color flow mapping identify the need for tricuspid valve repair?

Tricuspid regurgitation severity was assessed preoperatively with Doppler color flow mapping and these assessments were compared with surgical findings in 90 patients undergoing mitral or aortic valve replacement, or both. Group I (n = 52) required tricuspid valve annuloplasty because tricuspid regurgitation was judged intraoperatively to be severe; in Group II (n = 38), tricuspid valve annuloplasty was not performed because tricuspid regurgitation was judged intraoperatively not to be severe. With use of the apical four chamber and parasternal short-axis imaging planes, the severity of tricuspid regurgitation by Doppler color flow mapping was assessed by comparing the maximal area of tricuspid regurgitant signals with the right atrial area taken in the same frame in which the maximal tricuspid regurgitant signals were noted. This ratio was found to be greater than or equal to 34% (mean 50.2 +/- 11.8%) in 50 (96%) of 52 patients in Group I and less than 34% (mean 27.5 +/- 6.9%) in 36 (95%) of 38 patients in Group II (p less than 0.001). The maximal diastolic tricuspid anulus diameter measured with the same two-dimensional imaging planes was greater than or equal to mm/m2 body surface area (mean 26.7 +/- 5.2 mm/m2) in 46 patients (88%) in Group I and less than 21 mm/m2 (mean 17.8 +/- 2.5 mm/m2) in 36 patients (95%) in Group II (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Pressure↗
PubMed1989

Abortive infection of the virulent phage 9NA in a fatty acid auxotroph of Salmonella typhimurium: effect of fatty acid supplementation.

A conditional (temperature sensitive) fatty acid biosynthetic mutant (fabB2) of Salmonella typhimurium does not support the development of the virulent bacteriophage 9NA even at permissive temperature (30 degrees C). A limited amount of phage DNA synthesis takes place at this temperature. When the fatty acid composition of the host membrane is altered by growing the cells at 37 degrees C in the presence of exogenous unsaturated fatty acid, differential expression of phage genes was observed. Phage specific lysozyme is induced when the cultures are supplemented with elaidic, palmitelaidic, linoleic and linolelaidic acids but not with oleic and plamitoleic acids. However, in no case were infective particles produced. Under conditions where no lysozyme is synthesized the infected cells increase in length and become filamentous.

Bacteriophages↗
PubMed1989

Influence of a cysteine prodrug, L-2-oxothiazolidine-4-carboxylic acid, on the urinary elimination of mercapturic acids of ethylene oxide, dibromoethane, and acrylonitrile: a dose-effect study.

Metabolic disposition of ethylene oxide, dibromoethane, and acrylonitrile in rats after acute exposure was studied by examining the relationship between dose and urinary metabolites, and by establishing the influence of a glutathione precursor, L-2-oxothiazolidine-4-carboxylic acid (OTCA), on the above relationship. Respective urinary metabolites, hydroxyethylmercapturic acid, cyanoethylmercapturic acid, thiocyanate, and ethylene glycol, were quantified to estimate the extent to which each compound was metabolized. The animals were given either ethylene oxide (0.34, 0.68, or 1.36 mmol/kg), dibromoethane (0.2, 0.4, or 0.6 mmol/kg), or acrylonitrile (0.10, 0.38, or 0.76 mmol/kg). Urine samples were collected at 24 h. The metabolic biotransformation of all three chemicals to their respective mercapturic acids was strongly indicative of saturable metabolism. Administration of OCTA (4-5 mmol/kg) enhanced gluthathione availability and increased excretion of urinary mercapturic acids at the higher doses of the chemicals. This study indicates that OTCA increases the capacity for detoxification via the glutathione pathway thereby partially correcting the nonlinearity between the administered dose of ethylene oxide, dibromoethane, and acrylonitrile and the amount of certain urinary metabolites.

Acetylcysteine↗
PubMed1987

Species differences in the urinary disposition of some metabolites of ethylene oxide.

Some aspects of the qualitative and quantitative urinary disposition of some metabolites of ethylene oxide in three rodent species, mouse, rat, and rabbit, were examined by determining urinary N-acetyl-S-(2-hydroxyethyl)-L-cysteine, S-(2-hydroxyethyl)-L-cysteine, S-carboxymethyl-L-cysteine, and ethylene glycol after ethylene oxide exposure by iv and inhalation routes. The animals were given ethylene oxide at 20 and 60 mg/kg, and urine samples were collected at 6 and 24 hr. Important differences were observed between the three species in the urinary metabolic disposition of ethylene oxide. Mice excreted significant quantities of N-acetyl-S-(2-hydroxyethyl)-L-cysteine, S-(2-hydroxyethyl)-L-cysteine, S-carboxymethyl-L-cysteine, and ethylene glycol (8.3, 5.8, 1.9, and 3.3% of the lower dose, respectively, in 24 hr), whereas in rats only N-acetyl-S-(2-hydroxyethyl)-L-cysteine (31%) and ethylene glycol (6%) were apparent. In contrast, the rabbits were found to excrete only ethylene glycol (2%). This study further reveals species-related differences in the urinary excretion of N-acetyl-S-(2-hydroxyethyl)-L-cysteine and ethylene glycol during the two collection periods. The observed differences between the three species in the metabolic disposition of ethylene oxide were found to be qualitatively independent of the route of exposure, i.e., inhalation at 200 ppm or iv. These results suggest that care should be exercised when using an animal species as a model for human disposition of ethylene oxide.

Administration, Inhalation↗