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Biomedical subjects

B Fischer

Publications and source records attributed to B Fischer.

At least 37 records · Page 2Linked to original sources
PubMed1996

Folding of lysozyme.

Due to the detailed knowledge of the three-dimensional structure, chemistry and catalytic mechanism of hen egg white lysozyme, this enzyme has become a major model for the analysis of the folding pathway of globular proteins. Unfolding and folding of lysozyme are reversible processes. Unfolding is a highly cooperative event; under physiological conditions only the native and the unfolded states are stable. Folding of lysozyme involves both a cooperative and a parallel pathway. The complexities in the folding pathway arise from the collapsed state which is formed within a burst-phase in the first milliseconds of folding. In a second, fast folding phase, major parts of the secondary structures both in the alpha-domain and the beta-domain are formed. During the slow folding phase, formation of secondary structure is completed and native tertiary structure is formed in less than 1 second. Folding of reduced lysozyme combines both secondary and tertiary structure organization, as well as formation of four disulphide bonds. Analysis of formation of disulphide bonds showed that there exists a restricted search of structures in the formation of the native conformation and a nucleation in the folding pathway. The transition from a two-disulphide bond intermediate to a three-disulphide bond form appears to be the rate-limiting step in this pathway. Native-like catalytic properties depend on the correct generation of all four disulphide bonds. Folding of both denatured and denatured/reduced lysozyme is characterized by transient folding species possessing structural properties of the molten globule state: high content of secondary structure, no tertiary fold, and the appearance of hydrophobic structures.

Animals↗
PubMed1996

Effects of procues on error rate and reaction times of antisaccades in human subjects.

In a gap paradigm, where the saccadic reaction times are usually short, the number of express saccades can be further increased and their latency decreased when a valid transient peripheral cue is given 100 ms before target occurrence. In the present study we measured the saccadic reaction times of seven human subjects who had been instructed to make antisaccades (saccades to the side opposite to stimulus presentation) in the gap paradigm. In the first experiment, we presented a 100% valid cue with 100 ms cue lead time. To explore whether the cue reduced the reaction times of the antisaccades, the cue was always presented on the opposite side to where the stimulus occurred (stimulus direction was randomized between 4 degrees to the left and right), and it was thus indicated in each trial to which side the antisaccade was required (procue). In the second set of experiments the cue was consistently presented on either the left or the right side in two different blocks; it was thus noninformative with respect to the direction of the antisaccade. In the first experiment, a significant increase in mean reaction times of correct antisaccades and a considerable increase in erratic prosaccades to the stimulus were obtained compared with a control session with no cue. In the two experimental blocks with noninformative cues, the reaction times of correct antisaccades were decreased when cue and stimulus were on at the same side, while large numbers of erratic prosaccades were again obtained when cue and stimulus were presented on opposite sides. These results suggest that the orienting mechanism elicited by a transient peripheral cue relates to the command and to the decision to make a pro- versus an antisaccade. Since the subjects reported that they could not prevent, or, moreover, in some cases did not even realize that they were making erratic prosaccades, we conclude that this orienting mechanism occurs automatically, being largely beyond voluntary control.

Attention↗
PubMed1996

Visualisation of intracranial aneurysms by transcranial duplex sonography.

We examined 72 patients with 89 angiographically confirmed intracranial aneurysms, using transcranial colour-coded duplex sonography (TCCD) to determine the location and size of the aneurysm. The patients were admitted for coil embolisation of their aneurysm following subarachnoid haemorrhage or because of a cranial nerve palsy. Using a 2/2.25 MHz transducer, 42 aneurysms (47%) were seen satisfactorily through the temporal bone window or foramen magnum. In 24 cases (27%) image quality was insufficient as a result of a poor bone window, of the aneurysm having a diameter of less than 6 mm or of its being in an unfavorable location. In 23 other cases (26%) it was not possible to detect the aneurysm. Thrombosed structures could be demonstrated using TCCD in 8 of 12 giant intracavernous or basilar artery aneurysms, and in 15 of 19 aneurysms treated by platinum coil embolisation. TCCD offers a noninvasive method for monitoring progressive intra-aneurysmal thrombosis following coil embolisation and for follow-up of patients with untreatable fusiform aneurysms, should this be required. Detection of small aneurysms is limited by spatial resolution and insonation angles.

Aneurysm, Ruptured↗
PubMed1996

[High resolution computed tomography of the lung in neutropenic patients with fever].

PURPOSE: To determine the sensitivity and clinical impact of high-resolution CT (HRCT) of the lung in febrile neutropenic patients under antibiotic therapy. MATERIAL AND METHODS: Chest X-ray and HRCT were prospectively performed to exclude pneumonia in 34 patients (53 examinations) suffering from febrile neutropenia following antitumor therapy. Diagnosis was confirmed by bronchoalveolar lavage or sputum cultures. RESULTS: Chest X-ray showed pneumonia in 13/53 examinations, in 12/13 a micro-organism was found. HRCT demonstrated pneumonia in 39/53, in 31/39 a micro-organism was found. All cases with positive cultures showed suspicious HRCT findings. Changes in antibiotic treatment resulted in findings suspicious for pneumonia and evidence of a new or a just treated micro-organism (chest X-ray 8/53, HRCT 31/53); the search for the source of fever was escalated in cases without evidence of micro-organisms and without suspicion of pneumonia findings 14/53. CONCLUSION: HRCT of the lung exhibits a higher sensitivity than conventional radiographs. Findings resulted in relevant therapeutic consequences. Hence, HRCT is indicated in neutropenic patients with fever and inconspicuous chest X-ray.

Adolescent↗
PubMed1996

Identification of potent P2Y-purinoceptor agonists that are derivatives of adenosine 5'-monophosphate.

1. A series of chain-extended 2-thioether derivatives of adenosine monophosphate were synthesized and tested as agonists for activation of the phospholipase C-linked P2Y-purinoceptor of turkey erythrocyte membranes, the adenylyl cyclase-linked P2Y-purinoceptor of C6 rat glioma cells, and the cloned human P2U-receptor stably expressed in 1321N1 human astrocytoma cells. 2. Although adenosine monophosphate itself was not an agonist in the two P2Y-purinoceptor test systems, eleven different 2-thioether-substituted adenosine monophosphate analogues were full agonists. The most potent of these agonists, 2-hexylthio AMP, exhibited an EC50 value of 0.2 nM for activation of the C6 cell receptor. This potency was 16,000 fold greater than that of ATP and was only 10 fold less than the potency of 2-hexylthio ATP in the same system. 2-hexylthio adenosine was inactive. 3. Monophosphate analogues that were the most potent activators of the C6 cell P2Y-purinoceptor were also the most potent activators of the turkey erythrocyte P2Y-purinoceptor. However, agonists were in general more potent at the C6 cell receptor, and potency differences varied between 10 fold and 300 fold between the two receptors. 4. Although 2-thioether derivatives of adenosine monophosphate were potent P2Y-purinoceptor agonists no effect of these analogues on the human P2U-purinoceptor were observed. 5. These results support the view that a single monophosphate is sufficient and necessary for full agonist activity at P2Y-purinoceptors, and provide insight for strategies for development of novel P2Y-purinoceptor agonists of high potency and selectivity.

Adenosine Monophosphate↗
PubMed1996

Radiofrequency catheter ablation of common atrial flutter in 200 patients.

INTRODUCTION: The purpose of this study was to evaluate the efficacy and safety of radiofrequency (RF) catheter ablation of common atrial flutter and to determine the optimum target sites in a large series of patients. Three different approaches were used to target the ablation site. The first used a combined anatomic and electrophysiologic approach, whereas the second and the third approaches relied primarily on anatomic guidelines to target the critical area in the atrial flutter reentrant circuit located in the low right atrium. BACKGROUND: Recent studies report the efficacy of RF current application in the low right atrial region to interrupt and prevent recurrences of common atrial flutter using either anatomic or electrophysiologic targets. However, larger groups of patients are required to confirm the efficacy of this technique and to specify the target sites. METHODS AND RESULTS: Two hundred consecutive patients with drug-resistant common atrial flutter were studied. In the first 50 patients, target sites were localized using both anatomic landmarks and electrophysiologic parameters. The anatomic landmarks were area 1 between the tricuspid valve and inferior vena cava orifice; area 2 between the tricuspid valve and coronary sinus ostium; and area 3 between the inferior vena and coronary sinus. The electrophysiologic criterion was to ablate when there was an atrial electrogram occurring during the plateau phase (preceding F wave). The first targeted area was that giving the more stable catheter position. In the following 30 patients, we assessed the effect of RF energy application in a single line to area 1 in the first 10 patients, area 2 in the next 10, and area 3 in the last 10 patients. In the last 120 patients, RF energy was applied only in area 1 using repeated applications. RF energy of 12 to 30 W, or that achieving a temperature of 70 degrees C, was applied for 60 to 90 seconds at each site. The endpoint of the ablation procedure was interruption and noninducibility of common atrial flutter in the first 110 patients and additional isthmal block in 48 of the last 90 patients. Overall, atrial flutter was interrupted and rendered noninducible after a single session in 191 (95%) patients and could not be interrupted in 9 (4.5%) patients. The mean number of RF applications was 12 +/- 8. After a mean follow-up of 24 +/- 9 months, recurrences occurred in 31 (15.5%) patients, 26 of whom underwent a successful second or third session without further recurrences of atrial flutter. Atrial fibrillation not documented before the ablation was detected in 11 patients. On a retrospective analysis of the final successful site in the first group of 50 patients, the location was in area 1 in 39% of patients; area 2 in 36% of patients, and area 3 in 25% of patients. Atrial electrograms recorded at these sites showed a single spike pattern in 46% of patients, and double spike pattern (28%) or fractioned electrogram in 26% patients. When lines of RF lesions were placed at several sites, they produced a success rate of 70%, 40%, and 10% at areas 1, 2, and 3 respectively. In the last series of 120 patients, the procedure was successful in 119 patients: 92% of whom were successfully treated only by a linear lesion between the tricuspid annulus isthmus and the inferior vena cava, and the other 8% by additional applications near the coronary sinus ostium. No complications were observed. CONCLUSIONS: RF catheter ablation of atrial flutter can be done with a high success rate and is safe. The highest success rate is achieved with RF energy applied in the isthmus between the inferior vena cava orifice and the tricuspid valve. However, 15.5% of patients need multiple sessions to achieve success because of recurrence of flutter. Further follow-up is needed to evaluate the long-term effects of this procedure.

Adult↗
PubMed1996

Human express saccade makers are impaired at suppressing visually evoked saccades.

1. We report the oculomotor behavior of human subjects who produce unusually high numbers (> 30%) of express saccades (latency range 85-135 ms) in the overlap saccade task, where express saccades are usually absent or small in number (< 15%). We refer to these subjects as "express saccade makers" (ES makers). 2. We tested the hypothesis that ES makers have difficulties in maintaining fixation and in suppressing unwanted saccades to a suddenly appearing peripheral target by comparing the performances of 10 ES makers and 10 control subjects in gap and overlap antisaccade tasks and in a memory-guided saccade task. 3. The ES makers produced between 35% and 95% incorrect saccades toward the stimulus (prosaccades) in the antisaccade tasks, compared with control subjects, who produced < 20%. Their correct antisaccades appeared to be normal. 4. We further tested the ability of ES makers to maintain fixation and to avoid reflexive saccades to the onset of a target in the memory-guided saccade task. ES makers tended to glance to the briefly presented cue in many trials (4 of them in 50-80% of the trials) instead of delaying the saccade until fixation point offset. Most of the inappropriate saccades had latencies in the range of express saccades. 5. These results can be associated with the finding of fixation related neurons in different cortical and subcortical brain regions (e.g., inferior-parietal and frontal cortex, basal ganglia, superior colliculus). The unusual number of express saccades made by the ES makers in the standard overlap and gap tasks, and their unwanted short-latency reflexive saccades to the target in the memory-guided saccade task, are reminiscent of the performance in these tasks of monkeys whose collicular fixation neurons were chemically deactivated. The collicular fixation neurons are probably the final common pathway in the control of active fixation, and are in mutual inhibitory relationship with the saccade cells. 6. The decreased saccadic control observed in the ES makers suggests that saccade execution in humans is also gated by a fixation system. These ES makers may have reduced voluntarily control over saccade generation as a result of a defect or poor development of their fixation system.

Adolescent↗
PubMed1996

Three-dimensional helical CT of the tracheobronchial tree: evaluation of imaging protocols and assessment of suspected stenoses with bronchoscopic correlation.

OBJECTIVE: To assess the accuracy of three-dimensional (3D) helical CT of normal airways, we evaluated different imaging protocols in test objects and patients. The clinical value of 3D helical CT was composed with bronchoscopy in patients with suspected stenoses, especially before and after endobronchial procedures. SUBJECTS AND METHODS: Solid test objects--one of central airways and one of peripheral airways--were scanned and assessed for volume defects and stairstep artifacts. Fifty helical studies were performed in 36 patients. We evaluated these images for visualization of segmental bronchi; frequency of artifacts; and presence, localization, and degree of stenoses. Bronchoscopic correlation was available for 40 CT examinations. Follow-up 3D helical CT after endobronchial procedures was performed in nine patients. RESULTS: In test objects, thin sections reduced volume artifacts. Overlapping sections mainly diminished stairstep artifacts. In vivo, overlapping sections were superior to contiguous sections for good visualization of the origin (96% versus 89%, p < .01) and of the course (75% versus 54%, p < .001) of segmental bronchi. Three-dimensional helical CT allowed us to assess accurately 36 of 36 central stenoses that were seen on bronchoscopy; however, on 3D helical CT, we missed two of three segmental stenoses. At bronchoscopy, 18 stenoses could not be passed, whereas 3D helical CT provided details for possible endobronchial procedures: length of stenosis, patency (12/18), and spatial orientation of distal bronchi. Follow-up 3D helical CT documented the efficacy of endobronchial treatment. CONCLUSION: Three-dimensional helical CT based on thin overlapping sections accurately visualized the normal airways down to the origin of the segmental bronchi and central stenoses. When it complements bronchoscopy, 3D helical CT allows visualization beyond stenoses, supports planning of endobronchial procedures, and may even substitute for bronchoscopy after endobronchial procedures.

Adult↗
PubMed1995

[Therapy and prognosis of tuberculosis].

Treatment and prognosis of tuberculosis. Worldwide the so-called short-course chemotherapy has become the standard treatment for tuberculosis. The 6-month regimen consists of isoniazid, rifampin, and pyrazinamid given for 2 month followed by isoniazid and rifampin for 4 month. Ethambutol or streptomycin is added in the first 2 month in patients with advanced disease. This recommendation applies to both HIV-infected and uninfected persons. The major determinant of the outcome of treatment is patient adherence to the drug regimen. In susceptible strains the success rate with the 6-month regimen in sputum conversion is far beyond 90% within the first two month of therapy. The relapse rate after 3 to 5 years is about 0-3%. Multiple-drug-resistant tuberculosis (i.e., resistance to at least two drugs) presents difficult treatment problems. Treatment must be individualized and based on susceptibility studies. For patients with tuberculosis that is resistant to rifampin and isoniazid, even the best available treatment is often unsuccessful. The role of new agents such as the quinolone derivatives and amikacin in the treatment of multidrug-resistant disease is not known, although these drugs are commonly being used in such cases.

AIDS-Related Opportunistic Infections↗
PubMed1995

Catheter ablation of permanent junctional reciprocating tachycardia with radiofrequency current.

OBJECTIVES: This study evaluated accessory pathway location, its relation to retrograde P wave polarity on the surface electrocardiogram and radiofrequency ablation efficacy and safety in a large group of patients with permanent junctional reciprocating tachycardia. BACKGROUND: Permanent junctional reciprocating tachycardia is an uncommon form of reciprocating tachycardia, almost incessant from infancy and usually refractory to drug therapy. It is characterized by RP > PR interval and usually by negative P waves in leads II, III, aVF and V4 to V6. Retrograde conduction occurs through an accessory pathway with slow and decremental properties. Although this accessory pathway has been classically located in the posteroseptal zone, other locations have been recently reported. METHODS: The study included 32 patients (20 men, 12 women, mean [+/- SD] age 29 +/- 15 years) with a diagnosis of permanent junctional reciprocating tachycardia confirmed at electrophysiologic study. Seven patients had depressed left ventricular function. Radiofrequency energy was applied at the site of the earliest retrograde atrial activation during tachycardia. RESULTS: There were 33 accessory pathways. The site of the earliest retrograde atrial activation was posteroseptal in 25 patients (76%), midseptal in 4 (12%), right posterior in 1 (3%), right lateral in 1 (3%), left posterior in 1 (3%) and left lateral in 1 (3%). Thirty pathways were ablated with a right approach; in 11 patients with posteroseptal pathway the ablation was performed through the coronary sinus. Three pathways were ablated with a left approach. Positive retrograde P wave in lead I suggested that ablation could be performed from the right side; if negative, it did not exclude ablation from this approach. All the accessory pathways were successfully ablated, with a median of 3 and a mean of 5.6 +/- 5 radiofrequency applications of 70 +/- 26 s in duration. In two patients with the accessory pathway in the midseptal zone, a transient second- and third-degree atrioventricular block, respectively, was observed after ablation. At a mean follow-up of 18 +/- 12 months, 31 patients (97%) are asymptomatic without antiarrhythmic therapy (95% confidence interval [CI] 84% to 99%). Recurrences were observed in four patients (13%) (95% CI 4% to 29%), three of whom had the accessory pathway ablated successfully at a second session. All patients with depressed left ventricular function showed a marked improvement after successful ablation. CONCLUSIONS: In our experience, most of the patients with permanent junctional reciprocating tachycardia had posteroseptal pathways; all these pathways were ablated from the right side. P wave configuration may be helpful in suggesting the approach to the site of ablation. Catheter ablation using radiofrequency energy is an effective therapy for permanent junctional reciprocating tachycardia.

Adolescent↗
PubMed1995

Purification of recombinant human coagulation factors II and IX and protein S expressed in recombinant Vaccinia virus-infected Vero cells.

Recombinant human coagulation factors II and IX and recombinant human protein S were expressed by the Vaccinia virus expression system in Vero cells and isolated from the serum-free media. All three recombinant proteins were purified by the same universal strategy. After concentration by anion exchange chromatography, recombinant coagulation factors were purified by anion exchange filtration in the presence of Ca2+. The addition of Ca2+ to the vitamin K-dependent coagulation factors modified their physico-chemical behavior during anion exchange chromatography and resulted in the separation of the recombinant coagulation proteins from contaminating proteins.

Animals↗
PubMed1995

The three-loop model: a neural network for the generation of saccadic reaction times.

This paper presents a computer simulation of the three-loop model for the temporal aspects of the generation of visually guided saccadic eye movements. The intention is to reproduce complex experimental reaction time distributions by a simple neural network. The operating elements are artificial but realistic neurones. Four modules are constructed, each consisting of 16 neural elements. Within each module, the elements are connected in an all-to-all manner. The modules are working parallel and serial according to the anatomically and physiologically identified visuomotor pathways including the superior colliculus, the frontal eye fields, and the parietal cortex. Two transient-sustained input lines drive the network: one represents the visual activity produced by the onset of the saccade target, the other represents a central activity controlling the preparation of saccades, e.g. the end of active fixation. The model works completely deterministically; its stochastic output is a consequence of the stochastic properties of the input only. Simulations show how multimodal distributions of saccadic reaction times are produced as a natural consequence of the model structure. The gap effect on saccadic reaction times is correctly produced by the model: depending only on the gap duration (all model parameters unchanged) express, fast-regular, and slow-regular saccades are obtained in different numbers. In agreement with the experiments, bi- or trimodal distributions are produced only for medium gap durations (around 200 ms), while for shorter or longer gaps the express mode disappears and the distributions turn bi- or even unimodal. The effect of varying the strength of the transient-sustained components and the ongoing activity driving the hierarchically highest module are considered to account for the interindividual variability of the latency distributions obtained from different subjects, effects of different instructions to the same subject, and the observation of express makers (subjects who produce exclusively express saccades). How the model can be extended to describe the spatial aspects of the saccade system will be discussed as well as the effects of training and/or rapid adaptation to experimental conditions.

Computer Simulation↗
PubMed1995

Complement C1q and C3 mRNA expression in the frontal cortex of Alzheimer's patients.

The levels and cellular localization of mRNA for complement C1q and C3 were examined by RNA gel blot and nonradioactive in situ hybridization in the frontal cortex of patients with Alzheimer's disease (AD) and age-matched controls. We found that the hybridization signal for C1q mRNA was markedly increased (approx. 3.5-fold) in the frontal cortex of AD patients compared to that in age-matched controls. In contrast to previous reports we also found that the levels of C3 mRNA, although well expressed, did not differ significantly between AD cases and age-matched controls. Nonradioactive in situ hybridization using digoxigenin-labeled ribo-probes revealed that transcripts coding for both C1q and C3 were closely associated with neurons. These results support the hypothesis that complement could play a role in neuronal degeneration which has been observed in the brain of AD patients.

Aged↗
PubMed1995

Gap duration and location of attention focus modulate the occurrence of left/right asymmetries in the saccadic reaction times of human subjects.

Five human subjects were trained in a single target gap saccade task (fixation point offset precedes target onset, target presentation random at 4 deg to the left or right of the fixation point). Four of them produced different distributions of saccadic reaction times (SRT) for left vs right directed saccades. These asymmetries consisted mostly in different numbers of express saccades, which the subjects produced to the left and to the right side. Using different gap durations (0, 100, 200, 300 and 400 msec) and an overlap task, we found a systematic modulation of the frequency of express saccades: for the shortest and longest gap durations, and in the overlap task, express saccades tended to decline. As a consequence of this effect asymmetric SRTs became rather symmetric for these gap durations. In a gap task where the central fixation point was replaced by a peripheral attention target the occurrence of express saccades was strongly modulated by the location of the attention target relative to the saccade target: for all subjects the frequency of express saccades decreased when the saccade target occurred in the close vicinity of the peripheral attention target. This effect resulted again in clear modifications of the observed asymmetries. We suggest that the occurrence of express saccades can be influenced in a dynamic way by the permanent allocation of the subject's visual attention. Moreover, the phenomenon of direction asymmetry in the SRT distributions can be modulated by such manipulations of the attentional focus.

Adult↗
PubMed1995

Intertrial effects of randomization on saccadic reaction times in human observers.

We investigated the effect of randomizing different spatial and temporal parameters on saccadic reaction times (SRTs) in five human subjects, to explore the relative occurrence of express and regular saccades. Parameters randomized in various test sessions were: target direction (right/left), intertrial interval, fixation foreperiod and gap duration (two or three 400 msec) in gap and overlap trials. For the sake of comparison the parameters under consideration were kept constant in non-random control sessions. We found that express saccades were still present in the random test sessions but their relative frequency (and the number of regular saccades) obtained in a given test session depends on the type of randomized parameters: randomizing the intertrial interval or the fixation foreperiod in the gap task yielded modest but significant changes in the SRT distributions, express and fast regular saccades being present in both the control and the random conditions. Randomization of the fixation foreperiod in the overlap task, on the other hand, caused a quite drastic increase in the SRTs. Randomization of gap and overlap trials did not cause considerable effects on express and fast regular saccades in the gap trials, and the SRTs in the overlap trials were significantly increased only in two subjects. When two or three gap durations were randomly interleaved, we found effects that ranged from "negligible" (usually for the longest gap in a given test session) to highly significant differences as compared with the corresponding control condition. The results suggest that express saccades--as fast regular saccades--are visually guided saccades which occur when a certain state of saccade preparation has been reached before target onset. This state depends on the amount of activation in the brain structures involved in the control of attention and fixation, and the decision processes involved in saccade preparation.

Adult↗
PubMed1995

Radiofrequency catheter ablation of common atrial flutter in 80 patients.

OBJECTIVES: The purpose of this study was to evaluate the efficacy and safety of radiofrequency catheter ablation of common atrial flutter and to determine the optimal target sites in a large series of patients. BACKGROUND: Recent studies report the efficacy of radiofrequency current application in the low right atrial region to interrupt and prevent recurrences of common atrial flutter. However, larger groups of patients are required to confirm the efficacy of this technique and to specify the target sites. METHODS: Two different approaches were used to target the ablation site in 80 consecutive patients. In the first 50 patients, target sites were localized using both anatomic landmarks and electrophysiologic variables. Three anatomic landmarks were used: area 1 = between the tricuspid valve and inferior vena cava orifice; area 2 = between the tricuspid valve and coronary sinus ostium; area 3 = between the inferior vena cava and coronary sinus. The electrophysiologic criterion was to ablate when there was a stable atrial electrogram during the plateau phase. In the next 30 patients we assessed the effect of application of radiofrequency energy in a single line in area 1, 2 or 3 in groups of 10 patients. RESULTS: Overall atrial flutter was interrupted and rendered noninducible after a single session in 72 patients (90%) and could not be interrupted in 8 (10%). The mean (+/- SD) number of radiofrequency applications was 12 +/- 8. After a mean (+/- SD) follow-up of 20 +/- 8 months, recurrences occurred in 14 patients (17%). The location of the final successful site in the first group of 50 patients was in area 1 in 39%, area 2 in 36% and area 3 in 25%. In the next 30 patients, when lines of radiofrequency lesions were placed at several sites, they produced success rates of 70%, 40% and 10% at areas 1, 2 and 3, respectively. CONCLUSIONS: Radiofrequency catheter ablation of atrial flutter can be performed with a high success rate and is safe. The highest success rate is achieved with radiofrequency energy applied in the isthmus between the inferior vena cava orifice and tricuspid valve.

Actuarial Analysis↗