Kinetic modeling of the SWNT growth by CO disproportionation on CoMo catalysts.

A kinetic model has been developed to describe the growth of single-walled carbon nanotubes (SWNT) in the CoMoCAT method, which is based on the disproportionation of CO on supported CoMo catalysts. The model attempts to capture mathematically the different stages involved in this method: (i) catalyst activation or in-situ creation of active sites, i.e., reduced Co clusters by transformation of CoMoOx precursor species, or oxidized sites; (ii) CO decomposition over active sites, which increases the surface fugacity of carbon until reaching a certain threshold; (iii) nucleation of ordered forms of carbon; (iv) C diffusion (both across the surface and into the metal particle); (v) SWNT growth; (vi) termination, by either deactivation of the catalyst active sites or by increase in the carbon concentration at the metal/SWNT interface, approaching that of the metal/gas interface and eliminating the driving force for diffusion. Previous investigations have only explained the growth termination by the former. Here, we emphasize the possible contribution of the later and propose a novel "hindrance factor" to quantify the effect of nanotube interaction with its surroundings on the growth termination. To test the kinetic model and obtain typical values of the physical parameters, experiments have been conducted on a CoMo/SiO2 catalyst in a laboratory flow reactor, in which the rate of carbon deposition was continuously evaluated by the direct measurement of the CO2 evolution as a function of time. The experimental data are fitted very well with model.

Role of autonomic reflexes in syncope associated with paroxysmal atrial fibrillation.

OBJECTIVES: The purpose of this study was to evaluate the role of autonomic reflexes in the genesis of syncope associated with the onset of paroxysmal atrial fibrillation. BACKGROUND: Syncope associated with paroxysmal atrial fibrillation has been interpreted as an ominous finding predictive of rapid ventricular rates. However, various mechanisms may be involved when heart rate is not particularly high. METHODS: Forty patients (age 60 +/- 14 years, 20 men, 20 women) with syncope and atrial fibrillation were compared with atrial fibrillation without syncope. Carotid sinus massage and head-up tilt testing (at 60 degrees for 60 min at baseline and during isoproterenol infusion) were performed during sinus rhythm. A positive response was defined as the induction of syncope. Atrial fibrillation was also induced on a tilt table at 60 degrees by means of short bursts of atrial pacing. RESULTS: Results of carotid sinus massage were positive in 15 (37%) of 40 patients but in no control subjects (p = 0.002). Head-up tilt test findings were positive in 25 (66%) of 38 patients and in 2 (12%) of 16 control subjects (p = 0.0004). The induction of atrial fibrillation in the upright position elicited syncope in 16 (42%) of 38 patients but in none of 16 control subjects (p = 0.001). At the beginning of atrial fibrillation, systolic blood pressure was lower in patients than in control subjects (88 +/- 32 vs. 127 +/- 32 mm Hg), whereas mean heart rate was similar (142 +/- 35 vs. 134 +/- 25 beats/min). The correlation between heart rate and systolic blood pressure was weak (r = 0.35), and in five patients syncope occurred at a heart rate < or = 130 beats/min. At the time of syncope, heart rate decreased (-12 +/- 21 beats/min) in patients with induced syncope, whereas it remained unchanged in patients without induced syncope (+1 +/- 17 beats/min, p = 0.04) or slightly increased in control subjects (+9 +/- 21 beats/min, p = 0.009). CONCLUSIONS: Patients with syncope associated with paroxysmal atrial fibrillation are predisposed to an abnormal neural response during both sinus rhythm and arrhythmia. In some patients the onset of atrial fibrillation triggers vasovagal syncope.

An abnormal neural reflex plays a role in causing syncope in sinus bradycardia.

OBJECTIVES: This study investigates the role of an abnormal neural reflex in causing syncope in patients with sinus bradycardia. BACKGROUND: Syncope is commonly considered an indication of severity in sinus bradycardia. However, the occurrence of syncope is unpredictable, and the prognosis appears to be similar in patients with and without syncope. METHODS: Head-up tilt testing (60 degrees for 60 min), carotid sinus massage in the supine and standing positions, 24-h Holter ambulatory electrocardiographic (ECG) recording and electrophysiologic study before and after pharmacologic autonomic blockade were performed in 25 patients with sinus bradycardia and syncope (group I, sinus rate < 50 beats/min, age 71 +/- 12 years) and 25 patients with sinus bradycardia and no neurologic symptoms (group II, sinus rate < 50 beats/min, age 67 +/- 16 years). RESULTS: Clinical characteristics and ambulatory ECG monitoring data were similar in the two study groups. A positive response (induction of syncope or presyncope with hypotension and/or bradycardia) was obtained by head-up tilt testing in 15 group I (60%) and in 3 group II (12%) patients (p < 0.001) and by carotid sinus massage in 11 group I (44%) and 6 group II (24%) patients (p = NS). Results of at least one test (head-up tilt testing or carotid sinus massage, or both) were positive in 19 group I (76%) and 9 group II (36%) patients (p < 0.01). Basal and intrinsic corrected sinus node recovery time did not differ significantly between the two groups. An abnormal intrinsic heart rate was present in 66% of group I and 26% of group II patients (p < 0.01). The different percentage of positive findings on head-up tilt testing and carotid sinus massage in the two groups was independent of the presence of intrinsic sinus node dysfunction. CONCLUSIONS: These results indicate that an abnormal neural reflex plays a role in causing syncope in patients with sinus bradycardia. This reflex seems to be unrelated to the severity of sinus node dysfunction, even if the latter could enhance the cardioinhibitory response.

Sinus node function in hyperthyroid patients.

We have studied the electrophysiology of the sinus node and the role of the autonomic nervous system on sinus node function in 8 thyrotoxic patients of both sexes, 37.5 +/- 4.3 (mean +/- SE) yr old. The resting heart rate (RHR), the sino-atrial conduction time (SACT), and the sinus node recovery time (SNRT) were measured in the untreated condition (basal), after sympathetic blockade with propranolol 0.2 mg/kg body weight (BW) i.v. infusion, and after complete autonomic blockade with the additional administration of atropine 0.04 mg/kg BW i.v. bolus. 1) In the thyrotoxic patients the RHR was higher [117 +/- 6 beats per min (bpm)] than in 20 normal subjects (73 +/- 1 bpm, P less than 0.001), whereas the SACT and SNRT values were not different. 2) After sympathetic blockade with propranolol, the RHR decrement and SACT increase were greater in the hyperthyroid patients than in normal subjects, whereas there was no difference in SNRT values between the two groups. 3) In the thyrotoxic patients the complete autonomic blockade reestablished the electrophysiological parameters to values similar to those observed in basal condition. In conclusion, in thyrotoxic patients the intrinsic activity of the sinus node is increased. It appears that this is a direct consequence of thyroid hormone excess, rather than an effect of extrinsic influences exerted by the autonomic nervous system on sinus node activity.

Long-term outcome of paced and nonpaced patients with severe carotid sinus syndrome.

The natural history of patients with severe carotid sinus syndrome, and the efficacy of permanent pacemaker treatment are not clearly known. A randomized treatment/nontreatment prospective study was performed in 60 patients affected by carotid sinus syndrome whose symptoms were judged to involve risk of major trauma or interfered with their daily activity. They were randomly assigned to 2 groups: 28 patients to no therapy (nonpacing group), and 32 to VVI (n = 18) or DDD (n = 14) pacemaker implant (pacing group). Syncope recurred in 16 patients (57%) of the nopacing group (mean follow-up 36 +/- 10 months) and in only 3 (9%) of the pacing group (mean follow-up 34 +/- 10 months) (p = 0.0002); moreover, 19 (68%) in the nonpacing group needed a secondary pacemaker implant because of the severity of symptoms. The actuarial rate of absence of syncopal recurrence after 1, 2, 3 and 4 years was 64, 54, 38 and 38%, respectively, for the nonpacing group, and 100, 97, 93 and 84%, respectively, for the pacing group (p = 0.0001). The actuarial rate of absence of minor symptoms after 1, 2, 3 and 4 years was 21, 14, 7 and 7%, respectively, for the nonpacing group and 66, 43, 27 and 27%, respectively, for the pacing group (p = 0.002). Reproducibility of carotid sinus reflex was tested after 15 +/- 8 months in 54 patients; an abnormal response to carotid sinus massage persisted in all 54. In conclusion, symptoms recur in most patients with untreated carotid sinus syndrome, and pacing is a useful therapy for preventing recurrences.

Progression of permanent atrial fibrillation after atrioventricular junction ablation and dual-chamber pacemaker implantation in patients with paroxysmal atrial tachyarrhythmias.

Among 63 patients affected by symptomatic drug refractory paroxysmal atrial fibrillation who had undergone atrioventricular junction ablation and dual-chamber pacemaker implantation, the actuarial estimate of progression of permanent atrial fibrillation was 22%, 40%, and 56% respectively, 1, 2, and 3 years after ablation. A stratification of the risk of development of permanent atrial fibrillation was obtained on the basis of several clinical variables.

Follow-up of asystolic episodes in patients with cardioinhibitory, neurally mediated syncope and VVI pacemaker.

The occurrence rate of spontaneous asystolic episodes during long-term follow-up in patients with abnormal asystolic responses induced by means of vasovagal maneuvers was evaluated. The heart rate of 23 patients (mean age 64 +/- 12 years; 6 women and 17 men) affected by neurally mediated syncope (mean 4.3 +/- 4.9 episodes) was continuously monitored by a specially designed implanted pacemaker able to detect and store in its memory all asystolic episodes lasting 3 to 6 or > 6 seconds. Asystolic, neurally mediated syncope was diagnosed when a reflex asystole of > 3 seconds was induced during carotid sinus massage (n = 22), eyeball compression test (n = 3) or head-up tilt test (n = 2). During a total of 357 months (mean 15 +/- 7) of monitoring, asystolic episodes occurred in 17 patients (74%): 1,765 episodes of 3- to 6-second (median 3) duration occurred in 14 patients, and 47 episodes of > 6-second (median 2) duration occurred in 11. The actuarial estimates of occurrence of asystolic episodes of > 3 and > 6 seconds were 82 and 53%, respectively, after 2 years of follow-up. Only 12 episodes of 3 to 6 seconds (0.7%), and 20 episodes of > 6 seconds (43%) resulted in presyncopal or syncopal symptoms. Thus, an asystolic response to vasovagal maneuvers predicts the occurrence of spontaneous asystolic episodes during follow-up. With few exceptions, spontaneous episodes are asymptomatic and their incidence is low.

Influence of atrioventricular junction radiofrequency ablation in patients with chronic atrial fibrillation and flutter on quality of life and cardiac performance.

The purpose of this study was to evaluate the effects of atrioventricular junction radiofrequency ablation on the quality of life, exercise performance, and echocardiographic parameters in 23 patients with chronic, severely symptomatic, drug-refractory atrial fibrillation or flutter. Initially, patients were randomized to receive ablation plus pacemaker therapy (n = 12) or pacemaker therapy alone (n = 11). After 15 days, palpitations decreased by 92% and 37% (p = 0.004), rest dyspnea by 79% and 40% (p = NS), effort dyspnea by 65% and 30% (p = 0.03), exercise intolerance by 54% and 17% (p = 0.005), and asthenia by 67% and 31% (p = 0.02) in the 2 groups, respectively. At the end of this short-term study, control patients also underwent ablation therapy, and a 3-month intrapatient follow-up study was performed in 22 patients. New York Heart Association functional class > or = 3 was present in 14 patients (64%) before, but in only 3 patients (14%) after ablation therapy (p = 0.002); specific activity scale functional class > or = 3 was present in 9 patients (41%) before, but in only 5 (23%) after ablation therapy (p = NS). Exercise duration during standardized stress testing increased by a mean of 63 +/- 93 seconds (15% increase) (p = 0.001). In the 9 patients with depressed left ventricular systolic function, echocardiographic fractional shortening increased by 34% (from 23 +/- 5% to 31 +/- 9%) (p = 0.003). In the remaining 13 patients with normal systolic function, fractional shortening decreased by 10% (from 40 +/- 5% to 36 +/- 6%) (p = 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Neurally mediated syncope detected by carotid sinus massage and head-up tilt test in sick sinus syndrome.

It is generally accepted that a positive response to carotid sinus massage (CSM) or head-up tilt (HUT) in patients affected by syncope suggests a reflex cause of the syncope. To study the role of the autonomic nervous system in causing syncope in the sick sinus syndrome (SSS), CSM and HUT were performed in 35 consecutive patients (20 men, mean age 70 +/- 9 years) with syncope and SSS. Results were compared with those in 35 patients affected by syncope that, despite careful cardiovascular and neurologic examination, were of uncertain origin (21 men; mean age 68 +/- 9 years) and with those of 35 subjects without syncope (20 men; mean age 69 +/- 10). All patients underwent CSM in the supine and standing positions for 10 seconds and HUT to 60 degrees for 60 minutes. In the patients with SSS, the full reproduction of spontaneous symptoms by CSM occurred in 21 (60%) and by HUT, in 19 (54%). At least 1 test was positive in 28 patients (80%): cardioinhibitory or mixed responses in 69%, vasodepressor responses in 11%. The percentages of positive tests in the patients with syncope of uncertain origin were similar to or slightly less than those of patients with SSS (CSM 63%, HUT 26%, overall 74%) with cardioinhibitory or mixed responses in 54% and vasodepressor in 20% (p less than 0.05). In control subjects, syncope was induced by CSM in 1 (3%) and by HUT in 2 (6%); overall positivity was 9%. In conclusion, in most patients affected by syncope and SSS, an abnormal neural reflex probably plays a major role in causing syncope.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanisms of syncope caused by transient bradycardia and the diagnostic value of electrophysiologic testing and cardiovascular reflexivity maneuvers.

Transient bradycardia may be intrinsic because of sinus node or atrioventricular (AV) conduction abnormalities, or extrinsic because of abnormal vagal reflex. Twenty-five consecutive patients, referred to us for study of unexplained syncope, who, during electrocardiographic monitoring, had a documented episode of intermittent bradycardia that caused syncope, underwent a full electrophysiologic study, carotid sinus massage, and the head-up tilt test. A prolonged ventricular asystole (5 to 20 seconds) was documented during syncope in all patients: sinus arrest in 13, AV block in 7, sinus arrest plus AV block in 3, and asystolic pause during atrial fibrillation in 2. Abnormal electrophysiologic findings suggested the correct diagnosis in 6 patients (24%): block within the bundle of His in 5 and sick sinus syndrome in 1. An abnormal response to carotid sinus massage or to the head-up tilt test suggested a neurally mediated mechanism in 17 patients (68%). Overall, electrophysiologic study and vasovagal maneuvers were able to identify the mechanism of spontaneous syncope in 23 patients (92%). Thus, in patients affected by syncope due to transient bradycardia, the most likely mechanism of syncope is neurogenic, whereas it is cardiogenic only in a few instances. Electrophysiologic testing, carotid sinus massage, and the head-up tilt test can identify most of these patients. Conversely, when all these tests are negative, it is unlikely that transient bradycardia is the cause of syncope. Because of the different mechanisms involved, electrophysiologic study and vasovagal maneuvers are complementary diagnostic tools.

A controlled trial of acute and long-term medical therapy in tilt-induced neurally mediated syncope.

To study the efficacy of medical treatment for preventing syncopal recurrences in patients affected by tilt-induced neurally mediated syncope, a randomized placebo-treatment prospective study was performed in 30 patients (10 men and 20 women, mean age 42 +/- 21 years) who had syncope reproduced in 2 consecutive head-up tilt-table tests without pharmacologic intervention (n = 20) or during isoproterenol infusion (n = 10). Patients were randomly assigned to 2 groups: 15 to placebo, and 15 to drug therapy (determined on the basis of serial pharmacologic tilting tests). Therapy was either atenolol (n = 7), dihydroergotamine (n = 2), domperidone (n = 2), cafedrine (n = 1), or elastic compression stockings, alone or in association with drugs (n = 3). During a mean of 10 +/- 7 months of follow-up, syncope recurred in 3 patients (20%) in the treatment group and in 4 (27%) in the placebo group; actuarial rates of absence of syncopal recurrences after 20 months were 70 and 67%, respectively. Thus, the outcome of either treated or untreated patients was favorable (with a low recurrence rate of syncope), and the usefulness of tilting-guided medical therapy remains uncertain.

The natural course of untreated sick sinus syndrome and identification of the variables predictive of unfavorable outcome.

We performed a prospective study in 35 untreated patients aged > or = 45 years, who had a mean sinus rate at rest of < or = 50 beats/min and/or intermittent sinoatrial block, and symptoms attributable to sinus node dysfunction. The patients were followed up for up to 4 years (mean 17 +/- 15 months). During follow-up, 20 patients (57%) had cardiovascular events that required treatment: 8 had syncope (23%); 6 had overt heart failure (17%); 4 patients had chronic atrial fibrillation (11%); and 2 patients had poorly tolerated episodes of paroxysmal tachyarrhythmias (6%). Actuarial rates of occurrence of all events were 35%, 49%, and 63%, respectively, after 1, 2, and 4 years. At univariate analysis, age > or = 65 years, end-systolic left ventricular diameter > or = 30 mm, end-diastolic left ventricular diameter > or = 52 mm, and ejection fraction < 55% were predictors of cardiovascular events. At multivariate analysis, age, end-diastolic diameter, and ejection fraction remained independent predictors of events. Actuarial rates of occurrence of syncope were 16%, 31%, and 31%, respectively, after 1, 2, and 4 years. Both univariate and multivariate predictors of syncope were history of syncope and corrected sinus node recovery > or = 800 ms. A favorable outcome was observed in the remaining 43% of patients. Thus, clinical cardiovascular events occur in most untreated sick sinus syndrome patients during long-term follow-up, even though a favorable course can be expected in 43% of patients. The outcome can be partly predicted on initial evaluation. In the patients with a favorable outcome, treatment can safely be delayed.

Value of head-up tilt testing potentiated with sublingual nitroglycerin to assess the origin of unexplained syncope.

This study was undertaken to assess the value of sublingual nitroglycerin administration during upright tilt as a simple practical test for the diagnosis of vasovagal syncope. To this purpose, 235 patients with syncope of unknown origin and no evidence of organic heart disease (110 men, mean age 52 +/- 20 years) and 35 asymptomatic control subjects underwent head-up tilt testing with nitroglycerin challenge. Patients and subjects were tilted at 60 degrees for 45 + 20 minutes; the initial 45 minutes were without medication and the final 20 minutes after 300 micrograms of sublingual nitroglycerin. During the drug-free phase of the test, 59 patients (25%) and no controls had a positive response. After drug administration, a positive response (syncope in association with sudden hypotension and bradycardia) occurred in 60 patients (26%) and in 2 controls (6%), whereas an exaggerated or false-positive response (minor or different symptoms in association with slowly increasing hypotension alone) was observed in 33 patients (14%) and in 5 controls (14%). We conclude that the sublingual nitroglycerin head-up tilt test is a useful tool to unmask the vasovagal origin of unexplained syncope in patients without organic heart disease. The addition of nitroglycerin to upright tilt allows the positive rate of passive tilting to be doubled (51% vs 25%) while maintaining a high specificity (94% vs 100%).

Carotid sinus syncope: the most frequent neurally mediated syncope in the elderly.

The present work reviews current literature and the authors' experience of carotid sinus syndrome (CSS), which is considered to be the most common cause of neurally mediated acute disorders of consciousness in the elderly. Although no definitive consensus about its nosology has yet been reached, most groups agree that three features fulfill the diagnosis: anamnestic presence of syncope or its minor equivalents, and their reproduction by carotid sinus massage associated with defined values of cardioinhibition or vasodepression or both. The technique for performing carotid sinus massage used by the authors is described; this manoeuvre seems very safe and reproducible as long as simple rules are followed, and it allows the classification of CSS types. The treatment of CSS is varied, according to several factors. No pharmacological therapy has yet been demonstrated to be effective. While severe cardioinhibitory forms require an appropriate pacing, vasodepressive ones and types with only minor symptoms show a more favourable natural history. Pacing is advised in mixed CSS with either frequent and invalidating relapses, or 'high risk' attacks (severe, abrupt, with major traumas, etc.). Finally, the protocol for choosing the adequate mode of pacing is illustrated. In most cases VVI is sufficient, but the decision requires a careful individual examination.

[General surgery in the octogenarian patient. One year's clinical experience]. / La chirurgia generale nel paziente ottuagenario. Esperienza clinica di un anno.

BACKGROUND: As the number of people over the age of 80 years is rapidly increasing, it may be expected that demand for surgical care for the elderly will also rise during the next decade thus contributing to a change in surgeon attitude. AIM OF THE STUDY: Because little literature is available on the surgical care requested by the over eighties, the aim of this study is to focus on the present surgical demand of the octogenarians in general surgical practice. METHODS: Two hundred-five admissions of 187 patients of above 80 years during one year were recorded retrospectively and statistical evaluation (Fisher exact test or Chi square test) of main clinical features was performed. RESULTS: The rate of surgical admission of octogenarians was 6.5% (205/3135). Half of the patients were admitted as emergencies (52.7%). This percentage was significantly higher (p < 0.000) than in < 80 year old patients (20.8%). The mortality rate for all admissions was 11.2%. In 65.4% of cases a surgical procedure was necessary with a correlated mortality rate of 8.2%. The mortality (2.9%) and morbidity (17%) rate in elective surgery were significantly lower (p = 0.0176 and p = 0.003 respectively) than in emergency surgery (13.6% and 42% respectively). Of all admissions 74.4% were uneventful and, in patients who underwent surgery, complications occurred in 29.8% with no statistically significant differences between patients with or without coexisting disease. The mean hospital stay was 11.4 days and in operated patients was 14.4 days. Almost the total number of patients could be sent home directly. CONCLUSIONS: In octogenarians, surgery is performed more frequently when a complication occurs, but this attitude should be changed because the mortality and morbidity rate are significantly higher. New standards of management and new resources will be requested for the elective surgical care of this rapidly increasing aged group of patients.

[Comparison of clinical and electrophysiologic characteristics of patients with occult and manifest atrioventricular accessory pathway]. / Confronto delle caratteristiche cliniche ed elettrofisiologiche dei pazienti con via accessoria atrioventricolare occulta e manifesta.

BACKGROUND: It is current opinion that concealed and manifest accessory pathways (APs) are indistinguishable with respect to their location and contribution to orthodromic reciprocating tachycardias. The aim of this study was to compare clinical and electrophysiological characteristics of two groups of patients. METHODS: Between January 1999 and June 2000, 42 consecutive patients underwent radiofrequency catheter ablation for paroxysmal atrioventricular reciprocating tachycardia attributable to a concealed AP. Their clinical and electrophysiological characteristics were compared with a group of 48 consecutive patients with manifest AP and supraventricular tachyarrhythmias. RESULTS: There were no differences regarding gender, the prevalence of heart disease and the age of onset of symptomatic tachycardias between the two groups. Compared to those with a manifest AP, the patients presenting with a tachyarrhythmia due to a concealed AP were older (48 +/- 15 vs 40 +/- 16 years, p < 0.05) and had a longer history of tachyarrhythmias (22 +/- 16 vs 13 +/- 13 years, p < 0.05). Atrial fibrillation was more frequent in patients with a manifest AP than in patients with a concealed AP (50 vs 9.5% respectively, p = 0.02). Atrioventricular reciprocating tachycardia was a cause of more hospitalizations (76 vs 35%, p = 0.01) and episodes of pre-syncope (47 vs 22%, p < 0.05) in the group of patients with a concealed AP. The anatomical site of concealed and manifest APs was significantly different: concealed APs were more frequently localized in the left side (93% left, 7% right), while manifest APs were seen in the left side in 64% of cases, in the right side in 29% and in the posteroseptal left + right region in 7% of cases. The retrograde electrophysiological properties and the inducibility of other types of reentrant arrhythmias were similar. Catheter ablation was similarly successful regardless of whether the AP was concealed or manifest, the rates of success being 91 and 88% respectively at the first attempt and with a similar number of energy applications (7 +/- 7 vs 10 +/- 9, p = NS). At a second attempt, the procedure was successful in 100 and 98% of cases respectively. Periprocedural complications occurred in 5% of patients with a concealed (1 ventricular fibrillation, 1 cerebral transient ischemic attack) and in 8% of patients with a manifest AP (2 pericardial effusion, 1 transient atrioventricular block, 1 anginal attack with spontaneous recovery) (p = NS). Complications occurred only for left-sided APs and were independent of the approach (transseptal or retrograde). Relapse of AP conduction was more frequent in the group of patients with a manifest than in those with a concealed AP (12 vs 5%), though not significantly. There were no late complications. CONCLUSIONS: Those patients presenting with a tachyarrhythmia due to a concealed AP, compared to those with a manifest AP, were older and had a longer history of tachyarrhythmia. Atrial fibrillation was more frequent in patients with manifest AP. Atrioventricular reciprocating tachycardia episodes were longer-lasting and caused more hospitalizations and more frequently pre-syncope in the group of patients with a concealed AP. Almost all concealed APs were localized in the left side. The retrograde electrophysiological properties were similar. The results of radiofrequency catheter ablation were comparable in both groups.

[Controversies in timing of preoperative staging of pancreatic carcinomas]. / Controversie nel timing per la stadiazione preoperatoria dei carcinomi pancreatici.

In recent years pancreatic cancer has shown an increasing incidence. Preoperative staging represents a main problem for its surgical management. Recent behaviour in the treatment of the disease led to considerably more encouraging results. The Authors describe the cases treated at the Dept. of Surgery of the University of Perugia and review the most important international reports on preoperative staging of pancreatic cancer.