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Our study analyzes imaging results in near-hanging to determine what neuroimaging workup is necessary. We evaluate GCS as a clinical predictor to help guide imaging choice. This is a retrospective study of patients from a level one trauma center and from the National Trauma Data Bank (NTDB). We classified injuries into categories based on the likelihood that CT played an important role in their diagnosis and management. We assessed whether a normal Glasgow Coma Scale (GCS) could exclude clinically important injuries. Chi square was used to test for significance for categorical variables. Multivariate logistic regression was used for multivariate analysis. CT showed structural brain findings in 0% of patients from our facility (local patients) and 11.7% of NTDB patients. Of local patients and NTDB patients, 1.4% and 6.6% had blunt cerebral vascular injury (BCVI) respectively. Of local patients and NTDB patients, 1.4% and 3.3% had a cervical spine fracture or dislocation, respectively. Mortality for patients with GCS 15 versus GCS

To complement and ensure redundancy in the endcap muon system of the Compact Muon Solenoid (CMS) detector and to extend the Resistive Plate Chamber (RPC) system coverage, improved RPCs (iRPCs) with either orthogonal layer strips with one-end electronics or single layer strips with two-end electronics providing more precise time measurement will be installed in the very forward pseudorapidity region of $$|\eta

International audience; The CMS experiment implements a two-level triggering system composed of Level-1, instrumented by custom-design hardware boards, and a software High Level Trigger. To cope with the more challenging luminosity conditions, a new Level-1 architecture has been deployed during run II. This new architecture exploits in a better way the redundancy and complementarity of the three muon subsystems: Cathode Strip Chambers (CSC), Drift Tubes (DT) and Resistive Plate Chambers (RPC). The role of each subsystem in the Level-1 Muon Trigger is described here, highlighting the contribution from the RPC system. Challenges brought by the HL-LHC environment and new possibilities coming from detector and trigger upgrades are also discussed.

A number of factors in Western society, including inflammatory diets, sedentary lifestyles, vitamin D deficiency and chronic psychological stress, are known to induce inflammation and to be associated with neuropsychiatric disorders. One factor that is emerging as a potential inflammation inducing factor is biota depletion, or loss of biodiversity from the ecosystem of the human body as a result of industrialization. Originally known as the "hygiene hypothesis", biota alteration theory describes the effects of biota alteration on the human immune system. Work on this topic has pinpointed depletion of helminths as a key loss to the body's ecosystem in Western society, and suggests that some exposure to helminths, ubiquitous prior to the modern era, may be necessary for normal immune system development. Socio-medical studies of humans "self-treating" with helminths as well as limited studies in animal models strongly suggest that helminth therapy may be a productive approach toward treating a range of neuropsychiatric disorders, including chronic fatigue, migraine headaches, depression and anxiety disorders. However, helminth therapy faces some daunting hurdles, including the lack of a financial incentive for development, despite a tremendous potential market for the organisms. It is argued that benevolent donation for early trials as well as changes in regulatory policy to accommodate helminth therapy may be important for the field to develop. It is hoped that future success with some high-profile trials can propel the field, now dominated more by self-treatment than by clinical trials, forward into the main stream of medicine.

As part of the Compact Muon Solenoid experiment Phase-II upgrade program, new resistive plate chambers will be installed in the region at low angle with respect to the beam collision axis, in order to improve the detection of muons with a low transverse momentum. High background conditions are expected in this region during the high-luminosity phase of the Large Hadron Collider, therefore an improved-RPC design has been proposed with a new front-end electronics to sustain a higher particle rate capability and better time resolution. A new technology is used in the front-end electronics resulting in low achievable signal detection of 1–20 fC. Crucial in the design of the improved-RPC is the capability of a two-dimensional readout in order to improve the spatial resolution, mainly motivated by trigger requirements. In this work, the first performance results towards this two-dimensional readout are presented, based on data taken on a real-size prototype chamber with two embedded readout planes with orthogonal strips. As part of the Compact Muon Solenoid experiment Phase-II upgrade program, new Resistive Plate Chambers will be installed in the forward region. High background conditions are expected in this region during the high-luminosity phase of the Large Hadron Collider, therefore an improved RPC design has been proposed with a new front-end electronics to sustain a higher rate capability and better time resolution. A new technology is used in the front-end electronics resulting in very low achievable thresholds of the order of several fC. Crucial in the design of the improved RPC is the capability of a two-dimensional readout in order to improve the spatial resolution, mainly motivated by trigger requirements. In this work, the first performance results towards this two-dimensional readout are presented, based on data taken on a real-size prototype chamber with two embedded orthogonal readout strips. Furthermore, dedicated studies of the muon cluster size as a function of the graphite resistivity are discussed.

Increased sugar consumption is a risk factor for the metabolic syndrome including obesity, hypertriglyceridemia, insulin resistance, diabetes, and nonalcoholic fatty liver disease (NAFLD). Carbohydrate responsive element-binding protein (ChREBP) is a transcription factor that responds to sugar consumption to regulate adaptive metabolic programs. Hepatic ChREBP is particularly responsive to fructose and global ChREBP-KO mice are intolerant to diets containing fructose. It has recently been suggested that ChREBP protects the liver from hepatotoxicity following high-fructose diets (HFrDs). We directly tested this hypothesis using tissue-specific ChREBP deletion. HFrD increased adiposity and impaired glucose homeostasis in control mice, responses that were prevented in liver-specific ChREBP-KO (LiChKO) mice. Moreover, LiChKO mice tolerated chronic HFrD without marked weight loss or hepatotoxicity. In contrast, intestine-specific ChREBP-KO (IChKO) mice rapidly lost weight after transition to HFrD, and this was associated with dilation of the small intestine and cecum, suggestive of malabsorption. These findings were associated with downregulation of the intestinal fructose transporter, Slc2a5, which is essential for fructose tolerance. Altogether, these results establish an essential role for intestinal, but not hepatic, ChREBP in fructose tolerance.

Chinese herbal medicine Jinlianqingre Effervescent Tablets (JET) are the recommended control measure for uncomplicated hand, foot, and mouth disease (HFMD) by the Ministry of Health of China. However, high-quality evidence to support this recommendation is limited. A total of 288 patients ranging in age from 1 to 13 years were randomly assigned to JET in combination with conventional therapy (mainly including the reduction of temperature by applying physical cooling paste or warm bathing), or conventional therapy with placebo group for 7 days. The objective was to test the hypothesis that JET combination therapy is more effective than conventional therapy for uncomplicated HFMD. A randomized, double-blind, placebo-controlled trial was designed. Our study showed that, compared with conventional therapy, the median time to fever resolution was significantly shorter in the JET combination therapy (8 vs. 80 h; p < 0.0001); the risk of fever resolution increased in the JET combination therapy [hazard ratio, 19.8; 95 % confidence interval (CI), 12.8 to 30.7]; the median healing time of rash or oral ulcer was significantly shorter in the JET combination therapy (14 vs. 74 h; p < 0.0001); and the median symptom score for skin or oral mucosa lesions improved more rapidly in the JET combination therapy during the follow-up period. The median duration of hospital stay was 6 days in the JET combination therapy and 7 days in the conventional therapy (p < 0.0001). No significant adverse events and complications were found in both groups. The addition of JET to conventional therapy reduced fever clearance time, healing time of skin or oral mucosa lesions, and duration of hospital stay in children with uncomplicated HFMD.

For measurements of the total hemispherical emittance e h of nonconducting materials, a problem of the thermal gradient produced in a sample specimen arises. An improved transient calorimetric technique to reduce the thermal gradient is proposed in this study. Glass sheets (borosilicate), semi-transparent for radiation, are selected as the nonconducting test material. The e h values of the glass sheets for various thicknesses are measured, and their results are presented as functions of thickness and temperature. The thermal gradients in the specimens are calculated by a three-dimensional analysis, and the corner effect due to them on the measured e h is estimated. It is shown that the proposed technique is useful for measuring the emittance e h of nonconducting materials.

Pulmonary Vein Arrhythmias. Introduction: Recent studies demonstrated that atrial arrhythmias may be generated within pulmonary veins. The purpose of this study was to compare the endocardial activation times at effective and ineffective ablation sites during radiofrequency catheter ablation of arrhythmias initiated or generated within pulmonary veins. Methods and Results: Twenty-one of 28 patients without structural heart disease underwent successful ablation of 23 arrhythmogenic foci within a pulmonary vein. Electrograms were recorded at 75 pulmonary venous sites and categorized into three groups: 23 successful ablation sites; 28 unsuccessful target sites within an arrhythmogenic pulmonary vein; and 24 sites within nonarrhythmogenic pulmonary veins. The endocardial activation time of premature depolarizations arising at successful target sites was significantly earlier than at other sites. During premature depolarizations, an endocardial activation time of -75 msec or earlier had a sensitivity of 83% and a specificity of 79% for identification of a successful ablation site. Endocardial activation times earlier than -100 msec were recorded only at successful ablation sites, and endocardial activation times later than -30 msec were recorded only at sites within nonarrhythmogenic pulmonary veins. The presence of a split potential during sinus rhythm or premature depolarizations was not a specific indicator of a successful ablation site. Conclusion: The endocardial activation times of premature depolarizations that arise within pulmonary veins and initiate atrial tachycardia/fibrillation are useful in identifying successful ablation sites.

Prior studies have demonstrated that sympathetic tone may influence the effects of adenosine on His-Purkinje automaticity, and that enhanced vagal tone may influence its effects on the sinus node. However, the interaction between autonomic tone and the effects of adenosine on the sinus node in humans remains unknown. Therefore, this study was designed to investigate the interaction between different states of autonomic tone and the bradycardiac response of the sinus node to adenosine. In 11 patients without structural heart disease who underwent a clinically indicated electrophysiology procedure, the sinus cycle length was measured before and after a 12-mg bolus of adenosine in the baseline state, during an infusion of 2 mcg/min of isoproterenol, after the administration of 0.2 mg/kg of propranolol, and again after the administration of 0.04 mg/kg of atropine. Adenosine significantly lengthened the sinus cycle length in the baseline state (760 +/- 165 vs 909 +/- 188 ms, P < 0.05), during isoproterenol infusion (516 +/- 67 vs 766 +/- 146 ms, P < 0.05), after propranolol (850 +/- 153 vs 914 +/- 143 ms, P < 0.05) and after the combination of propranolol and atropine (662 +/- 76 vs 801 +/- 121 ms, P < 0.05). The degree of lengthening in sinus cycle length was significantly greater (P < 0.05) during isoproterenol infusion (253 +/- 157 ms, or 51% +/- 40%) than in the baseline state (149 +/- 85 ms, or 20% +/- 12%), after propranolol (68 +/- 53 ms, or 8% +/- 8%), and after propranolol and atropine (140 +/- 110 ms, or 21% +/- 18%). The negative chronotropic effect of adenosine is influenced by autonomic tone. The effect of adenosine on the sinus node is accentuated by beta-adrenergic stimulation and unaffected by beta-adrenergic blockade or combined beta-adrenergic and cholinergic blockade.

A transient heating technique, improving the constant-rate-heating technique for the measurements of thermal diffusivities of metals, is proposed. For a physical model of a specimen to be measured, the transient heat-conduction equation was solved with some boundary conditions, and the solution obtained was used as the principle of the present transient heating technique for determining the thermal diffusivity of the specimen. Additionally, a thermal analysis was made to satisfy a boundary condition involved in the principle, that is, the condition of radiative thermal insulation at the two end surfaces of the specimen. To verify the validity of the present technique, the thermal diffusivity of iron, whose thermophysical properties are well-known, was measured with the same apparatus as used in our previous work, and the experimental results are discussed. Moreover, thermal diffusivities of thermocouple materials, namely, constantan, chromel, and alumel, were measured by the technique in the temperature range of 360 to 680 K.

The Accufix (Telectronics Pacing Systems, Englewood, Colo.) atrial active fixation pacemaker lead has a preformed J stiff retention wire than can fracture and erode through the atrium. We screened 85 patients with digital fluoroscopy and detected 18 (21%) lead fractures. Fourteen (16%) leads were successfully extracted by percutaneous techniques. The mean time for extraction and placement of a new atrial lead was 109 ± 53 min, and a lead > 1 year old but not in the presence of a fracture was associated with a significantly longer extraction time. There were two extraction complications. One patient had a fever following the extraction, and one patient had a focal sensory deficit 1 week after the extraction probably caused by a paradoxical embolus. Standard percutaneous extraction tools can be used for successful and safe removal of a fractured Accufix lead.

Previous studies have reported a significant morbidity and mortality associated with coronary artery bypass graft (CABG) surgery in conjunction with the placement of an implantable cardioverter defibrillator (ICD) with an epicardial lead system. In the absence of a control group, how significantly the component of concomitant placement of the ICD system contributes to these untoward outcomes remains unknown. The purpose of this study was to assess the short- and long-term complications in patients undergoing CABG surgery in conjunction with the placement of an ICD with epicardial leads and to compare these complications with those of patients who had only CABG surgery (control group). The study group (group A) consisted of 56 patients who underwent CABG surgery and placement of an ICD pulse generator with epicardial leads. A control group (group B) consisted of 56 patients who underwent CABG surgery only during the same time period. The two groups were matched for age, sex distribution, left ventricular function, surgical approach, number of bypass grafts per patient, bypass pump time, and length of follow-up period. The early mortality for group A was 7.1% versus 1.8% for group B (p > 0.05). The incidence of early morbidity (congestive heart failure, infection, supraventricular and ventricular arrhythmias) for groups A and B was similar (26.8% vs 25.0%, p > 0.05). The incidence of late mortality and morbidity (progression of congestive heart failure, recurrence of coronary events, chronic atrial fibrillation) for groups A and group B were 7.7% versus 5.5% (p > 0.05) and 23.1% versus 21.8% (p > 0.05), respectively. However, death caused by cardiopulmonary difficulties was more frequent in group A than group B (12.5% vs 1.8%, p < 0.05). With the availability of the nonthoracotomy lead system and the pulse generator capable of delivering biphasic shock waveform, to place such an ICD system at a later time after the CABG surgery appears to be the preferred approach to treat patients who need both surgical coronary revascularization and ICD.

Long RP Tachycardia, introduction: The purpose of this study is to describe a simple and reliuhle diagnostic maneuver that allows for the rapid differentiation of atypical AV nodal reentrant tachycardia (AVNRT) from other causes of long KP tachycardia. Lonf^ KP tachycardias may he caused by atypical AVNRT, orthodrnmic reciprocating tachycardia (ORT) involving a .slowly conducting retrograde accessory pathway, or atrial tachycardia. The dilTerentiation of atypical AVNRT from ORT or atrial tachycardia may be difficult, especially when the differential diagnosis includes a posteroseptal accessory pathway or an atrial tachycardia arising in the posteroseptal right atrium. Methods and Results: Twelve patients with atypical AVNRT, 21 with ORT, and 12 with an atrial tachycardia diagnosed using conventiitnal criteria were enrolled In this study. The atrialHis (AH) interval was measured at the His-hundle position during the tachycardia and during atrial pacing from the high right atrium at the tachycardia cycle length in the setting of sinus rhythm. In patients with atypical AVNRT, the mean AH interval was 69 msec ± 50 msec (± SD) longer during high right atrial pacing than during the tachycardia (P < 0.001). In 10 of 12 patients with atypical AVNRT, the AH interval during atrial pacing was more than 40 msec longer than the .\H interval measured during the tachycardia. In contra.st. In patients with ORT or atrial tachycardia, the difYerences in .AH interval hetween atrial pacing and tachycardia were never more than 20 and 10 msec, respectively. Conclusion: The difference in the AH interval between atrial pacing and the tachycardia allows a simple and rapid means of difierentiating atypical AVNRT from other types of long RP tachycardias. (J Cardiovasc Electrophysiol, Vol. 6, pp. 700-710. September 1995)

Coronary revascularization has been suggested as sole therapy for secondary prevention of sudden cardiac arrest associated with ischemia. The use of implantable defibrillators (ICD) in combination with coronary revascularization for this patient population is unclear. Among 412 consecutive patients receiving an ICD, 23 (6%) were identified as sudden cardiac arrest survivors who were noninducible with programmed stimulation and had unstable angina or ischemia on a functional study; they underwent successful coronary revascularization. During a follow-up of 34 ± 18 months, 10 (43%) of the 23 patients received ICD shocks (8 ± 8 per patient, range 1 to 22 shocks), and nine of the 10 patients had syncope/presyncope associated with at least one ICD discharge. Patients with ICD discharges were compared with those without ICD discharges, and no clinical characteristics were statistically different between the two groups. In conclusion, revascularization alone may be inadequate therapy for survivors of sudden cardiac arrest associated with ischemia who are noninducible with programmed stimulation, and clinical variables cannot predict which patients are likely to have recurrent malignant ventricular arrhythmias.

No prospective studies have compared sotalol and amiodarone during electropharmacologic testing. The purpose of this prospective, randomized study was to compare the electrophysiologic effects of sotalol and amiodarone in patients with coronary artery disease and sustained monomorphic ventricular tachycardia (VT). Patients with coronary artery disease and sustained monomorphic VT inducible by programmed stimulation were randomly assigned to receive either sotalol (n = 17) or amiodarone (n = 17). The sotalol dose was titrated to 240 mg twice daily over 7 days. Amiodarone dosing consisted of 600 mg 3 times daily for 10 days. An electrophysiologic test was performed in the baseline state and at the end of the loading regimen. An adequate response was defined as the inability to induce VT or the ability to induce only relatively slow hemodynamically stable VT. During the follow-up electrophysiologic test, 24% of patients taking sotalol and 41% of those taking amiodarone had an adequate response to therapy (p = 0.30). Amiodarone lengthened the mean VT cycle length to a greater degree than sotalol (28% vs 12%, p < 0.01). There were no significant differences in the effects of sotalol and amiodarone on the ventricular effective refractory period. In patients with coronary artery disease, amiodarone and sotalol are similar in efficacy in the treatment of VT as assessed by electropharmacologic testing. The effects of the 2 drugs on ventricular refractoriness are similar, but amiodarone slows VT to a greater extent than sotalol.

Iodixanol, a new ratio 6 nonionic iodinated contrast agent with an osmolality equal to serum, was compared with iohexol in a randomized, double-blind, parallel study. Two hundred patients undergoing elective diagnostic cardiac angiography were randomized to iodixanol (n = 101) or iohexol (n = 99). There were no differences noted between the 2 agents in the mean changes in systolic or diastolic blood pressure or heart rate during or immediately after any angiography. However, significantly more patients had a decrease in diastolic blood pressure of20 mm Hg during left coronary angiography with iodixanol. The only significant differences in any electrophysiologic parameter were slightly more PR prolongation during left coronary angiography with iodixanol and more ST-segment depression with iohexol during coronary angiography. Neither was clinically significant. Injection-associated discomfort occurred with both agents, but more patients experienced moderate to severe discomfort with iohexol (52%) than with iodixanol (17%) (p0.001). Only 1 potentially serious adverse event, ventricular fibrillation with iohexol, was considered related to contrast, and there were no differences noted between the agents. Overall, angiographic quality was equal with all angiograms being assessed as good or excellent in both groups (p = 0.885). In this low-risk population undergoing cardiac angiography, iodixanol is safe and effective without clinically important differences from iohexol. Additional studies in patients at high risk for complications should help further define the role of iodixanol in cardiac angiography.

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.

The natural history of patients with ischemic cardiomyopathy, asymptomatic nonsustained ventricular tachycardia, and negative electrophysiologic studies was assessed in a retrospective analysis of 55 consecutive patients. The results suggest that the prognosis for arrhythmic death in these patients is not necessarily benign.

The cost of definitive therapy was compared in 25 patients who underwent radiofrequency catheter ablation of accessory pathways in 1990 and 25 patients who underwent surgical ablation of accessory pathways in 1989. In the radiofrequency group, 23 of 25 patients had a single accessory pathway and the remaining 2 patients each had 2 accessory pathways. In the surgical group, 20 patients had a single accessory pathway and 5 patients each had 2 accessory pathways. The success rate was 96% in each group. The mean duration of hospitalization was 3 +/- 1 days in the radiofrequency group and 9 +/- 4 days in the surgical group (p less than 0.0001). All the cost data are expressed in fiscal year 1990/1991 dollar values. The total cost of therapy in the radiofrequency group was $14,919 +/- $6,740 compared with $53,265 +/- $12,755 in the surgical group (p less than 0.0001). The cost of radiofrequency ablation consisted of a hospital charge of $7,753 +/- $3,472 and physician fees of $7,166 +/- $3,439. The hospital charge included charges for use of the electrophysiology laboratory, hospital stay, electrocardiograms, echocardiograms and blood studies. The cost of surgery consisted of a hospital charge of $37,708 +/- $10,179 and physician fees of $15,557 +/- $3,149. The hospital charge in the surgical group included the costs of a baseline electrophysiology study, in-hospital care and a follow-up office visit. In conclusion, radiofrequency catheter ablation of accessory pathways results in a dramatic reduction in the cost of definitive therapy in patients with the Wolff-Parkinson-White syndrome.

Seventy-four patients (16 women, 58 men, age 58 ± 21 years, mean ± standard deviation) who received an implantable Cardioverter de/ibrillator (ICD) after experiencing a single episode of ventricular tachycardia or ventricular fibrillation were followed to determine if antiarrhythmic drug therapy affects the incidence of ICD discharges. Thirty-three patients (group A) were treated with an antiarrhythmic drug that was either untested or previously demonstrated during electropharmacological testing to be ineffective in suppressing the induction of ventricular tachycardia. Forty-one patients (group B) were not treated with an antiarrhythmic drug. There were no significant differences between the two groups in regards to age, sex, incidence of coronary artery disease, left ventricular function or the type of ICD pulse generator used. During a mean follow-up of 14 months for the entire cohort, 15 patients (46%) in group A and 18 patients (44%) in group B experienced at least one ICD shock. The time to the first appropriate shock (5 ± 5 months in both groups) and the frequency of ICD shocks (0.3 ± 0.2/month in group A vs 0.4 ± 0.5/month in group B) were similar in both groups. The incidence of syncope at the time of ICD discharge was higher in group A than group B patients (31% vs 5%, P < 0.05). In conclusion, antiarrhythmic drugs that are untested or have failed electropharmacological testing do not appear to reduce the probability of ICD discharge over a short-term (mean 14 months) follow-up in patients who have had only one clinical episode of VT/VF and may increase the risk of syncope during ICD discharge. Studies with a larger sample size and longer follow-up period will be needed to confirm these findings.

Background. We conducted this study to determine the feasibility of an abbreviated therapeutic approach to the Wolff-Parkinson-White syndrome or paroxysmal supraventricular tachycardia, in which the diagnosis is established and radiofrequency ablation carried out during a single electrophysiologic test. Methods. One hundred six consecutive patients were referred for the management of documented, symptomatic paroxysmal supraventricular tachycardias (66 patients) or the Wolff—Parkinson—White syndrome (40 patients). All agreed to undergo a diagnostic electrophysiologic test and catheter ablation with radiofrequency current. No patient had had such a test previously. Results. Among the 66 patients with paroxysmal supraventricular tachycardias, the mechanism was found to be atrioventricular nodal reentry in 46 (70 percent) (typical in 44 and atypical in 2), atrioventricular reciprocating tachycardia involving a concealed accessory pathway in 16 (24 percent), atrial tachycardia in 2 (3 percent), and no...

Ten consecutive patients with recurrent episodes of symptomatic, idiopathic, sustained monomorphic ventricular tachycardia (VT) originating in the right ventricle underwent an attempt at catheter ablation of the ventricular tachycardia. There were seven women and three men, with a mean age of 39 +/- 14 years (+/- SD). None of the patients had any evidence of structural heart disease. The VT had a left bundle branch block configuration and an inferior axis in each patient, and the mean cycle length was 313 +/- 75 msec. Based on the methods of induction of the VT and the response of the VT to verapamil, the VT mechanism was presumed to be reentry in six patients, triggered activity in three patients, and catecholamine-sensitive automaticity in one patient. Sites for ablation were guided by pace mapping, and an appropriate target site was identified in the right ventricular outflow tract in each patient. From one to three shocks of 100-360 J (mean total, 336 +/- 195 J) were delivered from a defibrillator between the tip of the ablation catheter (cathode) and a patch electrode on the anterior chest (anode). An electrophysiology test 7-9 days after ablation demonstrated that VT was still inducible in only one patient, who was treated with amiodarone. One other patient had a recurrence of VT 3 weeks after ablation and was treated with verapamil. Eight of 10 patients were not treated with antiarrhythmic medications and have had no episodes of symptomatic VT during 15-68 months of follow-up (mean follow-up, 33 +/- 18 months). There were no acute or long-term complications.(ABSTRACT TRUNCATED AT 250 WORDS)

Right ventricular refractory periods obtained using atrial and ventricular pacing with an atrioventricular (AV) interval of 160 ms were compared with those obtained with an AV interval of 0 ms in a group of 53 patients. The mean right ventricular effective refractory periods were longer at an AV interval of 160 ms than at an AV interval of 0 ms at pacing cycle lengths of 600 (mean 2.5 +/- 1.8 ms difference) and 400 ms (mean 3.8 +/- 2.4 ms difference; P less than 0.01). In a subset of 10 patients, left ventricular volumes measured by two-dimensional echocardiography demonstrated that pacing with an AV interval of 160 ms was associated with a higher end-diastolic volume and stroke volume than pacing with an AV interval of 0 ms (P less than 0.001). Autonomic blockade did not alter the relationship between AV interval and ventricular refractoriness. We conclude that 1) right ventricular refractory periods are shorter at an AV interval of 0 ms than at an AV interval of 160 ms; 2) these differences are not caused by changes in autonomic tone but are associated with differences in ventricular volumes; and 3) if precise determinations of ventricular refractoriness are desired, then the timing of atrial systole should be controlled by atrial pacing.

Inadequate drug plasma levels have been associated with the administration of phenytoin with enteral feedings through nasogastric (NG) tubes. It is demonstrated in this study that loss of phenytoin to tubing is a function of pH. Nonionized phenytoin is irreversibly bound to NG tubing from solution at the pH of enteral nutrient solutions while this is not the case for anionic phenytoin in unbuffered water or saline. In experiments pulsing phenytoin through glass vs NG tubing perfused with buffer at varying pH, reversible loss to tubing was observed at high pH while irreversible loss was observed at low pH. In addition, the irreversible loss of phenytoin was greater in NG tubing than glass particularly at low pH. It is suggested that in those cases where tubing is placed into the duodenum, inadequate gastrointestinal residence time for dissolution of phenytoin solid and suspension dosage forms coupled with irreversible drug loss from solution to NG tubing will result in decreased phenytoin absorption and subsequently lower drug plasma levels.

TOIVONEN, L.K., ET AL.: The Ventricular Excitability-Interval Relationship in Early Diastole in Humans: The Influence of the Electrode Configuration During Bipolar Stimulation. The purpose of this sludy was to determine (he relationship belween ventricular excitability and the extrastimuJus (S2) coupling interval in early diastole in humans. The influence of the electrode configuration during bipolar stimulation was examined. Ventricular strength-interval curves were constructed using an eight beat drive train at a cycle length 0/ 600 msec, 2-msec decrements in the S2 coupling interval, and 0.2-mA increments in the current intensity 0/ S2 at each coupling interval. A transient dip in ihe excitation threshold was observed in early diastole during bipolar pacing when the distal electrode was the anode in six of 17 patients {35%}. In contrast, this type of dip was not observed when the distal electrode was the cathode. The excitation threshold at the trough of the dip ranged from 1.0 to 2.2 mA. Unipolar strength-interval curves indicated that a dip occurred with anodal but not cathodal pacing. We postulated that the dip might inter/ere with the accurate determination of the ventricular ejfective refractory period hy resulting in transient loss of ventricular capture during decremental scanning of diastole with S2. A gap in ventricular capture was produced in all six patients who demonstrated a dip in the bipolar strength-interval curve by selecting an S2 current intensity that fell within the dip. In conclusion, the bipolar strength-interval curve may display an early diastolic dip in the excitation threshold, depending on the electrode conjiguration. During determination of the ventricular effective refractory period, if the stimulus intensity falls within the range of current intensities encompassed by the dip, a transient early diastolic gap in ventricular capture will he observed as diastole is scanned with S2. If this type of gap is not recognized, the ventricular effective refractory period may be overestimated. (PACE. Vol. 13, July 1990}

The yield of sustained, monomorphic ventricular tachycardia (VT) induced by programmed ventricular stimulation was compared, using basic drive trains of 400 ms, 600 ms and sinus rhythm, to identify the most efficient sequence of basic drive trains to use during programmed stimulation. Fifty-five patients with coronary artery disease and inducible sustained monomorphic VT not requiring countershock to terminate underwent 81 electrophysiology tests in which 1 to 3 extrastimuli were introduced during sinus rhythm and after basic drive trains of 600 and 400 ms. In 72 electrophysiology tests, sustained, monomorphic VT was induced at the right ventricular apex. The yield of VT using a drive cycle length of 400 ms was 63 of 72 (88%), compared to 46 of 72 (64%) when the drive cycle length was 600 ms, and 23 of 72 (32%) when the extrastimuli were introduced during sinus rhythm (p less than 0.001 for all pairwise comparisons). In 14 electrophysiology tests in which VT was not induced using a 400 ms basic drive cycle length at the apex, the yield of VT was higher using a 400 ms drive cycle length at a second right ventricular site (12 of 14) than with a 600 ms drive cycle length (3 of 12) or sinus rhythm (4 of 12) at the apex (p less than 0.05). The yield of sustained, monomorphic VT induced by 1 to 3 extrastimuli increases as the basic drive cycle length shortens. Whereas programmed stimulation is conventionally started during sinus rhythm or with a drive cycle length of 600 ms, the present results suggest that starting with a drive cycle length of 400 ms may be more efficient.

A wavelet image compression method using sub-block DCT is presented. The presented method is a hybrid type of DWT and DCT. The sub-block DCT is employed to the DWT-details. DWT-details have usually zero mean and small variance and hence the sub-block DCT method is very efficient. The size of sub-block for DCT is 8/spl times/8 pixel for level 1 DWT-details and 4/spl times/4 pixel for level 2 DWT-details. The simulation examples show that the presented method gives a better picture quality that of the usual JPEG method.

OBJECTIVES Using data from the Multicenter UnSustained Tachycardia Trial (MUSTT), we examined the factors used to select antiarrhythmic drug therapy and their impact on outcomes. BACKGROUND The MUSTT examined the use of programmed ventricular stimulation (PVS) to guide antiarrhythmic therapy in patients with coronary arteriosclerosis, left ventricular dysfunction and asymptomatic, unsustained ventricular tachycardia (VT). Trial outcomes may reflect factors used to select antiarrhythmic drug therapy. METHODS We compared subgroups of patients with inducible sustained VT randomized to PVS-guided antiarrhythmic therapy (n = 351), in particular those receiving PVS-guided antiarrhythmic drug therapy (n = 142) versus no antiarrhythmic therapy (controls, n = 353). RESULTS “Effective” antiarrhythmic drug therapy (i.e., the term “effective” was used to denote therapy that resulted in noninducible VT or hemodynamically stable induced VT) was found for 142 of the 351 patients (43%), most often at the first or second PVS session (125/142, 88%). Mortality among the 142 patients did not differ from that among control patients. Of these 142 patients, the PVS end point was noninducibility in 91 patients and stable VT in 51 patients. Mortality did not differ between these two groups either, but arrhythmia was numerically more frequent in the PVS-induced stable VT group. Mortality was greatest in the few patients receiving propafenone (unadjusted p = 0.07, adjusted p = 0.14 vs. controls), but mortality with all agents did not differ from that of controls, even after adjustment. CONCLUSIONS Even when presenting the results as favorably as possible, we found no benefit with PVS-guided drug therapy in patients with clinical unsustained VT who had inducible sustained VT. These findings are unaltered by using different end points for PVS or considering the response to individual drugs.

We studied the immediate reproducibility of the results of the head-up tilt-table test in elderly patients (age > or =60 years). Twenty-seven consecutive men underwent 51 tests. The overall reproducibility was 98%, including 92% of a positive test and 100% of a negative test. The finding of this study validates the use of intravenous pharmacologic intervention in the elderly population.

A density-corrected ultrasonic pneumotachometer designed specifically for horses (UF202) was evaluated and characterized with the aid of a custom-built apparatus. UF202 provided voltage outputs for airflow through and gas density within the flowhead. Baseline stability for flow channel output (VUF202) was < 0.35% full scale (FS), and VUF202 was linear over a range of +/- 50 l/s (R2 > or = 0.9976). Under optimal conditions, VUF202 accuracy was determined to be +/- 1.00% FS and repeatability was +/- 0.78% FS. VUF202 resolution was 24 ml/s. The rise time for VUF202 was 18 ms, and the -3-dB point was 18 Hz; digital compensation provided a flat frequency response to 32 Hz. VUF202 gain appeared to be stable over a period of 8 days. Density channel output (PUF202) was linear over a range of 1.11–1.23 g/l (R2 > or = 0.9645). PUF202 accuracy was calculated to be +/- 0.50% FS, and PUF202 repeatability was determined to be +/- 0.30% FS. Resistance of the flowhead was determined to be 0.013 cmH2O.l–1.s at a flow of 40 l/s. On the basis of this study, we conclude that UF202 should facilitate accurate measurement of breath-by-breath airflow of exercising horses.

Recognition of tachyarrhythmia by an implantable cardioverter-defibrillator (ICD) requires an intact rate-sensing lead. We retrospectively examined 266 consecutive patients requiring an ICD to characterize the incidence, clinical presentation, diagnosis, and management of a defective rate-sensing lead. To identify clinical parameters that may contribute to lead complications, we also assessed the effects of age, gender, type of rate-sensing lead, manufacturer of the lead, and surgeon. Over a follow-up period of 30 +/- 22 months (mean +/- standard deviation), a defective lead was found in 9 (3.4%) patients, in 9 (1.7%) of 514 leads over a period of 2 to 39 (mean 17 +/- 15) months after implantation. Except for 1 patient, in whom a lead fracture was incidently found during ICD generator replacement, these patients had multiple inappropriate shocks of recent onset. Clinical parameters were not helpful in identifying patients at risk for lead complication. An abnormal beeping signal obtained while the patients performed various maneuvers was helpful in confirming a defect. All of the defective leads were epicardial. These cases were managed by placement of a transvenous endocardial lead.

BACKGROUND Delivery of shocks within the right atrium has been reported to be more effective than conventional external shocks in converting atrial fibrillation (AF), but these two cardioversion techniques have never been compared prospectively. The purpose of this study was to compare the efficacies of external and internal cardioversion in patients with chronic AF unresponsive to prior attempts at electrical and/or pharmacological cardioversion. Low-dose amiodarone was used in all patients after cardioversion to suppress recurrences of AF. METHODS AND RESULTS One hundred twelve patients with AF of at least 1 month in duration were randomly assigned to undergo external cardioversion with 300-360-J shocks or internal cardioversion with 200-300-J shocks delivered through a standard electrode catheter within the right atrium. The patients were treated with amiodarone (200 mg/day 5-7 days/week) for 1 month before electrical cardioversion and afterward if the cardioversion was successful. The patients were evaluated at regular intervals during 1 year of follow-up. The efficacy of internal cardioversion was significantly greater than that of external cardioversion (91% versus 67%, p = 0.002). The only variable that was associated with the outcome of cardioversion was body weight. Among patients in whom sinus rhythm was restored, AF recurred as often after internal and external cardioversion; at 1 year of follow-up, 37% of patients in whom external or internal cardioversion had been effective were still in sinus rhythm. Patients who had undergone an attempt at electrical cardioversion before entry into this study were less likely to remain in sinus rhythm after cardioversion. The only complications of cardioversion were one instance of cerebral thromboembolism after external cardioversion and one instance of transient pulmonary edema after internal cardioversion. Therapy with amiodarone was discontinued because of an adverse drug effect in only three patients. CONCLUSIONS Internal cardioversion is more effective than external cardioversion in restoring sinus rhythm and is as safe as external cardioversion in patients with chronic AF. The recurrence rate of AF is the same after both types of cardioversion. If conventional electrical cardioversion is ineffective, internal cardioversion should be attempted. The combination of low-dose amiodarone and external or internal cardioversion may result in maintaining sinus rhythm long-term in patients with refractory AF.

BACKGROUND The purpose of this study was to report the results and complications of radiofrequency catheter ablation of accessory atrioventricular (AV) connections by using an abbreviated approach aimed at minimizing the duration of the procedure. METHODS AND RESULTS Two hundred fifty consecutive patients with the Wolff-Parkinson-White syndrome or paroxysmal supraventricular tachycardia involving a concealed accessory AV connection underwent catheter ablation with the use of radiofrequency current. In 179 of the 250 patients, catheter ablation was performed at the time of an initial electrophysiology test. Two hundred thirty-five patients had one accessory AV connection and 15 patients had two or more. One hundred eighty-three accessory AV connections were manifest and 84 were concealed. One hundred sixty-one were were located in the free wall of the left ventricle, 47 were in the right free wall, 44 were posteroseptal, 10 were anteroseptal, and five were intermediate test, and the ablation procedure was recorded for each patient, as was the total duration of fluoroscopy. A follow-up electrophysiology test was performed 2-3 months after the ablation procedure. Ninety-four percent of patients had all accessory AV connections successfully ablated and remained free of symptomatic tachycardia during a mean follow-up of 10 +/- 4 months. Two hundred nineteen patients (88%) had all accessory AV connections ablated during the initial attempt at catheter ablation. Mean duration of the entire procedure was 134 +/- 75 minutes. Procedure duration was longest in patients with multiple accessory AV connections, shortest in patients with intermediate septal accessory AV connections, and similar in all other locations. A nonfatal complication occurred in nine patients (4%). CONCLUSIONS The results of this study indicate that catheter ablation of accessory AV connections with radiofrequency current can be performed safely and expeditiously in a majority of patients and confirm in a large series the feasibility of catheter ablation at the time of an initial diagnostic electrophysiology test. This abbreviated therapeutic approach avoids the need for electropharmacological testing, long-term antiarrhythmic drug therapy, and surgical therapy in the majority of patients with the Wolff-Parkinson-White syndrome or with symptomatic tachycardias involving accessory AV connections.

To evaluate the effect of sympathetic activation on the efficacy of the implantable cardioverter-defibrillator (ICD) in converting ventricular tachycardia (VT) or ventricular fibrillation (VF), 32 patients who received an ICD because of life-threatening VT/VF underwent 1 week postimplant ICD testing both before and after infusion of 25 (16 patients) or 50 (16 patients) ng/kg/min of epinephrine for greater than or equal to 12 minutes. These infusion rates are known to result in plasma epinephrine concentrations comparable to mild-moderate stress. The patients' mean age was 63 +/- 10 years; 26 had coronary artery disease, 2 had dilated cardiomyopathy and 4 had no evidence of structural heart disease. VT and VF were induced in 16 patients each by programmed stimulation or alternating current. Among the 16 patients with VT, the first ICD discharge (26 to 30 J) was effective in 15 patients in the baseline state and in all 16 patients during epinephrine infusion. Among patients with VF, the first ICD discharge (26 to 30 J) terminated VF in all patients in the baseline state, compared with 12 of 16 patients during epinephrine infusion (p less than 0.05). In 4 patients, VF was terminated during epinephrine infusion only by the second or third ICD discharge (30 J). In conclusion, physiologic increases in the plasma epinephrine concentration may increase the number and energy of shocks needed to terminate VF.

Fifteen consecutive patients with drug-refractory, recurrent, sustained, monomorphic ventricular tachycardia and a history of remote myocardial infarction underwent catheter ablation of ventricular tachycardia. Shocks of 100 to 300 J were delivered to sites at which pacing during ventricular tachycardia resulted in concealed entrainment, in which the ventricular tachycardia accelerated to the pacing rate, there was a long stimulus to QRS interval and there was no change in the configuration of the QRS complex during pacing at several rates compared with the configuration during ventricular tachycardia, thus identifying a zone of slow conduction in the reentrant circuit. Concealed entrainment was demonstrated in nine (60%) of 15 patients, and the stimulus to QRS intervals were 90 to 400 ms. At sites of concealed entrainment, the endocardial activation time relative to the QRS complex during ventricular tachycardia ranged from -125 to +50 ms, the timing of the local electrogram relative to the QRS complex was the same during entrainment as during ventricular tachycardia and the pace map during sinus rhythm was discordant with that of the ventricular tachycardia in seven patients. In the six patients in whom a site of concealed entrainment could not be identified, the target site for ablation was selected on the basis of identification of an isolated mid-diastolic potential, activation mapping and pace mapping. The mean (+/- SD) cumulative number of joules delivered to the target site was 306 +/- 140. A successful long-term clinical outcome was achieved in 9 of the 15 patients (mean follow-up 20 +/- 7 months). The clinical success rate was the same whether the target site was selected on the basis of concealed entrainment (five of nine, 56%) or on the basis of the other mapping techniques (four of six, 67%). In conclusion, the responses to pacing suggest that sites at which there is concealed entrainment may be located within a zone of slow conduction in the ventricular tachycardia reentry circuit, although not necessarily in an area critical for the maintenance of reentry. The long-term clinical efficacy of catheter ablation targeted to sites of concealed entrainment is about 60%, similar to the results achieved when conventional mapping techniques are used.

BACKGROUND This study compared the sensitivity, specificity, and efficiency of a "conventional" and "accelerated" programmed stimulation protocol in 293 patients with coronary artery disease who had a history of sustained or nonsustained monomorphic ventricular tachycardia (VT). METHODS AND RESULTS In the conventional protocol, one and two extrastimuli were introduced during sinus rhythm and during basic drive trains at cycle lengths of 600 and 400 msec at the right ventricular apex and then at the outflow tract or septum. In the accelerated protocol, one, two, and then three extrastimuli were introduced at each of three basic drive train cycle lengths (350, 400, and 600 msec) at the right ventricular apex; the procedure was repeated at a second right ventricular site. Six hundred thirty-four electrophysiological tests were performed using one of these two protocols either in the baseline state (293 tests) or during drug testing (341 tests). The yield of sustained, monomorphic VT was 89% with the conventional protocol and 92% with the accelerated protocol during baseline tests in patients who had a history of sustained VT (p = 0.05); 20% and 34%, respectively, during baseline tests in patients with a history of nonsustained VT (p = 0.06); and 70% and 77%, respectively, during drug testing (p = 0.2). To induce sustained, monomorphic VT, 10.1 +/- 5.0 (mean +/- SD) protocol steps and 14.4 +/- 8.7 minutes were required with the conventional protocol, compared with 4.0 +/- 3.7 steps and 5.6 +/- 6.1 minutes with the accelerated protocol (p less than 0.001 for each comparison). Among the tests in which sustained, monomorphic VT was induced, sustained polymorphic VT or ventricular fibrillation was induced more often with the conventional protocol (3.6%) than with the accelerated protocol (0.9%, p = 0.05). CONCLUSIONS The efficiency of programmed stimulation can be improved by the early use of a basic drive train cycle length of 350 msec and three extrastimuli. Compared with a conventional stimulation protocol, the accelerated protocol used in this study reduces the number of protocol steps and duration of time required to induce monomorphic VT by an average of more than 50% and improves the specificity of programmed stimulation without impairing the yield of monomorphic VT.

This study examines the changes in pacing threshold and R- or P-wave amplitude during the first 30 minutes after implantation of tined and screw-in leads. The leads examined were those of 1 manufacturer (Medtronic) and consisted of 3 ventricular pacing leads (model numbers 6957 unipolar screw-in [11 patients], 6961 unipolar tined [12 patients] and 6962 bipolar tined [7 patients]) and 1 atrial lead (model number 6957J unipolar screw-in [10 patients]). After optimal lead position was obtained fluoroscopically in the right ventricular apex or right atrium, the pacing threshold and R- or P-wave amplitudes were measured at 5-minute intervals for 30 minutes. The acute ventricular pacing threshold with the screw-in lead was significantly higher than with the tined lead (0.84 +/- 0.17 vs 0.58 +/- 0.15 volts; p less than 0.001). There was a significant (p less than 0.001) acute decrease in the ventricular pacing threshold with both lead types, with the maximum decrease occurring 5 minutes after lead implantation. There was a significant acute increase in R-wave size with the ventricular screw-in lead that peaked 20 minutes after lead implantation (11.9 +/- 3.0 to 14.7 +/- 4.1 mV; p less than 0.001). The atrial screw-in lead behaved in a manner identical to its counterpart in the ventricle. In conclusion, there are acute changes in the pacing threshold and R- or P-wave amplitude obtained with tined and screw-in pacing leads.(ABSTRACT TRUNCATED AT 250 WORDS)

In retrospective studies, quinidine-induced proarrhythmia and excessive lengthening of the OT interval have been described to occur in 5–10% of patients (pts). There are, however. no prospective studies. Therefore, the purpose of this study was to prospectively assess the acute effects of quinidine on the QT interval and on the incidence of proarrhythmic events in hospitalized pts. using daily 12-lead ECG's and continuous telemetric monitoring. Clinical data included gender, age, body surface area, left ventricular ejection fraction (LVEF), etiology of heart disease, congestive heart failure class, Q-wave infarction pattern, indication for quinidine, quinidine and potassium serum levels, and use of a diuretic, digoxin or an antiarrhythmic agent. Pts were followed until time of discharge. Quinidine was initiated in 35 pts (18 M; 17 F) for supraventricular (n = 22) or ventricular (n = 13) arrhythmias 19 pts had an ischemic, 6 had a nonischemic, and 3 had a valvular cardiomyopathy; 5 had hypertensive and 2 had no heart disease. The mean age was 63 ± 13 years. the mean LVEF was 0.38 ± 0.15 and the mean functional class was 2.0 ± 1.1. The mean quinidine level was 2.7 ± 1.2 μ g/ml. The QT interval increased from 388 ± 61 to 499 ± 70 msec (p l 0.01) and the QTc increased from 445 ± 61 to 543 ± 60 msec (p l 0.005). 11 pts (31%) developed a QTc g 550 msec. Torsade de pointes (n = 3) or other ventricular proarrhythmic events (n = 3) occurred in 6 pts (17%). The pts experiencing torsade de pointes were female pts with a mean LVEF of 0.24 and a QTc of 610 to 650 msec. Female gender (p = 005), younger age (p = 0.04), lower LVEF (p = 0.01). and an increased baseline QTc interval (p l 0.005) were statistically associated with proarrhythmia. Proarrhythmic events occurred on day 2.3 ± 1 of quinidine therapy (range: 1–4). In conclusion in this prospective study of hospitalized pts, quinidine resulted in lengthening of the QTc inteNal beyond 550 msec in 31% of the pts and in a 17% incidence of clinically significant ventricular proarrhythmia. Proarrhythmia was statistically associated with female gender, decreased LVEF and increased baseline QTc interval. The results of this prospective study indicate that the incidence of quinidine-induced proarrhythmia and excessive QT prolongation may be higher than the 5–10% incidence previously reported in retrospective studies.

OBJECTIVE: To determine the incidence of loss of consciousness occurring in association with shocks delivered by automatic implantable cardioverter-defibrillators (AICD) in patients who had undergone implantation as treatment for ventricular tachycardia or ventricular fibrillation. DESIGN: Cohort study. SETTING: Two major tertiary medical care facilities. PATIENTS: A total of 180 patients who had undergone implantation of an AICD for treatment of ventricular tachycardia or ventricular fibrillation. INTERVENTION: Implantation of an AICD that delivered only high-energy shock. MEASUREMENTS: During a mean (+/- SD) follow-up period of 16 +/- 12 months, the incidence of loss of consciousness occurring in association with spontaneous AICD shocks was determined. Various clinical factors were analyzed to identify predictors of loss of consciousness that occurred during AICD shocks. MAIN RESULTS: Of the 180 patients who received an AICD, 106 patients (59%) experienced AICD shocks during follow-up. Sixteen of the 180 patients (9%) experienced loss of consciousness; 13 of these 16 patients had syncope and 3 died suddenly, in association with AICD shocks. The absence of syncope during one AICD shock did not always predict the absence of syncope during subsequent shocks. Syncope could not be predicted by age, sex, history of syncope, left ventricular function, type of underlying heart disease, electrophysiologic findings, rate of ventricular tachycardia, antiarrhythmic medications, and type of pulse generator implanted. CONCLUSIONS: Patients with sustained ventricular tachycardia or ventricular fibrillation who receive an AICD that delivers only high-energy shock therapy are at moderate risk for experiencing loss of consciousness during AICD shocks. No clinical variables were found to be predictors of syncope. Therefore, driving and other activities that require patients to be extra vigilant should not be assumed to be safe after implantation of an AICD that delivers only high-energy shock. Language: en

Evidence of an atriofascicular accessory pathway has not been reported previously. In the patient presented in this case report, an electrophysiology study demonstrated a constant left bundle branch block QRS configuration despite varying degrees of ventricular preexcitation, in association with a constant artrioventricular interval during incremental atrial pacing and programmed atrial stimulation. The presence of an atrioventricular, nodoventricular, nodofascicular, and atrial-His accessory pathway was ruled out. The findings are best explained by the presence of an underlying left bundle branch block and an atriofascicular accessory pathway connecting the atrium and right bundle. The atriofascicular accessory pathway was a passive bystander during an atrial tachycardia and was not directly involved in the generation of the tachycardia. To our knowledge, this is the first report of an atriofascicular accessory pathway.

The electrophysiologic effects of circulating epinephrine in humans were examined in four study groups of 10 subjects each. In 10 subjects without structural heart disease (Group 1) and in 10 patients with coronary disease or dilated cardiomyopathy (Group 2) epinephrine infusion at 25 and 50 ng/kg body weight per min for 14 min resulted in an elevation of the plasma epinephrine concentration in the physiologic range. In both groups it produced a dose-dependent decrease in the effective refractory period of the atrium, atrioventricular (AV) node and ventricle and improvement in AV node conduction. Epinephrine facilitated the induction of sustained ventricular tachycardia in 3 of the 20 subjects. In Group 3, a beta-adrenergic blocking dose of propranolol was added to the infusion of 50 ng/kg per min of epinephrine. Propranolol not only reversed the effects of epinephrine, but also lengthened these variables compared with baseline values. In Group 4, propranolol was administered first, followed by 50 ng/kg per min of epinephrine. Propranolol alone slowed AV node conduction and mildly prolonged the refractory periods. In the presence of betablockade, epinephrine had no effect on AV node properties but resulted in a lengthening of the atrial and ventricular effective refractory periods. In conclusion, epinephrine in physiologic doses shortens the effective refractory period of the atrium, AV node and ventricle, improves AV node conduction and may facilitate the induction of sustained ventricular tachycardia. The overall electrophysiologic effects of epinephrine result from stimulation of beta-receptors. Stimulation of alpha-receptors by epinephrine has no effect on the AV node but prolongs the effective refractory period of the atrium and ventricle, partially offsetting the shortening of refractory periods mediated by beta-receptor stimulation.

The antiarrhythmic and antifibrillatorv effects of flecainide acetate during the early postinfarction period were evaluated in a conscious canine model of sudden cardiac death. Ventricular tachycardia remained inducible early after infarction in eight of nine dogs receiving an intravenous loading dose of flecainide (2.0 mg/kg body weight) and seven of eight dogs receiving saline vehicle. In both the drug and vehicle groups, there was no significant change in the ventricular refractory period or in the cycle length of the induced ventricular tachycardia. With a maintenance intravenous infusion of flecainide, 1.0 mg/kg per h for 4 hours, the subsequent occurrence of acute posterolateral ischemia resulted in the development of ventricular fibrillation and sudden death in seven of eight flecainide-treated and eight of eight vehicle-treated dogs. Seven additional postinfarction dogs with noninducible tachycardia during pretreatment programmed stimulation, and thereby considered to be at “low risk” for the development of ischemic ventricular fibrillation, were also given flecainide in an intravenous loading and maintenance dosing regimen. The subsequent occurrence of posterolateral ischemia resulted in the development of ventricular fibrillation in three of these seven dogs. These findings suggest that flecainide acetate may not possess pharmacologic properties useful in managing ventricular tachycardia or in preventing ischemic ventricular fibrillation in the presence of recent myocardial damage.

The results of 206 programmed ventricular stimulation studies performed in 130 patients (100 men and 30 women, mean age 62 +/- 12 years, +/- standard deviation) were examined prospectively to determine the sequelae of nonsustained polymorphic ventricular tachycardia (VT) induced during programmed ventricular stimulation. The clinical indication for the electrophysiologic study was either documented monomorphic VT or unexplained syncope. The pacing protocol included 2 right ventricular pacing sites, 2 basic drive cycle lengths and up to 3 extrastimuli. In 111 studies, nonsustained polymorphic VT was induced and with continuation of the programmed stimulation protocol, sustained monomorphic VT was induced in 48 studies (43%) and polymorphic VT was induced in 13 studies (12%). Overall, sustained monomorphic VT was induced in 110 studies and sustained polymorphic VT in 18 studies. The incidence of nonsustained polymorphic VT preceding the induction of sustained polymorphic VT was significantly greater than the incidence of nonsustained polymorphic VT preceding the induction of sustained monomorphic VT (72 vs 44%, p less than 0.05). Nonsustained polymorphic VT is not a useful predictor of the outcome of programmed ventricular stimulation. The use of nonsustained polymorphic VT as an endpoint for stimulation would be likely to improve the specificity of programmed ventricular stimulation by limiting the induction of sustained nonclinical arrhythmias that require countershock, but at the cost of significantly impairing the yield of monomorphic VT.

Studies that used prolonged contrast media infusion in canine arteries have generated controversy regarding the arrhythmogenic potential of low osmolarity, nonionic contrast agents. In order to establish the relative safety of these agents in the more typical setting of bolus injections, 4 ml intracoronary bolus injections of Hypaque-76 (n = 54), Iohexol-350 (n = 51), and Iohexol-140 (n = 51) were given in random order to 10 anesthetized, open-chest dogs undergoing programmed cardiac stimulation. Hemodynamics and electrocardiogram were monitored during stimulation, both during and for 2 minutes after the end of contrast infusion. Occurrence of evoked single and coupled premature ventricular contractions and nonsustained ventricular tachycardia did not differ statistically among agents. Sustained ventricular tachycardia (five episodes) and ventricular fibrillation (seven episodes) occurred only after Hypaque-76 injections (p less than 0.002). These results differ from those in studies that use continuous contrast infusion and suggest that low osmolarity nonionic contrast agents are as safe as high osmolarity nonionic contrast media. Both appear safer than ionic contrast material.

Forty-eight patients with a posteroseptal accessory atrioventricular (AV) connection underwent catheter ablation of the accessory AV connection with 200-400 J shocks delivered by a standard defibrillator. Cathodal shocks were delivered through the proximal pair of electrodes of a 6F quadripolar electrode catheter positioned in the coronary sinus such that the proximal electrodes straddled the ostium (12 patients) or the third electrode from the tip was at the ostium (36 patients). A 16-cm patch electrode positioned on the back or anterior chest served as the anode. Two to 4 shocks were delivered (total, 635 +/- 198 J, mean +/- SD). The cathether ablation procedure was clinically successful in eliminating symptomatic tachycardias in in 32 of 48 patients (67%) during a mean follow-up of 26 +/- 19 months. A long-term follow-up electrophysiology study was performed in 27 of the 32 patients who had a successful clinical outcome, and this showed that conduction through the accessory AV connection was completely absent in 25 patients and present but impaired in two patients. The success rate was significantly higher in patients with a concealed accessory AV connection (13 of 13, 100%) than in patients with manifest preexcitation (19 of 35, 54%; p less than 0.001). Among the 12 patients in whom the proximal electrodes of the ablation catheter straddled the ostium of the coronary sinus, one patient developed cardiac tamponade requiring needle pericardiocentesis; there were no instances of cardiac tamponade among the 36 patients in whom the third electrode from the tip was at the ostium of the coronary sinus. Other complications were AV block requiring a permanent pacemaker and transient atrial tachycardia in one patient each and an asymptomatic pericardial effusion in three patients. In conclusion, with the catheter ablation technique described in this study, a successful clinical outcome may be achieved in approximately two thirds of patients who have a posteroseptal accessory AV connection, and the risk of serious complications is low. This technique is particularly well suited to patients with a concealed posteroseptal accessory AV connection, in whom the success rate is higher than in patients with manifest preexcitation.

This prospective study compared the yield of programmed ventricular stimulation with single and double extrastimuli during an infusion of isoproterenol with that of programmed stimulation with triple extrastimuli. The subjects of this study were 58 patients who underwent programmed stimulation and did not have inducible ventricular tachycardia (VT) with single or double extrastimuli at two basic drive cycle lengths and at two right ventricular sites; 17 patients had a history of uniform VT unrelated to exercise, and 41 had no history of documented or suspected VT or ventricular fibrillation (VF). Programmed stimulation was performed with triple extrastimuli at both right ventricular sites. Isoproterenol was infused as a dose titrated to increase the sinus rate by 25% or to a rate of 100 beats/min, whichever was greater, and stimulation then was repeated with single and double extrastimuli. Among the 17 patients with a history of uniform VT, the clinical VT was induced by three extrastimuli in five patients (29%) and by two extrastimuli during isoproterenol infusion in six patients (35%, p greater than 0.05). Among the total study population of 58 patients, nonclinical multiform VT or VF was induced by three extrastimuli in 29 patients (50%), and by two extrastimuli during isoproterenol infusion in 15 patients (26%, p less than 0.05). Therefore stimulation with two extrastimuli during isoproterenol infusion has the same probability of inducing a clinical form of VT as does stimulation with extrastimuli, but the former has a significantly lower probability of inducing nonclinical multiform VT and VF.