Ground beetle (Coleoptera: Carabidae) diversity, activity density, and community structure in a diversified agroecosystem.

Diversity and abundance of ground beetles (Coleoptera: Carabidae) can be enhanced in vegetable and field intercropping systems, but the complexity of polycultures precludes the application of generalized assumptions of effects for novel intercropping combinations. In a field experiment conducted at Lacombe and Ellerslie, Alberta, Canada, in 2005 and 2006, we investigated the effects of intercropping canola (Brassica napus L.) with wheat (Triticum aestivum L.) on the diversity and community structure of carabid beetles, and on the activity density responses of individual carabid species. Shannon-Wiener diversity index scores and species evenness increased significantly as the proportion of wheat comprising total crop plant populations increased in one site-year of the study, indicating a positive response to enhanced crop plant species evenness in the intercrops, and in that same site-year, ground beetle communities in intercrops shifted to more closely approximate those in wheat monocultures as the percentage of wheat in the intercrops increased. Individual carabid species activity densities showed differing responses to intercropping, although activity densities of some potential root maggot (Delia spp.) (Diptera: Anthomyiidae) predators were greater in intercrops with high proportions of wheat than in canola monocultures. The activity density of Pterostichus melanarius (Illiger), the most abundant species collected, tended to be greater in canola monocultures than high-wheat intercrops or wheat monocultures. We conclude that intercrops of canola and wheat have the potential to enhance populations of some carabid species, therefore possibly exerting increased pressure on some canola insect pests.

Effects of canola-wheat intercrops on Delia spp. (Diptera: Anthomyiidae) oviposition, larval feeding damage, and adult abundance.

Reductions in oviposition and subsequent damage by root maggots (Diptera: Anthomyiidae, Delia spp.) to brassicaceous crops in the presence of nonhost plants has been demonstrated, but such investigations have not been conducted using intercrops of species commonly grown in the large-scale agricultural production systems of western Canada. A field experiment was conducted at three sites in Alberta, Canada, in 2005 and 2006 to determine interactions between root maggots and the various proportions of canola (Brassica napus L.) making up the total crop plant populations in intercrops with wheat (Triticum aestivum L.). The effect of a neonicotinoid seed treatment also was investigated. Root maggot damage to canola taproots decreased with increasing proportions of wheat in the intercrops. The presence of wheat in the intercrops had little effect on root maggot adult abundance in any single site-by-year combination or when data were combined over all sites and years, with different Delia species and sexes responding differently. Similarly, per plant root maggot egg populations were unaffected by intercropping, although egg populations were reduced on a per unit land area basis in intercrops compared with monocultures. Insecticidal seed treatment did not affect root maggot egg populations or canola root damage. Variable abundances and phenologies of the principal root maggot species infesting canola at different sites and years may influence their responses to canola-wheat intercrops. Intercropping canola and wheat may provide an opportunity for reducing crop damage from root maggot attack without compromising environmental sustainability.

Effect of verapamil on immediate recurrence of atrial fibrillation.

INTRODUCTION: The purpose of this study was to assess the effect of verapamil on immediate recurrences of atrial fibrillation occurring after successful electrical cardioversion. METHODS AND RESULTS: The effect of verapamil on the recurrence of atrial fibrillation within 5 minutes after successful transthoracic cardioversion was assessed in 19 (5%) of 364 patients undergoing electrical cardioversion. The mean duration of atrial fibrillation was 4.44+/-3.0 months. In the 19 patients, cardioversion was successful after each of three consecutive cardioversion attempts per patient; however, atrial fibrillation recurred 0.4+/-0.3 minutes after cardioversion. Verapamil 10 mg was administered intravenously and a fourth cardioversion was performed. Cardioversion after verapamil was successful in each patient, and atrial fibrillation did not recur in 9 (47%) of 19 patients (P < 0.001 vs before verapamil). In the remaining 10 patients in whom atrial fibrillation recurred, the duration of sinus rhythm was significantly longer compared with before verapamil (3.6+/-2.4 min, P < 0.001). The density of atrial ectopy occurring after cardioversion was significantly less after verapamil (21+/-14 ectopic beats per min) compared with before verapamil (123+/-52 ectopic beats per min, P < 0.001). CONCLUSION: Among patients with immediate recurrence of atrial fibrillation after electrical cardioversion, acute calcium channel blockade by verapamil reduces recurrence of atrial fibrillation and extends the duration of sinus rhythm.

Analysis of the pattern of initiation of sustained ventricular arrhythmias in patients with implantable defibrillators.

INTRODUCTION: The purpose of this study was to analyze the pattern of initiation of sustained ventricular arrhythmias in patients with varying types of underlying structural heart disease. METHODS AND RESULTS: The study group consisted of 90 patients with an implantable cardioverter defibrillator. Cardiovascular diagnoses included coronary artery disease in 64 patients (71%). The patients were divided into four groups based on the type and severity of structural heart disease. Two hundred sixty episodes of sustained ventricular arrhythmias were analyzed. The mean coupling interval of the initiating beat of all ventricular arrhythmias was 523 +/- 171 msec. The coupling interval of the initiating beat was longer in patients with impaired ventricular function, particularly those with nonischemic dilated cardiomyopathy. The prematurity index was similar regardless of the type of underlying structural heart disease. However, the prematurity index was shorter in patients with polymorphic ventricular tachycardia (VT) compared to those with monomorphic VT. A pause was observed more commonly before the onset of polymorphic VT/ventricular fibrillation than sustained monomorphic VT. Two hundred twenty-two (85%) of the arrhythmia episodes were initiated by a late-coupled premature beat, 33 (13%) were initiated by an early-coupled premature beat, and 5 episodes (2%) were initiated with a short-long-short sequence. The pattern of initiation of the ventricular arrhythmias was similar in all patient groups and for both monomorphic and polymorphic tachycardias. CONCLUSION: These findings demonstrate that sustained ventricular arrhythmias typically are initiated by late-coupled ventricular premature depolarizations, regardless of the type or severity of underlying structural heart disease or resultant arrhythmia.

Intracardiac echocardiography to guide transseptal left heart catheterization for radiofrequency catheter ablation.

INTRODUCTION: The purpose of this study was to assess the feasibility and safety of intracardiac echocardiography to guide transseptal puncture for radiofrequency catheter ablation. METHODS AND RESULTS: Transcatheter intracardiac echocardiography (9 MHz) was utilized to guide transseptal puncture in 53 patients undergoing radiofrequency catheter ablation. The anatomy and relationship of intra- and extracardiac structures were visualized with the ultrasound transducer positioned at the fossa ovalis. The tip of the transseptal dilator and tenting of the fossa ovalis and the left atrial wall were simultaneously visualized in a single ultrasound image in all patients. With maximum tenting of the fossa ovalis, the mean distance from the fossa to the left atrial wall was 11.9 +/- 5.8 mm (range: 1.8 to 25.6 mm). In four patients (8%), the tented fossa ovalis abutted the left atrial wall and the transseptal dilator was redirected with ultrasound guidance. Puncture of the interatrial septum was achieved through the fossa ovalis in each patient and required a single attempt in 51 patients (96%). The mean number of punctures per patient was 1.1 +/- 0.4. The mean time to perform transseptal catheterization was 18.2 +/- 6.8 minutes. There were no complications. CONCLUSION: Intracardiac echocardiography delineated the anatomy of intra- and extracardiac structures not identified with fluoroscopy and simplified correct positioning of the transseptal dilator, puncture of the fossa ovalis, and cannulation of the left atrium in a timely and uncomplicated fashion.

A quantitative fluoroscopic comparison of the coronary sinus ostium in patients with and without AV nodal reentrant tachycardia.

INTRODUCTION: The purpose of this study was to perform a quantitative fluoroscopic analysis of the coronary sinus ostium and its relationship to the His bundle in patients with and without AV nodal reentrant tachycardia. Sites of slow pathway ablation are often near the coronary sinus ostium, which can be located within a few millimeters of the His bundle. Whether such close proximity of the coronary sinus ostium to the His bundle is unique to patients with AV nodal reentrant tachycardia is unknown. METHODS AND RESULTS: Fifty consecutive patients (mean age 39 +/- 14 years) with no structural heart disease underwent electrophysiologic testing and radiofrequency ablation. The study group consisted of 28 patients with inducible AV nodal reentrant tachycardia or dual AV nodal physiology and 22 patients in the control group. A coronary sinus venogram was performed in each patient. The coronary sinus ostium was similar in size in the study group (11.4 +/- 4.5 mm) and in the control group (10.5 +/- 3.6 mm, P = 0.2). The coronary sinus ostium was funnel shaped in half of the study patients and in half of the control patients (P = 1.0). The mean distance from the upper lip of the coronary sinus ostium to the tip of the His bundle catheter was 9.7 +/- 5.5 mm in the study group and 10.4 +/- 5.1 mm in the control group (P = 0.7). The mean distance from the lower lip of the coronary sinus ostium to the tip of the His-bundle catheter in the study group was 20.1 +/- 6.1 mm and 19.5 +/- 5.6 mm in the control group (P = 0.7). CONCLUSION: This study demonstrates a wide range of normal coronary sinus ostium diameters, morphology, and anatomic relationships with surrounding structures, with no demonstrable correlation to the presence or absence of dual AV node physiology or AV nodal reentrant tachycardia.

Effect of first-phase polarity of biphasic shocks on defibrillation threshold with a single transvenous lead system.

OBJECTIVES: The purpose of this study was to determine whether the polarity of the first phase of a biphasic shock affects the defibrillation threshold. BACKGROUND: The polarity of a monophasic shock has been shown to affect the defibrillation threshold. METHODS: A transvenous defibrillation lead with distal and proximal shocking electrodes was used in this study. In 15 consecutive patients, the defibrillation threshold was determined twice using a step-down protocol, in random order: with the distal coil as the anode for the initial phase (anodal biphasic shock) and with the polarity reversed (cathodal biphasic shock). The power to detect a 5.0-J difference in this study is 0.96. These patients were 61 +/- 11 years old (mean +/- SD), and the mean left ventricular ejection fraction was 0.32 +/- 0.10. RESULTS: Mean defibrillation threshold using anodal biphasic shocks was 9.9 +/- 4.8 J, compared with 9.5 +/- 4.2 J using cathodal biphasic shocks (p = 0.8). In three patients the defibrillation threshold was lower by a mean of 6.3 +/- 2.9 J with the former configuration; in three patients the defibrillation threshold was lower by a mean of 6.7 +/- 2.5 J with the latter configuration; and in nine patients it was the same. Using the standard cathodal configuration, a defibrillation threshold < or = 10 J was obtained in approximately 70% of patients, and a subcutaneous patch was not required in any patient. CONCLUSIONS: The polarity of the first phase of a biphasic shock used with a single transvenous lead does not affect the defibrillation threshold.

Comparison of implantation of nonthoracotomy defibrillators in the operating room versus the electrophysiology laboratory.

Implantable cardioverter-defibrillators (ICDs) with nonthoracotomy lead systems are widely available, and are implanted either in the electrophysiology laboratory or the operating room. The purpose of this study was to prospectively evaluate the safety and efficacy of nonthoracotomy ICD implantation in an electrophysiology laboratory versus an operating room. During a 7-month period, 62 consecutive ICDs with nonthoracotomy lead systems were implanted in patients in an electrophysiology laboratory. During the next 10 months, 110 consecutive ICDs were implanted in patients in a surgical operating room. All ICD implantations were performed under general anesthesia by electrophysiologists. There were no differences in age (58 +/- 14 vs 62 +/- 12 years, p = 0.06), gender distribution (p = 0.3), frequency of structural heart disease (97% vs 97%, p = 0.9), ejection fraction (0.31 +/- 0.15 vs 0.29 +/- 0.13, p = 0.3), or presentation with cardiac arrest (65% vs 53%, p = 0.2) between patients undergoing ICD implantation in the electrophysiology laboratory and operating room, respectively. The rate of successful implantation and of complications for systems implanted in the electrophysiology laboratory (95% and 13%, respectively) and in the operating room (98% and 14%, respectively) were similar (p = 0.4 and p = 0.8, respectively). Specifically, the rate of infection (0% vs 4%, p = 0.3) and hematoma formation (2% vs 4%, p = 0.8) were not statistically significantly different. Three patients who had undergone ICD implantation in an operating room died within 30 days. ICDs with nonthoracotomy lead systems can be implanted with a similarly high rate of success and acceptable complication rate in the electrophysiology laboratory and in the operating room.

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

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

Results and efficiency of programmed ventricular stimulation with four extrastimuli compared with one, two, and three extrastimuli.

BACKGROUND: Conventional programmed ventricular stimulation protocols are inefficient compared with more recently proposed protocols. The purpose of the present study was to determine if additional efficiency could be derived from a 6-step programmed ventricular stimulation protocol that exclusively uses four extrastimuli. METHODS AND RESULTS: The subjects were 209 consecutive patients with coronary artery disease and documented sustained monomorphic ventricular tachycardia, nonsustained ventricular tachycardia, aborted sudden death, or syncope. These patients underwent 159 electrophysiological tests in the absence of antiarrhythmic drug therapy and 105 electrophysiological tests in the presence of antiarrhythmic therapy. Programmed stimulation was performed with two protocols in random order in each patient. Both protocols used an eight-beat drive train, 4-s intertrain pause, and basic drive cycle lengths of 350, 400, and 600 ms. The 6-step protocol started with coupling intervals of 290, 280, 270, and 260 ms, which were shortened simultaneously in 10-ms steps until S2 was refractory. The 18-step protocol used one, two and three extrastimuli in conventional sequential fashion. The end points were 30 s of sustained monomorphic ventricular tachycardia, two episodes of polymorphic ventricular tachycardia requiring cardioversion, or completion of the protocol at two right ventricular sites. There was no significant difference in the yield of sustained monomorphic ventricular tachycardia using the two protocols, regardless of the clinical presentation or treatment with antiarrhythmic drugs. Polymorphic ventricular tachycardia occurred with the 18-step protocol twice as frequently as with the 6-step protocol (6% versus 3%, P < .001). The duration of the 18-step protocol was significantly longer than that of the 6-step protocol in patients with inducible ventricular tachycardia (5.5 +/- 7 versus 2.3 +/- 2 minutes, P < .001), as well as in patients without inducible ventricular tachycardia (25.4 +/- 7 versus 6.9 +/- 2 minutes, P < .001). CONCLUSION: A stimulation protocol that exclusively uses four extrastimuli improves the specificity and efficiency of programmed ventricular stimulation without compromising the yield of monomorphic ventricular tachycardia in patients with coronary artery disease.

Electrophysiologic effects of sotalol and amiodarone in patients with sustained monomorphic ventricular tachycardia.

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.

The economic impact of transvenous defibrillation lead systems.

The purpose of this study was to compare implant charges and convalescence for transvenous and epicardial defibrillation systems. Hospital stay, intensive care utilization, professional fees, and hospital bills were compared in 44 patients who underwent implantation of a cardiac defibrillator between September 1991 and May 1993. Twenty-five consecutive patients received an epicardial lead system, while 19 consecutive patients underwent implantation of the entire transvenous defibrillation system in the electrophysiology laboratory. There were no significant differences between the two groups in mean age or left ventricular ejection fraction. There was a significant reduction in postoperative hospital convalescence from 7.2 +/- 2.0 days with epicardial systems to 3.1 +/- 1.5 days with transvenous systems (P < 0.001). Postoperative intensive care unit stay was significantly reduced with transvenous systems compared with epicardial systems (0.1 +/- 0.2 vs 1.5 +/- 0.9 days; P < 0.001). Hospital charges were also significantly reduced with the transvenous lead system implants. Mean implant charges were lower with transvenous systems: $32,090 +/- $2,620 vs $38,307 +/- $2,701 (P < 0.001); convalescence charges were lower: $5,861 +/- $5,010 $12,447 +/- $4,969 (P < 0.001); the total hospital bill was also significantly lower with transvenous systems: $53,459 +/- $12,588 vs $71,981 +/- $16,172 (P < 0.001). Professional fees for implantation ($4,131 +/- $1,724 vs $6,100 +/- 0, P < 0.001), convalescence care ($1,258 +/- $960 vs $2,846 +/- $1,770; P < 0.001), and total professional fees ($12,925 +/- $4,772 vs $15,731 +/- $4,055, P < 0.05) were lower in the transvenous defibrillation group.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of shock polarity on ventricular defibrillation threshold using a transvenous lead system.

OBJECTIVES: The purpose of this study was to determine whether the polarity of a monophasic shock used with a transvenous lead system affects the defibrillation threshold. BACKGROUND: The ability to implant an automatic defibrillator depends on achieving an adequate defibrillation threshold. METHODS: A transvenous defibrillation lead with distal and proximal shocking electrodes was used in this study. In 29 consecutive patients, the defibrillation threshold, using a stepdown protocol was determined twice in random order: 1) with the distal coil as the anode, and 2) with the polarity reversed. Only the 20 patients in whom an adequate defibrillation threshold could be obtained with the transvenous lead alone were included in this study. These patients were 61 +/- 14 years old (mean +/- SD) and had a mean ejection fraction of 28 +/- 12%. RESULTS: The mean defibrillation threshold was 11.5 +/- 5.0 J with the distal coil as the anode versus 16.9 +/- 7.7 J with the distal coil as the cathode (p = 0.04). The defibrillation threshold was lower by a mean of 9 +/- 7 J with the former configuration in 14 patients and was lower by a mean of 7 +/- 6 J with the latter configuration in 3 patients; in 3 patients it was the same with both configurations. Use of a subcutaneous patch was avoided in five patients by utilizing the distal electrode as the anode. CONCLUSIONS: Defibrillation thresholds with monophasic shocks are approximately 30% lower with the distal electrode as the anode. The use of anodal shocks may obviate the need for a subcutaneous patch and allow more frequent implantation of a transvenous lead system.

Implantation by electrophysiologists of 100 consecutive cardioverter defibrillators with nonthoracotomy lead systems.

BACKGROUND: Traditional lead systems for implantable cardioverter defibrillators (ICDs) require a thoracotomy for placement. Nonthoracotomy lead systems are available and are usually implanted by an electrophysiologist and a surgeon. The purpose of this study was to prospectively evaluate the safety and efficacy of ICD implantation with a nonthoracotomy lead system by electrophysiologists. METHODS AND RESULTS: A consecutive series of 100 patients (mean age, 61 +/- 13 years, +/- SD) underwent ICD implantation with a nonthoracotomy lead system while intubated and under general anesthesia. Seventy-seven patients had coronary artery disease, 15 had idiopathic cardiomyopathy, 6 had miscellaneous heart disease, and 2 had structurally normal hearts. The mean ejection fraction was 0.29 +/- 0.13. Sixty-eight patients had suffered a cardiac arrest, and 32 had had ventricular tachycardia or syncope. All patients except 9 underwent electrophysiological testing and had failed 1 +/- 1 drug trials before ICD implantation. Three types of nonthoracotomy lead systems were used. The nonthoracotomy lead with an ICD was successfully implanted in 96 patients (96%). Of the unsuccessful implants, 1 patient did not have venous access, the passive fixation lead in 1 would not remain lodged, 1 had elevated defibrillation thresholds, and 1 developed a hemopneumothorax while venous access was being obtained. The mean defibrillation threshold was 17 +/- 6 J. The mean procedure duration was 161 +/- 57 minutes. When a subcutaneous patch was used (n = 58), the procedure duration was 189 +/- 5 minutes, and when a subcutaneous patch was not required (n = 40), the procedure lasted 123 +/- 37 minutes (P < .0001). Patients remained in the hospital 4.5 +/- 4.1 days after implantation, with no procedure-related deaths. Acute complications occurred in 10 patients; 2 had lead dislodgments, 1 with previous abdominal surgery had his abdominal cavity entered (without other complications) while the ICD pocket was being made, 1 had postoperative heart failure, 1 developed a large hematoma when anticoagulation therapy was initiated, 3 required reintubation because of excessive anesthesia, 1 developed superficial cellulitis, and 1 developed a hemopneumothorax secondary to a lacerated subclavian vein. During 6 +/- 3 months of follow-up, 2 patients developed lead fractures. CONCLUSIONS: (1) Electrophysiologists can implant an ICD with a nonthoracotomy lead system safely and with a high success rate; (2) use of a subcutaneous patch correlates with longer procedure durations; and (3) special precautions should be taken in patients with previous abdominal surgery.

Effects of partial and complete ablation of the slow pathway on fast pathway properties in patients with atrioventricular nodal reentrant tachycardia.

INTRODUCTION: The purpose of this study was to prospectively compare the effects of complete and partial ablation of slow pathway function on the fast pathway effective refractory period (ERP). METHODS AND RESULTS: The subjects were 20 patients (mean age 43 +/- 13 years) with atrioventricular nodal reentrant tachycardia (AVNRT), no structural heart disease, and easily inducible AVNRT. Autonomic blockade was achieved with propranolol (0.2 mg/kg) and atropine (0.04 mg/kg). After elimination of AVNRT and during autonomic blockade, the presence of residual slow pathway function was determined by the presence of a single AV nodal echo and/or dual AV nodal physiology. After autonomic blockade and before ablation, the mean fast pathway ERP was 319 +/- 44 msec and the mean slow pathway ERP was 251 +/- 31 msec. After slow pathway ablation and during autonomic blockade, 7 patients had residual slow pathway function and 13 did not. Complete loss of slow pathway function was associated with a shortening of the fast pathway ERP from 334 +/- 35 msec to 300 +/- 62 msec (P < 0.01), while the fast pathway ERP did not change significantly in patients with residual slow pathway function (291 +/- 29 msec vs 303 +/- 38 msec, respectively; P = 0.08). A shortening of 30 msec or more in the fast pathway ERP was observed in 11 of 13 patients who did not have residual slow pathway function, compared to 0 of 7 patients with residual slow pathway function (P < 0.001). CONCLUSION: Shortening of the fast pathway ERP after successful ablation of AVNRT is dependent upon complete loss of slow pathway function. This observation is consistent with electrotonic inhibition of the fast pathway by the slow pathway.

Transvenous and subcutaneous implantable cardioverter defibrillators: radiographic assessment.

PURPOSE: To assess chest radiograph configurations in 102 patients following total or partial transvenous and subcutaneous insertion of a non-thoracotomy lead implantable cardioverter defibrillator (NTL-ICD) device. MATERIALS AND METHODS: The four overlapping system types reviewed were the Endotak (49 patients), PCD (32 patients), Res-Q (10 patients), and hybrid combinations of NTL-ICD and surgically inserted pericardial and epicardial automatic implantable cardioverter defibrillator (AICD) devices (15 patients). RESULTS: Abnormalities were detected on radiographs both at the time of implantation and at early follow-up. NTL-ICD electrodes partially replaced or augmented AICD systems in 11 patients (10.7%) because of sensing lead or defibrillation failure or infection. Defibrillation failure necessitated augmentation of NTL-ICD systems with AICD pericardial patches in four patients (3.9%). Catheter displacement, lead fracture, or pneumothorax was detected in eight patients (7.8%). CONCLUSION: Complex radiographic appearances may be seen and important abnormalities may be detected after insertion of these devices.

Randomized comparison of anatomic and electrogram mapping approaches to ablation of the slow pathway of atrioventricular node reentrant tachycardia.

OBJECTIVES: The purpose of this study was to prospectively compare in random fashion an anatomic and an electrogram mapping approach for ablation of the slow pathway of atrioventricular (AV) node reentrant tachycardia. BACKGROUND: Ablation of the slow pathway in patients with AV node reentrant tachycardia can be performed by using either an anatomic or an electrogram mapping approach to identify target sites for ablation. These two approaches have never been compared prospectively. METHODS: Fifty consecutive patients with typical AV node reentrant tachycardia were randomly assigned to undergo either an anatomic or an electrogram mapping approach for ablation of the slow AV node pathway. In 25 patients randomly assigned to the anatomic approach, sequential radiofrequency energy applications were delivered along the tricuspid annulus from the level of the coronary sinus ostium to the His bundle position. In 25 patients assigned to the electrogram mapping approach, target sites along the posteromedial tricuspid annulus near the coronary sinus ostium were sought where there was a multicomponent atrial electrogram or evidence of a possible slow pathway potential. If the initial approach was ineffective after 12 radiofrequency energy applications, the alternative approach was then used. RESULTS: The anatomic approach was effective in 21 (84%) of 25 patients, and the electrogram mapping approach was effective in all 25 patients (100%) randomly assigned to this technique (p = 0.1). The four patients with an ineffective anatomic approach had a successful outcome with the electrogram mapping approach. On the basis of intention to treat analysis, there were no significant differences between the electrogram mapping approach and the anatomic approach with respect to the time required for ablation (28 +/- 21 and 31 +/- 31 min, respectively, mean +/- SD, p = 0.7) duration of fluoroscopic exposure (27 +/- 20 and 27 +/- 18 min, respectively, p = 0.9) or mean number of radiofrequency applications delivered (6.3 +/- 3.9 vs. 7.2 +/- 8.0, p = 0.6). With both the anatomic and electrogram mapping approaches, the atrial electrogram duration and number of peaks in the atrial electrogram were significantly greater at successful target sites than at unsuccessful target sites. CONCLUSIONS: The anatomic and electrogram mapping approaches for ablation of the slow AV nodal pathway are comparable in efficacy and duration. If the anatomic approach is initially attempted and fails, the electrogram mapping approach may be successful at sites outside the areas targeted in the anatomic approach. With both the anatomic and electrogram mapping approaches, there are significant differences in the atrial electrogram configuration between successful and unsuccessful target sites.