bluuebunny/crossref_metadata_2025 huggingface dataset:
Origin of planktotrophy—evidence from early molluscs
Authors: Nützel Alexander , Lehnert Oliver , Frýda Jir̆í
Published: June 2006

SUMMARY
The size of early ontogenetic shells (protoconchs) of ancient benthic molluscs suggests that feeding larvae occurred at about 490 myr (approximately, transition from Cambrian to Ordovician). Most studied Ordovician protoconchs were smaller than Cambrian ones, indicating smaller Ordovician eggs and hatchlings. This suggests substitution of nutritious reserve matter such as yolk by plankton as an energy source for larvae. The observed size change represents the first direct empiric evidence for a late Cambrian to Ordovician switch to planktotrophy in invertebrate larvae. It corroborates previous hypotheses about a possible polyphyly of planktotrophy. These hypotheses were primarily based on molecular clock data of extant clades with different types of larva, change in the overall body size, as well as increasing predation pressure on Early Paleozoic sea floors. The Early Ordovician is characterized by an explosive radiation of benthic suspension feeders and it was suggested that planktotrophy would prolongate escape from benthic predation on hatchlings. This biological escalation hypothesis does not fully explain why planktotrophy and suspension feeding became important at the same time, during a major biodiversification. An additional factor that probably included availability of nutrients must have played a role. We speculate that an increasing nutrient supply and availability of photoautotrophic plankton in world oceans have facilitated both planktotrophy and suspension feeding, which does not exclude a contemporaneous predation‐driven escalation. It is very likely that the evolution of planktotrophy as well as increasing predation contributed to the Ordovician radiation.
Different roads to form the same gut in nematodes
Authors: Houthoofd Wouter , Willems Maxime , Vangestel Sandra , Mertens Clarinda , Bert Wim , Borgonie Gaëtan
Published: June 2006

SUMMARY
The morphogenesis of a gut from the endoderm has been well studied among the animal kingdom and is also well described in the nematode Caenorhabditis elegans. But are there other ways to build a nematode intestine? Sulston et al. (1983) described a different intestinal cell lineage in the species Panagrellus redivivus and Turbatrix aceti that includes two programmed cell deaths. However, no details are known about the three‐dimensional (3D) configuration and the role of the cell deaths. Here, we describe the intestinal morphogenesis of P. redivivus and five other nematode species by means of four‐dimensional microscopy, which gives us a 3D representation of gut formation at the cellular level. The morphological pathway of gut formation is highly conserved among these distantly related species. However, we found the P. redivivus pattern in another related species Halicephalobus gingivalis. In this pattern, the intestinal precursors migrate inward in concert with the mesoderm precursors. Based on the observations, we propose a hypothesis that could explain the differences. The positions of the mesoderm precursors create a possible spatial constraint, by which the establishment of bilateral symmetry in the intestine is delayed. This symmetry is corrected by cell migrations; other cells are eliminated and compensated by supplementary cell divisions. This pattern leads to the same result as in the other nematodes: a bilateral symmetrical intestine with nine rings. This illustrates how conserved body plans can be achieved by different developmental mechanisms.
A model for the morphogenesis of strip reduction patterns in phototrophic euglenids: evidence for heterochrony in pellicle evolution
Authors: Esson H. J. , Leander B. S.
Published: June 2006

SUMMARY
We propose a general developmental model that explains the evolutionary origin, diversification, and inheritance of pellicle strip patterns in phototrophic euglenids. Dividing cells of Euglena gracilis, E. viridis, and Phacus similis were observed with scanning electron microscopy in order to study the morphogenesis of posterior whorls of strip reduction. We found evidence that constant whorl numbers are maintained through cell division because of organized strip growth before and during cytokinesis. Alternating nascent strips form a new whorl of strip reduction at each of the anterior and posterior ends of daughter cells. Strips that terminated to form posterior whorls in the mother cell change in length during the development of daughter cells. In the mother cells of E. gracilis, the strips forming whorls I and II grow to become whorls II and III, respectively, in the daughter cells; the strips forming whorl III in the mother cell lengthen and meet with other strips already present at the posterior tip of daughter cells. This process of whorl morphogenesis during asexual reproduction is consistent with known variation in pellicle strip patterns and suggests that heterochrony played a major role in the ultrastructural evolution of phototrophic euglenids.
Unexpected Loss of Bipolar Pacing With Implanted Dual Chamber Pacemakers
Authors: GUO G. BIH‐FANG , CHEN MIEN‐CHENG , WANG CHUN‐CHIEH , CHANG KUNG‐CHENG , FU MORGAN
Published: June 2006

Bipolar leads are most commonly used in the current practice of pacemaker therapy. In our study of 124 patients implanted with Guidant/Cardiac Pacemakers (CPI) Vigor dual chamber pacemakers, 5 patients had unexpectedly abrupt increases in bipolar lead impedance and pacing threshold 2 weeks to 18 months postimplantation without changes in sensing function. With the lead configuration reprogrammed to unipolar, the lead impedance and pacing threshold were restored to appropriate ranges. The changes in bipolar lead parameters can be caused by the CPI's “Quick Connect” (QC1) header lead system incorporated in these pacemakers.
Tissue Temperatures and Lesion Size During Irrigated Tip Catheter Radiofrequency Ablation: An In Vitro Comparison of Temperature‐Controlled Irrigated Tip Ablation, Power‐Controlled Irrigated Tip Ablation, and Standard Temperature‐Controlled Ablation
Authors: PETERSEN HELEN HØGH , CHEN XU , PIETERSEN ADRIAN , SVENDSEN JESPER HASTRUP , HAUNSØ STIG
Published: June 2006

The limited success rate of radiofrequency catheter ablation in patients with ventricular tachycardias related to structural heart disease may be increased by enlarging the lesion size. Irrigated tip catheter ablation is a new method for enlarging the size of the lesion. It was introduced in the power‐controlled mode with high power and high infusion rate, and is associated with an increased risk of crater formation, which is related to high tissue temperatures. The present study explored the tissue temperatures during temperature‐controlled irrigated tip ablation, comparing it with standard temperature‐controlled ablation and power‐controlled irrigated tip ablation. In vitro strips of porcine left ventricular myocardium were ablated. Temperature‐controlled irrigated tip ablation at target temperatures 60°C, 70°C, and 80°C with infusion of 1 mL saline/min were compared with standard temperature‐controlled ablation at 70°C and power‐controlled irrigated tip ablation at 40 W, and infusion of 20 mL/min. Lesion size and tissue temperatures were significantly higher during all modes of irrigated tip ablation compared with standard temperature‐controlled ablation (P < 0.05). Lesion volume correlated positively with tissue temperature (r = 0.87). The maximum recorded tissue temperature was always 1 mm from the ablation electrode and was 67 ± 4°C for standard ablation and 93 ± 6°C, 99 ± 6°C, and 115 ± 13°C for temperature‐controlled irrigated tip ablation at 60°C, 70°C, and 80°C, respectively, and 112 ± 12°C for power‐controlled irrigated tip ablation, which for irrigated tip ablation was significantly higher than tip temperature (P < 0.0001). Crater formation only occurred at tissue temperatures > 100°C. We conclude that irrigated tip catheter ablation increases lesion size and tissue temperatures compared with standard ablation in the temperature‐controlled mode at the same or higher target temperatures and in the power‐controlled mode. Furthermore, tissue temperature and delivered power are the best indicators of lesion volume during temperature‐controlled ablation.
Electrophysiological Correlates of Transmural Linear Ablation
Authors: LIEM L. BING , POMERANZ MARK , RISELING KIM , ANDERSON STEVE , BERRY GERALD J.
Published: June 2006

The purpose of this study is to describe the characteristics of lesions created using radiofrequency (RF) energy delivered through a saline/foam electrode that is designed to simplify ablation of the isthmus between the tricus‐pid annulus (TA) and the inferior vena cava (IVC). We compared the changes in the electrophysiological parameters produced by the ablation to histological findings. In search of a more practical and effective atrial flutter ablation method, various energy modifications and catheter designs have been tested. It was shown that the efficiency of RF ablation could be improved using an endocardial cooled catheter; resulting in increased lesion size. Thus, we postulate that a similar advantage of the cooled catheter system would allow efficient RF delivery through specially designed long foam electrodes, therefore improving the practicality of TA‐IVC isthmus ablation for a trial flutter. The study was performed in two acute and five subacute sheep under general anesthesia and with adequate heparinization. We used a linear ablation catheter system equipped with two 2‐cm saline bipole electrode pockets with 1.5‐mm separation, each consisting of two 8‐mm electrodes with 1‐mm spacing, allowing for bipolar pacing and recording. This saline/foam electrode pair were positioned on a support loop. RF energy was applied to the saline electrodes at 50 watts for 90 seconds with a saline flow rate of 0.4 mL/s. Bipolar atrial signal amplitude and pacing thresholds were measured before and after ablation. If necessary, the catheter was pulled back and additional ablation was applied to any viable tissue. Transisthmus ablations were created with a single catheter positioning in five sheep using both saline electrodes in four and one electrode in the other. Fullback and additional ablation to one saline electrode was required in two sheep; in one after RF was delivered to only one electrode. After ablation, a trial signal amplitude was reduced by an average of 76% (range 51%‐92%) and its pacing threshold was increased by an average of 617% (range 150%–400%). Transmural lesions were found in all sheep, measuring 8–20 mm in length, 4–10 mm in width, and 1.5–2.0 mm in depth. No charring, coagulum, or remote structural damage was found in any preparation. Continuous transmural TA‐IVC isthmus lesions could be produced with stationary RF linear ablation using a saline/foam electrode catheter system. This system allowed for assessment of electrophysiological parameters that correlated with complete necrosis.
Long‐Term Reproducibility of Ventricular Tachycardia Induction with Electrophysiological Testing in Patients with Coronary Heart Disease and Depressed Left Ventricular Ejection Fraction
Authors: BREMBILLA‐PERROT B. , HOURIEZ P. , CLAUDON O. , PREISS J.P. , BEURRIER D. , LOUIS P. , DE LACHAISE A. TERRIER
Published: June 2006

The Multicenter Automatic Defibrillator Implantation Trial (MADIT) has recently confirmed the role of programmed ventricular stimulation (PVS) to identify the high risk patients of sudden death after myocardial infarction and to prevent this risk. The purpose of this study was to evaluate the long‐term reproducibility of PVS in these patients. Thirty patients with coronary heart disease without spontaneous documented sustained ventricular tachycardia (VT) underwent two programmed stimulations in the absence of antiarrhythmic drug treatment between 2 and 6 years (mean 4 years). No patient had a myocardial infarction or intervening cardiac surgery during this period. The protocol of study was similar using up to three extrastimuli in two sites of the right ventricle, delivered in sinus rhythm and driven rhythm (600 ms, 400 ms, respectively). On the first PVS, 17 patients had inducible sustained VT (group I). Thirteen patients did not have inducible VT (group II). On the second PVS all group I patients but one had inducible VT, but the cycle length was significantly modified in 11. In group II, five patients had inducible VT and in the other patients the PVS remained negative. In conclusion, in patients with coronary heart disease, but without documented VT, the long‐term reproducibility of PVS was excellent in those with inducible VT (94%); the patients remain at risk of VT and a prophylactic implantable car‐dioverter defibrillator could be considered. In patients with initially negative study, reproducibility of PVS was lower (61.5 %), probably because of the progressive remodeling after myocardial infarction. Therefore, the occurrence of new symptoms in patients with previously negative study requires a second programmed ventricular stimulation.
Preserving Normal Ventricular Activation Versus Atrioventricular Delay Optimization During Pacing: The Role of Intrinsic Atrioventricular Conduction and Pacing Rate
Authors: ILIEV IVAN ILIEV , YAMACHIKA SHIRO , MUTA KEIZO , HAYANO MOTONOBU , SHIISHIMATSU TAKA , NAKAO KOJIRO , KOMIYA NORIHIRO , HIRATA TETSUYA , UEYAMA CHIAKI , YANO KATSUSUKE
Published: June 2006

The purpose of the study was to compare the effects of DDD pacing with optimal AV delay and AAI pacing on the systolic and diastolic performance at rest in patients with prolonged intrinsic AV conduction (first‐degree AV block). We studied 17 patients (8 men, aged 69 ± 9 years) with dual chamber pacemakers implanted for sick sinus syndrome in 15 patients and paroxysmal high degree AV block in 2 patients. Aortic flow and mitral flow were evaluated using Doppler echocardiography. Study protocol included the determination of the optimal A V delay in the DDD mode and comparison between AAI and DDD with optimal A V delay for pacing rate 70/min and 90/min. Stimulus‐R interval during AAI (AHI) was 282 ± 68 ms for rate 70/min and 330 ± 98 ms for rate 90/min (P < 0.01). The optimal A V delay was 159 ± 22 ms, A V delay optimization resulted in an increase of an aortic flow time velocity integral (AFTVI) of 16%± 9%. At rate 70/min the patients with ARI ≤ 270 ms had higher AFTVI in AAI than in DDD (0.214 ± 0.05 m vs 0.196 ± 0.05 m, P < 0.01), while the patients with ARI > 270 ms demonstrated greater AFTVI under DDD compared to AAI(0.192 ± 0.03 m vs 0.166 ± 0.02 m, P < 0.01). At rate 90/min AFTVI was higher during DDD than AAI (0.183 ± 0.03 m vs 0.162 ± 0.03 m, P < 0.01). Mitral flow time velocity integral (MFTVI) at rate 70/min was higher in DDD than in AAI (0.189 ± 0.05 m vs 0.173 ± 0.05 mP < 0.01), while at rate 90/min the difference was not significant in favor of DDD (0.149 ± 0.05 m vs 0.158 ± 0.04 m). The results suggest that in patients with first‐degree AV block the relative impact of DDD and AAI pacing modes on the systolic performance depends on the intrinsic AV conduction time and on pacing rate.
Electrophysiologist‐Implanted Transvenous Cardioverter Defibrillators Using Local Versus General Anesthesia
Authors: MANOLIS ANTONIS S. , MAOUNIS THEMOS , VASSILIKOS VASSILIS , CHILADAKIS JOHN , COKKINOS DENNIS V.
Published: June 2006

With the advent of smaller biphasic transvenous implantable Cardioverter defibrillators (ICDs) and the experience gained over the years, it is now feasible for electrophysioiogists to implant them safely in the abdominal or pectoral area without surgical assistance. Throughout the years, general anesthesia has been used as the standard technique of anesthesia for these procedures. However, use of local anesthesia combined with deep sedation only for defibrillation threshold (DFT) testing might further facilitate and simplify these procedures. The purpose of this study was to test the feasibility of using local anesthesia and compare it with the standard technique of general anesthesia, during implantation of transvenous ICDs performed by an electrophysiologist in the electrophysiology laboratory. For over 4 years in the electrophysiology laboratory, we have implanted transvenous ICDs in 90 consecutive patients (84 men and 6 women, aged 58 ± 15 years). Early on, general anesthesia was used (n = 40, group I), but in recent series (n = 50, group II) local anesthesia was combined with deep sedation for DFT testing. Patients had coronary (n = 58) or valvular (n = 4) disease, cardiomyopathy (n = 25) or no organic disease (n = 3), a mean left ventricular ejection fraction of 35%, and presented with ventricular tachycardia (n = 72) or fibrillation (n = 16), or syncope (n = 2). One‐lead ICD systems were used in 74 patients, two‐lead systems in 10 patients, andan AVICD in 6 patients. ICDs were implanted in abdominal (n = 17, all in group I) or more recently in pectoral (n = 73) pockets. The DFT averaged 9.7 ± 3.6 J and 10.2 ± 3.6 J in the two groups, respectively (P = NS) and there were no differences in pace‐sense thresholds. The total procedural duration was shorter (2.1 ± 0.5 hours) in group II (all pectoral implants) compared with 23 pectoral implants of group I (2.9 ± 0.5 hours) (P < 0.0001). Biphasic devices were used in all patients and active shell devices in 67 patients; no patient needed a subcutaneous patch. There were six complications (7%), four in group I and two in group II: one pulmonary edema and one respiratory insufficiency that delayed extubation for 3 hours in a patient with prior lung resection, both probably related to general anesthesia, one lead insulation break that required reoperation on day 3, two pocket hematomas, and one pneumothorax. There was one postoperative arrhythmic death at 48 hours in group I. No infections occurred. Patients were discharged at a mean time of 3 days. All devices functioned well at predischarge testing. Thus, it is feasible to use local anesthesia for current ICD implants to expedite the procedure and avoid general anesthesia related cost and possible complications.
Short‐, Mid‐, and Long‐Term Reproducibility of the Atrial Signal‐Averaged Electrocardiogram in Healthy Subjects: Comparison with the Conventional Ventricular Signal‐Averaged Electrocardiogram
Authors: SAVELIEVA IRINA , AYTEMIR KUDRET , HNATKOVA KATERINA , CAMM A. JOHN , MALIK MAREK
Published: June 2006

Although atrial signal‐averaged electrocardiogram (SAECG) has been proposed for noninvasive identification of patients with atrial tachyarrhythmias, the substantial variability of the measurement limits the clinical value. The aim of the study was to assess the short‐ to long‐term reproducibility of atrial SAECG and to compare it to that of the conventional ventricular SAECG in 51 healthy volunteers (30 men; age 32 ± 8 years). In each subject, SAECG recordings were obtained using MAC‐VU electrocardiograph and HiRES and PHiRES software (Marquette Medical Systems) and repeated after 5 minutes, 1 day, 1 week, and 1 month. Automatically detected onset and offset of the filtered QRS complex and P wave were subsequently corrected by two independent observers, and the averaged values were used for the analysis. Conventional ventricular SAECG parameters: filtered QRS duration (QRStot), low amplitude signal duration, and root mean square voltage (RMS) of the terminal 40 ms of QRS; and 5 atrial parameters: filtered P wave duration (Ptot), RMS of the terminal 40, 30, 20 ms, and of the entire P wave were obtained. Relative errors of different pairs of measures were used to assess the intrasubject reproducibil‐ity. QRStot and Ptot were the most reproducible parameters. The relative errors after 5 minutes, 1 day, 1 week, and 1 month were 0.8% to 2.4% for QRStot, and 1.3% to 4.2% for Ptot. For RMS voltages, the relative errors exceeded 15% in short‐term and 20% in long‐term recordings. Although Ptot was statistically less reproducible than QRStot, the reproducibility of the former was good and comparable to that of the QRStot. The reproducibility of the voltage parameters was significantly poorer than that of the duration parameters. The study showed a satisfactory short‐ and long‐term reproducibility of Ptot in the atrial SAECG in healthy subjects. However, low reproducibility of the voltage parameters should be considered in clinical applications.
Cisapride and Torsades de Pointes in a Pacemaker Patient
Authors: NG KHENG‐SIANG , THAM LAI‐SAN , TAN HWEE‐HUAN , CHIA BOON‐LOCK
Published: June 2006

Cisapride induced QTprolongation with consequent life‐threatening arrhythmias including torsades de pointes has recently been documented but is rare. We report the case of a patient who had received permanent pacemaker therapy for complete AV block with symptomatic bradycardia dependent torsades de pointes, but suffered breakthrough torsades during cisapride therapy despite constant pacing.
Adenosine Induced Atrial Fibrillation Precipitating Polymorphic Ventricular Tachycardia
Authors: KAPLAN ILYA V. , KAPLAN ALEXANDER V. , FISHER JOHN D.
Published: June 2006

An 86‐year‐old female developed supraventricular tachycardia 36 hours after a myocardial infarction (MI). She developed atrial fibrillation and polymorphic ventricular tachycardia (PVT) following administration of 12 mg ofadenosine. The PVT caused hemodynamic instability with no response to cardioversion, but termination with procainamide. The heart is vulnerable to hemodynamically unstable, possibly lethal, PVT early after MI under some circumstances. This vulnerability may be exposed following administration of adenosine. Extra caution is warranted when using adenosine in the post‐Mi period.
Dual Chamber Pacemaker Implantation Via a Double Superior Vena Cava
Authors: GARG A. , SADLER M.R.DE C , ROZKOVEC A.
Published: June 2006

We present the chest X ray of a woman with sinoatrial node disease. She has had a dual chamber pacemaker implanted with each lead coursing through a separate superior vena cava.
Electrocardiographic Criteria for Diagnosis of Irregular Broad Complex Tachycardia with a High Sensitivity for Preexcited Atrial Fibrillation
Authors: LAU ERNEST W. , PATHAMANATHAN RAVI K. , NG G. ANDRÉ , GRIFFITH MICHAEL J.
Published: June 2006

AF may appear as an irregular broad complex tachycardia (BCT) if atrioventricular conduction occurs via an accessory pathway (preexcited AF) or if bundle branch block (BBB), preexistent or rate related, exists in the His‐Purkinje system (BBB‐AF). While BBB‐AF is relatively benign, preexcited AF may herald sudden cardiac death. Hence it is important that the two conditions can be reliably distinguished. Yet. there is no preexistent algorithms for this purpose. Griffith et al. previously proposed a simple algorithm for a similar problem, that of distinguishing the two differential diagnoses for regular BCT: VT and SVT with BBB, on the basis that unless the QRS morphologies in V1 and V6 are absolutely typical of BBB, VT will be diagnosed. The authors propose an extrapolation of this principle to irregular BCT by stating that, unless the QBS morphologies in V1 and V6 are absolutely typical of BBB, preexcited AF will he diagnosed. Seventy‐five ECGs showing irregular BCT (41 preexcited AF and 34 BBB‐AF) were shown to two fellows in electrophysiology who were given no other information and were instructed to diagnose preexcited AF unless the QRS morphology pattern was typical of BBB. Observer 1 achieved a sensitivity of 100% (41/41) and a specificity of 79% (27/34). while observer 2 achieved a sensitivity of 100% and a specificity of 85% (29/34), By QRS morphology pattern, an average sensitivity of 100% and specificity of 82% were achieved for the diagnosis of irregular BCT. The algorithm is simple and easy to implement and recommended for clinical use.
Does an Early Increase in Heart Rate During Tilting Predict the Results of Passive Tilt Testing?
Authors: SUMIYOSHI MASATAKA , NAKATA YASURO , MINEDA YORIAKI , TOKANO TAKASHI , YASUDA MASAYUKI , NAKAZATO YUJI , YAMAGUCHI HIROSHI
Published: June 2006

Head‐up tilt testing is a useful but time‐consuming procedure. If we could accurately predict the tilt testing results; we would be able to substantially shorten the duration of tilt protocol. To clarify the hypothesis that an early increase in heart rate (HR) during tilting can predict the passive tilt results in our protocol (80‐degree angle for 30 minutes), we studied 115 consecutive patients (72 men, 43 women, mean age 46 ± 19 years) who were clinically diagnosed with neurally mediated syncope. Twentynine (25%) patients had a positive tilt test (P group), whereas 86 (75%) patients had a negative test (N group). The early HR increase was defined as the maximum HR during the first 5 minutes of tilting minus the resting HR before tilting. The early HR increase was significantly higher in the P group (23.8 ± 9.5 beats/min) than in the N group (17.5 ± 8.2 beats/min, P = 0.0008), but it was negatively correlated with the tilt duration to positive response (r =−0.52, P = 0.0032) and the patient age in the entire study population (r = 0.62, P < 0.0001). Results of multiple regression analysis indicated that age, tilt result, and tilt duration were independently associated with the early HR increase. As a result, an early HR increase ± 18 beats/min, the best apparent cut‐off point obtained in our study, was a sensitive (100%) marker for prediction of a positive response at ± 15 minutes of tilting, but it showed a low specificity (61 %). In conclusion, an early HR increase during 80‐degree tilting may be only predictive for a positive result ± 15 minutes because it depends on the tilt duration to a positive response and patient age.
Safe and Effective Placement of Two Bipolar Silicone Leads in the Cephalic Vein Using a Hydrophilic Guidewire and a Split Introducer
Authors: DA COSTA A. , FAURE E. , ROMEYER C. , SAMUEL B. , MESSIER M. , LAMAUD M. , ISAAZ K.
Published: June 2006

The cephalic vein (CV) is preferable to the subclavian vein for implanting permanent pacing leads because of fewer complications. Unfortunately, this access is unusable in a substantial number of patients. This prospective study evaluates a technique to increase CV access for the placement of two silicons bipolar leads used in DDD pulse generator implants. A standard cephalic cutdown was performed under local anesthesia and a hydrophilic guidewire (HGW) threaded in the CV. The first (ventricular) bipolar lead was then introduced and positioned. When possible, introduction of the second (atrial) lead followed the same direct access. A failed introduction led to a modified procedure (MP) relying on a “split” introducer (8–9 Fr Plastimed) advanced with a circular motion over the HGW, then removal of the dilator, removal of the HGW, insertion of the pacing lead into the sheath with placement in the right atrium, followed by sheath withdrawal. Over an 18‐month period, 90 consecutive patients had DDD pacemakers implanted. The CV was accessible in 76 (84.5%) of 90 patients and the direct introduction of the ventricular lead was obtained in 74 (97.4%) of these. Atrialization proceeded as follows: direct access CV in 14 (18%) of 76 patients, MP access in 54 (71 %) of 76 patients, and MP failure in 8(11 %) of 76 patients. Overall, this approach allowed cephalic dual insertion in 68 (89%) of 76 patients. In conclusion, the modified procedure presented in this study allows a dual catheteriza‐tion with bipolar leads in 89% of patients when a CV is available. This significantly improves the success rate for dual bipolar lead implants in this configuration.
A Comparative Study on the Behavior of Three Different Automatic Mode Switching Dual Chamber Pacemakers to Intracardiac Recordings of Clinical Atrial Fibrillation
Authors: LEUNG SUM‐KIN , LAU CHU‐PAK , LAM CATHY T.F. , TSE HUNG‐FAT , TANG MAN‐OI , CHUNG FELSA , AYERS GREGORY
Published: June 2006

Automatic mode switching (AMS) allows patients with dual chamber pacemakers who develop paroxysmal AF to have a controlled ventricular rate. The aim of this study was to (1) compare the rate‐controlled behavior of three AMS algorithms in response to AF, in terms of speed and stability of response and resynchro‐nization to sinus rhythm, and (2) compare the influence of pacemaker programming on optimal mode switching. We studied 17 patients (12 men, 5 women; mean age 59 ± 15 years) who developed AF during electrophysiological study. Unfiltered bipolar atrial electrograms during sinus rhythm and AF were recorded onto high fidelity tapes and replayed into the atrial port of three dual chamber pacemakers with different mode switching algorithms (Them, Marathon, Meta). The Thera pacemaker uses rate smoothing, and mode switches occur when mean sensed atrial rate exceeds the predefined AMS rate (MR). Marathon mode switches after a programmable number of consecutive rapid atrial events (NR). Meta DDDR monitors the atrial rate by a counter for atrial cycles faster than the programmed AMS rate. It increases or decreases the counter if the atrial cycle length is shorter or longer than the programmed AMS interval, respectively. Mode switch occurs when the AF detection criteria are met (CR). A total of 260 rhythms were studied. NR was significantly faster than MR and CR (latency 2.5 ± 3 svs 26 ± 7 s vs 15 ± 22 s, respectively, P < 0.0001). During sustained AF, MR resulted in the most stable and regular ventricular rhythm compared to NR or CR. In CR, ventricular rate oscillated between AMS and atrial tracking (cycle length variations: 44 ± 2 s vs 346 ± 109 s vs 672 ± 84 s, P < 0. 05). At resumption of sinus rhythm, MR resyn‐chronized after 143±22 s versus 3.4 ± 0.7 s for NR and 5.9 ± 1.1 s for CR, resulting in long periods of A V dissociation when a VVI/VV1R mode is used after AMS. Programming of atrial refractory periods did not affect AMS response, although the speed of AMS onset can be adjusted by programming of onset criteria in the Meta DDDR. AMS algorithms differ in their ability to handle recorded clinical atrial arrhythmias. The rapid‐responding algorithm exhibits rate instability, whereas slow responding algorithm shows a long delay in response and risk of AV dissociation. Thus different instrumentation of AMS may have clinical implications in patients with dual chamber pacemakers who develop AF.
Is Dual Site Better Than Single Site Atrial Pacing in the Prevention of Atrial Fibrillation?
Authors: LECLERCQ JEAN‐FRANÇOIS , DE SISTI ANTONIO , FIORELLO PIERRE , HALIMI FRANCK , MANOT STEPHANIE , ATTUEL PATRICK
Published: June 2006

Long‐term prevention of atrial fibrillation is not constantly realized by single‐sits right atrial pacing, and the beneficial role of multisite atrial pacing is still being studied. Accordingly, we compared the effectiveness of dual site and single site atrial pacing in 83 patients (50 men, 33 women, aged 69 ± 10 years), who received a DDD device for primary sinus node dysfunction or bradycardia with documented atrial fibrillation. Inclusion criteria for dual site pacing were a sinus P wave ≥ 120 ms and at least two episodes of documented paroxysmal AF in the 6 months preceding implantation. Dual site atrial pacing (high right atrium‐coronary sinus ostium) was performed in 30 cases, and was compared to 53 single site paced patients, 21 with a P wave ≥ 120 ms and 32 with a P wave < 120 ms. The basic pacing rate was programmed at 68 ± 4 beats/min (range 60–75 beats/min). Sinus P wave (133 ± 20 vs 95 ± 9 ms; P < 0.001), paced P wave (107 ± 14 vs 99 ± 15; P < 0.05), number of antiarrhythmic drugs used (2.4 ±1.2 vs 1.6 ± 1.5, P < 0.05), and the duration of symptoms (8.1 ± 4.5 vs 3.8 ± 2.4 years; P < 0.001) were significantly higher in dual site patients. The other characteristics were similar. During the follow‐up of 18 ± 15 months (range 3–30 months), paroxysmal AF was documented in 33 patients. Among these patients, 13 developed permanent AF following at least one episode of paroxysmal AF. When comparing dual site patients and single site patients with a P wave duration ≥ 120 ms, paroxysmal AF incidence was lower in the dual site group (9/30 patients vs 15/21 patients, P < 0.01), as well as permanent AF (1/30 patients vs 8/21 patients, P < 0.01). By contrast, comparison between dual site patients and the group of single site patients with a P wave duration < 120 ms did not evidence any significant differences in paroxysmal (9/30 patients vs 9/32 patients) and permanent (1/30 patients vs 4/32 patients) AF incidences. Dual site seems better able than single site atrial pacing to improve the natural history of patients with a prolonged P wave, reducing the incidence of paroxysmal and permanent AF. No benefit could be expected in patients with a normal P wave duration.
Lead Noise with an Active‐Fixation Defibrillation Lead
Authors: GELDER ROBERT N. , GALVIN JOSEPH M. , ALBERT CHRISTINE M. , KEANE DAVID , RUSKIN JEREMY N.
Published: June 2006

Inappropriate detection and therapy is the most common adverse affect of implantable cardioverter defibrillator therapy. One mechanism is lead artifact, which usually presents late and is due to stress and fatigue of the lead components. Our experience with a defibriliator lead (Endotak Endurance EZ leads, Models 0154/0155/0156) and its method of active fixation is described. Of 20 implants with this lead, four patients were found to have noise that resulted in inappropriate detections in three. No patient received therapy as a consequence of these detections. The artifact appeared soon after implant and resolved in three of four cases by 4 weeks. None of the 16 remaining patients developed noise after this time. This is a unique lead problem that resolves with time, but it may result in inappropriate therapies and difficult management decisions in high risk patients with ventricular arrhythmias.
Iatrogenic Ventricular Tachycardia from Endocardial Pacemaker Late After Repair of Tetralogy of Fallot
Authors: LI WEI , SARUBBI BERARDO , SOMERVILLE JANE
Published: June 2006

A 34‐year‐old woman, who had undergone radical repair for tetralogy of Fallot at the age of 8 years, was left with moderate‐to‐severe pulmonary regurgitation. VT developed after endocardial pacing for symptomatic pauses and at rial flutter. The possibility that the new VT originated from the apical endocardial lead was suggested by the unusual morphology of the VT, which was similar to paced. Surgical removal of the lead, which was deeply embedded at the same time as a pulmonary valve was replaced, cured the arrhythmia. This unusual cause of VT highlights possible risks associated with setting up a dangerous reentry circuit by inserting a right ventricular endocardial pacemaker lead.
Permanent Pacing from a Left Ventricular Vein in a Patient with Persistent Left and Absent Right Superior Vena Cava
Authors: BIRNIE DAVID , TANG ANTHONY S.L.
Published: June 2006

Persistent left superior vena cava with coexisting absent right superior vena cavn is rare with less than 150 cases in the literature. Various techniques for pacemaker implantation have been described in this situation. We report a 40‐year‐old man with sinus and atrioventriciilar nodal dysfunction who underwent dual chamber pacemaker implantation. We elected to implant the ventricular electrode down a left ventricular branch of the coronary sinus and the lead is stable at 4‐month follow‐up.
Cardiopulmonary Resuscitation During Coronary Vasospasm Induced by Tilt Table Testing
Authors: WANG CHAO‐HUNG , HUNG MING‐JUI , KUO LI‐TANG , CHERNG WEN‐JIN
Published: June 2006

A 65‐year‐old man presented to our institution with recurrent episodes of early morning chest discomfort and near syncope. An ergonovine provocation test documented a diagnosis of coronary va‐sospastic angina. During our investigation of the syncope, a head‐up tilt table test provoked a severe episode of coronary vasospasm that resulted in a life‐threatening cardiac event. The present case reminds us that an elevation of ST segments on the electrocardiogram during tilt testing should be promptly managed as an attack of coronary vasospasm.
Pro arrhythmic Effects of Ibutilide in a Canine Model of Pacing Induced Cardiomyopathy
Authors: HSIEH MING‐HSIUNG , CHEN YI‐JEN , LEE SHIH‐HUANG , DING YU‐AN , CHANG MAU‐SONG , CHEN SHIH‐ANN
Published: June 2006

The authors developed a canine model of pacing induced cardio my apathy to study the possible mechanisms of ibutilide induced torsades de pointes (TP) in heart failure. Thirteen dogs received intravenous ibutilide after acute AV block for 60 minutes, and after implantation of a VVI pacemaker, with a rate of 270 beats/min for 2–3 weeks. Twelve‐lead ECG and right and left ventricle monophasic action potentials were recorded at different right ventricle pacing cycle lengths from 600 ms to 1200 ms during the study. The results showed ibutilide could significantly prolong ventricular repolarization and increase the dispersion in a dose dependent and reverse use dependent manner. Furthermore, after ihutilide administration, cardiomyopathic dogs had a greater dispersion of ventricular repolarization, and also had higher incidences of early afterdepolarizations and spontaneous or pacing induced TP than acute AV block dogs.
Importance of AV Synchronous Pacing During Low Intensity Exercise Evaluated by Oxygen Kinetics
Authors: RICKLI HANS , PETER HANS , ROCCA BRUNNER‐LA , MACCARTER DEAN J. , DURU FIRAT , CANDINAS RETO
Published: June 2006

It has been shown that dual chamber pacing with preservation of AV synchrony (ODD) is superior to fixed rate ventricular (VVI) or rate responsive ventricular (VVIR) pacing modes, as evaluated by ventilatory response to exercise. Previous studies have focused on the benefits of maintained AV synchrony at maximal exercise. However, there are limited data comparing O2 kinetics in different pacing modes during low intensity exercise, representing the majority of daily activities. This study aimed to provide an evaluation of different pacing modes using O2 kinetics during low intensity exercise. Nineteen patients (age 61 ± 18 years) with complete AV block underwent low intensity treadmill exercise (35 W) with simultaneous evaluation of symptoms and O2 kinetics in three pacing modes. The first test was performed in DDD mode followed by a second test in VVIR mode with a programmed heart rate corresponding to the sinus rate during the first test. After 6 minutes of each test, the mode was switched from DDD to VVIR and vice versa. The third test was performed in VVI mode at 70 beats/min. O2 kinetics were defined as O2 deficit (time [rest to steady state] ×Δ VO2—ΔVO2 [rest to steady state]) and mean response time (MRT) of oxygen consumption (O2 deficit/ΔVO2). The O2 deficit was 551 ± 134 ml in DDD pacing, 634 ± 139 mL in VVIR pacing, and 648 ± 179 mL in VVI pacing (P = 0.001). MRT was 49 ± 7.8 seconds in DDD pacing, 54.7 ± 9.5 seconds in VVIR pacing, and 57.4 ± 11.0 seconds in VVI pacing (P = 0.002). Ten (53%) patients developed symptoms during switch from DDD to VVIR mode whereas the switch from VVIR to DDD mode was not perceived by any patient (P < 0.001). In conclusion, our study shows an impact of AV synchronous pacing and heart rate adaptation on O2 kinetics during low intensity exercise that correspond to casual daily life activities. Our observations may have clinical implications for the management of patients with complete AV block.
Reproducibility of Response to Programmed Atrial Stimulation
Authors: BREMBILLA‐PERROT BÉATRICE , HOURIEZ PIERRE , CLAUDON OLIVIER , BEURRIER DANIEL , PREISS JEAN‐PHILIPPE , DE LA CHAISE ARNAUD TERRIER , LOUIS PIERRE
Published: June 2006

The induction of atrial tachyarrhythmias (ATAs) is used to guide the medical or ablative treatment of these tachycardias. To date no information is available regarding the reproducibility of programmed atrial stimulation (PAS) induced ATA. The purpose of the study was to look for the reproducibility of PAS. Two baseline electrophysiological tests were performed in the drug‐free state and within 6 months to 3 years of one another (mean 18 months) in 62 patients. Twenty‐six patients had spontaneous documented A TAs (group I); 36 patients did not have spontaneous ATAs (group II). PAS used one and two extrastimuli delivered during three cycle lengths (sinus rhythm, 600 ms, 400 ms). The results were as follows. In group I, sustained (< 1 minute) ATA was induced in 23 patients on the first PAS and remained inducible in 22 patients in the second study. In three patients with noninducible ATA, PAS remained negative in only one; the reproducibility of PAS was 88%. In 17 (47%) group II patients, a sustained ATA was induced in the first study, and the ATA remained inducible in 10 patients in the second study. Nineteen other patients did not have inducible ATA on the first study, but 10 of them had an inducible ATA on the second PAS; the reproducibility of PAS was 53%. In conclusion, long‐term reproducibility of PAS induced ATA in patients with spontaneous and documented ATA was good. In patients without spontaneous ATA, the reproducibility of PAS induced ATA was low and the induction of ATA in these patients should be interpreted cautiously in light of this observed variability in induced atrial arrhythmias.
The Effect of Ibutilide on Retrograde Accessory Pathway Conduction
Authors: SORBERA CARMINE , COHEN MARTIN
Published: June 2006

Ibutilide is a compound with Class III effects marketed for rapid conversion of atrial fibrillation and atrial flutter. The Class III effect is primarily mediated by blockade of the rapid component of the cardiac delayed rectifier of potassium current, Ikr. Ibutilide was used in three patients with concealed accessory pathways during electrophysiological evaluation for ablation of symptomatic atrioventricular reentry tachycardia. Each pathway (mid‐septal, left posterior, and left lateral) exhibited a mean retrograde effective refractory period of 240 ± 20 ms. Each patient had atrioventricular reentry tachycardia that consistently degenerated to recurrent sustained atrial fibrillation. One to two milligrams of intravenous ibutilide converted atrial fibrillation to sinus rhythm and maintained sinus rhythm throughout the procedure. Retrograde accessory pathway conduction was unchanged. Maintenance of sinus rhythm allowed for successful mapping and catheter ablation of the concealed accessory pathways. No direct current cardioversion was needed. In these patients, ibutilide was effective in converting and controlling atrial fibrillation induced by atrioventricular reentry tachycardia without masking retrograde pathway conduction. Antegrade accessory pathway conduction could not be assessed in this study.
QRS Amplitude and Shape Variability in Magnetocardiograms
Authors: HUCK MARKUS , HAUEISEN JENS , HOENECKE OLAF , FRITSCHI TORSTEN , LEDER UWE , NOWAK HANNES
Published: June 2006

In magnetocardiography, averaging of QRS complexes is often used to improve the signal‐to‐noise ratio. However, averaging of QRS complexes ignores the variation in amplitude and shape of the signals caused, for example, by respiration. This may lead to suppression of signal portions within the QRS complexes. Furthermore, for inverse source, reconstructions of dipoles and of current density distributions errors in the special arrangement may occur. To overcome these problems we developed a method for separating and selective averaging QRS complexes with different shapes and amplitudes. The method is based on a spline interpolation of the QRS complex averaged by a standard procedure. This spline function then is fitted to each QRS complex in the raw data by means of nonlinear regression (Levenberg‐Marquardt method). Five regression parameters are applied: a linear amplitude scaling, two parameters describing the baseline drift, a time scaling parameter, and a time shift parameter. We found that both amplitude and shape of the QRS complex are influenced by respiration. The baseline shows a weaker influence of the respiration. The regression parameters of two neighboring measurement channels correlate linearly. Thus, selective averaging of a larger number of sensors can be performed simultaneously.
Catheter Ablation of Atrioventricular Junction via Retrograde Route in a Patient with Single Ventricle
Authors: KERN JEFFREY H. , ROSENBAUM MARLON , HORDOF ALLAN J.
Published: June 2006

Radiofrequency catheter ablation of the atrioventricular junction (AVJ) was performed by the retrograde route in a 19‐year‐old woman with atrial fibrillation and single ventricle following the bidirectional Glenn procedure. Two energy applications resulted in complete atrioventricular block and dependence on an epicardial ventricular pacemaker.
Long‐Term Outcome of Patients with Multiple (≥ 3) Noninfected Transvenous Leads: A Clinical and Echocardiographic Study
Authors: DE COCK CAREL C. , VINKERS MAARTEN , VAN CAMPE LINDA C.M.C. , VERHORST PATRICK M.J. , VISSER GEES A.
Published: June 2006

To prospectively assess the incidence and clinical significance of thromboembolic complications in patients with multiple (≥ 3) noninfected transvenous leads; 48 consecutive patients were evaluated. Half of the patients had two ventricular leads and one atrial lead, 15 patients had two atrial leads and one ventricular lead, while 9 patients had two ventricular and two atrial leads. No additional care was provided except for aspirin (80 mg bid) and annually performed echo‐Doppler studies. Clinical follow‐up included signs and symptoms of subclavian and/or axillary vein thrombosis, the presence of right congestive heart failure, the number of hospital admissions, and death. Echo‐Doppler studies assessed the presence of an enlarged right atrium or ventricle, right atrial or ventricular spontaneous contrast, and the presence of tricuspid regurgitation. During a total follow‐up of 7.4 ± 2.2 years there were no differences in the incidence of clinical variables as compared to age‐matched controls with DDD pacemakers. The most common complication was transient venous thrombosis (mostly presenting as venous prominence 1–2 weeks after implantation), which was seen in 17% of the study group versus 15% in controls (NS). Cumulative mortality was not different in both groups (13% in the study group vs 15% in controls). No differences were present with respect to hospital admissions (1.1 ± 0.27/year in the study group vs 1.2 ± 0.30/yearin the controls). In patients with multiple ventricular leads, tricuspid regurgitation on echo‐Doppler studies was more frequent (24%) as compared to controls (4%); however, clinical signs of right heart failure were equally distributed. Thus, patients with multiple (≥ 3) noninfected leads have no clinical adverse outcome during long‐term follow‐up.
The Effect of Psychological Intervention on Patients' Long‐Term Adjustment to the ICD: A Prospective Study
Authors: KOHN CAROLYNN S. , PETRUCCI RALPH J. , BAESSLER CHRIS , SOTO DESIREE M. , MOVSOWITZ COLIN
Published: June 2006

This study prospectively examined the role of cognitive behavioral therapy (CBT) in (1) alleviating psychological and somatic distress, and (2) lowering arrhythmic events requiring shocks. Forty‐nine of 61 consecutive patients were randomized into therapy (CBT, n = 25) or no therapy (NT. n = 24) and completed a battery of self‐report questionnaires at baseline and at 9‐month follow‐up. CBT was administered at preimplant, predischarge, and at seven routine follow‐up visits. Patients were 65 ± 10 years old. 65% were men, and 92% Caucasian. Eighteen (72%) CBT patients and 18 (75%) NT patients were retained at follow‐up. Compared to CBT patients, NT patients reported higher levels of depression (P = 0.046), more anxiety (P = 0.013), more psychological distress (P = 0.015), poorer overall adjustment (P = 0.009), and poorer sexual functioning (P = 0.003). Mean number of shocks did not differ between the CBT and NT groups (2.85 vs 2.30. respectively); however, more patients in the CBT group (61%) than the NT group (33%) received shocks (P = 0.070). At follow‐up, a subgroup analysis revealed that the significant differences observed between the CBT and NT groups were attributable to the patients who received shocks in both groups. In conclusion, CBT was associated with decreased depression, decreased anxiety, and increased adjustment for ICD recipients, particularly among those patients receiving shocks. CBT can be administered effectively at routine follow‐up visits or transtelephonically with little added inconvenience to the ICD recipient.