bluuebunny/crossref_metadata_2025 huggingface dataset:
Atrial Fibrillation Induction and Determination of Atrial Vulnerable Period Using Very Low Energy Synchronized Biatrial Shock in Normal Subjects and in Patients with Atrial Fibrillation
Authors: TSE HUNG‐FAT , LAU CHU‐PAK , AYERS GREGORY M.
Published: June 2006

The atrial vulnerable periods (A VP)for shock induction of atrial fibrillation (AF) in humans have not been clearly defined. Furthermore, the safety and efficacy of using low energy biatrial shock delivered transvenously for AF induction are unknown. We tested the safety and efficacy of using very low energy biatrial shocks, delivered between the right atrium and the coronary sinus for AF induction and used this technique to characterize the A VP in nine controls and nine patients with AF. Thirty‐volt and 60‐V 3/3‐ms biphasic shocks were delivered, starting from 50 ms before the atrial effective refractory period with 20‐ms increments until the end of the QRS interval to determine the AVP front, AVP end, and the AVP duration. Successful AF induction could be achieved in eight (89%) of the nine controls and in nine (100%) of the nine patients with AF without any complication. In patients with AF, the AVP front started significantly earlier within the QRS complex, and the AVP duration and the AVP duration/QRS percent ratios were also significantly greater as compared to controls. Furthermore, a higher induction shock energy in patients with AF was associated with an increase in AF inducibility and significantly increased the AVP duration and A VP duration/QRS percent ratio as compared to the controls. This study demonstrated the safe and efficacy of delivering a very low energy biatrial shock during the AVP within the R wave for AF induction. The characteristics of A VP in patients with AF were significantly different from normal subjects.
Age Related Changes in Dual AV Nodal Physiology
Authors: BLAUFOX ANDREW D. , RHODES JOHN F. , FISHBERGER STEVEN B.
Published: June 2006

Dual atrioventricular nodal (DAVN) physiology has been reported in up to 63% of pediatric patients with anatomically normal hearts, yet atrioventricular nodal reentrant tachycardia (AVNRT) accounts for only 13%–16% of supraventicular tachycardia (SVT) in childhood. The incidence of AVNRT increases with age and becomes the most common form of SVT by adolescence. We investigated the age related electrophysiological responses to programmed atrial and ventricular stimulation in 14 pediatric patients who underwent intracardiac electro‐physiological study prior to radiofrequency catheter ablation for AVNRT and who exhibited DAVN physiology. Single atrial and ventricular extrastimuli were placed following drive trains with cycle lengths of 400–700 ms and 350–500 ms, respectively. Six children (mean age 8.2 years, range 5.2–11.5 years) were compared to eight adolescents (mean age 16.6 years, range 13.3–20.7 years). Adolescents were found to have a significantly longer fast pathway effective refractory period (ERP) (median 375 vs 270 ms, P = 0.03), slow pathway ERP (median 270 vs 218 ms, P = 0.04), atrio‐Hisian (AH) during AVNRT (median 300 vs 225 ms, P = 0.007), and AVNRT cycle length (median 350 vs 290ms, P = 0.03). There was a strong trend for the AH measured at the fast pathway ERP to be longer in adolescents than in children (median 258 vs 198 ms, P = 0.055). The AH at the fast pathway ERP was more strongly correlated with baseline cycle length than with age (r = 0.7, P = 0.01 vs r = 0.5, P = 0.7). There was no significant difference in the retrograde VA conduction between adolescents and children. These results demonstrate an age related difference in AV nodal response to programmed atrial stimuli in pediatric patients with DAVN physiology and AVNRT. These differences are consistent with mechanisms that may explain the increased incidence of AVNRT in adolescents compared to children.
Serial Lead Impedance Measurements Confirm Fixation of Helical Screw Electrodes During Pacemaker Implantation
Authors: ROELKE MARC , BERNSTEIN ALAN D. , PARSONNET VICTOR
Published: June 2006

The purpose of this study was to determine whether serial measurements of helical screw pacemaker lead impedance could reliably confirm electrode fixation in the right atrium and right ventricle. Fixation is generally assessed fluoroscopically, which can be misleading because the myocardium is radio lucent. Alternatively, because the electrical conductivity of blood is greater than that of myocardium, serial measurements of the lead impedance might be expected to show an impedance increase with appropriate fixation of the pacemaker electrode when the electrode becomes embedded in myocardial tissue. Impedance measurements were made during the placement of 23 atrial and 28 ventricular active fixation electrodes in 31 consecutive patients. Impedance measurements were recorded in unipolar and bipolar electrode configurations with the electrode free floating in the chamber, unfixed (with exposed screws) but touching the endocardial surface, and after fixation. No significant impedance differences were found between free‐floating and unfixed electrode positions. With fixation, the lead impedance increased significantly in the ventricle (P = 0.0001, unipolar and bipolar) and the atrium (P = 0.0069 unipolar and 0.0052 bipolar). Typical increases, reflected by median values, were 197 ohms unipolar and 203 ohms bipolar in the ventricle and 47 ohms unipolar and 53 ohms bipolar in the atrium for electrodes with permanently exposed or retractable screw designs. Comparing serial measurements of lead impedance before and after electrode fixation is a valid electrical method of confirming appropriate fixation of helical screw electrodes.
Tilt Training: A Treatment for Malignant and Recurrent Neurocardiogenic Syncope
Authors: REYBROUCK TONY , HEIDBÜCHEL HEIN , VAN DE WERF FRANS , ECTOR HUGO
Published: June 2006

The treatment of neurocardiogenic syncope is insufficient in many cases. We hypothesized that the repeated exposure of the cardiovascular system to orthostatic stress could have a therapeutic effect on the regulation of cardiovascular reflex mechanisms. We have started a program of tilt training for heavily symptomatic patients. After hospital admission, patients were tilted daily (60‐degree inclination), until syncope, or until a maximum of 45–90 minutes. The patients were instructed to continue a program of daily tilt training at home: two 30‐minute sessions of upright standing against a vertical wall. No medication was prescribed. A total of 260 tilt table sessions were performed in 42 patients. The first tilt test was positive after 21 ± 13 minutes. The syncope was cardioinhibitory in 14 cases, vasodepressor in 19, mixed in 9. At the time of hospital discharge, 41 patients could support 45 minutes of head‐up tilting. After a mean follow‐up time of 15.1 (SD 7.8) months, 36 patients remained completely free of syncope. Syncope still occurred in one patient and presyncope in four patients. One patient died from an extensive myocardial infarction. The abnormal autonomic reflex activity of neurocardiogenic syncope can be remedied by a program of continued tilt training without the administration of drugs. This new treatment has proven to be effective for the vasodepressor and the cardioinhibitory type of syncope.
Effect of Rates of Perfusion on Dominant Frequency and Defibrillation Energy in Isolated Fibrillating Hearts
Authors: BARTON CHRISTOPHER W. , CASCIO WAYNE E. , BATSON DAVID N. , ENGLE CONNIE L. , JOHNSON TIMOTHY A.
Published: June 2006

This study assessed the influence of rates of reperfusion on excitability of the myocardium using dominant frequency (DF) (in Hz) of VF and the relationship of DF to the minimum de‐fibrillation energy (MDE) (in J). Our hypothesis was that increasing flow during reperfusion increases DF that raises MDE. Initially, six Langendorff perfused swine hearts were serially fibrillated and perfusion arrested for 4 minutes followed by reperfusion and defibrillation to establish reproducibility of the model. The epicardial ECG was analyzed for DF. In subsequent studies (n = 8), no flow VF was followed by 1‐minute reperfusion at normal flow or 10% flow (low flow) and shocked with increasing energy via epicardial pads until defibrillation. The DF at onset of no flow VF was 9.5 ±1.4 and decreased to 3.6 ±1.4 after 4 minutes. Reperfusion at normal flow increased the DF of VF compared to low flow after 1 minute (10.8 ± 1.1 vs 4.5 ± 1.1 Hz, P = 0.0002) and was associated with increased defibrillation energy requirements (13.5 ± 5.0 vs 7.3 ± 6.2 J, P = 0.047). In summary, defibrillation energy requirements are lower when myocardial excitability is reduced during low flow reperfusion.
Using Intracardiac Catheter Recordings from the His and Proximal Coronary Sinus to Distinguish Isthmus Conduction Block During Catheter Ablation of Type I Atrial Flutter
Authors: SARTER BRIAN H. , CALLANS DAVID J. , MAN DAVID C. , COYNE ROBERT F. , SCHWARTZMAN DAVID , GOTTLIEB CHARLES D. , MARCHLINSKI FRANCIS E.
Published: June 2006

Isthmus conduction block, demonstrated with the use of multipolar catheter recordings, is considered the preferred endpoint for ablation of type I atrial flutter. This study investigated the feasibility of using recordings from the His and coronary sinus (CS) to document isthmus conduction block. Isthmus conduction block was produced with linear radiofrequency (RF) ablation in 27 patients with type I atrial flutter. In 13 patients (group I), RF was delivered until bidirectional isthmus conduction block was demonstrated with multipolar Halo catheter recordings. In 14 patients (group II), RF was delivered during pacing from the lateral isthmus at 600 ms until a reversal in activation of the proximal CS and His occurred. At this point, data from the Halo recordings were reviewed to see if reversal correlated with conduction block; if not, further ablation was performed until block was demonstrated. The initial reversal in His and CS activation during RF energy delivery correlated with isthmus block in only 4 (28.6%) of 14 patients in group II. Additional RF delivery produced isthmus block in the other ten patients resulting in a further increase in the St‐CS interval of 35 ± 20 ms. A His‐CS interval of at least ‐40 ms signified isthmus block with a sensitivity and specificity of 48% and 100%, respectively. Reversal in His‐CS activation during pacing from the lateral margin of the isthmus is not specific for the creation of isthmus block. While activation of the proximal CS bipole > 40 ms after activation of the His appears specific for isthmus block, the low sensitivity of this finding limits its clinical use.
Exercise Induced Atrioventricular Block with Gap Phenomenon in Atrioventricular Conduction
Authors: TOEDA TETSURO , SUETAKE SHYUJI , TSUCHIDA KEIICHI , TAKAHASHI KAZUYOSHI , MIIDA TSUTOMU , ODA HIROTAKA , HIGUMA NORIO
Published: June 2006

A 54‐year‐old man with normal atrioventricuiar (AV) conduction at rest gave a 4‐year history of presyncope during exercise. Treadmill testing showed exercise induced AV block. Electrophysiological study demonstrated rate dependent infranodal AV block and abnormal refractory period of the His‐Purkinje system. The gap phenomenon in AV conduction occurred during the programmed stimulation. Supernormal conduction could be considered as the mechanism of the gap phenomenon in this patient.
His‐Purkinje System Reentry As a Pro arrhythmic Effect of Flecainide
Authors: CHALVIDAN T. , CELLARIER G. , DEHARO J.C. , COLIN R. , SAVON N. , BARRA N. , PEYRE J.P. , DJIANE P.
Published: June 2006

We report a case of tachycardia due to reentry within the His‐Purkinje system (HPS) occurring after introduction of flecainide. The patient presented with a mild mitral regurgitation and normal left ventricular function. He had incomplete left bundle branch block with left‐axis deviation. At the electrophysiology study, a prolonged HV interval was observed at baseline, and the tachycardia could be reproduced after ajmaline infusion. Six months after interruption of flecainide, the patient remains free of arrhythmia recurrence. The authors emphasize that proarrhythmic effects of flecainide may include reentry within the HPS in patients with underlying HPS disease.
Ventricular Tachycardia in a Patient with Primary Hyperparathyroidism
Authors: CHANG CHIEN‐JUNG , CHEN SHIH‐ANN , TAI CHING‐TAI , YU WEN‐CHUNG , CHEN YI‐JEN , TSAI CHIN‐FENG , HSIEH MING‐HSIUNG , DING YU‐AN , CHANG MAU‐SONG
Published: June 2006

We present a case of primary hyperparathyroidism with hypercalcemia in a patient who had spontaneous attacks of ventricular tachycardia. Right ventricular burst pacing reproducibly induced ventricular tachycardia in the electrophysiological laboratory after intravenous administration of calcium‐gluconate, and verapamil could terminate the tachycardia. After resection of the parathyroid adenoma, the calcium level was restored to normal, and ventricular tachycardia did not occur again during the follow‐up period,
Dissection of the Coronary Sinus Secondary to Pacemaker Lead Manipulation
Authors: WALKER STUART , LEVY TERRY , PAUL VINCE E.
Published: June 2006

We report a 64‐year‐old man with atrial fibrillation and impaired left ventricular function in whom pacemaker lead manipulation during biatrial pacemaker lead removal and biventricular pacemaker lead insertion caused coronary sinus dissection. After further manipulation of the biventricular pacing lead, the true lumen of the coronary sinus could be entered and satisfactory left ventricular pacing undertaken. The dissection was managed conservatively without long‐term sequelae.
Atrial Electrophysiological Effects of Ibutilide Infusion in Humans
Authors: SCHWARTZ ROBERT A. , LANGBERG JONATHAN J.
Published: June 2006

Patients with persistent atrial fibrillation (AF) who respond to ibutilide infusion usually convert to sinus rhythm within 1 hour. However, little is known about the magnitude and time course of the drug's atrial electro‐physiological effects. In the current study, the frequency content of the fibrillatory baseline on the ECG was used to quantify the effects of ibutilide infusion on AF. Nineteen patients (age 56 ± 16 years) in persistent AF were studied. Nine of these were chronically treated with antiarrhythmic drugs. All subjects received ibutilide (1 mg IV) over 10 minutes and a second dose 10 minutes later as needed. An ECG was recorded and digitized throughout each of the 20 sessions (one patient had two separate cardioversions). A signal processing technique was then used to quantify the average rate of the fibrillatory baseline. After attenuating the QRS and T waves, the ECG was subjected to Fourier transformation. The average rate of fibrillatory activity was defined as the frequency corresponding to the peak power of this spectrum. The fibrillation rate declined by 20 ± 12% during the initial dose of ibutilide. This effect was rapid with t1/2= 4.2 minutes. Ibutilide induced slowing of AF was more intense and more rapid in patients who converted to sinus rhythm than in those who did not (25 ± 5% vs 18 ± 14% drop in rate, t1/2 3.4 minutes vs 6.3 minutes, P ‐ 0.002). Ibutilide induced slowing of fibrillatory activity occurs rapidly and approaches steady state before the end of a 10‐minute infusion. Although interaction with other antiarrhythmic drugs may have confounded the results, the speed and intensity of slowing correlated with conversion. These observations suggest that additional studies are warranted to determine if ibutilide dosing regiments can be optimized.
An Association Between Anxiety and Neurocardiogenic Syncope During Head‐Up Tilt Table Testing
Authors: COHEN TODD J. , THAYAPRAN NALLATHAMBY , IBRAHIM BASSIEMA , QUAN CINDY , QUAN WEILUN , VON ZUR MUHLEN FRIEDERIKE
Published: June 2006

To study the association between anxiety and neurocardiogenic syncope as determined by head‐up tilt table testing (HUT) in men and women with presyncope or syncope, patients with unexplained syncope or presyncope undergoing HUT were asked to complete the Burns Anxiety Inventory (BAI), a validated inventory of 33 questions with responses graded from 0 to 3. HUT consisted of a 30‐minute tilt to 60 degrees, which if negative, was repeated with an isoproterenol infusion. A positive HUT was defined as symptomatic hypotension and/or bradycardia. Of the 66 patients who completed the BAI and underwent HUT, 33 were men and 33 were women, The mean age was 57 ± 18 years (17–91 years). Patients with a positive HUT had a higher BAI score than those with a negative HUT (22 ± 12 vs 14 ± 13, P = 0.017). This association was stronger in women with a BAI score of 24 ± 11 in those with a positive HUT versus 13 ± 8 in those with a negative HUT (P = 0.005). In contrast, the mean BAI score for men with a positive HUT was 19 ± 13, as compared to 15 ± 16 fora negative HUT (P = 0.5). In conclusion, the present study demonstrates a statistical association between anxiety (as determined by BAI) and HUT result. Gender‐based analysis revealed a more statistically significant relationship between anxiety and HUT outcome for women as compared to men.
Infarct Related Artery Patency: Relation to Serial Electropharmacological Studies and Outcome in Patients with Previous Myocardial Infarction and Ventricular Tachyarrhythmias
Authors: HOPPE UTA C. , HAVERKAMP WILHELM , BREITHARDT GÜNTER , BORGGREFE MARTIN
Published: June 2006

Evidence suggests that infarct related artery (IRA) patency may improve survival after acute myocardial infarction, which is thought to be partially due to a lower incidence of malignant ventricular tachyarrhythmias. However, little is known about the effect of IRA patency on antiarrhythmic drug response and long‐term outcome in patients with previous infarction who already experienced sustained ventricular tachyarrhythmias. A total of 152 patients with remote myocardial infarction and documented ventricular tachycardia (VT) or ventricular fibrillation (VF) underwent coronary angiography and programmed ventricular stimulation before and after oral administration of d,l‐sotalol (240–640 mg/day). D.l‐sotalol suppressed inducibility of VT/VF in 37 (25.2%) patients. The IRA was patent in 38.1% of all patients. There was no significant difference in the frequency of drug response between patients with patent or occluded IRAs (26.8% vs 24.2%, P = 0.87). In patients with a patent IRA, d.l‐sotalol tended to be more effective in the absence of a left ventricular aneurysm. although this difference did not reach statistical significance (P = 0.38). Ejection fraction and collateral blood flow had no effect on drug response in the presence or absence of IRA patency. During follow‐up (13.0 ± 19.9 months) of 29 patients discharged on oral d,1‐so‐talol, 3 patients experienced symptomatic VT and 4 sudden death. Arrhythmia recurrence and death of all cause (n = 6) and cardiac death (n = 4) were independent of IRA patency status. IRA patency had no effect on short‐term drug response to d,1‐sotalol in patients with remote myocardial infarction and documented VT/VF. Long‐term outcome of patients with sustained ventricular tachyarrhythmias is independent of IRA patency status. In contrast to a previous report, outcome of electropharmacological testing was not predicted by the patency of the IRA.
Age Dependency of Sensing Performance and AV Synchrony in Single Lead VDD Pacing
Authors: WIEGAND UWE K.H. , POTRATZ JÜRGEN , BODE FRANK , SCHNEIDER REGINA , PETERS WERNER , BONNEMEIER HENDRIK , KATUS HUGO A.
Published: June 2006

Implantation of single lead VDD pacemakers is an established therapeutic option in patients with AV block and normal sinus node function. However, related to occurrence of sinus node disease and atrial undersensing, there is concern whether VDD devices are appropriate in physically active young patients. Two hundred thirty‐two consecutive patients with isolated A V block and VDD pacemakers were investigated. This population was subdivided into quartiles of 58 patients according to age at time of inclusion: 26.2–59.4 years (group A), 59.5–70.1 years (group B), 70.2–81.0 years (group C), and 81.1–92.5 years (group D). Follow‐up visits included pacemaker telemetry, Holier monitoring, and exercise testing. Patients were visited at 2 and 12 weeks after implantation thereafter followed by 6‐month intervals. Mean follow‐up period was 35 ± 14 months. Three months after implantation, atrial sensing threshold was significantly higher in young patients: 1.18 ± 0.58 mV (group A) versus 0.79 ± 0.35 mV (group B), 0.68 ± 0.33 mV (group C), and 0.60 ± 0.25 mV (group D), P < 0.001 for comparison of group A to all other groups. Atrial undersensing was observed less frequently in young patients: 6.9% (group A) versus 17.2% (group B), 24.1% (group C), and 27.6% (group D), P = 0.025 for intergroup comparisons. Sinus node dysfunction did not occur in group A. Atrial arrhythmias and loss of AV synchronized pacing mode occurred rarely in young patients: 0.6% (0.4%) per year in group A versus 1.3% (1.3%) in group B, 3.9% (3.4%) in group C, and 5.7% (7.4%) per year in group D, P < 0.01 for intergroup comparisons. Our data show good atrial sensing performance, low incidence of sinus node dysfunction, and few atrial arrhythmias in young patients with VDD pacing for AV block. Thus, single lead VDD pacing can be recommended particularly for young patients with AV block.
Diagnosis and Management of Inadvertently Placed Pacing and ICD Leads in the Left Ventricle: A Multicenter Experience and Review of the Literature
Authors: VAN GELDER BERRY M. , BRACKE FRANK A. , OTO ALI , YILDIRIR AYLIN , HAAS P. CLAY , SEGER JOHN J. , STAINBACK RAYMOND F. , BOTMAN KEES‐JOOST , MEIJER ALBERT
Published: June 2006

Three patients from different centers with pacemaker or ICD leads endocardially implanted in the left ventricle are described. All leads, two ventricular pacing leads and one ICD lead, were inserted through a patent foramen ovale or an atrial septum defect. The diagnosis was made 9 months. 14 months, and 16 years, respectively, after implantation. All patients had right bundle branch block configuration during ventricular pacing. Chest X ray was suggestive of a left‐sided positioned lead except in the ICD patient. Diagnosis was confirmed with echocardiography in all patients. One patient with a ventricular pacing lead presented with a transient ischcmic attack at 1‐month postimplantation. During surgical repair of the atrial septum defect 14 months later, the lead was extracted and thrombus was attached to the lead despite therapy with aspirin. The other patients were asymptomatic without anticoagulation (9 months and 16 years after implant). No thrombus was present on the ICD lead at the time of the cardiac transplantation in one patient. We reviewed 27 patients with permanent leads described in the literature. Ten patients experienced thromboembolic complications, including three of ten patients on antiplatelet therapy. The lead was removed in six patients, anticoagulation with warfarin was effective for secondary prevention in the four remaining patients. In the asymptomatic patients, the lead was removed in five patients. In the remaining patients, 1 patient was on warfarin, 2 were on antiplatelet therapy, and in 3 patients the medication was unknown. After malposition was diagnosed, three additional patients were treated with warfarin. In conclusion, if timely removal of a malpositioned lead in the left ventricle is not preformed, lifelong anticoagulation with warfarin can be recommended as the first choice therapy and lead extraction reserved in case of failure or during concomitant surgery.
Prevalence of Late Potentials in a Sample of 487 Healthy, Middle‐Aged Men from Southwestern France
Authors: MARQUES‐VIDAL PEDRO , RUIDAVETS JEAN‐BERNARD , PROUTEAU NATHALIE , CASTEIGNAU GAËLLE , DELAY MARC , FERRIÈRES JEAN
Published: June 2006

Late potentials (LPS) have been shown to be predictive of ventricular tachycardia in coronary artery disease subjects, but the prevalence of LP in the general population is not as well‐known. The study included 487 men without a history of cardiovascular disease (aged 50–59) living in Southwestern France. Standard‐averaged high resolution electrocardiogram was performed using Butterworth filtering at 40–250 Hz. LPS were defined as two or more of the following criteria: QRS > 114 ms, duration of the low amplitude signals in the terminal portion of QRS > 38 ms, root mean square (RMS) voltage of the last 40 ms < 20μV. The mean QRS duration was 97 ± 12 ms (mean ± SD), duration of the low amplitude signals in the terminal portion of QRS was 32 ± 10 ms, and RMS voltage in the last 40 ms was 39 ± 27 μV. Eight percent of subjects (95% confidence interval [CI]: 6%–l 1 %) had a QRS duration > 114 ms; 22% (95% CI: 18%–26%) had a duration of low amplitude signals > 38 ms, and 25% (95% CI: 22%–29%) had RMS voltage in the last 40 ms < 20 μV. Finally, the prevalence of LP was 21 % (95% CI: 18%–25%). In conclusion, according to commonly used criteria, the prevalence of LP in this healthy population of middle‐aged men is 21 %, close to the values found in the literature for myocardial infarction patients. Those findings indicate the need for reconsidering the definition of LPS.
ICD Hardware Failure Associated with Multiple Internal Shocks
Authors: NAIR LAWRENCE A. , OSTROW ELIOT L. , BECK BRYAN
Published: June 2006

The delivery of 37 shocks by an ICD within 20 minutes, in response to T wave oversensing during atrial flutter, resulted in several manifestations of undesirable device behavior. The generator reverted to backup mode, and disabled automatic capacitor reformation, therapy delivery, and automatic gain control. Postexplant analysis of the device revealed damage to the high voltage output section of the circuitry consistent with excessive electrical stress. In rare circumstances, multiple internal discharges can result in serious clinical anomalies in ICD behavior, and possibly in an increase in susceptibility to circuitry damage.
Radiofrequency Ablation of an Accessory Pathway in a Surgically Created Atrioventricular Fontan Anastomosis: Case Report and Review of Previous Published Cases
Authors: LIBERMAN LEONARDO , PASS ROBERT H. , ALFAYYADH MAJID I. , HORDOF ALLAN J.
Published: June 2006

Supraventricular tachyarrhythmias following the Fontan procedure can be life‐threatening. Though most are commonly due to intraatrial reentry, orthodromic reentrant tachycardia may also be present. Atrioventricular accessory pathways may develop across suture lines following right atrial to right ventricular anastomosis in patients with tricuspid atresia. We report a case of a patient who underwent this type of Fontan who developed orthodromic reentrant tachycardia and heart failure. An electrophysiological study revealed the presence of an atrioventricular accessory pathway traversing the Fontan anastomosis suture line. Successful radiofrequency ablation of the accessory pathway led to control of the tachyarrhythmia and improvement of heart failure.
Block of the Lower Interatrial Connections: Insight into the Sources of Electrocardiographic Diversities in Common Type Atrial Flutter
Authors: ZRENNER BERNHARD , NDREPEPA GJIN , KARCH MARTIN , SCHNEIDER MICHAEL , SCHMITT CLAUS
Published: June 2006

Whether the conduction disturbances of the interatrial connections play a role in the genesis of ECG variants of atrial flutter is almost completely unknown. We present a patient with typical counterclockwise atrial flutter in whom the ablation of the coronary sinus (CS) area during ongoing atrial flutter produced significant ECG changes without alterations in the activation sequence within the right atrium (RA). This case highlights the possible role of alterations of the interatrial connections in the genesis of atypical ECG manifestations of common type, atrial flutter.
Electrophysiological and Anatomic Heterogeneity in Evolving Canine Myocardial Infarction
Authors: HORVATH GEORGE , RACKER DARLENE K. , GOLDBERGER JEFFREY J. , JOHNSON DAVID , JAIN SANDEEP , KADISH ALAN H.
Published: June 2006

Although the heterogeneity of electrophysiological properties is increased after myocardial infarction, the degree of this heterogeneity has not been well quantitoted and its relationship to the histoslogical changes that occur after infarction has not been carefully examined. The purpose of the present study was to test the hypothesis that alterations in electrophysiological properties in healing canine infarction are related to particular histological changes. Experimental infarction was produced by left anterior descending coronary ligation. Six dogs were used as controls, six were studied 5 days following, and six were studied 8 weeks following infarction. Pacing thresholds, effective refractory periods, and activation‐recovery times were determined at 112 sites on the anterior left ventricle using a multiple electrode plaque. Conduction velocity, conduction‐heterogeneity index—a measure of conduction disturbance—and histology of the epimyocardium underlying the plaque were assessed. The effective refractory periods and activation‐recovery times were greater in both infarction groups, most prominently in the subacute group. In subacute infarction, significant postrepolarization refractoriness was present. In healed infarction, conduction velocity was decreased and the conduction‐heterogeneity index was increased compared to controls and subacute infarction. Dispersion of excitability and repolarization was associated with more extensive local scarring. Dispersion of myocardial fiber angles was associated with the conduction‐heterogeneity index. Some but not all of the electrophysiological changes noted in the animals with infarction were also seen in sham operated animals. Thus, heterogeneity in repolarization and refractoriness is greatest in the subacute phase of myocardial infarction and is associated with the extent of local cell death. In contrast, disturbances in conduction are greatest in healed infarction and associated with disarray of myocardial fibers.
High Rate Atrial Tachyarrhythmia Detections in Implantable Pulse Generators: Low Incidence of False‐Positive Detections
Authors: FITTS STEPHANIE M. , HILL MICHAEL R.S. , MEHRA RAHUL , GILLIS ANNE M.
Published: June 2006

Some newer pulse generators have enhanced diagnostic features that provide information on the frequency, date, time of onset, and duration of atrial and/or ventricular tachyarrhythmias. However, the sensitivity and specificity of device‐based atrial tachyarrhythmia detections may vary and depend, in part, on lead position and selected programming parameters. The prevalence of inappropriate detections of paroxysmal atrial fibrillation (PAF) was investigated in 97 patients who received a Thera DR pacemaker 3 months prior to a planned AV node ablation. Patients were randomized to no atrial or to rate adaptive atrial pacing therapy and followed for 3 months. Following a total AV node ablation, patients were randomized to DDDE versus VDD pacing and followed for 1 year. The high rate atrial episode diagnostic feature was used for detection of PAF and the diagnostic data were retrieved during follow‐up visits. Criteria were developed to identify oversensing due to near‐field P wave detections, far‐field R wave detections, or competitive atrial pacing as causes of false‐positive atrial tachyarrhythmia detections. A total of 1,636 detections of PAF were recorded in patients preablation. Only 48 episodes (2.9%) were characterized as false‐positive detections; 25 episodes (1.5%) were classified as oversensing, and 23 episodes (1.4%) were classified as competitive atrial pacing. A total of 3,061 detections of PAF were recorded postablation. Only four episodes (0.1%) were classified as oversensing. Thus, the diagnostic atrial tachyarrhythmia detection feature in newer pacemakers is an effective method for evaluating the time course of PAF in patients with implantable pulse generators.
Experience with a Higher Impedance, Fixed Helix, Steroid‐Eluting Pacing Lead
Authors: GIUDICI MICHAEL C. , LEE MICHAEL , HIGGINS STEVEN , WEST GEORGE R. , MOELLER ANGELA K. , DECKER JASON B. ,   SWEET PICOTIP RX STUDY GROUP
Published: June 2006

A higher impedance, steroid‐eluting pacing lead was studied in a multicenter trial. A total of 132 leads were implanted in 61 patients and the electrical characteristics were compared with historical controls. The study lead had a lower pacing threshold at 3 months. 0.72 ± 0.33 versus 1.29 ± 0.82 in the atrium and 0.71 ± 0.25 versus 1.52 ± 0.52 in the ventricle (P < 0.01 for both). Impedance was significantly higher in the study lead, 923 ± 133 versus 719 ± 109 in the atrium and 980 ± 235 versus 664 ± 104 in the ventricle (P < 0.01 for both). Sensing was similar for both leads. The study lead's higher impedance values and low pacing thresholds combine to reduce pacing system energy requirements.
Increased Variance of P Wave Duration on the Electrocardiogram Distinguishes Patients with Idiopathic Paroxysmal Atrial Fibrillation
Authors: ANDRIKOPOULOS GEORGE K. , DILAVERIS POLYCHRONIS E. , RICHTER DIMITRIS J. , GIALAFOS ELIAS J. , SYNETOS ANDREAS G. , GIALAFOS JOHN E.
Published: June 2006

We hypothesized that the variance of P wave duration (P variance) in the 12‐lead ECG could reflect the spatial dispersion of P wave duration due to inhomogeneous and delayed propagation of sinus impulses in the atria, and moreover could present better reproducibility than maximum P wave duration and P wave dispersion that have already been used for the prediction of idiopathic paroxysmal AF, We also tested a semiautomated PC‐based method to improve the accuracy and reproducibility of P wave measurements. A 12‐lead ECG was obtained from 60 patients with idiopathic paroxysmal AF and from 50 healthy controls. All ECGs were analyzed manually using magnifying lens and calipers, while 20 randomly selected ones were scanned and analyzed on screen using common commercial software. P maximum, P dispersion, and P variance were all significantly higher in patients with paroxysmal AF than in controls. A P maximum value of 110 ms, a P dispersion value of 40 ms, and a P variance value of 120 ms2 separated patients from controls with a sensitivity of 88%, 83%, and 80%, respectively and a specificity of 75%, 85%, and 74%, respectively. The reproducibility of P variance was higher compared to P dispersion and P maximum. Finally, the PC‐based method significantly increased accuracy and reproducibility of P wave measurements. Thus, the variance of P wave duration could be a useful ECG marker for the prediction of paroxysmal idiopathic AF and the use of PC‐based methods may enhance the accurate measuring of P wave duration on the ECG.
Atrial Lead Placement During Atrial Fibrillation. Is Restitution of Sinus Rhythm Required for Proper Lead Function? Feasibility and 12‐Month Functional Analysis
Authors: WIEGAND UWE K.H. , BODE FRANK , BONNEMEIER HENDRIK , TÖLG RALPH , PETERS WERNER , KATUS HUGO A.
Published: June 2006

Unexpected atrial fibrillation (AF) during implantation of an atrial pacemaker lead is sometimes encountered. Infra‐operative cardioversion may lengthen and complicate the implantation process. This study prospectively investigates the performance of atrial leads implanted during AF (group A) and compares atrial sensing and pacing properties to an age‐ and sex‐matched control group in which sinus rhythm had been restored before atrial lead placement (group B). Patient groups consisted of 32 patients each. All patients received DDDE pacemakers and bipolar, steroid‐elating, active fixation atrial leads. In patients with AF at the time of implantation (group A), a minimal intracardiac fibrillatory amplitude of at least 1.0 mV was required for acceptable atrial lead placement. In patients with restored sinus rhythm (group B). a voltage threshold < 1.5 V at 0.5 ms and a minimal atrial potential amplitude > 1.5 mV was required. Patients of group A in whom spontaneous conversion to sinus rhythm did not occur within 4 weeks after implantation underwent electrical cardioversion to sinus rhythm. Pacemaker interrogations were performed 3, 6, and 12 months after implantation. In group A, implantation time was significantly shorter as compared to group B (58.7 ± 8.6 minutes vs 73.0 ± 17.3 minutes, P < 0.001). Mean atrial potential amplitude during AF was correlated with the telemetered atrial potential during sinus rhythm (r = 0.49, P < 0.001), but not with the atrial stimulation threshold. Twelve months after implantation, sensing thresholds (1.74 ± 0.52 mV vs 1.78 ± 0.69 mV, P = 0.98) and stimulation thresholds (1.09 ± 0.42 V vs 1.01 ± 0.31 V.P = 0.66) did not differ between groups A and B. However, in three, patients of group A, chronic atrial sensing threshold was ≤ 1 mV requiring atria) sensitivities of at least 0.35 mV to achieve reliable atrial sensing. Atrial lead placement during AF is feasible and reduces implantation time. However, bipolar atrial leads and the option to program high atrial sensitivities are required.
Prospective Postmarket Device Studies Versus Returned Product Analysis as a Predictor of System Survival
Authors: PRATT TIMOTHY R.H. , PULLING CHRISTOPHER C. , STANTON MARSHALL S.
Published: June 2006

Monitoring and reporting mechanisms are vital tools for clinicians to assess ICD system performance over time for optimal patient care. This article explores the various reporting mechanisms available to the clinician, both historical and current, and compares and contrasts two such methods. The lead survival rates obtained by return product analysis (RPA) are compared with those from an ongoing prospective chronic study that actively follows patients for clinical ICD system failures (Tachyarrhythmia Chronic Systems Study [TCSS]). Examination of available data shows that a prospective study such as the TCSS is capable of detecting clinically significant adverse events in 2.2% of the 3,958 leads followed. By comparison, RPA‐based monitoring of the same leads detects “out of specification” events in 0.5% of the 78,571 leads followed. Statistical analyses of two separate families of leads (HV leads and SQ Patch leads) show that survival rates obtained by the two methods begin to differ at approximately 2 years of implant experience, with 95% confidence intervals no longer overlapping at 3 years. The authors conclude that prospective chronic device studies are a superior tool for the ongoing monitoring of implanted device performance compared to RPA‐based reports.
Pitfalls of the Concept of Incremental Specificity Used in Comparisons of Dual Chamber VT/VF Detection Algorithms
Authors: MALIK MAREK
Published: June 2006

The concepts of incremental specificity and incremental positive predictive accuracy (PPA) have been proposed to measure the success of dual chamber cardioverter deftbrillator (ICD) algorithms for tachyarrhythmia detection in improving specificity while maintaining very high sensitivity to detection of episodes of ventricular tachycardia/fibrillation (VT/VF), While dual chamber VT/VF detection algorithms differ substantially among different ICD manufacturers, they all operate as “add‐on” features to the single chamber elementary detection algorithms that are based on simple criteria of increased ventricular rate. The incremental specificity and PPA characterize the performance of the dual chamber detection operation in this “add‐on” mode, that is within a database of rhythm episodes all meet the simple rate‐based criteria. A statistical model of hypothetical devices has been used to demonstrate that the concepts of incremental specificity and PPA are very dependent on the composition of the database used to evaluate a particular dual chamber ICD. Because some sinus tachycardia and su prove n‐tricular tachyarrhythmias with regular atrioventricular conduction are more easily discriminated from true VT/VF than other supraventricular tachyarrhythmias, the model shows that rather than the performance of the dual chamber detection functions, the major contributor to the incremental specificity may be the proportion between the “easy” and “difficult” supraventricular episodes. The algorithms used by different ICD manufacturers to detect tachyarrhythmias based on ventricular rate are known to differ substantially in the ability to differentiate true VT/VF from other tachyarrhythmias. Consequently, the databases of rhythms against which the different dual camber ICDs are tested are also different in composition of different types of supraventricular tachyarrhythmias. Therefore, the values of incremental specificity and PPA reported by different manufacturers do not have an equivalent meaning and do not offer a valid comparison of the true performance of different dual chamber ICDs.
Implantable Defibrillator Therapy in Naxos Disease
Authors: GATZOULIS KOSTAS , PROTONOTARIOS NIKOS , ANASTASAKIS ARIS , TSATSOPOULOU ADALENA , VLASSEROS JOHN , GIALAFOS JOHN , TOUTOUZAS PAVLOS
Published: June 2006

Naxos disease is a unique form of right ventricular cardiomyopathy with a high prevalence of malignant ventricular arrhythmias, including sudden cardiac death. As a hereditary systemic disease confined to a small island, it has been closely studied over the last 15 years. The implantation of an automatic defibrillator provides an alternative form of antiarrhythmic management to improve life expectancy in these high risk cardiac patients. We present the first two Naxos disease patients with malignant ventricular arrhythmias who had defibrillator implantation.
Automatic Pace‐Sense Polarity Switch as an Indicator of Early Lead Corrosion: The Usefulness of Impedance Trend Graphing
Authors: WILLIAMS DEBORAH
Published: June 2006

A rate responsive dual chamber pacemaker system (Medtronic Inc.) was implanted without complications. At 6‐week postimplantation a routine pacemaker check showed a spontaneous switch from programmed bipolar pace‐sense to unipolar pace‐sense on the atrial and ventricular leads. Pacing and sensing thresholds were not significantly changed from implantation. The atrial and ventricular lead impedances increased from 680 and 720 ohms at implantation to 1,290 and 2,400 ohms, respectively. The device was reprogrammed to bipolar pace‐sense and the continuous lead telemetry trend option was programmed On. Evaluation of the system 1 month later revealed a decrease in atrial and ventricular lead impedances, 680 and 2,100 ohms, without a change in pace‐sense polarity. One month later, the lead polarity had again switched from programmed bipolar to unipolar pacesense. The lead trend data revealed stable atrial impedances with sporadic increases in the ventricular lead impedance to values > 3,000 ohms. The pacemaker lead system was invasively investigated and visible gross corrosion of the ventricular lead distal connector pin was discovered.
Management of Atrial Arrhythmias Secondary to Severe Congenital Heart Disease with the Atrioverter
Authors: TIMMERMANS CARL , RODRIGUEZ LUZ‐MARIA , REUTER DAVID , STAFFERS JAN , BARENBRUG PAUL J.C. , CHERIEX EMILE C. , WELLENS HEIN J.J.
Published: June 2006

An atrial defibrillator was implanted in a patient with congcnitally corrected transposition of the great arteries, associated cardiac abnormalities, and persistent atrial arrhythmias. During a 15‐month follow‐up, 14 of 20 spontaneous episodes of his arrhythmias were successfully treated with the device. Two of these episodes were converted to sinus rhythm during ambulatory use of the device. Successful use of the device required implantation of a third defibrillation lead in the persistent leftsided superior caval vein and rigid control of congestive heart failure. An atrial defibrillator may be a valid treatment option in patients with congenital heart disease crippled by atrial fibrillation
Muscle Stimulation Related to a Nonfunctioning Epicardial Pacemaker Electrode
Authors: BOHM ÁDÁM , PINTÉR ARNOLD , HAJDÚ LÁSZLÓ , PRÉDA ISTVÁN
Published: June 2006

Noninfected retained pacemaker leads produce fewer complications than infected electrodes. Epicardial electrodes are rarely used, thus complications associated with such electrodes are seldom reported. We report a case with muscle stimulation due to a retained epicardial pacemaker electrode.
Influence of Propafenone on Resetting and Termination of Canine Atrial Flutter
Authors: MENSOUR BOUALEM , JALIL ELISE , VINET ALAIN , KUS TERESA
Published: June 2006

Previous studies on atrial flutter (AF) presumed that resetting was due to the prematurity effect (PE) in which the stimulated antegrade wavefront travels in the tail of the AF preexisting wavefront. We studied the collision effect (CE) between the AF and the stimulated retrograde wavefronts, its contribution to resetting, and its relationship to AF termination and how they are affected by the Class IC agent propafenone (PPF). A canine model of AF was created using a Y‐shaped lesion in the right atrium in 14 dogs (33 ± 3 kg). Five atrial bipolar electrodes were positioned around the tricuspid valve. In a subsequent set of 11 dogs, we used 16 bipolar electrodes for recording, AF was induced by burst pacing. Single and multiple stimuli were applied to measure conduction time and reset‐response curves (RRCs). This was repeated after the administration of PPF (1 mg/kg loading dose for 10 minutes, followed by 1.8 mg/kg/per hour infusion). Three distinct mechanisms were found to contribute to the RRC: the PE, the CE, and heterogeneity. PPF stabilized the RRC, increased significantly the cycle length (CL), the duration of the effective refractory period, as well as the duration of the excitable gap. However, PPF did not alter the duration of the fully excitable portion. We studied 36 annihilations without and 48 with PPF. Transient fibrillation was found in 75% of the episodes without, compared to 22% with PPF. Other types of termination such as conduction block, CL oscillations, and reversal of activation were found for 25% of the episodes without and 78% with PPF. In many cases, conduction block and CL oscillations were associated with a failure of propagation of the stimulated antegrade wavefront in the region of collision. Termination by reversal of activation suggests that propagation was two dimensional and could not be represented by a one dimensional movement. The average coupling interval (in percent of CL), that induced fibrillation was not significantly different from that at which conduction block occurred. This suggests that transient fibrillation is associated with a weak CE rather than with rapid pacing. The CE is amplified by multiple stimuli and PPF. The incidence of transient fibrillation in AF annihilation diminishes with PPF as the CE becomes more important. This suggests that the evaluation of PE and CE in AF may be an indication of the risk of atrial fibrillation.