bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of the Effectiveness of In‐Office and Transtelephonic Follow‐Up in Terms of Pacemaker System Complications
Authors: SWEESY MARK W. , ERICKSON STEVEN L. , CRAGO JUDY A. , CASTOR KAREN N. , BATEY ROBERT L. , FORNEY RICHARD C.
Published: July 2006

A study was undertaken to determine the most effective method of pacemaker follow‐up in terms of the total number of complications detected and yield per follow‐up in single and dual chamber pacing systems. The analysis involved 9,786 patient records from 635 patients. The records were reviewed with respect to method of follow‐up, number of chambers paced, and complications detected. Complications included: oversensing, undersensing, noncapture, pocket and diaphragmatic stimulation, pacemaker mediated tachycardia, crosstalk, pulse generator malfunction, lead malfunction, infection/erosion, premature end of service, exit block, and other miscellaneous problems. Eight thousand two hundred eighty‐eight of the 9,786 follow‐ups were performed in the office while 1,498 were transtelephonic. Single chamber pacing systems were implanted in 329 patients and 306 were dual chamber systems. A total of 599 complications were detected. Analysis yielded a per patient complication rate of 5.1 % (single chamber) and 8.4% (dual chamber) for in‐office follow‐up. This compared to a transtelephonic follow‐up per patient complication rate of only 0.3% (single chamber) and 1.0% (dual chamber). In‐office pacemaker follow‐up is significantly more effective (P < 0.001) than transtelephonic follow‐up in detecting both single and dual chamber pacemaker system complications.
Direct and Telemetered Lead Impedance
Authors: BEN‐ZUR URI M. , PLATT SIMIE B. , GROSS JAY N. , KIM JUNE S. , DeLEON JOSHUA , GUGUCHEV PAVEL , FURMAN SEYMOUR
Published: July 2006

Objectives: We undertook this study to determine whether telemetered lead impedance measurements (LIM) can be correlated with direct LIM and to determine the stability of LIM over time when measured directly and via telemetry. Methods: Direct LIM and telemetered LIM were measured in 91 patients; 101 leads during initial implantation and 40 leads during pulse generator replacement. Differences in direct LIM measured during initial implant and pulse generator replacement (direct‐direct) were compared in 41 patients (28 atrial leads and 37 ventricular leads). The stability of telemetered LIM obtained immediately postoperatively, at 1 month and 1 year, postimplantation was assessed in 50 patients (23 atrial and 49 ventricular leads). Results: In atrial leads acute direct LIM was 633.9 ± 18.4 Ω versus 575.8 ± 18.5 Ω for telemetered LIM (r = 0.58), and chronic direct LIM was 670.9 ± 49.3 Ω versus 607.0 ± 36.3 Ω for telemetered LIM (r = 0.87). In ventricular leads acute direct LIM was 747.3 ± 16.9 Ω and 684.7 ± 16.4 Ω for telemetered LIM (r = 0.69), and chronic direct LIM was 674.8 ± 29.9 Ω and 625.2 ± 28.5 Ω for telemetered LIM (r = 0.68). The mean direct–direct UM rose 124 Ω (P < 0.001) in atrial leads and 10 Ω (P = NS) in ventricular leads. Telemetered LIM for atrial leads was 581.0 ± 27.6 Ω immediately postimplantation compared to 625.7 ± 34.8 Ω at 1 month and 754.1 ± 43.0 Ω at 1 year. Telemetered LIM for ventricular leads was 661.3 ± 17.5 Ω at implant, 684.6 ± 20.7 Ω at 1 month and 724.7 ± 22.7 Ω at 1 year. Conclusions: There is a good but limited correlation between direct and telemetered LIM. Mean direct LIM obtained at initial implantation is similar to that measured at pulse generator replacement. The telemetered LIM is stable over the first month postimplantation but tends to rise during the first year of follow‐up and substantial changes in impedance are not uncommon in individuals with normal function. There is a tendency for LIM to rise with lead maturation. If telemetered LIM is to be followed over time, a baseline telemetered value should be obtained immediately postoperatively.
Comparison of Threshold Values Between Steroid and Nonsteroid Unipolar Memhrane Leads
Authors: SVENSSON OLOF , KARLSSON J.‐E. , BINNER L. , BROBE R. , HÖHLER H. , KREUZER J. , MALM D. , MATHEIS G. , PIETERSEN A. , SCHENKEL W. , VESTERLUND T.
Published: July 2006

The aim of this study was to evaluate whether steroid membrane leads can reduce pacing thesholds and thereby save energy as compared to nonsteroid membrane leads. The study was a random sample, double blind test consisting of 90 patients between 49–94 years of age admitted to seven hospitals in Europe for pacemaker implantation. The two leads compared in this study had contoured activated carbon tips covered with ion exchange membranes. The leads were identical except that 30 μg of dexa‐methasone was dissolved in the ion exchange membrane of one of the leads. Normal lead implant procedures were used. Follow‐up procedures were conducted at 2 weeks and 1,3,6, and 12 months after lead implantation. The pulse generator was programmed to an amplitude of 2.5 or 5 V and a duration of 0.5 msec. The stimulation threshold was measured using the VARIO function. The threshold was measured a total of three times in order to determine the presence of microdislocations. At the 2‐ and 4‐week follow‐ups, the stimulation threshold was significantly lower for the steroid leads than for the membrane leads without steroid (0.54 ± 0.19 vs 0.76 ± 0.25 V, P = 0.0005; and 0.59 ± 0.19 vs 0.74 ± 0.26 V, P = 0.005), but after 3 months, the threshold values were almost the same for both leads.
Five‐Years Experience with Intravascular Lead Extraction
Authors: SMITH HEIDI J. , FEARNOT NEAL E. , BYRD CHARLES L. , WILKOFF BRUCE L. , LOVE CHARLES J. , SELLERS T. DUNCAN ,   for the U.S. LEAD EXTRACTION DATABASE
Published: July 2006

From December 1988 to April 1994, the extraction of 2,195 intravascular pacing leads from 1.299 patients was attempted at 193 centers. Indications were: infection (54%, including 10% septicemia), pacemaker reoperation with removal of nonfunctional or incompatible leads (40%), and other causes (6%). Extraction was attempted via the implant vein using locking stylets and dilator sheaths, via the femoral vein using snares, retrieval baskets, and sheaths, or via both approaches. Leads had been implanted for 0.2 months to 24 years (mean 56 months). At the conclusion of the intravascular procedure, 86.8% of the leads were completely removed, 7.5% were partially removed, and 5.7% were not removed. For physicians performing their first case, 12% of leads were not removed; for physicians who had performed more than 10 cases, only 2% of leads were not removed. Of the 189 leads where extraction attempts had previously failed, 75.1% were completely removed, 14.8% were partially removed, and 10.1% were not removed. Scar tissue increased in severity with implant duration, was a complicating factor, and was the main cause of failure to remove leads. Use of the femoral approach increased with implant duration (5% of leads implanted 12 months or less, 11% of leads 13 months to 3 years, 20% of leads 4–7 years, and 31 % of leads 8–24 years), primarily because of increasingly abundant scarring and prior lead damage. Fatal and near fatal complications occurred in 2.5%. including 8 (0.6%) deaths (3 hemopericardium/tamponade, 1 hemothorax, 3 pulmonary embolus, 1 stroke). With experienced operators, appropriate precautions, and appropriate patient selection, modern techniques allow the successful extraction of up to nearly 98% of intravascular leads with a relatively low incidence of complications.
A Comparison of VVIR and DDDR Pacing Following Cardiac Transplantation
Authors: ROELKE MARC , McNAMARA DENNIS , OSSWALD STEFAN , SEMIGRAN MARC , DEC WILLIAM , HARTHORNE J. WARREN
Published: July 2006

We compared the clinical course of patients paced in VVIR versus DDDR mode to determine the most appropriate method of pacing following cardiac transplantation. Pacemaker implantation was required in 9 of 90 orthotopic cardiac transplants (10%). Indications included sinus bradycardia or sinus arrest (8 patients) and AV node dysfunction (1 patient). VVIR pacemakers were implanted in four patients and DDDR in five patients. DDDR patients: The mean P wave was 1.7 mV and the mean atrial stimulation threshold was 0.8 V (at 0.5 msec). During follow‐up of 20 months, two atrial lead complications developed (29% of leads in 33% of patients). No lead complications were directly related to endomyocardial biopsy. VVIR patients: All four patients developed VA conduction with mean VA time 180 msec (160–240 msec). Two patients developed pacemaker syndrome. Conclusions: VA conduction and pacemaker syndrome may develop in cardiac transplant recipients paced in the VVIR mode. Dual chamber pacing is technically feasible and preferable following cardiac transplantation.
Dissimilar Action of Two Cyclic Adenosine‐Monophosphate Analogues on the Sodium Current in Intact Rat Papillary Muscle
Authors: KIRSTEIN MICHAEL , LANGENFELD HEINER , KATZER ASTRID , KOCHSIEK KURT
Published: July 2006

In intact papillary muscles from rat we have found with the loose‐patch‐clamp technique an increase of the fast cardiac sodium current (INa+) by isoproterenol (ISO). In this study we have tested two membrane permeable analogues of the intracellular second messenger cyclic adenosine‐monophosphate (cAMP) to investigate the intracellular pathway: 8‐Br‐cAMP (50 μM) and the newer developed Sp5,6‐Dichloro‐1‐β‐D‐ribofuranosylbenzimidazole‐3′, 5′‐cyclic‐monophosphor‐othioate (5,6‐DCl‐cBiMPS, 20 μM). The availability of INa+ was determined with test pulses to ± 0 mV every 3.5 seconds after 2.5‐second conditioning between ‐130 mV and‐50 mV and a holding potential at the resting potential of the cell under examination, and after wash‐in of either compound. The peak currents were fit to a Boltzmann equation, and expressed by the maximal attainable current INa+Na,max the mid‐point potential V½, and a steepness parameter a. Values are given by mean ± SEM. 8‐Br‐cAMP showed a significant shift of the availability curve in the hyperpolarized direction (V½= ‐82 ± 2 mV vs ‐ 66 ± 2 mV, n = 5, P < 0.05) with only minor changes of I+No,max and a. In contrast, 5,6‐DCI‐cBiMPS had no significant effect on V½ but increased I+Na,max by 8%± 2% versus control (n = 5. P < 0.05). In an intact muscle preparation we have found that 5,6‐DCI‐cBiMPS has a similar effect as that observed with the β‐adrenergic agonist ISO (100 nM), whereas 8‐Br‐cAMP exhibited a dissimilar action. This indicates, that ihe effects of ISO are transmitted by the cAMP system. On the other hand, 8‐Br‐cAMP, which is not as permeable and specific an activator of the cAMP dependent proteinkinase, may have other effects on the sodium channel, perhaps mediated through purinergic receptors.
Dispersion of Ventricular Refractoriness in Experimental Myocardial Infarction: Effect of Sotalol
Authors: LUBIÑSKI ANDRZEJ , HINDRICKS GERHARD , SHENASA MOHAMMAD , HAVERKAMP WILHELM , VOGT BARBARA , BORGGREFE MARTIN , BREITHARDT GÜNTER
Published: July 2006

Dispersion of refractoriness may contribute to the propensity for reentrant arrhythmias. This study was performed to assess the effect of sotalol on the dispersion of refractoriness in experimental myocardial infarction. In 9 mongrel dogs, 14 days after induction of myocardial infarction by an occlusion reperfusion technique, programmed ventricular stimulation and epicardial mapping were performed before and during (3 mg/kg + 0.5 mg/kg per hour) sotalol administration. To assess the spatial distribution of refractoriness, ventricular fibrillation (VF) intervals were analyzed. The rationale for this method is that, during VF, when multiple reentrant wavelets are present, cells are excited as soon as they recover from previous activation. The coefficient of variation (standard deviation × 100) served as an index of spatial distribution of refractoriness. Results: VF was induced before sotalol in 7 dogs and in 5 of 7 during sotalol administration. The mean value of the index VF intervals decreased from 19.8 ± 2.3 at baseline to 15.8 ± 2.6 during sotalol (P = 0.011), indicating a more homogeneous distribution of refractoriness. Thus, the antiarrhythmic effects of sotalol may be mediated by its action on the dispersion of refractoriness.
Reversibility of Electrophysiological Abnormalities in Subacute Ischemia
Authors: HOFFMAN BRIAN F. , REN XIAO‐LI
Published: July 2006

Twenty‐four hours after occlusion of the left anterior descending coronary artery in the dog, ventricular tachycardia is the predominant rhythm. At this time, records of transmembrane potentials from the subendocardial Purkinje fibers adjacent to the infarct show a low maximum diastolic potential, prominent phase 4 depolarization, and slow response action potentials. Exposure of the fibers to pinacidil, 25–100 μM, increases resting potential to the estimated value of EK, abolishes the phase 4 depolarization, and restores action potential amplitude and Vmax toward normal. Perfusion of the bed of the occluded coronary artery with Tyrode's solution prior to isolation of the subendocardial tissues results in similar normalization of transmembrane potentials. These findings indicate: (a) that the major cause of the abnormal transmembrane potentials of the subendocardial tissues is the loss of resting potential; and (b) that abnormalities of the transmembrane potentials are caused by some substance that can be washed out by perfusion and not by a direct effect of ischemia.
Specificity of Retrograde Conduction in Screening for Atrioventricular Nodal Reentrant Tachycardia
Authors: GLOTZER TAYA , EVANS STEVEN , BERNSTEIN NEIL , CHINITZ LARRY
Published: July 2006

Baseline AV conduction properties (antegrade and retrograde) are often used to assess the presence of dual AV nodal physiology or concealed AV accessory pathways. Although retrograde conduction (RET) is assumed to be a prerequisite for AV nodal reentrant tachycardia (AVNRT), its prevalence during baseline measurements has not been evaluated. We reviewed all cases of AVNRT referred for radiofrequency ablation to determine the prevalence of RET at baseline evaluation and after isoproterenol infusion. Results: Seventy‐three patients with AVNRT underwent full electrophysiological evaluation. Sixty‐six patients had manifest RET and inducible AVNRT during baseline atrial and ventricular stimulation. Seven patients initially demonstrated complete RET block despite antegrade evidence of dual AV nodal physiology. In 3 of these 7 patients AVNRT was inducible at baseline despite the absence of RET. In the other four patients isoproterenol infusion was required for induction of AVNRT, however only 3 of these 4 patients developed RET. One of these remaining patients had persistent VA block after isoproterenol. Conclusions: The induction of AVNRT in the absence of RET suggests that this is not an obligatory feature of this arrhythmia. Therefore, baseline AV conduction properties are unreliable in assessing the presence of AVNRT and isoproterenol infusions should be used routinely to expose RET and reentrant tachycardia.
Maze 3 for Atrial Fibrillation: Two Cuts Too Few?
Authors: TSUI S.S.L. , GRACE A.A. , LUDMAN P.F. , SCHOFIELD P.M. , PAGE A.J.P. , ROWLAND E. , LARGE S.R.
Published: July 2006

The Maze procedure has been developed as a surgical approach to the management of patients with atrial fibrillation refractory to medical treatment. The recent modification of the technique (Maze 3) achieves good rate control with coordinated AV contractions. However, the procedure involves cuts that completely isolate a block of left atrial (LA) wall, including the four ostia of the pulmonary veins. The electrical and mechanical activity of this isolated LA block are dissociated from the rest of the atrium, and the area may, in fact, continue to fibrillate. This may provide a nidus for the development of mural thrombus. The weight and endocardial surface area of the LA block and of the entire LA were estimated in ten formalin fixed hearts from trauma victims with no evidence of cardiac disease. In these samples, the LA block represented 35% of the endocardial surface area of the entire LA and 29% of the weight. The LA block is of sufficient size to allow macroreentrant circuits to form and has the potential to fibrillate if isolated from the rest of the atrium. We modified the Maze 3 procedure to recruit the otherwise isolated LA block by using two additional cuts around each pair of pulmonary veins as they enter the LA. The first patient who underwent the modified procedure demonstrated sinus rhythm on Holter monitoring postoperatively and remained in sinus rhythm following burst atrial pacing at 300 and 420 beats/min each for 30 seconds. In addition, atrial contractions were found to contribute 19% of the cardiac output. The majority of the atrial wall and, in particular, the recruited area between the pulmonary veins contracted well, as demonstrated by transesophageal echocardiography. We suggest that this modification of Maze 3 has a potential advantage over the standard procedure by recruiting the entire LA without leaving any dyskinetic endocardial surface for thrombus formation. This should in turn reduce the risk of thromboembolic complications.
Surgery as an Effective Nonpharmacological Mode of Treatment of Atrial Fibrillation Resistant to Standard Therapy
Authors: SUWALSKI KAZIMIERZ , PYTKOWSKI MARIUSZ , ZELAZNY PIOTR , MAJSTRAK FRANCISZEK , KASZCZYNSKI TOMASZ , PASIERSKI TOMASZ , RZACZYNSKA MAGDALENA , WOJCIECHOWSKI DARIUSZ
Published: July 2006

There are two surgical methods for atrial fibrillation (AF) treatment: Maze and corridoring procedures. The first one prevents AF occurrence by performing multiple atriotomies. During the second procedure a corridor between a sino‐atrial and the AV node is created together with an electrical isolation of the atria. During 1992 and 1993 seven patients, aged 27–55, mean 43‐years‐old, with recurrent, resistant to standard therapy AF were referred for surgical treatment to our department. Additional diagnoses include: concealed WPW syndrome in 1 patient, atrial septal defect (ASD) in 3 patients, coronary artery disease in 1 patient. Maze procedure was performed solely in 1 patient, in another together with 2 accessory pathways ablation, in 3 patients with ASD closure and in 1 patient with 2 bypass grafts. In one patient corridoring procedure was performed. Normal sinus rhythm was restored in every patient from 7 to 26 days after the procedure, No surgical complications were noted during the postoperative period. Mechanical function of the atria was documented with echo Doppler 2–6 weeks after the operation. No evidence for AF recurrence was noted within 3–14 months (mean 5 months) of follow‐up. The preliminary results of Maze and corridoring procedures are encouraging.
Nonpharmacological Therapy of Ventricular Tachyarrhythmias: Observations in 554 Patients
Authors: TRAPPE HANS‐JOACHJM , PFITZNER PETRA , FIEGUTH HANS‐GERD , WENZLAFF PAUL , KIELBLOCK BIRGIT , KLEIN HELMUT
Published: July 2006

It has been shown that conventional antiarrhythmic drug treatment is debatable, and there is growing interest in nonpharmacological techniques. We studied the outcome of 554 patients with ventricular tachycardia (VT) or ventricular fibrillation (VF) who underwent nonpharmacological techniques from March 1980 to June 1994 at our institution. Catheter ablation was performed in 51 patients (G1), map guided surgery in 147 (G2), and cardioverter defibrillator implantation (ICD) in 356 (C3). During a mean follow‐up of 37 ± 12 (< 1–137) months, incidence of sudden death (G1 4%, G2 6%, C3 3%) and cardiac death (G1 7%, G2 16%, G3 8%) were relatively low, and there was no significant differences between G1‐G3. VT/VF recurrences occurred more frequently in G1 (57%) than in G2 (18%) (P < 0.01). ICD discharges occurred in 69% of patients. We conclude that nonpharmacological techniques lead to low sudden death rates; however, there is a high rate of recurrence in G1. Risk stratification is necessary to select the ideal therapy for each individual patient.
Relationship Between Short‐ and Long‐Term Measurements of Heart Rate Variahility in Patients at Risk of Sudden Cardiac Death
Authors: FEI LÜ , STATTERS DEBORAH J. , ANDERSON MARK H. , MALIK MAREK , CAMM A. JOHN
Published: July 2006

Because of technical difficulties in analyzing heart rate variability (HRV) from ambulatory Holter recordings over 24‐hour periods, short‐term recordings are more practical for the clinical application of HRV. However, the relationship between short‐ and long‐term recordings is unclear. In this study, short‐term (10 min) electrocardiograms were assessed in the supine position, during passive head‐up tilt and on standing in 15 patients (aged 39 ± 14 years) with ventricular tachycardia/fibrillation not associated with coronary artery disease. Spectral HBV was computed as total frequency (TF: 0.01–1.00 Hz), low frequency (LF: 0.04–0.15 Hz), and high frequency (HF: 0.15–0.40 Hz) components. The short‐term HRV parameters were compared with those obtained from long‐term (24 hour) recordings from the same patients. There was a significant decrease in the HF component of HRV and a significant increase in LF/HF ratio during passive tilt or active standing compared with supine recordings, but no significant changes were observed in the TF or LF components. All frequency components of HRV for the 24‐hour periods showed significant correlation with the values from short‐term recordings (τ ranged from 0.67–0.87). Stepwise multivariate regression analysis showed that both the TF and HF components of HRV over 24 hours were predominantly related to the corresponding frequency components of HBV in the supine position, while the LF component of HRV over 24 hours was predominantly related to that on standing. Our observations suggest that the short‐term HRV is related to the long‐term value, but global HRV over 24 hours cannot completely be replaced by the short‐term recordings. The postural effects on the frequency components of HRV should be taken into account when short‐term HRV assessment is applied.
Arrhythmias in Centenarians
Authors: WAKIDA YASUSHI , OKAMOTO YASUYOSHI , IWA TORU , YONEMOTO TAKAYUKI , KANEMAKI KENGO , SHIOMI TOSHIAKI , MIZUTANI KOYA , KOBAYASHI TADASHI
Published: July 2006

Background: Many studies have shown an increase in the prevalence of arrhythmias with advancing age. However, little is known about arrhythmias in centenarians. Method and Results: Thirty‐two Japanese centenarians aged 100–106 years (14 males, 18 females) were studied. All of them had 12‐lead EGGs, and 22 also had 24‐hour ambulatory monitoring. As controls, 89 healthy Japanese elderly from the same geographic area underwent 12‐lead ECG. Their mean age was 75 ± 6 years with a range of 63–93 years, and there were 28 males and 61 females. Twenty‐three of them also had Holter ECGs. On the 12‐lead ECG, the heart rate was slightly, but significantly, higher in the centenarians (76.8 ± 12.7 beats/min) than that in the elderly subjects (74.9 ± 5.9 beats/min, P < 0.005). PQ and QTC were significantly longer in the centenarians (174 ± 29 and 439 ± 33 msec, respectively) compared with the elderly subjects (158 ± 23 and 417 ± 31 msec, P < 0.005 and P < 0.001, respectively). Supraventricular premature beats (SVPBs) were observed in 31% of the centenarians and in 4% of the elderly subjects (P < 0.001). First‐ and second‐degree AV block was recorded in 25% of the centenarians and 1% of the elderly subjects (P < 0.001). Right bundle branch block was found in 19% of the centenarians and 7% of the elderly subjects (P < 0.05). There were no differences in the frequency of ventricular premature beats (VPBs) or QRS voltage. On the Holter ECG, there were no significant differences in average heart rate, maximum heart rate, minimum heart rate, or the longest RR interval. A subgroup of centenarians had frequent SVPBs. However, none of them had > 1,000 VPBs/day as opposed to four elderly subjects (P < 0.01). Atrial fibrillation was not observed in any records of the centenarians despite the presence of frequent SVPBs. Conclusion: These data suggest that conduction disturbances of the AV nodal—His‐Purkinje system and frequent SVPBs are common in centenarians, whereas very frequent VPBs and atrial fibrillation seem less common.
Causes of Death in Patients with Unipolar Single Chamber Ventricular Pacing: Prevalence and Circumstances in Dependence on Arrhythmias Leading to Pacemaker Implantation
Authors: MATTIOLI ANNA VITTORIA , ROSSI ROSARIO , ANNICCHIARICO ELIGIO , MATTIOLI GIORGIO
Published: July 2006

Cardiac pacing improves the prognosis of patients with severe impulse formation and conduction disturbance, though sudden death can occur frequently in paced patients. In the present study, we analyzed the causes and the circumstances of 378 deaths in 2,243 paced patients followed over a 5‐year period. Sudden cardiac death occurred in 71 of these 378 patients (18.7%), 56 patients died of stroke (15%), heart failure was the cause of death in 91 subjects (24%). We analyzed the causes of death in two groups with respect to the arrhythmia that had led to pacemaker implantation. The prevalence of cardiac sudden death was higher in patients with AV block than in patients with sick sinus syndrome, while stroke was more frequent in patients with sick sinus syndrome, particularly those with both fast and slow components. Atrial fibrillation is common in patients with sick sinus syndrome and is an important well‐known risk factor for stroke. Death from heart failure was frequently reported in our population, but in our study group only a few patients had heart failure at the moment of pacemaker implantation. We conclude that sudden death is a common event in paced patients and the disturbance that led the patient to pacemaker implantation was also a factor in the cause of death.
A Direct Midseptal Approach to Slow Atrioventricular Nodal Pathway Ablation
Authors: EPSTEIN LAURENCE M. , LESH MICHAEL D. , GRIFFIN JERRY C. , LEE RANDELL J. , SCHEINMAN MELVIN M.
Published: July 2006

Objectives: The purpose of this study was to describe a midseptal approach to selective slow pathway ablation for the treatment of AV nodal reentrant tachycardia (AVNRT). In addition, predictors of success and recurrence were evaluated. Methods: Selective ablation of the slow AV nodal pathway utilizing radiofrequency (RF) energy and a midseptal approach was attempted in 60 consecutive patients with inducible AVNRT. Results: Successful slow pathway ablation or modification was achieved in 59 of 60 patients (98%) during a single procedure. One patient developed inadvertent complete AV block (1.6%). A mean of 2,7 ±1.4 RF applications were required with mean total procedure, ablation, and fluoroscopic times of 191± 6.3, 22.8 ± 2.3, and 28.2 ±1.8 minutes, respectively. The PR and AH intervals, as well as the antegrade and retrograde AV node block cycle length, were unchanged. However, the fast pathway effective refractory period was significantly shortened following ablation (354± 13 msec vs 298 ± 12 msec; P= 0.008). The A/V ratio at successful ablation sites were no different than those at unsuccessful sites (0.22 ± 0.04 vs 0.23± 0.03). Junctional tachycardia was observed during all successful and 60 of 122 (49%) unsuccessful RF applications (P < 0.0001). A residual AV nodal reentrant echo was present in 15 of 59 (25%) patients, During a mean follow‐up of 20.1± 0.6 months (11.5–28 months) there were four recurrences (5%), 4 of 15 (27%) in patients with and none of 44 patients without residual slow pathway conduction (P = 0.002). Conclusions: A direct midseptal approach to selective ablation of the slow pathway is a safe, efficacious, and efficient technique. Junctional tachycardia during RF energy application was a highly sensitive but not specific predictor of success and residual slow pathway conduction was associated with a high rate of recurrence.
Transient Loss of Sensing and Capture During Coronary Angiography in Two Patients with Permanent Pacemakers
Authors: PERRY GERSHON Y. , PARSONNET VICTOR , WERRES ROLAND , FLOWERS NANCY C.
Published: July 2006

Two cases of transient pacemaker failure to sense and capture during angiography are reported. This phenomenon is due to a transient increase in sensing and pacing thresholds beyond the pacemakers programmed settings. The underlying mechanism may be related to blood displacement, the electrochemical properties of the injectate, the high concentration of the contrast media, or a combination of these properties. Even though the chambers in which sensing and pacing loss occurred differed (ventricle in the first and atria in the second), the episode occurred repeatedly after injection of contrast media into the artery supplying the respective electrode‐tissue interface. In pacemaker dependent patients, provisions for external pacing should be implemented prior to injection of contrast into the coronary arteries.
Defibrillator Implantation in a Patient with a Persistent Left Superior Vena Cava
Authors: MATTKE SÖREN , MARKEWITZ ANDREAS , DORWARTH UWE , HOFFMANN ELLEN , STEINBECK GERHARD
Published: July 2006

The implantation of a transvenous cardioverter defibrillator (PCD 7217B) was performed in a patient with a persistent left superior vena cava. The defibrillation electrodes were positioned in the right ventricle and the superior vena cava via the right subclavian vein. A subcutaneous patch had to be implanted at the left lateral chest wall to achieve sufficient defibrillation thresholds. Three weeks later the system had to be removed because of a generator pocket infection. During the second implantation we placed one electrode in the persistent left superior vena cava perpendicular to the electrode in the right ventricle. Using this configuration transvenous defibrillation was possible without an additional subcutaneous patch.
Management of Electrical Instability After ICD Implantation
Authors: DIJKMAN BARBARA , DEN BULK KAREL , WELLENS HEIN J.J.
Published: July 2006

Postoperative ventricular arrhythmias were studied in 52 patients receiving implantable cardioverter defibrillators (ICDs). A group of 9 patients was identified who experienced electrical instability (El). The lead approach was thoracotomy in 6 and nonthoracotomy in 3 patients. In 8 of 9 patients VTs started soon after surgery. There was no evidence of ischemia, cardiac failure, electrolyte imbalance, or drug intoxication. The severity of ventricular arrhythmias varied from a considerable increase in incidence of well‐tolerated VTs in 3 patients (1 incessant) to poorly tolerated frequent VTs in 6 patients (2 incessant). In 4 patients VTs led to cardiac failure. Ventricular arrhythmias during El were refractory to antiarrhythmic drugs (AAD) in 7 of 9 patients. In 3 patients VTs accelerated into fast VT or VF with antitachycardia pacing (ATP) or cardioversion. The successful management of El was: sedation in 4 patients (3 with midazolam 1 with temazepam), ATP and AAD in 2 patients, AAD and hemodynamic support in 2 patients, spontaneous resolution in 1 patient. All patients survived the period of postoperative EL Two patients had a relapse of El at 2‐ and 9‐months postimplantation, respectively, one of whom eventually died.Conclusions: El occurred in 17% of patients after ICD implantation, had a varying degree of severity and required an individualized approach. Control of El with AAD was successful in only 2 of 9 patients. Sedation with midazolam was useful in the management of EL (PACE 1995; 18[Pt. II]:148–151)
Low Voltage Shocks Have a Significantly Higher Tilt of the Internal Electric Field Than Do High Voltage Shocks
Authors: BREWER JAMES E. , TVEDT MICHAEL A. , ADAMS TED P. , KROLL MARK W.
Published: July 2006

Typically, an implantable cardioverter defibrillator(ICD) uses a cardioversion shock that is a lower voltage pulse of the same morphology and tilt as its defibrillation pulse. We investigated the internal electric field resulting from an ICD low voltage shock to determine whether its field characteristics matched those of the internal electric field of a high voltage shock. We attached epicardial patch electrodes, for shock delivery, to five fresh pig hearts placed in a diluted, heparinized saline bath. We inserted two plunge electrodes into the myocardium to measure an internal voltage proportional to the electric field. Monophasic 20‐msec shocks, from a 140 μF capacitor, ranging from 0.1–30 joules, were delivered through the patches. We measured the current, external voltage, and internal voltage every 0.1 msec throughout the duration of a shock. For each shock, we calculated the time point that represented the 65% tilt position as measured across the patch electrodes. At this 65% tilt time position, we measured the pulse widths and calculated the internal tilt from the internal voltage. We found that the initial internal voltage for the 30‐joule shock was 173 ± 40 volts compared to 10 ± 2 volts for the 0.1‐joule shock. Similarly, we found that the final internal voltage for the 30‐joule shock was 56 ± 14 volts compared to 2 ± 1 volts for the 0.1‐joule shock. Thus, the internal tilt for the 30‐joule shock was 68 ± 1% versus 82 ± 3% for the 0.1‐joule shock (P < 0.05). Hence, a defibrillation shock (30 J) has an internal tilt close to its external tilt. A cardioversion shock (0.1 J), on the other hand, has a significantly higher internal tilt. The higher internal tilt of low strength, tilt‐based shocks should be investigated as a possible factor in the proarrhythmia of cardioversion therapy.
Electrode Surface Area Is An Important Variable for Defibrillation
Authors: SINGER IGOR , GOLDSMITH JANE , MALDONADO CLAUDIO
Published: July 2006

Previous studies have established efficacy of transseptal defibrillation. The purpose of the present study was to evaluate the role of transvenous electrode surface area for defibrillation. Sixteen dogs were randomized to 8 French and 5 French EnGuard™ electrodes; 8 dogs in each group. The length of the defibrillation coils was identical for both, but the surface area was different due to differences in the electrode diameters. Defibrillation threshold (DFT) testing was performed using a biphasic shock waveform, 6 msec+/2 msec‐. Logistic regression analysis was used to determine if the probability of defibrillation adjusted for voltage, current, and energy was different for 8 French electrodes. Logistic regression analysis found significant differences between 8 French and 5 French electrodes, with less voltage (P < 0.005), current (P < 0.03), and energy (P < 0.001) required at any level of probability to defibrillate for 8 French electrodes. These results support the conclusion that the surface area for endocardial electrodes is a significant factor for defibrillation. Therefore, when designing endocardial electrodes a desirable objective of reducing the electrode size should be weighed against the need to minimize DFTs.
Frequency Analysis of the P Wave: Comparative Techniques
Authors: STAFFORD PETER , DENBIGH PHILIP , VINCENT RICHARD
Published: July 2006

Frequency domain analysis of the signal‐averaged P wave (SAPW) may provide additional information over time domain analysis in patients with paroxysmal atrial fibrillation (PAF), but an optimum method has not yet been defined. We compared two different approaches using SAPW and test signals. We analyzed the frequency spectrum of the entire P wave (method A) or of only its terminal 100 msec (method B) using SAPW from 24 patients with idiopathic PAF and 34 normal controls. Absolute powers in frequency bands above 20, 30, 40, 60, and 80Hz (P20, P30, P40, P60, and P80) and power ratios about these frequencies (PR20, PR30, PR40, PR60, and PR80) were calculated. Patients had greater P30, P60, and P80 using method A (P30: 28.6 [± 2.2] vs 22.8 [± 1.6] μV2.s; P = 0.04; P60: 4.7 [± 0.5] vs 3.4 [± 0.3] μV2.s; P = 0.03; P80:1.9 [± 0.2] vs 1.3 [± 0.09] μV2.s; P = 0.01) but differences were smaller with method B. Moving the P wave endpoint 10 msec into the P wave had no effect on frequency domain parameters using method A but produced important changes using method B. Both methods were also applied to test signals of different durations but equal powers and power ratios. Method A gave predicted values for power and PR40 at all signal durations, but method B produced variable results. Frequency domain analysis of the SAPW shows significant increases in P wave energy in patients with PAF compared to controls. Analysis of the entire P wave is influenced less by signal duration and variations of the P wave endpoint than analysis of the terminal P wave alone and may define patient and control populations more precisely.
Inhibition of Atrial Electrical Activity by Ventricular Pacing Mediated by Vagal Stimulation
Authors: BATCHVAROV VELISLAV , BALABANSKI TOSHO , VELICHKOV PANKO , DASKALOV TIHOMIR , KATOVA TZVETANKA
Published: July 2006

In the absence of retrograde (VA) conduction, ventricular pacing does not exert any appreciable effect upon atrial electrical activity. We report three patients (2 with complete AV block and 1 with preserved AV conduction) in which, during EP study, no VA conduction was present and, in spite of that, excessive suppression (for more than 15 secs in the first patient) of sinus (atrial) electrical activity during RV pacing was observed. The sinus node suppression was reproducible in two patients. In all patients the suppression phenomenon was not observed after intravenous administration of atropine, which suggests that it was mediated by enhanced vagal tone.
Adenosine‐Sensitive Atrial Tachycardia
Authors: KALL JOHN G. , KOPP DOUGLAS , OLSHANSKY BRIAN , KINDER CHARLES , O'CONNOR MARK , CADMAN CHRISTOPHER S. , WILBER DAVID
Published: July 2006

Limited data suggest that adenosine termination of atrial tachycardia is uncommon. To investigate further the effect of adenosine on atrial tachycardia, adenosine (6–12 mg) was administered during sustained atrial tachycardia in 17 patients. All patients underwent electrophysiological study to exclude other mechanisms of supraventricular tachycardia. Mean patient age was 51 ± 20 years (range 18–82 years). Seven patients had no structural heart disease. The mean atrial tachycardia cycle length was 390 ± 80 msecs (range 260–580). Sustained atrial tachycardia was induced with atrial extrastimuli in 8 patients, and was either incessant at baseline or developed spontaneously during isoproterenol infusion in 9 patients. Adenosine terminated atrial tachycardia in 3 patients (18%), transiently suppressed atrial tachycardia in 4 patients (23%), and produced AV block without affecting tachycardia cycle length in the remaining 10 patients. Adenosine sensitivity was observed in 3 of 8 patients with tachycardias initiated and terminated by atrial extrastimuli, and in 4 of 9 patients with spontaneous, but not inducible tachycardias including 3 of 4 patients with isoproterenol facilitated tachycardias. Of multiple clinical and electrophysiological variables examined as potential predictors of adenosine sensitivity, only isoproterenol facilitation of spontaneous or inducible sustained tachycardia predicted adenosine sensitivity (P = 0.02). These observations suggest that adenosine‐sensitive atrial tachycardia may be more common than previously recognized. Adenosine sensitivity does not appear to be specific for tachycardia mechanism and cannot be predicted by response to pacing. Atrial tachycardias dependent on β‐adrenergic stimulation are most likely to be terminated by adenosine.
P Wave Oversensing in a Unipolar VVI Pacemaker
Authors: van GELDER BERRY M. , BRACKE FRANK A.L.E. , El GAMAL MAMDOUH I.H.
Published: July 2006

A 45‐year‐old male had a WI pacemaker implanted 20 years ago because of complete heart block. Because of perforation of the lead the pulse generator was removed after 4 weeks and a second lead was implanted from the contralateral side. Recently, the patient presented with symptoms of lightheadedness and syncope associated with prolonged pauses in the electrocardiogram. From the ECG, the ECG interpretation channel, and intracardiac electrogram telemetry, it was concluded that the VVI pacemaker was inhibited by P waves. The most likely explanation for this phenomenon was an insulation defect in the functioning lead caused by friction with the abandoned lead at the level of the high right atrium.
Atrial Fibrillation After Implantable Cardioverter Defibrillator Implantation
Authors: KELLY PATRICIA A. , MANN DAVID E. , REITER MICHAEL J. , HARKEN ALDEN H.
Published: July 2006

Atrial fibrillation is a reported complication of automatic defibrillator implantation. Its incidence, risk factors, time‐course, and complications have not been well‐defined. Accordingly, data from 117 patients who underwent defibrillator implantation via a thoracotomy (n = 71) or nonthoracotomy (n = 46) approach were reviewed. To identify risk factors, 15 variables of potential predictive value were chosen and analyzed. Atrial fibrillation developed in 26/117 patients (22%) during the early postoperative period and all but one of these 26 patients had undergone thoracotomy (P < 0.001). Patients who developed atrial fibrillation tended to be older than those who did not (63 ± 2 vs 58 ± 2 years, P = 0.04) and more frequently had a prior history of paroxysmal atrial fibrillation (31 % vs 10%, P = 0.02). They were also less likely to be taking Class I or III antiarrhythmic drugs (1/26 vs 24/91, P = 0.01). By multivariate analysis, operative approach (P < 0.001), the absence of antiarrhythmic drug therapy (P = 0.006), and a prior history of atrial fibrillation (P = 0.003) were significant independent variables. Digoxin neither prevented the occurrence of atrial fibrillation nor slowed the maximal ventricular response. The mortality and complication rates did not differ between the two groups. The major adverse effect of postimplant atrial fibrillation was automatic defibrillator discharge; six patients received between 1 and 11 discharges for atrial fibrillation with rapid ventricular rates.
Pure Atrial‐Based Lower Rate Timing of Dual Chamber Pacemakers: Implications for Upper Rate Limitation
Authors: BAROLD S. SERGE , FREDMAN CAREY S.
Published: July 2006

The release of dual chamber pulse generators with atrial‐based lower rate timing has added a new dimension to the complexity of pacemaker function and electrocardiography. This discussion focuses on the concept that in pulse generators with pure atrial‐based lower rate timing, preservation of the atrial lower rate interval takes hierarchial precedence over all other timing intervals including the ventricular‐based upper rate interval. Under certain circumstances whenever upper rate limitation requires extension of the programmed AV interval, a DDD pulse generator with pure atrialbased lower rate timing can violate its atrial‐driven upper rate interval to provide constancy of the lower rate interval. Such behavior also has important implications for upper rate control in devices that function in the DDI(DDIR) or DDDR mode with pure atrial‐based lower rate timing.
The Effects of Radiofrequency Ablation Versus Medical Therapy on the Quality‐of‐Life and Exercise Capacity in Patients with Accessory Pathway‐Mediated Supraventricular Tachycardia: A Treatment Comparison Study
Authors: LAU CHU‐PAK , TAI YAU‐TING , LEE PETER W.H.
Published: July 2006

This study aims to evaluate the impact of transcatheter radiofrequency ablation on quality‐of‐life (QOL) and exercise capacity in patients with paroxysmal Supraventricular tachycardia (SVT) on stable medical therapy and the extent of symptomatic benefits of this treatment in patients with SVT of different clinical severity. A total of 55 patients with SVT on stable medications for 3 months were randomly selected for either radiofrequency ablation treatment (46 patients) or continuation of medical therapy (medical control group, 9 patients). Severity of SVT was classified based on the frequency and duration of SVT episodes, hemodynamic disturbance, and the presence of preexcited atrial fibrillation during an episode. Treadmill exercise capacity (Bruce protocol) and QOL (questionnaire study and interview) were assessed before and at 3‐month intervals for 1 year after the radiofrequency procedure and at 3 months in the medical control group. Thirty‐six of 46 patients were successfully ablated in one session, and a QOL measure before and at 3 months after ablation in these patients showed an improvement in total scores for “General Health Questionnaire” (20.3 ± 6.2 vs 16.9 ± 5.3, P < 0.01), “Somatic Symptoms Inventory” (73. 0 ± 6.0 vs 76.1 ± 4.1, P < 0.02), and “Sickness Impact Profile” (12.6 ±1.7 vs 4.9 ± 3.9, P < 0.01). This improvement in QOL was progressive and sustained over a 1‐year period. Major arrhythmia limitations, such as apprehension of strenuous activities and long distance travel, were alleviated after a successful procedure. The extent of improvement in QOL was significant for patients considered to have “mild” or “severe” arrhythmia. Maximum exercise capacity during treadmill exercise increased from 13.1 ± 5.5 to l4.9 ± 4.5 minutes at 3 months after successful ablation (P < 0.002), which was mainly due to suppression of exercise induced SVT. There was no change in QOL or exercise capacity in the medical control group and in patients with an initially unsuccessful radiofrequency ablation. Thus, transcatheter radiofrequency ablation is superior to medical therapy in improving QOL and exercise capacity of patients with SVT of different clinical severity.
Correlation Among Fibrillation, Defibrillation, and Cardiac Pacing
Authors: IDEKER RAYMOND E. , ZHOU XIAOHONG , KNISLEY STEPHEN B.
Published: July 2006

An electrical stimulus must create an electric field of approximately 1 V/cm in the extracellular space to stimulate myocardium during diastole. To initiate fibrillation by premature stimulation during the vulnerable period or to defibrillate, an extracellular electric field of approximately 6 V/cm is required, a value approximately six times greater than that necessary for diastolic pacing. Yet, the current strength of the pulse given to the stimulating electrode to initiate fibrillation or to defibrillate is much greater than six times the diastolic pacing threshold. The ventricular fibrillation threshold is typically 40 times greater than the diastolic pacing threshold expressed in terms of current. The defibrillation threshold in terms of current is typically thousands of times greater than the diastolic pacing threshold. The reason that these thresholds vary so much more in terms of stimulus current than in terms of extracellular potential gradient is that each of the three thresholds requires creation of the required potential gradient at different distances from the stimulating electrode. Pacing requires a potential gradient of approximately 1 V/cm only in a small liminal volume of tissue immediately adjacent to the electrode. Initiation of ventricular fibrillation by premature stimulation during the vulnerable period requires a potential gradient of approximately 6 V/cm about 1 cm away from the stimulating electrode to allow sufficient space for the central common pathway of a figure‐eight reentrant circuit to form. Since the potential gradient falls off rapidly with distance from the stimulating electrode, a stimulating current about 40 times greater than the diastolic pacing threshold is required to generate an electric field of 6 V/cm approximately 1 cm away from the stimulating electrode. Defibrillation requires an electric field of approximately 6 V/cm throughout all or almost all of the ventricular myocardium. Since some portions of the ventricles can be more than 10cm away from the defibrillation electrodes, a shock of several amps is required to create this field, a current thousands of times greater than the pacing threshold.