bluuebunny/crossref_metadata_2025 huggingface dataset:
RR Variability and Baroreflex Sensitivity in Patients with Ventricular Tachycardia Associated with Normal Heart and Patients with Ischemic Heart Disease
Authors: GILL JASWINDER S. , FARRELL THOMAS , BASZKO A. , WARD DAVID E. , CAMM A. JOHN
Published: July 2006

Recent studies have suggested that disordered autonomic function, particularly the loss of protective vagal reflexes are associated with an increased incidence of arrhythmic deaths following myocardial infarction (MI). Heart rate variability (HRV) and baroreflex sensitivity (BRS) are measures of myocardial autonomic function and predict arrhythmic deaths post‐Mi. Patients with ventricular tachycardia associated with a “normal heart” frequently have exercise‐induced arrhythmia suggesting that the autonomic nervous system is important in the genesis of this form of ventricular tachycardia (VT). This study examines HRV and BRS in patients with VT associated with a “normal heart” and compares these values to patients post‐Mi with and without evidence of arrhythmia. Twenty patients with VT associated with a “normal heart,” 16 patients with MI but without arrhythmia on follow‐up, and 11 patients with MI and VT on follow‐up were studied. HRV was measured from 24‐hour Holter recordings and BRS was measured from plots of change in systolic blood pressure versus change in heart rate following an intravenous injection of 0.4–0.6 mg phenylephrine. HRV was significantly higher in the patients with VT associated with a normal heart (34.2 ± 10.8 msec) compared to the patients post‐Mi, without (23.7 ± 6.7 msec) and with (14.8 ± 3.8 msec) arrhythmia (F = 9.2, P < 0.001) and these differences were unaffected by adjustment for age. Baroreflex sensitivity was also higher in patients with VT associated with a “normal heart” (10.1 ± 6.8 msec/mmHg) compared to patients post‐Mi, without (6.1 ± 3.2 msec/mmHg) and with 3.2 ± 3.1 msec/mmHg) arrhythmia, (F = 7.2, P < 0.02), though statistical significance was lost after adjustment for age (F = 1.2, P = 0.3). We conclude that patients with VT associated with “normal hearts” have HRV and BRS that is higher than in patients post‐MI. Alterations of autonomic tone are, therefore, unlikely to be important in VT associated with a “normal heart,” whereas these appear to be important in patients with arrhythmic events post‐MI.
Factors Associated with Recurrence of Accessory Pathway Conduction After Radiofrequency Catheter Ablation
Authors: TWIDALE NICHOLAS , WANG XUNZHANG , BECKMAN KAREN J. , MCLELLAND JAMES H. , MOULTON KRIEGH P. , PRIOR MICHAEL I. , HAZLITT H. ANDREW , LAZZARA RALPH , JACKMAN WARREN M.
Published: July 2006

Catheter ablation of 215 accessory pathways (APs) using radiofrequency current (RF) was attempted in 204 consecutive patients. Two hundred twelve of the 215 (99%) APs were successfully ablated. After a minimum follow‐up period of 1 month (mean 8.5 ± 5.4 months), AP conduction had returned in 17 patients (8%). Recurrence of AP conduction was manifest by atrioventricular (AV) reentrant tachycardia in six patients, palpitations suggestive of AV reentrant tachycardia in five patients, ventricular preexcitation on electrocardiogram in five patients, and inducible AV reentrant tachycardia during a follow‐up electrophysiological study in one asymptomatic patient. AP conduction returned as early as 12 hours and as late as 4.7 months, but was evident within 2 months of ablution in 15 of 17 (88%) patients. AP conduction recurred in 12%‐14% of anteroseptal, right free‐wall, and posteroseptal APs, but only 5% of left free‐wall APs (P < 0.01). Retrograde only conducting APs (concealed APs) had recurrence of AP conduction more frequently (16%) than APs that exhibited antegrade conduction (5.5%; P < 0.01). Failure to record AP potentials from the ablation electrode, reflecting poor AP localization, was a strong predictor for recurrence of AP conduction. AP conduction returned in 19% of 48 APs when AP potentials were not recorded, compared to 5% of 164 APs where AP potentials were recorded from the ablation electrode (P < 0.01). The time to block of AP conduction from the onset of RF current application was longer in APs with recurrence of conduction (4.9 ± 6.1 sec vs 2.9 ± 3.4 sec; P < 0.02). Recurrence of AP conduction was more frequent when the stability of the ablation electrode was poor (12% of 41 APs vs 7% of 171 APs with stable electrode placement], and when the AP had multiple components (11% of 36 APs ablated at multiple sites vs 7% of 176 APs where AP was ablated at a single site), but these were not statistically significant. All 17 patients with recurrence of AP conduction underwent a second successful ablation. In conclusion, the overall incidence of recurrence of AP conduction is low, but is higher for right free‐wall and septal APs, concealed APs, and probably relates to poor AP localization.
The Effect of Age on the Electrophysiological and Autonomic Correlates of Sudden Death After Acute Myocardial Infarction
Authors: ODEMUYIWA OLUSOLA , FARRELL TOM , MALIK MAREK , BASHIR YAVER , POLONIECKI JAN , WARD DAVID E. , CAMM A. JOHN
Published: July 2006

To examine the influence of age on the autonomic and electrophysiological correlates of sudden death after myocardial infarction, 223 patients aged <60 and 195 patients aged ≥60 were followed up for a mean of 790 days. The patients had Holter monitoring and a signal‐averaged EGG 5–11 days after infarction. A mean ventricular ectopic beat frequency >10 beats/ hour (VE10) was present in 17.0% of young versus 28.2% of old patients (P < 0.01); a low heart heart variability index in 17.9% of young but in 32.3% of old patients (P < 0.001) and late potentials in 17.5% but 32% of young and old patients, respectively (P < 0.01). There was no difference in the incidence of sudden death between young and old patients (3.6% vs 3.1%). However, sudden death accounted for 50%, compared with 24% of all deaths in the young and old groups, respectively (P < 0.01). Sudden death was more closely associated with low heart rate variability and VE10 in the young than in the older group. The predictive values of a heart rate variability index <20 units with VE10 in younger patients were a sensitivity of 50%, a positive predictive accuracy (PPA) of 33% and risk ratio (RR) of 18 (P < 0.001); these values did not reach significance in older patients (16.7%, 4.3% and 1.4%, respectively.) Late potentials had a sensitivity of 50%, a PPA of 12.1%, and an RR of 4.7 in young patients (P < 0.05): the corresponding values in the older group were 80%, 8.9, and 8.4 (P < 0.02). It is concluded that sudden death is a more predominant mode of death and is more strongly associated with lower heart rate variability and with the VE10 incidence in young than in older postinfarction patients. Age should be taken into account when assessing the risk of sudden death after myocardial infarction.
Failure of Rate Responsive Ventricular Pacing to Improve Physiological Performance in the Univentricular Heart
Authors: KARPAWICH PETER P. , PARIDON STEPHEN M. , PINSKY WILLIAM W.
Published: July 2006

The physiological efficacy of single chamber, rate responsive ventricular pacing (VVIR) is unknown for symptomatic patients following the Fontan procedure for univentricular hearts. A total of six postoperative children, ages 6–21 years (mean 13), with symptomatic bradycardia requiring pacing therapy, underwent comparative treadmill exercise testing in randomized fixed rate (VVI) and VVIR pacing modes. In all instances, implanted activity pulse generators (Medtronic Model 8403) were programmed to identical age‐appropriate low paced rates during WI and VVIR modes with the upper rate response at 150 ppm. All studies were performed at least 2 weeks apart. Physiological values of heart rate, blood pressure, work rate (watts), oxygen comsumption (VO2), carbon dioxide production (VCO2), and respiratory exchange ratio (RER) were monitored continuously during each test using a 1 minute incremental treadmill protocol. Ventilatory anaerobic threshold (VAT) was calculated from VO2, VCO2, and minute ventilation. The results demonstrated that although there was a significant increase in paced heart rate per minute throughout exercise (P < 0.01) with VVIR pacing, maximum watts, VO2, and VAT remained unchanged. These findings indicate that in spite of an improved chronotropic response to exercise, children with Univentricular hearts following the Fontan procedure continue to demonstrate altered hemodynamics which negate potential benefits of VVIR pacing.
Automatic Reduction of Stimulus Polarization Artifact for Accurate Evaluation of Ventricular Evoked Responses
Authors: CURTIS ANNE B. , VANCE FRED , MILLER KIM
Published: July 2006

The ventricular evoked response, the cardmc depolarization generated in response to a pacing stimulus, is potentially useful as a sensorforrate responsive pacing and automatic threshold tracking. It is necessary to minimize the polarization artifact that results from pacing in order to sense cardiac depolarizations from the same electrodes that pace the heart. To accomplish this, a triphasic stimulus waveform consisting of precharge, stimulus, and poslcharge was used. An algorithm was developed that introduced pacing stimuli during the refractory period of sensed beats, when cardiac depolarization could not occur by definition and polarization artifact could be evaluated. Precharge duration was varied until the amplitude of the polarization artifact was small compared to the evoked response. In 18 patients with temporary electrode catheters, polarization artifact was reduced from 6.8 ± 3.4 mV to 1.9 ± 1.1 mV after balancing (P < 0.005). Initial precharge duration was 3200 μsec and the mean final precharge duration was 3551 ± 516 μsec. In 14 patients with permanent bipolar pacing leads, polarization artifact was reduced from 3.2 ± 3.5 mV to 0.7 ± 0.6 mV (P < 0.025). Final precharge duration averaged 3440 ± 310 μsec. Under a wide variety of pacing conditions, this algorithm simply and quickly reduces polarization artifact to a minimum to allow accurate analysis of evoked responses.
Orthogonal Electrode Catheter Array for Mapping of Endocardial Focal Site of Ventricular Activation
Authors: DESAI JAWAHAR M. , NYO HTAY , VERA ZAKAUDDIN , SEIBERT J. ANTHONY , VOGELSANG PHILIP J.
Published: July 2006

Precise location of the endocardial site of origin of ventricular tachycardia may facilitate surgical and catheter ablation of this arrhythmia. The endocardial catheter mapping technique can locate the site of ventricular tachycardia within 4–8 cm2 of the earliest site recorded by the catheter. This report describes an orthogonal electrode catheter array (OECA) for mapping and radiofrequency ablation (RFA) of endocardial focal site of origin of a plunge electrode paced model of ventricular activation in dogs. The OECA is an 8 F five pole catheter with four peripheral electrodes and one central electrode (total surface area 0.8 cm2). In eight mongrel dogs, mapping was performed by arbitrarily dividing the left ventricle (LV) into four segments. Each segment was mapped with OECA to find the earliest segment. Bipolar and unipolar electrograms were obtained. The plunge electrode (not visible on fluoroscopy) site was identified by the earliest wave front arrival times of ‐30 msec or earlier at two or more electrodes (unipolar electrograms) with reference to the earliest recorded surface ECG (I, AVF, and V1). Validation of the proximity of the five electrodes of the OECA to the plunge electrode was performed by digital radiography and RFA. Pathological examination was performed to document the proximity of the OECA to the plunge electrode and also for the width, depth, and microscopic changes of the ablation. To find the segment with the earliest LV activation a total of 10 ± 3 (mean ± SD) positions were mapped. Mean arrival times at the two earlier electrodes were ‐ 39 ± 4 msec and ‐35 ± 3 msec. Digital radiography showed the plunge electrode to be within the area covered by all five electrodes in all eight dogs. The plunge electrode was within 1 cm2 area of the region of RFA in all eight dogs. The width and depth of ablation were 5 ± 3.5 and 7 ± 3.5 mm, respectively. Microscopic changes revealed coagulative necrosis, hemorrhage, and inflammatory changes in all RFAs. In conclusion, the OECA can map the endocardial focal site of origin of paced ventricular activation within 1 cm2 area in a canine model. RFA from the OECA can cause discrete ablations representing all five electrodes or cross‐shaped ablation connecting central electrode to all four peripheral electrodes. This catheter holds promise for extending surgical and clinical catheter ablation procedures.
The Subpectoral Pocket: The Preferred Implant Site for Pediatric Pacemakers
Authors: GILLETTE PAUL C. , EDGERTON JIM , KRATZ JOHN , ZEIGLER VICKI
Published: July 2006

Implantation technique for pediatric pacemaking has evolved from predominantly epicardial to predominantly endocardial, One of the potential problems with endocardial pacing in children is their very thin subcutaneous tissue, which can result in an unpleasant cosmetic result. The superficialness of the pacemaker pulse generator also may render it more susceptible to erosion and infection. A series is presented of pediatric patients who underwent implantation of a transvenous bipolar pricing system in the pediatric catheterization laboratory. The pacemaker was implanted under the pecforalis major muscle after a muscle spreading incision was made. The lead was also introduced into the subclavian vein under the pectoraiis muscle. No complications resulted, and the cosmetic result was judged to be good to excellent by the parents and physicians. No infections or erosions occurred. The subpectoral pocket is recommended as the preferred site for implantation of transvenous pacemakers in pediatric patients.
Brady Cardie‐Dependent Early Afterdepolarizations in a Patient with QTU Prolongation and Torsade de Pointes in Association with Marked Bradycardia and Hypokalemia
Authors: SHIMIZU WATARU , TANAKA KOUICHI , SUENAGA KENJI , WAKAMOTG ATSUO
Published: July 2006

Endocardial monophasic action potentials (MAPs) were recorded at the right ventricular apex in a patient with QTU prolongation and torsade de poinles (TdP) in association with marked bradycardia and hypokalemia. There was a distinct hump on phase 3 repolarization of the MAPs characteristic of early afterdepolarizations (EADs), which was associated with marked prolongation of the QTU interval on the surface electrocardiogram. EAD amplitude was bradycardia dependent, and there was a strong correlation (r = 0.91) between the preceding RR interval and the amplitude of the EAD (percent of MAP amplitude). Intravenous administration of lidocaine or right ventricular pacing suppressed the ventricular premature complexes and TdP in association with the suppression of the EADs on the MAPs. Furthermore, these EADs were not recorded on the MAPs 1 month Iater when the QTU prolongation and TdP had disappeared. These findings suggest that the TU abnormality and QTU prolongation responsible for TdP were due to bradycardia‐dependent EADs.
Clinical Electrophysiological Effects of Intravenous Recainam: An Antiarrhythmic Drug Under Investigation for the Treatment of Ventricular and Supraventricular Arrhythmias
Authors: FELD GREGORY K. , LUCERI RICHARD M. , GREENSPON ARNOLD J. , SINGH BRAMAH N. , HOROWITZ LEONARD N. , CAPUZZI DAVID M. , FRAME VIRGINIA B. , MYERBURG ROBERT J.
Published: July 2006

This open‐label, multicenter study was designed to assess the electrophysiological properties of intravenous recainam, an investigational Class I antiarrhythmic agent. In 25 patients undergoing electrophysiological studies for the evaluation of arrhythmias, recainam was administered intravenously in a loading infusion (0.1 mg/kg/min) for 40 minutes, followed by a maintenance infusion (0.02 mg/kg/min) until the completion of the study. Electrophysiological measurements were obtained at baseline, 30 minutes after initiation of the loading infusion, and 30 minutes after termination of the infusion during washout. Conduction intervals, refractory periods, and sinus node recovery times were measured during sinus rhythm and during atrial or ventricular pacing. Vital signs were obtained and recorded before, during, and after recainam infusion. The results showed no change in mean arterial pressure, but heart rate increased slightly by 4 beats/min following recainam infusion. Recainam produced a generalized slowing of in‐tracardiac conduction. The mean intraatrial conduction time, measured at an atrial paced cycle length of 600 msec, increased during recainam loading infusion by 44%, from 38.8 ± 2.8 to 53.0 ± 5.4 msec; intranodal conduction time increased by 10%, from 102.0 ± 5.5 to 112.1 ± 5.2 msec; and infranodal conduction time increased by 31% from 53.1 ± 3.0 to 70.7 ± 3.8 msec. Slowed conduction persisted during washout. The mean right atrial effective refractory period was significantly prolonged (+ 7% at 600 msec cycle length and +8% at 450 msec cycle length, P < 0.05 and P < 0.01, respectively) during recainam loading and remained so during washout. However, the mean effective refractory period of the atrioventricular node was significantly prolonged only during the recainam loading infusion while pacing at 450‐msec cycle length (+ 8%, P < 0.05). In contrast, the mean effective refractory period of the right ventricle was not changed during or immediately after the infusion, but was significantly shortened 30 minutes later (‐4%, P < 0.05). Two of 25 patients (8%) developed adverse reactions requiring termination of the infusion. Five other patients (20%) developed less serious side effects during the recainam infusion, all of which resolved spontaneously and did not require termination of the infusion. The results demonstrate that recainam prolongs conduction in atrial, ventricular, and specialized cardiac conduction tissues. Recainam also prolongs atrial refractory periods, but has little or no effect on the sinus node or on AV nodal and right ventricular refractory periods. Thus, recainam is a Class I antiarrhythmic agent with a combination of electrophysiological properties suggesting its potential utility in the treatment of atrial and ventricular arrhythmias.
Retrospective Analysis of Patients Undergoing One‐ or Two‐Stage Strategies for Myocardial Revascularization and Implantable Cardioverter Defibrillator Implantation
Authors: PINSKI SERGIO L. , MICK MATTHEW J. , ARNOLD ANITA Z. , GOLDING LEONARD , MCCARTHY PATRICK M. , CASTLE LON W. , MALONEY JAMES D. , TROHMAN RICHARD G.
Published: July 2006

Internal defib‐rillation leads were placed at time of coronary revascularization in 79 patients. In 34, an implantable Cardioverter defibrillator (ICD) was placed simultaneously (group I). A two‐stage strategy (selective implantation of the ICD in patients with postoperative spontaneous or inducible ventricular tachycardia [VT]) was followed in 45 patients (group II). Group I patients had failed more antiarrhythmic drug trials (2.9 ± 1.6 vs 1.5 ± 1.6; P = 0.02), including amiodarone (62% vs 20%; P < 0.001). There were four operative deaths in each group. Postoperatively, VT was present in 27 group II patients (60%), 25 of whom received an ICD (two refused device implantation). Patients with postoperative VT had a lower left ventricular election fraction than those without VT (33 ± 9 vs 47 ± 16; P = 0.01). Actuarial survival at 1, 2, and 3 years was 88 ± 6, 88 ± 7, and 88 ± 10 in group I; and 83 ± 6, 76 ± 7, and 76 ± 11 in group II (NS). No patient without an ICD (based on the postoperative electrophysiological study [EPS]) died suddenly. Five patients (6%) had ICD system infection. Sudden death was largely prevented by either strategy, but relatively high rates of operative mortality and ICD system infection were observed. Prospective studies should identify patients more likely to benefit from one or another strategy.
Dispersion of Repolarization Induced by a Nonuniform Shock Field
Authors: KNISLEY STEPHEN B. , AFEWORK YOHANNES , LI JIANHUA , SMITH WILLIAM M. , IDEKER RAYMOND E.
Published: July 2006

Dispersion of repolarization may contribute to arrhythmias. To determine whether an electrical field stimulus (S2) with a nonuniform potential gradient can induce a dispersion of repolarization, we applied 5 ms rectangular S2 that had a nonuni/orm or uniform potential gradient during the action potential (AP) of bathed frog ventricular strips. One group had a partitioned bath to produce a nonuniform S2 of 39 ± 11 V/cm (mean ± SD) in one half of the 1 ± 6 mm strip (H) and 0.3 ± 0.2 V/cm in the other half (1), and simultaneous intraceflular AP recordings in H and L with glass microelectrodes positioned 1.4 ± 0.4 mm apart. Another group had uniform S2 and an AP recorded near the center of the strip. S1 pacing at 0.5 Hz was performed at one end of the strip and conduction along the strip was monitored. In each experiment, the S2 trials had an S1‐S2 interval of 300 ms so that S2 was given during an AP (shocked AP). In both H and L, nonuniform S2 produced cumulative shortening of paced APs and lengthening of each shock AP compared with the paced AP preceding it. Uniform S2 of 1 V/cm did not shorten (he paced APs or lengthen the shocked APs indicating that the AP changes in L were not due to the small potential gradient in L. Before beginning nonuniform S2 trials, (he AP duration determined at the maximum repolarization rate was 601 ± 72 ms in H and 602 ± 71 ms in L (P = ns). During 13–20 nonuniform S2 trials over a 60–80 minute period, paced APs were shortened to 490 ± 51 ms in H and 515 ± 39 ms in L while each shocked AP was lengthened, compared with the paced AP preceding it, to 636 ± 40 ms in H and 561 ± 21 ms in L (P < 0.05). Therefore, paced APs after shocks repolarized 25 ms earlier in H than in L and shocked APs repolarized 75 ms later in H than in L. The results show that during the shortened AP in H, the AP in L is shortened, which is consistent with intracellular current from L to H during repolarization. During the prolonged AP in H, the AP in L is prolonged compared with the paced AP preceding it, consistent with intracellu lar current from H to Lduring repolarization. Thus, nonuniform shocks can induce a dispersion of repolarization and may induce cell‐to‐cell interactions during re‐polarization.
Pacemaker Syndrome in a Patient with DDD Pacemaker for Long QT Syndrome
Authors: CHIEN WALTER W. , FOSTER ELYSE , PHILLIPS BARRY , SCHILLER NELSON , GRIFFIN JERRY C.
Published: July 2006

A patient with long QT syndrome was treated with bela blockers and had a permanent DDD pacemaker implanted. The lower rate was set to 85 beats/min because this provided the best shortening of QT interval at the lowest paced heart rate. The atrioventricular (AV) delay was programmed to 250 msec to allow native AV conduction. Patient returned complaining of symptoms suggestive of pacemaker syndrome. EGG during one of these episodes showed AV sequential pacing. Doppler echocardiography of hepatic vein flow suggested atrial contraction against a closed tricuspid valve. Endocardial electrogram telemetry demonstrated ventriculoatrial (VA) conduction with the retrograde atrial electrogram falling within the atrial re/ractory period and thus was not sensed. The following atrial stimulus did not capture because of the atrial refractoriness. Ventricular pacing proceeded after the programmed AV delay. Reprogram‐ming the AV delay to 200 msec restored AV synchrony by allowing the atrial stimulus to capture by placing it outside of the refractory period of the atrium. No further symptoms reported during six months of follow‐up.
Active Fixation of Endocardial Pacing Leads: The Preferred Method of Pediatric Pacing
Authors: FRIEDMAN RICHARD A. , MOAK JEFFREY P. , GARSON ARTHUR
Published: July 2006

Pacing system failure due to lead related problems may necessitate repositioning or explanation of the problem lead. Pediatric patients with permanent pacemakers have additional considerations that necessitate revision or explantation of pacing leads. Active fixation type leads appear to offer the physician advantages over passive fixation leads that may make them the lead of choice for use in children. We reviewed our experience with active fixation type leads to determine whether the ease with which these leads could be revised or explanted justified recommending their use in our patients. Eleven patients underwent 13 lead revisions. The time from implant to revision was a mean of 12.3 months. Six patients had previously undergone repair of a congenital heart defect. Modes of pacing were: DDD (seven); AAI (three); and VVI (one). Exposed, isodiametric leads accounted for 11/13 leads. Leads were successfully explanted in nine cases and repositioned in four cases. The only lead that could not be revised and resulted in retention was a nonisodiametric, retractable helix lead at the junction of the subclavian vein and clavicle. We conclude isodiametric active fixation leads can be safely repositioned or explanted in children and should he considered the preferred method for endocardial pacing in children.
Low Energy Catheter Ablation of a Posteroseptal Accessory Pathway Associated with a Diverticulum of the Coronary Sinus
Authors: CONNELLY DEREK T. , ROWLAND EDWARD , AHSAN ARIF J. , CUNNINGHAM DAVID
Published: July 2006

A 23‐year‐old man was resuscitated from ventricular fibrillation and subsequently shown to have the Wolff‐Parkinson‐White syndrome. Electrophyslological study demonstrated a posteroseptal accessory pathway, and coronary sinus angiography demonstrated that this was associated with a diverticulum of the coronary sinus. Catheter ablation was performed using a new low energy system. Five shocks were delivered within the coronary sinus diverticulum, with a cumulative energy of 39 joules (J). Accessory pathway conduction was blocked successfully, and there were no complications.
Experimental Study About Removal of the Implanted Tined Polyurethane Ventricular Lead by Radiofrequency Waves Through the Lead
Authors: EBE KATSUYA , FUNAZAKI TOSHIKAZU , AIZAWA YOSHIFUSA , SHIBATA AKIRA , FUKUDA TAKEAKI
Published: July 2006

Polyurethane pacemaker leads are: widely used nowadays. However, only a few studies have been done to investigate the fixation mechanism of polyurethane leads. To elucidate how pacemaker leads are fixed at the early phase after Implantation, polyurethane‐insulated fined ventricular leads were implanted in seven mongrel dogs. One to 4 months later. lips of the leads were anchored among the trabeculae and the distal part of the leads were encapsulated by whitish fibrous tissue. It was found that not organized thrombi, but cell reaction with various states of inflammatory cells was responsible for forming the fibrous tissue. We attempted to remove the lead In‐delivering radiofrequency wave through the lead. However, no lead could be removed.
Orthodromic and Antidromic Pacemaker Circus Movement Tachycardia
Authors: von KNORRE GEORG H. , ISMER BRUNO , VOSS WOLFGANG , WESTPHAL BERND
Published: July 2006

Pacemaker circus movement tachycardia (PCMT) during DDD pacing is usually sustained by retrograde natural and antegrade electronic atrioventricular (AV) conduction. As PCMT is often initiated by a ventricular premature beat (VPB) one method of its prevention is the programming of an atrial stimulus synchronously following a ventricular extrasystole. A patient is described with preserved antegrade, but without retrograde, i.e., VA, conduction. The optional pacemaker mode of synchronous atrial stimulation following a VPB caused an unusual PCMT sustained by retrograde electronic and antegrade natural AV conduction. This PCMT is similar to a natural reentry tachycardia, the most common variety of which (based on retrograde conduction) is termed antidromic and that which we describe is orthodromic.
Practical Aspects of Rate Adaptive Atrial (AAI,R) Pacing: Clinical Experiences in 44 Patients
Authors: BRANDT JOHAN , FÅHRAEUS THOMAS , OGAWA TADASHI , SCHÜLLER HANS
Published: July 2006

Forty‐four patients with sinus node disease and chronotropic incompetence but no evidence of AV conduction disturbances were treated with rate adaptive atriul (AAI,R) pacemakers. Medtronic Activitrax and Siemens Sensolog activity sensing single chamber pulse generators were used. Twentyfour patients (55%) had the bradycardia‐tachycardia syndrome. The mean folloiw‐up time is 20 ± 14 months (range 1–48, median 17 months). All patients remain alive. Two patients were reoperated upon for lead problems without change of pacing mode. One patient developed symptomatic: srecond‐degree Wenckebach block during follow‐up, and received a DDD,R system. Although 22 of the patients were treated with antiarrhythmic drugs postoperatively, no further cases of significant AV conduction disturbances were seen. During rapid atrial pacing, exercise‐induced enhancement of AV conduction was a consistent finding, although less pronounced in patients treated with beta‐blocking drugs. One patient developed permanent atrial fibrillation with an adequate ventricular rate. By systematic reprogramming procedures, QRS complex sensing through the atrial electrode could be demonstrated in 25 patients (23/28 with unipolar and 2/16 with bipolar leads). it could be counteracted effectively by pulse generator program selection in all cases. Forty‐two of 44 patients (95%) remain in AAI,R pacing with normal function, Rate adaptive atrial pacing can be successfully applied in this patient group.
Experience with a New Implantable Pacer‐, Cardioverter‐Defibrillator for the Therapy of Recurrent Sustained Ventricular Tachyarrhythmias: A Step Toward a Universal Ventricular Tachyarrhythmia Control Device
Authors: FROMER MARTIN , SCHLÄPFER JÜRG , FISCHER ADAM , KAPPENBERGER LUKAS
Published: July 2006

Ten consecutive patients (mean age 57.9 ± 7.6 years) were treated with an investigational tachyarrhythmia control device, the implantable Medtronic Pacer‐, Cardioverter‐, Defibrillator model 7216A or 72170. All patients had coronary artery disease with old myocardial infarctions and presented hemodynamically significant sustained ventricular tachyarrhythmias not suppressed by antiarrhythmic drug therapy and unrelated to acute myocardial infarction. In two patients a nonthoracotomy lead system was implanted. Lowest effective defibrillation energy ranged from 5 to 18 joules (mean 12.2 ± 4 joules) for the epicardial bielectrode systems and were 15 and 18 joules for the nonfhoracotomy lead system implants. The postoperative periods were unremarkable. Follow‐up ranged from 7 to 19 months (mean 13.8 ± 4.5 months). Spontaneous tachyarrhythmia episodes were detected and treated by the device in six patients, five of them received staged therapies. No deaths occurred and no hospital admissions were necessary for device related or ventricular tachyarrhythmia related complications. In conclusion, this integrated device represents a major step toward the development of a universal ventricular arrhythmia control device.
Crosstalk with External Bipolar DVI Pacing: A Case Report
Authors: DE KEYSER FRANK , VANHAECKE JOHAN , JANSSENS LUC , ECTOR HUGO , DE GEEST HILAIRE
Published: July 2006

An increase of the basic atrial pacing rate from a preset value of 70 beats/min up to 91 beats/min was recorded in a patient with an external bipolar dual chamber pacing system. This observation could be explained by the occurrence of crosstalk; this specific manifestation of crosstalk was the result of the use of an uncommitted DVI pacing mode.
Intravenous 3‐Methoxy‐O‐Desmethyl‐Encainide in Reentrant Supraventricular Tachycardia: A Randomized Double‐Blind Placebo‐Controlled Trial in Patients Undergoing EP Study
Authors: WARE DAVID L. , LEE JOHN T. , MURRAY KATHERINE T. , HANYOK JAMES J. , RODEN DAN M. , ECHT DEBRA S.
Published: July 2006

Encainide is an agent effective in atrioventricular and atrioventricular nodal reentrant tachycardia. The metabolites O‐desmethyl encainide and 3‐methoxy‐O‐desmethyl encainide (MODE) are responsible for the clinical effects of encainide in most patients. In this study, intravenous MODE was evaluated in eight patients with reentrant Supraventricular tachycardia undergoing electrophysiological testing. After tachycardia was induced at least twice to ensure reproducibility, MODE (30 μg/kg/min ± 15 min, then 7.5 μg/kg/min) or placebo was administered in a double‐blind fashion. If tachycardia remained inducible, the infusion was unblinded; in nonresponding subjects who received placebo, MODE was then administered. Placebo was ineffective in 3/3 patients. MODE prevented tachycardia induction in 5/8 patients and increased the tachycardia cycle length from 302 ± 38 to 413 ± 67 msec in the other three. At a mean concentration of 774 ± 229 ng/ml, MODE prolonged PR, AH, HV, QRS, and QT intervals, right ventricular and accessory pathway effective refractory periods, and slowed or blocked antegrade accessory pathway conduction. Changes in intracardiac conduction were rate independent between cycle lengths 400 to 600 msec, while changes in ventricular effective refractory periods were most pronounced at rapid pacing rates. No adverse effects, hemodynamic changes, or conduction disturbances occurred. Thus, MODE can modify or suppress induction of reentrant atrioventricular or atrioventricular nodal tachycardia. The study design used here is well suited for the evaluation of newer antiarrhythmic agents by electrophysiological testing.
Fourier Analysis in Patients with Different Pacing Modes
Authors: SANTOMAURO MAURIZIO , FAZIO SERAFINO , FERRARO SERGIO , MADDALENA GIOVANNI , PAPACCIOLI GIUSEPPE , PAPPONE CARLO , BETOCCHI SANDRO , CHIARIELLO MASSIMO
Published: July 2006

The purpose of this study was to evaluate the usefulness of phase analysis in detecting the altered activation sequence induced by different pacing modes. Radionulide ventriculography and planar gated blood pool scintigraphy were performed at rest in 56 patients with different pacemakers. This method permitted us to localize the pacemaker impulse site in the right ventricie and its diffusion in the heart. In patients with VVI pacemaker, this technique showed an evident asynchronism of contraction and relaxation of each ventricle and the standard deviation of phase angle (σ), calculated by computer, is greater during pacing than sinus rhythm for left (LV) and right (RV) ventricles (LV σ: 17°± 4 vs 11°± 3, < 0.001; RV σ: 31°± 7 vs 14°± 4, P < 0.001). In the patients with VVI rate responsive pacemakers, the LV σ changed from 18.5 ± 3 under pacing to 11°± 3 in sinus rhythm, P < 0.001, while the RV σ changed from 30°± 8 to 14°± 4, P < 0.001. Instead in the patients with DDD pacemakers, the LV σ changed from 15.5°± 2 under pacing to 11°± 3 in sinus rhythm, P < 0.05, while the RV cr changed from 29.1°± 6 to 14°± 4, P < 0.001. Besides in patients with VDD pacemakers, the LV σ changed from 14.9°± 3 during pacing to 11°± 3 in sinus rhythm, P < 0.01, and from 27.5°± 5 to 14°± 4 for the right ventricle, P < 0.01. So the technique of Fourier analysis permits us to examine the effects of a temporal inhomogeneity induced by different pacing modes, and it can be utilized to assess the optimal atrioventricular delay in DDD paced patients.
Transesophageal Atrial Pacing—Stimulation and Discomfort Thresholds: The Role of Electrode Configuration and Pulse Width
Authors: RES JAN C.J. , VAN WOERSEM RUURD J. , DEKKER EGBART , DUNNING AREND J.
Published: July 2006

A balloon catheter with six electrodes has been developed for transesophageal atrial stimulation of the human heart. Introduction is easy and its positioning is simple with the help of six unipolar atrial electrograms. In a group of 20 healthy volunteers, stimulation and discomfort thresholds (intolerable discomfort) were measured for three levels of pulse widths (12, 16, and 20 msec) and for five electrode configurations. Stimulation thresholds were below discomfort thresholds in each case. The stimulation threshold depended on pulse width and not on electrode configuration. The discomfort threshold, however, depended on the electrode configuration and not on the pulse width. A moderate but potentially important increase of the ratio between stimulation threshold and discomfort threshold could be achieved by combining a long pulse width (20 msec) and avoiding the largest distance between the active (cathode) and the passive (anode) electrode. Transesophageal atrial stimulation promises to be a practical noninvasive tool for the termination of regular supraventricular tachycardias, basal electrophysiological studies, and controlled acceleration of the heart rate in the study of myocardial ischemia.
MCL1 and MCL6 Compared to V1 and V6 in Distinguishing Aberrant Supraventricular from Ventricular Ectopic Beats
Authors: DREW BARBARA J. , SCHEINMAN MELVIN M. , DRACUP KATHLEEN
Published: July 2006

Use of V1 and V6 has been suggested for distinguishing aberrant supraventricular from ventricular ectopy, For two decades, “modified” leads MCL1 and MCL6 have been widely used as V1 and V6 substitutes for bedside monitoring, but their use has never been validated. To determine the value of MCL1 and MCL6, 81 morphologically distinct wide QRS ectopic beats were recorded from 46 patients during cardiac electrophysiological study. As determined by the His‐bundle electrogram, 31 of the ectopics were aberrant supraventricular, 50 were ventricular, A new criterion, measurement of QRS onset to the predominant peak or nadir of the complex, was valuable in diagnosing wide complexes in MCL6 and V6. An interval of SO msec or less predicted aberrant Supraventricular ectopy; an interval of 70 msec or more predicted ventricular ectopy. There was agreement between the modified and conventional precordial leads regarding which QRS patterns were useful in distinguishing aberrant supraventricular from ventricular ectopy, A greater proportion of wide complexes in MCL1 and V1 exhibited patterns useful in making the diagnosis compared to MCL6 and V6. Using well‐established criteria, the proportion of correct diagnoses that was made from individual leads was: MCL1—86%, V1= 85%, MCL6= 72%, V6= 67%. The bedside leads (MCL1 and MCL6) were not statistically different in diagnostic accuracy from their conventional lead counterparts (V1 and V6); however, MCL1 and V1 were superior to MCL6 and V6, When the new criterion was added to make the diagnosis from MCL6 and V6 no difference in diagnostic accuracy was present between the four leads.
Comparative Efficacy of Subcutaneous Mesh and Plate Electrodes for Nonthoracotomy Canine Defibrillation
Authors: NOGAMI AKIHIKO , TAKAHASHI ATSUSHI , NITTA JUNICHI , AONUMA KAZUTAKA , IESAKA YOSHITO , HIROE MICHIAKI , MARUMO FUMIAKI , HIRAOKA MASAYASU
Published: July 2006

To determine the optimal configuration for the subcutaneous placement of electrodes for the performance of ventricular defibrillation without thoracotomy, internal defibrillation using four different subcutaneous electrodes was performed in 13 anesthetized dogs (7–12 Kg, mean ± SD: 9.2 ± 1.5 Kg). An electrode (7 cm2) was positioned transvenously in the superior vena cava with the following electrodes randomly implanted subcutaneously on the left chest: small mesh electrode (14 cm2), large mesh electrode (28 cm2), small titanium plate electrode (14 cm2), and large plate electrode (28 cm2). Ventricular fibrillation was induced by applying alternating current: a monophasic defibrillation wave was administered between (he superior vena cava and the subcutaneous electrodes 10 seconds later. The energy level associated with a 50% successful defibrillation, as predicted by logistic regression analysis, was defined as the ED50. After the completion of the defibrillation protocol using the four subcutaneous electrodes, the small mesh electrode was sutured to the epicurdium and the ED50 measurements were repeated. Energy ED50s were lower when the superior vena cava electrode was used as the cathode rather than as the anode. Of the subcutaneous electrodes, the large plate electrode showed the lowest energy ED50 (3.3 ± 0.9 joules). The plate electrodes had lower energy ED50s than the mesh electrodes, and the large electrode had a lower energy ED50 than the small electrodes. Using the epicurdium electrode, transient arrhythmias and ST elevation were observed following successful defibrillation; however, no arrhythmias or ST‐T changes were observed following defibrillotion using the subcutaneous electrodes. In another eight dogs (7–12 Kg, 9.8 ± 2.0 Kg), seven subcutaneous titanium plate electrodes (surface areas 7, 14, 28, 42, 56, 70, and 98 cm2) were randomly implanted on the left chest. Increasing the surface area of the subcutaneous electrode from 14 to 70 cm2 (from 2 to 5 cm2/Kg) produced a significant reduction in the energy ED50. However, a further increase in the surface area did not further reduce the ED50. In conclusion, the subcutaneous plate electrode significantly reduced the ED50 as compared to the mesh electrodes. The optimal size of electrode for reducing the defibrillation threshold was approximately 5 cm2/Kg.
Dual Chamber Pacing Aborts Vasovagal Syncope Induced by Head‐Up 60° Tilt
Authors: FITZPATRICK A. , THEODORAKIS G. , AHMED R. , WILLIAMS T. , SUTTON R.
Published: July 2006

To determine if pacing might prevent syncope in cardioinhibitory ‘Malignant Vasovagal Syndrome’ (also known as ‘Neurally‐Mediated Bradycardia/Hypotension’), a study of dual chamber pacing during head‐up 60° tilt was undertaken. Paired invasive tilts were performed in 10 patients who had a history of recurrent syncope, normal routine investigations including electrophysiological study and prior tilt induced vasovagal syncope. Vasovagal reactions of identical severity were produced by prolonged 60° head‐up tilt on consecutive days in seven out of 10 patients. On day 2, without pacing, seven patients had tilt‐induced vasovagal reactions and six became syncopal during the reaction. On day 3, with temporary DVI pacing with rate hysteresis, seven patients had tilt‐induced vasovagal reactions and 1 patient was syncopal. Syncope was aborted in the other five patients. DVI pacing significantly improved cardiac index (CI) (one ± 0.2 to 1.6 ± 0.3 L/min/m2, P < 0.01) and mean arterial blood pressure (MABP) (30 ± 11 to 48 ± 12 mmHg, P < 0.01) during vasovagal reactions on day 3 compared with day 2. The mean period of time that patients could tolerate in the tilted position after the onset of the tilt‐induced vasovagal reaction was significantly prolonged by pacing from 0.9 ± 1.2 to 3.2 ± 1.6 min (P < 0.01). Dual chamber pacing may abort syncope in 85% of patients with cardioinhibitory malignant vasovagal syndrome. Pacing may prolong consciousness sufficiently during a vasovagal reaction to allow injury to be avoided.
Implantable Electrical Stimulator‐Alloprosthesis in Repair of Postoperative Hernias
Authors: PEKARSKY VIKENTY V. , SHPILEVOY PETER K. , DERUGHINA MARIA S. , GLUSCHUK SERGEY Ph.
Published: July 2006

An implantable electrical stimulator‐alloprosthesis produced better regeneration of connective tissue for prevention of recurrences in patients after surgery for postoperative hernias. The experiments demonstrated that the use of the electrical stimulator‐alloprosthesis resulted in significant improvement in connective tissue regeneration, tissue proliferation through the prosthesis and in the speed of postoperative suture healing. The device was successfully used in 30 patients. The period of treatment decreased by an average of 10 days. The method is recommended for wide clinical use, especially in cases of postoperative recurrent hernias and in patients with suppressed regenerative ability of connective tissue.
Ninety‐Six Episodes of Spontaneous Ventricular Tachycardia in 1 Week: Success of Ramp Pacing by a Pacer‐Cardioverter‐Defibrillator
Authors: PORTERFIELD JAMES G. , PORTERFIELD LINDA M. , BRAY LOUISE
Published: July 2006

This case report describes the flexibility and usefulness of a pacer‐cardioverter‐defibrillator for the management of a 63‐year‐old patient with malignant ventricular tachyarrhythmias. Ninety of 96 episodes of ventricular tachycardia were terminated successfully with ramp pacing in a 1‐week period. In those patients who have frequent episodes of ventricular tacycardia that respond to antitachycardia pacing, the multifunction device can add to the patient's comfort and increase acceptance of this type of device.
Inappropriate Shocks and Elevation of Defibrillation Thresholds in a Patient with Automatic Defibrillator Patch Silastic Erosion and Titanium Mesh Fraying
Authors: MITTLEMAN ROBERT S. , MACK KEITH , RASTEGAR HASSAN , MANOLIS ANTONIS S. , ESTES N. A. MARK
Published: July 2006

A case is presented of a defibrillator patch erosion, inappropriate shocks, and high defibrillation thresholds in a 59‐year‐old man requiring thoracotomy for proper diagnosis and management.
Radiofrequency Catheter Ablation for Wolff‐Parkinson‐White Syndrome Associated with a Coronary Sinus Diverticulum
Authors: LESH MICHAEL D. , VAN HARE GEORGE , KAO ANN K. , SCHEINMAN MELVIN M.
Published: July 2006

The case of a patient with Wolff‐Parkinson‐White syndrome undergoing attempted radiofrequency catheter ablation of a left posterior paraseptal accessory pathway is described. Coronary sinus venography revealed the presence of a large diverticulum attaching near the os. The electrogram recorded from a catheter placed in the narrow neck of the diverticulum revealed a very short atrioventricular time during sinus rhythm. The pathway was easily ablated using radiofrequency energy applied in the neck of the diverticuham, after multiple failed attempts at catheter ablation from the endocardial surface of the mitral annulus. Our report emphasizes the importance of searching for a coronary sinus diverticulum's in all patients with posterior accessory pathways undergoing catheter ablation.
Bradycardia and Syncope in Children Not Controlled by Pacing: Beta‐Adrenergic Hypersensitivity
Authors: PERRY JAMES C. , FRIEDMAN RICHARD A. , MOAK JEFFREY P. , GARSON ARTHUR
Published: July 2006

Cardiac pacing is frequently employed in the therapy of children with syncope and documented bradycardia. This report describes two children, ages 7 and 9 years, who underwent placement of demand ventricular pacing systems for documented bradycardia and syncope. Cardiac cathe‐terization and intracardiac electrophysiological studies failed to show evidence of structural abnormalities, sinus node or conduction system disease, inducible arrhythmias, or VA conduction in each patient. Both patients had persistent symptoms after pacemaker implantation. Autonomic function testing with continuous heart rate and blood pressure monitoring revealed exaggerated beta‐adrenergic responses to simple standing and small doses of isoproterenol. Symptoms were completely eliminated with atenolol. In these two children, cardiac pacing alone was not adequate for relief of symptoms. Autonomic mechanisms of bradycardia and hypotension should be considered prior to implantation of permanent pacing systems in children.
Sudden Bradyarrhythmic Death in Patients with the Implantable Cardioverter‐Defibrillator: Report of Two Cases
Authors: KHASTGIR TERRANCE , AARONS DIANA , VELTRI ENRICO
Published: July 2006

Two cases of sudden bradyarrhythmic death necessitating cardiopulmonary resuscitation in patients with the automatic implantable cardioverter‐defibrillator are described. One patient had sudden bradyarrhythmic death while being monitored in the hospital. This patient could not be resuscitated and represents the first reported sudden cardiac death secondary to bradyarrhythmia in a patient with the automatic implantable cardioverter‐defibrillalor. The second patient had an out‐of‐hospital sudden death followed by probable cardioverter‐defibnllator discharge, leading to complete heart block with escape ventricular rhythm necessitating immediate temporary pacemaker insertion. These cases highlight the need for bradycardia back‐up pacing and event monitoring in the newer tachyarrhythmia management devices.