bluuebunny/crossref_metadata_2025 huggingface dataset:
Myocardial Mechanics Before and After Ablation of Chronic Tachycardia
Authors: FISHBERGER STEVEN B. , GOLAN STEVEN D. , SAUL J. PHILIP , MAYER JOHN E. , WALSH EDWARD P.
Published: July 2006

Chronic tachycardia has been shown to cause a congestive cardiomyopathy; however, previous methods of evaluating ventricular function are highly dependent on cardiac loading conditions. Mean velocity of fiber shortening and its relation to end‐systolic wall stress (ESS) is a preload independent index of contractility that incorporates afterload. We reviewed 33 patients (aged 6 months to 20 years; mean 9.7 years) with ectopic atrial tachycardia (EAT) (n = 19), permanent functional reciprocating tachycardia (PfRT) (n = 12), or ventricular tachycardia (n = 2). who underwent nonpharniacological elimination of tachycardia; 28 by radiofrequency ablation and 5 surgically. Ventricular function was evaluated by echocardiographic measurements of shortening fraction, mean velocity of shortening corrected for heart rate (VcFc), and afterload as ESS. Contractility, expressed as the stress‐velocity index, was determined by comparing the ESS/VcFc relation to the predicted normal VcFc for the measured ESS. Myocardial dysfunction was seen in 21 patients: 13 with EAT; 7 with PJRT; and 1 with ventricular tachycardia. In patients with EAT, the mean heart rate in tachycardia was significantly faster in those with dysfunction than in those without dysfunction (176.8 ± 32.2 vs 136.7 ± 28.2; P < 0.02). Of the 21 patients with dysfunction, full recovery was seen in 17 of 18 patients restudied after intervention (mean 17.5 ± 17.6 weeks), and the remaining patient improved markedly, but did not normalize entirely. Dysfunction, seen in 64% of young patients with chronic tachycardia, was due to depressed myocardial contractility, and is generally reversible within 3 months of definitive therapy.
Effects of Polarity for Monophasic and Biphasic Shocks on Defibrillation Efficacy with an Endocardial System
Authors: USUI MASAHIRO , WALCOTT GREGORY P. , STRICKBERGER S. ADAM , ROLLINS DENNIS L. , SMITH WILLIAM M. , IDEKER RAYMOND E.
Published: July 2006

Electrode polarity has been reported to be one of the factors that affect defibrillation efficacy. We studied the influence of polarity on defibrillation efficacy when monophasic and biphosic waveforms were used with an endocardial lead system. In six anesthetized pigs, defibrillation catheters were placed in the right ventricular (RV) apex and at the junction of the superior vena cava (SVC) and right atrium. Monophasic shocks were 6 ms in duration, while for biphasic shocks the first phase was 6 ms and the second was 4 ms in duration. Four electrode configurations were tested: R:S, M (the RV electrode, cathode; the SVC electrode, anode, with a monophasic shock); S:R. M; R:S, B (the RV electrode, first phase cathode; the SVC electrode, first phase anode, with a biphasic shock); S:R, B. Defibrillation probability of success curves were determined using an up/down protocol requiring 15 shocks for each configuration. For monophasic shocks, total delivered energy at the 50% probability of success point was significantly lower when the RV electrode was an anode than when it was a cathode (R:S, M: 24.4 ± 7.4 J [mean ± SD] vs S:R, M: 16.4 ± 5.5 J; P < 0.05). For biphasic shocks, total energy was not affected by polarity reversal of the electrodes (R:S, B: 8.7 ± 1.4 J vs S:R, B: 8.4 ± 2.5 J; P = NS). The endocardial electrode configuration with the RV electrode as an anode requires less energy for defibrillation with a monophasic but not a biphasic waveform.
Clinical Benefit of Dual Chamber Pacing in Hypertrophic Cardiomyopathy: A Case Report
Authors: TEIXEIRA JOSE M. , GREENWAY PATRICIA S. , STAEDTLER CAROL , BAREIS REUBEN
Published: July 2006

This case study presents evidence that angioplasty and dual chamber pacing can be used as a therapeutic alternative to coronary artery bypass grafting and myectomy. The following case report describes this treatment option in a patient with hypertrophic Cardiomyopathy and ischemic heart disease who refused surgery. A severe coronary lesion was successfully treated with percutaneous transluminal coronary angioplasty (PTCA), Subsequent deterioration of the patient's clinical status occurred, yet a repeat heart catheterization revealed no angiographic changes from the PTCA. The left ventricular outflow gradient was 97 mmHg despite optimizing medical therapy. Temporary pacing leads were inserted and the patient was DDD paced at 70 ppm while measuring the LVgradient at varying A V intervals. Significant reduction of the outflow tract gradient occurred at all A V intervals tested. Although the pressure gradient decreased during VVI pacing, atrial contribution was necessary to achieve the desired hemodynamic benefit. A permanent DDDR pacemaker was implanted with satisfactory clinical results.
Removal of Endocardial Defibrillation Leads
Authors: JORDAENS LUC , Van BELLEGHEM YVES , HERREGODS LUC
Published: July 2006

Two patients, each with an endocardial defibrillation lead system (Endotak O62), required lead removal; one because of chronic lead infection and the second because of spurious shocks caused by lead insulation damage. Neither lead could be removed by simple traction. The defective lead was removed by a combination of catheterization techniques including a steerable ablation catheter and traction, both under general anesthesia. The lead with the insulation defect was rapidly removed with a locking stylet, suggesting that endocardial lead defibrillating leads can be removed similarly to pacemaker leads, thus avoid thoracotomy.
Double Atrial Responses to a Single Ventricular Impulse in Long RP′ Tachycardia
Authors: YAMABE HIROSHIGE , OKUMURA KEN , TABUCHI TOSHIFUMI , TSUCHIYA TAKESHI , YASUE HIROFUMI
Published: July 2006

Double atrial responses (DARs) to a single ventricular impulse have been described in patients with long RP' tachycardia. To define the determinants for the occurrence of DARs. 8 cases with long RP' tachycardia were examined. The mechanism of long RP' tachycardia was the orthodromic atrioventricular reciprocating tachycardia (AVRT) involving a slow conducting concealed accessory pathway in 4 cases and uncommon (fast‐slow) type of atrioventricular nodal reentrant tachycardia (AVNRT) in the other 4 cases. Programmed and rapid ventricular pacing was performed during sinus rhythm and also rapid ventricular pacing during tachycardia (i.e., entrainment). The retrograde effective refractory period (ERP) and the retrograde maximal 1:1 conduction rate of the fast and slow conducting pathways were examined. In 1 of the 4 cases with AVRT, DARs were observed during programmed and rapid ventricular pacing, performed during sinus rhythm and also during entrainment. In 1 of the 4 cases with AVNRT, DARs were observed only during entrainment. The determinants of DARs in cases with long RP' tachycardia were: (1) presence of two different retrogradely conducting pathways; (2) short ERP of the retrograde fast and slow conducting pathways and a short minimal pacing cycle length at which 1:1 ventriculoatrial conduction occurs via these pathways; (3) crucial conduction delay in the slow conducting pathway: and (4) preexisting antegrade unidirectional block in the slow conducting pathway or the antegrade block in the slow conducting pathway produced by collision with a previous retrograde impulse during entrainment.
A Critical Period of Ventricular Fibrillation More Susceptible to Defibrillation: Real‐Time Waveform Analysis Using a Single ECG Lead
Authors: HSIA PENG‐WIE E. , FRERK SYLVIA , ALLEN CYNTHIA A. , WISE ROBERT M. , COHEN NERI M. , DAMIANO RALPH J.
Published: July 2006

Previous studies have suggested that variations in the underlying ventricular fibrillation (VF) waveform may be one of the factors responsible for the probabilistic nature of defibrillation. The heart appeared to be more susceptible to defibrillation at higher absolute VF voltages (AVFV). This study investigated in an open‐chest canine model (n = 8), a newly developed system that analyzed the VF waveform in real‐time, instantaneously determined the time to shock, and immediately delivered a fixed low energy DC shock. A two parameter tracking technique using a running long‐term and short‐term AVFV average was devised to automatically identify a high voltage peak area of the VF waveform, which has been hypothesized to represent a critical period susceptible to defibrillation. Using a DC shock estimated at the 50% success level, the performance using this technique in 58 defibrillation trials was compared to the performance of the conventional method of shocking at a fixed time (random shock method) in 62 trials. Patch size, electrode location, and discharge voltage were kept constant while VF duration, transmyocardial resistance (TMR), energy delivered, and AVFV at the point of shock were measured. Shock energy and current, TMR, and VF duration were similar with both shock methods. A significantly higher AVFV was observed for trials performed with the peak shock method (0.66 ± 0.02 mV) as compared to trials performed with the random shock method (0.25 ± 0.09 mV) (P < 0.003). Using lead II as the only sensing lead, the success rate was increased in 6 of 8 dogs (75%) with the new method. One animal showed identical performance, and one animal a worse performance. The overall increase in success rate was 24% using a single ECG lead (range 0%‐100%; P < 0.04). Our data document that using this algorithm a period of high VF voltage can be detected in realtime. The improved success in the majority of animals supports the hypothesis that a critical period susceptible to defibrillation exists during VF. However, the high AVFV detected using a single ECG lead did not translate to an improved success rate in all animals. This suggests that other factors in addition to the VF voltage measured on a single lead of the ECG are important in characterizing this critical period.
Immediate and Day‐to‐Day Reproducibility of the Signal‐Averaged Electrocardiogram in Patients with Coronary Artery Disease
Authors: PAQUAY JEAN LOUIS , ZIMMERMANN MARC , MERMILLOD BERNADETTE , ADAMEC RICHARD
Published: July 2006

The purpose of this study was to prospectively evaluate the immediate (5 minutes) and short‐term (1 day) reproducibility of the signal‐averaged electrocardiogram (SAECG) in patients with coronary artery disease. A total of 59 consecutive patients with coronary artery disease (50 male, 9 female, mean age 59 ± 13 years) were included. Analysis was performed using a commercially available system with high‐pass filters of 25, 40, and 80 Hz without any change in electrode position. The following time‐domain parameters were measured: (1) total filtered QRS duration; (2) duration of high‐frequency low‐amplitude signals (HFLA); and (3) root‐mean‐square voltage of the terminal 40 ms of the QRS complex (RMS40). Correlation between pairs of measurements was excellent, ranging from 0.91–0.99 for QRS and HFLA duration, and from 0.83–0.98 for RMS40 value. However, the range of differences was wide for all parameters, especially at 25 and 80 Hz, revealing marked individual variations in selected cases. The immediate reproducibility of an initially normal SAECG was 95% at 25 Hz, 100% at 40 Hz, and 81 % at 80 Hz; figures for an initially abnormal SAECG were 89%, 91 %, and 93%, respectively, and the coefficient of agreement kappa was highest at 40 Hz than at 25 or 80 Hz. Discordant results were most frequently observed in patients with borderline values, or in cases with nonsimilar residual noise levels. In conclusion, the immediate and day‐to‐day reproducibility of the SAECG is excellent in patients with chronic stable coronary artery disease. However, individual variations are observed in selected cases, leading to modification in interpretation of the result. For this reason, individual reproducibility should be considered before evaluating the effect of any therapeutic intervention on the SAECG, especially in patients with borderline values of the quantitative parameters of the SAECG.
Activation Times for “Emergency Backup” Programs
Authors: FORNEY RICHARD C. , SWEESY MARK W. , SECKINGER BRAD , TALBOTT PATRICK , ERICKSON STEVEN L. , BATEY ROBERT L.
Published: July 2006

A bench study was performed on 42 different pulse generators (PGs) to evaluate the time required to actuate an “emergency backup” (EBU) program. PGs were programmed to loss of capture before the EBU programming key was activated. Activation times for the EBU pause were measured on an ECG strip from the first noncaptured beat to the first recaptured beat while the total pause was measured between the two captured beats. Each test was performed five times. Special features for temporary threshold testing were also evaluated. Mean activation times for EBU pauses ranged from 1.46–11.90 seconds with total pauses of 2.18–12.94 seconds. Significant differences were observed for EBU activation times from the same PG but utilizing older and newer generation programmers, e.g., 10.90 (old) versus 4.54 seconds (new) for a mean EBU pause. Extreme variations existed in EBU activation times for programmers with multiple “EBU keys” for the same PG, e.g., 12.94 versus 4.96 seconds for the mean total pause. The special features for temporary threshold testing resulted in mean EBU pauses measuring 0.62–2.88 seconds and mean total pauses of 1.21–3.76 seconds. The special features were significantly faster than manual activation of the “EBU key” for regaining capture with few exceptions. Activation times were complicated by multiple programmers for the same PG and several “EBU keys” on the same programmer.
Development of an Interactive Computer‐Guided Method for Radiofrequency Catheter Ablation of Ventricular Tachycardia
Authors: COHEN TODD J. , GOLDNER BRUCE G. , JADONATH RAM , HORWITZ LEORA , QUAN WEILUN
Published: July 2006

The purpose of this study was to develop a simple computer‐guided approach to localizing ventricular tachycardias during ventricular mapping. Six patients with sustained monomorphic ventricular tachycardia were connected to a 32‐lead computer body surface mapping system. Isoarea maps of induced ventricular tachycardia were recorded. Then a pacing probe was placed in either the right or left ventricle, and maps were generated from a variety of sites. Differences between ventricular tachycardia and pace map maxima X,Y coordinates were utilized to guide catheter manipulation and localization. In 6 of 6 patients (100%) this method appeared to provide a systematic approach to ventricular tachycardia localization. Computer‐generated correlations as well as the X,Y coordinates of the QRS isoarea maxima were used to determine proximity to the ventricular tachycardia foci and direct catheter manipulation. In the next three patients this method was applied prospectively to help guide catheter manipulation during ventricular tachycardia (two right ventricular outflow tract tachycardias, and one left ventricular tachycardia). After a mean of 4.0 ± 1.7 radiofrequency applications, ventricular tachycardia was no longer inducible, and at 7 ± 0 months follow‐up there have been no arrhythmia recurrences. We conclude that online computerized body surface mapping can assist in localizing ventricular tachycardia. Differences in maxima during pace maps and in‐situ ventricular tachycardias can help with catheter manipulation as well as with more precise identification of focal tachycardias. This technique appears to hold the promise of a simple computer‐guided method that may facilitate radiofrequency catheter ablation.
No Output or Runaway?
Authors: SWEESY MARK W. , FORNEY RICHARD C. , ERICKSON STEVEN L. , CALABRIA DOMINICK A.
Published: July 2006

A 75‐year‐old male was implanted with a Telectronics MetaTM DDDR model 1250 pacemaker 47 months ago. The patient was evaluated in‐office for symptomatic complaints of dizziness, palpitations, and “too slow or too fast” pulse rates. Upon examination, the device displayed sudden no output manifestations for which the device had been recalled. However, the device further displayed erratic paced rates to 200 ppm, switching between VVIR and DDDR modes. To the best of our knowledge, this is a previously unreported manifestation in this recalled device and needs to be addressed due to its potentially hazardous patient effects.
Serial Fluoroscopic Evaluation of a Pacing Lead
Authors: LLOYD MARGARET A. , HAYES DAVID L. , HOLMES DAVID R.
Published: July 2006

A recall of the Telectronics Accufix™ 330–801 atrial lead was issued in November 1994, because of fracture of the “J”‐shaped retention wire. To assess the integrity of the retention wire, we have performed fluoroscopic screening on 209 patients with the Accufix 330–801 atrial lead in place. Cine films of ail 135 patients originally classified as normal were reevaluated after the original screening. Eighty patients have undergone two serial fluoroscopic evaluations separated by 158 ± 5.4 days. Nine retention wires originally classified as normal were reclassified as fracture without protrusion, and two were reclassified as fracture with protrusion when the original films were reevaluated. Eight of the 11 leads reclassified were screened during our first 2 days of fluoroscopic evaluation of this lead. Of the 80 patients who underwent a second fluoroscopic screening, 70 were initially classified as normal (9 of which were reclassified as described above), 1 fractured, and 9 indeterminate. There were no new fractures detected in this group, and the fractured retention wires did not appear to change during this observation period. We conclude that there is a definite learning curve associated with fluoroscopic evaluation of this lead, and continue to recommend that screening be performed by cardiologists experienced in fluoroscopic screening. Fractured retention wires remained stable in appearance during this observation time. No new retention wire fractures were detected: however, longer follow‐up will be required before the incidence of retention wire fracture can be determined.
Monomorphic Right Ventricular Tachycardia in a Patient with Mitral Valve Prolapse
Authors: KOSMAS CONSTANTINE E. , DALESSANDRO DAVID A. , LANGIERI GARY , RUBIN ANDREW M. , RIALS SETH J. , MARINCHAK ROGER A. , KOWEY PETER R.
Published: July 2006

A patient with mitral valve prolapse and symptomatic ventricular ectopy underwent an electrophysiological study during which a sustained monomorphic ventricular tachycardia with a left bundle branch block/right axis deviation morphology was induced. This morphology was replicated by pace mapping at the right ventricular outflow tract. To the best of our knowledge, this finding has not been previously described and suggests that the association between ventricular arrhythmias and mitral valve prolapse may not necessarily be causal.
Use of Pacemaker Diagnostic Functions for Recognition and Management of Cardiac Arrhythmias
Authors: KAMALVAND KAYVAN , TAN KIM , WILLEMS ROGER , SULKE NEIL
Published: July 2006

Pacemakers are becoming increasingly sophisticated, offering a host of new diagnostic functions. This case illustrates how some of these functions can be used to help with the diagnosis and management of patients with pacemakers who suffer from cardiac arrhythmias.
Comparison of Single‐Biphasic Versus Sequential‐Biphasic Shocks on Defibrillation Threshold in Pigs
Authors: CSANADI ZOLTAN , JONES DOUGLAS L. , WOOD G. KIM , KLEIN GEORGE J.
Published: July 2006

Current generation implantable cacdioverter defibrillators use monophasic, biphasic, or sequential pulse shocks, most of which truncate after a given time, dumping the remaining charge on the capacitor through an internal resistor. We hypothesized that having an additional current pathway, and delivering the majority of the remaining charge on a single capacitor to the two pathways using additional shock phases, would improve defibrillotion efficacy. This hypothesis was tested by comparing DFTs using a simulated single capacitor, single‐biphasic shock (two 5‐ms pulses separated by 0.2 ms), delivered to coupled pairs of electrodes, to those using a sequential‐biphasic shock (four 5‐ms pulses separated by 0.2 ms) delivered to separate opposing electrodes, delivered from the same electrodes for both woveforms. In eight open‐chest anesthetized pigs, four mesh electrodes (Medtronic TX‐7. 6.5 cm2), were sutured on the epicardium of the anterior and posterior surfaces of each ventricle. Shocks were delivered from a 200‐μF capacitor bank. Triplicate DFTs were obtained using each waveform in a randomized crossover design. Initial leading edge voltage (mean ± SEM: 420 ± 33 V vs 497 ± 34 V; P < 0.05). initial peak current (4.8 ± 0.4 Avs 13 ± 1.1 A: P < 0.001). and delivered energy (16.9 ± 2.6 J vs 30.4 ± 5.3 f; P < 0.05) at the DFT were all significantly lower using sequential‐biphasic shocks than those using single‐biphasic shocks, respectivelv. We conclude that for direct heart defibrillation, it is worthwhile to combine sequential capability to biphasic shocks and deliver the remaining charge on the capacitor to the two different pathways.
The Use of Left Ventricular Epicardial Surface Velocity Patterns as a Marker of Pacing Site
Authors: MCINERNEY JOSEPH J. , HERR MICHAEL D. , LUCK JERRY C. , ORLEDGE JEFFREY D.
Published: July 2006

Ectopic ventricular foci were simulated at selected endocardial sites in 15 closed‐chest canines using ventricular pacing. During this pacing, a noninvasive x‐ray backscatter imaging technique was used to measure epicardial LV displacements at 5‐ms intervals during the cardiac cycle. These displacement measurements were used to calculate epicardial surface velocities in each study and were presented as a time sequence of color coded velocity maps. Characteristic patterns in the timing and spatial propagation of LV surface velocities were noted for each pacing site, particularly during the expansion of the LV during isovolumic contraction and the inward motion of the LV during ejection. Average surface velocity maps for the 15 canines were computed for each pacing site. These average maps were used as standards for comparison with individual pacing studies to determine the probable site of pacing. Comparisons were made using a computer algorithm, based upon auto‐ and cross‐correlation techniques in the time domain. This algorithm correctly identified pacing sites with sensitivities of HA 74%, LV 76%, RV 79%, and RVOT 77% and specificities of RA 98%, LV 96%, RV 90%, and RVOT 93%. The results show that this noninvasive mapping procedure has potential for identifying the location of an ectopic ventricular focus.
Influence of Early Coronary Reperfusion on QT Interval Dispersion After Acute Myocardial Infarction
Authors: ENDOH YASUHIRO , KASANUKI HIROSHI , OHNISHI SATOSHI , SHIBATA NITARO , HOSODA SAICHI
Published: July 2006

We studied the influence of early coronary reperfusion on QT interval dispersion in patients with acute myocardial infarction (MI). Tbere were 54 males and 18 females witb a mean age of 60 ± 10 years. Of the 51 patients with recanalization of the infarct related vessel in the recovery phase, 28 (group A) had early coronary reperfusion (5.5 ± 2.7 bours), 23 other patients (group B) were not confirmed with early coronary reperfusion. Twenty‐one patients (group C) did not undergo recanalization of the infarct related vessel in the recovery phase. Corrected QT (QTc) maximum, QTc minimum, and QTC dispersion calculated as tbe difference between the maximum and minimum QTc intervals, were compared among these three groups at both acute and recovery phase. At the acute phase after MI, there were no significant differences in the QTc maximum, QTc minimum, QT dispersion, and QTc dispersion among these three groups. At the recovery phase after MI, there were also no significant differences in the QTc maximum and QTc minimum. However, there were significant differences in the QT dispersion (0.035 ± 0.010 in group A, 0.049 ± 0.015 in group B, and 0.061 ± 0.031 s in group C, respectively; P = 0.0001), and QTc dispersion (0.038 ± 0.012 in group A, 0.050 ± 0.015 in group B, and 0.063 ± 0.032 s in group C, respectively; P = 0.0003) among the three groups. Comparison of QTc dispersion between acute and recovery phase revealed significant reduction from acute to recovery phase in group A. The number of premature ventricular contraction was lower in groups A and B than group C. In summary, early coronary reperfusion may reduce electrophysiological instability by reducing QT dispersion in the recovery phase after acute MI.
Sudden Cerebral Vasoconstriction During Induced Polymorphic Ventricular Tachycardia and Fibrillation: Further Observations of a Paradoxic Response
Authors: GRUBB BLAIR P. , DURZINSKY DENNIS , BREWSTER PAMELA , GBUR CAROLYN , COLLINS BRAD
Published: July 2006

To determine the effect of induced polymorphic VT/VF on the cerebral circulation, transcranial Doppler (TCD) ultrasonography was used to prospectively assess changes in cerebral blood flow velocity during ICD implantation. Fourteen patients (13 men, 1 woman, mean age 58 ± 20 years, range 34‐74 years) who were survivors of an out of hospital cardiac arrest, were evaluated during routine ICD implantation. TCD ultrasonography was used to assess middle cerebral artery systolic velocity (Vs), diastolic velocity (Vd), pulsatility index (PI = Vs– Vd/Vmean) and resistance index (RI = Vs‐ValVs) before, during, and after DFT testing with alternating current induction of polymorphic VT/VF. In each of the 14 patients studied, concomitant with the abrupt onset of hypotension, TCD sonography demonstrated a 33%± 28% decrease in diastolic velocity, a 42%± 28% increase in systolic velocity, a 190%± 141% increase in FI, and a 44%± 19% increase in RI. These findings reflect an increase in cerebrovascular resistance secondary to arteriolar vasoconstriction distal to the point of insonation of the middle cerebral artery. This response is paradoxic, as the expected response of the cerebral circulation to hypotension is vasodilation, but it is consistent with observations made in other acute hypotensive settings, such as tilt induced neurocardiogenic syncope.
Regional Wall Motion During Pacing for Hypertrophic Obstructive Cardiomyopathy
Authors: JEANRENAUD XAVIER , KAPPENBERGER LUKAS
Published: July 2006

In order to assess the influence of right ventricular stimulation on LV contraction sequence in hypertrophic obstructive cardiomyopathy (HOCM), we performed a regional wall‐motion analysis of the left ventricle by comparing normal His‐Purkinje activation to pacing from the right ventricular apex. In 9 patients (5 males and 4 females, mean age 61 ± 9 years) assessed after a mean pacing period of 12 weeks (range 7–24 weeks), AV sequential pacing induced a 52% reduction in maximal pressure gradient from 76 ± 36 to 40 ± 28 mmHg (P < 0.01) as determined by Doppler examination. Regional wall‐motion analysis of the left ventricle was computed from digitized two‐dimensional echocardiographic images by means of the area shrinking method. Pacing induced a significant reduction of total septal area shrinking from 25%± 17% to 12%± 17% (P < 0.005). A tendency toward paradoxical septal motion was observed in one patient only. The apex showed no significant variation. A 6% increase in area shrinking was observed at the posterior wall and lateral free wall, from 38%± 13% to 43%± 10% (P < 0.05). Pacing did not significantly alter the global ejection fraction. A direct correlation between the magnitude of subaortic pressure gradient reduction and that of septal motion changes was found in a majority of patients. In conclusion, dual chamber pacing reduces septal wall motion in patients with HOCM obstructive cardiomyopathy. Tins might be one of the mechanisms involved in the reduction of LV outflow tract obstruction.
Distortion of Intracardiac Electrograms Following Defibrillator Shocks for Atrial Tachyarrhythmias
Authors: KHALIGHI KOROUSH , FLORIN TODD J. , PETERS ROBERT W. , SHOROFSKY STEPHEN R. , GOLD MICHAEL R.
Published: July 2006

In three patients with a defibrillator system consisting of a Ventak P2 pulse generator and an Endotak C transvenous lead, we observed distortion of introcardiac electrograms following defibrillator shocks for atrial arrhythmias. There was a transient marked widening of the intracardiac ventricular complexes resembling ventricular tachycardia. This phenomenon should be recognized when evaluating arrhythmic episodes.
Maturation of the Sensed Electrogram Amplitude Over Time in a New Subcutaneous Implantable Loop Recorder
Authors: KRAHN ANDREW D. , KLEIN GEORGE J. , YEE RAYMOND , NORRIS CARO
Published: July 2006

The cause of recurrent syncope may be difficult to determine if the diagnosis is not establisbed from initial noninvasive and invasive testing. Eighteen patients with recurrent syncope and negative tilt table and electrophysiological testing underwent implantation of a left pectoral subcutaneous loop recorder. This device “freezes” the preceding 7.5 or 15 minate rhythm strip after magnet application after spontaneous syncope. Baseline and follow‐up electrograms were routinely recorded, and patients were followed until syncope recurred. Three patients bad syncope within 1 month of implantation and were excluded from this report. Implantation electrogram amplitude was 250 ±124 /μV and increased to 291 ±114 μV at 2–3 months, and increased further to 353 ± 167 μV at 4–6 months (P < 0.001, ANOVA). Syncope recurred in 14 of the 15 patients. An arrhythmic basis for syncope was established (n = 7) or excluded (n = 7) in every patient who had recurrent syncope. All syncopal episodes were associated with diagnostic sensed electrograms. The increase in sensed electrogram amplitude over time suggests a maturation of the device‐tissue interface. These results support the long‐term viability of this implantable monitoring technique.
High Thresholds May Alter End‐of‐Life Behavior in a Dual Chamher Pacemaker
Authors: KRAUS MARTIN , BUCKINGHAM THOMAS A. , CANDINAS RETO
Published: July 2006

We noted a series of 12 consecutive patients with a DDD Genisis® pacemaker that showed an unexpected and a relatively rapid fall in battery voltage and output as these devices approached end‐of‐life (EOL). Twenty‐one of 24 leads were Vitatron Helifix® leads and there was a relatively high mean threshold (atrial 2.5 ± 0.94 V: ventricular 2.9 ± 0.65 V) These devices were replaced after 65 ± 12 months. During the 9.3 ± 3.5 months before replacement, a striking fall in voltage from 2.7 ± 0.04 V to 2.49 ± 0.05 V was seen. Battery impedance rose from 3 ± 1.2 KΩ to 10.2 ± 4.3 KΩ during this same period. We unexpectedly observed a marked difference between programmed and telemetered output for both atrial (50%) and ventricular leads (30%). A discrepancy between measured and telemetered magnet rate was also seen. Despite this relatively rapid fall in battery voltage, several of these devices did not meet the manufacturer's recommended replacement time (RRT) criteria by magnet rate or according to the projected RRT determined by the relationship of battery impedance to current drain. These data have implications for the selection of RRT and EOL criteria for this device. Magnet rate measured by surface ECG was the safest indicator for RRT. Follow‐up for this pulse generator should be increased to every 2 months when battery impedance is > 2 KOhms or if there is a difference between programmed and measured output amplitude of more than 15%. The data also highlight the effect of combining high threshold leads with modern pacemakers with relatively “small” batteries as well as certain problems with telemetered data
Safety of Slow Pathway Ablation in Patients with Long PR Interval: Further Evidence of Fast and Slow Pathway Interaction
Authors: NATALE ANDREA , GREENFIELD RUTH ANN , GEIGER MARY JANE , NEWBY KEITH H. , KENT VIRGINIA , WHARTON J. MARGUS , KEARNEY MARGARET M. , BRANDON M. JOAN , ZIMERMAN LEANDRO
Published: July 2006

Whether the presence of abnormal PR before selective slow pathway ablation for AV node reentrant tachycardia increased the risk of complete heart block remains controversial. We report our experience in seven patients with prolonged PR intervals undergoing catheter ablation for AV reentry tachycardia. Their mean age was 66 ± 12 years; four patients were female and three were male. RF ablation was performed using an anatomically guided stepwise approach. In six patients, common type AV node reentry was induced and uncommon type was observed in the remaining patient. In all seven patients, successful selective slow pathway ablation was associated with no occurrence of complete heart block and was followed by shortening of the AH interval in five patients. In all seven patients, successful ablation was achieved at anterior sites (M1 in two patients and M2 in five patients). Despite AH shortening after ablation, the 1:1 AV conduction was prolonged after elimination of the slow pathway, excluding either sympathetic tone activation or parasympathetic denervation. In conclusion, selective slow pathway ablation can be performed safely in the majority of patients with prolonged PR interval before the procedure. Because successful ablation is achieved at anterior sites in most patients, careful selection and monitoring of catheter position is required.
Inappropriate Discharges of an Implantable Cardioverter Defibrillator Secondary to Automatic Adjustable Gain of Atrial Tachycardia
Authors: SCHECTER STUART O. , GREENBERG STEVEN M. , HOGH DAVID H. , GESA MIGHAEL , LEVINE JOSEPH H.
Published: July 2006

Third generation implantable cardioverter defibrillators are capable of complex arrhythmia detection using sensing algorithms with automatic adjustable gain settings. We report a unique case where inappropriate sensing of atrial tachycardia in a patient with a His bundle ablation lead to satisfaction of ventricular fibrillation detection criteria.
Inadequacy of Qualitative Implantable Cardioverter Defibrillator Electrogram Analysis to Distinguish Supraventricular from Ventricular Tachycardia Due to Electrogram Changes During Normally Conducted Complexes
Authors: HALLETT NANETTE , MONAHAN KEVIN , CASAVANT DAVID , EPSTEIN LAURENCE , JOSEPHSON MARK
Published: July 2006

Stored electrograms (EGMs) recorded from ICD leads are used to evaluate the appropriateness of ICD therapies. Stored EGMs different from sinus have been interpreted as ventricular in origin. We present a patient with a n ICD for VT wh o received multiple shocks for a tachycardia with a stored EGM different than sinus, suggesting VT. An electrophysiological study demonstrated EGMs different than sinus during atrial pacing and induced supraventricular arrhythmias. This case points out the limitations of stored EGMs and suggests complete electrophysiological study with analysis of ECMs during induced arrhythmias should be performed prior to discharge.
Right Hemidiaphragmatic Twitching: A Complication of Bipolar Atrial Pacing
Authors: KHAN AFTAB A. , NASH ANTONY , RING NICHOLAS J. , MARSHALL ANDREW J.
Published: July 2006

A patient with an atrioventricular sequential pacemaker developed rhythmic contractions of the right hemidiaphragm. This was found to be the result of right phrenic nerve stimulation, which was directly related to the wide distance between the poles of an ELA atrial lead when pacing in bipolar mode. Pole separation in current atrial leads is discussed.
Implantation of Dual Chamber Pacemaker in a Patient with Persistent Left Superior Vena Cava
Authors: ANTONELLI DANTE , ROSENFELD TIBERIO
Published: July 2006

A 35‐year‐old patient underwent permanent pacemaker implantation because of symptomatic sinus bradycardia. During the procedure, persistent left superior vena cava was found. The ventricular lead crossed the tricuspid valve only after curving the stylet to form a loop in the right atrium (RA); subsequently, the curved stylet was changed to a straight one and the lead was positioned and screwed into the right ventricular apex. The atrial lead positioning was possible when the stylet was slightly curved and the lead could reach the anterior wall of the RA. At 18 months, a follow‐up revealed normal pacemaker function and stable lead position.
Preimplant Atrial Defibrillation Testing with a Temporary Catheter in Sheep
Authors: ELABBADY TAREK Z. , TACKER WILLIS A. , GEDDES L.A. , AYERS GREGORY M.
Published: July 2006

Prior to implantation of an atrial defibrillator, its effectiveness should be tested in each patient. A new catheter design for temporary use with electrodes for atrial defibrillation, electrogram sensing, and pacing was tested in this study. Atrial defibrillation thresholds defined using this temporary catheter were compared to the ones defined by catheters intended for chronic use with an implantable atrial defibrillator. Atrial defibrillation threshold was determined in six sheep using both types of catheters. Each animal was subjected to studies on 2 consecutive days. On the first day, shocks were applied between two of the temporary catheters. On the following day, permanent leads were inserted and atrial defibrillation threshold was redetermined. In both cases, defibrillation electrodes were positioned in the same heart location with one electrode in the distal coronary sinus and the second electrode in the right atrium. Atrial defibrillation threshold was obtained using 10 V increments or decrements to determine the lowest shock intensity needed to defibrillate the atria. Threshold was defined as the shock intensity at which 20 shock percent success was at or between 15 % and 85%. Statistical analysis showed no significant difference (P < 0.05) between atrial defibrillation threshold energy (0.53 J vs 0.55 J), voltage (122 V vs 120 V) or current (2.2 A vs 2.6 A) measured with the temporary catheters and the permanent leads, respectively. These data indicate that temporary catheters can be used for efficacy testing prior to implant of an atrial defibrillator, and that they predict atrial defibrillation threshold adequately for chronic leads.
AAIR Versus DDDR Pacing in Patients with Impaired Sinus Node Chronotropy: An Echocardiographic and Cardiopulmonary Study
Authors: VARDAS P.E. , SIMANTIRAKIS E.N. , PARTHENAKIS F.I. , CHRYSOSTOMAKIS S.I. , SKALIDIS E.I. , ZURIDAKIS E.G.
Published: July 2006

The aim of this study was to compare AAIR and DDDR pacing at rest and during exercise. We studied 15 patients (10 men, age 65 ± 6 years) who had been paced for at least 3 months with activity sensor rate modulated dual chamber pacemakers. All had sick sinus syndrome (SSS) with impaired sinus node chronotropy. The patients underwent a resting echocardiographic evaluation of systolic and diastolic LV function at 60 beats/min during AAIR and DDDR pacing with an AV delay, which ensured complete ventricular activation capture. Cardiac output (CO) was also measured during pacing at 100 beats/min in both pacing modes. Subsequently, the oxygen consumption (VO2at) and VO2at pulse at the anaerobic threshold were measured during exercise in AAIR mode and in DDDR mode with an AV delay of 120 ms. The indices of diastolic function showed no significant differences between the two pacing modes, except for patients with a stimulus‐R interval > 220 ms, for whom the time velocity integral of LV filling and LV inflow time were significantly lower under AAI than under DDD pacing. At 60 beats/min, CO was higher under AAI than under DDD mode only when the stimulus‐R interval was below 220 ms. For stimulus‐R intervals longer than 220 ms, and also during pacing at 100 beats/min, the CO was higher in DDD mode. The stimulus‐R interval decreased in all patients during exercise. The time to anaerobic threshold, VO2at ond VO2at pulse showed no significant differences between the two pacing modes. Our results indicate that, at rest, although AAIR pacing does not improve diastolic function in patients with SSS, it maintains a higher CO than does DDDR pacing in cases where the stimulus‐R interval is not excessively prolonged. On exertion, the two pacing modes appear to be equally effective, at least in cases where the stimulus‐R interval decreases in AAIR mode.
Vibration, Acceleration, Gravitation, and Movement: Activity Controlled Rate Adaptive Pacing During Treadmill Exercise Testing and Daily Life Activities
Authors: CANDINAS RETO , JAKOB MARKUS , BUCKINGHAM THOMAS A. , MATTMANN HEIDY , AMANN F. WOLFGANG
Published: July 2006

Activity‐based sensors for rate adaptive pacing have been available for several years and now include several different types: vibration; acceleration; gravitation; and movement. However, a systematic comparison evaluating the relative advantages and disadvantages of these various sensors has received little study. The purpose of the present study was to compare these sensor subtypes using treadmill testing and an outdoor test circuit, which simulated daily life activities and included both uphill and downhill walking. Pacemakers were strapped on the chest of healthy volunteers and connected to one channel of an ambulatory recording device, which also recorded the subject's intrinsic heart rate. The pacemakers were programmed using an initial treadmill test to standardize the rate responsive parameters for each device. Nine different pacemaker models were studied including 3 vibration‐based (Elite. Synchrony, Metros). 4 acceleration‐based (Relay, Excel, Ergos, Trilogy), 1 gravitational‐based (Swing), and 1 movement‐based (Sensorithm) device. All devices demonstrated a prompt rate response with casual walking on flat ground. The vibration‐, gravitational‐, and movement‐based pacemakers showed a pronounced rate decline during more strenuous work, e.g., walking uphill. This phenomenon was absent in the accelerometer‐based units. In particular, the vibration‐ and movement‐based units showed a higher rate with walking downhill compared to uphill. An optimally tuned rote behavior on the treadmill usually did not provide an optimal rate behavior during daily activities and there was a tendency to overstimulation during low workload. The development of the two newest sensors (gravitational and movement) did not result in an improved performance of rate response behavior. Overall, the accelerometer‐based pacemakers simulated or paralleled sinus rate behavior the most closely.
Predictors of Psychosocial Adjustment in Patients with Implantable Cardioverter Defibrillators
Authors: BURGESS ELLEN S. , QUIGLEY JOHN F. , MORAN GEORGE , SUTTON FREDERIGK J , GOODMAN MARK
Published: July 2006

Predictors of psychological distress/adjustment were examined in 25 patients following placement of ICDs. Patients completed a demographic questionnaire and a standardized questionnaire of psychological symptoms (i.e., Symptom Checklist‐90 Revised; SCL‐90‐R). The number of discharges categorized by the patient as inappropriate and appropriate were also ascertained. The number of ICD discharges categorized as inappropriate and diminished levels of physical activity (r = 0.53 and 0.63, P < 0.01, respectively) did significantly relate to overall psychological distress. In addition, after controlling for age and prior psychiatric and physical health status through a stepwise multiple regression analysis, the occurrence of ICD discharges categorized as inappropriate and diminished physical activity continued to significantly predict overall psychological distress (R2= 0.41, P < 0.01). However, the number of ICD discharges categorized as appropriate did not significantly predict overall psychological distress. The results of this investigation suggest that further refinement of the ICD could reduce the risk of exposure to potential psychological distress, and an analysis of prior and anticipated patient physical activity levels should be a factor when calibrating minimum ICD discharge threshold levels.
Autonomic Effects on Noise Recorded During Signal‐Averaged Electrocardiography
Authors: AHMED MIRZA W. , KADISH ALAN H. , INBAR SHMUEL , GOLDBERGER JEFFREY J.
Published: July 2006

The purpose of this study was to assess the effects of autonomic stimulation and blockade on noise levels and to compare the noise measurements in the ST and TP segments of the signal‐averaged ECG. Five‐minute electrocardiographic data were recorded in 14 normal volunteers (8 males and 6 females; mean age 28.5 ± 5.0 years) on two separate days (day 1—baseline, epinephrine infusion, isoproterenol infusion, β‐blockade, and combined adrenergic and parasympathetic blockade; day 2—baseline, phenylephrine infusion, parasympathetic blockade, and during phenylephrine infusion following atropine). Signal averaging was done off‐line on 100 beats and noise was measured in both the ST and TP segments as the standard deviation of voltage in the segment of interest. For all conditions tested, the mean noise level measured in the ST segment (0.46 ± 0.16 μV) was significantly less than that measured in the TP segment (0.52 ± 0.24 μV; P = 0.0003). but there was good correlation between the noise measured in the STand the TP segment (R2= 0.62, P < 0.0001). Noise increased with isoproterenol infusion and decreased following adrenergic blockade. In addition, day 2 baseline noise was less than baseline noise on day 1. Finally, neither parasympathetic stimulation or blockade nor α‐adrenergic stimulation significantly affected signal‐averaged electrocardiography (SAECG) noise levels. Thus, the data support the notion that enhanced sympathetic tone increases noise levels and β‐adrenergic blockade may decrease noise levels, likely due to effects from muscle sympathetic nerve activity. These findings are important since the target population for the SAECG are patients with myocardial infarction and congestive heart failure, conditions associated with increased sympathetic tone, which may in turn impact on the reproducibility or technical aspects of the SAECG. In addition, because noise in the ST and TP segments are highly correlated and the noise measured in the ST segment is less than that in the TP segment, uniform adoption of noise measurement in the ST segment seems most appropriate.
Initial Experience with a Co‐Radial Bipolar Pacing Lead
Authors: TANG CHUEN , YEUNG‐LAI‐WAH JOHN A. , QI ANZHEN , MILLS PAULINE , CLARK JACQUELINE , TYERS FRANK
Published: July 2006

A new type of endocardial bipolar pacing lead has been designed to overcome the potential drawbacks of the conventional coaxial bipolar pacing had. We prospectively evaluated the new co‐radial bipolar pacing leads (Intermedics Thin Line), which are thinner (5 Fr vs 6—8 Fr) than standard coaxial bipolar leads. X‐ray visibility and lead handling were subjectively assessed (excellent, good, adequate, or poor) at implant; lead impedance, sensitivity threshold, and pacing threshold were measured at implant, then at 1, 3. 6, 12, and 18 months. The results were as follows: 103 patients (51 M; age 63.8 ± 17.4 years) received 71 atrial (A) and 89 ventricular (V) leads. X‐ray visibility was excellent in 59/103; good in 23/103; adequate in 11/103; and poor in 10/103. Overall handling was excellent in 56/71 A and 69/89 V; good in 11/71 A and 18/89 V; adequate in 3/71 A and 1/89 V; poor in 1/71 A and 1/89 V. There were two perioperative complications. At implant: impedance in A and V were 370.1 ± 74.7 and 501.5 ± 124.4 Ω, sensing thresholds in A and V were 3.0 ± 1.5 and 9.9 ± 5.0 mV, pacing thresholds at 0.45 ms in A and V were 0.59 ± 0.21 and 0.41 ± 0.15 volt, respectively. At 1, 3, 6. 12, and 18 months of follow‐up: no pacing lead related complications were reported; pacing lead characteristics remained outstanding and stable. This new lead appears to have significant clinical advantages over the conventional coaxial bipolar pacing lead. Long‐term follow‐up is required to confirm its reliability and chronic performance characteristics.