bluuebunny/crossref_metadata_2025 huggingface dataset:
Esophageal P‐Synchronous Pacing
Authors: MOURA PAULO , DEMORIZI NESTOR M. , MACMILLAN ROBERT M. , MORSE DRYDEN P. , GESSMAN LAWRENCE J.
Published: July 2006

An esophageal electrode can be employed to provide atrial sensing which then can be used to change from temporary right ventriculor (VVI) pacing to P‐synchronous (VAT) pacing. Two cases of postoperative aortic valve replacement, each with new complete heart block (CHB) and dopamine dependency, are presented. In both cases, establishment of P‐synchronous pacing resulted in improved hemodynamic status characterized by successful weaning from dopamine and maintenance of adequafe cardiac output (CO).
Atrial and Ventricular Burst Pacing from a Coronary Sinus Catheter: Relation to Position of Radiofrequency Transmitter
Authors: MARCHLINSKI FRANCIS E. , EYSMANN SUSAN
Published: July 2006

A young woman with drug‐refractory recurrent supraventricular tachycardia was managed by rapid atrial stimulation using a catheter positioned in the coronary sinus. During follow‐up, radiofrequency activation of the pacemaker resulted in burst ventricular and/or atrial pacing, depending on the distance of the transmitter's antenna loop from the receiver. Current output was directly related to the distance of the transmitter's antenna Joop from the receiver and ranged from 20 mA at a distance of 0 cm from the receiver to 1 mA at 5 cm. If possible, coronary sinus lead placement should be avoided for radiofrequency‐activated atrial burst pacing given the large current output with direct contact of the transmitter's antenna loop to the implanted receiver and the risk for ventricular stimulation. Alteration of the spatial relationship between the transmitter and receiver can be used to decrease current output and prevent ventricular pacing if atrial burst pacing from the coronary sinus is desirable.
Atrial Pacing Bigeminy: A Manifestation of Crosstalk
Authors: KERSSCHOT IVO E. , ORTMANNS PAUL , GOETHALS MARC A.
Published: July 2006

Atrial pacing bigeminy. defined as atrial pacing with alternating short and long cycle lengths, was recorded in two out of five DDD‐pacemaker implants. Another fascinating feature, the lowering of the effective pacing rate after programming to a higher rate, occurred in one patient. Both phenomena can be explained by crosstalk; appropriate programming resulted in normal DDD‐function in all cases. These observetions in our patients have led to some interesting conclusions regarding multiprogrammability and nominal settings.
Late Potentials and Arrhythmogenesis *
Authors: EL‐SHERIF NABIT. , GOMES JOSEPH A. C. , RESTIVO MARK , MEHRA RAHUL
Published: July 2006

There are three current prognostic indicators of ventricular electrical instability. (1) categorization and siratification of sponlaneous ventricular arrhythmias from standard ECG recordings; (2) programmed electrical stimulation; (3) direct recording of delayed depolarization potentials, usually re/erred to as late potentials. Of the three, the latter offers a new and promising approach. Late potentials represent delayed activation potentials of diseased myocardial zones and may prove to be a strong independent marker of the propensity to develop reentrant ventricular arrhythmias and sudden cardiac electrical death. The problem in identifying late potentials on the body surface is that the signal is smaller than the electrical noise produced by various sources. Two different techniques have been utilized to improve the signal‐to‐noise ratio: first, signal averaging, which is applicable to regular repelifive electrocardiographic signals but cannot detect moment‐to‐moment dynamic changes in the signal; second, low‐noise or high‐resolution electrocardiography that utilizes spatial averaging techniques as well as other noise‐reducing measures to record the late potentials on a beat‐to‐beat basis. This technique has the potential of directly identifying malignant “reentrant” versus benign “focal” ventricular rhythms. The present report discusses the electrophysiologic basis of late potentials and the clinical results of both signal‐averaged and low‐noise recordings for evaluation of ventricular electrical instability, particularly in patients with ischemic heart disease.
Simultaneous Recording of Atrial and Ventricular Monophasic Action Potentials: Monophasic Action Potential Duration During Atrial Pacing, Ventricular Pacing, and Ventricular Fibrillation
Authors: STROOBANDT ROLAND , BRACHMANN JOHANNES , BOURGEOIS IVAN , WIELDERS PIERRE , KÜBLER WOLFGANG , SENGES JOCHEN
Published: July 2006

A newly developed transvenous suction electrode was used in dogs to record monophasic action potentials (MAPs) from the right atrium and right ventricle simultaneously. Continuous MAP recordings could be made from the same endocardial site for test periods of 1.5 hours. Left ventricular pacing at increasing heart rates resulted in a statistically significant decrease of right ventricular MAP duration. A high degree of correlation was found between right ventricular MAP duration at 90% of repolarization and the QT interval during both right atrial and left ventricular pacing. At the onset of ventricular fibrillation (VF), right ventricular MAP duration shortened to 25% of the value obtained during left ventricular pacing at a cycle length of 250 ms. A cyclic alternation in amplitude of the right ventricular MAPs was observed during VF. Fast Fourier Transform Analysis of right ventricular MAPs during VF showed a significant dominant frequency at 12 Hz, with no levels of interest beyond this frequency. This observation might prove to be useful in elaborating a new algorithm for the automatic detection of ventricular fibrillation.
Use of the Pill Electrode for Transesophageal Atrial Pacing
Authors: JENKINS JANICE M. , DICK MACDONALD , COLLINS STEVE , O'NEILL WILLIAM , CAMPBELL ROBERT M. , WILBER DAVID J.
Published: July 2006

The pill electrode, which was developed for esophageal electrocardiography, has found application in transesophageal atrial pacing during procedures such as conversion of tachycardia, electrophysiologic measurement, and acceleration of heart rate to produce stress during cardiac imaging studies. This paper presents theoretical studies that examine the relationship of interelectrode distance, current level, and pulse duration to the achievement of successful capture. Theoretical results agree with our clinical findings, i.e., current levels of 25 mA are effective to sustain capture; increased pulse duration reduces current requirements; and close bipolar spacing combines efficacy with safety. Results of animal studies performed to assess the extent of esophageal burn injury reveal that current levels in excess of 75 mA are required to produce lesions in short‐term (under 30) minutes pacing, and greater than 60 mA in long‐term (4 hours) pacing. These results are based on experiments using a pulse duration of 2 ms, and the current levels that produce injury will be considerably lower if longer pulse durations are used. Typical current levels and pulse durations for successful capture are presented for 46 subjects in several new clinical applications. Termination of tachycardia, basic electrophysiologic measurements, and controlled acceleration of heart rate can be performed noninvasively with this technique.
Torsades de Pointes Due to N‐Acetylprocainamide
Authors: STEVENSON WILLIAM G. , WEISS JAMES
Published: July 2006

A 66‐year‐old female with chronic renal failure received five doses of procainamide and developed marked QT interval prolongation and recurrent episodes of torsades de pointes. which were temporally related to high serum n‐acetylprocainamide (NAPA) levels and not to procainamide levels. Repeated hemodialysis was effective in lowering NAPA levels. Torsades de pointes is a potential hazard of NAPA accumulation during procainamide administration to patients with renal insufficiency.
A Connection Box Allowing Simultaneous Recording of Electrograms and Shock Delivery for Treatment of Cardiac Arrhythmias
Authors: KERSEMAKERS JAN , BRUGADA PEDRO , WELLENS HEIN J. J.
Published: July 2006

A description is given of a connection‐box allowing the simultaneous recording from three electrodes and the delivery of a high‐energy shock for ablation of cardiac areas involved in generation or conduction of cardiac impulses.
Alternate Ventriculo‐Atrial Wenckebach Conduction during Ventricular Tachycardia
Authors: LÉVY SAMUEL , METGE MARC , COINTE ROLAND , FAUGERE GÉRARD , VALEIX BERNARD , GATAU‐PELANCHON JACQUELINE , GERARD RAYMOND
Published: July 2006

Although pacing‐induced ventriculo‐atrial (VA) Wenckebach conduction has been previously described, the occurrence of this phenomenon during ventricular tachycardia has received little attention. The latter is defined as 2:1 VA block in which the conducted beats show progressive lengthening of VA conduction until the sequence is terminated by two or three blocked ventricular beats. This phenomenon was observed in a 16‐year‐old boy who underwent electrophysiologic study for ventricular tachycardia as a late complication of surgical correction of tetralogy of Fallot. During pacing‐induced ventricular tachycardia with a morphology similar to that of the spontaneous tachycardia, 8:4 alternating VA block was observed. This sequence suggested that the AV node was the site of block, the 2:1 block being located at the upper level, and the VA Wenckebach block at the lower level Alternate VA Wenckebach conduction appears as a possible cause of variation in atrial depolarization intervals during ventricular tachycardias with short cycle lengths.
PACTOT: A Reprogrammable Software Pacing System
Authors: DASSEN WILLEM R. M. , VAN DER STELD ALBERT , VAN BRAAM WILLIAM , DEN DULK KAREL , GORGELS ANTON P. M. , BRUGADA PEDRO , WELLENS HEIN J. J.
Published: July 2006

The long battery life in modern pacemakers has created the need for pacemakers in which all the parameters can be changed and updated. The availability of such a system has potential advantages: new pacing techniques can be programmed without reoperation; the number of different pacemaker systems in stock in a hospital can be reduced to this reprogrammable unit; and, finally, this system can be of great help in designing and evaluating new pacing strategies.
The Use of Exercise Testing in Children to Evaluate Abnormalities of Pacemaker Function not Apparent at Rest
Authors: BRICKER J. TIMOTHY , GARSON ARTHUR , TRAWEEK MALINDA S. , SMITH RICHARD T. , WARD KENT A. , VARGO THOMAS A. , GILLETTE PAUL C.
Published: July 2006

The purpose of this study was to evaluate the use of exercise testing in identifying abnormalities of pacemaker function and in confirming set parameters not apparent at rest in children with implanted atrial synchronous physiologic pacemakers. Maximal exercise tests were performed on 24 children (15 boys, 9 girls) from 4.5 to 18 years of age (median =15) with physiologic pacemakers. The lower rule limit was observed before or following testing in 19 of 24 cases. In each case this correlated with the set lower rate limit. The upper rate limit was readied in 10 of 24 cases and was found to be lower than that programmed in one case in which a long atrial refractory period had limited the upper rate limit. Six children reached the maximum upper rate limit to which their pacemaker could be programmed. No abnormalities of atrial capture or ventricular capture occurred during exercise testing. Ventricular sensing was normal in each case. Atrial sensing was observed to be normal in 15 of the 24 cases. Two patients had decreased atrial sensing with exercise. Reversion to the “noise rate” due to myopotential inhibition was found in seven other cases. Subsequent tests on two of these children showed normal sensing. We conclude that: (1) maximal exercise testing identifies aspects of pacemaker function not apparent at rest; decreased atrial sensing and myopotential inhibition are the problems most commonly observed; (2) maximal exercise testing is of value in confirming programmed pacemaker parameters in a population of children with physiologic pacemakers; and (3) because six children reached the maximum upper rate limit of the pacemaker, higher upper rate limits than those currently available may be optimal for pacing in children. Exercise testing is recommended in follow‐up of the child with a physiologic pacemaker.
Pullout His Bundle/Electrophysiologic Studies Using Leads Previously Inserted Via the Subclavian Vein
Authors: FISHER JOHN D.
Published: July 2006

Conventional electrophysiologic studies involve the insertion of several catheter electrodes, positioned to pace and record from the high right atrium. His bundle region, and the right ventricular apex. The present study was undertaken to determine whether similar information could be obtained during removal of temporary pacing leads previously inserted via the subclavian vein, without the need for further invasive studies. Attempts to record a His bundle potential were successful in 157 of 200 patients (79%). A His bundle potential could be recorded during low right atrial pacing on 24 of 58 attempts. The Wenckebach cyle length was compared during high and low right atrial pacing in 34 patients, and did not differ significantly. Ventricular stimulation from the right ventricular apex and right ventricular inflow tract could be performed for assessment of ventricular vulnerability. Similarly, high right atrial pacing for sinus node testing was readily accomplished. In conclusion, detailed electrophysiologic studies can be performed during termination of temporary pacing, in sufficient detail to provide results equivalent to those of a more formal study.
Reliability of the Evoked Response in Determining the Paced Ventricular Rate and Performance of the QT or Rate Responsive (TX) Pacemaker
Authors: FANANAPAZIR LAMEH , RADEMAKER MARIUS , BENNETT DAVID H.
Published: July 2006

The TX pacemaker uses a conventional transvenous electrode to sense T‐waves of paced ventricular complexes and it adapts the pacing rate to varying physioiogical demands by responding to changes in the QT or, more correctly, the stimulus artifact‐to‐T‐wave (stimulus‐T) interval. This pacing system was assessed in 13 patients. The relation between heart rate and stimulus‐T interval and the effect of programming on the performance of this pacemaker were studied on several occasions in each patient. Treadmill exercise performance during TX pacing mode was compared with atrial synchronized ventricular (VAT) and asynchronous ventricular demand (VOO and VVI—70 beats per minute) pacing modes. T‐wave sensing problems arose in three patients. In one. this was overcome by reducing the pulse amplitude from 5.0 to 2.5 V. In another patient, spontaneous recovery of T‐wave sensing occurred 5 months after pacemaker implantation. T‐wave sensing deteriorated with the passage of time in most patients. Satisfactory rate response as assessed by treadmill exercise testing and Holter monitoring was achieved in 12 patients through adjustments of two programmable parameters: the slope that defines the alteration in heart rate in response to a millisecond change in stimulus‐T interval and the “sensing window” that is the interval during which T‐waves can be sensed and a rate response is possible. Exercise performance was significantly better during rate responsive pacing (TX) mode as compared with VVI pacing but was comparable to that during VAT pacing. The resting heart rate/stimulus‐T interval can be described by the following linear regression equation; stimulus‐T interval = 466 – 1.68 × paced‐rate, r2=–0.62. This relation, however, was subject to wide inter‐ and intra‐patient variation. Consequently, given identical programmed parameters and exercise protocol, the chronotropic response differed significantly from patient to patient and in the same patient from one occasion to another. Our results show that a physiologically beneficial chronotropic response can be achieved in most patients. However, reprogramming, based on results of exercise tests and Holter monitoring, may be necessary to adjust for changes in T‐wave sensing and the heart rate/stimulus‐T interval relation and, thus to ensure that the pacemaker continues to function optimally.
Permanent Cardiac Pacing After Open Heart Surgery: Congenital Heart Disease
Authors: GOLDMAN BERNARD S. , WILLIAMS WILLIAM G. , HILL TALLY , R.N.  , HESSLEIN PETER S. , McLAUGHLIN PETER R. , TRUSLER GEORGE A. , BAIRD RONALD J.
Published: July 2006

A retrospective review of 6,004 patients who underwent open repair of congenital heart defects revealed that 132 patients (2.2%) required permanent cardiac pacing postoperative/y. The indications for pacing were early atrioventricular (AV) block in 55%, late onset AV block in 31%, and sick sinus syndrome in 34%. A ventricular septal defect (VSD) was the most common congenital anomaly present alone or in association with other lesions in 67% of the patients. Atrial surgery accounted for 21% of the patients requiring pacing. Ten‐year patient survival was found to be 66% (± 6%). Thirty‐five percent of the deaths were sudden and unexpected, presumably due to an arrhythmia. Reoperation for pacing system failure has occurred too frequently (12% per year). The most common causes for reoperation were battery failure (44%) and exit block (25%).
Frequent Attacks of Supraventricular Tachycardia in a Patient Treated with an Automatic Scanning Pacemaker (PASAR): Holter Documentation of 554 Episodes
Authors: SIMONSEN ERIK , FABRICIUS JØRGEN
Published: July 2006

A 68‐year‐old woman suffering from frequent attacks of supraventricular tachycardia received an implantable, automatic scanning pacemaker for tachycardia termination (PASAR). Electrophysiological study had shown the mechanism to be atrioventricular reentry with retrograde conduction through a concealed bypass tract. During 1 year of follow‐up, a total of twenty‐one 24‐hour Holter recordings documented 554 episodes of tachycardia. In spite of marked fluctuation in tachycardia rate from 135 to 195 bpm and a considerable variation in diurnal pattern of onset of episodes, a clinical improvement resulted. Previous episodes of tachycardia had been isolated and of longer duration. Following implantation, an unexpected observation was made of numerous episodes of supraventricular tachycardia confined to periods lasting up to several hours. This pattern seemed to result from the efficacy of tachycardia termination combined with a continued presence of factors responsible for initiation of tachycardia.
Emergency Defibrillation Using a Temporary Pacing Electrode Catheter
Authors: MANN DAVID E. , INOUYE ISAO KENNETH , SAKUN VALERIE , PICKETT DWAYNE , LUCK JERRY C. , WYNDHAM CHRISTOPHER R. C.
Published: July 2006

Direct application of electrical current to the heart utilizing special equipment such as implantable defibrillators or specially designed catheters has been useful in patients with recurrent ventricular tachyarrhythmias. We describe a patient who developed intractable ventricular fibrillation (VF) during the course of electrophysiologic testing. VF continued for 50 minutes, during which time multiple transthoracic shocks of 360 joules failed to convert the arrhythmia, intracardiac shocks were then delivered via a transvenous 6 French standard quadripolar pacing catheter positioned in the right ventricular apex by direct application of the defibrillator paddle to the catheter, with the patient lying on the posterior paddle. Energy of up to 300 joules failed to defibrillate the patient, but use of 360 joules delivered in this fashion defibrillated the patient twice. Despite the protracted time of cardiac arrest, the patient recovered without sequelae. We report this case to demonstrate that VF refractory to transthoracic defibrillation may be converted by intracardiac shocks using a temporary pacing catheter without special equipment.
Pacemaker Malfunction Simulated by Amplifier Saturation
Authors: MURDOCK DAVID K. , MORAN JOHN F. , HWANG MING H. , EN PIAO ZHEN , SCANLON PATRIGK J.
Published: July 2006

In this case report, pacemaker malfunction is simulated by prolonged pauses after each pacemaker discharge. The pauses were due to saturation of the input of the telemetry monitor amplifier by the discharge voltage of the pacemaker. It is important to recognize amplifier saturation as a form of artifact that can mimic pacemaker malfunction.
Inhibition of a Physiologic Pacing System Due to its Anti‐Pacemaker‐Mediated Tachycardia Mode
Authors: SATLER LOWELL F. , RACKLEY CHARLES E. , PEARLE DAVID L. , FLETCHER ROSS D. , DEL NEGRO ALBERT A.
Published: July 2006

Newer programmable DDD pacemakers prevent pacemaker‐medialed tachycardia by automatic extension of the atrial refractory period after a detected premature ventricular contraction. We present an example in which the automatic extension of the atrial refractory period resulted in pacemaker inhibition, which should not automatically be assumed to represent pacemaker malfunction. A careful understanding of pacemaker timing intervals may allow for identification and correction of this problem.
Effect of Transvenous Atrioventricular Nodal Ablation on the Function of Implanted Pacemakers
Authors: BOWES ROBERT J. , BENNETT DAVID H.
Published: July 2006

We report on seven patients with implanted pacemakers who underwent transvenous ablation of the atrioventricular junction using direct current shocks of 200 to 350 joules. Pacemaker impulse duration and rate were unaffected, but one rate responsive (TX) pacemaker was reprogrammed by a 300‐joule shock. Transient increases in stimulation threshold did occur in two patients, and exit block for 2–15 seconds developed on four occasions. Chronic stimulation thresholds were unaffected. We conclude that it is preferable to carry out ablation before pacemaker implantation, but it is possible to perform transvenous ablation of the atrioventricular junction without damage to an implanted pacemaker; however, a transient rise in stimulation threshold or even exit block may occur, and pacemaker function should be carefully assessed after the procedure.
An Investigation into the Electrical Ablation Technique and a Method of Electrode Assessment
Authors: BOYD EDWARD G.C.A. , HOLT PHYLLIS M.
Published: July 2006

Ablative techniques, using standard defibrillalors and commonly available cardiac catheters, have been applied to the His bundle and bypass tracts for the management of arrhythmias. We have done in vitro studies of the physical effects of these high energy electrical impulses delivered via different pacing electrodes. Unipolar impulses of 10 to 400 joules were delivered via three U.S.C.I. bipolar electrodes and three Vitatron Helifix electrodes immersed in Ringer's solution. The effects were recorded on 35 mm still film, video tape, and high speed cine film. Pressure, voltage, and current were measured. The U.S.C.L bipolar electrodes and the Vitatron Helifix electrodes safely withstood repeated delivery of 400‐Joule impulses which produced similar flash shapes. Each took the form of an incandescent, spherical “fire‐ball” centered around the exposed electrode surface. The mean diameters of the “fire‐baH” for 10 to 400 J using the U.S.C.I. electrodes were 5–24 mm and 3–20 mm for the Helifix catheter electrodes. Peak pressure excursions of over an atmosphere were observed 3 cm from the electrode tips. Higher pressures, lower voltages, and larger currents occurred using the U.S.C.I. pacing lead. The simple. 35 mm time exposure technique showed that at low energies the flashes appeored to emerge in a retrograde manner from the U.S.C.I, catheters and more distally from the Helifrx electrode. This suggested that the latter might be more elective with lower energy impulses. It is concluded that lower energies should be used to take full advantage of the active fixation electrode.
Two False‐negative Responses to the Ajmaline Test in the Wolff‐Parkinson‐White Syndrome
Authors: CAVALLI AUGUSTO , MAGGIONI ALDO , TUSA MAURIZIO , VOLPI ALBERTO
Published: July 2006

Anterograde block in the accessory pathway with a short effective refractory period was observed after intravenous (IV) injection of 1 mg/kg of ajmaline in two patients with the Wolff‐Parkinson‐White syndrome. The possibility of a false‐negative response to this test is discussed. Ajmaline is proposed as an emergency drug in the Wolff‐Parkinson‐White syndrome in the setting of atrial fibrillation with a very high ventricular rate.
Valsalva‐Induced Variations in the Intracardiac Signal
Authors: ROSENQVIST M. , LAGERGREN H. , STRANDBERG H. , EDHAG O.
Published: July 2006

Variations in the intracardiac signal may substantially effect the sensing function of cardiac pacemakers. As the Valsalva maneuver causes a change in heart volume, its effect on the intracardiac signal was studied in seven patients with an adequate escape rhythm who had permanent ventricular pacemakers. During generator replacement, they were asked to perform a standardized Valsalva maneuver. An increase from the baseline amplitude ranging from 5% to 70% was noted during forced expiration against the closed glottis. There was a decrease from the baseline ranging from 15% to 50% after terminafion of this maneuver. Similar changes were noted for the rate of voltage change (slew rate). The magnitude of these alterations was most pronounced in patients with comparatively low intracardiac amplitudes. Because marked changes in the intracardiac signal can result from the Valsalva maneuver, it might be an important source of undersensing among patients with permanent pacemakers.
Osteomyelitis of the First Rib Presenting as a Cold Abscess Nine Months After Subclavian Venous Catheterization
Authors: ROSENFELD LYNDA E.
Published: July 2006

.Percutaneous subclavian catheterization has been associated with numerous complications inciuding osteomyelitis of the clavicle and slernodavicular joint. We report a case of stophylococcal aureus osteomyelitis of the first rib associated with subclavian vein catheterization performed for temporary right ventricular pacing. This case is unusual because of its involvement of the first rib, its late development. and its presentation as a cold chest wall mass.
Mechanically Mediated Pacemaker Pseudomalfunction
Authors: MASSUMI RASHID A. , BEESON CHARLES R. , UDHOJI VASANT N. , BERSOHN MALCOLM M. , USSELMAN LEO B.
Published: July 2006

A case is described of pacemaker pseudomalfunction caused by intermittent displacement of the ventricular lead. The displacement was shown to be caused by critically timed atrial contractions, dislodging the looped ventricular lead, and resulting in intermittent failure to stimulate the heart.
“Incessant” Atrioventricular (AV) Reciprocating Tachycardia Utilizing Left Lateral AV Bypass Pathway with a Long Retrograde Conduction Time
Authors: OKUMURA KEN , HENTHORN RICHARD W. , EPSTEIN ANDREW E. , PLUMB VANCE J. , WALDO ALBERT L.
Published: July 2006

Two patients with incessant or nearly incessant episodes of atrioventricular (AV) reciprocating tachycardia were studied and were found to be unique because of the location of a slowly conducting retrograde AV bypass pathway in the left lateral position. During the tachycardia in both patients, negative P waves were present not only in ECG leads II, III, and aVF. but also in leads I and aVL. The R‐P/P‐R ratios were 1.3 and 1.9, respectively. Cardiac electrophysiologic study revealed that in both tachycardias, retrograde ventriculoatrial conduction occurred utilizing a concealed left lateral AV bypass pathway with a long conduction time. Verapamil prolonged conduction over the AV bypass pathway in both patients. One patient was successfully treated with oral verapamiL The other patient underwent successful surgical interruption of the AV bypass pathway.
An Analysis of Post‐Pacing R‐R Intervals During Atrial Fibrillation
Authors: MORADY FRED , DICARLO LORENZO A. , KROL RYSZARD B. , DE BUITLEIR MICHAEL , BAERMAN JEFFERY M.
Published: July 2006

Bursls of ventricular pacing at cycle lengths of 350–260 ms were introduced during atrial fibrillation in nine patients, and thepost‐pacing R‐R intervals were compared to the R‐R intervals of spontaneous QRS complexes. In eight of nine patients, the mean post‐pacing R‐R interval was 126–199 ms longer than the mean spontaneous R‐R interval (p < 0.005).

Spontaneous runs of aberrantly conducted supraventricular complexes were recorded during atrial fibrillation in one patient. The meon R‐R interval following the runs of aberrantly conducted supraventricular complexes was significantly longer than the mean R‐R interval of spontaneous narrow QRS complexes (p < 0.001). but not significantly different than the mean post‐pacing R‐R interval.

The findings of this study suggest that the R‐R interval that follows a wide‐complex tachycardia during atrial fibrillation is unlikely to be of value in differentiating ventricular tachycardia from aberrantly conducted supraventricular complexes. Analysis of R‐R intervals that follow bursts of ventricular pacing suggests that there is likely to be considerable overlap between the R‐R intervals that follow runs of ventricular tachycardia and the spontaneous R‐R intervals during atrial fibrillation. Furthermore, even when the post tachycardia R‐R interval clearly exceeds the longest spontaneous R‐R interval during atrial fibrillation, this is still of little diagnostic value, because a long pause may occur after either a run of ventricular tachycardia or a run of aberrantly conducted QRS complexes of supraventricular origin.
Transvenous Atrial Pacing in the Management of Sick Sinus Syndrome Following Surgical Treatment of the Univentricular Heart: Case Report and Review
Authors: VINCE DENNIS J. , TYERS G. FRANK O. , KERR CHARLES R.
Published: July 2006

An 11‐year‐old boy with univentricular heart type A‐III underwent surgical treatment at age 10 with a modified Fontan operation. Six months postoperatively he developed intermittent periods of cyanosis and fatigue associated with profound sinus bradycardia and nodal escape. After demonstrating normal atrioventricular conduction, a transvenous atrial pacemaker was implanted. This produced a marked clinical improvement. Transvenous atrial pacing is a satisfactory method of treating sinus node dysfunction in patients with univentricular heart following the Fontan operation provided that there is normal AV conduction.
Verapamil in Idiopathic Ventricular Tachycardia of Right Bundle Branch Block Morphology: Observations During Electrophysiologic and Exercise Testing
Authors: SETHI KAMAL K. , MANOHARAN S. , MOHAN JAGDISH C. , GUPTA M.P.
Published: July 2006

Electrophysiologic studies before and after administration of verapamil were performed in three young patients with recurrent sustained ventricular tachycardia (VT) of right bundle branch block morphology. VT was not provoked by maximal treadmill testing in any patient. Electrophysiologic findings at induction of VT suggested reentry in the first patient and triggered automaticity in the second. Findings were inconclusive in the third patient. Intravenous verapamil terminated the VT in all the three cases. Oral verapamil prevented laboratory induction of sustained VT in the latter two patients. However, VT could be provoked during exercise in both while on oral verapamil therapy. These findings suggest that different mechanisms may underlie ventricular tachycardia dependent upon slow‐response tissue; the role of oral verapamil in the treatment of such VT needs further investigation.
Spontaneous Termination of Paroxysmal Supraventricular Tachycardia Following Disappearance of Bundle Branch Block Ipsilateral to a Concealed Atrioventricular Accessory Pathway: The Role of Autonomic Tone in Tachycardia Diagnosis
Authors: WAXMAN MENASHE B. , CUPPS CHRISTINA L.
Published: July 2006

We present a case of an 18‐year‐old man with a history of palpitations in whom episodes of paroxysmal supraventricular tachycardia were easily initiated by administered atrial premature beats. In all 15 control episodes of tachycardia, functional left bundle branch block (LBBB) seen at the onset, resolved within 10–20 cycles (mean, 13.1 ± 0.95). The tachycardia ended with the normalized QRS complex in each episode. Eleven episodes ended because of block within the antegrade pathway (ended with a P‐wave), and four episodes stopped because of block within the retrograde pathway (ended without a P‐wave). During the administration of isoproterenol (1 mg/min IV) all six episodes of tachycardia had LBBB but these did not end when LBBB disappeared spontaneously. When LBBB subsided, the mean tachycardia cycle interval shortened from 328.5 ± 1.4 to 264.2 ± 2.1 ms (p < 0.001). Each episode of tachycardia was then terminated by carotid sinus massage. The disappearance of LBBB in control conditions presented the retrograde and antegrade limbs of the reentrant circuit with an early impulse that stopped the tachycardia. After isoproterenol adminstration, the tachycardia did not end following disappearance of LBBB, thus enabling the tachycardia cycle interval to shorten by a mean of 64.3 ± 1.9 ms. This extent of tachycardia acceleration is diagnostic of the participation of a concealed, left free‐wall bypass tract.
Differentiation of Sinus Tachycardia from Paroxysmal 1:1 Tachycardias Using Single Late Diastolic Atrial Extrastimuli
Authors: MUNKENBECK FRANCES C. , BUMP THOMAS E. , ARZBAECHER ROBERT C.
Published: July 2006

. Existing antitachycardia devices do not discriminate perfectly between sinus tachycardia and paroxysmal tachycardias with 1:1 atrioventricular relationship (paroxysmal 1:1 tachycardias). The present study tested the hypothesis that the nature of the ventricular response to atrial extrastimulation might distinguish between sinus tachycardia and selected paroxysmal 1:1 tachycardias. In 15 patients, atrial extrastimuli were delivered during sinus tachycardia and in 13 patients during various types of paroxysmal 1:1 tachycardia, and the timing of the next ventricular beat was measured. During sinus tachycardia, in 14 of 15 patients, atrial extrastimuli which were, in turn, early by 80 and 100 ms made the next ventricular beat premature by at least 30 and 50 ms, respectively. In all 13 patients, during paroxysmal 1:1 tachycardia, atrial extrastimuli that were early by 80 and 100 ms failed to make the next ventricular beat premature by more than 10 ms. Single atrial extrastimuli that were premature by less than or equal to 100 ms did not provoke faster tachycardias in any of the patients. In this study, a technique that used single late extrastimuli during tachycardia safely distinguished sinus tachycardia from paroxysmal tachycardias. This technique might be suitable for incorporation into an antitachycardia device. Further investigation of this technique is warranted in a larger number of patients with a wider variety of tachycardias.
Attempted Entrainment of Circus Movement Tachycardias by Ventricular Stimulation
Authors: SAOUDI NADIR C. , CASTELLANOS AGUSTIN , ZAMAN LIAQAT , PORTILLO BOLIVAR , SCHWARTZ ALAN , MYERBURG ROBERT J.
Published: July 2006

. Entrainment was attempted while pacing the right ventricle in 12 patients with circus movement tachycardias. At the onset of stimulation eight patients had short episodes of intraventricular and atrioventricular dissociation during which the paced impulses activated the various ventricular recording sites (right and left), but did not reach the atria. The latter occurred because the ventricular olectrograms were recorded from parts of the ventricles which were not essential components of the reentry circuit. Relatively long (greater than 5 s) runs of entrainment were not possible in any case because of the relatively prompt termination of the tachycardias. Whereas in three patients this was due to the abrupt appearance of retrograde block in the accessory pathway, in nine patients it happened when the sequential, anterograde and retrograde, penetration of the AV node resulted in AV nodal block of the subsequent, reentering atrial impulse. The findings in this study showed that, with the methodology used, entrainment of circus movement tachycardias by ventricular stimulation had to be defined conceptually, by the fulfillment of requirements which did not include its occurrence for at least 5 seconds. Furthermore, the results also suggested that entrainment and tachycardia termination were best demonstrated by a technique which allowed the emission of the first stimulus in a constant (late) moment of the cycle, with deliverance of one additional stimulus at the same cycle length in successive pacing runs.
Tachycardia Mediated by an AV Universal (DDD) Pacemaker Triggered by a Ventricular Depolarization
Authors: PIMENTA JOÃO , SOLDÁ ROBERTO , PEREIRA CARLOS BRITTO
Published: July 2006

A 44‐year‐old female had Chagas’ disease with right bundle branch block, right axis deviation, and ventricular ectopic beats. An invasive evaluation showed a prolonged HV interval of 100 ms. A Medtronic Versatrax 7000 was implanted, after which a pacemaker‐mediated tachycardia was observed. The esophageal lead ruled out the possibility of an atrial triggered tachycardia. The diagnosis was pacemaker‐mediated tachycardia due to abnormal sensing of the terminal forces of the ventricular activation because of malposition of the atrial lead in the right ventricular out‐flow tract.
The QT‐Sensitive Cybernetic Pacemaker: A New Role for an Old Parameter?
Authors: PUDDU PAOLO E. , TORRESANI JEAN
Published: July 2006

A critical review of the available data on QT interval is presented to delineate techniques useful to the development of a QT‐sensitive cybernetic pacemaker. The reason for the development of this unit stems from the ability of QT prolongation to predict the onset of life‐threatening ventricular arrhythmias in some clinical situations; the QT interval is physiologically related to the cardiac cycle length, therefore providing adequate information to drive both ventricuiar and atrioventricuiar sequential rate‐responsive pacemakers. This unit might also monitor cardiac rhythm and detect the pathophysioiogic precursors of advanced grades of ventricular arrhythmias. A therapeutic role, both pharmacologic and electrical, may also be possible in the future. Integration of these concepts and cooperation between interested physicians, technicians and manufactors will be necessary to produce such a unit at a low cost‐benefit ratio. The potential clinical application of this pacemaker deserves attention for the prophylaxis and treatment of sudden arrhythmic death.
Augmentation of Cardiac Output by External Cardiac Pacing: Pacemaker‐Induced CPR
Authors: MURDOCK DAVID K. , MORAN JOHN F. , SPERANZA DAVID , LOEB HENRY S. , SCANLON PATRICK J.
Published: July 2006

Transthoracic cardiac pacing is frequently associated with simultaneous stimulation of skeletal muscle and nerves. We describe a patient in cardiogenic shock and complete heart block in whom the associated vigorous abdominal and chest muscle contractions caused by transthoracic cardiac pacing resulted in a marked augmentation of cardiac output and systemic blood pressure via a “CPR” effect
Time Course of Transvenous Pacemaker Stimulation Impedance, Capture Threshold, and Electrogram Amplitude
Authors: PLATIA EDWARD V. , BRINKER JEFFREY A.
Published: July 2006

To examine the time course of atrial and ventricular stimulation impedance, capture threshold, and electrogram amplitude, we obtained noninvasive telemetric data in 63 patients who underwent implantation of unipolar, endocardial pacing leads and a second‐generation dual chamber pacemaker with expanded bidirectional telemetry, including stimulation impedance, endocardial electrograms, and automatic capture threshold determination. On follow‐up of 9–20 months [mean, 15 months], all but six patients continued to pace in the DDD mode. To validate measurements made with telemetry, invasive measurements made directly with a pacing system analyzer at time of implant were compared with immediate postimplant telemetric measurements. Significant correlation of acute stimulation impedance was noted in both atrial (r = .7, p < .001) and ventricular (r = .8, p < .001) lead systems. The atrial stimulation impedance decreased from 538 ohms at implant to 471 ohms at 13 months (p < .01); the ventricular stimulation impedance similarly declined from 545 ohms to 485 ohms at 13 months (p < .0l). Capture thresholds peaked at one month, then declined: atrial, 1.2 V at implant vs 2.2 V at 1 month (p < .008) and 1.4 V at 13 months; ventricular, 1.1 V at implant vs 1.9 V at 1 month (p < .001) and 1.3 V at 13 months. There were no significant changes noted in atrial or ventricular electrogram amplitude following implantation.

We conclude that there is close correlation of invasive recordings with those made telemefrically with this pacemaker at time of implant. Chronic atrial and ventricular stimulation impedances gradually decline for at least one year following implant, while electrogram amplitude in both chambers remains unchanged. Atrial and ventricular capture thresholds increase within one month after implant and thereafter decline for at least one year, but not to implant levels. Expanded bidirectional telemetry with such second‐generation units allows more precise and efficacious long‐term appraisal of the pacemaker‐myocardium interface.
Effects of Antiarrhythmic Drugs on the Chronic Pacing Threshold and the Endocardial R Wave Amplitude in the Conscious Dog
Authors: HUANG SHOEI K. , HEDBERG PETER S. , MARCUS FRANK I.
Published: July 2006

To determine the effects of antiarrhythmic drugs on the chronic pacing threshold and the endocardial R wave amplitude, we tested seven drugs (representative of Vaughn Williams' antiarrhythmic class I‐IV) on four to six dogs after the implanted ventricular endocardial bipolar leads had reached chronic stable thresholds. The seven antiarrhythmic drugs tested were procainamide (oral [p.o.] and intravenous [IV], class IA), lidocaine (IV, class IB), tocainide (p.o., class IB), flecainide (p.o. and IV, class IC), propranolol (p.o. and IV, class II), amiodarone (p.o. and IV, class III), and verapamil (p.o. and IV, class IV). The drugs were administered in sufficient doses to achieve plasma levels associated with antiarrhythmic efficacy in humans. All oral drugs were given for sufficient time to achieve expected steady state levels. The pacing thresholds, both voltage and current, and the endocardial R wave amplitude were measured in the conscious dog with a Medtronic pacing system analyzer at a pulse width of 0.1, 0.5, 1.0, and 2.0 ms at intervals following IV or p.o. administration of each antiarrhythmic drug. We found that there were no significant effects of any of the tested seven antiarrhythmic drugs on the chronic pacing threshold and the endocardial R wave amplitude at any of the pulse widths. We conclude that in the healthy dog antiarrhythmic drugs do not alter the pacing threshold and the endocardial R wave amplitude.
Comparative Efficacy of Continuous and Pulsed Argon Laser Ablation of Human Diseased Ventricle
Authors: CICCONE JOHN , SAKSENA SANJEEV , PANTOPOULOS DEMETRIS
Published: July 2006

We compared the tissue lesions obtained in a saline medium using single continuous argon laser discharges with paired sequential continuous laser discharges in nine segments of diseased human ventricle resected from patients with and without ventricular tachycardia (VT) at cardiac surgery. Single continuous argon laser discharges were delivered to separate sites on the endocardial surface of the tissue segments for periods of 10, 20, and 30 seconds at laser beam power of 5 W (group IA) and 8 W (group IIA). Paired sequential argon laser discharges of 5, 10, and 15 seconds in duration were delivered to separate sites at a laser power of 5 W (group IB) and 8 W (group IIB). Gross and microscopic examination of each tissue lesion and its dimensions were performed.

Laser irradiation of excised human ventricle resulted in a circular discrete burn at the site of application. Histologic examination showed crater formation due to tissue vaporization with the crater lining consisting of charred tissue and a zone of coagulation necrosis. Analysis of lesion dimensions in groups IA and IIA showed comparable lesion depth and diameter with single continuous and paired sequential laser discharges at energies of 50 J (p > .2), 100 J (p > .2), and 150 J (p > .2). Similarly, lesion depth and diameter were comparable in groups IB and IIB at the same energies. We conclude that paired sequential argon laser discharges may be used to produce comparable tissue lesions to single continuous argon laser discharges in diseased human ventricle.
Alternating Wenckebach Periods in Acute Inferior Myocardial Infarction: Clinical, Electrocardiographic, and Therapeutic Characterization
Authors: LEWIN RUBEN F. , KUSNIEC JAIRO , SCLAROVSKY SAMUEL , STRASBERG BORIS , ARDITTI ALEXANDER , PINCHAS AVRAHAM , AGMON JACOB
Published: July 2006

We report on twelve patients with alternating Wenckebach periods (AWP) occurring during an acute inferior myocardial infarction (AIMI). There were nine males and three females, with a mean age of 61 years (range, 43 to 75). AWP appeared during the first 48 hours of the AIMI in 10 patients and on the fourth day of hospitalization in two patients. AWP occurred spontaneously in nine patients and following the administration of atropine in the remaining three patients. Mean systolic blood pressure significantly decreased during AWP as compared to the period preceding or following the bradyarrhythmia (93 ± 42 mmHg vs 123 ± 37 mmHg, p < 0.02). Killip functional class was significantly higher during AWP as compared to the period preceding or following the bradyarrhythmia (2.1 ± 1.2 vs 1.5 ± 0.8, p < 0.02). Pacemaker therapy was initiated prophylactically in two patients, because of syncope in six, because of hemodynamic deterioration in two, and for syncope and hemodynamic deterioration in two. Three patients died in cardiogenic shock despite pacemaker therapy. No evidence of right ventricular infarction was seen in the patients.

Atropine administration during AWP significantly increased the sinus rate and significantly decreased the ventricular rates and the systolic blood pressure. In addition, three patients developed long bouts of paroxysmal AV block. Isoproterenol administration improved AV conduction in one patient, caused no change in two patients and induced non‐sustained ventricular tachycardia in three patients.

In conclusion, AWP occurring during AIMI is a symptomatic bradyarrhythmia associated with hemodynamic deterioration. Drug therapy for this bradyarrhythmia is usually ineffective and sometimes paradoxical responses are observed. Pacemaker therapy is usually needed to correct symptoms and the worsening hemodynamic status. We recommend prophylactic pacemaker implantation in patients developing AWP during AIMI.
Totally Implantable Spinal Cord Stimulation for Chronic Pain: Design and Efficacy
Authors: SHATIN DEBORAH , MULLETT KEITH , HULTS GERALD
Published: July 2006

Neurostimulators used to treat chronic, intractable pain have evolved from technical developments in pacemaker technology. A totally implantable spinal cord stimulation (SCS) system* was designed based on elements of a widely used cardiac pacemaker.** This paper reports on the transformation of pacemaker technology for neurostimulation applications and presents results of using this system for the treatment of 90 patients with chronic, intractable pain of the low back and/or legs. Significant reduction in pain levels resulted from use of a totally implantable spinal cord stimulation system. Seventy percent of the patients experienced good or excellent pain relief at an average of 14.5 months after implant. Patients who used an automatic ON/OFF cycling mode of stimulation reported greater pain relief than patients who were stimulated continuously.
Noninvasive Serial Electrophysiological Testing Using an Implanted Pacemaker for Management of Recurrent Ventricular Tachycardia
Authors: MENOZZI CARLO , BRIGNOLE MICHELE , MONDUCCI IGOR , LOLLI GINO
Published: July 2006

An implanted multiprogrammable pacemaker capable of performing both premature and burst stimulation can be teamed with a special external programmer for noninvasive electrophysiological testing. Such studies, combined with indications from provocative pharmacologic tests, allowed us to formulate effective antiarrhythmic therapies for three patients suffering from post‐infarction, recurrent sustained ventricular tachycardia.