bluuebunny/crossref_metadata_2025 huggingface dataset:
Clinical, Electrophysiological, and Histopathological Observations in Supraventricular Tachycardia
Authors: KOBAYASHI YOUICHI , YAZAWA TAKASHI , BABA TAKAO , MUKAI HIDEYUKI , INOUE SHIN , TAKEYAMA YOUICHI , NIITANI HIROKAZU
Published: July 2006

Fifty patients with supra ventricular tachycardia (SVT) underwent clinical electrophysiological studies (EPS), endomyocardial biopsies und cardiac catheterizations. EPS revealed AV nodal reentrant tachycardia (AVNRT) in seven patients, AV reentrant tachycardia utilizing concealed AV bypass tracts (AVR‐ CBT) in nine patients, AV reentrant tacycardia utilizing AV bypass tracts with ventricular preexcitation (manifest WPW) in 13 patients, sinus nodal or intra‐atrial reentrant tachycardia (SNRT or TART) in three patients, atrial flutter (AF) in nine patients, automatic atrial tachycardia (AAT) in jive patients, and multifocal atrial tachycardia (MAT) in four patients. According to the clinical observations, three patients with AVNRT (43%), six with AVH‐CBT (67%), six with manifest WPW (46%), two with SNRT or IART (67%), eight with AF (89%), two with AAT (40%), and two with MAT (50%) showed other accompanying clinical abnormalities. In all patients who were studied histologically, changes in the myocardium were seen; myocarditic changes, postmyocarditic changes and nonspecific abnormalities were present in six (12%). 15 (30%), and nine (18%) respectively. Myocardial changes were observed in four out of seven cases with AVNRT (57%), in six out of nine with AVR‐CBT (67%), in five out of 13 with manifest WPW (38%), in two out of three with SNRT or IART (67%), in six out of nine with AF (67%), in all five cases of AAT (100%), and in two out of four with MAT (50%). Nineteen out of 32 without clinical abnormalities except for arrhythmias (59%) had myocardial changes (six had myocarditic changes, ten had postmyocarditic changes, and three had nonspecific abnormalities). On the other hand, nine out of 21 with myocarditic or postmyocarditic changes were accompanied with various arrhythmias other than SVT (two had SSS, five had AV block or rBBB, and two had VT). Elevated LVEDP was present in 36% of the group with normal myocardium and in 53% of the group with myocardial changes. However, the low EF was shown in no patients with normal myocardium but in 21% of the group with myocardial changes. The low CI was also shown in only 9% of the group with normal myocardium but in 28% of the group with myocardial changes. These results suggest that patients with SVT may exhibit several histopathological changes in the myocardium, even in the absence of any clinical organic heart disease.
Reuse of Pacing Catheters: A Survey of Safety and Efficacy
Authors: O'DONOGHUE SUSAN , PLATIA EDWARD V.
Published: July 2006

We surveyed 12 medical centers with regard to the reuse of pacing catheters during electrophysiologic studies. The prevalence of superficial skin infections or bacteremia related to EP studies was extremely low, and was not significantly different in the catheter reuse group compared to the single use group. We conclude that catheter resterilization and reuse is safe and cost‐effective.
Ventricular Tachycardia with Alternating Cycle Lengths: Self‐Entrainment of Parasystolic Rhythm?
Authors: CASTELLANOS AGUSTIN , MENDOZA IVAN J. , SAOUDI NADIR , JALIFE JOSE
Published: July 2006

A patient had ventricular tachycardia with cycle lengths consistently varying between 400 and 490 ms. Arrhythmias with a similar electrocardiographic pattern had been thought to result from the regular activity of an automatic pacemaker with either 3:2 exit block of the Wenckebach type or alternation in exit conduction times. However, the findings in our patient could also be explained by postulating the existence of modulated ventricular parasystole having 3:2 exit block or with alternating (short‐long) exit conduction times. In either case, the action potentials elicited by the parasystole must have reached (with variable delays) the ventricular tissue beyond the zone of protection to produce electrotonic depolarizations which, in turn, were reflected back to the ectopic focus itself. This resulted in runs of 2:3 or 2:2 “self‐entrainment” of the parasystolic pacemaker. Similar phenomena have been produced in biologic and mathematical models of modulated parasystole.
Increased Pacing Threshold After an Automatic Defibrillator Shock in Dogs: Effects of Class I and Class II Antiarrhythmic Drugs
Authors: GUARNIERI THOMAS , DATORRE STEVEN D. , BONDKE HANSJURGEN , BRINKER JEFFREY , MYERS STEVEN , LEVINE JOSEPH H.
Published: July 2006

A high energy shock delivered by an automatic defibrillator may interfere with pacemaker function. To provide insight into the changes that occur in the threshold for ventricular pacing after the shock from an automatic defibrillator, we measured the time to capture during asynchronous ventricular pacing in dogs from endocardial or epicardial sites, after a 30 joule shock was delivered via conventional automatic defibrillator (AICD) patch electrodes. After a 30 joule shock, there was a transient Joss of ventricular capture. The duration of capture loss was related to current strength. During endocardial pacing at threshold current, the time to capture was 4.9 ± 1.2 s, whereas at current values twice threshold the time to capture from endocardial pacing was 2.2 ± 0.9 s. No difference was found between endocardial and epicardial pacing sites in the time to capture. To ascertain the mechanism of capture loss we: (1) examined the effects of converting the pacing catheter to a current sink (transiently shunting to ground); (2) altered excitability by an infusion of flecainide; (3) blocked sympathetic input (propranolol). No change in time to capture was noted by shunting the pacer to ground. After an infusion of flecainide the time to capture from endocardial pacing was significantly prolonged to 14.9 ± 2.2 s at the threshold value (P < .01) and 5.6 ± 2.1 s at twice threshold (P < .05). Conversely, intravenous propranolol had no effect on the time to capture after shock from endocardial pacing. These data indicate that there is a transient increase in pacing threshold after the shock from an automatic defibrillator. The duration of capture Joss is current‐dependent, and can be significantly increased by the presence of a class Ic antiarrhythmic drug.
Sudden Bradyarrhythmic Death in Dilated Cardiomyopathy: A Case Report
Authors: RADHAKRISHNAN S. , KAUL U. , BAHL V.K. , TALWAR K.K. , BHATIA M.L.
Published: July 2006

An 18‐year‐old male presented with biventricular failure and atrial fibrillation. Detailed investigations revealed the diagnosis of dilated cardiomyopathy. He was put on medical treatment which resulted in symptomatic improvement. One year later he presented with 2 episodes of syncope, with no change in the routine electrocardiogram. A 24‐hour ambulatory monitoring was done. The patient died suddenly while on the monitor. Analysis of the terminal event revealed a sudden complete heart block followed by asystole, an event described very rarely in the published literature.
Discrimination of Anterograde From Retrograde Atrial Electrograms for Physiologic Pacing
Authors: TIMMIS GERALD C. , WESTVEER DOUGLAS C. , BAKALYAR DONOVAN M. , PUGSLEY THOMAS J. , STEWART JAMES R. , GORDON SEYMOUR
Published: July 2006

The morphology of bipolar electrograms recorded in the right atrium was examined in nine patients in an attempt to discriminate retrograde from anterograde atrial signals to an extent that would be useful for physiologic pacing. Peak‐to‐peak amplitude, duration, √energy, maximum slew rate, mean slew rate, and polarity were examined in the time domain. Maximum frequency, half‐power frequency, Fourier amplitude peak, and frequency of peak were measured in the frequency domain. There was a significant difference between anterograde and retrograde signals for all variables related to amplitude; these variables are peak‐to‐peak amplitude, √energy, Fourier amplitude peak, maximum slew rate and mean slew rate. In seven of nine patients there was at least one variable sufficiently discriminating to insure reliable detection of anterograde signals while systematically rejecting retrograde signals. However, no individual variable was able to effect this discrimination in more than four patients and at least three variables were needed for all seven patients: maximum frequency, one of either √energy and Fourier amplitude peak, and one of either frequency of peak or half‐power frequency (six possible combinations). Thus, although differences between anterograde and retrograde atrial activity can he demonstrated in most patients, no single parameter displays sufficient discriminating power to facilitate physiologic pacing in patients exhibiting retrograde activity.
Differential Bipolar Sensing of a Dual Chamber Pacemaker
Authors: DE BOER HANS , KOFFLARD MARCEL , SCHOLTES TON , VAN MECHELEN ROB
Published: July 2006

Differential bipolar sensing was evaluated in 10 consecutive patients with symptomatic heart block managed with dual chamber pacing. During pacemaker implantation atrial and ventricular electrograms were recorded using unipolar (L/P) and differential bipolar (DBP) sensing amplifiers. The mean peak‐to‐peak amplitudes of the VP and DBP atrial electrograms were 3.3 ± 1.2 mV and 4.2 ± 1.2 mV, respectively. The difference was statistically significant (p < 0.05). The mean peak‐to‐peak amplitudes of the ventricular electrograms were, respectively, 6.8 ± 1.5 mV and 7.5 ± 1.4 mV (p < 0.01). Within 6 weeks after pacemaker implantation, patients visited the outpatient clinic. Isometric exercise tests were performed during UP and DBP sensing of the pacing system. Myopotential sensing in the ventricle occurred in nine patients during UP sensing and in none of the patients during DBP sensing (p < 0.01) at a sensitivity setting of 0.5 mV. In addition, chest wall stimulation was performed to assess the effects of far‐field signals on the ventricular sensing circuit of the pulse generator. Chest wall stimuli inhibited ventricular output during UP sensing in all 10 patients, whereas during DBP sensing inhibition of the ventricular channel occurred in three patients and then only at high output (>8 V) settings. The susceptibility of the pacing system to crosstalk was also determined. However, neither during UP sensing nor during DBP sensing could cross‐stimulation or cross‐inhibition be demonstrated. In conclusion, DBP sensing is superior to UP sensing in terms of myopotential and far‐field sensing. In addition, statistically significant differences were observed in amplitudes of UP and DBP atrial or UP and DBP ventricular signals. The clinical relevance of the latter finding remains to be assessed.
Electrophysiologic Demonstration of an Atriofascicular Accessory Pathway
Authors: KOU WILLIAM H. , MORADY FRED , DE BUITLEIR MICHAEL , NELSON STEVEN D.
Published: July 2006

Evidence of an atriofascicular accessory pathway has not been reported previously. In the patient presented in this case report, an electrophysiology study demonstrated a constant left bundle branch block QRS configuration despite varying degrees of ventricular preexcitation, in association with a constant atrioventricular interval during incremental atrial pacing and programmed atrial stimulation. The presence of an atrioventricular, nodoventricular, nodofascicular, and atrial‐His accessory pathway was ruled out. The findings are best explained by the presence of an underlying left bundle branch block and an atriofascicular accessory pathway connecting the atrium and right bundle. The atriofascicular accessory pathway was a passive bystander during an atrial tachycardia and was not directly involved in the generation of the tachycardia. To our knowledge, this is the first report of an atriofascicular accessory pathway.
Automatic Implantable Scanning Burst Pacemakers for Recurrent Tachyarrhythmias
Authors: PALAKURTHY PRASAD R. , SLATER DAVID
Published: July 2006

Ninety patients (18 patients with spraventricular tachycardia and 72 patients with ventricular tachycardia) underwent electrophysiological study. Six out of 18 patients with supraventricular tachycardia (33%) and one out of 72 patients with ventricular tachycardia (1.4%) were considered suitable condi‐dates for the scanning pacemaker. However, only six of the seven patients underwent implantation. The seventh patient decided not to undergo implantation and continued to have recurrent episodes of supra‐ventricular tachycardia. The scanning pacemaker delivers extrastimuli at preset initial and coupled delay after four cycles of tachycardia. If tachycardia is not terminated, another set of extrastimuli are delivered with a decrement in the coupling cycle. During the follow‐up period of 7–25 months (mean, 14.3 months), tachycardia cycle lengths and termination windows changed in four patients. The pacemakers in these patients were reprogrammed multiple times (2 to 6 times with a mean of 3.5) as the previous number of extrastimuli and intervals were ineffective in the termination of tachycardias. The major limitations of the extrastimulus pacemaker were: 1) only a small percentage of patients were suitable candidates for its use; (2) the initially selected termination window in the majority of patients was ineffective during the follow‐up period due mainly to the changes in tachycardia cycle length and subsequent termination windows; and (3) the majority (five out of six patients in this series) of patients needed additional pharmacologic therapy to modify their tachycardia rates. However, despite these limitations, the scanning pacemaker may be an additional tool in the management of recurrent tachyarrhythmias in selected patients.
Electrocardiographic Characteristics of Pacing From the Right Atrial Appendage During Atrioventricular Sequential Pacing
Authors: HARDEBECK CHARLES J.
Published: July 2006

In the interpretation of electrocardiograms recorded during atrioventricular sequential pacing, uncertainty frequently arises in the assessment for evidence of atrial capture. In the present study, electrocardiographic characterization of pacing from the right atrial appendage as a component of atrioventricular pacing was performed on tracings obtained from 16 patients with bipolar dual chamber pacing units, and from 18 patients with unipolar dual chamber pacing units in which large overshoot potentials occurred following the atrial pacing spike. Atrial complexes resulting from bipolar pacing of the right atrial appendage were found to be uniformly prolonged and of diminished amplitude compared to those in sinus rhythm; they were also noted to contain sequential inferoposterior and leftward‐posterior component vectors. The exponential overshoot‐decay complex associated with unipolar atrial pacing appeared as a vector directed along the axis from the pulse generator to the pacing lead; the degree to which this deflection interfered with identification of atrial capture in various leads was thus largely dependent on pulse generator location. It was concluded that careful systematic inspection of multiple electrocardiographic leads will generally permit the characteristic features of pacing the right atrial appendage to be recognized, thus facilitating correct interpretation of atrial capture during atrioventricular sequential pacing.
Electrophysiological Evaluation of Sustained Ventricular Tachyarrhythmias in Idiopathic Dilated Cardiomyopathy
Authors: MILNER PETER G. , DIMARCO JOHN P. , LERMAN BRUCE B.
Published: July 2006

Sustained ventricular tachyarrhythmias and sudden death are particularly prevalent in patients with idiopathic dilated cardiomyopathy (IDC). In contrast to patients with ischemic heart disease, the value 0/electrophysiological stimulation (EPSJ in patients with IDC has not yet been established. To clarify the role of EPS in these patients, we studied 19 patients (58 ± 11 years) with IDC who had symptomatic ventricular tachycardia (VT) or ventricular fibrillation (VF). The mean left ventricular ejection fraction was 26 ± 9%. Ten patients had survived out‐of‐hospital cardiac arrest, eight had documented sustained monomorphic VT and one patient had non‐sustained VT associated with syncope. Thirteen of the 19 patients (68%) had their clinical ventricular tachyarrhythmias induced at EPS (12 VT, 1 VF). In nine of 13 patients (69%), the arrhythmias were subsequently suppressed during serial electrophysiological drug testing. During 17 ± 11 months of follow‐up, 10/19 (53%) patients experienced recurrence of their arrhythmias and nine out of 19 (47%) patients died; six died suddenly and three secondary to heart failure. There was no difference in arrhythmia recurrence between patients with and without inducible ventricular tachyarrhythmias at initial study. Furthermore, suppression of arrhythmia during serial testing did not predict outcome; recurrences were observed in jive out of nine patients whose arrhythmias were suppressed. These data indicate that the sensitivity of programmed ventricular stimulation in patients with IDC and symptomatic ventricular tachyarrhythmias is approximately 70%, and that non‐inducibility during control EPS or prevention of arrhythmia induction with antiarrhythmic therapy does not confer long‐term protection against recurrent arrhythmias.
Failure of Elective Replacement Indicator to Predict End‐of‐Life of the Automatic Implantable Cardioverter‐Defibrillator
Authors: EPSTEIN ANDREW E. , SHEPARD RICHARD B. , KIRKLIN JAMES K. , MCGIFFIN DAVID C.
Published: July 2006

A major limitation in the use of the automatic implantable cardioverter‐defibrillator (AICD) is limited battery longevity and the absence of an accurate and precise end‐of‐life indicator. An elective replacement indicator, or ERI, was proposed by the manufacturer of the AICD in 1985. This ERI was evaluated in nine patients with AICDs. The ERI was exceeded at a mean of 10.9 ± 3.0 months after implantation. Although 0.6 ± 0.4 months of battery life were predicted to remain before battery failure, the devices were followed for 6.0 ± 3.8 months (p = 0.002) during which time no device failed. Although 28.9 ± 21.9 seconds of charging time were predicted to remain, 103.5 ± 67.9 seconds were shown to be available by magnet charge time testing (p = 0.01). Thus, the EHI of the AICD, as originally proposed by its manufacturer, consistently underestimated both the predicted time to end‐of‐life as well as the cumulative charging time remaining before end‐of‐life for each AICD examined. We propose that this ERI not be used to predict end‐of‐life of the AICD. A “new” ERI has been recommended.
Techniques and Methods for Catheter Endocardial Fulguration
Authors: FONTAINE G. , CANSELL A. , TONET J.L. , FRANK R. , GALLAIS Y. , ROUGIER I. , GROSGOGEAT Y.
Published: July 2006

Fulguration is a new and promising technique for the treatment of cardiac arrhythmias. This paper discusses the methods and equipment used at Jean Rostand Hospital for invasive experimental research related to fulguration. The importance of catheter testing and selection is demonstrated. The most important features of the measurement techniques for both His bundle and ventricular tachycardia recordings are described. The main components of the protocols for fulguration and early post‐operative surveillance are reported. The ODAM Fulgucor is used, augmented by the incorporation of additional pieces of equipment to allow monitoring of current and voltage curves. An electromechanic relay allows for automatic switching from the recording amplifier to the energy source. The video system used includes recording of the image of the last fluoroscopic event with a character generator and an electronic pointer superimposed (when necessary). Computer programs for appropriate timing of predominant events have been developed.
Long‐Term Outcome Following Programmed Electrical Stimulation in Patients with High‐Grade Ventricular Ectopy
Authors: KHARSA MOHAMED H. , GOLD ROBERT L. , MOORE HAROLD , YAZAKI YOSHIZUMI , HAFFAJEE CHARLES I. , ALPERT JOSEPH S.
Published: July 2006

To determine if programmed electrical stimulation (PES) could be utilized to identify patients with high‐grade ventricular ectopy at low‐ or high‐risk for sudden cardiac death, we performed PES in 40 patients with high‐grade ventricular ectopy reactory to conventional antiarrhythmic agents. Twenty‐one patients had a previous myocardial infarction, five had cardiomyopathy, six had hypertension, three had valvular heart disease and five had no known structural heart disease. The mean age was 50 years (range, 18 to 76). During programmed ventricular stimulation, eight patients had inducible sustained (more than 30 seconds) monomorphic ventricular tachycardia (Group II but in 32 patients sustained ventricular tachycardia was not inducible (Group II). None of the five patients without structural heart disease were inducible while seven out of 21 (33%) patients with previous myocardial infarction had inducible ventricular tachycardia (VT). Antiarrhythmic therapy was instituted in patients with inducible VT; patients without inducible VT did not receive antiarrhythmic agents. In Group I, seven of the eight patients are alive (mean follow‐up, 16 months) and in Group 11, 28 of the 32 patients are alive (mean follow‐up, 17 months). None of the five deaths were sudden. We conclude that in the absence of antiarrhythmic therapy, the incidence of sudden cardiac death is very low in patients with high‐grade ventricular ectopy who do not have inducible monomorphic ventricular tachycardia during programmed ventricular stimulation.
DDD‐Pacemaker Pseudomalfunction During Supraventricular Tachycardia
Authors: FONTAINE JOHN M. , ALMA‐PERRI CARMEN , EL‐SHERIF NABIL
Published: July 2006

Asynchronous pacing during the presence of electromagnetic interference or other sources of “noise” is a protective mechanism available to prevent pacemaker output inhibition. We describe a patient with a DDD pacemaker who had asynchronous dual chamber or noise reversion pacing as a consequence of repetitive signals (QHS complexes) failing into the noise sampling period (NSP) of the pacemaker ventricular refractory period. During supraventricular tachycardia al a rate of 215 bpm, noise reversion mode pacing occurred when QRS complexes were well detected immediately after the termination of a normal pacemaker ventricular refractory period and treated as a premature ventricular depolarization, resulting in automatic refractory period extension. Recycling of this extended refractory period occurred when consecutive QRS complexes were detected during the NSP and forced asynchronous dual chamber pacing at the programmed lower rate. The mechanism is presented and was supported by subthreshold esophageal pacing simulating the tachycadia and initiating the noise reversion response.
Fluoroscopic Technique of Subclavian Venous Puncture for Permanent Pacing: A Safer and Easier Approach
Authors: LAMAS GERVASIO A. , FISH R. DAVID , BRAUNWALD NINA S.
Published: July 2006

Infraclavicular subclavian puncture may be performed with fluoroscopic observation of the needle trajectory. In 92 patients so implanted between July 1985 and May 1987 uneventful venous access was achieved in 90, one was unsuccessful and one patient had subcutaneous emphysema, a complication rate of 2.2%.
Recipient P Wave Synchronized Pacing of the Donor Atrium in a Heart‐Transplanted Patient: A Case Study
Authors: MARKEWITZ ANDREAS , OSTERHOLZER GEORG , WEINHOLD C. , KEMKES BERNHARD M. , FERUGLIO GIORGIO A.
Published: July 2006

We present the case of a 23‐year‐oid patient who underwent orthotopic heart implantation and subsequent implantation of an atrial dual chamber pacemaker. The stimulation rate in the donor atrium is controlled by the recipient's sinus node activity, thereby maintaining AV synchrony and allowing appropriate rate increase during exercise.
Comparative Evaluation of Chronotropic Responses of QT Sensing and Activity Sensing Rate Responsive Pacemakers
Authors: MEHTA DAVENDRA , LAU CHU‐PAK , WARD DAVID E. , CAMM A. JOHN
Published: July 2006

The rate responses of activity sensing (ATS) and QT sensing (QTS) rate responsive pacemakers to different forms and durations of exercises were compared. Nine patients with ATS and five with QTS were studied. All had complete heart block and atrial arrhythmias. At (he onset, (he pacemakers were programmed to achieve a pacing rate of 100–110 bpm by the end of stage 1 of the Bruce protocol, and to a pacing rate range of 70–150 bpm. With progressive exercise, using a treodmill (Bruce protocol), the maximum pacing rates in the two groups were not significantly different (mean ± SD; 123 ± 18 vs 129 ± 23 bpm, ATS vs QTS). The time taken to return to the baseline pacing rate during recovery was significantly longer with QTS (178 ± 70 vs 264 ± 68 s, p < 0.05). Brief exercise tests on a treadmill were performed for 3 min each with different combinations of treadmill speeds (1.2 and 2.5 mph) and gradients (0, 5, 10 and 15%). In both groups of patients, faster walking speed was associated with a faster pacing rate at each gradient. However, with increasing gradients, at each speed, there was a rise in the maximum pacing rate only in patients with QTS. During brief exercise tests, the maximum rate was achieved by the end of exercise in patients with ATS, but was delayed by 33 ± 20 s after exercise in patients with QTS. With very brief exercises lasting less than 1 minute (jogging on the spot), which require immediate rate response, patients with ATS had a rapid rate response and the maximum pacing rates were achieved by the end of the activities. The response of QTS was delayed and maximum pacing rate occurred during recovery. Ascending and descending four flights of stairs resulted in similar pacing rates in patients with ATS (100 ± 8 vs 105 ± 4 bpm, NS). Higher pacing rates were achieved on ascending stairs in patients with QTS (115 ± 24 vs 93 ± 28 bpm, p < 0.01). We conclude that with comparable pacemaker settings, ATS results in a more prompt rate response while the peak pacing rate of QTS is delayed. Rate responses are similar with gradually progressive exercise. However, the magnitude of rate response with QTS is more proportional to the level of exertion.
Utility of the Atrial Endocardial Electrogram Concurrent with Dual‐Chamber Pacing in the Determination of a Pacemaker‐Mediated Arrhythmia
Authors: SHANDLING ADRIAN H. , CASTELLANET MARK J. , MESSENGER JOHN C. , BROWNLEE ROBERT R.
Published: July 2006

A 73‐year‐old male required a permanent pacemaker for complete heart block. After placement of the dual‐chamber pacemaker, the patient developed random, repetitive ventricularly paced coupling at the upper rate limit. The diagnosis made from the surface electrocardiography was one of ventricular tracking of occult (T wave obscured) atrial ectopic activity. Examination of the telemetered atrial electrogram (EGM) revealed a diagnosis of intermittent far‐field atrial sensing of the terminal ventricular depolarization. The value of obtaining an atrial electrogram during dual‐chamber pacing is discussed.
Changes in QT and Q‐aT Intervals Induced by Mental and Physical Stress with Fixed Rate and Atrial Triggered Ventricular Inhibited Cardiac Pacing
Authors: HEDMAN ANDERS , NORDLANDER ROLF
Published: July 2006

We have investigated the influence of mental stress and physical stress, i.e., exercise, on the QT and Q‐aT intervals (measured from the pacemaker stimulus to the end or the apex, respectively, of the T wave). The study was made on ten patients with high degree atrioventricular block treated with AV universal (DDD) pacemakers. These were programmed to a fixed rate ventricular (VVI) or an atrial triggered (VDD) function for different parts of the study. An arithmetic mental stress test and a bicycle exercise test were performed with each mode of pacing. In the VVI pacing mode, the atrial rate increased by 11% during mental stress and by 46% during exercise. There was a significant shortening of QT and Q‐aT intervals with both types of stress. With VDD pacing, mental stress induced a 12% increase in rate and a significant shortening of QT and Q‐aT. The paced rate increased by 50% during the exercise test. This increase in ventricular rate was associated with the most marked changes in QT and Q‐aT intervals. Thus, both types of stress cause a significant shortening of the QT and Q‐aT interval even in the absence of a simultaneous increase in ventricular rate. When the latter is allowed to increase during VDD pacing, both intervals shorten considerably more. There was a marked inter‐individual variability in the response to both types of stress. These findings are of importance with regard to the QT sensing rate responsive pacemaker which can be expected to respond to mental stress in most patients, but that response might be unpredictable in the individual.
Far‐Field QRS Complex Sensing Via the Atrial Pacemaker Lead. I. Mechanism, Consequences, Differential Diagnosis and Countermeasures in AAI and VDD/DDD Pacing
Authors: BRANDT JOHAN , FÅHRAEUS THOMAS , SCHÜLLER HANS
Published: July 2006

Unintended sensing of QRS complexes via atrial pacemaker leads may cause disorders of pacemaker function in AAI, VDD and DDD pacing. The consequences of this phenomenon depend upon the pacing mode and the timing of the inappropriate sensing as related to the technical characteristics of the pulse generator. With AAI pacemakers, “inappropriate pacemaker bradycardia” may be seen or P‐wave undersensing may be simulated. With VDD and DDD systems a special kind of pacemaker mediated tachycardia or apparent P‐wave undersensing may result. With knowledge of the underlying mechanisms, differential diagnosis is possible. The countermeasures available are discussed.
Clinical Experience with Sensolog 703: A New Activity Sensing Rate Responsive Pacemaker
Authors: LAU CHU‐PAK , TSE WANG‐SUM , CAMM A. JOHN
Published: July 2006

Sensolog 703 is a new activity sensing rate responsive pacemaker which detects body vibration during physical exercise and uses the vibration as an indicator of the physiological need for a rate increase. This pacemaker was implanted in 11 patients with complete heart block and atrial arrhythmias. Their mean age was 58 (range 39–72) years. With appropriate rate response, exercise capacity, as assessed by the duration of graded treadmill exercise using the Bruce protocol, was significantly improved over the WI pacing mode (mean ± SEM, 462 ± 52 s in the rate responsive mode and 368 ± 34 s in the VVI mode, P < 0.02). Cardiac output at peak exercise, as assessed by continuous wave Doppler sampling of aortic root blood flow, was also significantly increased compared to the resting value in both piecing modes. However, the increase was more marked when exercise was performed in the rate response mode (93 ± 22% increase over resting cardiac output in the rate responsive mode and 57 ± 13% increase in the WI mode, P < 0.05). The rate responses of this pacemaker were compared with those of a Medtronic Activitrax pacemaker. Although both pacemakers responded to an increase in walking speed, neither responded appropriately to walking up different gradients. In both cases, ascending and descending four flights of stairs resulted in similar pacing rates. There was no response to physiological activities with minimal body movements such as isometric exercise and the Valsalva maneuver. Technical problems were encountered in two implanted Sensoiog pacemakers: one had spontaneous rate acceleration at rest immediately following implantation and one showed intermittent rate acceleration while the patient was at rest. Both units were programmed to the WI mode. In conclusion, satisfactory rate response, improvement in exercise duration and increase in cardiac output were achieved with the Sensolog 703 pacemaker. However, as body vibration is not closely related to physiological needs, it has similar limitations in rate response as the Activitrax pacemaker.
Atrial Sensing to Augment Ventricular Tachycardia Detection by the Automatic Implantable Cardioverter Defibrillator: A Utility Study
Authors: SCHUGER CLAUDIO D. , JACKSON KENNETH , STEINMAN RUSSELL T. , LEHMANN MICHAEL H.
Published: July 2006

The triggering of automatic implantable cardioverter defibrillator (AICD) discharges by supraventricular tachycardias, despite the presence of a probability density function algorithm, remains a limitation of an otherwise highly effective device. We systematically investigated the diagnostic utility which theroretically could derive form the addition of atrial sensing capability to the AICD in 25 patients with 30 inducible sustained monomorphic ventricular tachycardias (VTs) at clinically relevant rates ( 150 beats/min). Patients were included only if they were not taking medication capable of depressing ventriculoatrial (VA) conduction for at least 5 half‐lives prior to electrophysiological testing. We tested the simple criterion for VT that ventricular cycle length (CL) be shorter than the atrial CL (not met in sinus or most other supraventricuilar tachycardias). Mean VTCL was 283 ± 47 ms (range 210 to 370). In 25 (83%) VTs, the VT criterion was consistently satisfied. Of the five cases in which the criterion was not met, 1:1 VA conduction during VT was present in four, three of which initially manifested 2:1 VA conduction lasting from 14 to 28 s and therefore would have transiently fulfilled the VT criterion. The remaining patient who failed to satisfy the VT criterion had ongoing atrial flutter during a relatively slower sustained VT, but this circumstance could be recognized because of the varying AV interval. The absence of 1:1 VA conduction at CLS 400 ms during ventricular pacing accurately predicted the absece of 1:1 VA conduction during VT in 95% of patients. Overall, then, use of the simple VT criterion early after tachycardia onset ‐ in tandem with AV interval tracking ‐ would have correctly identified 29/30 (97%) VTs. We conclude that simple incorporation of atrial sensing capability into the AICD, with corresponding software modification, is likely to facilitate differentiation of VT from supra‐ventricular tachycardia in the vast majority of patients.
Modification of the DDD Pacing Mode to Prevent Junctional Reentry Tachycardia: Computer Modelling Experiments
Authors: MALIK MAREK , DA VIES D. WYN , CAMM A. JOHN
Published: July 2006

This paper examines the possibility of using short atrioventricular (AV) delay dual chamber pacing to prevent junctional reentry tachycardia mediated by an accessory pathway or by an intra‐AV nodal circuit. For this purpose, a clinically realistic computer simulation model of cardiac rhythm and heart‐pacemaker interactions has been used. The computational experiments compared the actions of two pacemaker models: (A) a clinically realistic DDD mode operating with quasi‐Wenckebach prolongation of the AV delay; and (B) a new modification of the DDD mode introducing independent counters for the atrial and ventricular refractory periods of the heart, and the possibility of instantaneous or shortly delayed atrial pacing triggered by a sensed or paced ventricular event. The pathological phenomena modelled in the experiments simulate different possibilities of tachycardia initiation. These disorders include: (1) single atrial premature beats (APBs), (2) salvos of APBs, (3) closely coupled pairs of APBs, (4) ventricular premature beats initiating an antidromic reentry tachycardia, and (5) ventricular ectopic beats initiating an AV nodal reentry tachycardia. The computational results prove that many possible mechanisms of initiation of junctional reentry tachycardia are beyond the prophylactic capabilities of current sophisticated DDD pacemakers (A). The results also show that the suggested pacing mode (B) improves anti‐tachycardia prophylaxis even when responding to complex pathological episodes of the natural cardiac activity. Future development of the suggested mode (B) is discussed.
Fatigue of the His‐Purkinje System During Routine Electrophysiologic Studies
Authors: DiLORENZO DANIEL R. , SELLERS T. DUNCAN
Published: July 2006

In this report we describe fatigue of the His‐Purkinje system during retrograde stimulation of the His bundle by ventricular programmed stimulation. The patient underwent electrophysiologic evaluation for syncope, Antegrade conduction and supraventricular studies were normal with the exception of baseline left bundle branch block. During programmed ventricular stimulation, the patient developed intra‐Hisian and infra‐Hisian block with symptomatic 3:1 atrioventricular heart block requiring insertion of a permanent pacemaker. This case demonstrates the need for careful study of both antegrade and retrograde conduction properties of the His bundle and atrioventricular node when performing standard His bundle studies in evaluation of syncope.
A Comparative Analysis of Signal Averaging of the Surface QRS Complex and Signal Averaging of Intracardiac and Epicardial Recordings in Patients with Ventricular Tachycardia
Authors: GOMES J. ANTHONY , MEHRA RAHUL , BARRECA PHILIP , WINTERS STEPHEN L. , ERGIN ARISAN , ESTIOKO MANUEL , MINDITCH BRUCE P.
Published: July 2006

To test the hypothesis that late potentials may be more enhanced by signal processing of intracardiac and epicardial electrograms, we performed a comparative analysis of signal averaging (SA) of the surface QRS complex (method I), signal averaging of an endocardial electrode catheter recording (method II), and epicardial recording (method III) in 24 patients (mean age = 55 ± 14 years). Sixteen of (he 24 patients (66%) had spontaneous as well as induced sustained ventricular tachycardia (VT), whereas the remaining 8 patients (33%) had spontaneous non‐sustained VT. SA by the three methods was performed within ≤24 hours of each other, utilizing a band pass jilter frequency of 25 to 250 Hz. The duration of the SA‐QRS complex, low amplitude signals (LAS) of <40 μV and the RMS‐voltage (V) of the terminal 40 ms were determined for the three methods. There was a significant correlation between method I and methods II and III for the SA‐QfiS duration (r = .928, p < .001), RMS‐V(r = .634. p < .002) and LAS (r = .783, p < .001). There was no significant difference in the quantitative signal‐averaged parameters between the three methods. The incidence of the RMS‐V of <25 μV (37.5% vs 21%); LAS of >32 ms (46% vs 37.5%) and SA‐QRS of >120 ms (54% vs 42%) was higher but statistically non‐significant by methods II and III when compared to method I. We concluded that: (1) SA of intracardiac electrograms correlate well with SA of the surface QKS. This observation further validates the technique of surf ace SA to detect delayed ventricular activation. (2) SA of intracardiac electrograms may provide additional information on quantitative SA parameters relative to surface QRS in some patients with VT.
Evaluation and Management of a Supraventricular Tachycardia with a Standard Bradycardia Support Pacemaker
Authors: ESTRADA A.Q. , KOGAN A.D.
Published: July 2006

A standard dual chamber pacemaker with the ability to telemeter intracardiac electrograms and to perform noninvasive electrophysiological studies was implanted in a patient with previously documented complex ventricular arrhythmias treated with amiodarone who later presented with a hypersensitive carotid sinus syndrome and syncope. Subsequently, he developed a supraventricular tachyarrhythmia with an atrial cycle length of 320 ms. Its diagnosis was facilitated by the ability to noninvasively telemeter atrial endocardial electrograms directly from the implanted pacemaker. Its management was aided by utilizing the already implanted bradycardia support pacemaker to stimulate the patient with premature extrastimuli coupled to his intrinsic atrial rhythm (PS1 and S1S2 each 170 ms.) by connecting the pacemaker to au electrophysiological stimulator via the pacemaker programmer. This particular pacemaker was not chosen because of this capability at the time of its original implantation. However, this capability facilitated the patient's evaluation and subsequent management.
Course of Symptoms and Spontaneous ECG in Pacemaker Patients: A 5‐Year Follow‐up Study
Authors: LANGENFELD HEINER , GRIMM WOLFRAM , MAISCH BERNHARD , KOGHSIEK KURT
Published: July 2006

We investigated the course of symptoms and the spontaneous ECG retrospectively in 308 patients who had received a pacemaker because of atrioventricular (AV) block fn = 115), sick sinus syndrome (SSS, n = 107), bradyarrhythmic atriai jibriJiation (bradyarrhythmia, n = 51). carotid sinus syndrome (CSS, n = 16), complete bifascicular block associated with 1st degree AV block (n = 13) and with other indications fn = 6). The mean implantation time was 63 months. The clinical state of 93% of all patients improved after pacemaker implantation; their symptoms decreased markedly. Persisting syncopy in some patients with SSS, however, supports a restricted implantation policy. We rarely saw improved AV conduction in patients with AV block fn%). Furthermore, in patients with SSS, atrial fibrillation occured significantly more often (35%) than in those with AV block (17 %; P < 0.01). Only 3% of patients with SSS developed 2nd and 3rd degree AV block within the observation period. In all patients with Initial bifascicular block and additional 1st degree AV block, pacing prevented further syncopal attacks; four of them showed 3rd degree AV block at control, indicating that pacemaker implantation is mandatory in symptomatic patients with bifascicular disease and 1st degree AV block.
The Maximum Effect of an Increase in Rate on Human Ventricular Refractoriness
Authors: MORADY FRED , KADISH ALAN H. , TOIVONEN LAURI K. , KUSHNER JEFFREY A. , SCHMALTZ STEPHEN
Published: July 2006

The purpose of this study was to determine the maximum shortening of ventricular refractoriness that occurs following an increase in rate and to quantitate the duration of ventricular pacing required to obtain this maximum shortening of refractoriness. The subjects of the study consisted of 41 patients who underwent a clinically indicated electrophysiologic study. Ventricular refractory periods were measured with an extrastimulus (S2) at basic cycle lengths of 600 and 400 ms by Method A (8 beat basic drive trains and 4 second intertrain paue and Method B (drive train duration of 3 minutes, then an S2 after every eighth basic drive beat, with no pause after the S2). In 23 subjects, the mean ventricular effective refractory period determined by Method B was 12 ± 7 ms (± standard deviation) shorter than when determined by Method A at a basic drive cycle length of 600 ms (p < 0.0001] and 33 ± 9 ms shorter at a basic drive cycle length of 400 ms (p < 0.001]. In these 23 subjects, the drive train duration required for maximum shortening of ventricular refractoriness was estimated by counting the number of drive train beats preceding ventricular capture by an S2 inserted after every fourth basic drive beat at a coupling interval fixed at 5 ms longer than the ventricular effective refractory period determined in that subject by Method B. The mean number of basic drive beats preceding capture by S2 was 114 ±84 beats at a basic drive cycle length of 600 ms and 233 ± 85 beats at a BDCL of 400 ms. In six subjects the ventricular effective refractory period was measured by Methods A and B before and after autonomic blockade with propranolol and atropine, and the amount of shortening in the ventricular effective refractory period with Method B was not affected by autonomic blockade. In conclusion, the basic drive train has a cumulative effect on ventricular refractoriness in humans, and a drive train duration substantially longer than 50 beats often is required to obtain the maximum shortening of ventricular effective refractory period after an increase in rate. Therefore, ventricular effective refractory periods determined conventionally using 8 beat drive trains and a 4 second intertrain pause often may be overestimates of the actual ventricular effective refractory period. The shortening of ventricular refractoriness with long drive train durations is probably related to a prolonged duration of pacing required to obtain a steady‐state action potential duration after an increase in rate.
Narrow QRS Complex Tachycardia with Atrioventricular Dissociation
Authors: SHIMIZU AKIHIKO , OHE TOHRU , TAKAKI HIROSHI , KAMAKURA SHIRO , MATSUHISA MOKUO , SATO IWAO , SHIMOMURA KATSURO
Published: July 2006

We describe the case of a 22‐year‐old man who had frequent episodes of narrow QRS complex tachycardia with atrioventricular dissociation. The ECG during sinus rhythm showed normal PR and QRS intervals, hut it showed a left bundle branch block configuration during atrial pacing or after injection of verapamil. An electrophysiological study demonstrated that the patient had nodoventricular Mahaim fibers. The narrow QRS complex tachycardia was explained by a circuit involving antegrade conduction via the atrioventricular nodo‐His axis and retrograde conduction via the nodoventricular bypass tract.
Comparison of the Effects of Right Atrial, Right Ventricular Apex and Atrioventricular Sequential Pacing on Myocardial Oxygen Consumption and Cardiac Efficiency: A Laboratory Investigation*
Authors: BALLER DETLEV , WOLPERS HANS‐GEORG , ZIPFEL JOHANNES , BRETSCHNEIDER HANS‐JÜRGEN , HELLIGE GERHARD
Published: July 2006

As the impact of cardiac pacing on myocardial energetics has not yet been established, this laboratory investigation was undertaken to evaluate the ejects of right atrial (AP), right ventricular apex (VP) and atrioventricular sequential pacing (AVP) on cardiac energetics in a closed‐chest model. Ninety‐two pacing interventions were performed in ten anesthetized mongrel dogs with normal loading conditions and contractile states. The energetic effects of pacing were assessed in terms of myocardial oxygen consumption (MVOz), its hemodynamic determinants and cardiac effciency. Effciency was calculated as the ratio of O2‐equivalent of external cardiac work to MVO2, using standard definitions. In the first series of experiments 36 intra‐individual comparisons were made between AP and VP at identical rates (95–210 beats/min). In the second series AVP was compared to VP in 10 intra‐individual comparisons at identical rates (109–190 beats/min). MVO2 was lower (p < 0.001) during AP (8.30 ± 2.14 ml O2/min · 100 g) compared to VP (10.16 ± 3.15 ml O2/min · 100 g) at the same rate (158 ± 32 beats/min). Efficiency (p < 0.001) was considerably higher during AP (21.6 ± 5.7%) compared to VP (12.8 ± 5.9%). During AVP, MVO2 (10.85 ± 1.76 ml O2/min · 100 g) was not significantly different from VP (10.57 ± 1.34 ml O2/min · 100 g) at the same rate (146 ± 25 beats/min). Hemodynamics were superior with AVP compared to VP. Efficiency was significantly higher (p < 0.01) with sequential (15.4 ± 3.9%) as compared to ventricular pacing (12.0 ± 3.2%). In conclusion, this study indicated that VP exerts disadvantageous effects on MVO2 and cardiac effciency. AP has beneficial effects on cardiac energetics because it improves the relationship between mechanical performance of the heart and its energy requirements. AVP results in a higher efficiency than VP due to superior hemodynamics, despite MVO2 levels comparable to those of VP. The mechanism of energy waste with right ventricular apex pacing is probably related to an asynchronous contraction in the ventricular myocardium due to a nonphysiological spread of excitation.
Electrophysiological Observations During QRS Alternans in a Patient with Incessant Tachycardia
Authors: ELLENBOGEN KENNETH A. , ROGERS REGINA R. , SZENTPETERY SZABOLCS
Published: July 2006

Electrophysiological observations during preoperative and intraoperative study of a 46‐year‐old patient with incessant ventricular tachycardia and QRS alternans demonstrated a potential mechanism for this electrocardiographic finding. During QRS alternans, conduction delay (or block) was recorded from the site of origin of the tachycardia, high on the anterior septum to the His bundle: After procainamide infusion, the tachycardias slowed and, concurrent with the disappearance of QRS alternans, conduction from the site of tachycardia origin to the His bundle could no longer be demonstrated.