bluuebunny/crossref_metadata_2025 huggingface dataset:
Reconciling Salvage Logging of Boreal Forests with a Natural‐Disturbance Management Model
Authors: SCHMIEGELOW FIONA K.A. , STEPNISKY DAVID P. , STAMBAUGH CURTIS A. , KOIVULA MATTI
Published: July 2006

Abstract: In North American boreal forests, wildfire is the dominant agent of natural disturbance. A natural‐disturbance model has therefore been promoted as an ecologically based approach to forest harvesting in these systems. Given accelerating resource demands, fire competes with harvest for timber, and there is increasing pressure to salvage naturally burned areas. This creates a management paradox: simultaneous promotion of natural disturbance as a guide to sustainability while salvaging forests that have been naturally disturbed. The major drivers of postfire salvage in Canadian boreal forests are societal perceptions, overallocation of forest resources, and economic and policy incentives, and postfire salvage compromises forest sustainability by diminishing the role of fire as a critical, natural process. These factors might be reconciled through consideration of fire in resource allocations and application of active adaptive management. We provide novel treatment of the role of burn severity in mediating biotic response by examining its influence on the amount, type, and distribution of live, postfire residual material, and we highlight the role of fire in shaping spatial and temporal patterns in forest biodiversity. Maintenance of natural postfire forests is a critical component of an ecosystem‐based approach to forest management in boreal systems. Nevertheless, present practices focus heavily on expediting removal of timber from burned forests, despite increasing evidence that postfire communities differ markedly from postharvest systems, and there is a mismatch between emerging management models and past management practices. Policies that recognize the critical role of fire in these systems and facilitate enhanced understanding of natural system dynamics in support of development of sustainable management practices are urgently needed.
Salvage Logging, Ecosystem Processes, and Biodiversity Conservation
Authors: LINDENMAYER D.B. , NOSS R.F.
Published: July 2006

Abstract: We summarize the documented and potential impacts of salvage logging—a form of logging that removes trees and other biological material from sites after natural disturbance. Such operations may reduce or eliminate biological legacies, modify rare postdisturbance habitats, influence populations, alter community composition, impair natural vegetation recovery, facilitate the colonization of invasive species, alter soil properties and nutrient levels, increase erosion, modify hydrological regimes and aquatic ecosystems, and alter patterns of landscape heterogeneity. These impacts can be assigned to three broad and interrelated effects: (1) altered stand structural complexity; (2) altered ecosystem processes and functions; and (3) altered populations of species and community composition. Some impacts may be different from or additional to the effects of traditional logging that is not preceded by a large natural disturbance because the conditions before, during, and after salvage logging may differ from those that characterize traditional timber harvesting. The potential impacts of salvage logging often have been overlooked, partly because the processes of ecosystem recovery after natural disturbance are still poorly understood and partly because potential cumulative effects of natural and human disturbance have not been well documented. Ecologically informed policies regarding salvage logging are needed prior to major natural disturbances so that when they occur ad hoc and crisis‐mode decision making can be avoided. These policies should lead to salvage‐exemption zones and limits on the amounts of disturbance‐derived biological legacies (e.g., burned trees, logs) that are removed where salvage logging takes place. Finally, we believe new terminology is needed. The word salvage implies that something is being saved or recovered, whereas from an ecological perspective this is rarely the case.
Salvage Logging in the Montane Ash Eucalypt Forests of the Central Highlands of Victoria and Its Potential Impacts on Biodiversity
Authors: LINDENMAYER D.B. , OUGH K.
Published: July 2006

Abstract:  The two major forms of disturbance in the montane ash eucalypt forests of the Central Highlands of Victoria (southeastern Australia) are clearfell logging and unplanned wildfires. Since the 1930s wildfire has been followed by intensive and extensive salvage‐logging operations, which may proceed for many years after a wildfire has occurred. Although applied widely, the potential effects of salvage logging on native flora and fauna have been poorly studied. Our data indicate that the abundance of large trees with hollows is significantly reduced in forests subject to salvage harvesting. This has implications for the persistence of an array of such cavity‐using vertebrates as the endangered arboreal marsupial, Leadbeater's possum (Gymnobelidues leadbeateri). Salvage logging also reduces the prevalence of multiaged montane ash forests—places that typically support the highest diversity of arboreal marsupials and forest birds. Limited research has been conducted on the effects of salvage logging on plants; thus, we constructed hypotheses about potential impacts for further testing based on known responses to clearfell logging and key life history attributes. We predict many species, such as vegetatively resprouting tree ferns, will decline, as they do after clearfelling. We also suggest that seed regenerators, which typically regenerate well after fire or conventional clearfelling, will decline after salvage logging because the stimulation for germination (fire) takes place prior to mechanical disturbance (logging). Understory plant communities in salvage‐logged areas will be dominated by a smaller suite of species, and those that are wind dispersed, have viable soil‐stored seed remaining after salvage logging, or have deep rhizomes are likely to be advantaged. We recommend the following improvements to salvage‐logging policies that may better incorporate conservation needs in Victorian montane ash forests: (1) exemption of salvage logging from some areas (e.g., old‐growth stands and places subject to only partial stand damage); (2) increased retention of biological legacies on burned areas through variations in the intensity of salvage logging; and (3) reduction in the levels of physical disturbance on salvage‐logged areas, especially through limited seedbed preparation and mechanical disturbance.
Postfire Logging in Riparian Areas
Authors: REEVES GORDON H. , BISSON PETER A. , RIEMAN BRUCE E. , BENDA LEE E.
Published: July 2006

Abstract: We reviewed the behavior of wildfire in riparian zones, primarily in the western United States, and the potential ecological consequences of postfire logging. Fire behavior in riparian zones is complex, but many aquatic and riparian organisms exhibit a suite of adaptations that allow relatively rapid recovery after fire. Unless constrained by other factors, fish tend to rebound relatively quickly, usually within a decade after a wildfire. Additionally, fire and subsequent erosion events contribute wood and coarse sediment that can create and maintain productive aquatic habitats over time. The potential effects of postfire logging in riparian areas depend on the landscape context and disturbance history of a site; however, available evidence suggests two key management implications: (1) fire in riparian areas creates conditions that may not require intervention to sustain the long‐term productivity of the aquatic network and (2) protection of burned riparian areas gives priority to what is left rather than what is removed. Research is needed to determine how postfire logging in riparian areas has affected the spread of invasive species and the vulnerability of upland forests to insect and disease outbreaks and how postfire logging will affect the frequency and behavior of future fires. The effectiveness of using postfire logging to restore desired riparian structure and function is therefore unproven, but such projects are gaining interest with the departure of forest conditions from those that existed prior to timber harvest, fire suppression, and climate change. In the absence of reliable information about the potential consequence of postfire timber harvest, we conclude that providing postfire riparian zones with the same environmental protections they received before they burned is justified ecologically. Without a commitment to monitor management experiments, the effects of postfire riparian logging will remain unknown and highly contentious.
Clinical Value of Tests of Sino‐Atrial Function*
Authors: EVANS T.R. , CALLOWHILL E.A. , KRIKLER D.M.
Published: July 2006

Sinus node recovery times and the premature atrial stimulus test were studied in 36 patients, seven with gross sinus node disease, 25 with possible sinus node disease and four with no clinical evidence of sinus node disease. The corrected sinus node recovery time proved of most value in predicting which patients needed and would benefit from permanent pacemaker implantation, though there was one false negative diagnosis and two patients with abnormal corrected sinus node recovery times were asymptomatic. The premature atrial stimulus test usually proved to be of no practical value once severe sinus node disease was present and, in the group of patients with suspected sino‐atrial disease, only 13 of 25 graphs could be analysed due to gross “scatter” in the others.

When patients with symptoms have unequivocal evidence of sino‐atrial dysfunction, invasive study seems unnecessary. With lesser degrees of sino‐atrial disease, premature atrial stimulation may provide confirmatory evidence; but when sinus arrhythmia, atrial escape beats, or more marked dysfunction are present, one is likely to encounter useless “scatter” graphs. In the absence of regular sinus rhythm on the EGG, overdrive sinus node suppression is the only invasive study worth attempting.
Hemodynamic Consequences of Atrioventricular and Ventriculoatrial Pacing
Authors: OGAWA SATOSHI , DREIFUS LEONARD S. , SHENOY PRAKASH N. , BROCKMAN STANLEY K. , BERKOVITS BAROUH V.
Published: July 2006

The effect of atrialventricular versus ventricular pacing and contraction were studied in seven open‐chest dogs. Cardiac output, left ventricular, left atrial, right atrial and pulmonary artery pressures were recorded. The right or left ventricular apical areas were consistently superior as ventricular pacing sites.

Appearance of cannon A waves within the pre‐ or ejection period produced a significant decrease in left ventricular and systemic blood pressure, and cardiac output with a concomitant increase in right atrial, ventricular and pulmonary pressures. Prominent “v” waves were also observed during these periods.

Reducing the basic driving cycle length from 400 to 300 msec caused a marlted deterioration of all hemodynamic parameters with the appearance of mechanical alternans. Random VA conduction or ventricular pacing in the presence of com‐plete AV and VA heart block appeared to offer a more favorable hemodynamic result than constant 1:1 VA conduction. It is concluded that maintenance of a physiologic AV interval permitting atrial contraction to appear outside of pre‐ or ejection period of ventricular systole is an important determinant or ventriculor function during cardiac pacing.
Influence of Output Capacitor, Electrode and Pulse Width on Power Consumption in Cardiac Pacing‡
Authors: EDHAG OLOF , LAGERGREN HANS , THORÉN ANDERS , WAHLBERG INGER
Published: July 2006

Three different types of unipolar endocardial electrodes—47 in all—were compared in regard to power consumption at stimulation threshold with six different output capacitors and seven pulse widths.

Fifteen were conventional large surface electrodes (area 47 mm2); 18 were conventional small surface electrodes (area 6 mm2), and 14 had a specially designed tip with a large area but small active surface of 8 mm2. Pulse widths ranged from 0.15 to 2.0 msec and output capacitors from 1.0 to 22.0 4mUFarads. All in all about 2,000 measurements were performed. The average current drain to the pacemaker output stage was measured and power consumption was calculated for each electrode— pulse width—output capacitor combination. In all combinations, the two small surface electrodes consumed approximately the same amount of power and, in both cases, significantly less than the larger one.

With regard to power economy at stimulation threshold, the pulse width of choice was about 0.5 msec and, furthermore, power consumption decreased with increasing capacitor size. The optimal combination was a small surface electrode, an output capacitor of 22 pF and a pulse width of 0.5 msec.
Permanent Cardiac Pacing with Electrodes of a New Type of Fixation in the Endocardium
Authors: BREDIKIS JURGIS , DUMCIUS ARIMANTAS , STIRBYS PETRAS , MUCKUS KAZIMIERAS , VETEIKIS ROMUALDAS , KOROLIOV VLADIMIR , YARMILKO PIOTR
Published: July 2006

To improve electrode construction the following main problems have been considered: (1) reliable initial fixing in the endocardium, and (2) reducing the area of contact surface and improving threshold values.

In this article we have described three original electrodes: (1) an endocardial electrode with a multi‐edged tip (contact area 28 mm2), which gives high electric field strength and low thresholds; 2) a spreading tip electrode, which was created on the basis of morphological data. The tissues grow into the spread spaces of this tip and ensure better stability fcontact area 17.8 mm2); and 3) a double‐screw‐in electrode which differs from the other corkscrew types. The contact end (surface area‐10,4 mm2) consists of two sickle‐shaped hooks. The sickle handle is 0.7 mm in length which prevents further hook penetration in the wall of the heart.

It was found that a multi‐edged electrode and electrodes supplied with a fixation device are, in terms of energy consumption, more effective compared to electrodes with spherical or cylindrical tips of the same area of contact surface.

The double‐screw‐in endocardial electrode has useful features: reliable fixation and a small contact surface area and, therefore, a low threshold value. Thirty‐five double‐screw‐in electrodes were inserted into an atrial position and 28 into a ventricular position. We have not observed any displacement of such electrodes during the past two years.
Unusual Electrocardiographic Pattern During Transvenous Pacing From the Middle Cardiac Vein
Authors: BAROLD S. SERGE , BANNER RICHARD
Published: July 2006

This report documents the unusual occurrence of a left bundle branch block pattern of ventricular depolarization during permanent pacing from the middle cardiac vein. All previous reports of ventricular pacing from the middle cardiac vein have described a right bundle branch block pattern of ventricular activation (dominant R‐waves in the right precordial leads), except in one case where both right and left bundle branch block patterns occurred at separate times.

A high posterior infarct allowed early activation of the right ventricle from the middle cardiac vein. Undue reliance on the electrocardiogram may detract from the diagnosis of electrode malposition.
Self‐Conversion of Supraventricular Tachycardia by Rapid Atrial Pacing*
Authors: WAXMAN MENASHE B. , WALD ROBERT W. , BONET JORGE F. , MACGREGOR DAVID C. , GOLDMAN BERNARD S.
Published: July 2006

The use of pacemakers in the treatment of tachycardias is one of the most exciting and rapidly expanding applications of cardiac pacing. One of the more recent developments in this field has been the use of patient‐activated radio frequency transmitted rapid atrial stimulation (RAS) in the treatment of paroxysmal supra‐ventricular tachycardia (PSVT). Based on the previously established ability of asynchronous atrial pacing to interrupt a variety of re‐entrant supraventricular rhythm disturbances, this modality of treatment is gaining increasing applicability in patients with PSVT associated with debilitating symptoms or other severe cardiovascular consequences in whom standard pharmacological regimens have either failed or are impossible to maintain for indefinite periods.

This report describes our experience with five patients who underwent implantation of HAS units. The detailed electrophysiological studies required to ensure success and avoid any possible future complications are described. Over a follow‐up period of four months to four years (mean 16 months) very few problems arose in the use of these units which have immeasurably improved the quality of life of the recipients. Our experience with RAS units has led to a few suggestions for future improvement and these are outlined in this report.

The excellent patient acceptance and the reliability of this technique in terminating episodes of PSVT should, in the future, render RAS the treatment of choice in certain selected patients suffering form this common disorder.
Electromagnetic Interference in Implantable Pacemakers*
Authors: IRNICH W. , de BAKKER J.M.T. , BISPING H.‐J.
Published: July 2006

The inhibited pacemaker (VVI or AAI) has become the most popular in recent years because of its ability to combine a physiological advantage with economical current consumption in cases with spontaneous activity. One of its disadvantages is its sensitivity to external electromagnetic interference. Though today's pacemakers possess, effective protection against most interference signals there may be instances in which patients are subjected to uncomfortable or even life‐threatening situations. This is the case of “amplitude modulated” or “pulsed” fields with modulation frequencies in the physiological range. Fields of that sort have been found in the vicinity of a welder, an electric steel plant, and in medical practice where therapeutic currents were applied. Even touch‐actuated switches may influence a demand pacemaker. However, these situations may be overcome by a device within the pacemaker for simple time analysis which can be carried out with few components. If electromagnetic fields of diathermy equipment are applied, today's pacemakers may react with intolerably high or low rates. They should, therefore, be avoided.
The Diagnosis of Right Ventricular Perforation by an Endocardial Pacemaker Electrode
Authors: MOND HARRY G. , STUCKEY JOHN G. , SLOMAN GRAEME
Published: July 2006

The diagnosis of right ventricular perforation by an endocardial pacemaker electrode should be suspected when failure of pacing occurs without electrode displacement. Although a number of changes occur on the standard electrocardiogram (ECG), none of these are diagnostic. The intracardiac electrogram performed during electrode withdrawal is not only diagnostic of perforation but can also aid in electrode positioning. Two case reports highlight these changes in the intracardiac electrogram. The first case also illustrates that, with electrode perforation, the ability to sense the intrinsic intracardiac electrical activity may be retained.
Persistent Atrial Standstill with Atrial Inexcitability
Authors: AMRAM SALOMAO S. , VAGUEIRO M. CELESTE , PIMENTA ALVARO , MACHADO H. BASTOS
Published: July 2006

Electrophysiologic studies including His bundle recording, atrial, and ventricular stimulation, were performed in three symptomatic patients with persistent atrial standstill of unknown etiology. The rhythm was junctional in two cases and ventricular in one. In two cases, evidence suggestive of associated impairment of the His bundle conduction system was found. The atria were inexcitable at multiple sites and no retrograde conduction to the right atrium could be elicited by ventricular pacing. Follow‐up in the three cases, respectively for 48, 42 and 12 months after pacemaker implantation, revealed no return of spontaneous atrial electrical activity.
Atrial Programmed Pacing*
Authors: SMYTH NICHOLAS P.D.
Published: July 2006

Early experience with a J‐shaped lead inserted transvenously into the right atrial appendage is reviewed in thirty‐one patients. Fifteen patients are still being followed with satisfactory atrial programmed pacing for five to (en years. A dislodgement rate of twenty percent led to the development of the “lined” J lead in the hope that better fixation would be achieved.

Experimental data has shown the new lead to be stable with evidence in both animal and man of firm fixation of the lead in the appendage. The lead has been inserted in twenty patients. Of these, fifteen are still being followed with satisfactory atrial programmed pacing. There has been no case of dislodgement of the lead in a follow‐up period of two years and eight months.
Transvenous Long‐Term Pacing with an External Pacemaker. What are the risks?
Authors: SIDDONS HAROLD
Published: July 2006

Externalized endocardial electrodes were used for pacing 138 patients for periods of one month to 12 years. In the 416 patient/years of pacing by this method, 13 septicemias occurred.

Implanted pacemakers with endocardial electrodes were used in 3186 patients. In the 3488 patient/years 13 septicemias occurred.

The mortality and an assessment of the cause of death for pacing by the two methods is presented.

It is concluded that the external method of transvenous pacing carries additional risk and is only justified in special circumstances.
Phantom Pacemaker Programming*
Authors: FIELDMAN ARNOLD , DOBROW ROBERT J.
Published: July 2006

Spurious or “phuntom” programming of programmable pacemakers may occur as the result of two phenomena. One is change in rate and/or output of the generator from an anomalous source (dysprogramming); the other is a generator response different from that intended and set on the conventional programmer (misprogramming). In either case, the result is a nuisance, at best. Conceivably, at worst, an irreversible subthreshold output could be induced. Despite wide usage of such devices, neither event has been reported, in the routine folow‐up of 95 implanted Cordis Omni‐Stanicor®† generators, we have observed three instances of dysprogramming upon application of a magnet commonly used to induce the asynchronous mode. Subsequent in vitro studies revealed magnetically induced programming reed switch vibration in 9 of 6,680 units, which could account for the in vivo observations. We also describe many instances of misprogramming, attributable, in most cases, to a faulty programmer emission count. In this series, none of the anomalies was clinically detrimental. However, anyone involved in pacemaker follow‐up should be alerted to the existence of these potentially hazardous phenomena.
Effect of Electroconvulsive Therapy on Cardiac Rhythm, Conduction and Repolarization*
Authors: TROUP PAUL J. , SMALL JOYCE G. , MILSTEIN VICTOR , SMALL IVER F. , ZIPES DOUGLAS P.
Published: July 2006

Because sympathetic stimulation has been implicated in the genesis of arrhythmias, we studied the effects on arrhythmias of electroconvulsive therapy (ECT). Fifteen psychiatric patients (male: 8, female: 7, age: 19‐51, mean: 29.8) without known heart disease underwent 24‐hour Holter recordings before, during, and after ECT (25 episodes). All patients were taking psychotropic drugs and received atropine (0.4‐1.2 mg, mean: 1.1 mg IV), methohexital, and succinylcholine prior to ECT. Following ECT, mean maximum heart rate increased (106 ± 3.2 to 142 ± 6.0 beats/min, p < .001), PR interval decreased (149 ± 3.3 to 131 ± 3.7 msec, p < .001) and QTC interval increased (432 ± 6.5 to 454 ± 9.7 msec, p < .001) compared to values obtained after atropine administration. Mean PVC or PAG frequency immediately after ECT or per 24 hours did not change significantly (PVC per 24 hours 6.8 ± 3.2 to 10.4 ± 6.4, NS; PAC per 24 hours 0.4 ± 0.3 to 0.3 ± 0.2, NS) and no complex arrhythmias were noted. Rate and PR changes suggest adrenergic effeqts of ECT and QTC increase may be due to imbaianced sympathetic discharge. Autonomic stimulation produced by ECT did not induce arrhythmias in these patients without heart disease. The possible antiarrhythmic role of psychotropic agents or premedication is unknown.
Methods for Recording Intermittent Contact Signals in Demand Pacemaker Arrhythmias (11 cases)
Authors: MUGICA J. , DUCONGE R. , DUBOS M. , LAZARUS B.
Published: July 2006

This report describes some of the various techniques which may be used to demonstrate intermittent and/or incomplete fracture of a pacing lead. Eleven patients treated with an R‐wave‐inhibited demand pacer showed signs of paroxysmal arrhythmias, Intraoperative recordings of the ventricular electrogram showed the presence of spurious signals mimicking an R‐wave. These signals varied from patient to patient but remained morphologically constant when a given technique was used in a given case. The most significant signals were picked up when pacing and recording on the same lead.
The Noise Sampling Period: A New Cause of Apparent Sensing Malfunction of Demand Pacemakers
Authors: FALKOFF MICHAEL , ONG LING S. , HEINLE ROBERT A. , BAROLD S. SERGE
Published: July 2006

Two patients with Omni‐Stanicor®* pulse generators presented an apparent sensing problem characterized by intermittent reversion to fixed‐rate pacing only during atrial fibrillation with a very rapid ventricular rate, Every fixed‐rate cycle contained two unsensed beats. The first un‐sensed beat fell in the noise sampling period (the last 3/6 of the pacemaker refractory period) and, therefore, disabled the demand function of the pulse generator for a single timing cycle. The presence of two consecutively unsensed beats within one timing cycle (automatic or escape interval) during tachycardia suggests normal function of the noise sampling period of this particular pulse generator, rather than a true sensing problem. The diagnosis becomes evident if the sensing problem disappears when abbreviation of the refractory period occurs by reprogramming the pulse generator at a higher rate.
Unusual Complication of Bifascicular Block During Surgery Under General Anesthesia
Authors: FALKOFF MICHAEL , STOWE STEPHEN , ONG LING S. , HEINLE ROBERT A. , BAROLD S. SERGE
Published: July 2006

This report describes the occurrence of Mobitz type II AV block during surgery under general anesthesia in a patient with apparently uncomplicated right bundle branch and left anterior fascicular block (RBBB and LAH). Although prophylactic pacing is not usually recommended in uncomplicated HBBB and LAH, the events in this case suggest that this abnormality may not always be benign during surgery. Continuous monitoring is essential and emergency equipment for temporary pacing should be readily available near the operating and recovery rooms.
Cardiac Electrophysiologic Action of Carteolol Hydrochloride (OPC‐1085), a New Beta‐Adrenergic Blocking Agent*
Authors: WATANABE YOSHIO , TODA HITOSHI , OZAWA MIGHIE
Published: July 2006

Cardiac electrophysiologic action of a new beta‐adrenergic blocking agent carteolol hydro‐chloride, or OPC‐1085, was studied in either isolated, perfused rabbit hearts or in atrial, ventricular or Purkinje fibers of dogs and rabbits superfused in the tissue bath. Transmembrane potentials were recorded with intracellular microelectrodes and atrioventricular conduction was studied by recording a His bundle electro‐gram. OPC‐1085 at a concentration of 0.1 mg/L shortened the sinus node recovery time, while propranolol at a coraparable concentration prolonged it, Isoproterenol‐enhanced canine Purkinje automaticity was more markedly depressed by OPC‐1085 than by propranolol. In rabbit atrial and ventricular muscle, OPC‐1085 up to the concentration of 2 mg/L did not alter the action potential characteristics but tended to shorten the conduction time. At 20 mg/L, OPC‐1085 significantly decreased the maximal rate of depolarization and maximal following frequency, and prolonged the action potential duration and conduction time in non‐reserpinized as well as reserpinized preparations. On atrioventricular conduction, 0.1 mg/L to 5 mg/L of this drug prolonged the St‐A and H‐V intervals but tended to shorten the A‐H interval. All these intervals were prolonged at 20 mg/L. The action potential duration of canine Purkinje fibers was shortened, whereas the effective refractory period was prolonged. Purkinje‐ventricular block developed at higher frequencies of stimulation. In view of the clinical dosage levels, it is suggested that the antiarrhythmic effects of OPC‐1085 depend predominantly on its beta blocking action. At higher concentrations, OPC‐1085 may exert some beta stimulating action, whereas still higher and possibly toxic concentrations could depress conduction through a direct membrane effect.
Reciprocating Tachycardia Due to a Right‐Sided Unidirectional Retrograde Anomalous Pathway (URAP)*
Authors: ORZAN FULVIO , GILLETTE PAUL C.
Published: July 2006

An 8 year‐old boy had extensive electrophysiological evaluation of his recurrent supraventricular tachycardias. His EGG never showed delta waves but intracardiac stimulation and recording disclosed the following: (1) eccentric retrograde atrial activation; (2) increased cycle length and retrograde conduction time following the development of right bundle‐branch block; (3) constant retrograde conduction time for increasingly premature ventricular stimuli; (4) atrial captures by ventricular stimuli when the atrioventricular‐His pathways were refractory; and (5) no delta waves upon stimulation of the atrial input site of the anomalous pathway. A diagnosis of reciprocating tachycardia involving retrograde conduction through an accessory pathway was made.

Reciprocating tachycardias involving a unidirectional retrograde anomalous pathway can be easily misdiagnosed as atrioventricular node reentrant tachycardias if no evidence of preexcitation can be found, particularly if the anomalous pathway is on the right side. In order to exclude the participation of a concealed unidirectional anomalous pathway in a patient's reentry tachycardia, a complete map must be made of right and left atrial endocardial activity.
Acute Ischemic Sinus Node Dysfunctions in Dogs
Authors: BILLETTE JACQUES , BONIN JEAN‐PIERRE
Published: July 2006

The effects of the occlusion of the two main atrial arteries irrigating the sinus node on sinus rhythm and postpacing sinus recovery were studied in 12 anesthetized dogs. Records of spontaneous rhythm and of postpacing sinus recovery were taken at control and hourly for 6 hours after the occlusion. The spontaneous cycle length (AA interval) was 335 ± 11 ms at control and 416 ± 17 ms (mean ± SE) (p < 0.005) one hour after the occlusion. It remained nearly unchanged during the following 5 hours of observation. The occlusion also shortened atrioventricular conduction time [AV interval] and reduced P‐wave amplitude in EGG lead II in 9 of these dogs. While the control postpacing sinus recovery time was 397 ± 13 ms, the 3‐hour value was 715 ± 165 ms. This prolongation persisted during the first four postocclusion hours but was Jess marked during the last two hours of observation. Moreover, the postpacing mode of return of the AA intervals to their prepacing value (sinus recovery pattern) became characteristically slow and progressive after occlusion, complete post‐pacing recovery often occurring only after 100 or more beats. Sequences of escape atrial and/or AV functional rhythms were frequently seen during this recovery. Atrial extrasystoles and short sequences of atrial tachycardias were observed in most dogs after occlusion. Conversely, none of these changes occurred during a 6‐hour experimental time in 5 control dogs in which the same protocol, occlusion excepted, was repeated. These observations show that the sinus node function in the dog is consistently affected by impairing its blood supply. Ischemic dysfunctions include sinus slowing, pacemaker shift, prolonged sinus recovery time, delayed post‐pacing recovery and supraventricular tachyarrhythmias.
Comprehensive Cardiac Pacemaker Information System: Basis for a Regional Follow‐up Network
Authors: HANSON JOHN S. , GRANT MICHAEL E.
Published: July 2006

The capabilities of a mini‐computer‐oriented permanent pacemaker information system are described. Extensive patient and pacer functional data are maintained in readily accessible files which may be displayed on a CRT terminal or printed out. Selective sorting of stored information may be accomplished according to any desired set of inclusive or exclusive criteria. Intelligent, comprehensive patient follow‐up has been greatly facilitated through application of the system. In view of the rapidly expanding pacemaker population, it is suggested that cooperative regional networks operating with comparable information storage and retrieval structures will provide the only means for adequate patient surveillance and compilation of necessary pacemaker data.
Unipolar Ventricular Electrogram in the Diagnosis of Right Ventricular Ischemic Injury
Authors: VARRIALE PHILIP , NIZNIK JOSEF
Published: July 2006

Unipolar ventricular electrograms were recorded in the right ventricular apical area in five patients with clinical, hemodynamic features of the right ventricular infarction.

The intracavitary potential exhibited a downward displacement of the ST segment (1.5 mV). This significant negative current of injury in the ventricular electro‐gram is consistent with ischemic injury of the free right ventricular wall in the area subtended by the intracavitary exploring electrode.

We suggest that ventricular electrographic recordings be performed in patients who present with acute inferior wall infarction requiring temporary electrode catheter pacing for serious AV conduction disturbances. The presence of a significant downward ST segment displacement (1.5 mV) provides further support and an electrical criterion for right ventricular ischemic injury.

unipolar, ventricular electrogram, endocardial potential, negative deflection, ischemic injury, right ventricular infarction
Unusual Mechanism in the Initiation of the Paroxysmal Supraventricular Tachycardia in a Patient with WPW Syndrome
Authors: TAKAGI MAKOTO , ICHINOSE SUSUMU , TSURUHA YOSHIAKI , SHIOTSU HIROAKI , UWATOKO HIROHISA
Published: July 2006

A heretofore unre‐ported unusual mechanism in the initiation of the paroxysmal supraventricular tachycardia fPSVTj in a patient with WPW (Wo/ff‐Parkinson‐Whitej syndrome was observed using His bundJe recordings. The patient initially had some degree of AV conduction disturbance at the JeveJ of the AV node. A premature atriaJ impulse initially activated the ventricle exclusively through the accessory pathway and the same impulse re‐excited the ventricle via the AV nodai‐His axis after finishing the pure pre‐excitation with marked prolongation of the AH and the HV intervals. After finishing this double ventricular response it traversed to the atrium to produce the PSVT.
Characterization of Atrial Fibrillation in Man: Studies Following Open Heart Surgery*
Authors: WELLS JAMES L. , KARP ROBERT B. , KOUCHOUKOS NICHOLAS T. , MACLEAN WILLIAM A.H. , JAMES THOMAS N. , WALDO ALBERT L.
Published: July 2006

The nature of localized atrial activation during atrial fibrillation was characterized in 34 patients following open heart surgery. Bipolar atrial electrograms (AEG) recorded in each patient with atrial fibrillation exhibited a myriad of sizes, shapes, polarities, amplitudes, and beat‐to‐beat intervals. On the basis of the AEG morphology and the nature of its baseline, we have classified the recordings into four Types. Type I was characterized by discrete AEG complexes separated by an isoelectric baseline free of perturbation, Type II by discrete AEG complexes but with perturbations of the baseline between complexes, Type III by AEGs which failed to demonstrate either discrete complexes or isoelectric intervals, and Type IV in which AEGs of Type III alternated with periods characteristic of Type I and/or Type II. In 22 patients, the AEGs were recorded a second time, and in 11 of these patients the type of atrial fibrillation changed between the first and second recording period. An atrial flutter‐fibrillation pattern in the ECG was associated with a relatively ordered atrial activation pattern and a relatively slow atrial rate. Human atrial fibrillation is not an electrophysiologically homogeneous process when compared among different patients or ad seriatim in the same patient.
Preliminary Experience with the pH‐triggered Pacemaker
Authors: CAMMILLI L. , ALCIDI L. , PAPESCHI G. , WIECHMANN V. , PADELETTI L. , GRASSI G.
Published: July 2006

cardiac pacemaker capable of responding to blood acidosis by change in its stimulation rate allows adjustment to a patient's metabolic needs. The blood pH is sensed by an iridium oxide electrode in the right atrium. During exercise, the venous pff decreases and the paced ventricular rate increases. If acidosis persists, the paced rate gradually returns to baseline and reaches it after about 70 minutes. A pH‐triggered pacemaker has been implanted in a 72‐year‐old male. The pacemaker remained responsive one year after implant, increasing rate during exercise, cold pressor stress, ischemia of the arms and emotional stress.
Permanent Pacing in the Elderly
Authors: STRAUSS HANS D. , BERMAN NEIL D.
Published: July 2006

A total of 89 patients, age 80 years or older at the time of initial permanent pacemaker implantation, were followed for 10 to 128 months (mean 32.7), There were 54 males and 35 females. The mean age was 84.8 years. There were 51 patients age 80–84, 25 age 85–89, and 13 age 90–94. The actuarial 5‐year survival was 457%. Complications occurred in 23 patients (40 episodes). To date, 41 patients have already required at leasl one pulse generator replacement and 2 patients have already required 5 replacements. All but 3 patients were symptomatic prior to pacing and 56 were asymptomatic at last follow‐up. Permanent pacing in the elderly is therapeutically rewarding and not associated with excess morbidity.
Risks of Delayed Potentials in Pacemaker Patients Prone to Ventricular Tachycardia*
Authors: FONTAINE G. , FRANK R. , PETITOT J.C. , GROSGOGEAT Y.
Published: July 2006

Late potentials occurring after completion of the QRS complex have been observed in patients prone to ventricular tachycardia. They were recorded either during epicardial studies or in the catheterization laboratory. This paper describes such abnormal myocardial activity and discusses their potential effects on cardiac pacemakers.
Termination of Symptoms in the Sick Sinus Syndrome by Atrial Fibrillation
Authors: LISTER JOHN W.
Published: July 2006

A female patient with symptomatic sick sinus syndrome (SSS) had a permanent pacemaker implanted. She later developed chronic atrial fibrillation with an adequate ventricular rate. When the puise generator failed she was found to be clinically asymptomatic. This patient had never adjusted emotionally to her pacemaker and, since she was asymplomatic and in a stable rhythm, the failed pacemaker was not replaced. Possibly, thought should be given to the discontinuance of pacing for the SSS when, in the presence of adequate A‐V conduction, stable atrial fibrillation develops.
Spontaneous Termination of Reentry Ventricular Tachycardia in the Late Myocardial Infarction Period: An Experimental Study in the Dog
Authors: OGAWA SATOSHI , KAPLINSKY ELIESER , DREIFUS LEONARD S.
Published: July 2006

Forty episodes of induced ventricular tachycardia in the late myocardial infarction period (4‐6 days old) were analyzed in 12 dogs in an attempt to identify the possible mechanisms for the termination of reentry tachycardia. Multiple epicardial and endocardial composite electrograms were recorded in and around the central ischemic zone of the infarction. During tachycardia, the earliest site of activation was identified in the epicardial surface of the border or normal zone immediately adjacent to the ischemic zone in 36 of the 40 episodes, suggesting efferent epicardial spread from the site of the activity. In four instances, the efferent pathways were directed to the endocardial surface

Four distinct patterns of activation sequences were observed during spontaneous termination: (a) a shift of the efferent pathways from epicardial to endocardial site (19 instances); (b) a change of the efferent pathways within the endocardium (4 instances); (c) a shift of the earliest site of activation between the left arid right ventricles (9 instances); and (d) no apparent change in the epicardial efferent pathways (4 instances). In four other instances, ventricular tachycardia deteriorated into ventricular fibrillation. In patterns (a) and (c), a shift of the efferent pathways resulted in a more rapid and homogeneous activation of the border and normal zone epicardium. These changes were associated with cessation of delayed or continuous activity in the ischemic zone epicardium, resulting in termination of tachycardia. (PACE, Vol. 2, May‐June, 1979)
The Optimization of the Pulse Delivered by the Pacemaker
Authors: DRESSLER L. , GRUSE G. , von KNORRE G.H. , OTTE K.‐B. , PODSZUZ G. , RIGHWIEN R. , SCHAEDEL H. , WEBER D. , WEBER D. , WITTE J.
Published: July 2006

The results of stimulation threshold analysis carried out in 230 patients after the initial electrode implantation, and in 188 patients during pacemaker replacement, are presented. The electrodes investigated were the IE‐60K‐10 (279 cases), the IE‐60‐K (96 cases) and the ME‐50 (26 cases). The chronic stimulation threshold voltage for the electrode 7E‐60K‐1Q (electrode surface area: 10 mm2) at a pulse width of 0.5 ms, after an electrode function time of 25 months, is 2.05 ± 0.18 V, representing 256% of the acute threshold, and is equally as high as the chronic figure for the JE‐60‐K electrode; 0.43 mA (291 %). On the basis of the computation of the stimulation threshold energy and the stimulation threshold charge, a reduction of pulse duration (a below 0.5 ms would not appear to make such energy‐saving sense. (PACE, Vol. 2, May‐June, 1979)
Automatic “Scanning” by Radio‐frequency in the Long‐Term Electrical Treatment of Arrhythmias
Authors: CRITELLI GIUSEPPE , GRASSI GINO , CHIARIELLO MASSIMO , PERTICONE FRANCESCO , ADINOLFI LORENZO , CONDORELLI MARIO
Published: July 2006

The use of programmed electrical stimulation in the long‐term treatment of re‐entry tachycardia offers encouraging perspectives. Among the others proposed, the “scanning” system seems to be the most effective. However, an implantable stimulator with these features is not yet available and, thus, a temporary external lead is required. These difficulties have been overcome by utilizing radiofrequency to synchronize and stimulate. An implantable device was therefore designed which is triggered by the patient and automatically searches the interruption zone of the tachycardia by exploring the R‐R cycle. The external transmitter, which can produce one or two synchronized impulses, is programmed to scan the R‐R cycle with progressive steps of 5 or 10 ms; when tachycardia is interrupted, further stimulation is inhibited. The implanted module connected to an endocavitary lead does not have any power supply and, therefore, is very small. The efficacy of this method has been demonstrated in 4 patients with supraventric‐ular lacycardia (3 with WPW syndrome) resistant to conventional pharmacologic therapy. (PACE, Vol. 2, May‐June 1979)
Beat‐to‐Beat Stability of Implanted Pacemakers
Authors: KRESH YASHA M. , PARSONNET VICTOR , MYERS GEORGE H. , PARSONNET BRIAN
Published: July 2006

A method of measuring and analyzing beat‐to‐beat interval stability of implanted pacemakers has been devised, and a number of normal and failing pacers have been studied in this way. It was seen that normal pacer rates were remarkably stable, but that abnormalities in beat‐to‐beat interval were found in 67.4% of all failing pacers. The abnormalities consisted primarily of excessive interval (rate) scatter, linear and cyclic fluctuation, and transients following application of a magnet.

It is expected that in problem cases a beat‐to‐beat analysis will be of help in differentiating normal from abnormal pacer function, and will provide confirmation signs of pacer failure; it may also uncover unusual and heretofore unpredictable failure modes. (PACE, Vol. 2, May‐June, 1979)
Sick Sinus Syndrome and AV Node Re‐entry*
Authors: TORNOS PILAR , HEDDLE WILLIAM , TONKIN ANDREW
Published: July 2006

A 69‐year‐old man presented with recurrent palpitations since childhood. Electrophysiology studies performed on two separate occasions revealed the combination of sick sinus syndrome and AV node re‐entrant tachycardia. The case is reported because it illustrates marked temporal variability in the electrophysioiogical properties of the dual AV node pathways, and also deleterious effects of verapamil on sinoatrial node function. (PACE, Vol. 2, May‐June, 1979)
Radiation From Implantable Nuclear Pacemakers. II. Analysis
Authors: JACOBSON PETER M.
Published: July 2006

The dose equivalent rate from a nuclear pacer was determined in a previous paper10 through direct measurements of the gamma contribution, and through calculations of the neutron contribution which make use of computer simulation work done at the Oak Ridge National Laboratory. The resulting annual dose equivalent has been shown to be a level generally acceptable to adult individuals exposed for less pressing reasons than long‐term cardiac pacing, in a comparison with the maximum permissible dose (MPD). Other guide lines have been applied elsewhere, but are largely inappropriate. The MPD is a level expected to produce a vanishingly small risk for exposed individuals.
Inappropriate Slowing of the Pacemaker Rate with Programmahle Demand Pacemaker
Authors: BAROLD S. SERGE , GOULD LAWRENCE , REDDY C.V.R. , SINGH BRIJESH K. , ZEN BUJUNG
Published: July 2006

A 60‐year‐old male with a programmable pacemaker developed inappropriate slowing of the pacemaker rate. This was due to oversensing of the T waves combined with after‐potential sensing. This does not represent generator malfunction and can usually be corrected by reprogramming the pulse duration, or the milliamperage.
A New Concept for Atrial Triggered Pulse Generators
Authors: PEHRSSON KENNETH , LENTELL JAN , LEVANDER‐LINDGREN MAI , SVENSSON BENGT
Published: July 2006

In order to avoid the potential risk of a short refractory period and the inconvenience of the electronic blocking mechanism at the highest synchronous rate with the conventional atrial triggered pulse generator, two more functions have been added to the normal atrial triggered (VAT) pulse generator. First, it has been designed to be ventricular inhibited; second, a highest synchronous rate detector has been added, When the highest synchronous rate of about 140 is exceeded, the atrial signals are blocked and the frequency of the basic rate generator is increased to about 130. Two patients could hardly feel the change from atrial triggered pacing to ventricular inhibited stimulation, and both were able to work at higher loads with this type of pacing compared with the conventional atrial triggered pulse generator.