bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Chronotropic Response Pattern on Oxygen Kinetics
Authors: DAILEY SHARON M. , BUBIEN ROSEMARY S. , KAY G. NEAL
Published: July 2006

Background: The sinus node is considered to be the model of chronotropic response for pacemakers that use artificial rate modulating sensors. Maximal metabolic exercise testing with measurement of oxygen consumption (VO2) is frequently used to evaluate chronotropic response. Since activities of daily living are generally transient and involve submaximal effort, maximal exercise testing may not provide the most clinically relevant method of assessing rate modulation. The purpose of this study was to determine if an abrupt increase in heart rate (HR) at the onset of submaximal exercise provides improved oxygen kinetics compared with a linear response. Methods and Results: Thirteen patients with complete heart block and permanent rate modulating pacemakers implanted following catheter ablation of the atrioventricular junction for refractory atrial fibrillation were chosen for study. The patients first completed a maximal treadmill exercise test using the chronotropic assessment exercise protocol with breath‐by‐breath analysis of expired gases. The expected HR at 50% of metabolic reserve was calculated for each patient. Three submaximal constant workload exercise tests were then performed at 50% of each patient's metabolic reserve, with the pacemaker randomly programmed to provide three different patterns of chronotropic response: linear (in which HR increased from 70 beats/min to the expected HR at 50% of metabolic reserve), fast(in which HR was abruptly increased to the expected HR at 50% of metabolic reserve), and slow (VVI at 70 beats/ min). Oxygen kinetics were compared for the three patterns of chronotropic response. Cumulative oxygen (O2) consumption was significantly greater for the fast pattern (3610 mL) as compared with the linear (3487 mL, P = 0.004) or slow pattern (3277 mL). The O2 deficit was lower for the fast (361 ± 139 mL) than for the linear (539 ± 225 ml, P = 0.003) or slow chronotropic pattern (559 ± 194). Similar improvements in the rate constant of O2 uptake and Borg perceived exertion scores were observed with the fast chronotropic response pattern. Conclusion: A rapid increase in pacing rate at the onset of exercise improves oxygen kinetics and results in less perceived exertion as compared to a more gradual rate increase that is more characteristic of sinus node behavior.
Why Is Catheter Ablation Less Successful than Surgery for Treating Ventricular Tachycardia that Results from Coronary Artery Disease?
Authors: BLANCHARD SUSAN M. , WALCOTT GREGORY P. , WHARTON J. MARGUS , IDEKER RAYMOND E.
Published: July 2006

Nearly 80% of patients with coronary artery disease who have map‐directed surgery for control of ventricular tachycardias require no drug therapy to prevent recurrences, while fewer than 50% of patients undergoing catheter ablation have similar outcomes. Catheter ablation will fail if arrbythmogenic sites are incompletely ablated by lesions that are too small or too far away from the reentrant pathway or if all arrbythmogenic sites are not identified. The underlying assumptions used to guide site selection are that: (a) ventricular tachycardias arise from reentrant mechanisms; (b) monomorphic ventricular tachycardias with similar QRS morphologies arise from the same pathway; (c) the ventricular tachycardia initiated during the procedure represents the patient's spontaneous arrhythmia; (d) the endocardial site that should be ablated can be identified from cardiac activation maps produced during induced ventricular tachycardia or from ancillary techniques; and (e) the patient has only one or two reentrant pathways. Relying on incorrect assumptions may account for the difference in success rates. Patients may have similar appearing ventricular tachycardias that arise from different pathways, and the entire thin layer of viable tissue between the infarct and the endocardium may contain many reentrant pathways. Some ventricular tachycardias may arise from the myocardium away from the endocardium, while others may arise from the epicardium. Small lesions may not be large enough to eliminate all possible reentrant pathways. Catheter ablation may be less successful because the lesions are inadequate, the assumptions guiding the selection of arrhythmogenic tissue are incorrect, or all arrhythmogenic sites are not identified. The primary reason catheter ablation is less successful than surgery in the treatment of ventricular tachycardias is that catheter ablation does not ablate as much tissue as is removed by surgery. The success rate of catheter ablation probably can be improved if the amount of tissue ablated is increased.
Percutaneous Removal of Infected Permanent Pacemaker Leads Using a Simple Coaxial Dilating System
Authors: HAGER W. DAVID , BROWN LOUIS , RAMSBY GALE
Published: July 2006

A simple traction‐countertraction technique using common and readily available materials was successfully used to remove infected pacemaker leads from two patients. The specific methodology is presented. Although somewhat technically demanding, this approach appears safe and cost‐effective. This method provides another way to remove pacemaker leads without resorting to thoracotomy.
Cerebral Embolism Due to Left Ventricular Pacemaker Lead: Removal with Cardiopulmonary Bypass
Authors: LIEBOLD ANDREAS , AEBERT HERMANN , MUSCHOLL MICHAEL , BIRNBAUM DIETRICH E.
Published: July 2006

Malposition of a cardiac pacemaker lead within the left ventricle represents a source of early and late thromboembolic complications. We report a case of cerebral embolism, caused by an inadvertently misplaced left ventricular electrode, occurring 3 years after implantation. The lead was removed via a transaortic approach with extracorporeal circulation.
Low Dose Disopyramide Often Fails to Prevent Neurogenic Syncope During Head‐Up Tilt Testing
Authors: KELLY PATRICIA A. , MANN DAVID E. , ADLER STUART W. , FUENZALIDA CHARLES E. , REITER MICHAEL J.
Published: July 2006

Low dose disopyramide has been used to prevent neurally‐mediated syncope during head‐up tilt testing but a correlation between blood levels and efficacy has not been described. We measured disopyramide levels in 15 patients with recurrent syncope and positive 70° head‐up tilt tests who underwent one or more repeat tests on the drug. There were 9 males and 6 females, age range 15–78 years. Fourteen of the 15 patients had structurally normal hearts. The daily disopyramide dose was 645 ± 165 mg (mean ± SD). Patients developed syncope during 9 tests and had no syncope during 12 tests. The mean disopyramide level in patients with positive tests was significantly lower than the level in patients with negative tests (2.4 ± 0.15 μ/mL vs 3.2 ± 0.22 μ/mL, P = 0.018). Six patients were tested twice on different disopyramide doses. Five of these six patients had syncope during head‐up tilt testing on the lower dose and negative tests on the higher dose (disopyramide levels 2.2 μ 0.17 μ/mL vs 3.2 μ0.17 fi/mL, P = 0.004). Thus, disopyramide is effective in preventing neurogenic syncope during head‐up tilt testing, but higher blood levels are often necessary for efficacy. In a given patient, failure to respond to low dose disopyramide does not preclude success on higher doses.
Study of Late Potentials and Ventricular Arrhythmias in Hypertensive Patients with Normal Electrocardiograms
Authors: VARDAS PANOS E. , SIMANDIRAKIS EMMANUEL N. , PARTHENAKIS FRAGISKOS I. , MANIOS EMMANUEL G. , ELEFTHERAKIS NIKOLAOS G. , TERZAKIS DIMITRIOS E.
Published: July 2006

Introduction: Although an increase in the occurrence of ventricular arrhythmias has been observed in hypertensive patients, some basic questions remain unresolved regarding the prevalence and the pathophysiology of these arrhythmias. The basic aims of this study were as follows: (1) to examine the incidence and severity of ventricular arrhythmias in a substantial number of hypertensive patients without electrocardiographic indications of hypertrophy; and (2) to examine the correlation between late potentials, hypertrophy, and ventricular arrhythmias in these patients. Materials and Methods: We studied 78 consecutive patients (31 men, 47 women), aged 60.5 ± 7.8 years, with a history of hypertension but a normal electrocardiogram. All patients had an echocardiographic study, 24‐hour ambulatory monitoring, exercise test, and signal‐averaged electrocardiogram. The latter was analyzed using a 40‐to 250‐Hz filter and with a noise level ± 0.3 μV. Results: Of the 78 patients studied, 21 (26.9%) had severe ventricular arrhythmias, while 57 (73.1 %) had either no ventricular ectopics or sporadic isolated ventricular extrasystoles. Left ventricular hypertrophy, defined by echocardiography, was found in 58 patients (74.3%), of which 16 (27.58%) had severe ventricular arrhythmias. Five (25%) of the 20 patients without hypertrophy also had severe ventricular arrhythmias (P = NS). Ventricular late potentials were recorded in 19 (24.5%) of the 78 patients. Of these, 11 (57.89%) had severe arrhythmias, while of the 59 patients without late potentials 10 (16.94%) had severe ventricular ectopic activity. Conclusions: In hypertensive patients without electrocardiographic signs of hypertrophy, the higher prevalence of ventricular arrhythmias does not appear to be related to left ventricular hypertrophy but is correlated with the existence of ventricular late potentials.
Differentiation of Beats of Ventricular and Sinus Origin Using a Self‐Training Neural Network
Authors: EVANS STEVEN J.L. , HASTINGS HAROLD , BODENHEIMER MONTY M.
Published: July 2006

Despite advances in the computerized detection of arrhythmias, arrhythmia recognition by morphological waveform analysis still poses a difficult problem. Artificial neural networks, computer algorithms that are self‐trained by an analog of biological synaptic modification to perform pattern recognition, hold great promise for the differentiation of various cardiac rhythms. The goal of this study was to differentiate beats of sinus and ventricular origin on a global basis and on a patient‐specific basis by the use of artificial neural network analysis. Neural networks were trained to recognize digitized intracardiac electrograms (9 patients) and surface electrocardiograms (11 patients) obtained during sinus rhythm and ventricular tachycardia. After training, sinus rhythm or ventricular tachycardia beats were input into the neural network, and classified as to their origin. By the use of modified receiver operating characteristic curve plots, it was possible to differentiate with high sensitivity and specificity between beats of sinus origin and ventricular origin in all patients. The addition of high amounts of noise to the beats did not markedly degrade the performance of the surface ECG neural networks, and still allowed high sensitivity in differentiating beats of sinus origin from beats of ventricular origin, especially when noise was added to the training set. Neural networks provided sensitive and specific detection of cardiac electrical activity during sinus rhythm and ventricular tachycardia, and may play an important role in allowing development of improved arrhythmia recognition and management systems.
Histopathological Changes Following Laser Ablation of a Left‐Sided Accessory Pathway in a Human
Authors: MEHTA DAVENDRA , BHARATI SAROJA , LEV MAURICE , SAKSENA SANJEEV
Published: July 2006

Laser ablation was performed intraoperatively in a patient with coronary artery disease and Wolff‐Parkinson‐White syndrome. Histopathological evaluation of the laser ablation site revealed a transverse laser incision in the left atrial septum and mitral valve annulus. There was hemorrhage in the atrioventricular (AV) groove with interruption of a posterolateral AV connection. The laser lesion was confined largely to the atrial aspect of the AV annulus. We conclude that laser catheter ablation of accessory pathways is feasible in humans.
A New Method for Diagramming Pacemaker Electrocardiograms
Authors: HESSELSON AARON B. , PARSONNET VICTOR
Published: July 2006

Advancements in technology have made paced ECG interpretation increasingly difficult. A new method for depicting the complex pacemaker/heart interactions that eliminates the extensive use of symbols and repetitious use of refractory period and rate limit information of previous methods has been devised. The method uses a framework of parallel horizontal lines drawn on grid paper underneath the ECG. The lines are spaced apart by the actual programmed values (lower rate, AV, VA intervals) of the pacemaker in question. This framework allows the simultaneous use of the horizontal and vertical directions for the diagram of pacemaker timing intervals. Also, a single representation of refractory periods, upper rate intervals, and other variables can be labeled vertically and extrapolated horizontally across the entire diagram. Single chamber, dual chamber, and rate‐modulated ECGs are readily represented. The diagram is easily plotted on standard ECG paper and flexible enough to represent complex ECGs.
Rate Modulated Pacing Based on Right Ventricular dP/dt: Quantitative Analysis of Chronotropic Response
Authors: KAY G. NEAL , PHILIPPON FRANçOIS , BUBIEN ROSEMARY S. , PLUMB VANCE J.
Published: July 2006

Right ventricular contractility increases in response to catecholamine stimulation and greater ventricular preload, factors that increase with exercise workload. Thus, the maximum systolic dP/dt may be a potentially useful sensor to control the pacing rate of a permanent pacing system. The present study was designed to test the long‐term performance of a permanent pacemaker that modulates pacing rate based on right ventricular dP/dt and to quantitatively analyze the chronotropic response characteristics of this sensor in a group of patients with widely varying structural heart diseases and degrees of hemodynamic impairment. A permanent pacing system incorporating a high fidelity pressure sensor in the lead for measurement of right ventricular dP/dt was implanted in 13 patients with atrial arrhythmias and AV block, including individuals with coronary artery disease, hypertension, severe obstructive pulmonary disease with prior pneumonectomy, atrial septal defect, dilated cardiomyopathy, restrictive cardiomyopathy, and mitral stenosis. Patients underwent paired treadmill exercise testing in the VVI and VVIR pacing modes with measurement of expired gas exchange and quantitative analysis of chronotropic response using the concept of metabolic reserve. The peak right ventricular dP/dt ranged from 238–891 mmHg/sec with a pulse pressure that ranged from 19–41 mmHg. There was a positive correlation between the right ventricular dP/dt and pulse pressure (r = 0.70, P = 0.012). The maximum pacing rate and VO2max were 72 ± 6 beats/min and 12.61 ± 4.0 cc O2/kg per minute during VVI pacing and increased to 124 ± 18 beats/min and 15.89 ± 5.9 cc 02/kg per minute in the VVIR pacing mode (P < 0.0003 and P < 0.002, respectively). The integrated area under the normalized rate response curve was 96.7 ± 45.7% of expected during exercise and 100.1 ± 43.4% of expected during recovery. One patient demonstrated an anomalous increase in pacing rate in response to a change in posture to the left lateral decubitus position. Thus, the peak positive right ventricular dP/dt is an effective rate control parameter for permanent pacing systems. The chronotropic response was proportional to metabolic workload during treadmill exercise in this study population with widely varying forms of structural heart disease.
Relation Between Cycle Length, Volume, and Pressure in Type I Atrial Flutter
Authors: VULLIEMIN PIERRE , DEL BUFALO ALESSANDRO , SCHLAEPFER JURG , FROMER MARTIN , KAPPENBERGER LUKAS
Published: July 2006

Assuming that type I atrial flutter is a macroreentrant circuit, its cycle length should vary with the atrial dimensions. In order to test this hypothesis, flutter cycle length was measured while inducing atrial volume and pressure changes by postural and pharmacological means in seven patients undergoing a therapeutic programmed stimulation for type 1 atrial flutter conversion. Right atrial volume was estimated from B‐mode echocardiography data. Basal values were compared with those obtained during inspiration, expiration, Valsalva maneuver, negative tilt (head down), and positive tilt (head up) with 0.8–1.6 mg p.o. nitroglycerin. The right atrial size increased slightly from 17.8 to 18.3 cm2 (P = 0.04) during the pressure load induced by negative tilt (+ 3 mmHg), with a corresponding lengthening of the flutter cycle length from 228 to 233 msec (P = 0.02). Similarly, pressure unloading of ‐2 mmHg by positive tilting and nitrates was accompanied by a decrease in right atrial size to 16.6 cm2 (P = 0.04), with a corresponding decrease in cycle length from 228 to 219 msec (P = 0.03). Respiratory maneuver yielded similar results with an inspiratory cycle lengthening, expiratory shortening, and further shortening during Valsalva maneuver. These experiments demonstrate a direct relation between cycle length and atrial volume in human type I atrial flutter. They underline the importance of the right heart preload and atrial size for the electrophysiological characteristics of type I atrial flutter. Beside its fundamental interest, this finding is important for the understanding of the mechanism of maintenance and therapeutic responses of this common arrhythmia.
Idiopathic Ventricular Fibrillation in Out‐of‐Hospital Cardiac Arrest Survivors
Authors: TUNG ROBERT T. , SHEN WIN‐KUANG , HAMMILL STEPHEN G. , GERSH BERNARD J.
Published: July 2006

This study examined diagnostic and therapeutic roles of electrophysiological testing and long‐term clinical outcome after out‐of‐hospital cardiac arrest due to idiopathic ventricular fibrillation. This is defined as ventricular fibrillation occurring in the absence of detectable underlying heart disease or metabolic or electrolyte disturbance. Out‐of‐hospital cardiac arrest resulting from idiopathic ventricular fibrillation is uncommon. Records of all patients who underwent electrophysiological testing between June 1979 and June 1992 were reviewed. Patients with out‐of‐hospital cardiac arrest due to idiopathic ventricular fibrillation were identified. Follow‐up information was obtained by telephone interview in June 1992. Of 194 patients who underwent electrophysiological study after out‐of‐hospital cardiac arrest not associated with acute myocardial infarction, only six (4 male and 2 female) had idiopathic ventricular fibrillation. It was induced in only two patients by programmed ventricular stimulation. No sustained ventricular arrhythmias were induced in the remaining four patients. Four patients received implantable cardioverter defibrillators, one was treated with a β‐adrenergic blocker, and one received no treatment. All patients were alive at a mean follow‐up of 50 months. Two of the four patients without inducible sustained ventricular arrhythmias had events during follow‐up. Of the two patients with inducible ventricular fibrillation, one experienced a cardiac arrest and documented ventricular fibrillation at 41 months after the index event and the other had had no recurrence at 15‐month follow‐up. All four patients with implantable cardioverter defibrillators were alive at last follow‐up, and two had device discharges. In survivors of out‐of‐hospital cardiac arrest due to idiopathic ventricular fibrillation: (1) programmed electrical stimulation is of limited value for evaluating cause and guiding therapy; (2) a high rate of recurrent events is observed (50%); and (3) an implantable cardioverter defibrillator is effective for preventing a fatal outcome.
A Technique for Rapid Transfemoral Catheterization of the Coronary Sinus with Multielectrode Catheters
Authors: KLEMAN JAMES M. , PINSKI SERGIO L. , STERBA RICHARD , KIDWELL GREGORY A. , TROHMAN RICHARD G.
Published: July 2006

To minimize procedural and fluoroscopic times and avoid the risks of vascular injury and pneumothorax, some investigators have advocated elimination of routine placement of a coronary sinus (CS) catheter during electrophysiological procedures. We hypothesized that expedient and reproducible CS catheterization could be performed with minimal patient risk by utilizing a femoral vein approach. Fifty consecutive patients referred for radiofrequency ablative procedures underwent attempted CS catheterization using a 6‐French steerable, quadripolar catheter via a femoral vein. Procedures were performed utilizing single‐plane fluoroscopy without contrast angiographic aid by operators experienced in the technique. Successful catheterization was defined by the attainment, in < 15 minutes, of a stable catheter position with the distal electrode at or beyond the lateral margin of the heart. Successful catheterization of the CS was achieved in 47 (94%) patients. Selective pacing of the left atrium without patient discomfort was possible in all, eliminating the need for a right atrial pacing catheter. The median time to successful catheterization was 1.4 minutes (range 0.3–14.7). Only six patients required > 5 minutes. The median fluoroscopic time required was 1.2 minutes (range 0.3–12.7). No clinical variable was predictive of catheterization failure or time to successful catheterization. No complications were observed as a result of this technique. This prospective evaluation demonstrates that catheterization of the CS via a femoral vein approach is highly successful, expedient, and safe. The ability to selectively pace the left atrium may eliminate the requirement for a right atrial catheter.
Experience with Two Different Nonthoracotomy Systems for Implantable Defibrillator in 170 Patients
Authors: SRA JASBIR S. , NATALE ANDREA , AXTELL KATHI , MAGLIO CHERYL , JAZAYERI MOHAMMAD , DESHPANDE SANJAY , DHALA ANWER , BLANCK ZALMEN , AKHTAR MASOOD
Published: July 2006

Implantation of a nonthoracotomy system (Medtronic PCD or CPI Endotak) was attempted in 170 patients with ventricular tachycardia (VT) or ventricular fibrillation (VF) not requiring concomitant cardiac surgery. A nonthoracotomy system could be successfully implanted in 95 of the 115 patients with the PCD system and 49 of 55 patients receiving the Endotak lead system. In 26 patients with failed nontboracotomy system because of defibrillation threshold (DFT) > 25 joules (J), an epicardial system was implanted at the same setting. Patients receiving the two lead systems were comparable with regard to age, sex, and ejection fraction. However, since tbe PCD system offers tiered therapy multiprogrammable options, all attempts were made to implant tbis lead system in patients with VT that could be pace terminated. Mean DFT(15 ± 4.7 vs 17 ± 4.6 J;P = 0.03) and implant time (2.5 ± 0.6 vs 3.3 ± 0.7 hours; P = 0.02) were less with the Endotak lead system. There was no perioperative mortality. During a mean follow‐up of 20 ± 4 months, there were eight instances of lead dislodgment in patients receiving the PCD system. Tbere were four nonsudden cardiac deaths and one sudden death in the Endotak group and three nonsudden deaths in the PCD group. Sudden cardiac death and total survival using the intention‐to‐treat analysis during this follow‐up period were 99% and 95%, respectively. In conclusion, successful implantation, perioperative mortality, and survival rate are comparable with both lead systems; however, incorporating two defibrillating electrodes in one lead minimizes lead dislodgment and reduces implant time.
Stimulation Characteristics, Complications, and Efficacy of Spinal Cord Stimulation Systems in Patients with Refractory Angina: A Prospective Feasibility Study
Authors: de JONGSTE MIKE J.L. , NAGELKERKE DICK , HOOYSCHUUR CARLA M. , JOURNEE HENRICUS L. , MEYLER PIM W.J. , STAAL MICHIEL J. , de JONGE PIETER , LIE K.I.
Published: July 2006

Objectives: In a prospective study with a 1‐year follow‐up we evaluated: (1) the feasibility of a method for the adjustment of spinal cord stimulator (SCS) parameters, (2) complications of SCS, and (3) efficacy of SCS. Methods: In patients receiving an SCS for severe angina unresponsive to standard therapies, SCS characteristics were evaluated within 1 week and at 4, 14, 26, and 52 weeks after SCS treatment. Step‐by‐step adjustment of pulse output parameters was performed at the electrode configuration at which paresthesias occurred (‘sensory threshold”), covered the anginal area (“adjusted setting”), or provoked pain (“motor threshold”). In addition, the number of anginal attacks and intake of glyceryl trinitrate (GTN) tablets were recorded at regular intervals. Results: Twenty‐two patients with either a bipolar (14) or a unipolar (8) system were evaluated. In the 14 patients with bipolar systems, alteration in paresthesias required 26 reprogrammings of the configuration. In the eight patients with bipolar systems who completed the followup without lead dislocation, the mean “sensory threshold” was 3.3 V (1.7–5.6), the mean “adjusted stimulation” output was 4.5 V (2.8–7.6), and the mean “motor threshold” was 4.9 V (2.8–7.7) after 4 weeks SCS. The mean stimulation duration per 24 hours was 14.1% (5%–24%), and the mean standardized impedance was 821 Ω (748–893) after 4 weeks SCS. The unipolar group demonstrated comparable results. After 1‐year follow‐up the parameters had not changed significantly. During the 1‐year follow‐up, 6 of 22 patients experienced lead dislocation that required surgery. In all patients, anginal attacks (P < 0.003) and GTN intake (P < 0.005) were reduced significantly with SCS. The effect lasted during the 1 year. Conclusions: During a 1 ‐year follow‐up, the stimulation parameters did not change significantly in the 16 patients without lead dislocations. Our standardized method appears to be feasible for follow‐up of SCS. Moreover, SCS seems to be an effective adjuvant therapy for intractable angina, despite a relatively frequent dislocation of the electrode.
Radiofrequency Catheter Ablation of a Concealed Accessory Atrioventricular Pathway After Heart Transplantation
Authors: NEUZNER JÖRG , FRIEDL A. , PITSCHNER H.F.
Published: July 2006

Three months after orthotopic cardiac transplantation, a 46‐year‐old man developed paroxysmal supraventricular tachycardia. Electrophysiological investigation of the arrhythmia led to the diagnosis of an atrioventricular reentrant tachycardia involving a left lateral concealed accessory pathway. When antiarrhythmic drugs failed to suppress the arrhythmia, radiofrequency catheter ablation of the accessory pathway was performed without complication.
Migration of an Epicardial Pacemaker to the Pericardial Space in an Infant
Authors: VAN HARE GEORGE F. , WITHERELL CHARLES , MERRICK SCOT M.
Published: July 2006

We report the case of a 4‐month‐old infant who was implanted with an epicardial ventricular pacing system at 6 days of age for the prolonged QT syndrome, who subsequently developed migration of the pulse generator to the pericardial space. Tracking of the pulse generator through the diaphragm and into the pericardium followed the route of the myocardial lead. The possibility of pulse generator migration, as well as disruption of the diaphragm and pericardium, should be considered by those who care for infants with implanted pacemakers.
Differentiation of Sinus Tachycardia From Ventricular Tachycardia with 1:1 Ventriculoatrial Conduction in Dual Chamher Implantable Cardioverter Defibrillators: Feasibility of a Criterion Based on the Atrioventricular Interval
Authors: LeCARPENTIER GERALD L. , BAGA JOHN J. , YANG HUA , STEINMAN RUSSELL T. , MEISSNER MARC D. , LEHMANN MICHAEL H.
Published: July 2006

Tachycardia discrimination in future implantable cardioverter defibrillators (ICDs) is likely to be enhanced by the addition of an atrial sensing/pacing lead. However, differentiation of sinus tachycardia (ST) from ventricular tachycardia (VT) with 1:1 VA conduction will remain problematic. We assessed the use of the AV interval as a potential criterion for correctly differentiating ST from VT. Incremental V pacing at the right ventricular (HV) apex served as a “VT” model in each of 41 patients with 1:1 VA conduction to pacing cycle lengths ≤ 450 msec. High right atrial and RV apical electrograms during normal sinus rhythm (NSR) and during incremental V pacing were digitized (simulating ICD sensing). From these signals, AV interval versus pacing cycle length plots were computer generated to identify crossover cycle lengths, each defined as the cycle length at which the AV interval during V pacing equals the AV interval during NSR. At cycle lengths longer than the crossover value, the AV interval during “VT” exceeds the AV interval during NSR. In contrast, the AV interval during ST is physiologically shorter than the AV interval during NSR. Thus, ST can be readily differentiated from “VT” over a range of cycle lengths greater than the crossover value. The overall mean calculated crossover cycle length was 371 ± 52 msec. In 11 patients paced multiple times, each crossover cycle length was reproducible (mean coefficient of variation was 1.2%± 0.9% per patient). AV intervals measured at the RV apex were also analyzed with incremental V pacing during catecholamine stimulation (isoproterenol, n = 5) and during alternate site “VT” (RV outflow tract [n = 8] and left ventricle [n = 2]). In all these cases, the new “VT” plots of AV interval versus pacing cycle length coincided with or fell to the left of those obtained during control RV apical pacing and recording (i.e., these AV interval values crossed the NSR baseline at cycle lengths ≤ the crossover cycle length). Thus, the cycle length range for recognizable differentiation of ST from “VT” remained valid. The data suggest that the described AV interval criterion relying on the crossover cycle length: (1) is a promising approach to improve differentiation of ST from relatively slow VTs with 1:1 VA conduction, and (2) can readily be automated in future dual chamber ICDs, given its computational simplicity.
Quality‐of‐Life in DDDR Pacing: Atrioventricular Synchrony or Rate Adaptation?
Authors: LAU CHU‐PAK , TAI YAU‐TING , LEE PETER W.H. , CHEUNG BEN , TANG MAN‐OI , LAM WAH‐KING
Published: July 2006

Al though differences in exercise performance have been observed between different rate adaptive modes, the relative impact of atrioventricular (AV) synchrony and rate adaptation on quality of life (QOL) have not been determined. Thirty‐three patients with either sinoatrial disease (18) or complete atrioventricular (AV) block (15) received DDDR pacemakers (16 minute ventilation sensing, 17 activity sensing). There were 11 males and 22 females, with a mean age of 66 ± 1 (range 39–78) years. The study was a double‐blind, triple cross‐over study comparing DDDR, DDD, and VVIR modes. At the end of each 8‐week study period in each mode, QOL was assessed by a questionnaire evaluating patients' functional class (Classes I‐IV), physical malaise inventory (41 items), illness perception (43 items), and overall QOL rating based on a 48 items measure covering different aspects of the patients' daily life adjustment. Two patients required early crossover from VVIR mode during the study. Patients experienced significantly fewer physi cal malaise such as temperature intolerance, dyspnea, and palpitations in the DDDR mode, compared with either DDD or VVIR pacing. DDDR pacing reduced the perception of illness in 5 of 43 items compared to VVIR pacing, and improved stamina and appetite compared to DDD pacing. The overall QOL score was 102 ± 2, 105 ± 2, 113 ± 2 in the DDDR, DDD, and VVIR modes, respectively, with a higher score indicating a poorer QOL (DDDR/DDD vs VVIR, P < 0.02). There was no change in functional classes between the three pacing modes. In conclusion, VVIR pacing has a lower QOL compared with DDD pacing, which can be further enhanced with rate augmentation.
A New Dual Chamber Single Lead System
Authors: HIRSCHBERG JAKUB , EKWALL CHRISTER , STRANDBERG HANS , CARLSTEN JOHAN , BOWALD STAEFAN
Published: July 2006

A DDD pacing system normally requires the introduction and positioning of two separate electrode leads. A VDD system may use a single lead with a ventricular electrode at the tip and at least one atrial ring electrode. The disadvantage of VDD systems is that the full range of DDD stimulation and detection alternatives is not available. The present animal study was made to evaluate a new single lead design with the distal electrode placed in the atrium and the proximal ring electrode in the right ventricle. This design permits the full range of DDD options including atriai stimulation. Acute stimulation thresholds and sensing amplitudes were stable and comparable to conventional DDD systems. Long‐term studies are on‐going.
A New Pacemaker for Paroxysmal Atrial Fibrillation Treated with Radiofrequency Ablation of the AV Junction
Authors: BRIGNOLE MICHELE , GIANFRANCHI LORELLA , MENOZZI CARLO , BOTTOM NICOLA , BOLLINI ROBERTO , LOLLI GINO , ODDONE DANIELE , GAGGIOLI GERMANO
Published: July 2006

Atrial fibrillation is a relative contraindication to atrial synchronous pacing because of the risk of the tracking of rapid atrial rhythms by the pacemaker. In this study, we describe the clinical results of an AV synchronous rate responsive pacemaker with an original algorithm, which is able to sense pathological increments in atrial rate and automatically to switch into a non‐AV synchronous mode of pacing. This pacemaker was implanted in 12 patients who had undergone radiofrequency ablation of the A V junction in order to cure severely symptomatic, drug refractory, paroxysmal atrial fibrillation. In an acute, intrapatient comparison between the standard AV synchronous mode and the automatic switching mode, ventricular tracking of atrial fibrillation occurred in 35% and 4% of total beats at rest and in 24% and 2% of total beats during exercise, respectively (P < 0.001). During 5 ± 4 months of follow‐up, no further tachyarrhythmia related symptoms occurred. In conclusion, the standard DDDR mode is unable to eliminate ventricular tracking of atrial fibrillation, thus undermining the efficacy of AV junction ablation therapy. The automatic switching mode eliminates this adverse effect of dual chamber pacing.
A New Automode Switch Algorithm for Supraventricular Tachycardias
Authors: LEVINE PAUL A. , BORNZIN GENE A. , BARLOW JEFFREY , FLORIO JOSEPH , SHOLDER JASON , TYLER JIM , MANN BRIAN
Published: July 2006

Patients with complete heart block on a spontaneous, or iatrogenic basis who also have recurrent supraventricular tachycardias, particularly atrial fibrillation and flutter, are often difficult to manage. Various techniques include: independently programmable maximum tracking and maximum sensor rates, limiting the maximum atrial tracking rate to the sensor response of the pacemaker, or automatically switching from DDDR to VVIR based upon the sensed atrial rate. This article will describe a mode switch algorithm that allows for an independently programmable atrial tachycardia detection rate (ATDR). This allows mode switching to occur only in response to the patient's pathological tachyarrhythmia, and not during normal upper rate response. The ATDR is based upon a filtered atrial rate, which will prevent an isolated premature beat from initiating the algorithm. In addition, the unit can be programmed to switch to either DDI, DDIR, VVI, or VVIR. Extensive event counters in the pulse generator allows the system to record and store the number of algorithm activations, the average atrial rate which triggered each mode switch, and the duration of the mode switch. These reports are accessible at each follow‐up visit.
Quantitative Comparison of Rate Response and Oxygen Uptake Kinetics Between Different Sensor Modes in Multisensor Rate Adaptive Pacing
Authors: LEUNG SUM‐KIN , LAU CHU‐PAK , WU CHE‐WO , LEUNG WING‐HUNG , TAI YAU‐TING , LEE IRIS , CHOW YUEN‐HA
Published: July 2006

Although multisensor pacing may mitigate the inadequacy of rate adaptation in a single sensor system, the clinical role of multisensor driven rate adaptive pacing remains unclear. The cardiopulmonary performance of six patients (mean age 63.5 ± 10 years) who had undergone the implant of combined QT and activity VVIR (Topaz®) pacemakers was assessed during submaximal and maximal treadmill exercise with the rate response sensor randomly programmed to either single sensor mode. QT and activity (ACT), or dual sensor mode, with equal contribution of QT and ACT (QT = ACT). The rate of response, the proportionality, oxygen kinetics, and maximal exercise performance of the various sensor modes during exercise were measured and compared. The ACT sensor mode “overpaced” and the QT and QT = ACT sensor modes “underpaced” during the first three quartiles of exercise (P < 0.05). The ACT sensor mode also gave the fastest rate of response with the shortest delay (13 ± 1.5 sec vs 145 ± 58 sec and 41 ± 17 sec, P < 0.05), time to 50% rate response (39 ±2.7 sec vs 275 ± 48 sec and 203 ± 40 sec, P < 0.05), and time to 90% of rate response (107 ± 21 sec vs 375 ± 34 sec and 347 ± 34 sec, P < 0.05) and a smaller oxygen debt (0.87 ± 0.16 L vs 1.10 ± 0.2 L and 1.07 ± 0.18 L, P < 0.05) compared to the QTand QT = ACT sensor modes, respectively. These differences were most significant at low exercise workloads. Thus, different sensor combinations resuh in different rate response profiles and oxygen delivery, especially during low level exercise. However, the observed oxygen kinetics difference was workload dependent, and its clinical relevance remains to be tested. Despite the marked difference in exercise rate profile and oxygen kinetics, there was no difference in the maximal oxygen uptake, anaerobic threshold, and exercise duration between the various sensor modes during maximal exercise.
A Rate Responsive Pacemaker that Physiologically Reduces Pacing Rates at Rest
Authors: MORRIS‐THURGOOD JAYNE , CHIANG CHIH‐MING , ROGHELLE JULIE , STEINHAUS BRUCE , ILSLEY CHARLES , PAUL VINCENT
Published: July 2006

Current rate responsive pacemakers incorporate sensors such as minute ventilation (MV) for adapting to changing patient conditions during exercise and periods of exertion. However, for sleep and/or rest periods, the only pacemakers currently on the market that slow the pacing rate utilize an internal timer to determine a decrease in pacing rate. It would be advantageous if the pacing rate could be automatically lowered during periods of sleep or rest. This study utilized a rate responsive sensor, MV, to track the patient's sleeping and resting periods and to decrease the pacing rate at such times. A total of eight patients implanted with Sentri 1210 single chamber MV sensor pacemakers were studied. A sleep rate (SH) of 45 beats/min was selected. A sleep rate response function, which indicated the relationship between changes in MV and corresponding heart rate, was initially set at a value of 16 and continually and automatically updated in a 3‐month study. Adaptation was based on the premise that 3 hours per day should be spent at the SR. The average decrease in pacing rates from onset to 3 month for the eight patients was 12.4%± 5.3%. Correspondingly, the histograms of the lowest datalog histogram (40–59 beats/min) increased from 0% to 15.4%± 0.9% of paced beats. Correlation between the patients' 24‐hour diary and Holter recordings showed that the pacing rates during sleep were consistently lower than when the patients were awake and active. This was also the case with a patient whose nocturnal and daily routine was intentionally altered. In conclusion, the MV sensor has shown to be an accurate sensor for the automatic determination of periods of sleep or rest. Data demonstrates that the decreased average pacing rate will increase pacer longevity as well as potentially provide more physiological pacing rates at night.
Oxygen Pressure as Biosensor for Rate Adaptive Cardiac Pacing
Authors: CARLSTEN JOHAN , HOLMSTRÖM NILS , HAGEL PIA
Published: July 2006

A new carbon based oxygen sensor for rate adaptive cardiac pacing has been developed. It measures oxygen partial pressure In mixed venous blood. The system was implanted in six sheep with a mean follow‐up time of 261 days after implant. The sensor reacted in a physiological manner when the animals were at rest as well as during exercise. Long‐term sensor stability and sensitivity were satisfactory, and we found excellent correlation with spontaneous heart rate variations and with oxygen saturation measurements. The sensor shows great promise although our experience is still limited and further development on the concept is on‐going.
Clinical Evaluation of a Dual Sensor, Rate Responsive Pacemaker
Authors: SINHA SANJAY , SCHILLING RICHARD J. , KAYE GERRY C. , CAPLIN JOHN L.
Published: July 2006

Dual sensor pacemakers should respond more appropriately during differing exercise modes than a single sensor device. The Topaz™ models 515 (QT and activity count [ACT] sensing) pacemaker shows appropriate rate response during treadmill exercise testing. We postulated that adjustments to relative sensor contribution should allow fine tuning of the onset of rate response. Eleven patients with this pacemaker were studied. Three standard exercise tests were performed with adjustment of sensor blending and activity threshold between each one. We also assessed the response to isometric exercise and a false positive activity signal. Results: Times to 100 ppm (3.7 ± 1.3, 4.4 ± 2.0, 5.3 ±1.5 mins), times to peak rate (6.1 ± 1.6, 5.6 ± 1.4, 6.5 ± 1.3 mins) and accelerations to peak (9.0 ± 2.4, 9.2 ± 5.3, 7.7 ± 2.8 ppm/min) were measured in all three different sensor settings (QT = ACT, QT <ACT, and QT = ACT with decreased activity threshold). No significant difference in onset of rate response was seen between the three settings. Tapping (false‐positive activity) provided a rapid rise in paced rate to 79 ppm from a resting value of 65 ppm. This came down to 71 ppm demonstrating satisfactory sensor cross‐checking. Isometric exercise induced a moderate response from 65 ppm at rest to 74 ppm after 3 minutes. Conclusions: Satisfactory rate response was demonstrated in most patients to treadmill testing and to isometric exercise. However, small adjustments to relative sensor contributions do not predictably alter the onset of rate response.
Stepwise Analysis of the Calibration Procedure of an Accelerometer‐Based Pacemaker
Authors: MAHAUX VÉRONIQUE A. , VERBOVEN YVES J. , WALEFEE ANDRE , KULBERTUS HENRI
Published: July 2006

The rate modulation of Relay™ 294–03 is individually adjusted during a 3‐minute calibration test corresponding to the collection of moderate acceleration signals (MAL), which are related to a programmable moderate pacing rate (PR). Those rate/acceleration values form a calibration point in the flat part of the rate response curve (HRC). To help in a more clinically oriented analysis of this feature, the stimulator was first calibrated while strapped on a volunteer who remained seated (low MAL), walked (medium MAL), or jogged (high MAL). The device was then mechanically submitted to three calibrated to and fro movements corresponding to the sensitivity spectrum of the sensor. Each movement was repeated ten times to test the influence of the slope (1–10). Results: (1) One‐way ANOVA showed a significant effect of the MAL recorded during the calibration test on subsequent rate modulation (P = 0.0001); (2) The sensor amplifier gain was inversely related to the MAL: high MAL induced lower amplifier gain and lower PR for identical accelerations; (3) Lower amplifier gain allowed to discriminate highest acceleration magnitudes before reaching an overflow of the sensor; (4) The maximum achievable PR increased not only with the programmed slope, but also with decreasing MAL (P = 0.0055): a low MAL shifts to the left calibration point located on the part of the RRC and makes the last steep part of the RRC start earlier, thus leading to higher maximum achievable PR. In conclusion the calibration procedure is crucial not only in defining a moderate acceleration intensity but also in determining the sensor amplifier gain and the maximum achievable PR.
A New Pacing Algorithm for Overdrive Suppression of Atrial Fibrillation
Authors: MURGATROYD FRANCIS D. , NITZSCHÉ RÉMI , SLADE ALISTAIR K.B. , LIMOUSIN MARCEL , ROSSET NICOLAS , CAMM A. JOHN , RITTER PHILIPPE ,   for the CHORUS MULTICENTRE STUDY GROUP
Published: July 2006

Constant rapid pacing may suppress arrhythmias, but it is usually poorly tolerated in the long term. We report a pilot study of a new pacing algorithm for overdrive suppression of atrial premature complexes (APCs) and atrial fibrillation (AF), which prevents postextrasystolic pauses and varies the pacing rate in response to the frequency of APCs. The algorithm was tested in a multiple crossover study for 24 hours in dual chamber pacemakers implanted in 70 patients. Comparison was made on ambulatory recordings between the number of atrial arrhythmias commencing with the algorithm active and inactive. In all cases, the algorithm functioned as designed. No patient was aware of its operation, and no malignant arrhythmias were induced. The 36 recordings that showed atrial arrhythmia were included for analysis. The effects of the algorithm were: APCs (estimated from pacemaker statistics) reduced in 18 patients, increased in 8 (P = 0.02); atrial salvos reduced in 12, increased in 4 (P = 0.041); and AF reduced in 11, increased in 8 (P = NS). In all patients with frequent AF (> 5 episodes in total), fewer episodes occurred when the algorithm was active. We conclude that the algorithm is safe and well tolerated, reduces atrial ectopic activity, and may reduce the frequency of sustained atrial fibrillation.
AV Delay Optimization and Management of DDD Paced Patients with Dilated Cardiomyopathy
Authors: GUARDIGLI GABRIELE , ANSANI LUCIA , PERCOCO GIAN FRANCO , TOSELLI TIZIANO , SPISANI PATRIZIA , BRAGGION GABRIELE , ANTONIOLI GIAN ENRICO
Published: July 2006

Ten DDD paced patients, suffering front dilated cardiomyopathy in the NYHA functional classes III or IV were studied by means of Doppler ecbocardiography at different programmed values of atrioventricular (AV) delay (200, 150, 120, 100, and 80 msec). The following variables were evaluated: LV diameter, ejection fraction, mitral and aortic flow velocity integrals, and stroke volume. During VDD pacing, a resting AV delay associated with the best diastolic filling and systolic function was identified and programmed individually. Shortening of the AV delay to about 100 msec was associated with a gradual and progressive improvement. Further decrease caused an impairment of systolic function. The patients were clinically and beinodynamically reevaluated after 2 months of follow‐up. A reduction of NYHA class and an improvement of LV function were consistently found. The reported data suggest that programming of an optimal A V delay may improve myocardial function in DDD paced patients with congestive heart failure. This result may be the consequence of an optimization of left ventricular filling and a better use of the Frank‐Starling law.