bluuebunny/crossref_metadata_2025 huggingface dataset:
Entrainment Onset in a Pacemaker Model of Reentrant Ventricular Tachycardia: Insight into Localization of Critical Elements of a Reentrant Circuit
Authors: KREMERS MARK S. , WELLS PETER J. , BLACK WILLIAM H. , MCBRIDE WADE , ZMIJEWSKI MATT , TAYLOR ANNE L. , ECKELS ROBIN
Published: July 2006

We investigated entrainment in a pacemaker model of reentrant ventricular tachycardia (VT) created in the intact dog heart using a VAT pacemaker with both electrodes on the ventricular epicardium. This produced an incessant wide QRS tachycardia originating from the pacing site with a cycle length equal to the conduction time between the sensing and pacing site plus the pacemaker AV delay. The conduction time between entrainment sites and the critical elements of the reentrant pathway (sensing and pacing sites) was determined by pacing at a comparable cycle length during sinus rhythm. Entrainment was achieved in 12 tachycardias with pacing at 1–4 sites at cycle lengths 30–100 msec shorter than tachycardia and confirmed by constant QRS fusion, progressive QRS fusion, and coupling of the first nonpaced QRS or intracardiac electrogram at the entraining cycle length. By least squares regression, the timing of entrainment onset (first reset of pacing or sensing site electrogram) measured by the prematurity of the local electrogram at the entraining site was highly correlated to the shortest conduction time between the entraining site and the circuit (F value of 84.7 and R = 0.752 [P < 0.001]). Therefore, the timing of entrainment onset maybe useful in predicting the conduction time from the entraining site to critical elements of a reentrant circuit and may assist in localization of the reentrant pathway.
Atrial Automatic Tachycardia‐Reversion Pacemakers: Their Economic Viability and Impact on Quality‐of‐Life
Authors: LI CURTIS K. , SHANDLING ADRIAN H. , NOLASCO MARIA , THOMAS LAVERGNE A. , MESSENGER JOHN C. , WARREN JAY
Published: July 2006

Refractory supraventricular tachyarrhythmias may be both difficult and costly to control medically and can interfere with the patient's lifestyle. Newer treatment modalities are available for their management, and these require comprehensive assessment. We therefore compared costs and selective indices of patient benefit in a group of 17 patients in whom an atrial antitachycardia (Intermedics Intertach 262–12) pacemaker was placed for refractory supraventricular tachyarrhythmias. Prior medical therapy was compared to subsequent automatic antitachycardia pacemaker treatment. The total medical costs (admissions, emergency room visits, office visits, and medication costs) and the number of hospitalizations and medications were compared prior to implantation (F/U 69.3 ± 61 months) and after implantation (F/U 15.3 ± 7.8 months). A detailed quality‐of‐life questionnaire was also obtained 36.6 ± 11 months after implantation. Results: There were significant per patient differences in total cost before and after implantation: monthly costs were $505 ±$833 before pacemaker implantation and $105 ±$117 monthly afterward (P < 0.005). Pacemaker implantation hospitalization costs were $19,063 ±$8,362. Monthly medication costs averaged $46 before versus $15 after implantation (P < 0.01). The number of medication types also differed with an average 5.5 medication types per patient before versus 1.2 after implantation (P < 0.001). There were 8.6 yearly hospital admissions in the whole group before implantation, versus 4.7 admissions in the group per year thereafter. Patients demonstrated significant improvement in 80% of the quality‐of‐life parameters studied. Conclusion: Adjunctive atrial automatic tachycardia‐reversion pacemaker therapy may be cost‐competitive over time when compared to medical therapy alone in patients with refractory supraventricular tachyarrhythmias and appears to improve overall quality‐of‐life.
Therapy Assessment for Sustained Ventricular Tachyarrhythmias: How Many Electropharmacological Tests are Appropriate?
Authors: SCHOELS WOLFGANG , BRACHMANN JOHANNES , HUG RENATE , SCHMITT CLAUS , KUEBLER WOLFGANG
Published: July 2006

Surgery, implantable devices or catheter ablations offer therapeutic choices for the treatment of malignant ventricular tachyarrhythmius (VT) resistant to antiarrhythmic drugs. The number of electropharmacological (EP) tests that should precede consideration of a nonpharmacological therapy has not been defined. We performed serial EP tests in 94 patients with inducible sustained VT until an effective drug was identified or all available drugs had failed to suppress VT induction. With up to 11 tests in individual patients, suppression of VT inducibilify was finally achieved in 66 patients (70%). In 47 of these 66 patients (70%), only one or two tests were necessary to identify an effective regimen. However, in 40%, 28%, 18%, and 9% of the patients still inducible after 2, 3, 4, and 5 drug tests, respectively, an effective agent could be identified during subsequent tests. No critical number of unsuccessful EP tests clearly separated responders and nonresponders to medical therapy. During follow‐up (34 ± 11 months), 14 patients placed on antiarrhythmic drugs predicted to be effective had symptomatic VT recurrence. VT recurrence was unrelated to the type or the number of unsuccessful EP tests preceding identification of the prescribed drug. Extensive EP testing with all available agents might therefore be worthwhile in selected patients. An “appropriate” number of EP studies has to be determined individually for each patient, based on the chance of finding an effective drug during subsequent studies and the risk and benefit of the therapeutic choices.
Stroke Volume and the Three Phase Cardiac Output Rate Relationship with Ventricular Pacing
Authors: WESSALE JERRY L. , VOELZ MARGARET B. , GEDDES LESLIE A.
Published: July 2006

Knowledge of how stroke volume (SV), and hence cardiac output (CO), changes with ventricular pacing rate (R) constitutes a key aspect of sensor driven, variable rate pacemakers. It has been established that the relationship between CO and pacing rate exhibits three phases for rest and constant exercise. At low rates (phase 1), CO increases with increasing R; with additional rate increase (phase 2), CO either remains constant or increases slightly; and above some critical rate, CO decreases (phase 3). However, the nature of the relationship between SV and pacing rate has not been as clearly described. Therefore, the objectives of this study were (1) to describe and document the relationship between SV and R, and (2) to demonstrate the consequence of this relationship in terms of the three phase CO versus R relationship. In six anesthetized dogs, right ventricular SV was determined from pulmonary artery blood flow measured using an electromagnetic flow meter, and the right ventricle was paced over a range of rates. In general, SV decreased with increasing R, although the exact nature of the relationship varied from animal to animal. The results demonstrate that it is the manner in which SV decreases with increasing R that determines the three phase relationship between CO and R. The relationships described in this study have important implications for choosing pacing rates for patients receiving sensor driven, variable rate pacemakers.
Facilitation of the Subclavian‐Introducer Technique with Contrast Venography
Authors: HIGANO STUART T. , HAYES DAVID L. , SPITTELL PETER C.
Published: July 2006

The subclavian‐infroducer technique is a rapid and easily performed method of obtaining venous access for implanting permanent pacemaker electrodes. Although this technique has facilitated the participation of nonsurgeons in pacemaker implantation, the potential for complications is increased over the venous cutdown approach. This is particularly true in difficult cases, such as those with prior lead implants, venous thrombosis, or anomalous venous return. This article describes the use of contrast venography for facilitating an otherwise “blind” subclavian venipuncture. This method should make use of the subclavian‐introducer technique safer.
Thyrotoxicosis Induced Sick Sinus Syndrome: Medical Therapy May Avoid Permanent Pacing
Authors: LUBITZ ROBERT M. , ACKER JAMES J.
Published: July 2006

A 65‐year‐old white female developed sick sinus syndrome associated with thyrotoxicosis which resolved upon achieving a euthyroid state, thus obviating the need for permanent pacemaker implantation. TSH was < 0.1 ng/dL, and 24‐hour iodine uptake was 28%. After correction of the hyperthyroid state with propylthiouracil and potassium iodine, senatorial pauses up to 6 seconds resolved over 10 days. A subsequent sinus node recovery time was normal and no symptoms recurred over 22 months.
Occurrence of Atrial Fibrillation in Patients With Paroxysmal Supraventricular Tachycardia Due to Atrioventricular Nodal Reentry
Authors: HURWITZ JODIE L. , GERMAN LAWRENCE D. , PACKER DOUGLAS L. , WHARTON I. MARCUS , MCCARTHY ELIZABETH A. , WILKINSON WILLIAM E. , PRYSTOWSKY ERIC N. , PRITCHETT EDWARD L.C.
Published: July 2006

The occurrence of atrial fibrillation in patients with paroxysmal supraventricular tachycardia (PSVT) has been well documented when PSVT is secondary to atrioventricular reentry, but not when PSVT is secondary to atrioventricular nodal reentry (AVNRT). Seventeen patients with AVNRT were followed using transtelephonic electrocardiogram monitoring to document symptomatic tachycardias. The median length of telephone monitor surveillance was 357 days. Fifteen of 17 patients transmitted electrocardiograms that showed PSVT. Three of 17 patients (18%) transmitted eJectrocardiograms that showed atrial fibrillation. A transition from PSVT into atrial fibrillation was not recorded, but all three did have PSVT recorded on other days of follow‐up. We report the occurrence of atrial fibrillation in patients with AVNRT and that its incidence is higher than expected for the general population.
Thermal Catheter Disruption During Closed‐Chest Radiofrequency Ablation of the Atrioventricular Conduction System
Authors: FROHNER KLAUS J. , PODCZECK ANDREA , HIEF CHRISTINE , NURNBERG MICHAEL , STEINBACH KONRAD K.
Published: July 2006

Radiofrequency ablation of the atrioventricular conduction system was attempted in a 63‐year‐old man with drug refractory atrial fibrillation. A total of 5 radiofrequency pulses (750 kHz, power setting: 25–50 W. pulse duration: 9–20 sec) were delivered in a unipolar fashion via the distal electrode of a 7 Fr bipolar electrode catheter without induction of permanent AV block. No direct measurements of current (I) and voltage (U) were made. During the fifth pulse catheter disruption occurred at the interface of the shaft and the proximal electrode. Inspection of the catheter shaft revealed carbonized insulation material indicating overheating of the catheter tip. Overheating was presumably due to an impedance rise with unrecognized clot formation on the distal electrode. This led to progressive melting of insulation material during repeated radiofrequency applications and short circuiting of current flow to the proximal ring electrode that resulted in catheter disruption. This case report is the first to describe a serious complication of radiofrequency ablation. The complication might have been prevented by measurements of U and I, reflecting changes in impedance or by measurements of catheter tip temperature (T). It is concluded that measurements of U, I, and/or T are necessary to control the coagulation process thereby reducing the risk of serious complications during transcatheter radiofrequency ablation.
Successful Transcatheter Ablation of Congenital Junctional Ectopic Tachycardia in a Ten‐Month‐Old Infant Using Radiofrequency Energy
Authors: VAN HARE GEORGE F. , VELVIS HARM , LANGBERG JONATHAN J.
Published: July 2006

Congenital functional tachycardia is a difficult‐to‐control rhythm in children which has a high mortality rate with current management. A 10‐month‐old child followed since birth with the diagnosis of congenital functional ectopic tachycardia is reported. He failed treatment with multiple antiarrhythmic agents, and underwent an electrophysiology study. The Junctional focus was successfully ablated using transcatheter radiofrequency energy. This technique may be safer than high voltage DC shock ablation, particularly in small children.
Function of Ventricular Pacemakers During Resuscitation
Authors: ZULLO MICHAEL A.
Published: July 2006

The reciprocal effects of resuscitation and permanent, ventricular‐inhibited pacemakers were examined in four, well‐documented cases of witnessed out‐of‐hospital arrest. The resulting observations provide useful insight in the treatment of cardiac arrest in the large number of patients with permanent pacemakers. Transient sensing malfunctions occurred in the two patients in whom direct current countershocks were not required and were probabaly related to the severely deranged state of the myocardium. In spite of periods of asynchronous pacing in this critically unstable setting, no arrhythmias were precipitated. In the two patients who required defibrillation, transient malfunctions of pacing, capture and sensing occurred in spite of protective electronics in the pacing system, the left‐sided location of the generator and, in one patient, the bipolar configuration. The pacemaker appeared to intermittently sense coarse ventricular fibrillatory waves. The malfunctions in the two latter cases were probably the result of the combined effects of the countershock and the abnormal state of the myocardium. All four patients succumbed, three in the emergency room and one on the eighth hospital day. Outcome was predominantly determined by the patient's response to therapeutic interventions. The observed pacemaker malfunctions, although potentially life‐threatening, had no obvious, adverse effect on outcome in these four cases, mainly because of the transient nature of the abnormalities. Indeed, in one case, the presence of pacemaker activity was pivotal in identifying the native rhythm, illustrating the diagnostic potential of this analytical approach.
Closed Chest Radiofrequency Ablation of the Sinoatrial Node in Dogs
Authors: SANCHIS JUAN , CHORRO FRANCISCO J. , LOPEZ‐MERINO VICENTE , SUCH LUIS , CERDA MIGUEL , VALENTIN VICENTE
Published: July 2006

Transcatheter ablation of the sinoatrial node with radiofrequency energy (0.6 MHZ, 2.5–5 watts) was performed in 10 dogs under fluoroscopic monitoring and autonomic blockade. Sinus function was previously studied in terms of cycle length, recovery time and atrial activation pattern by catheter mapping. Several discharges (8–22) were applied for variable periods of time (maximum 1 minute). Sinus tachycardia and/or sinus arrest during ablation confirmed correct catheter position. Sinus rhythm was abolished in eight dogs. The ectopic rhythm was atrial in six and AV nodal in two dogs. Ectopic atrial cycle length and recovery time were longer than the baseline sinus values: 724 ± 321 versus 509 ± 147, P < 0.05; 1103 ± 775 versus 638 ± 151, P < 0.05 (values in msec). The study was repeated 10–14 days later in six dogs; three maintained the same atrial rhythm, one persisted in sinus rhythm, and one dog changed from atrial to sinus rhythm, whereas another changed from sinus to atrial rhythm. Gross findings revealed transmural lesions in all dogs, without perforation. Histology in chronic dogs showed sinus cell necrosis and its replacement by granulation tissue. In conclusion: sinus function may be abolished by closed chest radiofrequency ablation.
Single‐Lead VDD Pacing System
Authors: VARRIALE PHILIP , PILLA ANGELO G. , TEKRIWAL MAHESH
Published: July 2006

A single pass ventricular lead with a dual chamber electrode system, designed for VDD pacing, was implanted in 17 patients (11 men, 6 women, aged 53 to 86 years, mean 74) for symptomatic bradycardia due to second‐or third‐degree AV block and normal sinus node function. Bipolar atrial electrodes, diagonally displaced along the lead axis and positioned within the right atrial cavity, are used to detect atrial activity that is then differentially processed within the pacemaker, P wave amplitude (amp) derived from a PSA‐DAA device at implant was 1.38 ± 0.28 mV. P wave signal amp derived from telemetered atrial electrograms was 1,29 ± 0.22 mV at predischarge (n = 17), 1.32 ± 0.24 mV at 3 months (n = 15), 1.30 ± 0.24 mVat 6 months (n =8), 1.51 ± 0.34 mVat 9 months (n = 4), and 1.35 ± 0.35 mV at 12 months (n = 2); and the far‐field QRS signal measured at predischarge was of negligible voltage (0.17 ± 0.07 mV). The susceptibility of the atrial sensor system to interference was noted with chest wall stimulation and only at higher sensitivities (0.1 to 0.3 mV) and not with isometric arm exercise. Intact VDD pacing function at rest and during exercise was established using Holter and periodic ECG monitoring. Postoperative complications included one lead displacement and one pocket hematoma. Three patients died postimplant of causes unrelated to pacemaker function. Advantages of the single‐lead VDD pacing include: (1) elimination of second atrial sensing lead; (2) superior atrial sensing performance; (3) effective resistance to myopotential and far‐field signal interference; and (4) stability of postimplant atrial signal amplitude.
The Use of an Electrically Activated Valve to Control Preload and Provide Maximal Muscle Blood Flow with a Skeletal‐Muscle Ventricle
Authors: GEDDES L.A. , WESSALE J.L. , BADYLAK S.F. , JANAS W. , ACKER W.A. T , VOORHEES W.D.
Published: July 2006

A new method for optimally loading a skeletal muscle‐wrapped pouch to act as a Wood pump is described. The method takes advantage of the fact that the high preload pressure required for a forceful contraction needs to be present for only a short time. By using an electrically controlled valve to delay pouch filing until just be/ore muscle contraction, pouch diastolic pressure can be kept low, which in turn maintains a high muscle capillary blood flow. The intrapouch precontraction pressure can be controlled by selecting the appropriate valve‐open time (VOT). The pumping capabilities of untrained rectus abdominis and latissimus dorsi muscles were evaluated using a hydraulic circulatory system in a ten dog study (weight range 20–32.7 kg). The afterload was constant at 100 mmHg, and the pouch precontraction pressure, selected by choice of the VOT, was the test variable. It was found that for maximum pouch output, a precontraction pressure of 60–100 mmHg was required, being attained in this hydraulic model with a VOT of 400–500 msec. Typical pouch outputs were 400–600 mL/min with a muscle contraction rate of/40/min. Muscle capillary blood flow, measured with a periarterial electromagnetic flowmeter, varied inversely with pouch diastolic pressure and was near zero during tetanic muscle contraction. In one animal, a pouch output of 200 mL/min or more was maintained for more than 20 hours of continuous pumping without fatigue. In a related experiment, the method was applied to pump blood in a 32.7 kg dog, in which the muscle‐wrapped pouch was connected between the descending thoracic aorta and the abdominal aorta. A pouch output of about 400 mL/min was obtained when the muscle was contracted 30 times/min and the VOT was 400 msec. This flow represented about 20% of the animal's cardiac output. This study demonstrates that by delaying pouch filling until just be/ore the muscle is to be contracted, a low pouch diastolic pressure can be maintained, thereby maximizing muscle capillary blood flow and, in turn, providing the best opportunity for prolonged pumping.
Sustained Effectiveness of an Atrial Antitachycardia Pacemaker during Follow‐Up
Authors: SHANDLING ADRIAN H. , LI CURTIS K. , THOMAS LAVERGNE
Published: July 2006

Atrial antitachycardia pacemakers are indicated for medically refractory atrial rachyarrhyth‐mias. To confirm long‐term device effectiveness, we studied diagnostic data obtained in 17 patients with atrially‐placed Intermedic “Iniertach” pacemakers. The unit has programmable primary (P mod) and secondary (S mod) antitachycardia response protocols. Success of the P mod was defined as a P mod response first with no subsequent S mod response. Follow‐up was for 595 days (±302 days). The P mod was utilized first 88.2 ± 102 times per patient interrogation with subsequent S mod use 21.1 ± 53 times (P < 0.0001). Results were also significant when P mod was compared to S mod in the first versus the last half of follow‐up (both P < 0.0001). These results suggest that the programmed P mod of the atrial “Intertach” tachycardia reversion pacemaker has sustained effectiveness in the treatment of medically refractory atrial tachyarrhythmias.
Termination of Ventricular Tachycardia by Nonpropagated Local Depolarization: Further Observations on Entrainment of Ventricular Tachycardia from an Area of Slow Conduction
Authors: RUFFY RODOLPHE
Published: July 2006

A 60‐year‐old woman with a large left ventricular apical aneurysm underwent preoperafive catheter mapping of ventricular tachycardia. A zone of slow conduction with marked decremenlal conductive properties was identified between the left ventricular aneurysmal pouch and the right ventricular septum. Pacing from the right ventricuJar septum produced a QRS on the surface electrocardiogram of the same morphology as that of spontaneous ventricular tachycardia, while pacing from the left ventricular aneurysm caused tachycardia entrainment without fusion. Termination of ventricular tachycardia invariably occurred in association with an unpropagated left ventricular capture, followed by a change in ventricular activation to an opposite direction. This case provides a direct demonstration of reentrant ventricular tachycardia termination by orthodromic block in a zone of slow conduction.
Atrial and Ventricular Stimulation Threshold Development: A Comparative Study in Patients with a DDD Pacemaker and Two Identical Carbon‐Tip Leads
Authors: BRANDT JOHAN , ATTEWELL ROBYN , FÅHRAEUS THOMAS , SCHÜLLER HANS
Published: July 2006

The atrial and ventricular pacing threshold development during the first postoperative year was studied in a group of patients receiving DDD pacemakers, fdentical carbon‐tip endocardial leads were implanted in atrium and ventricle. Atrial and ventricular voltage stimulation thresholds were measured at implantation, and noninvasively at 1 and 12 months thereafter. The atrial amplifier sensitivity required for adequate P wave sensing during follow‐up was also determined. The possible influence of a number of factors upon atrial and ventricular threshold evolution was statistically assessed. The threshold data were complete in 57 patients (mean age ± SD, 65,2 ± 12.4 years). Thirteen patients had a diagnosis of sinus node disease, whereas 44 had not. Patient age and diagnosis did not significantly influence atrial or ventricular stimulation threshold development. Atrial sensing thresholds were not related to atrial stimulation thresholds during follow‐up. Atrial pacing thresholds were higher than ventricular thresholds at pacemaker implantation (P < 0.00005), but the postoperative threshold rise and thresholds at 1 and 12 months postoperatively did not differ significantly between the atrium and ventricle. The ratio of chronic to acute stimulation thresholds was higher on the ventricular than on the atrial level (0.003 > P > 0.0005). The chronic atrial threshold showed a logarithmic relation to the threshold at implantation (P = 0.0006); postoperative threshold rise was not a significant determinant of the chronic afrial threshold (P = NS). On the ventricular level, the reverse was seen: The chronic threshold was related to the postoperative threshold rise (P = 0.0015, logarithmic relation), but not to the implantation threshold (P = NS). The positive findings of this study appear compatible with the “virtual electrode concept” of postoperative stimulation threshold development.
Clinical Experience with a New Software‐Based Antitachycardia Pacemaker for Recurrent Supraventricular and Ventricular Tachycardias
Authors: FROMER MARTIN , GLOOR HANS , KUS TERESA , SHENASA MOHAMMAD
Published: July 2006

The Intermedics Intertach 262–12 tachycardia reversion pulse generator was implanted in 14 patients (six male, eight female, mean age at implantation 45 ± 16 years) with recurrent symptomatic tachycardias. Six patients had atrioventricular (AV) nodal reentrant tachycardia, three patients had orthodromic tachycardia with Wolff‐Parkinson‐White syndrome, two had circus movement tachycardia via a concealed bypass tract, two had ventricular tachycardia, one patient had atrial flutter. Mean duration of symptoms before implantation was 8 ± 4 years and mean number of antiarrhythmic drug trials was 3.5 ± 1. The primary tachycardia response mode consisted of autodecremental pacing in one patient, burst pacing in two patients, and adaptive scanning of the initial delay or burst cycle length in eleven patients. The secondary tachycardia response mode consisted of autodecremental pacing in four patients, burst pacing in three patients and burst scanning in four patients. Tachycardia response was automatic in all but one patient with ventricular tachycardia. During a follow‐up period of 30.5 ± 10.6 months, one patient with ventricular tachycardia died from a nonarrhythmic cause, Reinterventions were necessary due to electrode fracture in one patient and due to pacemaker software defect in another one. Two patients underwent surgical cure of their arrhythmia: one patient with atrial flutter and one patient with AV nodal reentry tachycardia, 24 months and 11 months postpacemaker implantation, respectively. Four patients required digitalis to prevent pacing induced atrial fibrillation. Other proarrhythmic effects were not encountered. The pacemaker proved to be a versatile system with reliable tachycardia detection and termination functions. It provided a valuable adjunctive therapy in these selected patients.
Reentrant Fascicular Tachycardia with Cycle Length Alternans: Insights into the Tachycardia Mechanism and Origin
Authors: TAI YAU‐TING , FONG PING‐CHING , LAU CHU‐PAK , CHOW WING‐HING , CHENG CHUN‐HO
Published: July 2006

This report details the electrophysiology of a unique case of reentrant fascicular tachycardia in a patient without structural heart disease. Persistent cycle length alternans, with constant fluctuation in alternate RR intervals, occurred during tachycardia. A distinct mode of spontaneous termination of tachycardia was observed. The findings were consistent with the presence of decrementel conduction properties in the tachycardia circuit or decrementel dual functional pathways within one limb of the circuit. These observations provide further evidence in support of a fascicular origin of the tachycardia.
Cryoablation of Medically Refractory Nodoventricular Tachycardia
Authors: SILKA MICHAEL J. , KRON JACK , CUTLER JOEL E. , WILSON RICHARD A. , COBANOGLU ADNAN
Published: July 2006

Paroxysmal wide QRS tachycardia, based on a nodoventricular accessory connection, is an uncommon arrhythmia. In this report, the endocardial and epicardial mapping and Cryoablation of a nodoventricular fiber, documented to participate in medically refractory tachycardia in an 11‐year‐old boy, are described. Epicardial cryothermia, applied at the earliest site of right ventricular activation, resulted in the abrupt termination of tachycardia. Endocardial cryothermia was subsequently applied in the perinodal region, the presumed site of origin of the nodoventricular fiber. No tachyarrhythmias were inducible postoperatively, and no antiarrhythmic treatment has been required during 18 months of follow‐up. Based on precise anatomic localization of the nodoventricular connection, a definitive cure of associated tachyarrhythmias may be possible utilizing cryothermia, without the requirement for extensive intraoperative dissection.
Magnesium Therapy in Ventricular Arrhythmias
Authors: KEREN ANDRE , TZIVONI DAN
Published: July 2006

Magnesium (Mg) is the known activator of 300 enzymes which govern energy utilization, cell permeability, and ionic membrane currents in the cardiac conducting cells. This may explain the antiarrhythmic efficacy of Mg in specific clinical settings, despite its only modest electrophysiological effects. This review summarizes the effect of Mg administration in four clinical conditions: in digitalis toxicity; in drug‐induced torsade de pointes; in patients with chronic diuretic therapy; and in acute myocardial infarction. Mg effectively abolished ventricular tachyarrhythmias associated with digitalis intoxication. This effect of Mg is related to the activation of sodium‐potassium ATP‐ase, which is inhibited by digitalis. Drug‐induced torsade de pointes was promptly abolished by Mg sulfate in the clinical setting. Experimental studies showed that Mg suppresses the early after depolarizations and the triggered activity responsible for occurrence of the arrhythmia. In diuretic‐treated hypertensives, potassium depletion has been associated with increased ventricular ectopy and sudden death. Mg has been found to be an important adjuvant for intracellular repletion of potassium in these patients. Several randomized, double‐blind studies in patients with acute infarction showed that Mg administered on admission improved survival or reduced the incidence of complex ventricular arrhythmias. Thus, Mg should be employed as first‐line therapy in digitalis intoxication and drug‐related torsade de pointes, and should be considered an important adjuvant therapy in hypertensives treated with diuretics and patients with acute myocardial infarction.
A Technique for the Prevention of Automatic Implantable Cardioverter Defibrillator Generator Migration
Authors: MANCINI MARY C. , GRUBB BLAIR P.
Published: July 2006

In order to prevent AICD generator migration in nine patients and correct chronic painful generator migration in three patients, we placed the AICD generator in an absorbable microfibrillar collagen pouch at the time of implant to facilitate fibrous capsule formation. Over a mean follow‐up period of 14 ± 2 months for the new implants, there have been no episodes of generator erosion, migration or infection. The three patients who suffered from generator migration have been symptom free for 22 ± 2 months. We conclude that use of a microfibrillar collagen pouch at the time of AICD implant is a safe, inexpensive, and effective method for preventing generator migration.
A Technique for Intraoperative Arrhythmia Induction during Automatic Implantable Defibrillator Placement
Authors: GRUBB BLAIR P. , MANCINI MARY
Published: July 2006

In 14 patients (12 men, 2 women, mean age 51 ± 4 years) we evaluated a new technique for Intraoperative arrhythmia induction during Ventak 1550 automatic implantable cardioverter defibrillalor (AICD), pulse generator placement. At the lime of surgery (nine new impants, five pulse generator replacements), when the AICD pulse generator is in its final configuration with the rate sensing and patch electrodes leads inserted into the header, a #2 hex wrench was inserted into each of the rate sensing lead set screw sites. The alligator clips of a temporary pacing cable were placed on each of the hex wrenches and the remainder of the cable passed off field for attachment to a programmed stimulator or AC fibrillator. In all 14 patients, the clinical arrhythmia was induced at least twice (ventricular tachycardia in eight patients, ventricular fibrillation in six patients). No difficulties with arrhythmia induction or AICD sensing as discharge were encountered. We conclude that this technique is both a safe and effective means of intraoperative arrhythmia induction during placement or replacement in the Ventak AICD 1550 and 1600 series pulse generators.
Wolff‐Parkinson‐White Syndrome Associated with a Coronary Sinus Diverticulum: Ablative Surgical Approach
Authors: MCGIFFIN DAVID C. , MASTERSON MARTIN L. , STAFFORD WAYNE J.
Published: July 2006

This report concerns a patient with drug refractory supraventricular tachycardia due to the Wolff‐Parkinson‐White syndrome in association with a coronary sinus diverticulum. Division of the anomalous bypass tract was initially performed by an endocardial approach together with circumferential dissection of the neck of the diverticulum. This procedure failed to ablate the bypass tract that was only successfully divided when the superficial wall of the diverticulum was excised. This case illustrates the dose association that exists between an anomalous atrioventricular bypass tract and a coronary sinus diverticulum, and the importance of dividing the superficial wall of the diverticulum as an integral part of the ablative procedure.
Atrial Natriuretic Peptide Levels Reflect Hemodynamic Changes Under Pacemaker Stimulation
Authors: NOLL BERND , KRAPPE JOACHIM , GÖKE BURKHARD , MAISCH BERNHARD
Published: July 2006

Pacemaker stimulation influences plasma levels of atrial natriuretic peptide (ANP). This study evaluated in individuals without impaired myocardial function whether a consecutive increase of pacing rates results in reduced alteration of plasma ANP levels mirroring a putative decrease of atrial contribution to cardiac output. In nine resting patients with DDD pacemakers, absolute and relative ANP plasma levels were determined under DDD (175 msec AV delay) and VVI pacing at a pacing rate of 72, 82, 92, and 113 beats/min. When pacing rates were consecutively increased, higher plasma ANP concentrations were measured. However, the differences in relative ANP levels between DDD and VVI pacing decreased. At 113 beats/min, both relative and absolute ANP levels were nearly identical. Therefore, it seems likely that the atrial contribution to cardiac output at high pacing rates is less important than at lower frequencies, at least when the overall myocardial function is not impaired.
Ventricular Cross Stimulation Using a Pacing System Analyzer
Authors: GOLDSCHLAGER NORA , FRANCOZ RICHARD
Published: July 2006

Cross simulation refers to the situation in which a pacing lead positioned in one cardiac chamber results in stimulation of another chamber. We report three cases of ventricular cross stimulation observed at the time of pacing system implantation. The cross stimulation occurred through bipolar atrial and ventricular leads connected in bipolar configuration to a dual chamber pacing systems analyzer. Analysis of events during cross stimulation indicated that the current pathway was occurring within the pacing system analyzer itself, due to low resistance internal connections between the ring electrodes of the atrial and ventricular pacing systems analyzer channels. Cross stimulation within the pacing system analyzer can be eliminated by making the ventricular channel unipolar. Awareness of the phenomenon reported here should assist in the avoidance of the mistaken diagnosis of pacing lead migration and malposition during pacing system implant procedures.
Ventricular Cross Stimulation in a Dual Chamber Pacing System: Phenomenon Analysis
Authors: PUGLISI ANDREA , RICCI RENATO , AZZOLINI PAOLO , NEJA CARLO PERALDO , FIORANELLI MASSIMO , SPECIALE GIULIO , ANGRISANI GERARDO
Published: July 2006

Seven cases of ventricular cross stimulation from a group of 23 patients implanted with DDD devices are presented. In two patients the phenomenon was observed at the moment of DDD programming at nominal values, and in five other patients it was reproduced by increasing the atrial output voltage up to ten volts. In all 23 patients cross stimulation disappeared permanently within 24 hours after implantation. From the onset of cross stimulation to its end, atrial and ventricular threshold voltages were unchanged, while the atrial and ventricular impedances significantly decreased. These results suggest that an important role in the phenomenon occurs by impedance variation at the interface between the pulse generator and body tissue.
Rate‐Dependent Threshold Changes During Atrial Pacing: Clinical and Experimental Studies
Authors: KATSUMOTO KEIICHIRO , NIIBORI TATSURU , WATANABE YOSHIO
Published: July 2006

In 36 patients undergoing a permanent right atrial pacing for the treatment of sick sinus syndrome and/or atrioventricular block, the stimulation threshold was determined at a wide range of pacing rates (60 to 120 beats/min) 7 to 10 days after the lead implantation. Twenty‐nine (80%) of these cases showed rate‐dependent threshold changes, with significantly lower thresholds at higher than lower pacing rates (e.g., 2.91 ± 1.01 mA at 70 beats/min and 2.32 ± 0.75 mA at 120 beats/min, P < 0.01). Thus, with a fixed, smaller current strength, the stimuli often /ailed to capture the right atrium at lower rates, but caused a 1:1 capture at higher rates. In an echocardiographic study in another series of eight patients, the end‐diastolic diameter of the left atrium was decreased from 3.2 ± 0.9 to 2.7 ± 0.8 cm (P < 0.01) when the pacing rate was increased from 60–70 beats/min to 100–120 beats/min. in experiments using two anesthetized, open‐chest dogs, a rapid withdrawal of 500 mL of arterial blood reduced the right atrial dimension. This was accompanied by an increased amplitude of the right atrial endocardial electrogram, and the initially subthreshold stimuli became effective in capturing the atria. It was concluded that (1) rate‐dependent threshold changes were commonly observed in the early stage of atrial pacing, and (2) fluctuations in the electrode contact with the endocardium appeared responsible for such threshold changes.
Is Accurate Rate Response Programming Necessary?
Authors: SULKE NEIL , DRITSAS ATHANASE , CHAMBERS JOHN , SOWTON EDGAR
Published: July 2006

Exercise capacity and general well‐being are improved by appropriately programmed rate responsive pacemakers when compared to fixed rate units. Ten patients had activity sensing DDDR units implanted for combined AV block and sinus node incompetence. Ten patients had Sensolog activity sensing VVIR units implanted for complete heart block. The effects of over and under programming of rate response in both dual and single chamber activity sensor rate adaptive pacemakers has been assessed subjectively by visual analog scales and specific activity questionnaires and objectively by graded treadmill testing and the performance of standardized daily activities. Patients were randomly programmed to absent rate response VVI in the Sensolog group), hyporesponsive (DDD in the dual chamber group), appropriate response (VVIR, DDDR according to Manufacturer's instructions) and over responsive (VVIR+, DDDR+) in a double‐blind crossover design. Thirty percent of patients demanded early crossover from VVI, 30% from DDDR+ and 50% from VVIR+. Perception of Exercise Capability was similar to objective exercise treadmill times which were shorter in VVI than in VVIR or VVIR+ (P < 0.05) or control subjects (P < 0.001). There was no difference between any dual chamber mode or control subjects. General well‐being was poorest in DDDR+ and VVIR+ modes despite objective improvement in exercise capacity. Symptoms were least in VVIR and DDDR and all but one patient chose appropriate programming as their overall preferred mode. Thus, even inaccurate rate response programming results in similar and improved exercise capacity compared to absent rate response but overprogramming is unacceptable to most patients, confirming that appropriate programming and sensor specificity is critical in rate responsive pacing.
Phrenic Nerve Stimulation for Central Ventilatory Failure with Bipolar and Four‐Pole Electrode Systems
Authors: BAER GERHARD A. , TALONEN PASI P. , SHNEERSON JOHN M. , MARKKULA HANNU , EXNER GERHARD , WELLS FRANCIS C.
Published: July 2006

A multi‐channel phrenic nerve stimulator developed in Tampere has been implanted into seven patients with C2‐etraplegia and into three patients with central sleep apneas. Six bipolar cuff electrodes were implanted bilaterally into the neck. Two four‐pole cuff and 14 four‐pole noncuff electrodes were used in seven patients and to replace one bipolar electrode. Four‐pole electrodes were implanted within the thorax. Seven patients achieved total independence from conventional ventilators within 4 months of implantation, and one for 18 hours each day. Two patients died 12 days and 3 months after implantation and two patients after having achieved independence from mechanical ventilators from causes unrelated to the simulators. Reoperations were necessary because of dislocation of receivers, electrodes, electrode lesions, nerve injuries, and technical failures in seven patients. Most of the problems appeared in two patients with obesity and in three patients with very thin phrenic nerves. Single unit prototypes failed technically more frequently than units of prototype serial fabrication. New electrode design, progress in the manufacture of receivers, and improved implantation technique should help to diminish failures in future.
Internal Cardioverter Defibrillator: Component Failure
Authors: VLAY STEPHEN C. , OLSON LINDA C. , BURGER LYNN
Published: July 2006

Sudden death occurred in a patient with congestive cardiomyopathy, sustained ventricular tachycardia refractory to amiodarone, and an automatic internal Cardioverter defibrillator. Interrogation of the AICD at the time of death was indicative of malfunction. Postmortem analysis documented component failure involving a voltage regulating transistor resulting in prolonged charge times.
The Clinical Use of External Noninvasive Pacing in the Termination of Sustained Ventricular Tachycardia
Authors: GRUBB BLAIR P. , TEMESY‐ARMOS PETER , HAHN HARRY , ELLIOTT LAURA
Published: July 2006

In order to evaluate the potential use of external cardiac pacing (EXP) in the clinical termination of sustained ventricular tachycardia (VT), we attempted VT terminations in seven patients. All had recurrent sustained monomorphic ventricular tachycardia (mean rate 145 beats/min), which had previously required cardioversion. During subsequent VT episodes, all seven underwent overdrive pacing with EXP at a pulse amplitude of 120 mA, and rates of 200 pulses/min. A total of 18 of 18 episodes of VT were successfully terminated by EXP alone. In one patient, the first attempt at EXP termination of one episode of VT resulted in an acceleration of the tachycardia, which was then terminated by EXP. All patients tolerated EXP well with minimal sedation. We conclude that EXP may be an effective clinical modality for the termination of sustained monomorphic ventricular tachycardia.
Simultaneous, Multiple Point Mapping During Surgery for Wolff‐Parkinson‐White Syndrome Without the Use of a Computer
Authors: BRODINE WILLIAM N. , BAKER KATHLEEN A. , KIRCHMER J. THOMAS , CHIARELLI THOMAS E.
Published: July 2006

Epicardial mapping of patients undergoing surgical correction of the Wolff‐Parkinson‐White syndrome is usually accomplished by using a single point probe. This somewhat tedious and time consuming method has been streamlined by computer‐based systems allowing multiple simultaneous point maps to be developed either by electrodes applied as a band around the atrioventricular groove or a sock over the ventricle. Because the computer technology required to access, analyze, and display this data is not widely available, a system was devised to display ten simultaneous electrograms from a wrap of ten electrodes placed about the atrial or ventricular side of the atrioventricular groove. Using this technique three patients undergoing surgery for accessory pathway removal were accurately and quickly mapped allowing surgical cure of the preexcitation in each case.
Correlation Between the Ventricular Electrogram Amplitude in Sinus Rhythm and in Ventricular Fibrillation
Authors: LEITCH JAMES W. , YEE RAYMOND , KLEIN GEORGE J. , JONES DOUGLAS L. , MURDOCK CHALLON J.
Published: July 2006

During testing of implantable defibrillators, ability to sense ventricular fibrillation is assessed by observing electrograms and the emitted ECG interpretation channel during induced ventricular fibrillation. We hypothesized that ventricular electrogram amplitude in sinus rhythm could be used to predict the ventricular electrogram amplitude in ventricular fibrillation and serve as a first approximation of the “safety margin” for sensing ventricular fibrillation. We compared the peak‐to‐peak epicardial ventricular electrogram during sinus rhythm and ventricular fibrillation in 12 patients undergoing defibrillator impJantation. The ventricular electrogram was recorded with an integrated bipolar lead and Altered at 10–50 Hz. Ventricular fibrillation was induced by alternating current and the ventricular electrogram measured from cessation of alternating current to the first countershock. The mean ventricular electrogram amplitude in sinus rhythm was 15.3 ± 5.4 mV (range 7.1–25.5) and in 37 episodes of ventricular fibrillation was 8.3 ± 3.6 mV frange 2.1–16.3). There was a significant relationship between the mean ventricular electrogram amplitude in sinus rhythm and in ventricular fibrillation (R = 0.7, P < 0.001). There was wide variation among individuals in the decrease in the mean ventricular electrogram amplitude during ventricular fibrillation, with the ratio of mean ventricular electrogram in sinus rhythm to mean ventricular electrogram in ventricular fibrillation ranging from 0.29 to 1.05 (mean 0.55 ± 0.20). This suggests that up to a fourfold decrease may be expected in the mean ventricular electrogram amplitude during ventricular fibrillation. These results suggest that there is a relationship between the mean ventricular electrogram in sinus rhythm and in ventricular fibrillation which is useful as an initial approximation in assessing sensing lead function and programming device sensitivity levels.
The Influence of Endocardial Electrode Fixation Status on Acute and Chronic Atrial Stimulation Threshold and Atrial Endocardial Electrogram Amplitude
Authors: SHANDLING ADRIAN H. , CASTELLANET MARK J. , THOMAS LAVERGNE A. , MESSENGER JOHN C. , RYLAARSDAM ARLENE , EVANS KARLA , CASTELLANET CRAIG
Published: July 2006

The endocardial atrial electrogram or “P wave amplitude” (PWA) and pacemaker atrial stimulation thresholds are important parameters determining correct pacing system junction. Pacemaker lead fixation mechanism and lead age may negatively influence these parameters. Therefore, we compared acute and chronic PWA and atrial stimulation thresholds in 33 patients with permanent transvenous atrial screw‐in leads, follow‐up 647 days ± 297 days; and in 31 patients with nonscrew leads, follow‐up 855 days ± 512 days (P = ns). Results: The PWA differed between the two lead types acutely (1.97 mV ± 0.8 mV for screw‐in versus 2.48 mV ± 1.1 mV for nonscrew‐in leads; P < 0.05), but not chronically (2.21 mV ± 0.8 mV vs2.2 mV ± 1.2 mV; P = ns). Acute and chronic atrial pacing thresholds did not differ between groups. We also analyzed an early interim PWA in a subgroup of patients (mean 31 days after implantation). The nonscrew fixation group interim PWA was 1.76 mV ± 0.9 mV versus 2.7 mV ± 1.2 mV at implant (P < 0.001). The screw‐in lead interim PWA was 2.04 mV ± 0.9 mV versus 1,97 mV ± 0.7 mV at implant (P = ns). Conclusions: (1) A significantly higher endocardial PWA occurs at the time of lead implantation in nonscrew versus screw‐in lead groups, but the chronic PWA does not differ between the two groups. (2) A transient but marked early (mean approximately 31 days) attenuation of the PWA occurs only with nonscrew‐in leads, (3) Atrial threshold stimulation energies do not differ between the two lead groups acutely or during follow‐up.
Inappropriate Discharges by the Implantable Cardioverter Defibrillator During Postoperative Testing: Implications for Intraoperative Assessment
Authors: SULKE NEIL , HOLT PHYLLIS , BOSTOCK JULIAN , YATES ALAN , SOWTON EDGAR
Published: July 2006

Inappropriate shocks were delivered to a patient while in sinus rhythm by an implantable Cardioverter defibrillator (ICD) during routine prehospitai discharge testing. This was induced by the standard programmer when the “read” telemetry sequence was initiated. The ICD was removed and found to suffer from electrical artifact that was sensed as ventricular tachycardia during telemetry. To avoid inadvertent telemetry‐induced shocks during routine testing, all ICDs should be interrogated, using a standard programmer, intraoperatively, with the unit in “defibrillation on” mode.