bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrophysiological Effect of the Maze Procedure on Canine Sinoatrial Node Function
Authors: MCLOUGHLIN DAVID E. , BLITZ ARIE , SIMMONS JESSICA , BRODMAN RICHARD , FRAME ROSEMARY , BATOR STEVE , ADAMS JOHN , SCHWARTZ DANIEL S. , FURMAN SEYMOUR , FISHER JOHN D.
Published: July 2006

The maze procedure is an operation that has had great initial success in curing atrial fibrillation. This procedure includes several right atrial incisions that may interrupt the integrity of the sinoatrial node or its arterial supply. To assess the effect of the maze procedure on sinus node function (SNF), the following studies were performed: sinus node recovery times (SNRT), corrected SNRT (CSNRT), CSNRT under autonomic blockade maximal heart rate and intrinsic heart rates. Thirty‐four dogs underwent a right thoracotomy with cardiopulmonary bypass (CPB). The dogs were divided into three groups. Group I (n = 9), the sham group, underwent CPB without any incisions. Group 2 (n = 8) underwent CPB and one of the right atria] incisions. Group 3 (n = 18) underwent CPB and all three of the right atrial incisions. SNF was determined before and after the procedure. Groups 1 and 2 had no significant difference in measured SNF acutely after the procedure. In Group 3 the mean SNRT increased from 552 msec to 1,984 msec (P = 0.005). Sinus node dysfunction was corroborated by all studies. In the chronic studies, a trend toward recovery of SNF was observed. The maze procedure results in significant acute sinus node dysfunction. This dysfunction may resolve spontaneously over the ensuing months. Modifications of the maze procedure that avoid the sinus node or its blood supply area may reduce procedure related sinus node dysfunction.
Dual Chamber Rate Responsive Pacing to Allow Sotalol Therapy for Ventricular Tachycardia
Authors: HORRIGAN M.C. , DAVIS M.J.E. , MAY C. , SMITH P.
Published: July 2006

In order to allow the use of sotalol to control ventricular tachycardia (VT), dual chambe rate responsive (DDDR) pacemakers were implanted in ten patients aged 6 to 73 years (mean 50 years) Nine presented with monomorphic VT (seven inducible at baseline electrophysiological study (EPS)) ant one with syncope (monomorphic VT at EPS). On sotalol, VT was initiated in only one. This patien received sotalol in the absence of an effective alternative agent. The mean dose was 468 ± 269 mg/day Indications for pacing were symptomatic sotalol induced bradycardia (7), sinus node dysfunction (1) postoperative complete heart block (1), and infra‐His block at baseline EPS (1). At least five of these patients would have been candidates for an implantable cardioverter defibrillator had sotalol required discontinuation. Initially, nine patients were paced in DDDR mode and one, with normal AV conduciioi on sotalol, in AAIR. One patient was unable to tolerate sotalol despite pacing. One patient died suddenly after 35 months of symptom‐free follow‐up. There was a significant improvement in symptomatic statu, (P = 0.03) after pacing among the other eight patients with no recurrence of VT. The implantation of DDDR pacemaker may be indicated in selected patients with serious cardiac arrhythmias. With such < device programmed to an appropriate mode, sotalol can be used successfully where otherwise contraindi cated by bradycardia or preexisting conduction disease. For some patients this may obviate the expense inconvenience, and attendant risks of implantable cardioverter defibrillator implantation.
Comparison of Verapamil and Diltiazem in the Suppression of Idiopathic Ventricular Tachycardia
Authors: GILL JASWINDER S. , WARD DAVID E. , CAMM A. JOHN
Published: July 2006

This study examines the efficacy of verapamil and diltiazem in the suppression of idio‐pathic ventricular tachycardia (VT). Eight patients (mean age 29.8 ± 12.3 years, two males and six females) with VT, without any underlying cardiac abnormality on clinical examination and noninvasive investigation, were studied. The inducibility of the clinical VT was examined by treadmill exercise testing and programmed ventricular stimulation (PVS). In six patients, VT was inducible by exercise testing and in the remaining two by PVS. Following baseline testing, verapamil (120‐mg thrice daily) and diltiazem (60‐mg thrice daily) were administered in random order, allowing 5 half‐lives for the drug to load before evaluation. Two patients had complete suppression of the VT and the remaining six patients demonstrated a partial response to both calcium antagonists. In the patients with a partial response, the duration of the longest run of VT was reduced (baseline 96.0, 34.2 SEM); verapamil 19.2 (7.5); diltiazem 45.3 (21.4 beats), whereas, there was no change in the rate of VT (baseline 199.7 (8.0); verapamil 184.5 (11.4); diltiazem 201.0 (9.5 beats/min). No proarrhythmic effect was observed with either of the drugs in these patients. We conclude that idiopathic VT can be suppressed in some patients by calcium antagonists. In patients with a partial response, the length of run of the VT can be reduced, but the rate is unaffected. Verapamil and diltiazem do not differ in their ability to suppress VT in individual patients.
Antiarrhythmic Efficacy of Ethacizine Assessed by Programmed Electrical Stimulation in Patients with Ventricular Tachycardia
Authors: KAIK JÜKI , KAIK VEERA , KIITAM MAIRE
Published: July 2006

The efficacy of ethacizine, a Class Ic drug, was assessed by programmed electrical stimulation (PES), delivering single, double, and triple extrastimuli at paced drives of 100 and 140 beats/min from two right ventricular sites (apex and out flow tract) in 38 patients with recurrent sustained ventricular tachycardia (VT). Underlying disease was coronary artery disease (CAD) in 26 (group I) and other conditions in 12 patients (group II; hypertrophic cardiomyopathy in 7, mitral valve prolapse in 1, and no apparent heart disease in 4). In the baseline study VT was induced in all patients. After a single intravenous dose (0.6‐0.7 mg/kg) of ethacizine, VT was still inducible in six patients in group I and seven patients in group II. Ethacizine was administered on a long‐term basis to all patients in a dose of 200‐400 mg per day. All but one CAD patient remained free of recurrences after a mean follow‐up of 16.5 (range 3‐22) months, while there were recurrences in six of 12 patients in group II. We conclude that: (1) ethacizine appears to be effective in the treatment of VT in CAD patients; (2) the study demonstrates the clinical utility of PES in the management of VT, although some patients in whom VT remains inducible on ethacizine may have good clinical outcome; and (3) the efficacy of ethacizine in other forms of heart disease remains to be studied.
Relationship Between Spectral Measures of Heart Rate Variability and Ventricular Ectopic Activity in Patients with Idiopathic Ventricular Tachycardia
Authors: GILL JASWINDER S. , LU FEZ , WARD DAVID E. , CAMM A. JOHN
Published: July 2006

This study examines the relationship of hourly spectral measures of heart rate variability (HRV) to the occurrence of ventricular ectopic (VE) activity in 20 patients with idiopathic ventricular tachycardia and frequent VE's. Spectral measures of HRV were obtained from 24‐hour Holler recordings from the patients in a drug free state and included the total energies in the spectrum, the low frequency components (1) (0.04–0.15 Hz) representing predominantly sympathetic lone with some contribution from the parasympathetic and high frequency components (H) (0. 15–0.4 Hz) representing mainly parasympathetic tone. A high H component (parasympathetic) was defined as area > 12 msec and high L components (sympathetic) as area > 30 msec. On an hourly analysis of spectral components in relation to VE activity, VE's occurred significantly more frequently during periods of low H and low L (F = 20.5, DF = 3, P < 0.0001). The number of VE's did not differ statistically in the other combinations of H and L components flow H, low L = 612.8 (50.1); high H, low L = 180.1 (36.8); low H, high L = 338.4 (58.9); high H, high L ‐ 204.9 (17.7) VE's/hr (SEM). The results suggest that VE's are more frequent during periods of low H and low L and are diminished when either H or L are increased in patients with idiopathic ventricular tachycardia. The results would be consistent with the hypothesis that the parasympathetic nervous system has an electro physiologically stabilizing effect on the myocardium.
Bedside Termination of Sustained Ventricular Tachycardia by Transesophageal Atrial Pacing
Authors: KATZ AMOS , KNILANS TIMOTHY K. , PRYSTOWSKY ERIC N.
Published: July 2006

Transesophageal atrial pacing was used to terminate hemodynamically stable sustained mono‐morphic ventricular tachycardia in two patients. The procedure was performed at the bedside, no anesthesia was required, there were no complications, and one of the patients went home after the procedure was performed. This method should be considered prior to using direct current cardioversion in patients with hemodynamically stable sustained monomorphic ventricular tachycardia.
TU Alternans, Long QTU, and Torsade de Pointes: Clinical and Experimental Observations
Authors: HABBAB MOHAMMAD A. , EL‐SHERIF NABIL
Published: July 2006

T or U wave alternans in association with long QTU and torsade de pointes (TdP) is uncommon and its mechanism(s) is unknown. We studied three patients with TU alternans, long QTU, and TdP: patient 1 was a newborn with congenital long QTU; patient 2 had marked hypokalemia and hypomagnesemia; and patient 3 was receiving procainamide. In the three patients, TU alternans was tachycardia dependent and preceded the onset of TdP. In the patient on procainamide, TU alternans and TdP occurred at long cardiac cycles, In this patient, endocardial monophasic action potential (MAP) recordings showed that TU alternans was associated with alternation of the duration of the plateau. A deflection consistent with early after depolarization (EAD) arose at a constant time interval from phase 0 but alternated from high and low levels of phase 3. The first ectopic beat of TdP arose on the descending limb of the EAD. TU alternons was investigated by MAP recordings in six normal dogs, following the administration of anthopleurin‐A (AP‐A), a drug shown to delay sodium inactivation and to induce bradycardia dependent long QTU, EADs, and TdP. In two dogs TU alternans was associated with 2:1 recordings of EAD and nearly constant plateau duration. In three dogs, TU alternans was associated with EAD that occurred in consecutive beats at constant time intervals from phase 0, but alternated from high and low phase 3 because of alternation of the duration of the plateau. In one dog, alternation of EAD and plateau duration occurred. In 36 separate episodes of TdP that were analyzed in the six dogs, 32 were bradycardia dependent but four developed on abrupt shortening of the cardiac cycle associated with alternation of action potential duration. Our results suggest: (1) TU alternans may be due to 2:1 propagation of an EAD or to alternation of the recovery kinetics of a repolarization current; (2) The constant occurrence of EAD in relation to phase 0 in spite of alternation of plateau duration suggests an ionic mechanism synchronized to depolarization; (3) Tachycardia dependent TdP in clinical and experimental examples of long QTU seems to be characteristically associated with TU alternans. Dispersion of repolarization may underlie the increased ventricular electrical instability in these cases.
Syncope—Brain or Heart? A Case Report
Authors: NILSSON HÅKAN , FREITAG MICHAEL , HINDFELT BENGT , JOHANSSON BENGT W. , ROSÉN INGMAR
Published: July 2006

A 44‐year‐old man suffered from recurrent episodes of unconsciousness, without any other concomitant manifestations. After routine ivorkup, EEC and CT had proven nondiagnostic, prolonged Holter monitoring revealed a single episode of asystole, lasting 7.6 seconds. A pacemaker was inserted but did not abolish his episodic syncope. Subsequently, long‐lerm EEC recording revealed epileptiform activity with independent foci in both temporal Jobes. Antiepilepfic treatment relieved the patient of his symptoms. This case illustrates the intimate relationship between the heart and the brain that sometimes lies behind syncope.
Unusual Wenckebach Upper Rate Response of an Atrial‐Based DDD Pacemaker
Authors: FREDMAN CAREY S. , BJERREGAARD PREBEN , JANOSIK DENISE L. , BAROLD S. SERGE
Published: July 2006

We describe in this report an unusual form of Wenckebach upper rate response produced by a DDD pulse generator with atrial‐based lower rate timing. The pacemaker maintained the programmed upper and lower rate intervals at the expense of a prolonged atrial paced‐venfricular paced AV interval. This form of upper rate behavior eliminated the longer cycle (containing the unsensed P wave) that occurs at the end of the pacemaker Wenckebach sequence during traditional DDD pacing with ventricular‐based lower rate timing.
Thermal Ablation of Perfused Porcine Left Ventricle In Vitro with the Neodymium‐YAG Laser Hot Tip Catheter System
Authors: HAINES DAVID E.
Published: July 2006

Catheter ablation in the treatment of arrhythmias has been limited by the small lesion size achievable with a radiofrequency energy source. The feasibility of catheter ablation with a neodymium‐yttrium‐aluminurn‐garnet (Nd‐YAG) laser hot tip catheter was tested because of the capability of achieving a high catheter‐tissue contact temperature, which should result in a larger lesion. In a model of isolated perfused pig hearts, 77 endocardial lesions were produced with powers of I to 10 watts and peak measured temperatures of 40° to 318°C. Lesion size correlated with power and temperature, but the correlations were poor. High temperature lesions resulted in significant intramyocardial catheter penetration and only marginal increased lesion width. Catheter ablation with a Nd‐YAG laser hot tip catheter is feasible, but carries a risk of perforation at high powers. High temperatures result in tissue dessication with a resultant fall in thermal conductivity that limits the radius of thermal injury and overall lesion size.
Electrophysiological Abnormalities of the Atrial Muscle in Patients with Manifest Wolff‐Parkinson‐White Syndrome Associated with Paroxysmal Atrial Fibrillation
Authors: KONOE ATSUSHI , FUKATANI MASAHIKO , TANIGAWA MUNEO , ISOMOTO SHOHRO , KADENA MITSUO , SAKAMOTO TOSHIFUMI , MORI MITSUHIRO , SHIMIZU AKIHIKO , HASHIBA KUNITAKE
Published: July 2006

We investigated the electrophysiological properties of the atrial muscle in 33 patients with manifest Wolff‐Parkinson‐White syndrome. Group I consisted of 13 patients with paroxysmal atrial fibrillation and group II consisted of 20 patients without paroxysmal atrial fibrillation. The anterograde and retrograde effective refractory periods of the accessory pathway and the inducibility of atrioventricular reciprocating tachycardia were not significantly different between the two groups, Endocardial electrograms, obtained by right atrial catheter mapping, were recorded during sinus rhythm from 12 sites of the right atrium in 12 of the 13 group I patients and in all group II patients. An abnormal atrial electrogram was defined as 100 msec or longer in duration, and/or the occurrence of eight or more deflections. Ten (83%) of the 12 group I patients had abnormal atrial electrograms, while only two (10%) of the 20 group II patients had abnormal atrial electrograms, and the difference was significant (P < 0.01). Thirty‐six (26%) of the total 139 electrograms obtained from 12 group I patients and two (1%) of the total 199 electrograms obtained from 20 group II patients fulfilled the criteria for an abnormal atrial electrogram, and the difference was significant (P < 0.01). The fragmented atrial activity zone, interatrial conduction delay zone, and repetitive atrial firing zone obtained by right atrial extrastimulation were significantly wider in group I than in group II, respectively. It was concluded that electrical abnormalities of the atrial muscle may play an important role in the occurrence of paroxysmal atrial fibrillation in patients with Wolff‐Parkinson‐White syndrome.
Improved Chronic Epicardial Pacing in Children: Steroid Contribution to Porous Platinized Electrodes
Authors: KARPAWICH PETER P. , HAKIMI MEDHI , ARCINIEGAS EDUARDO , CAVITT DIANNE L.
Published: July 2006

Although new “low threshold” epicardial electrodes combine steroid with a porous, platinized‐platinum surface, the actual contribution of steroid elution has not been established. We evaluated this new electrode surface design with and without steroid in 13 children, ages 1–22 years. Both electrodes are unipolar and of similar surface area. The Medtronic Model 4951‐P is a barb design for epimyocardial insertion without steroid while the Model 10295A is a steroid elufing, epicardial disk‐shaped design. Both electrodes were implanted for atriai and ventricular pacing. At implant, sensed P and R waves, and pacing impedances were comparable between both electrodes. There were no significant differences between initial measured pulse width or calculated energy thresholds for the first 2 months following implant. Strength‐duration curves for both electrodes at 1 month were comparable to implant values. After 2 months, the threshold of the nonsleroid electrode peaked and stabilized at a significantly higher fP < 0.05) level than the more constant steroid eluting electrode. This difference continued for the first year following implant. We conclude that the new porous, platinized‐platinum electrode design intrinsically limits initial electrode‐tissue interface reactivity in children and improves epicardial pacing with low chronic threshold values. Steroid elution augments these intrinsic qualities by maintaining fibrous capsule stability with more constant low thresholds over time.
Ablation of Ventricular Tachycardia Using Multiple Sequential Transcatheter Application of Radiofrequency Energy
Authors: OEFF MICHAEL , LANGBERG JONATHAN J. , CHIN MICHAEL C. , FINKBEINER WALTER E. , SCHEINMAN MELVIN M.
Published: July 2006

Multiple sequential radio/requency energy was applied in the left and right ventricles of 24 dogs to produce large ablated areas limited to endocardial and subendocardial regions. Endocardial ablation was performed in nine dogs with normal ventricles and 15 that had survived remote myocardial infurcts, three with inducible sustained monomorphic ventriculur tachycardia. A quadripolar catheter was positioned either at the site of earliest ventricular activation during induced monomorphic ventricular tachycardia or at circumscribed areas of the left ventricle, Radio/requency energy was delivered between two adlacent poles of the catheter, successively applying radio/requency energy to the distal, middle, and proximal electrode pairs; this was repeated 9 to 11 times with the catheter in a slightly different position. A cumulative energy of 9,688 ± 4,191 joules resulted in an ablated endocardial/subendocardial surface area of 4.7 ± 2.2 cm2 (range 2.4–10 cm2, maximum depth 4 mm). Sustained tachycardia was not inducible by aggressive programmed ventricular stimulation in the dogs with previously inducible tachycardia, indicating successful ablation of the tachycardia foci. Only seven normal dogs were available for electrophysiological studies; three were used in acute and four in chronic studies. Ventricular tachycardia was not induced in the remaining dogs either before or after radiofrequency ablation, indicating the Jack of an arrhythmogenic effect of this method. Histologic examination was performed in all nine normal dogs (five were sacrificed for acute pathological examination) as well as in the 15 with myocardial infarction. The late pathological examination of the radiofrequency lesion in these 19 animals showed homogeneous areas of coagulation necrosis and endocardial proliferation. Thus, this modified technique of radiofrequency ablation produced large homogeneous endocardial/subendocardial scars suitable for treating ventricular tachycardia and showed no evidence of an arrhythmogenic influence.
MATIC—An Intracardiac Tachycardia Classification System
Authors: LEONG PHILIP HENG WAI , JABRI MARWAN ANWAR
Published: July 2006

The use of an additional atrial sensing electrode together with a morphology recognition algorithm provides a significant, improvement in classification performance over the current rate based algorithms used in implantable cardioverter defibrillator (ICD) devices. The classification system, called morphology and timing intracardiac classifier (MATIC), follows a classification process similar to that used lay cardiologists. Timing between the atrial and ventricular channels is examined using a decision tree and forms the primary criterion for arrhythmia classification. A neural network based morphology classifier is used for cases such as ventricular tachycardia with 1:1 retrograde conduction where timing alone cannot make a reliable decision. MATIC achieves 99.6% correct classification on a database of infracardiac electrogram (ICEG) signals containing 12,483 QRS complexes recorded from 67 patients during electrophysiological studies. Arrhythmias in this database include sinus tachycardia, normal sinus rhythm, normal sinus rhythm with bundle branch block, sinus tachycardia with bundle branch block, atrial fibrillation (AF), various supraventricular tachycardias, ventricular tachycardia, ventricular tachycardia with 1:1 retrograde conduction, and ventricular fibrillation. Within these arrhythmias, there were numerous ventricular ectopic beats, fusion beats, noise, and other artifacts. MATIC addresses the classification problem from start to finish, inputs being raw intracardiac electrogram signals and the outputs being the recommended ICD therapy. Results achieved with MATIC were compared with a classifier used in the Telectronics Guardian ATP 4210, which achieved 75.9% correct classification on the same database. MATIC is simple and efficient, making it suitable for use in a low power implantable device.
New Concept in Activity‐Controlled Pacemakers: Clinical Results With an Accelerometer‐Based Rate Adaptive Pacing System
Authors: ERDELITSCH‐REISER EVA , LANGENFELD HEINER , MILLERHAGEN JAY , KOCHSIEK KURT
Published: July 2006

An accelerometer‐based rate adaptive generator (EXCEL(tm) VR) has been introduced. A preclinical group of 22 subjects with strap‐on devices was observed and reported. A clinical protocol including observation of rate adaptive response to typical daily activities and incremental exercise on a treadmill was administered in seven implanted patients. Indications for implantation in these patients was either second‐ or third‐degree atrioventricular block (five patients, VVIR pacing mode) and sick sinus syndrome (two patients, AAIR pacing mode). Mean pacing rates were 50 ppm (supine), 56 ppm (standing), 77 ppm (descending the stairs), 81 ppm (slow walk), 83 ppm (slow stair climb), 91 ppm (fast walk), and 92 ppm (fast stair climb). When the arm proximal to the pulse generator was exercised, the rate rose to 92 ppm. When the distal arm was strained, the rate was 63 ppm. During treadmill testing, rates between 82 ppm (2 km/hour) and 104 ppm (5 km/hour) were observed. This accelerometer‐based rate adaptive pulse generator provided a proportional response to graded activities of treadmill exercise and daily living in these groups of preclinical and clinical subjects.
Quantitative Relationship Between Atrial Refractoriness and the Dispersion of Refractoriness in Atrial Vulnerability
Authors: TSUJI HIROSHI , FUJIKI AKIRA , TANI MASANAO , YOSHIDA SHIGEKI , SASAYAMA SHIGETAKE
Published: July 2006

We investigated the quantitative relationship between the atrial refractory period and the dispersion of refractoriness with respect to atrial vulnerability in 19 adult mongrel dogs. The atrial effective refractory period (AERP) was measured at the sinus node area (SNA), the low posterior right atrium (LRA), and the distal coronary sinus. The study was performed under the following conditions: (1) control status; (2) hypothermia (30°C); (3) vagus nerve stimulation; and (4) a combination of (2) and (3). The subjects were separated into two groups: atrial fibrillation (AF) (+) group (n = 23), which developed AF by atrial extrastimulus due to increased vulnerability, and AF (−) group (n = 39), which did not develop AF. The mean AERP was 97 ± 23 msec (mean ± SD) in the AF (+) group and 124 ± 23 msec in the AF (−) group, with a significantly shorter refractory period seen in the former (P < 0.001). The dispersion of refractoriness was 59 ± 24 msec in the AF (+) group and 29 ± 18 msec in the AF (−) group, with a significant increase noted in the former (P < 0.001), On X‐Y coordinates (where X denotes the AERP, and Y denotes the dispersion of refractoriness) the data from the AF (+) group were clustered in the upper left region of the graph while the data from the AF (−) group were clustered in the lower right region. These two groups were separated by a linear equation of Y = 0.86X ‐ 57 with a predictability of 90.3%. No difference in the time from SNA stimulation to LRA excitation was found between the groups. On the basis of these results, we suggest that increased atria) vulnerability can be predicted from an analysis of the quantitative relationship between the atrial refractory period and the dispersion of refractoriness.
Programmed Electrical Stimulation of the Ventricle: An Efficient, Sensitive, and Specific Protocol
Authors: FISHER JOHN D. , KIM SOO G. , FERRICK KEVIN J. , ARTOUL SAMIR G. , FINK DANIEL , ROTH JAMES A. , JOHNSTON DEBRA R. , WILLIAMS HENRY R.
Published: July 2006

A relatively simple and evident ventricular programmed electrical stimulation (PES) protocol was developed, capable of achieving high degrees of sensitivity and specificity. In a series of 481 subjects, 1, 2, and 3 extrasfimuli (ES) were used successively during sinus rhythm and ventricular pacing at two drive cycle lengths, at one or more ventricular sites, together with rapid ventricular pacing, and other maneuvers such as isoproterenol infusion. Three ES were used immediately after two ES at each drive rate, rather than returning after completion of the protocol with two ES. Using the protocol, appropriate arrhythmias could be induced in 88% of all patients with ventricularfibrillation, 84% of all patients with sustained ventricular tachycardia (91% with underlying coronary disease), and 58% of patients with severe nonsus‐tained ventricular tachycardia. There were significant differences in inducibility between patients whose ventricular arrhythmias were due to coronary artery disease and other causes. In contrast, sustained ventricular arrhythmias fall ventricular fibrillation) could be induced in only 5% of a control group of control patients, for a specificity of 95%. The protocol described is simpler and more efficient than those that use exhaustive testing of two ES before going to three ES. Three ES during sinus rhythm proved to be the most productive step, with a higher yield ratio (true:false‐positives) than two ES or three ES during pacing, especially at fasterrates. Greater efficiency is also achieved by leaving the timing of an extrastimulus just beyond its effective refractory period when an additional extrastimulus is to be added, compared to protocols in which the extrastimulus is moved later in the cycle and then decremented in tandem with the additional extrastimulus. Coupling intervals < 200 msec produced some false‐positives, but fewer overall than intervals < 200 msec, and with yield ratios comparable to other protocol steps. The protocol described meets NASPE standardsfor ventricular programmed stimulation protocols, and with its demonstrated specificity and relative simplicity and efficiency may be useful as a model for groups not yet committed to an alternative protocol.
The Safety and Efficacy of Chronic Ventricular Pacing at 1.6 Volts Using a Steroid Eluting Lead
Authors: STAMATO NICHOLAS J. , O'TOOLE MICHAEL F. , FETTER JOSEPH G. , ENGER ELAINE L.
Published: July 2006

Steroid eluting leads may allow for lower chronic pacing thresholds and therefore lower pacing outputs. Twenty‐two patients (15 presenting with syncope) were implanted with VVI or VVIR pacemakers and transvenous steroid eluting leads and followed for a mean of 20.6 months while being paced at 1.6 V and 0.6 msec. Mean acute voltage pacing thresholds were 0.40 V at 0.5 msec and chronic pulse width thresholds were 0.22 msec at 0.8 V. Pacemaker function was documented with one to three 24‐hour Holter monitors, attached during the 2–6 week postimplant period, bimonthly transtelephonic monitoring, and monthly pacemaker clinic visits. No patient developed recurrent symptoms and consistent capture ivas verified in all patients on every 24‐hour Holter recording and transtelephonic monitor. Chronic ventricular pacing at an output of 1.6 V at 0.6 msec is safe and effective when using a steroid eluting lead and potentially has implications for pacemaker longevity.
Should a VVIR Pacemaker Increase the Heart Rate with Standing?
Authors: LEITCH JAMES W. , ARNOLD J. MALCOLM , KLEIN GEORGE J. , YEE RAYMOND , RIFF KENNETH
Published: July 2006

To assess the usefulness of incorporating a posture sensor into a ventricular inhibited rate modulated pacemaker, the hemodynamic effects of increasing the ventricular pacing rate with standing were studied in 15 pacemaker dependent patients aged 55 ± 3.5 years. In a randomized cross‐over design, the pacing rate remained at 70 or was increased to 100 beats/mm immediately prior to standing. Blood pressure was monitored continuously and forearm blood flow was measured by venous occlusion plethysmography. There was no difference in supine blood pressure (117 ± 4/63 ± 3 compared to 118 ± 5/64 ± 4 mmHg) or forearm blood flow (2.88 ± 0.36 vs 2.94 ± 0.32 mL/100 mL/min) before the 70 or 100 pacing rate intervention. With standing, blood pressure fell to an equivalent degree at the two pacing rates (fall in mean blood pressure at 70 beats/min 6 ± 4 and of 100 beats/min 8 ± 2 mmHg, P = 0.7). After 1 minute of standing differences in blood pressure were similar, but after 2.5 minutes of standing the increase in mean blood pressure was less at 70 than at 100 beats/min (increase from control 28 ± 2 compared to 36 ± 3 mmHg, P = 0.002). Forearm blood flow decreased after standing for 1 and 2.5 minutes but there was no difference between the 70 and 100 pacing rates (fall in forearm blood flow at 2.5 minutes 0.50 ± 0.24 and 0.59 ± 0.25 mL/100 mL/cm2). In six patients with postural hypotension (fall in mean blood pressure > 10 mmHg at 70 beats/min), pacing at 100 beats/min appeared to lessen the fall in blood pressure with standing (fall 19 ± 4 mmHg compared to 6 ± 4 mmHg respectively, P = 0.07). In contrast, the nine patients without postural hypotension at pacing rate 70 beats/min appeared to be worsened by pacing at 300 beats/min (fall in mean blood pressure, ‐2.5 ± 3 compared to 9 ± 5 mmHg, respectively, P = 0.07). These data indicate that this degree of rate acceleration with standing is unlikely to be generally beneficial in patients dependent upon rate modulated ventricular inhibited pacemakers. In selected patients with significant postural hypotension, there may be a benefit from ventricular rate acceleration with standing.
The Response of Implanted Dual Chamber Pacemakers to 50 Hz Extraneous Electrical Interference
Authors: ASTRIDGE PENELOPE S. , KAYE GERALD C. , WHITWORTH SARAH , KELLY PAUL , CAMM A. JOHN , PERRINS E. JOHN
Published: July 2006

Twenty‐two patients with dual chamber pacemakers with interchangeable lead configuration were exposed to 50 Hz electromagnetic interference. Current, al corporeal levels from 0–600 μA, was applied between electrodes on shoulders and feet using a bedside injection unit. Pacemaker behavior was monitored with telemetered event markers and intracardiac eJectrograms. In bipolar mode, noise reversion mode was induced in all except two Medtronic units at high (> 170 μA) levels of corporeal current, In the Inlermedics, Siemens Pacesetter, and Telectronics models, onset of noise reversion mode was preceded by a window of inappropriate function, characterized by rate acceleration due to atriai maisensing, or pacemaker inhibition due to ventricular nialsensiiig. In unipolar mode, pacemaker malfunction occurred at much lower current levels. Inappropriate behavior preceded the onset of protective noise reversion mode. During current injection, all pacemakers could be interrogated and reprogrammed, and intracardiac telemetry was reliably obtained except in two Medtronic units at high current levels. No pacemaker was reset by the electrical interference, and no cross‐talk was seen. Use of bipolar mode confers a high decree of protection from extraneous electrical interference, but in unipolarmode pacemakers may be inhibited by small amounts of corporeal current, potentially encountered in every day life. The current injection anit allows safe, controllable, and quantifiable investigation of the effects of the electric field induced by a current on implanted pacemakers. Telemetry of annotated intracardiac signals during electromagnetic interference clarifies observations of pacemaker acceleration and inhibition.
Effect of Ibutilide, a New Class III Agent, On Sustained Atrial Fibrillation in a Canine Model of Acute Ischemia and Myocardial Dysfunction Induced By Microembolization
Authors: NABIH MERVAT A. , PRCEVSKI PETAR , FROMM BARBARA S. , LAVINE STEVEN J. , ELNABTITY MOHAMED , MUNIR ASIF , STEINMAN RUSSELL T. , MEISSNER MARC D. , LEHMANN MICHAEL H.
Published: July 2006

The effect of ibutiJide, a new Class III antiarrhythmic agent, upon acute onset atriai fibriJIation was investigated in a closed‐chest canine model of acute left ventricular fLVj dysfunction. Twenty‐four anesthetized mongrel dogs, mean weight 24.9 ± 4 kg were subjected to coronary artery microsphere emboiization and volume Joading, followed by attempted induction of atrial fihrillation (AF) by rapid atrial pacing. Acute ischemic LV dysfunction was successfully induced by emboiization in aii dogs, and caused significant (P < 0.02) decreases in LV systolic pressure, peak + dp/dt (and − dp/dtj, stroke volume, and RR interval; whereas LV end diastolic pressure and QTc significantiy increased. Sustained AF (≥ 30 min) was successfully induced in 15 of 24 dogs (62%) and unsustained AF (< 30 min) was induced in the remainder (38%). At 30 minutes after induction of sustained AF, 15 dogs were randomized to intravenous ibutiiide (0.15 mg/kg, given as a 0.075 mg/kg bolus, followed by 0.075 mg/kg infusion over 1 hour; n = 7) or placebo (saline; n = 8). There were no statistically significant differences between the ibutilide and the placebo groups with respect to mean LV systolic pressure, LV end diastoJic pressure, LV dp/dt, RR intervaJ, or QTc intervaJ during AF prior to infusion. All seven dogs receiving ibutiJide converted to sinus rhythm after a median of 3 minutes (range 0.5–26 min), whiJe onJy three of eight pJacebo dogs (P < 0.03J converted to sinus rhythm after a median duration of 30 minutes (range 15–60 min) (P < 0.04 for difference in time to conversionj. QTc prolonged by 27 ± 17%, 1 hour after ibutiJide, but was unaJtered after pJacebo (P ≥ 0.02). There were no significant hemodynamic changes after either ibutiJide or pJacebo. We concJude that: (1) sustained AF (> 30 min) can be readily induced in this closed‐chest animal model and used t o test antiarrhythmic agents acutely; and (2) intravenous ibutiJide is effective in rapidJy terminating acute onset AF; the drug prolongs the QTc intervaJ but does not exacerbate preexisting hemodynamic compromise in the acutely ischemic LV.
Randomized Cross‐Over Evaluation of Two Adaptive Pacing Algorithms for the Termination of Ventricular Tachycardia
Authors: KANTOCH MICHAL J. , GREEN MARTIN S. , TANG ANTHONY S.L.
Published: July 2006

Objective: In a randomized, cross‐over study we evaluated the efficacy of rate adaptive constant cycle length (BURST)and autodecremental (RAMP)pacing for termination of sustained monomorphic ventricular tachycardia. Methods: An external device capable of delivering the same types ofantitachycardia pacing as the newer generation implantable cardioverter defibrillators wos used. Thirty‐one patients with ischemic and nonischemic cardiomyopathy and documented clinical ventricular tachycardia or ventricularfibrillation were examined during routine invasive electrophysiological studies. RAMP and BURST pacing were each attempted in 54 matched pairs of induced ventricular tachycardia. After a therapy was applied, the tachycardia was reinitiated and the other therapy applied during the second episode so that a total of 108 ventricular tachycardia episodes were studied. Results: Overoll efficacy of ventricular tachycardia pace termination was 69% and the time required to stop ventricular tachycardia was 14.1 ± 11.3 seconds. The ability to terminate ventricular tachycardia by RAMP (72%)or BURST (65%)pacing was not significantly different. However, time to terminate ventricular tachycardia by HAMP (It.8 ± 8.5 sec)was significantly shorter than by BURST (16.4 ± 13.5), P < 0.001. Acceleration of ventricular tachycardia was uncommon with both pacing modes, 7/108 (7%). The ability to pace terminate ventricular tachycardia was cycle length dependant. The highest success was with ventricular tachycardia cycle length between 300 and 350 msec. The success rate decreased with faster and also slower ventricular tachycardia. Conclusions: 1. Rate adaptive pacing methods for ventricular tachycardia termination are effective and safe. 2. Autodecremental fiAMP pacing afford quicker ventricular tachycardia termination than constant cycle length BURST pacing. 3. The ability to terminate ventricalar tachycardia is cycle length dependent with cycle length range of 300–350 msec being most responsive to pace termination
Laser Induced Fluorescence Identification of Sinoatrial and Atrioventricular Nodal Conduction Tissue
Authors: PERK MASIS , FLYNN GREGORY J. , GULAMHUSEIN SAJAD , WEN YUE , SMITH CAROLYN , BATHGATE BEN , TULIP JOHN , PARFREY NOLLAIG A. , LUCAS ALEXANDRA
Published: July 2006

Transcatheter ahlation of nodal tissue is used for the treatment of arrhythmia resistant to medical therapy. We have investigated the use of laser induced fluorescence spectroscopy for the in vitro recognition of nodal conduction tissue. Twelve fresh human necropsy specimens (< 48 hours)were obtained from sinoatrial node and atrioventricular node areas. Spectra were recorded during excitation at 308 nm (XeCl excimer iaser, 1.5–2.0 mJ/puJse, 10 Hz). Each area examined was marked for subsequent histoiogic examination. Four hundred eleven spectra were obtained, of which 37 contained nodai conduction tissue (21 sinoatrial, 16 atrioventricular node). Normalized fluorescence emission intensity from these areas was compared with that of surrounding endomyocardial tissue at 18 wavelengths and 35 ratios of fluorescence intensity at selected wavelengths. Spectra recorded from nodal tissue could be clearly distinguished hy a visible decrease in fluorescence emission intensity at wavelengths from 440 to 500 nm (P < 0.0006 at 450 nm), peak area, and peak width when compared to that of adjacent atrial endomyocardial tissue. Nodal conduction tissue was also distinguished from ventricular endocardium (14 spectra) by an increase in fluorescence emission at 430 to 550 nm (P < 0.0001). The specificity was 73% and 88% and the sensitivity was 73% and 60% for sinus nodal and atrioventricular nodal conduction tissue identification, respectively. A ratio of fluorescence emission intensity > 1.3 for 380/475 nm was able to detect nodal conducfion tissue (P < 0.001). Conclusion. Laser induced fluorescence can differentiate nodal conduction tissue from atrial and ventricular endocardium and may provide a new diagnostic tool for the recognition and subsequent ablation of nodal conduction tissue.
Transiliac Vein Approach to a Rate Responsive Permanent Pacemaker Implantation
Authors: ANTONELLI DANTE , FREEDBERG NAHUM A. , ROSENFELD TIBERIO
Published: July 2006

A 60‐year‐oId patient was admitted for elective replacement of a depleted pulse generator. The pacemaker was implanted 5 years before because of sick sinus syndrome and it was connected to an epicardial lead due to total occlusion of the superior vena cava. The pacing threshold of the epicardial electrode was unacceptabiy high, so an endocardial lead was inserted through the iliac vein. The lead was connected to a VVIR pacemaker, ivhich was located in the abdomen just lateral to the umbilicus. During a 1‐year follow‐up period, the patient felt well and pacemaker performance was satisfactory.
Permanent Pacemaker Positioning Via the Inferior Vena Cava in a Case of Single Ventricle with Loss of Right Atrial‐Vena Cava Continuity
Authors: WEST JOHN N.W. , SHEARMANN CLIFF P. , GAMMAGE MICHAEL D.
Published: July 2006

Successful dual chamber pacing was achieved by implanting permanent pacemaker leads using an extra‐peritoneal approach to the inferior vena cava in a 48‐year‐old patient with a single ventricle, transposition of the great vessels, and a right atrial pulmonary artery shunt (Glenn's procedure). The pacemaker generator was implanted into a subcutaneous pockel in the anterior abdominal wall.
Double Response of the Ventricle During Transient Entrainment in a Common Atrioventricular Nodal Reentrant Tachycardia
Authors: SHIMIZU AKIHIKO , FUKATANI MASAHIKO , CENTURION OSMAR A. , KONOE ATSUSHI , ISOMOTO SHOJIRO , KAIBARA MUNESHIGE , YANO KATSUSUKE
Published: July 2006

We report a patient with slow‐fast atrioventricuiar (AV)nodal reentrant tachycardia, in which double ventricuJar response was demonstrated during rapid pacing at cycle length of 300 msec or less from the high right atrium. The determinants of double ventricular response during transient entrainment in the present case were: (1)a crucial conduction delay in the slow pathway; (2)the collision between the activation via the antegrade fast pathway (antidromically)of the last paced beat and the activation via the antegrade slow pathway (orthodromically)of the previous paced beat, instead of the unidirectional block in the slow pathway; and (3)the enhanced AV nodal conduction over the antegrade fast pathway.
Clinical Efficacy and Safety of the New Cardioverter Defibrillator Systems
Authors: TRAPPE HANS‐JOACHIM , KLEIN HELMUT , FIEGUTH HANS‐GERD , KIELBLOCK BIRGIT , WENZLAFF PAUL , LICHTLEN PAUL R.
Published: July 2006

Clinical efficacy and safety of two new third‐generation implantable cardioverter defibrillators (ICD) were studied in 38 patients with ventricular tachycardia (VT) or fibrillation (VF). There were 31 patients with coronary disease, three patients with right ventricular dysplasia, one patient with dilated cardiomyopathy, and three patients with valvular disease. Twenty‐four patients (group I) received an ICD with monophasic (Ventak PRx 1700, CPI) and 14 patients (group II) with biphasic shocks (Cadence V 100, Ventritex). Intraoperatively, the mean defibrillation threshold was significantly lower in group II than in group I, both in patients with induced VT (group I 11.0 ± 6.3 joules: group N 5.8 ± 1.3 joules) (P < O.01) and induced VF (group I 17.5 ± 4.6 joules; group II 9.6 ± 5.2 joules) (P < O.O1). During the mean follow‐up of 12 ± 7 months four patients (11%) died. 865 arrhythmia events (AE) occurred and were terminated by ATP (671 VTs, 78%). Acceleration of VTs was observed in 28 AE (3%) and ATP was unable to interrupt 58 AE (7%). ICD shocks were delivered as a first therapy in 108 AE (13%).
Effects of Antiarrhythmic Drugs on Epicardial Defibrillation Energy Requirements and the Rate of Defibrillator Discharges
Authors: JUNG WERNER , MANZ MATTHIAS , PFEIFFER DIETRICH , TEBBENJOHANNS JÜRGEN , PIZZULLI LUGIANO , LÜDERITZ BERNDT
Published: July 2006

Antiarrhythmic drugs are commonly used with the implantable cardioverter/defibrillator to treat recurrent ventricular tachyarrhythmias. Since various antiarrhythmic drugs have been reported to alter defibrillation threshold, an important question is whether the device will provide adequate energy for defibrillation during long‐term follow‐up and to what extent antiarrhythmic drug treatment will affect defibrillation energy requirements. To answer these questions, the defibrillation thresholds were determined in 20 patients using an epicardial patch‐patch lead configuration at the time of implantation and at the time of pulse generator replacement. During a mean follow‐up period of 24 ± 6 months, the defibrillation threshold increased significantly from 14.2 ± 3.7 joules to 18.3 ± 5.5 joules in the entire group (P < 0.05). This increase in defibrillation threshold was due to a marked elevation of defibrillation energy requirements in the subgroup of patients taking amiodarone compared with patients receiving mexiletine. Based on these results it is mandatory to retest defibrillation threshold at any time of pulse generator replacement to guarantee continued effectiveness. In particular, if amiodarone treatment is initiated after implantation of a defibrillator, it is recommended to reevaluate defibrillation threshold to ensure an adequate margin of safety.
Bipolar Transseptal Radiofrequency Ablation of AV Node: An Alternative to High Energy Shocks?
Authors: MOLIN FRANCK , DUBUC MARC , HATALA ROBERT , KUS TERESA , NADEAU RÉGINALD
Published: July 2006

Atrioventricular (AV) node ablation to control ventricular response was attempted in two patients with recurrent drug refractory atrial flutter. Standard radiofrequency (RF) procedure, which delivers energy through the 4‐mm tip electrode of an ablation catheter positioned at the right AV junction and a large back plate (unipolar mode), failed in both patients. As an accepted second step, high energy direct current (DC) ablation under general anesthesia was then performed in patient one. After two shocks of 200 J, complete AV block occurred, but complete recovery was noted 3 hours later. In a third session for patient 1 and in the first session for patient 2 (after 15 unsuccessful unipolar right‐sided RF applications), a second ablation catheter was introduced via the femoral artery on the left side of the His bundle area under the aortic valves. Energy was then delivered in a bipolar fashion between the tip electrodes of the right‐sided and the left‐sided catheter. Complete and permanent AV block (follow‐up: 3 and 1 months) was created within 4 and 1.5 seconds, respectively, in each patient. No complication was encountered and echocardiograms and blood levels of cardiac enzymes were all normal after the procedures. This new approach, after further evaluation, may represent a useful additional step in the strategy of AV node ablation and could be applied before high energy DC shock when the standard RF procedure is unsuccessful.