bluuebunny/crossref_metadata_2025 huggingface dataset:
Variable Effects of Adenosine on Retrograde Conduction in Patients with Atrioventricular Nodal Reentry Tachycardia
Authors: FISHBERGER STEVEN B. , MEHTA DAVENDRA , ROSSI ANTHONY F. , LANGAN M. NOELLE , MARX STEVEN O. , GOMES J. ANTHONY
Published: July 2006

Adenosine has been demonstrated to reliably produce transient block of atrioventricular nodal (AVN) conduction, and has been advocated as a method of differentiating retrograde conduction via the atrioventricular node from accessory pathway conduction. However, the response of retrograde AVN to adenosine in patients with typical atrioventricular nodal reentry tachycardia (AVNRT) remains unclear. We evaluated 13 patients (mean age 45 ± 20 years) with typical AVNRT prior to AVN modification. During right ventricular pacing, a rapid bolus of adenosine (0.2 mg/kg; maximum 18 mg) was administered. Adenosine sensitivity, defined by transient ventriculoatrial block, was observed in six patients, while in seven patients ventriculoatrial conduction was unaffected. An adenosine bolus administered during sinus rhythm or atrial pacing resulted in antegrade atrioventricular block in all the adenosine resistant patients in whom this was performed (n = 6). Comparisons of AVN electrophysiological characteristics between the adenosine sensitive and adenosine resistant patients were performed. There was no difference with respect to ventriculoatrial effective refractory period, ventriculoatrial Wenckebach, AVNRT cycle length, and His to atrial echo interval in AVNRT. However, there was a trend toward a longer antegrade fast pathway ERP in the adenosine sensitive group (P = 0.07). Electrophysiological properties do not predict retrograde AVN adenosine sensitivity. Adenosine does not cause retrograde AVN block in all patients with AVNRT, and therefore cannot reliably distinguish between retrograde conduction via the AVN or an accessory pathway.
Implantable Defibrillator Diagnostic Storage Capabilities: Evolution, Current Status, and Future Utilization
Authors: SARTER BRIAN H. , CALLANS DAVID J. , GOTTLIEB CHARLES D. , SCHWARTZMAN DAVID S. , MARCHLINSKI FRANCIS E.
Published: July 2006

There has been a rapid and significant evolution in the stored diagnostic information available from implantable cardioverter defibrillatars (ICDs). The diagnostic information available in current generation ICDs has greatly enhanced the clinicians' ability to determine the rhythm triggering device therapy as well as to identify potential problems with the ICD system. Furthermore, this information may be useful in identifying triggers of ventricular arrhythmias in patients at high risk for sudden death. The history, evolution, value, and limitations of the stored diagnostic capabilities of implantable defibrillators are discussed.
Carotid Sinus Massage as a Diagnostic and Therapeutic Tool for Atrial Flutter‐Fibrillation
Authors: KIRCHHOF C.J.H.J. , GORGELS A.P.M. , WELLENS H.J.J.
Published: July 2006

Alterations in vagal tone can influence the atrial fibrillatory process by changing the atrial refractory period. We observed in a patient with paroxysmal atrial fibrillation (AF) that carotid sinus massage (CSM) changed a “coarse” type of fibrillation into a “fine” type, followed by termination of the arrhythmia. Although coincidental conversion of AF into sinus rhythm could not be excluded, we concluded that it is worthwhile to try CSM in every patient presenting with AF prior to other interventions to restore sinus rhythm.
Impedance Rise, Only Clue to Severe Insulation Damage in a Transvenous Single‐Lead AICD‐System
Authors: SCHIBGILLA VOLKER , DIEM BJÖRN , MAHMOUT OMAR , JANßEN GERHARD , EMDE JÜRGEN V.D. , BACHMANN KURT
Published: July 2006

We report a case of severe insulation damage 10 months after implantation of a fourth‐generation single‐lead implantable cardioverter defibrillator in a 45‐year‐old patient with dilative cardiomyopathy. The measured impedance was > 2000 Ohm and decreased to < 100 Ohm after sligbt pressure was applied to the device. All other parameters including intracardiac ECGs and markers were normal. Despite this delicate finding operative exploration revealed severe insulation damage of the pace‐sense arm of the plug and insulation loss proximal to the distal coil of the lead.
Effects of Pharmacological Autonomic Blockade on Dual Atrioventricular Nodal Pathways Physiology in Patients with Slow‐Fast Atrioventricular Nodal Reentrant Tachycardia
Authors: LIN LI‐JEN , LIN JIUNN‐LEE , LAI LING‐PING , CHEN JYH‐HONG , TSENG YUNG‐ZU , LIEN WEN‐PIN
Published: July 2006

The purpose of this study was to investigate the atrioventricular AV nodal physiology and the inducibility of AV nodal reentrant tachycardia (AVNRT) under pharmacological autonomic blockade (AB). Seventeen consecutive patients (6 men and 11 women, mean age 39 ± 17 years) with clinical recurrent slow‐fast AVNRT received electrophysiological study before and after pharmacological AB with atropine (0.04 mg/kg) and propranolol (0.2 mg/kg). In baseline, all 17 patients could be induced with AVNRT, 5 were isoproterenol‐dependent. After pharmacological AB, 12 (71 %) of 17 patients still demonstrated AV nodal duality. AVNRT became noninducible in 7 of 12 nonisoproterenol dependent patients and remained noninducible in all 5 isoproterenol dependent patients. The sinus cycle length (801 ± 105 ms vs 630 ± 80 ms, P < 0.005) and AV blocking cycle length (365 ± 64 ms vs 338 ± 61 ms, P < 0.005) became shorter after AB. The antegrade effective refractory period and functional refractory period of the fast pathway (369 ± 67 ms vs 305 ± 73 ms, P < 0.005; 408 ± 56 ms vs 350 ± 62 ms, P < 0.005) and the slow pathway (271 ± 30 ms vs 258 ± 27 ms, P < 0.01; 344 ± 60 ms vs 295 ± 50 ms, P < 0.005) likewise became significantly shortened. However, the ventriculoatrial blocking cycle length (349 ± 94 ms vs 326 ± 89 ms, NS) and effective refractory period of retrograde fast pathway (228 ± 38 ms vs 240 ± 80 ms, NS) remained unchanged after autonomic blockade. Pharmacological AB unveiling the intrinsic AV nodal physiology could result in the masking of AV nodal duality and the decreased inducibility of clinical AVNRT.
Automatic Adaptation of the Basic Pacing Rate in Response to Minute Ventilation
Authors: LIMOUSIN MARCEL , PIOGER GUY , BONNET JEAN‐LUC , GEROUX LAURENCE ,   on behalf of the Chorum French Investigational Group.
Published: July 2006

Rate responsive pacing based on minute ventilation (VE) correlates highly with metabolic demand. This type of sensing also recognizes extended periods of rest. The Chorum pacemaker includes a rate responsive algorithm that modulates the basic rate according to phases of activity versus sleep. Forty‐six patients (mean age 78 ± 15), received a Chorum pacemaker for atrioventricular block in 17 cases, sick sinus syndrome in 25, and mixed disorders in 4. Holter monitoring was performed to analyze heart rate and to examine the circadian adaptation of the minimal pacing rate. The mean basic rate was programmed at 63 ± 5 beats/min, and the sleep rate at 52 ± 4 beats/min. Seventeen patients had spontaneous heart rates consistently above the programmed basic rate, and 6 had sustained supraventricular tachyarrhythmias. One‐half of the patients had periods of pacing at the programmed sleep rate. The mean diurnal pacing rate was 68 ± 5 beats/min compared to a mean nocturnal rate of 60 ± 4 beats/min (P < 0.0001). The average time spent at the basic rate was 37 ± 30 min (0–110) during daytime (4%), versus 242 ± 153 min (20–477) at night (45%, P < 0.0001). No adverse effect was observed in this patient population. VE allows a reliable detection of the sleeping periods as well as an adjustment of the basic rate in accordance. Caution is advised in cases of bradycardia dependent tachyarrbythmias.
Myocardial Injury Induced by Radiofrequency and Low Energy Ablation: A Quantitative Study of CK Isoforms, CK‐MB, and Troponin‐T Concentrations
Authors: KATRITSIS DEMOSTHENES G. , HOSSEIN‐NIA MOJGAN , ANASTASAKIS ARIS , POLONIECKI JAN , HOLT DAVID W. , CAMM A. JOHN , WARD DAVID E. , ROWLAND EDWARD
Published: July 2006

We conducted a prospective, controlled study to investigate the use of CK‐MB concentration and newer methods such as troponin‐T concentration and CK isoforms, in the assessment of myocardial damage caused by radiofrequency current or low energy DC catheter ablation. The study population consisted of 3 consecutive patients who underwent low energy catheter ablation, 28 consecutive patients subjected to radiofrequency ablation, and 4 patients wbo were subjected to radiofrequency energy ablation but also bad external DC shocks for cardioversion of atrial fibrillation that occurred during the procedure. The control group comprised eight subjects undergoing electrophysiological study. Prior to ablation and at 30 minutes, 1,2,6, and 12 hours following the procedure, serial blood samples were taken for measurement of troponin‐T and CK‐MB concentrations, and calculation of the MM3/MM1 and MB2/MB1 ratios.

Troponin‐T concentration was raised above normal in all patients subjected to low energy ablation and in all but two patients subjected to radiofrequency ablation. Only 42% of all patients subjected to ablation had at least one raised CK‐MB concentration postablation. The MB2/MB1 ratio was raised in all but two patients following radiofrequency or low energy ablation but it was also abnormal in the preablation samples in nine patients. The MM3/MM1 ratio failed to detect myocardial damage in 71 % of all patients. There was a statistically significant difference between the control and patient groups regarding all four indices of myocardial damage. Low energy ablation caused a significantly higher degree of myocardial damage compared with radiofrequency (RF); this effect could not be attributed to different numbers of total energy discharges. Our results indicate that catheter ablation, regardless of the mode of energy used, inflicts detectable injury upon the myocardium. This injury can be quantitated by using newer analytical techniques, such as serial, postablation measurements of troponin‐T concentration.
The Effects of Ventricular Pacing on Left Ventricular Geometry, Function, Myocardial Oxygen Consumption, and Efficiency of Contraction in Conscious Dogs
Authors: OWEN CLARENCE H. , ESPOSITO DAVID J. , DAVIS JAMES W. , GLOWER DONALD D.
Published: July 2006

The effects of ventricular pacing on left ventricular (LV) dynamic geometry, function, and myocardial oxygen consumption (MVO2) were measured in 12 conscious dogs using sonomicrometry, micromanometry, ultrasonic flow probes, and oximetry catheters during right atrial (A‐) and right ventricular (V‐) pacing at 150 beats/mm. Systolic function was quantified using slopes (Mw) and volume‐intercepts (Vw) of linear relationships between end‐di‐astolic volume (EDV) and stroke work (SW) for data obtained during vena caval occlusion. V‐pacing shifted SW‐EDV relationships downward (Mw decreased from 97 ± 21 to 81 ± 21 Kerg/mL) and to the right (Vw increased from 14 ± 11 to 20 ± 12 mL) in comparison with A‐pacing (P < 0.05). These functional changes correlated with altered contractile geometry manifest as early shortening in the septal free wall relative to anterior‐posterior dimension (increased minor axis mid‐wall eccentricity at end‐diastole and begin‐ejection). Steady‐state LV power output decreased from 802 ± 213 mW during A‐pacing to 514 ± 170 mW during V‐pacing (P < 0.05), while MVO2 remained relatively unchanged during V‐pacing (10 ± 3 mL O2/min vs 11 ± 3 mL O2/min during A‐pacing, P = NS). As a result, overall LV efficiency decreased from 0.24 ± 0.08 during A‐pacing to 0.16 ± 0.06 during V‐pacing (P < 0.05). These data illustrate the impact of V‐pacing on dynamic LV geometry and function, including impaired LV work output at all physiological levels of preload. Most importantly, the relationship between LV work output and MVO2 is depressed during V‐pacing, emphasizing the interaction between LV mechanics and pump efficiency in intact subjects. As a result, measures taken to restore normal contractile geometry might improve LV efficiency and performance when V‐pacing is necessary.
The Development of Sinoatrial Dysfunction in Pacemaker Patients with Isolated Atrioventricular Block
Authors: MORSI AMR , LAU CHING , NISHIMURA SANDRA , GOLDMAN BERNARD S.
Published: July 2006

The purpose of this paper is the assessment of sinus node competence over time in patients with isolated atrioventricular block (AV block). Patients implanted with AV synchronous pacemakers for isolated A V block between December 1993 and June 1995 were prospectively evaluated at predischarge, 6 weeks, and subsequent 6 months follow‐up with respect to atrial rate monitors/24‐hour Holter and modified exercise test. Patients unable to maintain AV synchronous pacing or complete a modified exercise test were excluded. Sinus node competency is interpreted as: (1) absence of atrial brady‐ or tach‐yarrhythmia, (2) ability to achieve a minimum heart rate of 100 beats/min with modified exercise test or during daily activities. There were 58 patients (22 women), mean age 71.0 ± 13.8 with an average follow‐up of 30.4 months (11–40). Three patients did not complete a modified exercise test, 4 patients were lost to follow‐up, and 2 patients were unable to maintain AV synchronous pacing. Of the remaining 49 patients, 3 developed chronic or paroxysmal atrial fibrillation. No patient developed significant bradyarrhythmias. All patients achieved a heart rate of ≥ 100 beats/min modified exercise test. In our group of patients with isolated AV block within a moderate follow‐up period, development of Sinoatrial dysfunction was rare (6%). A longer follow‐up is required to delineate the natural history of Sinoatrial dysfunction in patients with isolated AV block.
Identification and Ablation of Macroreentrant Ventricular Tachycardia with the CARTO Electroanatomical Mapping System
Authors: STEVENSON WILLIAM G. , DELACRETAZ ETIENNE , FRIEDMAN PETER L. , ELLISON KRISTIN E.
Published: July 2006

Monomorphic ventricular tachycardias associated with regions of scar are most commonly due to reentry. Catheter based techniques have recently been described for mapping of reentry circuits. Fluoroscopic methods have obvious limitations when attempting to map large ventricular reentry circuit and localize target‐sites of radiofrequency ablation. Three‐dimensional right ventricular endocardial mapping was performed in a 38‐year‐old patient with ventricular tachycardia 28 years after surgical correction of tetralogy of Fallot by using the CARTO electroanatomical system. The map of electrogram voltage showed low amplitude electrograms over the anterior wall of the right ventricle extending into the right ventricular outflow tract, consistent with the location of the ventriculotomy scar. Recording of local activation time was combined with entrainment mapping to define the macroreentrant circuit during ventricular tachycardia. Since the activation propagated through a broad path around the right ventriculotomy scar, ablation was performed by creating a line of block, which was facilitated by tagging of the lesion sites on the endocardial activation map. Large ventricular reentry circuits can be identified and interrupted by creation of a line of block to interrupt a broad path. A practical approach to mapping combining analysis of electrogram voltage, activation sequence, and entrainment is presented.
Evolution and Revolution in Drug Labeling: Regulation of Antiarrhythmic Drugs by the Food and Drug Administration 1962–1996
Authors: PRITCHETT EDWARD L.C.
Published: July 2006

Between 1962, when the Kefauver‐Harris Drug Amendments were passed, and 1996, 20 pharmaceutical compounds were approved and labeled by the FDA as effective antiarrhythmic drugs for some specified cardiac arrhythmia. Drug research and development in the 1970s and 1980s were focused on treatment of premature ventricular beats as a marker for sudden cardiac death and ventricular tachycardia. The Cardiac Arrhythmia Suppression Trial in 1989 irrevocably altered this approach. Recent drug development programs have targeted atrial fibrillation (AF) as epidemiologic data have predicted an increase in the incidence of AF as the United States population ages, and as treating premature ventricular beats has fallen from favor. The FDA, the scientific community, and the pharmaceutical industry have all participated in and been affected by this evolution in drug development.
Paradoxically Shortened QT Interval after a Prolonged Pause
Authors: TAKAHASHI NAOHIKO , ITO MORIO , ISHIDA SHUJI , NAKAGAWA MIKIKO , HARA MASAHIDE , SAIKAWA TETSUNORI , SAKATA TOSHIIE
Published: July 2006

We analyzed Holter ECG recordings in 15 patients with episodes of prolonged RR intervals > 2.5 seconds. In 13 patients, the QT interval showed a linear prolongation when RR interval was < 1.5 seconds and became relatively flat at longer RR intervals. In the remaining two patients, the QT and RR intervals were correlated within physiological range of RR intervals. However, at longer RR intervals, the QT interval was unexpectedly shortened and constant. The paradoxically shortened QT interval observed in the present 2 cases may indicate an abnormal adaptation of repolarization time to an abrupt increase in the preceding RR intervals.
Complete Atrioventricular Block with Unwidened QRS Complex During Hyperkalemia
Authors: TIBERTI GIANLUCA , BANA GILBERTO , BOSSI MARIO
Published: July 2006

Purkinje and ventricular myocardial fibers are thought to be more sensitive to hyperkalemia than sinoatrial and atrioventricular (AV) nodes, although complete AV block due to hyperkalemia can occur. We describe a case in which hyperkalemia in a patient affected by renal failure is responsible for complete AV block without QRS complex prolongation. Temporary endoventricular pacing was essential in restoration of adequate renal blood flow and excretion of exceeding serum potassium with subsequent normalization of AV conduction.
Chronic Atrial Lead Explantation Using a Staged Percutaneous Laser and Open Surgical Approach
Authors: VARMA NIRAJ , SELLKE FRANK W. , EPSTEIN LAURENCE M.
Published: July 2006

We report a staged approach to the explantation of a passive fixation atrial lead 4 years after implantation in a patient with extracardiac J wire protrusion. The body of the lead, from the venous entry site to the proximal electrode, was freed from extensive fibrous binding using an investigational Excimer laser lead extraction sheath. The distal end and J wire were freed and the lead was removed at thoracotomy. This staged approach offered a safe and effective method for the removal of a heavily fibrosed chronic endocardial lead.
Inadvertent Implantation of an ICD Lead in the Great Cardiac Vein
Authors: TARRAGANO FRANÇOIS , KLUG DIDIER , LACROIX DOMINIQUE , KACET SALEM
Published: July 2006

We report an implantable cardioverter defibrillator (ICD) implanted with a single lead inadvertently introduced in the great cardiac vein. No venous lesion was caused by the shocks and the position of the lead remained stable. This case emphasizes the usefulness of different fluoroscopic views during ICD implantation.
Usefulness of Plasma Catecholamines During Head‐Up Tilt as a Measure of Sympathetic Activation in Vasovagal Patients
Authors: YAMANOUCHI YOSHIO , SHEHADEH ABBAS A. , FOUAD‐TARAZI FETNAT M.
Published: July 2006

Vasovagal syncope is a common clinical disorder which has been traditionally related to a vasovagal reflex precipitated by an initial excess sympathetic stimulation. We hypothesized that the increase in plasma Catecholamines during head‐up tilt is more accentuated in patients with tilt induced vasovagal syncope. To test this hypothesis, plasma Catecholamines were measured in supine posture and during head‐up tilt in patients with a history suggestive of vasovagal syncope. Of these, 13 had a normal response to tilt (nonvasovagal group; age 41 ± 19 [SD]years) and 11 had a vasovagal response to tilt (vasovagal group; 39 ± 20 years). In the supine posture at rest, plasma epinephrine and norepinephrine were not significantly different between the nonvasovagal and the vasovagal groups (39 ± 28 ng/L vs 46 ± 38 ng/L, P = 0.5792, 335 ± 158 ng/L vs 304 ± 124 ng/L, P = 0.6007, respectively). Furthermore, the tilt induced changes in plasma epinephrine and norepinephrine were not different between the two groups (20 ± 20 ng/L vs 35 ± 55 ng/L, P = 0.3562, 264 ± 158 ng/L vs 242 ± 205 ng/L, P = 0.7724, respectively) suggesting that differences in the hemodynamic response to tilt are not predictable by the supine levels of circulating plasma Catecholamines, and that the extent of plasma catecholamines increase during tilt does not determine the hemodynamic outcome of the tilt test. Since orthostatic changes of plasma Catecholamines could be influenced by volume factors, we assessed plasma renin activity and aldosterone as surrogates of blood volume. Baseline plasma renin activity and aldosterone were not significantly different between the two groups. We conclude that inasmuch as plasma catecholamines reflect the status of sympathetic activity, our data do not support the hypothesis that accentuation of sympathetic activity precedes necessarily the tilt induced vasovagal syncope. However, one should take in consideration that multiple factors may influence catecholamine levels and catecholamines kinetics. A hyperresponsiveness of β‐receptors to Catecholamines in patients with vasovagal syncope may be suggested but needs to be tested.
Association between Cardiac Autonomic Function and Coping Style in Healthy Subjects
Authors: RAMAEKERS DIRK , ECTOR HUGO , DEMYTTENAERE KOEN , RUBENS AN , VAN DE WERF FRANS
Published: July 2006

The link between personality and cardiac function is insufficiently characterized. We postulated that in a healthy population, cardiac autonomic function is linked to coping style. In 276 healthy volunteers, between the ages of 18 and 71, the Utrecht Coping List was used to evaluate different coping strategies. Trait anxiety was scored by the Spielberger State Trait Anxiety Inventory. A 24‐hour Holter recording was used to calculate heart rate variability (HRV). For HRV parameters and coping mechanisms this study demonstrated gender‐specific differences and correlations with age. In men (n = 141) higher active coping was associated with less global autonomic activity or SDANN (rs=−0.27, P < 0.001). This relationship was most prevalent in young (18–30 years) men (rs=−0.45, P < 0.005). Higher expression of negative emotions or anger was related to both higher vagal (rs= 0.23 for rMSSD, P < 0.01) tone and higher LF power (rs= 0.23, P < 0.01). In young men expression of negative emotions or anger was associated with LF power (rs= 0.37, P < 0.01) and in middle‐aged (31–50 years) men with vagal tone (rs= 0.43 for rMSSD, P < 0.005) and heart rate (rs=−0.41, P < 0.005). Higher comforting ideas was related to higher LF power (rs= 0.23 for LF power, P < 0.005), and this especially in middle‐aged men (rs= 0.37, P < 0.01). In women (n = 135), no significant correlations between coping style and HRV indices were found. We conclude that in normal individuals, at least in men, our findings suggest a relationship between coping style and cardiac autonomic function.
Koch's Triangle in Pediatric Age: Correlation with Extra‐ and Intracardiac Parameters
Authors: FRANCALANCI PAOLA , DRAGO FABRIZIO , AGOSTINO DOMENICO ANTONIO , DI LISO GAETANO , DI GIOMMO VINCENZO , BOLDRINI RENATA , RAGONESE PIETRO , BOSMAN CESARE
Published: July 2006

The atrioventricular node is situated in the lower atrial septum, at the apex of the Koch's triangle. The dimensions of the Koch's triangle are studied in adult humans, while no data exist about tbem in pediatric age. the knowledge of the dimensions of Koch's triangle in childhood is very important for safe and correct application of radiofrequency energy during transcatheter ablation. The dimensions of Koch's triangle were determined in 69 human pediatric hearts. the median age of the children was 3 months. with a range from 1 day to 14 years, 30 were female and 39 were male. Relations between body weight (extracardiac parameter) and tricuspid valve diameter (intracardiac parameter) were determined in all hearts to sbow morpbometric modifications with growth. the distribution of body weight was not Gaussian and no correlation could be obtained between Koch's triangle dimensions and body weight. However, it was possible to identify that the mean ratio between the cathetus of the Koch's triangle corresponding to the annulus of the tricuspid valve and the tricuspid valve diameter was 0.45 ± 0.16, with a highly significant correlation coefficient (r = 0.653, P < 0.001). Therefore, by knowing: (1) the diameter of the tricuspid valve, and (2) the constant ratio between the cathetus of the Koch's triangle and the tricuspid valve diameter, it is possible to calculate the lengtb of the segment of the tricuspid annulus along wbich the transcatheter application of radiofrequency current can be applied to ablate the slow‐pathway, tbus reducing the risks of damage of the atrioventricular node.
Reversion to Back‐Up Mode (VOO) in a DDD Pacemaker Model
Authors: TURNER MARK , ZACHARKIW LINDA , MARSHALL ANDREW J.
Published: July 2006

Sorin recently identified mode reversion to backup mode (VOO). They estimate a prevalence of 1% and suggest electromagnetic interference (EMI) as the cause. We identified ten patients being followed in our pacing clinic, of whom four were found to have suffered mode reversion. We, therefore, conclude that the prevalence of this problem may be greater than predicted. None of the patients who were found to have mode reversion gave any history to suggest that they had been exposed to EMI.
Radiofrequency Ablation of Idiopathic Left Ventricular Tachycardia with Changing EGG Morphology
Authors: CHEN YI‐JEN , CHEN SHIH‐ANN , TAI CHING‐TAI , CHIANG CHERN‐EN , LEE SHIH‐HUANG , WEN ZU‐CHIN , YU WEN‐CHUNG , FENG AN‐NING , CHANG MAU‐SONG
Published: July 2006

Idiopathic left ventricular tachycardia is a distinct clinical entity with a typical ECG of right bundle branch block and left axis deviation. We presented a 39‐year‐old man with idiopathic left ventricular tachycardia, which demonstrated change in the configuration of QRS complex during successive radiofrequency catheter ablation. We proposed that this idiopathic left ventricular tachycardia may have alternative pathways within the reentrant circuit leading to different exits.
Triple Chamber Pacemaker for End‐Stage Heart Failure in a Patient with a Previously Implanted Automatic Defibrillator
Authors: LE FRANC PIERRE , KLUG DIDIER , LACROIX DOMINIQUE , JARWE MUSTAFA , KOUAKAM CLAUDE , KACET SALEM
Published: July 2006

A 63‐year‐old man with an ischemic dilated cardiomyopathy previously implanted with an implantable cardioverter defibrillator (ICD) received a triple chamber pacemaker as an ultimate therapeutic resort for end‐stage congestive heart failure. After implant, the tolerance to physical exercise increased and NYHA class decreased from III to II. Echocardiography assessed ventricular contraction resynchronization during DDD biventricular pacing as compared to VVI pacing. No major pacemaker‐ICD interaction was noted during testing or follow‐up. We conclude that sequential biventricular pacing is feasible in the presence of an ICD.
Asymptomatic Superior Vena Caval Occlusion: A Complication of Nonthoracotomy Implantation of Cardioverter Defibrillator
Authors: MINEN GIORGIO , PROCLEMER ALESSANDRO , FACCHIN DOMENICO
Published: July 2006

A patient with ischemic dilated cardiomyopathy and history of ventricular fibrillation received an implantable Cardioverter defibrillator by the nonthoracotomy approach. Four years later, during elective replacement of an exhausted pulse generator, a superior vena caval thrombotic occlusion with collateral circulation through the azygos and emiazygos vein systems was documented. This occlusion occurred despite an anticoagulant treatment in the standard therapeutic range. We speculate that thrombotic occlusion might be secondary to a mechanical vessel injury.
Quantification of the Modifications in the Dominant Frequency of Ventricular Fibrillation under Conditions of Ischemia and Reperfusion: An Experimental Study
Authors: CHORRO FRANCISCO J. , GUERRERO JUAN , CANOVES JOAQUIN , MARTÍNEZ‐SOBER MARCELINO , MAINAR LUIS , SANCHIS JUAN , CALPE JAVIER , LLAVADOR ESTEBAN , ESPÍ JOSÉ , LÓPEZ‐MERINO VICENTE
Published: July 2006

The characteristics of ventricular fibrillatory signals vary as a function of the time elapsed from the onset of arrhythmia and the maneuvers used to maintain coronary perfusion. The dominant frequency (FrD) of the power spectrum of ventricular fibrillation (VF) is known to decrease after interrupting coronary perfusion, though the corresponding recovery process upon reestablishing coronary flow has not been quantified to date. With the aim of investigating the recovery of the FrD during reperfusion after a brief ischemic, period, 11 isolated and perfused rabbit heart preparations were used to analyze the signals obtained with three unipolar epicardial electrodes (E1‐E3) and a bipolar electrode immersed in the thermostatizfid organ bath (E4), following the electrical induction of VF. Recordings were made under conditions of maintained coronary perfusion (5 min), upon interrupting perfusion (15 mini, and after reperfusion (5 min), FrD was determined using Welch's method. The variations in FrD were quantified during both ischemia and reperfusion, based on an exponential model AFrD = A exp (‐t/C). During ischemia ΔFrD is the difference between FrD and the minimum value, while t is the time elapsed from the interruption of coronary perfusion. During reperfusion ΔFrD is the difference between the maximum value and FrD, while t is the time elapsed from the restoration of perfusion, A is one of the constants of the model, and C is the time constant. FrD exhibited respective initial values of 16.20 ± 1.67, 16.03 ± 1.38, and 16.03 ± 1.80 Hz in the epicardial leads, and 15.09 ±1.07 Hz in the bipolar lead within the bath. No significant variations were observed during maintained coronary perfusion. The fit of the FrD variations to the model during ischemia and reperfusion proved significant in nine experiments. The mean time constants C obtained on fitting to the model during ischemia were as follows: El =294.4 ± 75.6, E2 = 225.7 ± 48.5, E3 = 327.4 ± 79.7, and E4 = 298.7 ± 43.9 seconds. The mean values of C obtained during reperfusion, and the significance of the differences with respect to the ischemic period were: El = 57.5 ± 8.4 (P ± 0.01), E2 = 64.5 ± 11.2 (P0.01), E3 = 80.7 ± 13.3 (P < 0.01), and E4 = 74.9 ± 13.6 (P < 0.0001). The time course variations of the FrD of the VF power spectrum fit an exponential model during ischemia and reperfusion. The time constants of the model during reperfusion after a brief ischemic period are significantly shorter than those obtained during ischemia.
Mid‐ and Long–Term Similarity of Ventricular Response to Paroxysmal Atrial Fibrillation: Digoxin versus Placebo
Authors: HNATKOVA KATERINA , MURGATROYD FRANCIS D. , POLONIECKI JAN , WAKTARE JOHAN E.P. , ALFERNESS CLIF A. , CAMM A. JOHN , MALIK MAREK
Published: July 2006

The effects of digoxin on ventricular response during atrial fibrillation (API and consequent effects on arrhythmic symptoms have still not been fully explained. This study investigated whether the treatment by digoxin contributes to mid– and long–term stabilization of ventricular cycles in patients with paroxysmal AF. A population of 45 patients with paroxysmal AF underwent 24–hour ECG recordings during each arm of a randomized crossover trial comparing digoxin and placebo. This yielded 30 Holter recordings from 22 patients that contained AF episodes lasting in excess of 2 minutes and with acceptably low Holter noise. Each AF episode was divided into nonoverlapping segments of 30 seconds and the distribution of RR intervals in each segment was compared with the distribution of all other AF segments in the same recording using the Kolmogorov–Smimov test. The percentage of tests that revealed significant differences at levels of P ≤ 0.01, and P ≤ 0.001 were sorted according to the time between the segments compared. The comparisons of these results were performed between: (a) all recordings on placebo (n = 16) and all recordings on digoxin (n = 14), and (b) between recordings on placebo and on digoxin in 8 patients in whom paired analysis was possible. Adjacent AF segments (distance 0) differed significantly only in < 30% of both recordings on placebo and on digoxin. However, with increasing the distance between segments, the proportion of the significant differences between RR interval distributions increased more with placebo than with digoxin (P < 10−300, Chi‐square test). Paired data revealed larger differences between placebo and digoxin with increasing distance between segments. Thus in patients with paroxysmal AF, digoxin leads to more reproducible patterns of ventricular cycles that may be better tolerated clinically.
Early Benefit of Implantable Cardioverter Defibrillator Therapy in Patients Waiting for Cardiac Transplantation
Authors: LORGA‐FILHO ADALBERTO , GEELEN PETER , VANDERHEYDEN MARC , MALACKY TIBOR , PRIMO JOAO , GOETHALS MARC , WELLENS FRANCIS , BRUGADA PEDRO
Published: July 2006

The ICD can effectively recognize and treat ventricular arrhythmias that can lead to sudden death. Sudden death is a major problem in patients awaiting heart transplantation. We reviewed our experience with the ICD in patients with malignant ventricular arrhythmias waiting for cardiac transplantation. Nineteen patients were included. Seventeen were men, mean age was 54 ±11 years (range 17–66) and the left ventricular ejection fraction was 22%± 10% (range 9%–46%). After a mean follow–up of 6 ± 5 months (range 1–20 months), 17 patients reached heart transplantation. One patient died and the other is waiting for a transplant. Before transplantation 71 % of patients received an appropriate discharge. The mean time to the first appropriate discharge was 2 ± 2 months (range < 1–6 months), which was significantly shorter than the mean time to first discharge in the other patients (n = 182) receiving a defibrillator in our center (11 ±10 months; range 1–58 months) (P < 0.0004). In conclusion, cardiac transplantation candidates with life–threatening ventricular arrhythmias can effectively be protected against sudden arrhythmic death by ICD. These patients have a high incidence of appropriate shocks occurring very early after implantation.
Worldwide Clinical Experience with aDown‐Sized Active Can ImplantableCardioverier Defibrillator in 162 ConsecutivePatients
Authors: STICHERLING CHRISTIAN , KLINGENHEBEN THOMAS , CAMERON DOUGLAS , HOHNLOSER STEFAN H. ,   Worldwide 7221 ICD Investigators
Published: July 2006

Treatment with an ICD is the first‐line treatmentfor survivors of sudden cardiac death. More recently, evidence accumulates that prophylactic ICD therapy may be beneficial for selected subgroups of patients after myocardial infarction. Particularly for future studies on the value of prophylactic ICD therapy, downsized devices are needed to allow easy pectoral implantation with a single lead configuration and featuring extended memory capabilities.Accordingly, this study assesses the clinical performance of a downsized fourth‐generation ICD in 162consecutive patients. All devices could be successfully implanted pectorally, in 96% with a single leadconfiguration with a low defibrillation threshold of 10.6 ± 5.2 J. During a 3‐month follow‐up, 26% of thepatients received ICD therapy. Twenty percent had appropriate therapy for ventricular fibrillation (n= 9) and VT (n = 23), which was effective in all cases. Of the 450 episodes of VT, 426 were terminated by an‐titachycardia pacing. Fourteen patients (9%) had inappropriate ICD therapy mainly due to atrial fibrillation or sinus tachycardia, which could be reliably diagnosed by the ICD stored intracardiac electrograms.
Radiofrequency Catheter Ablation of Atrioventricular Nodal Reentry Tachycardia Utilizing Nonfluoroscopic Electroanatomical Mapping
Authors: COOKE PHILIP A. , WILBER DAVID J.
Published: July 2006

The advent of catheter ablation stimulated extensive research into anatomical localization of the pathways involved in atrioventricular nodal reentrant tachycardia(AVNRT). Conventional electrophysiological methods that attempt to correlate intracardiac electrograms with two‐dimensional fluoroscopic anatomy are limited by the relative inaccuracy and poor reproducibility of this technique, and the requirement for high levels of radiation exposure. A new method of nonfluoroscopic electroanatomical mapping utilizes magnetic field sensing with a specialized catheter to construct three‐dimensional electroanatomical endocardial maps of selected heart chambers with spatial resolution of < 1 mm. This system can be used in patients undergoing catheter ablation for AVNRT to create accurate maps of Koch's triangle and to guide application of radiofrequency energy. Initial experience in 14 patients suggests efficacy and safety comparable to conventional mapping and ablation techniques. Further evaluation may confirm the potential benefits of this system with respect to success rates, complications, procedure time, and radiation exposure.
Electroanatomical Mapping and Ablation of the Substrate Supporting Intraatrial Reentrant Tachycardia after Palliation for Complex Congenital Heart Disease
Authors: DOROSTKAR PARVIN C. , CHENG JIE , SCHEINMAN MELVIN M.
Published: July 2006

In patients with congenital heart disease who have undergone palliative surgical interventions postoperative arrhythmias frequently complicate tbe clinical course. Intraatrial reentrant tachycardias(LAHTs) are one of the most common forms of postoperative arrhythmias in these patients and can lead to significant morbidity and even mortality. Drug therapy and/or antitachycardia pacing have been disappointing. Ablative therapy with radiofrequency energy offers a potential for cure for these patients but the conventional approach using multielectrode recordings and fluoroscopic guidance is technically difficult and provides limited success. Recent development of a novel nonfluoroscopic technology with electroanatomical mapping using the CARTO mapping/ablation system has shown promising results in defining the arrhythmia circuit, facilitating diagnosis, and guiding ablative therapy. Rased on our preliminary experience, a systematic approach to postoperative IART using electroanatomical mapping is described. Further studies are needed to fully evahiate the impact of this new technology on the management and therapy of IART.
Idiopathic Left Ventricular Tachycardia with Block Between Purkinje Potential and Ventricular Myocardium
Authors: TOMOKUNI AKIRA , TGAWA OSAMU , YAMANOUCHI YUMI , ADACHI MASAMITSU , SUGA TOSHIMITSU , YANO AKIO , MIAKE JUNICHIRO , INOUE YOSHIAKI , FUJITA SHINYA , HISATOME ICHIRO , SHIGEMASA CHIAKI
Published: July 2006

We performed radiofrequency current catheter ablation in a patient with idiopathic LV. While mapping the inferoapical LV septum during tachycardia, spontaneous termination of tachycardia was observed with block between Purkinje (P) potential and ventricular electrogram (P‐V block). The cycle length of the tachycardia was associated with prolongation of P‐P interval and P‐V interval. P potential recording at this site was earliest and at very low amplitude during tachycardia. The radiofrequency current at this site was successful. These findings indicated that Purkinje fiber was a critical part of the tachycardia circuit. Ablation was successful at a site where both an earliest and low amplitude P potential was recorded during tachycardia, and where P‐V block that was induced by catheter manipulation was observed during tachycardia.
Electrogram Signals Recorded from Acute and Chronic Pacemaker Implantation Sites in Pacemaker Patients
Authors: THERES HEINZ , COMBS WILLIAM , FOTUHI PARWIS , CONDIE CATHY , BONDKE HANS JÜRGEN , STANGL KARL , BAUMANN CERT
Published: July 2006

Electrogram signals recorded from typical pacemaker implantation sites may be useful for a variety of pacemaker system functions including pacemaker follow‐up, atrial and ventricular sensing (event detection), and triggered electrogram storage. We quantified the electrical characteristics of pacemaker pocket electrograms using a subcutaneous electrode array (SEA) in a population of 48 patients undergoing initial or replacement pacemaker implantation. SEA recorded intrinsic R wave amplitudes measured peak to peak averaged 118 μV and 65 μV for the two recorded SEA electrograms and were significantly different (P < 0.001); paced R wave amplitudes averaged 180 μV and 110 μV. P wave amplitudes averaged 39 μV and 26 μV. No statistically significant difference in amplitudes were observed between acute versus chronic pacemaker pocket or indication for pacing (A V block, sick sinus syndrome). Signal to noise ratios, using R wave amplitude as signal, were lower in the SEA electrogram on average (11 dB) compared to the intracardiac electrogram (27 dB), but sufficient for diagnostic assessment. R wave/P wave ratios for SEA signals were lower than surface and intracardiac values 3.1 and 2.7 compared to a range of 6.2–9.8, indicating a relative enhancement of P waves to R waves in SEA signals. In summary, SEA electrograms are of sufficient amplitude and signal quality (signal to noise ratio) to hold promise for future implantable device features such as electrogram telemetry, enhanced sensing, and diagnostic data storage.
Further Observations of “Linking” of Atrial Excitation During Clinical Atrial Fibrillation
Authors: SCHOENWALD ADAM T. , SAHAKIAN ALAN V. , SIH HARIS J. , SWIRYN STEVEN
Published: July 2006

The objective of this article was to look for evidence of nonrandom behavior during atrial fibrillation hy examining long (> 15 minutes) recordings. We have previously reported transient “linking“ of atrial activation during atrial fibrillation, and showed that activation was not entirely randotn. Over the few episodes of linking seen during 1 minute, activation directions apparently repeated, indicating a possible anatomical or physiological constraint. In the present study, we examined atrial fibrillation over longer time periods to see if this constancy of direction was stable. Endocardial recordings were made from 12 patients with atrial fibrillation using a catheter with three orthogonal bipoies, aHowing measurements of local activation directions in three dimensions. The direction was calculated using Pipberger's half‐area method, and episodes of transient linking were identified. An average direction for each episode of linking was calculated and plotted in two dimensions using spherical coordinates (altitude and azimuth). In addition, the nature of initiation and termination of linking was examined. Of the twelve patients, 611 episodes of linking (range 1 to 169 per patient, mean 51) were identified. The episodes for most patients clustered closely in direction. In contrast, directions measured for all activations (i.e., linked and not linked) filled up the entire available range. Linking in most cases subjectively appeared to initiate and terminate suddenly. The results indicate that the local anatomy, pathology, or physiology of the atrium has a strong constraining effect on the electrical activations occurring during atrial fibrillation, and revises our perception of activation during atrial fibrillation as “random.“ The demonstration that local properties greatly influence conduction during fibrillation has important implications for ablation or pacing therapy.
Abnormalities of Electrocardiographic P Wave Morphology and Their Relation to Electrophysiological Parameters of the Atrium in Patients with Sick Sinus Syndrome
Authors: LIU ZHIGANG , HAYANO MOTONOBU , HIRATA TETSUYA , TSUKAHARA KIMIO , QUIN YUEWU , NAKAO KOUJIRO , NONAKA MASAHARU , ISHIMATSU TAKASHI , UEYAMA CHIAKI , YANO KATSUSUKE
Published: July 2006

We examined the incidence, of long P wave duration in lead II and increased P terminal force in lead V1(PTFV1), and their relationship to electrophysiological findings of atrial muscle in 34 patients with sick sinus syndrome (SSS). Patients were divided into three groups: Group I, consisting of 20 patients with various cardiac arrhythmias other than SSS and paroxysmal atrial fibrillation (PAF) who served as controls; Group II, consisting of 18 patients with SSS but without PAF; and Group III consisted of 16 patients with SSS and PAF. P wave duration was significantly longer in Group III (122 ± 11ms, mean ± SD, P < 0.0001) and Group II (111 ± 15 ms, P < 0.002) than in Group I (98 ± 10 ms). PTFV1 was greater in Group III (0.052 ± 0.025 ms) than in Group I (0.028 ± 0.011 ms, P < 0.05). P wave duration and PTFV1 had significantly and/or borderline correlations with longest duration of right atrial electrograms (r = 0.84, P < 0.0001 and 0.47, P < 0.02, respectively), maximal number of fragmented deflections of atrial electrograms (r = 0.69, P < 0.0001 and r = 0.51, P < 0.02, respectively), repetitive atrial firing zone (RAFZ) (r = 0.81, P < 0.0001 and 0.48, P < 0.05, respectively) and fragmented atrial activity zone (FAAZ)(r ‐ 0.53, P < 0.01 and r = 0.45, P = 0.06, respectively). We concluded that long P wave duration and increased PTFV1 are electrocardiographic indicators for coexistence of electrophysiological abnormalities in the atria in SSS without recognizable heart disease.
When Pacemakers Fail: An Analysis of Clinical Presentation and Risk in 120 Patients with Failed Devices
Authors: NANTHAKUMAR KUMARASWAMY , DORIAN PAUL , HAM MINEY , LAM PATRICK , LAU CHING , NISHIMURA SANDRA , NEWMAN DAVID
Published: July 2006

Although pacemaker recalls are common, the optimal mechanism for risk assessment and triage of patients at risk for sudden loss of device system function is unknown. A retrospective chart review of 120 patients with factory proven failed devices was performed. Logistic regression analysis was used to determine clinical correlates of emergency room versus outpatient clinic presentation at time of device failure. Twenty‐two patients (18%) presented to emergency and 98 (82%) to clinic. Sixty‐three devices had no device output at the time of presentation. Multivariate logistic regression analysis revealed that antiarrhythmic drug use (odds ratio: 7.4, 95% CI: 2.0–28.0), atrioventricular nodal disease as an indication for pacing (odds ratio: 2.8, 95% CI: 1.2–3.0), and female gender (odds ratio: 2.2, 95% CI: 1.0–4.5) were the only significant correlates of emergency room presentations. Pacemaker dependency (escape heart rate < 40 beats/min) did not correlate with location of presentation even though no device output at the time of presentation was associated with emergency room presentation (odds ratio: 2.5, 95% CI: 1.1–5.8). Neither the presence of structural heart disease nor symptoms at the time of device implantation (syncope or presyncope) were correlated with location of presentation upon unexpected device failure. Although there were no deaths in the 120 failed devices studied, there were 26 deaths in the total group of 227 patients with recalled devices that could not be studied. Antiarrhythmic drug use, electrocardiographic pacing indication, and female gender may be more sensitive predictors of emergency room presentation and significant symptoms in the event of unanticipated pacemaker failure. The inability of any retrospective analysis to accurately assess mortality in the setting of pacemaker system failure underscores the need for prospective databases in recall situations.