bluuebunny/crossref_metadata_2025_split huggingface dataset:
Unipolar Electrogram Characteristics Predictive of Successful Radiofrequency Catheter Ablation of Accessory Pathways
Authors: BARLOW MALCOLM A. , KLEIN GEORGE J. , SIMPSON CHRISTOPHER S. , MURGATROYD FRANCIS D. , YEE RAYMOND , KRAHN ANDREW D. , SKANES ALLAN C. 
Published: April 2007

Unipolar Electrogram in Ablation. Introduction: The purpose of this study was to determine the characteristics of the unipolar electrogram that are most helpful in predicting successful radiofrequency ablation of accessory pathways. Methods and Results: The unipolar electrogram was analyzed at 185 ablation sites in 53 patients; 94 attempts were directed at the site of earliest atrial activation (“atrial gronp”) and 91 at the site of earliest ventricular activation (“ventricular group”). The electrogram was analyzed for several features, including pattern (“QS” or “initial R”). Unipolar pattern: Overall, a “QS” pattern was seen at 55% of unsuccessful, 75% of temporarily successful, and 90% of permanently successful sites. For the atrial group, the respective frequencies were 53%, 77%, and 92%, and for the ventricular group, 57%, 73%, and 86%. The difference in pattern distribution between unsuccessful and permanently successful sites was significant for all groups: overall, P < 0.0001; atrial group, P = 0.0005; ventricular group, P = 0.02. Absence of a “QS” pattern (i.e., “initial R”) predicted a 92% chance of unsuccessful ablation. Additional features: Activation times were significantly shorter at permanently successful than at unsuccessful (P < 0.0001) or temporarily successful sites (P = 0.0002). No significant differences were found in atrial or ventricular amplitudes or in A/V ratios. Intrinsic deflection slew was lower at temporarily successful sites (P = 0.03 vs all other sites). Conclusion: Ablation at sites revealing an “initial R” pattern (i.e., absent “QS”) is very unlikely to be successful. Activation time is shorter at successful sites. These features are equally applicable when mapping the atrial potential as when mapping the ventricular potential.
Comparison of Endocardial Activation Times at Effective and Ineffective Ablation Sites Within the Pulmonary Veins
Authors: TSE HUNG‐FAT , LAU CHU‐PAK , KOU WILLIAM , PFLOSI FRANK , ORAL HAKAN , KIM MICHAEL , MICHAUD GREGORY F. , KNIGHT BRADLEY P. , MOSCUCCI MAURO , STRICKBERGER S. ADAM , MORADY FRED 
Published: April 2007

Pulmonary Vein Arrhythmias. Introduction: Recent studies demonstrated that atrial arrhythmias may be generated within pulmonary veins. The purpose of this study was to compare the endocardial activation times at effective and ineffective ablation sites during radiofrequency catheter ablation of arrhythmias initiated or generated within pulmonary veins. Methods and Results: Twenty‐one of 28 patients without structural heart disease underwent successful ablation of 23 arrhythmogenic foci within a pulmonary vein. Electrograms were recorded at 75 pulmonary venous sites and categorized into three groups: 23 successful ablation sites; 28 unsuccessful target sites within an arrhythmogenic pulmonary vein; and 24 sites within nonarrhythmogenic pulmonary veins. The endocardial activation time of premature depolarizations arising at successful target sites was significantly earlier than at other sites. During premature depolarizations, an endocardial activation time of ‐75 msec or earlier had a sensitivity of 83% and a specificity of 79% for identification of a successful ablation site. Endocardial activation times earlier than ‐100 msec were recorded only at successful ablation sites, and endocardial activation times later than ‐30 msec were recorded only at sites within nonarrhythmogenic pulmonary veins. The presence of a split potential during sinus rhythm or premature depolarizations was not a specific indicator of a successful ablation site. Conclusion: The endocardial activation times of premature depolarizations that arise within pulmonary veins and initiate atrial tachycardia/fibrillation are useful in identifying successful ablation sites.
Prevalence and significance of Exit Block During Arrhythmias Arising in Pulmonary Veins
Authors: TSE HUNG‐FAT , LAU CHU‐PAK , KOU WILLIAM , PELOSI FRANK , ORAL HAKAN , KIM MICHAEL , F GREGORY , P BRADLEY , MOSCUCCI MAURO , STRICKBERGER S. ADAM , MORADY FRED 
Published: April 2007

Exit Block. Introduction: Recent studies described the occurrence of conduction block within pulmonary veins. The purpose of this study was to evaluate the prevalence of exit block during arrhythmias that arise in pulmonary veins. Methods and Results: Twenty‐five patients with atrial tachycardia/fibrillation underwent successful ablation of 28 arrhythmogenic foci within a pulmonary vein. The prevalence of exit block in the pulmonary veins was determined in 28 arrhythmogenic pulmonary veins and 40 nonarrhythmogenic pulmonary veins. During isolated premature depolarizations, exit block in a pulmonary vein was observed at 50% of arrhythmogenic pulmonary vein sites and was never observed within pulmonary veins that did not generate a tachycardia (P < 0.01). During tachycardia, exit block from a pulmonary vein was observed in 61% of the arrhythmogenic pulmonary veins. The mean cycle length of the pulmonary vein tachycardias associated with exit block was significantly shorter than the cycle length of tachycardia that were not associated with exit block (163 ± 32 vs 251 ± 45 msec, P < 0.001), Exit block in two pulmonary veins during the same episode of tachycardia was observed in 3 of the 28 arrhythmogenic pulmonary veins (11%) in three different patients. Simultaneous recordings in the two pulmonary veins demonstrated bursts of tachycardia in both veins that were not synchronized. Radiofrequency catheter ablation of the arrhythmogenic site in one of the pulmonary veins eliminated spontaneous recurrences of tachycardia from the other pulmonary vein. Conclusion: Exit block from pulmonary veins is a common observation during tachycardias generated within pulmonary veins and indicates that an arrhythmogenic pulmonary vein has been identified. The occurrence of exit block in more than one pulmonary vein most likely is attributable to simultaneous tachycardias, one or both of which may be tachycardia induced and perpetuated by the other.
Junctional Rhythm During Slow Pathway Radiofrequency Ablation in Patients with Atrioventricular Nodal Reentrant tachycardia: Beat‐to‐Beat Analysis and Its Prognostic Value in Relation to Electrophysiologic and Anatomic Parameters
Authors: PORET PHILIPPE , LECLERCQ CHRISTOPHE , GRAS DANIEL , MASOUR HASSAN , FAUCHIER LAURENT , DAUBERT CLAUDE , MABO PHILIPPE 
Published: April 2007

Junctional Rhythm and Slow Pathway Ablation. Introduction: Junctional rhythm usually is considered a sensitive hut nonspecific marker of successful ablation of the slow pathway in AV nodal reentrant tachycardia. Nevertheless, this junctional rhythm has been little studied, and its relations to recognized predictors of successful radiofrequency (RF) application were never established in any study. Methods and Results: Thirty‐nine patients underwent RF ablation of the slow pathway for AV nodal reentrant tachycardia. Ninety RF applications were delivered, and each ablation site was determined using three different fluoroscopic projections. Six anatomic zones were defined from low posterior septum to the site of distal His‐bundle recording (P1, P2, Ml, M2, Al, and A2). Characteristics of junctional rhythm during RF applications were analyzed. Atrial electrogram characteristics at the ablation sites also were studied. All patients had successful slow pathway ablation, without any complication. The ablation sites were located as follows: 41 at PI. 26 at P2, 20 at Ml, and 3 in M2. Forty RF applications were successful: 14 of 41 attempts at P1, 7 of 26 at P2, 16 of 20 at M1, and 3 of 3 at M2. Mid‐septal ablation site (Ml and M2) was associated with higher occurrence of junctional rhythm (P < 0.0001), earlier first junctional heat (P = 0.008), and earlier occurrence of the longest junctional burst (P = 0.03) compared with posterior ablation site (P1 and P2). The combination of a mid‐septal ablation site and a first junctional heat occurring ≤3 seconds after onset of RF application identified successful RF application with 100% accuracy. Using multivariate analysis, the ablation site, duration of atrial electrogram (including slow pathway potential when present), and occurrence of junctional rhythm were independent predictors of success. Conclusion: Successful slow pathway ablation depends on many factors. Junctional rhythm characteristics are related to the site of RF delivery and can be helpful in assessing successful slow pathway ablation.
Late Fields of the Magnetocardiographic QRS Complex as Indicators of Propensity to Sustained Ventricular Tachycardia after Myocardial Infarction
Authors: KORHONEN PETRI , MOINTONEN JUHA , MÄKINÄRVI MARKKU , KATILA TOIVO , NIEMINEN MARKKU S. , TOIVONEN LAURI 
Published: April 2007

MCG Late Fields and Propensity to VT. Introduction: Magnetocardiographic (MCG) mapping is a new method to record cardiac signals. This study examined the association of MCG late fields with the propensity to sustained ventricular tachycardia (VT) after myocardial infarction (MI). Methods and Results: One hundred patients with remote Ml were studied, 38 with and 62 without history of VT. High‐resolution MCG and signal‐averaged ECG (SAECG) as a comparative method were recorded. Time‐domain parameters describing the abnormal low‐amplitude end QRS activity, MCG late fields, and SAECG late potentials were analyzed. Late field parameters differed significantly between the patient groups: filtered QRS duration was 137 ± 26 msec in the VT group and no ± 18 msec in the control group (P < 0.001), and root mean square amplitude of the last 40 msec was 260 ± 170 and 510 ± 360 IT (P < 0.001), respectively. The optimal MCG parameter combination yielded a sensitivity of 92% and a specificity of 61% in classification to the VT group, whereas those for SAECG were 63% and 66%. In a subgroup of 63 patients with marked left ventricular dysfunction and comparable stage of coronary heart disease, only MCG (sensitivity 73%, specificity 67%) but not SAECG could assign a patient to the VT group. Conclusion: Late fields of the MCG QRS complex indicate propensity to life‐threatening arrhythmias in post‐MI patients. This discriminative ability persists in the presence of severe left ventricular dysfunction where KCG late potentials lose their informative value. MCG late field analysis is a potential new method for noninvasive risk assessment in post‐MI patients.
Inhibition of Na,K‐ATPase by External Electrical Cardioversion in a Sheep Model of Atrial Fibrillation
Authors: MAIXENT JEAN‐MICHEL , BARBEY ODILE , PIERRE SANDRINE , DURAN MARIE‐JOSÉE , SENNOUNE SOUAD , BOURDEAUX MADELEINE , RICARD PHILIPPE , LÉVY SAMUEL 
Published: April 2007

Na,K‐ATPase and Cardioversion. Introduction: Electrical external cardioversion commonly used to treat atrial fibrillation (AF) is associated with myocardial membrane damage and disturbances in ionic homeostasis (hemodynamically unstable). The present study was designed to investigate whether alterations in ionic homeostasis observed were due in part to changes in the myocardial activity of Na,K‐ATPase. Methods and Results: AF was induced by pacing in ten anesthetized sheep divided into two groups. Group I (n = 4) received a single external countershock of 360 J after three episodes of AF lasting 10 minutes. Group II (n = 6) served as controls. Activity, responsiveness to ouabain, and membrane expression of catalytic α and β subunits of Na,K‐ATPase in sarcolemmal myocardial membrane fractions were investigated. Membrane fluidity and fatty acid composition, and plasma levels of atrial natriuretic factor (ANF) also were measured. One shock after episodes of AF significantly decreased ventricular Na,K‐ATPase activity up to 50% IP < 0.001) without modification of atrial activity at the membrane level. Sites with low affinity to ouabain showed a fivefold lower affinity for ouabain in the cardioversion group than in the control group (IC50= 7.9 μmol/L vs 40 μmol/L ouabain, P < 0.05). Plasma levels of ANF were significantly increased in the cardioversion group compared with the control group. These changes were independent of membrane modulation in terms of expression of Na,K‐ATPase, membrane fluidity, and fatty acid composition. Conclusion: This study suggests that left ventricular perturbation of ionic homeostasis subsequent to transthoracic cardioversion could result from inactivation of Na,K‐ATPase activity.
Block of IKs Does Not Induce Early Afterdepolarization Activity but Promotes β‐Adrenergic Agonist‐Induced Delayed Afterdepolarization Activity
Authors: BURASHNTKOV ALEXANDER , ANTZELEVITCH CHARLES 
Published: April 2007

Block of IK Does Not Induce EADs.
Introduction: An early afterdepolarization (EAD)‐induced triggered heat is thought to precipitate torsade de pointes (TdP) in the long QT syndrome (LQTS). Previous studies demonstrated the development of EAD activity and dispersion of repolarization under LQT2 (reduced IKr) and LQT3 (augmented late INa). but not LQTl (reduced IKs), conditions. The present study examines these electrophysiologic characteristics during IKs block. Methods and Results: Canine epicardial (Epi), M, and endocardial (Endo) tissues and Purkinje fibers isolated from the canine left ventricle were studied using standard microelectrode recording techniques. The IKs blocker chromanol 293B (293B, 30 μM), produced a homogeneous rate‐independent prolongation of action potential duration (APD) in Epi, M, and Endo, but little to no APD prolongation in Purkinje. Chromanol 293B I to 30 μM failed to induce EADs or delayed afterdepolarizations (DADs) in any of the four tissue types. Isoproterenol (ISO, 0.1 to 1.0 μM) in the presence of 293B 30 μM significantly prolonged the APD of the M cell (basic cycle length ≥ sec), abbreviated that of Purkinje, and caused little change in that of Epi and Endo. The combination of 293B 30 μM and ISO 0.2 μM did not induce EADs in any of the four tissue types, but produced DAD activity in 4 of 8 Epi, 7 of 10 M cells, and 3 of 8 Endo. Conclusion: Our results indicate that IKs block alone or in combination with β‐adrenergic stimulation does not induce EADs in any of the four canine ventricular tissue types, but that the combination of the two induces DADs as well as accentuated dispersion of repolarization.
Catheter Ablation for Hemodynamically Unstable Monomorphic Ventricular Tachycardia
Authors: ELLISON KRISTIN E. , STEVENSON WILLIAM G. , SWEENEY MICHAEL O. , LEEROY DAVID C. , DELACRETAZ ETIENNE , FRIEDMAN PETER L. 
Published: April 2007

Ablation of Unstable Ventricular Tachycardia. Introduction: Hemodynamic collapse precludes extensive catheter mapping to identify focal target regions in many patients with ventricular tachycardia (VT) associated with heart disease. This study tested the feasibility of catheter ablation of poorly tolerated VTs by targeting a region identified during sinus rhythm. Methods and Results: Ablation was attempted in five patients, ages 44 to 59 years, with left ventricular ejection fractions of 0.15 to 0.20 and poorly tolerated VT causing multiple implantable defibrillator therapies (6 to 30 episodes/month). VT was due to prior infarction in three patients and nonischemic cardiomyopathy in two. Target regions were sought that met the following criteria: (1) evidence of slow conduction from fractionated sinus rhythm electrograms and stimulus‐QRS delays during pace mapping, and (2) evidence that the region contains the reentrant circuit exit from pace mapping. In 4 of 5 patients, a target region was identified and radiofrequency lesions applied. Ablation abolished all recurrences of VT in 3 of 4 patients during follow‐up of 14 to 22 months. There were no complications. Conclusion: Ablation of poorly tolerated VT is feasible in some patients by mapping during sinus rhythm and performing ablation over a region of identifiable scar that contains abnormal conduction and a presumptive VT exit.
Ionic Basis for Action Potential Prolongation by Phenylephrine in Canine Epicardial Myocytes
Authors: ROBINSON RICHARD B. , LIU QIN‐YUE , ROSEN MICHAEL R. 
Published: April 2007

Phenylephrine Action on Repolarization. Introduction: In canine ventricle, α‐adrenergic agonists prolong action potential duration (APD) without any effect on the action potential notch, suggesting that, in this species, the effect on repolarization might he independent of inhibition of Ito. The present study investigated the action of the α‐adrenergic agonist phenylephrine on the action potential and the repolarizing currents Ito and IK in isolated canine epicardial myocytes. Methods and Results: Isolated cells from canine epicardial tissue, and Purkinje fibers, were studied with the whole cell, voltage clamp method. Phenylephrine 0.1 μM increased APD by 13%± 4% at 90% repolarization without affecting the notch or amplitude. Under voltage clamp, concentrations of phenylephrine as high as 10 μM had no effect on Itp in canine epicardial myocytes. However, Ito of isolated canine Purkinje myocytes was reduced to 69%± 7% of control by 1 μM phenylephrine. Further studies in canine epicardial myocytes revealed an action of phenylephrine to inhibit Ik, and in particular IKs Using a voltage protocol that included a two‐step repolarization to separate IKs and IKr tail components, the largely 1Ke, component was not significantly affected by 1 μM phenylephrine, whereas the largely IKs component was reduced to 81%± 5% of control value. Conclusion: α‐Adrenergic prolongation of repolarization in canine epicardium does not result from inhibition of Ito. Rather, it appears that reduction of IKs contributes to the action of phenylephrine. The unresponsiveness of epicardial Ito is not a general characteristic of the canine heart, because Purkinje myocyte Ito was inhibited, suggesting regional differences in the molecular basis of lto, and/or a‐adrenergic signaling in the canine heart.
How Constant Anatomically is the Tendon of Todaro as a Marker for the Triangle of Koch?
Authors: YEN HO SIEW , ANDERSON ROBERT H. 
Published: April 2007

Tendon of Todaro. Introduction: Although well recognized by anatomists as a border of the triangle of Koch demarcating the location of the A V node, the tendon of Todaro is not visible in the operating room or in the catheterization laboratory. Instead, clinicians use as surrogate a projected line between the eustachian valve and the central fibrous body. The constancy of the tendon of Todaro within this border remains to be determined. Materials and Results: We reexamined serial histologic sections from 25 adults and 50 infants and gross dissections in four normal hearts. The tendon of Todaro was identified in all cases and traced to the central fibrous body in all but one case. It tended to be thicker in the hearts of infants cases (0.2 to 0.8 mm vs 0.1 to 0.6 mm). The tendon and the binge‐line of the septal leaflet of the tricuspid valve were consistent as landmarks for location of the compact AV node in all the cases studied by histology. Gross dissections traced the tendon to the free edge of the eustachian valve. Conclusion: The tendon of Todaro is present in hearts obtained from both adults and infants. It or its surrogate, is a reliable border for the triangle of Koch and serves as a landmark to location of the atrial components of the AV conduction axis.
Gender‐Related Differences in Modulation of Heart Rate in Patients with Congestive Heart Failure
Authors: ARONSON DORON , BURGER ANDREW J. 
Published: April 2007

Gender and HRV in Heart FailureIntroduction. The prognosis of women with congestive heart failure (CHF) is better than that for men, but the mechanisms underlying the female survival advantage are not well understood. CHF is characterized by profound abnormalities in cardiac autonomic control that contribute to progressive circulatory failure and influence survival.Methods and Results. Time‐ and frequency‐domain heart rate variability (HRV) indexes were obtained from 24‐hour Holter recordings and compared to assess the role of gender in 131 men and 68 women with CHF (mean age 60 ± 13.6 years, range 21 to 87; New York Heart Association Functional Class III [66%] and IV [34%]). Gender‐related differences in HRV were observed only in the subset of patients with nonischemic heart failure (55 men and 39 women). Among the time‐domain indexes, the SD of the RR intervals (76 ± 5.3 msec vs 55.3 ± 3.2 msec, P < 0.0001) and indexes denoting parasympathetic modulation, the percentage of RR intervals with >50 msec variation (4.0%± 1.0% vs 6.5%± 1.3%, P = 0.02), and the square root of mean squared differences of successive RR intervals (19.1 ± 3.3 vs 28.4 ± 3.8, P = 0.004) were higher in women. Among the frequency‐domain indexes, the total power (7.5 ± 0.13 In‐msec2 vs 8.3 ± 0.14 In‐msec2, P = 0.0002), the ultralow‐frequency power (7.2 ± 0.11 In‐msec2 vs 8.0 ± 0.14 In‐msec2, P < 0.0001), the low‐frequency power (3.8 ± 0.25 In‐msec2 vs 4.8 ± 0.28 In‐msec2, P = 0.006), and the high‐frequency power (3.8 ± 0.24 In‐msec2, vs 4.6 ± 0.26 In‐msec2, P = 0.003) were greater in women than in men.Conclusion. Women with nonischemic CHF have an attenuated sympathetic activation and parasympathetic withdrawal compared with men. Gender‐based differences in autonomic responses in the setting of CHF may be related to the female survival advantage. (J Cardiovasc Electrophysiol, Vol. 11, pp. 1071‐1077, October 2000)
Circadian Variation of Vasovagal Syncope
Authors: MINEDA YORIAKI , SUMIYOSHI MASATAKA , TOKANO TAKASHI , YASUDA MASAYUKI , NAKAZATO KAORU , NAKAZATO YUJI , NAKATA YASURO , YAMAGUCHI HIROSHI 
Published: April 2007

Circadian Variation of Vasovagal Syncope. Introduction. Circadian patterns have been demonstrated for several cardiovascular catastrophes. Chronobiologic factors play a role in the emergence of vasovagal syncope (VVS); however, diurnal variation of syncopal episodes in VVS has not been reported previously.Methods and Results. We assessed daily distribution of the time of syncopal episodes in VVS. Time of syncope could be determined in 80 episodes in 54 patients (32 men and 22 women; mean age 37 years, range 12 to 67). Patients who were prescribed beta blockers or vasodilators, and who had syncopes related to alcohol intake, were excluded from the study. Head‐up tilt testing was performed in 53 patients. The distribution of the episodes of VVS in 3‐hour intervals differed significantly from uniform occurrence (P < 0.0001). with a peak frequency between 6 A.M. and noon (67.5% of total episodes). In patients who had experienced the initial syncope in the morning, most (78%) of the next syncopal episodes also occurred in the morning. There was no significant correlation between the time of last syncopes and tilt testing results.Conclusion. We demonstrated a prominent circadian variation in the frequency of VVS, with a peak in the morning. Recognition of the daily distribution of VVS is useful for patient education and therapeutic strategy. (J Cardiovasc Eleciroptiysiol. Vol. 11. pp. 1078‐1080, October 2000)