bluuebunny/crossref_metadata_2025_split huggingface dataset:
Repolarization Abnormalities Detected by Magnetocardiography in Patients with Dilated Cardiomyopathy and Ventricular Arrhythmias
Authors: KORHONEN PETRI , VÄÄNÄNEN HEIKKI , MÄKIJÄRVI MARKKU , KATILA TOIVO , TOIVONEN LAURI 
Published: August 2003

Repolarization Abnormalities by Magnetocardiography.
Introduction: Abnormal repolarization is one of the acknowledged mechanisms leading to malignant ventricular arrhythmias. We used a novel magnetocardiographic technique to investigate the role of inhomogeneous repolarization in patients with nonischemic dilated cardiomyopathy prone to sustained ventricular arrhythmias. Methods and Results: Forty‐nine dilated cardiomyopathy patients were studied, 18 with a history of sustained ventricular tachycardia (n = 6) or ventricular fibrillation (n = 12) and 31 with no ventricular arrhythmias. The magnetocardiogram was registered and QT apex and QT end intervals were determined by a computer algorithm. Inhomogeneity of repolarization was characterized with indices describing QT apex and QT end dispersion, and T wave end duration. In addition, time‐domain late fields of the QRS complex in magnetocardiography and QT dispersion in 12‐lead ECG were determined. T wave end was longer in the arrhythmia group in patients with sinus rhythm (87 ± 15 msec vs 73 ± 12 msec; P = 0.005) and in those not having bundle branch block. Magnetocardiographic late fields of the QRS complex were not different between groups. QT apex and end dispersion on magnetocardiography or 12‐lead ECG showed no difference. Conclusion: Prolongation of the end part of the T wave revealed by magnetocardiography is related to malignant ventricular arrhythmias in dilated cardiomyopathy. The results suggest that abnormal repolarization rather than delayed conduction underlies the arrhythmias in this disease.
Electrocardiographic Analysis of Ectopic Atrial Activity Obscured by Ventricular Repolarization: P Wave Isolation Using an Automatic 62‐Lead QRST Subtraction Algorithm
Authors: SIPPENSGROENEWEGEN ARNE , MLYNASH MICHAEL D. , ROITHINGER FRANZ X. , GOSEKI YOSHINARI , LESH MICHAEL D. 
Published: August 2003

62‐Lead QRST Subtraction Algorithm.
Introduction: Atrial activity on the surface ECG during premature beats and supraventricular arrhythmias frequently is obscured by the superimposed QRST complex of the previous cardiac cycle. This study examines the performance of a newly developed automatic QRST subtraction algorithm to isolate ectopic P waves from the preceding T‐U wave. Methods and Results: The 62‐lead ECG recordings were obtained during (1) sinus rhythm and programmed right atrial stimulation in 12 patients (group A); and (2) sinus rhythm and atrial premature beats, atrial tachycardia, or paroxysmal atrial fibrillation in 5 patients (group B). Pacing in group A patients was conducted at a slow drive cycle length to generate an ectopic P wave not obscured by the previous QRST complex and by delivering single premature extrastimuli at progressively shorter coupling intervals to produce an ectopic P wave obscured by the upsloping (early T‐U wave), peak (middle T‐U wave), and downsloping component of the T‐U wave (late T‐U wave). All ectopic P waves in group B patients were concealed by the preceding T‐U wave. Automatic QRST subtraction was attained using an adaptive template constructed from averaged QRST complexes (mean 83 ± 25 complexes) obtained during sinus rhythm (groups A and B) or atrial overdrive pacing (group A). P wave integral maps subsequently were computed, visually compared, and mathematically correlated. A high correspondence in spatial map pattern was observed between integral maps of “nonobscured” and previously “obscured” paced P waves obtained in group A patients (mean r = 0.88 ± 0.07) as well as between integral maps of two to three previously obscured P waves with the same atrial arrhythmia morphology obtained in group B patients (mean r = 0.94 ± 0.05). Improved morphologic P wave replication in group A patients was acquired when concealment occurred in the early (mean r = 0.90 ± 0.08) or late part of the T‐U wave (mean r = 0.90 ± 0.06) as opposed to the middle T‐U wave (mean r = 0.85 ± 0.07) (P = NS and P < 0.05 for early vs middle and late vs middle T‐U wave, respectively). Conclusion: This novel automatic 62‐lead QRST subtraction algorithm enables discrete isolation of T‐U wave obscured ectopic atrial activity on the surface ECG while retaining the intricate spatial detail in P wave morphology. Future clinical application of the algorithm may enable improved ECG localization of focal triggers of paroxysmal atrial fibrillation, atrial tachycardia, and the atrial insertion of accessory pathways.
Different Mechanisms of Isoproterenol‐Induced and Nitroglycerin‐Induced Syncope During Head‐Up Tilt in Patients with Unexplained Syncope: Important Role of Epinephrine in Nitroglycerin‐Induced Syncope
Authors: TAKASE BONPEI , UEHATA AKIMI , NISHIOKA TOSHIHIKO , ISOJIMA KAZUSIJE , SATOMURA KIMIO , OHSUZU FUMITAKA , KURITA AKIRA 
Published: August 2003

Isoproterenol‐Induced vs Nitroglycerin‐Induced Syncope.
Introduction: A reduction in left ventricular volume and an increase in epinephrine levels have been reported in tilt‐induced neurally mediated syncope. To compare the mechanisms of isoproterenol‐induced and nitroglycerin‐induced syncope during head‐up tilt and to investigate the role of catecholamines, the temporal changes in plasma levels of norepinephrine and epinephrine and in left ventricular volume were measured. Methods and Results: The first study population consisted of 90 patients with syncope of unknown etiology and 12 control subjects. The second study population consisted of 43 patients with unexplained syncope. In the first study, head‐up tilt (80° angle) was conducted for 40 minutes, and norepinephrine and epinephrine levels were measured. In the second study, all patients were randomly allocated to either isoproterenol test (20 patients) or nitroglycerin test (23 patients) for 20‐minute head‐up tilt. Isoproterenol infusion was given at a rate of 1 to 3 μ g/min. Intravenous infusion of nitroglycerin was started at 250 μ g/hour with increasing dosages up to 1,500 μ g/hour. Norepinephrine and epinephrine were measured in peripheral venous blood. Left ventricular volumes were measured by echocardiography with patients in the supine position and during head‐up tilt every 1 minute. End‐diastolic volume and end‐systolic volume were calculated. In the first study, 61 patients demonstrated a positive response and 29 patients demonstrated a negative response. Plasma norepinephrine changes during head‐up tilt were not significantly different, whereas epinephrine levels were significantly higher in the positive patients than in the negative and control subjects (148 ± 118 pg/mL vs 66 ± 31 pg/mL and 55 ± 27 pg/mL). Thirteen of the 20 patients given isoproterenol and 15 of the 23 patients given nitroglycerin showed a positive head‐up tilt (65.0% vs 65.2%; P = NS). During isoproterenol and nitroglycerin infusion head‐up tilt, epinephrine in the positive group determined by the nitroglycerin test was significantly higher than that in the other three groups (103 ± 38 pg/mL vs 60 ± 33 pg/mL, 31 ± 21 pg/mL, and 50 ± 52 pg/mL). In contrast, end‐systolic volume was significantly smaller in the positive group than in the other three groups based on findings of the isoproterenol test. Conclusion: The findings suggest that nitroglycerin triggers head‐up tilt‐induced syncope by increasing epinephrine levels, whereas isoproterenol induces syncope by decreasing left ventricular volume.
Sinus Pacemaker Function after Cardioversion of Chronic Atrial Fibrillation: Is Sinus Node Remodeling Related with Recurrence?
Authors: MANIOS EMMANUEL G. , KANOUPAKIS EMMANUEL M. , MAVRAKIS HERCULES E. , KALLERGIS ELEFTHERIOS M. , DERMITZAKI DESPINA N. , VARDAS PANOS E. 
Published: August 2003

Sinus Node Remodeling and Atrial Fibrillation.
Introduction: The objective of this study was to investigate the temporal changes in sinus node function in postcardioversion chronic atrial fibrillation (AF) patients and their possible relation with the recurrence rates of AF. Methods and Results: In 37 chronic AF patients, internally cardioverted to sinus rhythm, corrected sinus node recovery time (CSNRT), and the pattern of corrected return cycle lengths were assessed 5 to 20 minutes and 24 hours after conversion. The last 20 consecutive patients also were evaluated after autonomic blockade. Twenty subjects with normal atrial structure and no history of AF served as the control group. Patients were followed‐up for 1 month for recurrence, and the density of supraventricular ectopic beats per hour was obtained during the first 24 hours after conversion. Fifteen patients (40.5%) relapsed during follow‐up. CSNRT values at 600 msec (371 ± 182 msec) and 500 ms (445 ± 338 msec) were significantly higher than those of control subjects (278 ± 157 msec, P = 0.050, and 279 ± 130 msec, P = 0.037, respectively). Significant temporal changes in CSNRT also were observed during the first 24 hours after conversion (600 msec: 308 ± 120 msec, P = 0.034; 500 msec: 340 ± 208 msec, P = 0.017). No significant interaction and temporal effects were observed with regard to corrected return cycle length pattern. Similar data regarding CSNRT and corrected return cycle length pattern were obtained after autonomic blockade. Patients with abnormal CSNRT after cardioversion had higher recurrence rates (50%) than those with normal function (37%; P = NS). Patients who relapsed had a higher density of supraventricular ectopic beats per hour (159 ± 120) compared with those who did not (35 ± 37; P = 0.001). Conclusion: Depressed sinus node function is observed after conversion of chronic AF. Recovery from this abnormality and its independence from autonomic function suggest that AF remodels the sinus node. Our data do not support a causative role of sinus node function in AF recurrence, but they do indicate such a role for the density of atrial ectopic beats.
Pulmonary Vein Dilation in Patients with Atrial Fibrillation: Detection by Magnetic Resonance Imaging
Authors: TSAO HSUAN‐MING , YU WEN‐CHUNG , CHENG HUI‐CHENG , WU MEI‐HAN , TAI CHING‐TAI , LIN WEI‐SHIANG , DING YU‐AN , CHANG MAU‐SONG , CHEN SHIH‐ANN 
Published: August 2003

Pulmonary Vein Dilation in AF.
Introduction: The positive relationship between left atrial (LA) size and atrial fibrillation (AF) is well recognized; however, there is little information on the association of pulmonary vein (PV) diameter and AF. The purpose of this study was to investigate by magnetic resonance angiography the change of PV and LA size in patients with no history of AF, patients with paroxysmal AF (PAF), and patients with chronic AF (CAF). Methods and Results: The study included 47 patients. Group I included 15 patients with normal sinus rhythm and no history of documented AF. Group II included 24 patients with drug‐refractory PAF who underwent electrophysiologic study and radiofrequency ablation of PV foci. Group III included 8 patients with CAF who were converted to sinus rhythm by external electrical cardioversion. Age and concomitant heart diseases were similar among the three groups. We measured the diameter of each PV at its junction with the LA in addition to LA dimensions by gadolinium‐enhanced magnetic resonance angiography with three‐dimensional reconstruction. Significant dilation of both superior PVs (P < 0.01) and transverse diameter of LA (P < 0.01) was seen in the three groups. There were no significant changes of both inferior PVs, corrected PV (PV/LA) diameter, or longitudinal diameter of LA among the three groups. Only 28% patients showed arrhythmogenic foci from the largest PV. Conclusion: Significant dilation of both superior PVs with simultaneous LA enlargement was demonstrated in PAF and CAF patients. Although PV size cannot predict AF firing, the anatomic and geometric differences may participate in perpetuation of AF.
Echocardiographic Lesion Characteristics Associated with Successful Ablation of Inappropriate Sinus Tachycardia
Authors: REN JIAN‐FANG , MARCHLINSKI FRANCIS E. , CALLANS DAVID J. , ZADO ERICA S. 
Published: August 2003

Ablation for Inappropriate Sinus Tachycardia.
Introduction: Catheter ablation of inappropriate sinus tachycardia has proven difficult. Despite the use of intracardiac echocardiography to help direct radiofrequency (RF) application to the anatomic target of the superolateral crista terminalis (CT), multiple RF lesions often are required. Furthermore, the characteristic echo‐anatomic changes with RF application associated with a reduction in heart rate have not been defined. A characteristic echo signature, if present, may facilitate the ablation process. The purpose of this retrospective study was to define the echocardiographic characteristic changes associated with effective RF ablation for inappropriate sinus tachycardia. Methods and Results: Detailed intracardiac echocardiographic imaging characterization of the superolateral CT was performed before and at the time of successful heart rate reduction. Using on‐line videotape intracardiac echocardiography (9 MHz, 9 French), changes in wall thickness and echodensity at the CT lesion site were assessed at baseline, after each RF lesion, and with the lesion that produced heart rate reduction in 17 patients (age 32 ± 9 years; 15 women) with inappropriate sinus tachycardia. In all patients, RF ablation was anatomically based and targeted only the superolateral CT. RF lesions were created using 20 to 50 W for up to 2 minutes using an 8‐mm tip electrode. Successful heart rate reduction (≥ 20 beats/min) was achieved in 15 of 17 patients and required 41 ± 31 RF applications (range 5 to 110, median 40). Effective RF (reduced heart rate) was observed starting with the 34th ± 24th lesion (range 3rd to 86th, median 25th). After effective RF, CT wall thickness was increased (11.4 ± 3.1 mm vs 7.7 ± 2.4 mm at baseline) and wall swelling expanded to adjacent superior vena cava, but the degree of thickening was not specific for effective RF associated with heart rate reduction. Importantly, we noted echodensity changes reaching directly to the epicardium with the development of a linear low echodensity or echo‐free space at the time of effective RF resulting in heart rate reduction. In two patients without effective heart rate reduction, echodensity changes never reached the epicardium. No complications (superior vena cava‐right atrial junction orifice narrowing > 50% or pericardial effusion) of RF were identified. Conclusion: An echocardiographically guided anatomic approach to RF ablation of inappropriate sinus tachycardia is safe and effective. A characteristic echocardiographic signature suggesting transmural/epicardium damage appears to be present at the time of successful heart rate reduction and may serve as an appropriate guide for directing additional RF when using this anatomic echocardiographically based approach.
New Method for Predicting Efficiency of Heating by Measuring Bioimpedance During Radiofrequency Catheter Ablation in Humans
Authors: KO WEN‐CHIN , HUANG SHOEI K. STEPHEN , LIN JIUNN‐LEE , SHAU WEN‐YI , LAI LING‐PING , CHEN PAUL H. 
Published: August 2003

Bioimpedance During Radiofrequency Catheter Ablation.
Introduction: Efficiency of heating (defined as the average temperature divided by the average power) during radiofrequency (RF) catheter ablation (RFCA) can be predicted by the electrode‐tissue contact pressure before RFCA. To predict the efficiency of heating during RFCA, we prospectively measured bioimpedance and correlated the bioimpedance with the efficiency of heating in patients undergoing RFCA for supraventricular tachycardias. Method and Results: Of 239 RF applications in 55 patients, bioimpedance was measured from the distal pair of the electrodes of the ablation catheter using an extremely low current (10 μ A at 45 kHz). Tip electrode temperature was measured with a closed‐loop RF generator. Efficiency of heating and the difference (Δbioimpedance) between preablation bioimpedance (measured from the target ablation site) and baseline bioimpedance (measured in the right atrium without tissue contact) were calculated. There was significant positive correlation between preablation bioimpedance and efficiency of heating (regression coefficient = 0.053; P = 0.003) and between Δbioimpedance and efficiency of heating (regression coefficient = 0.067; P = 0.003). The highest degree of correlation was found during RFCA of the accessory pathways in the left free wall (regression coefficient = 0.14; P < 0.01). With preablation Δbioimpedance > 21.5 Ω, applications targeted at the left free‐wall, left posteroseptal, or right septal accessory pathways had a greater likelihood of achieving effective tissue heating (defined as maximal temperature achieved > 55°C). Conclusion: Both preablation bioimpedance and Δ bioimpedance have positive correlation with efficiency of heating during RFCA of supraventricular tachycardia. Measuring preablation bioimpedance appears to be a useful tool for predicting the efficiency of heating during RFCA.
Shortening the Second Phase Duration of Biphasic Shocks: Effects of Class III Antiarrhythmic Drugs on Defibrillation Efficacy in Humans
Authors: MERKELY BÉLA , LUBIŃSKI ANDRZEJ , KISS ORSOLYA , HORKAY FERENC , LEWICKA‐NOWAK EVA , KEMPA MACIEJ , SZABOLCS ZOLTÁN , NYIKOS GYÖRGY , ZIMA ENDRE , ŚWIĄTECKA GRAŻYNA , GELLÉR LÁSZLÓ 
Published: August 2003

Optimizing the Second Phase of Biphasic Shocks.
Introduction: The specific waveform providing optimal defibrillation threshold (DFT) is unknown. We compared the defibrillation efficacy of biphasic pulses with second phases (P2) of 2 and 5 msec in a randomized prospective clinical study. Methods and Results: Intraoperative DFTs of 62 patients (age 54 ± 13 years; ejection fraction 43% ± 17%; amiodarone 47%, d,l‐sotalol 13%) were determined in random order using a binary search protocol. Anodal shocks of 60% tilt first phases (P1) and P2 of 2 msec/5 msec were delivered from two 100‐μ F capacitors between the right ventricular electrode and the test housing of a Phylax 06/XM device. Mean DFT was significantly lower using the shorter P2 (9.5 ± 4.5 J vs 11.3 ± 5.2 J; P < 0.0001). According to subgroup analysis, the effect of changing P2 duration was only influenced by antiarrhythmic treatment. DFT decreased markedly using the shorter P2 in patients treated with amiodarone (10.7 ± 4.9 J vs 13.4 ± 5.6 J; P < 0.00001) or d,l‐sotalol (6.1 ± 3.3 J vs 9.1 ± 4.6 J; P < 0.05). The difference in patients not treated with Class III drugs was found to be insignificant. Chronic amiodarone treatment increased DFT only when the longer P2 was used. Conclusion: Biphasic shocks with shorter P2 should be used in patients undergoing Class III antiarrhythmic treatment.
Reduced Anisotropy of Action Potential Conduction in Left Ventricular Hypertrophy
Authors: CAREY PETER A. , TURNER MARK , FRY CHRISTOPHER H. , SHERIDAN DESMOND J. 
Published: August 2003

Conduction and Left Ventricular Hypertrophy.
Introduction: The aim of this study was to determine if anisotropic action potential conduction was altered during development of left ventricular hypertrophy (LVH). Methods and Results: Isolated guinea pig left ventricular preparations from hearts that had developed LVH were used to measure conduction velocity in longitudinal and transverse orientations to the fiber direction. A variable degree of LVH was induced by placing a ring around the ascending aorta for 50 to 250 days. Results were compared with an age‐matched control group that underwent a similar operation but with no ring placement. LVH was measured as the heart‐to‐body‐weight ratio (HBR), which correlated with an increase of mean myocyte cross‐sectional area. Longitudinal conduction velocity (LCV) declined progressively as HBR increased (mean ± SD: sham vs LVH: HBR 3.74 ± 0.30 g/kg vs 4.53 ± 0.52 g/kg; LCV 72.8 ± 15.5 vs 63.6 ± 11.1 cm/sec). Mean transverse conduction velocity (TCV) was greater in LVH compared with control (20.5 ± 4.7 cm/sec vs 25.4 ± 8.1 cm/sec), but there was no significance in the trend as a function of HBR. The anisotropic ratio (LCV/TCV) significantly declined as HBR increased. The time constant of the foot of the action potential was smaller in the transverse compared with the longitudinal dimension. There was no influence of hypertrophy. Conclusion: The decrease of LCV and reduction of the anisotropic conduction ratio suggest remodeling of the tissue in LVH. The consequences for the generation of arrhythmias are discussed.
Atrial Size Reduction as a Predictor of the Success of Radiofrequency Maze Procedure for Chronic Atrial Fibrillation in Patients Undergoing Concomitant Valvular Surgery
Authors: CHEN MIEN‐CHENG , CHANG JEN‐PING , GUO G. BIH‐FANG , CHANG HSUEH‐WEN 
Published: August 2003

Radiofrequency Maze Procedure and Atrial Size.
Introduction: Previous studies showed that the surgical maze procedure can restore sinus rhythm and atrial transport function in patients with chronic atrial fibrillation (AF). However, no previous studies discussed the association of atrial size reduction and the success of sinus conversion by the radiofrequency (RF) maze procedure for chronic AF. Methods and Results: A total of 119 chronic AF patients undergoing valvular operations were included in this study. Sixty‐one patients received RF and cryoablation to create lesions in both atria to simulate the surgical maze II or III procedure (RF maze II or RF maze III; 13 patients, group 1) or a modified maze pattern (RF maze “IV”; 48 patients, group 2). The other 58 patients who underwent valvular operations alone without the maze procedure served as control (group 3). At 3‐month follow‐up after operation, sinus rhythm was restored in 73%, 81%, and 11% of patients in groups 1, 2 and 3, respectively. Preoperative left and right atrial sizes were not statistically significant predictors of sinus conversion by the RF maze procedure. However, as a result of postoperative reduction of atrial sizes, postoperative left atrial diameter was significantly smaller in patients who had sinus conversion by the RF maze procedure than in patients who did not regain sinus rhythm (45.0 ± 7.0 mm vs 51.0 ± 8.0 mm; P = 0.03). Postoperative right atrial area of patients who had sinus conversion by the RF maze procedure also was significantly smaller than that of patients who did not regain sinus rhythm (18.1 ± 4.4 cm2 vs 28.5 ± 8.2 cm2; P = 0.008). Conclusion: Atrial size reduction appears to predict the success of sinus conversion with the RF maze procedure used in conjunction with valvular surgery.