bluuebunny/crossref_metadata_2025 huggingface dataset:
Dispersion of the QT Interval as a Predictor of Cardiac Death in Patients with Coronary Heart Disease
Authors: TRUSZ‐GLUZA MARIA , WOŹNIAK‐SKOWERSKA IWONA , GIEC LESZEK , SZYDLO KRZYSZTOF
Published: July 2006

Abnormal dispersion of the QT interval (QTd), measured as interlead variability of QT, may reflect a regional variation in duration of ventricular action potential and, hence, of cardiac electrical instability. In this retrospective study, we analyzed the effect of QTd on survival and its relation to other known predictors of subsequent cardiac death (CD) and sudden cardiac death (SCD) in 162 patients with coronary heart disease (CHD). QTd was calculated as the difference between the highest and lowest values measured in each of the 12 ECG leads (Qtmax ‐ QTmin). Seventeen CDs occurred, including nine SCDs, during a 25 ± 11 month follow‐up. There were significant differences in CD (P < 0.001 in log‐rank test) and in SCD (P < 0.01). The 1‐ and 3‐year survivals were 87.5% and 76.5% in patients with QTd > 0.060 seconds versus 98% and 93.5% in patients with QTd < 0.060 seconds, respectively. Additionally, a stepwise Cox regression analysis revealed that increased QTd was an independent risk factor of CD and SCD. A cut‐off value of 60 ms for QTd had a 53% sensitivity and 79% specificity in discriminating patients who are at risk of CD. The positive and negative prognostic values were 23% and 93%, respectively. Our findings support the hypothesis that increased QTd has a prognostic value in the stratification of patients with CHD independent of other known risk factors.
Effects of Ischemia and Reperfusion on QT Dispersion During Coronary Angioplasty
Authors: MICHELUCCI ANTONIO , PADELETTI LUIGI , FRATI MARCO , MININNI SIMONE , CHELUCCI ANDREA , STOCHINO M. LETIZIA , SIMONETTI IGNAZIO , GIGLIOLI GRISTINA , MARGHERI MASSIMO , GENSINI GIAN FRANCO
Published: July 2006

The effects of ischemia and reperfusion on QT interval dispersion (QTD: QTmax‐QTmin in the 12‐lead ECG) were analyzed in 15 patients (12 males, 57 ± 13 years) undergoing coronary angiopiasty (PTCA). AH patients had single‐vessel coronary artery disease (only one ≥ 85% stenosis in a major coronary artery) and normal left ventricular function. AH were in sinus rhythm with normal atrioventricular and intraventricular conduction on the surface ECG. No patient was on therapy that could affect the QT interval. The ECG was recorded (all 12 leads simultaneously) at 50 mm/s speed before the first balloon inflation, at the end of the first inflation during PTCA, and at 30″ and 60″ during reperfusion following the first inflation. In order to avoid ischemic preconditioning, only recordings of the first inflation were used. In each tracing QTmax and QTmin were evaluated. All values were rate corrected using a simple linear equation (QT linear corrected = QT + 0.154 [1‐RR]). QTD increased significantly during both ischemia and reperfusion. QTmax was not changed by ischemia and was increased by reperfusion. QTmin was reduced by ischemia and increased by reperfusion. These results indicate that both ischemia and reperfusion alter ventricular repolarization, inducing a less homogeneous ventricular recovery pattern.
Determinants of the Natural Course of Ventricular Late Potentials After Thrombolytic Therapy for Acute Myocardial Infarction
Authors: JUNG JENS , HEISEL ARMIN , BAY WOLFGANG , FRIES ROLAND , SCHIEFFER HERMANN , ÖZBEK CEM
Published: July 2006

The intraindividual changes of ventricular late potentials and their possible determinants were examined prospectively in 88 consecutive patients (male: 75; mean age: 58 ± 9 years) after thrombolytic therapy for acute myocardial infarction. Late potential analysis was performed 4 weeks and 12 months after acute myocardial infarction. At the same time, a left heart catheterization was performed to assess the extent of coronary heart disease and left ventricular ejection fraction. The incidence of late potential 4 weeks after acute myocardial infarction was 15% (13/88 patients). Eighteen percent (16/88) of the patients revealed changing results of late potential analysis: 9 patients lost late potential (late potential pos./neg.) 1 year after acute myocardial infarction and 7 patients presented new formation of late potential (late potential neg./pos.). Preserved late potentials were found in four patients (late potential pos./pos.). Late potential analysis remained negative in 68 patients (late potential neg./neg.). There was no influence of age, gender, site of infarction, clinical course, and medical treatment on the natural course of late potential. Changing results of late potential analysis seemed to be correlated with the evolution of left ventricular ejection fraction and the dynamics of coronary heart disease. In the group late potential pos./pos., comparable values for left ventricular ejection fraction were measured at both examinations, whereas late potential neg./neg. had a significant increase in ejection fraction. In the group late potential pos./neg., a significant improvement in left ventricular function was also measured. In contrast, the late potential neg./pos. group tended to have lower left ventricular ejection fractions 1 year after infarction. In the late potential neg./pos. and late potential pos./pos. groups, the extent of coronary artery disease returned to conditions comparable to baseline despite an initial reduction after coronary revascularization performed 4 weeks after infarction. Late potential neg./neg. and late potential pos./neg. revealed a stable benefit gained from coronary revascularization with a persistent reduction in the number of diseased vessels. Dynamic changes in the results of the signal‐averaged ECG 1 year after thrombolytic therapy for acute myocardial infarction were observed in 18% of the patients. These changes seem to be correlated with the evolution of left ventricular function and the dynamics of coronary artery disease.
ST Reelevation at Reperfusion is Associated with the Occurrence of Late Potentials in Patients with Acute Anterior Infarction
Authors: OCHIAI MASAHIKO , ISSHIKI TAKAAKI , OSHIMA AKIO , TOYOIZUMI HIDEKI , KONDO KIYOYUKI , TAKESHITA SATOSHI , SATO TOMOHIDE , MIYASHITA HIDEO
Published: July 2006

The relationship between ST reelevation at reperfusion and the occurrence of late potentials (LPS) in 35 patients with a first anterior infarction who had single vessel disease was investigated. All patients underwent a successful primary angioplastv and had a patent infarct related artery confirmed angiographically 4 weeks later. Patients were classified into groups based on changes in the ST level at reperfusion: patients with ST reelevation (group A, n = 22) and patients without ST reelevation (group B, n = 13). Signal‐averaged ECG was performed 4 weeks after primary angioplasty to detect LPS. Cineventriculography was performed to measure left ventricular ejection fraction (LVEF) and evaluate regional wall motion of the infarct area (SD/chords). LPS were present in eight of the 22 group A patients (36%) and in none of the 13 group B patients (P < 0.05). Left ventricular function was impaired in patients in group A compared with patients in group B (LVEF: 51 ± 12 vs 63 ± 10, P < 0.01; SD/chords: −2.7 ± 0.9 vs −1.9 ± 1.1, P < 0.05). These data suggest that ST reelevation and myocardial damage at reperfusion are associated with the occurrence of LPS in patients with successfully recanalized infarct related arteries after acute anterior infarction.
Evolution of Late Potentials During the First 8 Hours of Myocardial Infarction Treated with Thrombolysis
Authors: PETERS WERNER , KOWALLIK PETER , WILHELM KARIN , MEESMANN MALTE
Published: July 2006

It has been demonstrated that successful thrombolytic therapy is associated with a reduction of late potentials in the signal‐averaged electrocardiogram (SAECG) recorded within 48 hours after hospital admission. This study extends these observations, using for the first time a longitudinal design investigating whether ischemia and its potential reversal by thrombolytic therapy are associated with dynamic changes in SAECG recordings obtained continuously for 8 hours after the start of therapy in patients with acute myocardial infarction (MI). SAECGs were obtained from 12 patients (2 women and 10 men; ages 63 ± 13 years) with acute MI. The SAECG (X2+ Y2+ Z2)1/2 was generated with a high pass filter of 40 Hz, noise ≤ 0.3 μV. Comparing the SAECG recordings during the first and eighth hours, there was a significant decrease in filtered QRS duration (fQRS; 119.5 ± 17.1 vs 106.3 ± 15.3 ms) and duration of the low amplitude signals ≤ 40 μV of the terminal QRS (LAS40; 48.8 ± 18 vs 34.2 ± 14.2 ms), and increase of root mean square voltage of the last 40 ms of the QRS (t‐RMS; 14.8 ± 9.3 vs 37.8 ± 34.4 μV) (rank test, P ≤ 0.05). In this patient series, there was a significant improvement of fQRS, t‐RMS, and LAS40 during the first 8 hours of acute MI, perhaps indicating reversal of ischemia with thrombolysis. Even during acute MI, these markers of delayed conduction allow investigation of intervention induced changes in myocardial conduction and possibly prediction of the patency of the infarct related artery using signal‐averaging techniques.
Value of Time‐ and Frequency‐Domain Analysis of Signal‐Averaged Electrocardiography for Arrhythmia Risk Prediction in Idiopathic Dilated Cardiomyopathy
Authors: GRIMM WOLFRAM , HOFFMANN JÜRGEN , KNOP URSULA , WINZENBURG JENS , MENZ VOLKER , MAISCH BERNHARD
Published: July 2006

Signal‐averaged electrocardiography (SAECG) was performed in 120 consecutive patients with idiopathic dilated cardiomyopathy (IDC), and in 60 healthy controls. Time‐domain analysis of SAECGs revealed ventricular late potentials in 27 of 120 patients with IDC (23%) compared to 2 of 60 controls (3%; P < 0.05). Frequency‐domain analysis of SAECGs showed ventricular late potentials in 9 of 120 patients with IDC (8%) compared to none of the 60 controls (0%, P < 0.05). During a prospective follow‐up of 15 ± 7 months, serious arrhythmic events, defined as sustained ventricular tachyarrhythmias or sudden death, occurred in 17 of 120 patients with IDC (14%). The sensitivity, specificity, and positive and negative predictive values of ventricular late potentials for serious arrhythmic events were 35%, 80%, 22%, and 88% for the time‐domain analysis, and 18%, 94%, 33%, and 87% for the frequency‐domain analysis of SAECG, respectively. Thus, neither the time‐ nor the frequency‐domain analysis of SAECG appears to be useful for risk stratification in the setting of IDC in view of their low sensitivity and low positive predictive value for serious arrhythmic events during follow‐up.
Analysis of the P Wave in the Signal‐Averaged Electrocardiogram: Normal Values and Reproducibility
Authors: HOFMANN MONIKA , GOEDEL‐MEINEN LISELOTTE , BECKHOFF ANGELIKA , REHBACH KATHRIN , SCHÖMIG ALBERT
Published: July 2006

To apply p wave analysis of the signal‐averaged electrocardiogram (SAECG) clinically, the knowledge of normal values and the verification of highly reproducible measurements are essential. In 40 healthy volunteers (ages 23 ‐37 years), an SAECG of the p wave was performed and then repeated after 1 week and 1 month. In addition to Simson analysis (unidirectional and bidirectional filters), the data were filtered with finite impulse response (FIR) and least squares fit (LSQ) filters to obtain a better differentiation between the end of the p wave and QRS onset. All recordings were evaluated by two independent observers, and the following parameters were calculated: the duration of the p wave in the three unfiltered leads; and for the vector magnitude of the three leads x, y, and z: the duration of the p wave and the root mean square voltage of its last 30, 20, and 10 ms. The average p wave duration was significantly different among the various filter techniques: 135 ± 7 ms (unidirectional); 97 ± 8 ms (bidirectional); 109 ± 8.5 ms (FIR); and 126 ± 10 ms (LSQ) (P = 0.001 for each comparison). There was a good reproducibility of the data analyzed with the Simson method (R = 0.80–0.91). Filtering with the FIR and LSQ leads to a considerably greater variability.
Conversion of Recent Onset Atrial Fibrillation with Single Loading Oral Dose of Propafenone: Is In‐Hospital Admission Absolutely Necessary?
Authors: BOTTO G.L. , BONINI W. , BROFFONI T. , MOLTENI S. , LOMBARDI R. , ALFIERI G. , BARONE P. , BERNASCONI G. , FERRARI G.
Published: July 2006

A population of 283 patients with recent onset (< 72 hours) AF, without heart failure, who received a single 450‐ or 600‐mg oral dose of propafenone, or digoxin 1 mg, or placebo for conversion to sinus rhythm (SR), was studied to determine whether a routine admission to the hospital for drug administration is justified. Previous bradyarrhythmias or sick sinus syndrome (SSS), and concomitant use of antiarrhythmic drugs were exclusion criteria. None of the 283 patients studied experienced VT or VF and none of them needed implantation of a temporary pacemaker. Periods of atrial tachyarrhythmias with regularization of atrial waves and 1:1 AV conduction were observed in only two cases, both receiving placebo. No predictor of proarrhythmia was found among the clinical variables considered (age, etiology, arrhythmia duration, atrial dimension, and blood potassium). No serious hemodynamic adverse effects were noted in either group. The rates of conversion to SR after 4 hours were: 80 (57%) of 141 patients who received propafenone and 35 (25%) of 142 patients who received digoxin or placebo (P < 0.001). Acute oral treatment with propafenone is simple and effective for the conversion of recent onset AF to SR in patients without clinical signs of heart failure. The routine admission of these patients to the hospital is not necessary. Home‐based administration of oral propafenone to a selected group of patients could significantly increase the cost effectiveness of this treatment.
Atrial Arrhythmia Following a Biatrial Approach to Mitral Valve Surgery
Authors: BERNSTEIN NEIL E. , SKIPITARIS NICHOLAS T. , GLOTZER TAYA V. , DELIANIDES JULIE , CHINITZ LARRY A. , COLVIN STEPHEN
Published: July 2006

The biatrial approach to exposing the mitral valve during surgery has the potential for improving visualization of the valve with minimal cardiac manipulation. This procedure, involving a right atriotomy and an extended transseptal incision, may isolate the sinus node from its normal blood supply and autonomic innervation. Thirty‐eight consecutive patients undergoing this procedure were examined. Twenty‐two of these patients (58%) were admitted in normal sinus rhythm and 15 (40%) were in atrial fibrillation (AF) or atrial flutter. Of the 22 patients admitted in normal sinus rhythm, only 3 patients remained in this rhythm at discharge. Fourteen of the 22 patients were discharged in a slow, low atrial rhythm. All of the patients admitted in AF were discharged in AF. Of the 14 patients discharged in a low atrial rhythm, the rhythm persisted in eleven patients (80%) at a mean of 6‐month follow‐up. The routine use of this transseptal approach to mitral valve surgery needs further assessment in light of the predictable loss of the sinus mechanism.
Combined Transesophageal Left Atrial Pacing and Antiarrhythmic Therapy in the Treatment of Atrial Flutter
Authors: MATIOUCHINE G.V. , SHULMAN V.A. , BALOG A.I. , BEZRUK A.P. , GOLOVENKIN S.E.
Published: July 2006

In order to terminate atrial flutter (AF) overdrive transesophageal left atrial pacing (TELAP) was performed in 760 patients with paroxysmal AF. There were 315 women and 415 men (mean age 59 years). In 260 patients, TELAP was used in an outpatient setting. Approximately half of the patients (51 %) had coronary artery disease and/or arterial hypertension, and 23% of the patients had no structural heart disease. The duration of AF ranged between 1 hour and 1 month. TELAP was performed in 312 patients without any antiarrhythmic drug (AAD) administration (group I) and in 448 patients after administration of AAD (procainamide and/or amiodarone) in conventional doses (group II). TELAP resulted in immediate return of sinus rhythm in 85 patients (27%) of group I and in 222 patients (50%) of group II (P < 0.001). TELAP converted AF to atrial fibrillation (AFIB) in 185 of group I and in 214 (48%) of the group II patients (P < 0.01). In addition, within 1–2 days after TELAP AFIB converted to sinus rhythm spontaneously or after AAD in 87 patients of group I (28%) and in 84 (19%)of the group II patients (P < 0.01). In general, sinus rhythm was restored in 172 (55%) of the group I and in 306 (68%) of the group II patients (P < 0.005). AF was converted to AFIB in 98 (31 %) of the group I and in 130 (29%) of the patients in group II patients (NS). TELAP was ineffective in 42 (13.5%) of the group I and in 12 (3%) of the group II patients (P < 0.001). TELAP was an effective noninvasive method for the treatment of recent onset AF. Our experience showed that after TELAP, sinus rhythm was restored in most of the patients with paroxysmal AF within 1–2 days. In some patients TELAP converted AF to AFIB, making it easier to control the heart rate with AAD. Treatment with AAD before TELAP increased its effectiveness.
Reproducibility of Transesophageal Pacing in Patients with Wolff‐Parkinson‐White Syndrome
Authors: FENICI RICCARDO , RUGGIERI MARIA PIA , di LILLO MARIANGELA , FENICI PETER
Published: July 2006

The purpose of this study was to assess, in patients with ventricular preexcitation, the time dependent physiological variation of antegrade conduction properties in the AV node and in accessory pathways (Aps) as a function of autonomic tone variation induced by posture and physical effort, using noninvasive transesophageal atrial pacing. In 74 WPW patients (mean age 21.31 ± 9.46 yrs), AV node and Kent antegrade effective refractory periods (at pacing cycle lengths 600. 400, and 320 ms), Wenckebach point, shortest preexcited ER intervals during sustained atrial fibrillation (AF) or atrial pacing, as well as the inducibility of AV reentry tachycardia (A VRT) and AF/flutter (AFL) were assessed. AH measurements were carried out at rest, in supine and upright positions, and during effort. A second study was carried out approximately 3 months after the first study. The coefficients of variation (CVs) and reproducibility (CRs) were calculated. For each parameter, the differences between the mean of the two studies were not statistically significant. The CVs and CRs ranged between 0.4% and 4% and between 2 and 28 ms, respectively. AF was induced in 40 (54%) of 74 patients at the first study and in 30 (40.5%) of 74 patients at the second study. AVRT was induced in 33 (45%) of 74 patients at the first study and in 38 (51.3%) of 74 patients at the second study. The reproducibility was 45% for AF/AFL and 65% for reentry tachycardia. Transesophageal atrial pacing is a reliable method for noninvasive reproducible evaluation of ante‐ grade electroph ysiological properties of both the AV node and APs in WPW patients. However, the effect of autonomic balance variation has to be taken into account and precisely defined because it may significantly affect the inducibility of supraventricular arrhythmias and the estimation of the absolute values of the vulnerable parameters.
Alcohol Concentration Determines the Type of Atrial Arrhythmia Induced in a Porcine Model of Acute Alcoholic Intoxication
Authors: ANADON MARÍA J. , ALMENDRAL JESÚS , GONZÁLEZ PABLO , ZABALLOS MATILDE , DELCAN JUAN L. , DE GUEVARA JAVIER L.
Published: July 2006

Alcohol abuse has long been suspected clinically to cause paroxysmal atrial tachyarrhythmias. However, such a relationship has never been conclusively proven, partly due to the lack of experimental evidence. Although atrial fibrillation (AF) is the most common atrial arrhythmia attributed to acute alcoholic ingestion, atrial flutter has occasionally been noted. We analyzed the possible role of alcohol in initiation and/or maintenance of a variety of atrial tachyarrhythmias in a closed‐chest porcine model. Nine pigs underwent nine endocnrdial right atrial stimulation protocols (EASP) at baseline and 17 RASPs after increasing doses of ethanol (first infusion 1,230 mg/kg, second infusion 870 mg/kg) by means of one multipolar catheter advanced under heavy sedation from the femoral vein. Each RASP included 1, 2, and 3 extrastimuli, and rapid pacing at 5 times diastolic threshold. Venous ethanol concentrations were measured (HPGC method) every 10 minutes and at the time of arrhythmia induction. Atrial tachyarrhythmias were induced in 4 of 9 baseline RASPs, and lasted for a mean of 21 seconds, and in 16 of 17 RASPs after alcohol lasting for a mean of 357 seconds. Only fibrillation was observed at the baseline RASP. The atrial tachyarrhythmias induced after alcohol were AF in 11 RASPs and atrial flutter in 5 RASPs (in 5 animals). The mean venous ethanol concentration at the time of the longest arrhythmia induced for each RASP were 200 ± 89 mg/dL for RASP inducing fibrillation and 292 ± 40 mg/dL for RASP inducing flutter (P < 0.05). Flutter tended to be sustained (> 1 minute in duration) more often than fibrillation (4 of 5 flutter vs 2 of 11 fibrillation P < 0.05). In three experiments, atrial flutter persisted for > 10 minutes and was terminated by overdrive atrial pacing. We concluded: (1) in this closed‐chest porcine model, an ethanol infusion facilitates a variety of atrial arrhythmias related to the ethanol concentration; (2) flutter tended to be sustained, and its termination by overdrive pacing suggests the possibility of an alcohol induced reentrant mechanism: and (3) the higher concentration required for atrial flutter, exceeding that usually seen in humans, may help to explain the rarity of atrial flutter in clinical alcohol intoxication.
Effect of Digoxin on the Ventricular Rate Variability During Paroxysmal Atrial Fibrillation
Authors: HNATKOVA KATERINA , MURGATROYD FRANCIS D. , CAMM A. JOHN , MALIK MAREK
Published: July 2006

This study investigated whether the, irregularity of ventricular cycle length during atriai fibrillation (AF) is affected by digoxin. Patients (n = 41) with paroxysmal AF enrolled in a randomized crossover comparison of digoxin and placebo underwent 24‐hour ambulatory monitoring during each treatment. Tapes containing AF episodes lasting at least 2 minutes were selected (24 recordings on placebo and 17 on digoxin). The mean (mRR) and standard deviation (SDRR) of RR intervals was calculated for each 30‐second segment of AF. The resulting SDRR values were clustered according to bins of mRR values ranging from 350–650 ms in 25‐ms steps. In each bin, the SDRR values of all placebo and all digoxin recordings were statistically compared for the top 5, 10, and 15 percentiles of each bin which represented the extremes of ventricular cycle length irregularity during AF. There were no significant differences between the total data of SDRR values in individual bins of mRR. However, the top 5, 10, and 15 percentiles of SDRR values corresponding to mRR values from 350–550 ms were significantly reduced by digoxin (P < 0,0001). The study concludes that although digoxin does not influence the mean variability of RR cycles during AF paroxysms, it suppresses episodes in which a fast ventricular response is associated with extreme variability of RR periods.
Initial and Long‐Term Evaluation of Escape Rhythm After Radiofrequency Ablation of the AV Junction in 50 Patients
Authors: PIOT OLIVIER , SEBAG CLAUDE , LAVERGNE THOMAS , OLLITRAULT JACKY , JOHNSON NICOLAS , DINANIAN SYLVIE , LE HEUZEY JEAN‐YVES , GUIZE LOUIS , MOTTÉ GILBERT
Published: July 2006

Between 1986 and 1994, 50 patients (mean age 63 ± 13 years), 25 of whom had organic heart disease and presenting with atrial arrhythmias refractory to 5.6 ± 1.6 antiarrhythmic drugs, underwent radiofrequency ablation (5 ± 3 pulses by procedure; duration of pulses 50.5 ± 32 s) of the proximal AV junction to create complete and permanent AV block. The escape rhythm was studied immediately after the procedure and during long‐term follow‐up. Immediately after the procedure, an escape rhythm was observed in 80% of the patients (junctional in 92%). Over a mean follow‐up of 36 ± 16 months in 47 patients (2 patients died before assessment of escape rhythm and 1 was lost to follow‐up), an escape rhythm was present in 39 patients (83%) and absent in the remaining 8 (17%). The only significant difference between the two groups was the initial presence of an escape rhythm (P = 0.008). However, three patients with an initial escape rhythm had none during long‐term follow‐up. The initial presence of an escape rhythm as a predictive factor of its presence during follow‐up had a sensitivity of 87%, specificity of 63%, positive predictive value of 92%, and negative predictive value of 50%. Thus, the absence of an escape rhythm during long‐term follow‐up causing pacemaker dependency was noted in 1 of 6 patients. This represents a limitation to this palliative treatment, which should be reserved for patients suffering from supraventricular tachycardias refractory to other treatments.
Is Vagal Innervation to the Atrioventricular Node Impaired After Radiofrequency Ablation of the Slow Atrioventricular Nodal Pathway?
Authors: KAUTZNER JOSEF , HARTIKAINEN JUHA , HEALD SPENCER , MALIK MAREK , WARD DAVID , ROWLAND EDWARD
Published: July 2006

To assess the potentially adverse effects of RF catheter ablation (RFCA) of the slow AV nodal pathway on the parasympathetic innervation to the AV node in patients with AV nodal reentrant tachycardia (AVNRT), AV nodal conduction was evaluated following vagal stimulation by means of a phenylephrine bolus injection (200 μg) before and after RFCA in ten patients (mean age, 37 ± 14 years). Nine patients with AV reentrant tachycardia (AVRT) due to a left free wall accessory pathway served as a control group (mean age of 37 ± 12 years). Whereas no prolongation of the AH interval was observed in the AVNRT group following the phenylephrine bolus during sinus rhythm, despite a significant slowing in sinus rate, phenylephrine administration in AVRT patients was associated with both slowing of the sinus rate and prolongation of the AH interval. Following successful RFCA, the same responses were observed. To delineate the indirect effect of heart rate on AV conduction in response to the phenylephrine bolus, the AH interval was also measured during fixed atrial pacing. A marked prolongation of the AH interval occurred in both groups following phenylephrine administration. This prolongation was biphasic in 50% of A VNRT patients before ablation, suggesting a predominant effect of vagal stimulation on the fast AV nodal pathway. RFCA was associated with disappearance of discontinuous AV conduction in all but one patient with AVNRT. Vagal stimulation caused the same amount of AH interval prolongation as before RFCA in both study groups. In conclusion, patients with AVNRT have a preserved modulation of AV nodal conduction in response to vagal stimulation during sinus rhythm. In addition, vagal stimulation seems to exert a predominant effect on the fast A V nodal pathway. RFCA of the slow AV nodal pathway in patients with A VNRT does not cause detectable damage to the vagal innervation to the AV node.
Regional Disparities of Endocardial Atrial Activation in Paroxysmal Atrial Fibrillation
Authors: JAÏS PIERRE , HAÏSSAGUERRE MICHEL , SHAH DIPEN C. , CHOUAIRI SALAH , CLÉMENTY JACQUES
Published: July 2006

Previous experimental data suggest that atrial activity is homogeneously distributed during paroxysmal atrial fibrillation (AFib). Little is known about this in human paroxysmal AFib. Methods: Twenty‐five men and two women (mean age 49 ± 11 years; five with structural heart disease) with paroxysmal AFib for a mean 5 ± 6.2 years despite the use of a mean of 3.6 ± 1.7 antiarrhythmic drugs underwent atrial mapping. The right atrium was divided into four regions: posterior (intercaval), lateral, anterior, and septal. A 14‐pole catheter was positioned to assess complex electrical activity defined as the duration of continuous electrical activity or electrograms with FF intervals < 100 ms for 60 seconds (expressed as percentage of time). In addition, the left atrium (divided into three regions: posterior, anterior, and septal) was explored in 12 patients with a multipolar catheter. Results: The complex electrical activity time between all the regions explored was significantly different. In the right atrium, the septa] (74%± 32%; P = 0.02) and the posterior (63%± 32%; P = 0.04) areas were significantly more disorganized than the lateral (22%± 23%) and anterior (21 %± 26%) regions. In the left atrium, complex electrical activity was predominant and widely distributed (posterior: 87%± 11%; septal: 65%± 27%) except in the appendage area (anterior region: 18%± 14%). Conclusions: Quantitative assessment of complex electrical activity in both atria in humans shows heterogeneous temporal and spatial distribution. This may have implications for guiding catheter ablation of AFib.
Lack of Evidence of Areas of Slow Conduction Early After Radiofrequency Current Application at Porcine Atrial Myocardium
Authors: PAUL THOMAS , MAHNERT BRITTA , TRAPPE HANS J. , MAAß ANNE , BÖKENKAMP REGINA , MEYER PETRA , BRÜCKNER REINHARD
Published: July 2006

Electrophysiological sequelae after creation of atrial myocardial lesions by radiofrequency current (RFC) application have not been studied in vitro. During general anesthesia, a steerable 6 French electrode catheter, equipped with a thermistor at the 4‐mm tip electrode, was positioned at the lateral atrial aspect of the tricuspid valve annulus in 5 piglets (German Landrace, mean body weight 12.5 kg). Temperature‐guided (75°C) RFC (500 kHz) was delivered over 30 seconds. Forty‐ eight hours later, the hearts were removed and placed in ice‐cold Turner s solution. The right atria were dissected, and the RFC lesions with surrounding tissue were cut out and transferred to an organ bath according to Steiert. Preparations were superfused with Turner s solution at 37°C. Pacing of the viable tissue at the border of the preparations was accomplished at a cycle length of 500 ms. Whole atrial preparations ware impaled (76 to 150 impalements per specimen) with KC1 capillary microelectrodes containing 3 MKCl. In the surrounding viable tissue of the five preparations, mean maximum diastolic transmembrane potential ranged from −61.3 to −63.7 mV, mean action potential duration at 90% repolarization ranged from 135.2 to 156.1 ms, and mean maximum upstroke velocity of phase 0 of the action potential was between 104.7 and 112.9 V/sec. Statistical analysis revealed no significant differences among all 3 variables. No intracellular action potential was recorded from the surface of all 5 lesions. The surrounding tissue was sharply demarcated, with unaltered transmomhrane action potential characteristics in the vicinity of the lesions. Areas of slow conduction were not observed. Lack of evidence of areas of slow conduction after RFC application to the atrial myocardium may imply that this technique is safe regarding occurrence of atrial tachyarrhythmias.
Unipolar Recording and Pacing Using a Conductive Introducer Sheath as the Indifferent Electrode
Authors: GOLDMAN DANIEL S. , BUCK JERRICK C. , LARNARD DONALD J.
Published: July 2006

Unipolar recording has been shown to have advantages over bipolar techniques in certain clinical settings. Unipolar recording and pacing, however, require an indifferent electrode to complete the circuit. Current options for the indifferent electrode require additional hardware or special recording capabilities. A novel percutaneous unipolar conductive introducer sheath (PUCIS) was developed for unipolar electrophysiological recording and pacing. This article describes the development of this sheath, in vitro testing results, and initial animal data using the PUCIS as the indifferent electrode. The current silver/gold coating has acceptable mechanical and electrical properties. Electrogram appearance and amplitude, pacing thresholds, and impedances were comparable to currently used alternatives. The PUCIS sheath may therefore serve as a convenient standard as the indifferent electrode for unipolar electrophysiology.
Muscarinic Effects on Action Potential Duration and its Rate Dependence in Canine Purkinje Fibers
Authors: MALFATTO GABRIELLA , ZAZA ANTONIO , VANOLI EMILIO , SCHWARTZ PETER J.
Published: July 2006

Studies of the autonomic influence on action potential duration (APD) in the ventricles show direct effects of muscarinic stimulation on epicardial, but not endocardial, APD and conflicting results regarding direct vagal effects on the conduction system. In canine Purkinje fibers, we analyzed the action of the M2 agonist oxotremorine (OXO, 0.1μM) on APD and on its cycle length (CL) dependence. Fibers were impaled with glass microalectrodes and superfused with Tyrode s solution. APD90 was measured after 3 minutes of drive at CL between 0.3 and 5 seconds. The best fit for the APD/CL relationship at steady state was a hyperbole: APD = APDmax*CL/(CL+CL50), where APDmax (APD at infinite CL) is a rate independent measure of APD, and CL50 (CL at which 50% APDmax is reached) is an index of the rate dependence of APD. In five fibers, OXO reduced APD at all CL (P < 0.05), APDmax was also reduced to 377 ± 41 ms from 447 ± 34 ms (P < 0.05), while CL50 was unchanged (405 ± 46 ms from 437 ± 28 ms). No effects of OXO on APD and APDmax were seen in two fibers obtained from dogs pretreated with pertussis toxin (PTX). In conclusion, stimulation of M2 receptors in intact, and not PTX treated, Purkinje fibers affects APD but not its CL dependence. This may reflect the activation of a rate independent, background current through a GTP binding protein‐linked pathway, such as, IK.ACH These data differ from those obtained in endocardial and epicardial muscle, stressing the regional differences in vagal modulation of ventricular electrophysiological properties.
Analysis of High Frequency QRS Potential During Exercise Testing in Patients with Coronary Artery Disease and in Healthy Subjects
Authors: BEKER AMIR , PINCHAS ABRAHAM , EREL JACOB , ABBOUD SHIMON
Published: July 2006

High resolution ECG waveforms from leads V3, V4, V5, and V6 were analyzed in two groups of male subjects before, during, and following treadmill exercise testing. Group A included 32 coronary artery disease (CAD) patients, with arteriographically proven > 75% obstruction of at least two main coronary arteries, and group B included 30 healthy subjects, without history or symptoms of CAD. Signal averaging and filtering techniques ware used in order to enhance the signal‐to‐noise ratio of the recorded ECG. The averaged QRS waveforms were filtered between 150 and 250 Hz. QRS complexes of the four leads were combined to form a “precordial average complex” (PAC). The PAC signals were examined for each subject at different stages of the exercise test and two parameters were computed: the root mean square (RMS) voltage; and the peak amplitude. The values of RMS and peak amplitudes measured at each stage of the exercise test were normalized to the values at rest. Normalized RMS (NRMS) values at peak exercise, immediately after peak exercise, and during the recovery phase were found to be higher for the healthy subjects than for the CAD group (1.17 ± 0.31 vs 0.94 ± 0.26, P < 0.008 at peak exercise, 1.13 ± 0.24 vs 0.84 ± 0.19, P < 0.001 after peak exercise, 1.08 ± 0.22 vs 0.94 ± 0.17, P < 0.007 during recovery). Cut‐off NRMS value of one had a sensitivity of 81.3% and a specificity of 70.0% in differentiating CAD patients from healthy subjects in the examined groups. Normalized peak amplitude (NAMP) values exhibited similar behavior, with higher values for the healthy subjects than for the CAD group (1.23 ± 0.48 vs 0.94 ± 0.36, P < 0.03 at peak exercise, 1.20 ± 0.34 vs 0.83 ± 0.28, P < 0.001 after peak exercise, 1.10 ± 0.29 vs 0.94 ± 0.23, P < 0.02 during recovery). Specificity of 73.3% and sensitivity of 71.8% were found using a postpeak NAMP cut‐off value of 1. In conclusion, the present study shows that using high frequency ECG may contribute to identifying patients with CAD. Further studies in larger groups of patients are required to better define the true predictive value of the method described for the diagnosis of CAD.
Dual Level Sensing Significantly Improves Automatic Threshold Control for R Wave Sensing in Implantable Defibrillators
Authors: BREWER JAMES E. , PERTTU JOSEPH S. , KROLL MARK W. , DONOHOO ANN M. ,   THE ANGEION CORPORATION
Published: July 2006

ICDs must sense R waves over a range of amplitudes without sensing P or T waves. Automatic threshold control (ATC) is an accepted sensing method for that task. ATC sensing levels are from 25%‐75% of the electrogram (EGM) peak, decreasing with an exponential decay. A high sensing level for a time after peak detection may better allow ATC to pass over a T wave, while a lower sensing level thereafter may better allow ATC to sense the next R wave. An A TC was designed with two sensing levels and time constants (T), using a 58% level (T = 1,75 s) for 325 ms after peak detection switching to 33% (T = 1.1 sj thereafter, and was compared to a single level ATC (sensing level = 50%, T = 1.4 s). The two ATC circuits were tested with 22 arrhythmia EGMs to determine sensitivity and specificity rates at ± 1‐, 2‐, 5‐, 10‐, and 20‐mV amplitudes. It was confirmed that a dual level ATC significantly improves the sensitivity rate without degrading the high specificity rate of a standard sensing circuit.
Programmable Polarity: Effects on Pacing and Sensing of Bipolar Steroid‐Eluting Leads
Authors: SCHUCHERT ANDREAS , CAPPATO RICCARDO , KUCK KARL‐HEINZ , MEINERTZ THOMAS
Published: July 2006

Presently available bipolar pacemakers connected to bipolar leads allow the programming of polarity to either bipolar or unipolar configuration. The bipolar configuration improves sensing because of its lack of oversensing. In respect to the pacing impulse, it may be beneficial to program the bipolar to unipolar configuration, because the unipolar pacing configuration seems to lead to lower pacing thresholds. The aim of the study was to investigate the effects of the two configurations on pacing and sensing in 11 patients with a new ventricular steroid‐eluting lead (Encor Dec 033–301. Telectronics Inc.) connected to the same types of VVI(R) pacemakers. Follow‐up was 12 months after implantation. Pacing was assessed by pulse duration thresholds at 0.8‐, 1.6‐, and 2.5‐V pulse amplitude and by pacing impedance. Parameters for sensing included sensing thresholds, R wave amplitudes, and amplitude of intrinsic deflection. Pulse duration thresholds were similar for the two configurations. At implantation, pacing impedance was significantly higher with bipolar (672 ± 60 Ω) than with unipolar pacing configuration (626 ± 82 Ω, P < 0.005). The difference lasted until 1 month after implantation (bipolar: 670 ± 49 Ω: unipolar: 630 53 Ω, P < 0.01). No significant differences were detected after 3 (bipolar: 683 ± 63 Ω; unipolar: 662 ± 70 Ω) and 12 months (bipolar: 658 ± 64 Ω: unipolar: 660 ± 63 Ω) between the 2 configurations. Although intrinsic deflections of ventricular electrograms were different, mean R wave amplitudes were similar in unipolar and bipolar configuration. Pacing and sensing characteristics of unipolar and bipolar configuration were similar for the studied bipolar pacing lead. Pacing impedance was initially higher for bipolar than for unipolar configuration and equilibrated within 3 months after implantation.
Late Endocardial Pacing Lead Body Migration Compromising Fontan Physiology
Authors: O'CONNOR BRIAN K. , CASE CHRISTOPHER L. , WIENECKE MATTHEW M. , GILLETTE PAUL C.
Published: July 2006

Migration of intracardiac transvenous pacing leads may occur. There is a known risk of intrapul‐ monary ventricular pacing lead migration in patients with endocardial lead systems. In the current report we present the late intrapulmonary migration of an endocardial atrial pacing lead body. The patient had undergone antitachycardia pacemaker placement to control recurrent atrial tachyarrhythmias following the Fontan procedure. Although the lead electrode remained in place and continued to pace, the lead body migrated, causing severe obstruction to blood flow. This resulted in severe cardiac decompensation, which was ultimately ameliorated by lead repositioning.
Symptomatic Pericardial Disease Associated with Patch Electrodes of the Automatic Implantable Cardioverter Defibrillator: An Underestimated Complication?
Authors: CHEVALIER PHILIPPE , MONCADA ENRIQUE , CANU GUILLAUME , CLAUDEL JEAN‐PHILIPPE , BELLON CHRISTIAN , KIRKORIAN GILBERT , TOUBOUL PAUL
Published: July 2006

Constrictive pericarditis can be associated with ICD patch electrodes. During a mean follow‐up of 24 months, in a population of 35 patients who received ICDs with a patch electrodes configuration, we identified three patients with clinical and hemodynamic signs compatible with this event. Patient 1, a 35‐year‐old male, underwent implantation of an ICD because of a primary electrical disease complicated by cardiac arrest. Fourteen months later he complained ofexertional dyspnea without any signs of heart failure. Right heart catheter‐ ization showed high filling pressures and diastolic dip and plateau in pressure curves. Thoracotomy and pericardia! exploration were performed. Three months after removal of the patches and insertion of an endocardial lead system, the patient had normal respiration. Patients 2 and 3, who suffered from coronary heart disease without heart failure, exhibited a hemodynamic profile suggestive of constrictive pericarditis: in one patient, 10 months after ICD implantation, associated with right heart failure; and in the other, 18 months after ICD implantation with left heart failure. Patch electrodes were removed in these two patients and replaced by endocardial lead electrodes with subsequent clinical improvement. It is concluded that constrictive pericarditis related to epicardial patch is not an uncommon occurrence during ICD therapy and should be considered in patients who show clinical signs of cardiac decompensation.
Pacemaker Twiddler's Syndrome
Authors: CHERNILAS JOSEPH Z. , BILFINGER THOMAS V. , VLAY STEPHEN C.
Published: July 2006

Twiddler's syndrome may result from pulse generator manipulation or from spontaneous rotation due to movement around an inadequately secured electrode. In this case, the electrode became coiled in the right ventricular outflow tract.
Combined Third‐Generation Implantable Cardioverter Defibrillator with Permanent Unipolar Pacemakers: Preliminary Observations
Authors: HAFFAJEE CHARLES , CASAVANT DAVID , DESAI PRAKASH , MOON RICHARD , VOUKYDIS PANOS , PACETTI PATRICIA
Published: July 2006

As implantable Cardioverter defibrillators (ICDs) are strictly contraindicated in the presence of unipolar pacemakers, currently available options in patients having such chronic pacing systems include: abandoning the implanted pacemaker and selecting an ICD with ventricular demand (VVI) pacing; or replacing the chronic (dual chamber) unipolar pacing system with a dedicated bipolar version prior to ICD implantation. In three patients with previously implanted unipolar pacemakers, we challenged the premise that all ICD systems are incompatible by combining with a third‐generation transvenous ICD system (Medtronic 7217B PCD® incorporating true bipolar sensing, a self‐limiting auto‐adjusting sensitivity, and a tolerant VF detection algorithm. The potential for pace‐maker‐ICD interaction was minimized by separating the tip of the ICDs transvenous right ventricular pace/sense‐defihrillation coil lead from that of the chronic pacemaker lead by > 2–3 cm, and by performing “worst case” intraoperative testing. Although ICD double‐counting of the dual chamber pacemaker's atrial and ventricular pacing spikes could be provoked at extreme high output settings, it did not occur at clinically appropriate settings. More importantly, continuous high output asynchronous pacing during ventricular fibrillation (VF) did not interfere with ICD detection. During a mean follow‐up period of 18 months, one patient has had VF appropriately terminated bv the ICD. In the remaining two patients, proper VF detection and ICD function was reassessed at 3 months and/or at 1 year during noninvasive testing. Conclusion: These preliminary findings demonstrate that this transvenous ICD system's VF sensing and detection features combined with careful implant technique, rigorous “worst case” testing for possible pacemaker‐ICD interaction with regular follow‐up, may permit implantation of this ICD system in patients with chronic unipolar pacing systems. Further studies are needed to validate the long‐term clinical safety of this promising revised approach to a currently contraindicated device combination.
Acute Changes in Left Atrial and Left Ventricular Diameters After Physiological Pacing
Authors: ISHIKAWA TOSHIYUKI , KIMURA KAZUO , YOSHIMURA HIROSHI , KOBAYASHI KIMINARI , USUI TAKASHI , KASHIWAGI MASANOBU , ISHII MASAO
Published: July 2006

The present study examined alterations in left atria! diameter (LAD) and diastolic left ventricular diameter (LVDd) in 37 patients (72.2 ± 9.8 years old) who received physiological pacemakers; 22 with atrioventricular (AV) block and 15 with sick sinus syndrome (SSS). After pacemaker implantation, LAD and LVDd were serially measured using echocardiography, and their diameters ware expressed per body surface area (LADI and LVDdl; mm/m). Pulmonary capillary wedge pressure (PCWP) and cardiac output (CO) were measured in ten patients with SSS and ten with AV block during both right ventricular and AV sequential pacing. After AV sequential pacing, CO increased in 19 of 20 patients (3.2 ± 0.9 L/min to 3.9 ± 1.0 L/min: P < 0.001). LADI decreased from 24.9 ± 4.2 mm/m2 to 21.8 ± 4.4 mm/m2 (P < 0.001) in 22 patients with AV block and from 24.1 ± 3.4 mm/m2 to 20.4 ± 3.8 mm/m2 (P < 0.001) in 15 SSS patients. However, LVDdl did not change significantly in either group of patients. The changes in LAD after the implantation of a physiological pacemaker occurred rapidly, i.e. LAD began to decrease within 1 minute after the procedure, and then reached a plateau. This plateau phase continued for at least 7 days during physiological pacing. There was a positive correlation between the changes in LADI after pacemaker implantation and those in PCWP observed during the AV sequential pacing performed prim‐ to the implantation (r = 0.86; P < 0.001). The reduction in LAD following pacemaker implantation was rapid and seemed to be accompanied by improvement of cardiac function. Thus, it is suggested that the serial measurement of LADI is useful to predict the efficacy of physiological pacemaker implantation.
Mapping Guided Laser Catheter Ablation of the Atrioventricular Conduction in Dogs
Authors: WEBER HELMUT P. , HEINZE ARMIN , ENDERS S. , RUPRECHT. LUTZ , UNSOLD EBERHARD
Published: July 2006

Safety and efficacy of mapping guided laser catheter ablation of the AV junction was tested in a canine model. A total of 43 laser pulses (continuous wave, Nd:YAG, 1,064 nm, 30 W, irradiated spot diameter 2.0–2.5 mm) were delivered in 15 dogs (2–5 per dog) via a novel laser catheter system. Pulses were selectively aimed at: (1) the AV node: (2) the His bundle; and (3) the bundle branches. Laser pulses of 9.7 ± 1.1 seconds (n = 31) produced reversible conduction disturbances in the targeted segment of the AV conduction system, while pulses of 28.6 ± 7.9 seconds (n = 9) resulted in chronic block. The dogs survived the procedure without complications. Follow‐up was 6.5–10.5 months. Histopathologically, lesions showed clear‐cut oval‐shaped areas of fibrosis of 0.5–18.0 mm in diameter and 0.5–3.5 mm (transmural) in depth, depending on the irradiation time. Pervenous mapping guided laser catheter irradiation of the AV junction can produce AV block consistently and selectively in the targeted segment of the right ventricular conduction system in dogs. The method is safe and can be performed in a controllable manner by using the catheter system presented.