bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of Atrial Sensed Far‐Field Ventricnlar Signals: A Reassessment
Authors: BROUWER JAN , NAGELKERKE DICK , den HEIJER PETER , RUITER JAAP H. , MULDER HENK , BEGEMANN MALCOLM J.S. , LIE KONG I.
Published: July 2006

Accurate detection of the spontaneous far‐field ventricular signal may be used to determine the ventricular activation, and hence, the interval from atrial stimulus to the ventricular R wave (AR interval) using a standard atrial pacing lead. This can be useful in developing a physiological atrial rate responsive (AAIR) pacemaker and in further improving DDD(R) pacing algorithms. In order to better characterize the atrial sensed far‐field ventricular signal, 200 consecutive patients undergoing pacemaker implantation were studied. The amplitude of the far‐field ventricular signal was significantly smaller than that of the atrial deflection. In all recordings, the slew rate of the atrial deflection was larger than that of the far‐field ventricular signal. Subdivision of the recordings by electrode position, pocket location, or QRS duration on the surface ECG resulted in significantly different signal characteristics. The amplitude and slew rate of the far‐field ventricular signal were significantly smaller in bipolar versus unipolar sensing. Atrial sensed far‐field ventricular recordings could also be obtained in the case of ventricular pacing. Our results indicate that accurate sensing of the far‐field ventricular signal from an atrial pacing lead is conceivable in most patients. The different signal characteristics in relation to parameters, such as electrode position, sensing mode, and pocket location, may be useful in determining the optimal conditions for signal sensing.
Right Ventricular Disarticulation Procedures: The Role of Late Potentials in the Genesis of Postoperative Ventricular Arrhythmias
Authors: DOIG J. COLIN , NICHOL IAN E. , McCOMB JANET M. , FURNISS STEPHEN S. , HILTON COLIN J. , BOURKE JOHN P. , CAMPBELL RONALD W.F.
Published: July 2006

Arrhythwogenic right ventricular disease may be associated with life‐threatening and drug refractory ventricular arrhythmias. Right ventricular disarticulation procedures are effective antiarrhythmic surgical approaches in selected patients. This study examined the role of late potentials in the postoperative development of new ventricular arrhythmias, and showed that right ventricular isolation is effective, probably because it destroys the tissue giving rise to late potentials. Total disarliculation is associated with fewer postoperative arrhythmias than partial isolation procedures. Total disarticulation may be the surgical approach of choice in such patients.
Electrophysiological Effects of E 4031, a Drug with Selective Class III Properties, in Man
Authors: KATRITSIS DEMOSTHENES , MORGAN JOHN , BRACHMANN JOHANNES , BYGRAVE ANGELA , O'EARRELL DYMPNA , ROWLAND EDWARD , GAMM A. JOHN
Published: July 2006

We studied the electrophysiological effects ofE 4037, given in a dose ascending manner (1.5, 3.0, and 6.0 μg/kg over 5 min followed by 0.1, 0.2, and 0.4 μg/kg per min for 60 min, respectively) to 19 volunteers. There were significant, dose related linear increases in QT and QTC intervals, in atrial functional and effective refractory periods (ERPs) at a paced cycle length of 400 ms, and in ventricular functional and ERPs at a paced cycle length of 600 ms. There was no significant change in the AH and HV intervals or QRS duration. No significant proarrhythmic or other side effects were encountered during the administration of the drug. E 4031 prolongs atrial and ventricular refractoriness without significantly affecting AV or intraventricular conduction, consistent with selective Class III properties. At the doses used in the present study, intravenous infusion of E 4031 appears to be safe and well tolerated.
Successful Radiofrequency Catheter Ablation of Automatic Atrial Tachycardia with Regression of the Cardiomyopathy Picture
Authors: CHILADAKIS JOHN A. , VASSILIKOS VASSILIS P. , MAOUNIS THEMISTOCLIS N. , COKKINOS DENNIS V. , MANOLIS ANTONIS S.
Published: July 2006

Ectopic atrial tachycardia (EAT) is often refractory to pharmacological suppression, and if uncontrolled, it can lead to cardiomyopathy. Although RF current catheter ablation therapy has been effective in eliminating the arrhythmia, there is limited information. particularly in adult patients with regard to the reversal of the tachycardia induced cardiomyopathy. Four adult patients, 20–56 years of age, and a 6‐year‐old boy, were referred with refractory EAT. Four patients had heart failure and three had depressed LV function by echocardiographic criteria. AH patients underwent electrophysiological study, and RF ablation was successful in abolishing the arrhythmogenic foci. Of these, four were located in the right atrium and one in the left atrium, and were identified by recording of the earliest atrial activation. No complications occurred. Termination of the EAT resulted in symptomatic improvement. Serial echocardiographic assessment of LV function indicated a significant reversal of the cardiomyopathy picture with reduction in chamber size and recovery in systolic function; indices of diastolic dysfunction persisted in one patient. Chronic, uncontrolled EAT can cause tachycardia induced cardiomyopathy. The picture of the cardiomyopathy resolves after elimination of the focus. RF ablation is both effective and safe, and may be considered as early therapy, particularly in patients with incessant EAT and ventricular dysfunction.
Management of Distal Electrode Detachment During Lead Extraction
Authors: KUTALEK STEVEN P. , PACE JOSEPH N. , KUSSMAUL WILLIAM
Published: July 2006

A Telectronics 330–801 atrial active fixation lead with multiple J retention wire fractures was extracted. Separation of the distal electrode occurred due to antecedent inner conductor fracture between the endocardial electrode pair. Techniques for removal of the free distal electrode are described, including use of biopsy forceps and a snare.
Limitations of the Algorithm to Reconfirm Ventricular Fibrillation in a Third‐Generation Implantahle Cardioverter Defibrillator
Authors: MATTKE SÖREN , KRAMM BERTHOLD
Published: July 2006

We report on inadequate shocks delivered by an ICD for VT converting spontaneously to AF with slow ventricular response. This represents a correct behavior of the reconfirmation algorithm, as the detection of intervals longer than the fibrillation detection interval and shorter than the bradycardia escape interval is required to inhibit the shock.
Complete Heart Block in the Setting of Mitochondrial Cytopathy: Implantation of a Permanent Pacemaker in a 6‐Year‐Old Boy
Authors: GREKAS GEORGE F. , PAPPAS SPYROS D. , ARGIRI OURANIA A. , SIOGAS KONSTANTINOS G. , HATZIOANNIDIS VASSILIOS G. , SIDERIS DEMETRIOS A.
Published: July 2006

The case of a 6‐year‐old boy with cytochrome oxidase (complex IV) deficiency and complete heart block, treated with permanent pacemaker implantation, is reported.
Syncope Due to Advanced Atrioventricular Block Despite No Demonstrable Cardiac Disease
Authors: KOSINSKI DANIEL , GRUBB BLAIR P.
Published: July 2006

Cardiovascular syncope can be due to a variety of abnormalities. Often, multiple testing modalities are necessary to obtain an accurate diagnosis. We report on a young female patient with recurrent syncope in whom conventional evaluation was unremarkable. A diagnosis was established by prolonged ambulatory monitoring.
Ventriculoatrial Conduction Capability and Prevalence of 1:1 Retrograde Conduction During Inducible Sustained Monomorphic Ventricular Tacbycardia in 305 Implantable Cardioverter Defibrillator Recipients
Authors: MILITIANU ARIE , SALACATA ABRAHAM , MEISSNER MARC D. , GRILL CATHERINE , MAHMUD REHAN , PALTI AMOS J. , BEN DAVID JOSEPH , MOSTELLER ROBERT , LESSMEIER TIMOTHY J. , BAGA JOHN J. , PIRES LUIS A. , SCHUGER CLAUDIO D. , STEINMAN RUSSELL T. , LEHMANN MICHAEL H.
Published: July 2006

Retrograde Conduction During Inducible Sustained Monomorphic Ventricular Tachycardia in 305 Implantable Cardioverter Defibrillator Recipients. Despite the advent of dual chamber ICDs, differentiation of VT (SMVT) with 1:1 VA conduction will remain a challenge. In this study, VA conduction capability and prevalence of inducible sustained monomorphic (SM) VT with 1:1 VA conduction was assessed in 305 ICD recipients. SMVT with a mean cycle length (CL) of 304 ± 61 ms was induced in 161 (53%) patients. Twenty‐six percent of the patients maintained 1:1 VA conduction to CL ≤ 400 ms during incremental ventricular pacing, regardless of presenting tachyarrhythmia or presence of inducible SMVT. Among ten patients who had inducible SMVT with possible 1:1 VA conduction (based on SMVT CL comparable to the shortest CL associated with 1:1 retrograde conduction during ventricular pacing), all seven with available intracardiac tracings had documented 1 :1 VA conduction during the induced SMVT—representing 4.4% of the patients with inducible SMVT (95% CI 1.2%‐7.6%), and 2.3% of the entire ICD cohort (95% CI 0.6%‐4.0%). We conclude that about one‐fifth of ICD recipients possess 1:1 VA conduction to CL ≤ 400 ms and that inducible SMVT with 1:1 VA conduction can be demonstrated in a small hut nonnegligible proportion of ICD recipients. These data are relevant to the design of tachyarrhythmia‐discrimination algorithms for dual chamber ICDs.
Do Permanent Pacemakers Need an Insulative Coating? Results of a Prospective Randomized Double‐Blind Study
Authors: DAVIES TED , DORIAN PAUL , YAO JAMES , HART JOHN , NEWMAN DAVID
Published: July 2006

During conventional manufacturing of implanted pulse generators (IPGs), an insulative coating is often applied to prevent local muscle stimulation and myopotential sensing in unipolar pacing. This can limit the orientation of the IPG into its pocket, be a potential source of muscle stimulation via coating scratches, and result in an increase in IPG production costs. We hypothesized that advances in the design and construction of current IPCs and leads obviates the need for an insulative coating of the IPG. Using a double‐blind prospective randomized design, 39 patients were implanted with either coated or uncoated otherwise identical IPGs (19 dual, 20 single chamber). All testing was done in unipolar and bipolar mode in both channels. A strength‐duration curve for muscle stimulation was constructed for all patients with muscle stimulation. Myopotential sensing was established during isometric exercise. At 6‐month follow‐up when tested in unipolar mode, 3 of 15 (20%) patients with coated IPCs and 3 of 20 (15%) with uncoated IPCs had muscle stimulation at 5.0 V/ 1.5 ms or lower (P = NS). No patients in either population had muscle stimulation at their normally programmed output. Myopotential sensing occurred in all patients in unipolar mode at a mean of 2.29 ± 1.3 mV and 2.73 ± 1.14 mV for coated versus uncoated, respectively (P = NS). The statistical power of these negative observations was 80%. An insulative coating for pacemakers does not appear to alter sensing performance or cause a significant difference in the occurrence or characteristics of muscle stimulation.
Is Dispersion of Ventricular Repolarization Rate Dependent?
Authors: ZABEL MARKUS , WOOSLEY RAYMOND L. , FRANZ MICHAEL R.
Published: July 2006

QT dispersion has been adopted as a new index for the noninvasive assessment of the inhomogeneity of repolarization and has been evaluated in several clinical studies as an index of arrhythmia propensity. In most of these studies, indices of dispersion of repolarization were rate corrected by the Bazett formula calculating QT dispersion as QTcmax‐QTcmin or JT dispersion as fTcmax‐fTcmin, implying that dispersion of repolarization also changes with heart rate. This study aimed to determine in the electrically paced isolated heart whether dispersion of ventricular repolarization is rate dependent. Multiple (5–7) monophasic action potentials (MAPs) were recorded simultaneously from the epicardium and endocardium of both ventricles in 18 isolated Langendorff‐perfused rabbit hearts. Hearts were paced from a right ventricular site at basic cycle lengths (CL) between 1,200 and 300 ms in 100‐ms decrements. Action potential duration was measured at 90% repolarization (APD90), and recovery time (RT) was defined as the sum of APD90 and activation time in each of the simultaneous MAP recordings. The dispersion of APD90 ond RT, respectively, were calculated as the maximal difference among all recordings. APD90 and RT shortened continuously throughout the range of paced steady‐state CLs from 1,200 to 300 ms. APD90 was 197.6 ± 6.1 ms at a CL of 1,200 ms and decreased to 148.5 ± 2.5 ms at a CL of 300 ms (P < 0.0001). RT was 228.2 ± 6.2 ms at a CL of 1,000 ms and decreased to 175.9 ± 2.9 at a CL of 300 ms (P < 0.0001). In contrast, dispersion of APD90 and RT did not change significantly. Dispersion of APD90 was 24.8 ± 2.3 ms at a CL of 1,200 ms, 26.1 ± 1.9 msec at a CL of 1,000 ms, and 21.6 ± 2.1 at a CL of 300 ms (NS). Dispersion of RT was 29.7 ± 3.4 ms at a CL of 1,200 ms, 29.0 ± 3.0 ms at a CL of 1,000 ms, and 32.7 ± 3.2 ms at a CL of 300 ms (NS). In contrast to the duration of the QT interval, dispersion of ventricular repolarization does not change significantly with pacing induced changes in CL. Assuming that the rate‐dependent behavior of action potential duration is similar between the rabbit and human heart, a rate correction of parameters of dispersion of repolarization is probably unnecessary.
The Effect of Nonisodiametric Design on the Ease of Extracting Chronically Implanted Pacemaker Leads
Authors: PARSONNET VICTOR , HARARI DAVID
Published: July 2006

Extracting permanently implanted transvenous pacemaker leads is often difficult because a fibrous sheath tends to trap the lead at various points along its course. Because many leads have bulbous or nonisodiametric portions, extraction may be rendered even more troublesome, because it is difficult to pull the larger portion through the narrow areas of the sheath. Furthermore, forceful extraction may have dire consequences, such as cardiac laceration. A study was undertaken in animals to evaluate the effect of lead isodiametricity on lead extraction. The results show that any increase in the diameter of the lead tip greatly reduces the ease of its removal. Consequently, leads designed to be isodiametric tbroughout their entire lengths will greatly enhance their removability.
Hemodynamic Deterioration Following Radiofrequency Ablation of the Atrioventricular Conduction System
Authors: VANDERHEYDEN MARC , COETHALS MARC , ANCUERA IGNASI , NELLENS PAUL , ANDRIES ERIK , BRUGADA JOSEP , BRUGADA PEDRO
Published: July 2006

Radiofrequeucy ablation of the atrioventricular conduction system (ACS) has become an estoblished theTapy for patients with drug refroctory atrial fibrillation. We observed eight patients with hemodynamic deterioration ofteT radiofrequency oblotion of the otTioventTicular conduction system. As we found hemodynamic deterioration related to worsening mitral regurgitation, we compared the clinical history, eiectrophysiologicai, ond echocardiographic dato from the patients with hemodynamic deteriorotion and worsening mitral regurgitation (group 1) to those without hemodynamic deterioration and stable mitral regurgitation after the procedure (group 2). Eight out of 108 patients (7.4%) undergoing ablation of the ACS deteriorated hemodynamically with acute pulmonary edema in three and congestive heart failure in five patients occurring at a mean of 3 and 8 weeks, respectively, after the procedure. Three of these patients were referred for mitral valve surgery. Two patients underwent ablation using a left‐sided approach. A right‐sided approach was used in five patients. In one patient, a left‐ and right‐sided approach was used. Compared to group 2 patients, group 1 patients had significantly higher left ventricular end‐diastolic diameters (64 ± 6 mm vs 56 ± 9 mm) at baseline despite similar fractional shortening (32%± Il% vs 34%± 13%), left ventricular end‐systolic diameters (43 ± 9 mm vs36 ± 7 mm) and degree of mitral regurgitation (1.4 ± 1.1 vs 1.4 ±0.7) on echocardiographic analysis. Thus, hemodynamic deterioration together with progression of mitral regurgitation is a potential complication of ablation of the ACS (up to 7.4%). Patients with high left ventricular end‐diastolic diameters ond moderate mitral regurgitation at baseline seem prone to this complication.
Internal Atrial Defibrillation: Effect on Sinus and Atrioventricular Nodal Function and Implanted Cardiac Pacemakers
Authors: PRAKASH ATUL , SAKSENA SANJEEV , MATHEW PHILIP , KROL RYSZARD B.
Published: July 2006

Internal atrial defibrillation (IAD) has been extensively evaluated for clinical efficacy but the need for concomitant demand pacing and the effect of IAD shocks on pacemaker function is not well studied. We prospectively evaluated: (l) the incidence of bradycardia as a result of IAD shocks; and (2) effect of these shocks on functioning of implanted cardiac pacemakers. Consecutive consenting patients with atrial fibrillation (AF) requiring cardioversion or undergoing electrophysiologi‐col study were selected for IAD. IAD shocks were delivered using the right ventricle to right atrium (RV‐RA), right ventricle to superior vena cava (RV‐SVC), right atrium to axillary patch (RA‐AX), and right atrium to left pulmonary artery or coronary sinus (RA‐LPA/CS) lead configurations. Mean RR interval before and after the shocks and the time interval from shock delivery to first QRS complex were analyzed for unsuccessful and successful shocks. Pacing and sensing function was analyzed in patients with previously implanted pacemakers. Twenty‐five patients, 18 men, mean age 67.9 ± 10 years were included in the study. A total of 305 shocks (264 unsuccessful, 41 successful) were analyzed. For unsuccessful shocks the mean post‐IAD shock RR interval (795 ± 205 ms) and the time to first post‐IAD shock QRS complex (970 ± 438 ms) were both significantly greater than the pre‐IAD shock RR interval (685 ±131 ms, P < 0.001). The increase in post‐IAD shock RB interval and time to first post‐IAD shock QRS complex was seen with all four lead configurations used. With successful shocks the mean post‐IAD shock sinus cycle length (1.105 ± 450 ms) and time to first post‐IAD shock QRS complex (1,126 ± 443 ms) were both also significantly greater than the pre‐IAD shock RR interval (766 ±172 ms). Nine patients (36%) had episodes of significant bradycardia after shock delivery. Shocks of up to 20 J using the RA‐LPA/CS lead configuration did not affect pacemaker function. IAD can result in transient bradycardia related to sinus and atrioventricular nodal effects requiring backup ventricular pacing. Shocks can be safely delivered using RA‐LPA or RA‐CS lead configurations in patients with implanted bipolar cardiac pacemakers.
Analysis of Electrophysiological Activity in Koch's Triangle Relevant to Ahlation of the Slow AV Nodal Pathway
Authors: HAÏSSAGUERRE MICHEL , JAÏS PIERRE , SHAH DIPEN C. , HOCINI MÉLÈZE , TAKAHASHI ATSUSHI , GAÏTA FIORENZO , BAROLD S. SERGE , CLEMÉNTY JACQUES
Published: July 2006

Atrioventricuiar junctional reentrant tachycardia (AVfBT) is the most common form of paroxysmal regular supraventricular tachycardia. In patients with disabling, drug refractory AVJBT, catheter ablation has evolved rapidly from a last‐resort treatment in the form of interruption of atrioventricular (AV) conduction to selective modification of AV nodal function as an ideal treatment. This article will focus on the frequently unappreciated electrophysiological activities recordable in man in Kach's triangle during ablation of the so‐called slow pathway.
A Left Free‐Wall, Decrementally Conducting, Atrioventricular (Mahaim) Fiber: Diagnosis at Electrophysiological Study and Radiofrequency Catheter Ablation Guided by Direct Recording of a Mahaim Potential
Authors: JOHNSON C. TIMOTHY , BROOKS CONNI , JARAMILLO JOSEPH , MICKELSEN STEVEN , KUSUMOTO FRED M.
Published: July 2006

A 64‐year‐old female with Wolff‐Parkinson‐White syndrome and an ECG demonstrating a rigbt posterolateral accessory pathway was referred for electrophysiological study. During electrophysiological testing two AV pathways were identified: a right posterolateral pathway that displayed conventional electrophysiological properties: and a left free‐wall pathway tbat conducted only anterogradely and demonstrated decremental properties. Two separate wide complex tachycardias were induced that utilized the left free‐wall pathway anterogradely and either the AV node or the right posterolateral accessory pathway retrogradely. A discrete electrical potential on the free wall of the mitral an‐nulus was identified during tachycardia and was utilized to facilitate mapping and ablation.
Use of an Atrial Loop to Extend the Duration of Endocardial Pacing in a Neonate
Authors: ROSENTHAL ERIC , BOSTOCK JULIAN
Published: July 2006

Use of an atrial loop has been proposed as a means of extending the longevity of endocardial pacing systems in small children who require ventricular pacing. A few reports have demonstrated the effectiveness of tbis method at reducing the number of interventions in infants and small children, but there is little reported experience in neonates. Permanent endocardial ventricular demand pacing was performed in a 3.4‐kg neonate. The generator was placed in a prepectoral pocket and a redundant loop of lead was left in the atrium to cater for further growth. At 32 months he weighs 13.6 kg and the loop bas uncoiled leaving additional lead slack for further growth.
Transient Data Stream Dissociation in Computerized Data Acquisition System Masquerading as a Sensing Abnormality
Authors: NAIR LAWRENCE A. , GREENFIELD RUTH ANN , YARGER MICHAEL , NIBLEY CARLETON , WHARTON J. MARCUS
Published: July 2006

During testing of a CPI model 1715 ICD, an apparent sensing abnormality was noted following shock delivery for VF. Close inspection of the recording prior to the defib‐rillation attempt revealed that the surface leads spontaneously lost 848 ms of data while the event marker was unaffected. Computer simulations revealed that an inadequate buffer size for the ampHfied (surface ECC) data was the likely source of data loss. It is important to recognize tbat a discordance between surface leads and event marker may represent an abnormality in tlie data acquisition system and simulate an ICD or lead malfunction.
Use of Left Ventricular Ejection Fraction or Wall‐Motion Score Index in Predicting Arrhythmic Death in Patients Following an Acute Myocardial Infarction
Authors: KØBER LARS , TORP‐PEDERSEN CHRISTIAN , ELMING HANNE ,   HANS BURCHARDT ON BEHALF OF THE TRACE STUDY GROUP
Published: July 2006

All‐cause mortality and morbidity following an acute myocardial infarction (AMI) are correlated to LV systolic dysfunction. The correlation is closest with mortality and morbidity associated with congestive heart failure (CHF). Prediction of arrhythmic death in patients with AMI relies on the correlation between arrhythmic death and “sudden unexpected death” defined as death within 1 hour of onset of new symptoms. Assessment of late potentials, heart rate variability (HRV), T wave alternans, arrhythmias seen on Holter monitoring or during exercise testing, electrophysiological testing, and baroreceptor assessment have all proven to be useful in the prediction of sudden death even when LV systolic function is known. In selected populations HRV is superior to LV systolic function assessment in predicting sudden death and/or arrhythmic events, and may even predict all‐cause mortality with the same precision. Comparisons of other methods with LV function assessment should be interpreted with care because most methods have been evaluated in subgroups of infarct patients with a low risk of death. Results from a large series of high risk patients with AMI (the TRAndolapril Cardiac Evaluation study) have shown that even in patients with severe depressed LV systolic function around one‐third of the patients will die suddenly. The current situation is that LV function appears to be the best method of predicting death whereas other methods appear very promising for detecting arrhythmic death in more selected populations. The optimal method for selecting patients at high risk of arrhythmic death has not yet been developed, but a combination of LV function and another method, i.e., HRV, appears promising. This may ensure that the enrolled patients have an increased risk of death and that this risk will be due to arrhythmic events. Patients with LVEF of 10% or less can be excluded as they will most likely not die suddenly.
Arrhythmia Risk: Eiectrophysiological Studies and Monophasic Action Potentials
Authors: WELLENS HEIN J.J. , DOEVENDANS PETER , SMEETS JOEP , RODRIGUEZ LUZ MARIA , DULK KAREL DEN DULK , TIMMERMANS CARL , VOS MARC
Published: July 2006

Shortly after in the introduction of progrommed electrical stimulotion (PES) of the heart to study and localize cardiac arrhythmias in the intact human heart, the technique was used for risk stratification of the arrhythmia patient. Two decades later we have to conclude that especially in ventricular arrhythmias the technique of PES did not live up to our expectations and the left ventricular function is a better long‐term predictor than the induction of ventricular arrhythmias or the ability to find an antiarrhythmic drug able to prevent the initiation of the classically documented ventricular arrhythmia. Another sobering finding come from the analysis of the characteristics of the patient dying suddenly out‐of‐hospital, which showed that most of those patients could not be classified before the event as being at high risk using noninvasive or invasive testing, not even in those with o previous cardiac history. Monomorphic action potential (MAP) recordings have been of importance in our understanding of torsade de pointe arrhythmias in congenital and acquired QT prolongation. A major problem in case of a less generalized electrophysiological abnormality is the identification of the appropriate place where to put the MAP‐electrode.
Prediction of Arrhythmia Risk Based on Signal‐Averaged ECG in Postinfarction Patients
Authors: BORGGREFE MARTIN , FETSCH THOMAS , MARTÍNEZ‐RUBIO ANTONI , MÄKIJÄRVI MARKKU , BREITHARDT GÜNTER
Published: July 2006

In patients surviving acute MI, identification of those at high risk for life‐threatening ventricular tachyarrhythmias and/or sudden death is of great importance. Numerous strategies based on indices such as the degree of left ventricular dysfunction, complex ventricular arrhythmias, or parameters of autonomic dysfunction have not yet led to an effective identification of the individual patient at risk. During the past decade, many investigators have recorded low amplitude, high frequency components in the terminal QRS complex (so‐called late potentials) from patients prone to sustained ventricular tachycardia. The SAECG has been used to predict life‐threatening tachyarrhythmias in patients after acute MI and to screen for inducible ventricular tachycardia in patients with unexplained syncope or sustained ventricular tachycardia. This review article describes the most frequently applied methodology and clinical applications of the SAECG in post‐MI patients and discusses the usefulness of noninvasive recordings in various other clinical settings.
Signal‐Averaged P Wave in Patients with Paroxysmal Atrial Fibrillation
Authors: ROSENHECK SHIMON
Published: July 2006

The theoretical and experimental rational of atrial signal‐averaged ECG in patients with AF is delay in the intra‐atrial and interatrial conduction. Similar to the ventricuiar signal‐averaged ECG, the atrial signai‐averaged ECG is an averaging of a high number of consecutive P waves that match the template created earlier. P wave triggering is preferred over QRS triggering because of more accurate aligning. However, the small amplitude of the atrial ECG and its gradual increase from the isoelectric line may create difficulties in defining the start point if P wave triggering is used. Studies using P wave triggering and those using QRS triggering demonstrate a prolonged P wave duration in patients with paroxysmal AE. The negative predictive value of this test is relatively high at 60%–80%. The positive predictive value of atrial signal‐averaged ECGs in predicting the risk of AF is considerably lower than the negative predictive value. All the data accumulated prospectively on the predictive value of P wave signal‐averaging was determined only in patients undergoing coronary bypass surgery or following MI; its value in other patients with paroxysmal AF is still not determined. The clinical role of frequency‐domain analysis (alone or added to time‐domain analysis) remains undefined. Because of this limited knowledge on the predictive value of P wave signal‐averaging, it is still not clinical medicine, and further research is needed before atrial signal‐averaged ECG will be part of clinical testing.
Present and Future Role of Ambulatory Holter Monitoring for Arrhythmia Risk Stratification
Authors: STEINBACH KONRAD , NÜRNBERG MICHAEL
Published: July 2006

Risk stratification for arrhythmogenic events and sudden death in patients with organic heart disease, particularly those with coronary heart disease and a history of MI, continues to be one of the major tasks of clinical cardiologists, although advanced management strategies including thrombolysis, acute PTCA and surgical intervention dramatically reduced the percentage of sudden deaths following acute MIs. Noninvasive studies like resting and exercise ECG, echocardiography, signal averaging, 24‐hour ECG, and radionuclide studies, as well as invasive techniques such as electrophysiologically programmed electrostimulation and coronary angiography, are being used routinely. Ambulatory Holter monitoring is an established noninvasive technique for risk stratification. There is evidence showing that its predictive potential for arrhythmogenic risks is enhanced, if more than one parameter is analyzed. Absence of ST segment changes and a normal HRVare the parameters singling out low‐risk patients. The use of additional parameters which escape electrocardiographic recording, like ventricular function and myocardial ischemia, improve the accuracy of predicting arrhythmogenic events. The most predictive combination of risk parameters is, however, still poorly understood. Future research should define normal ranges of parameters recordable by H‐ECG, solve technical problems of recording data and analyzing them. In addition, the accuracy of measuring QT duration and documenting late potentials should be improved by more sophisticated methods. But it is unrealistic to expect that the QT interval will become amenable to automatic analysis in all patients. A fully automatic QT analysis without visually checking the measuring points at the tip and the end of the T wave for their consistency is hardly conceivable. The documentation of late potentials, in turn, is limited by artefacts caused by muscle contraction during physical activity. Clinical aspects, e.g., the predictability of arrhythmogenic events in patients with cardiomyopathies and valvular disease, should be addressed. This will require studies combining the predictive potentials of rhythmologic and hemodynamic data.
Heart Rate Variability Used as an Arrhythmia Risk Stratifier After Myocardial Infarction
Authors: HOHNLOSER STEFAN H. , KLINGENHEBEN THOMAS , ZABEL MARKUS , LI YI GANG
Published: July 2006

Heart rate variability (HRV) is considered to represent a noninvasive tool to assess cardiac autonomic tone at the level of the sinus node. It has been shown to have predictive power for risk assessment in patients surviving acute myocardial infarction. For this purpose, HRV should be assessed from 24‐hour Holter recordings obtained 7–10 days following the infarction. Although there is some recovery of HRV during the first 3 months after infarction, HRV remains reduced in postinfarction patients compared to values obtained in healthy individuals. Compared to assessment of left ventricular function as a risk marker, HRV is superior with respect to prediction of arrhythmic events and sudden death whereas both parameters yield comparative power for prediction of total cardiac mortality. Since the predictive power of HRV analysis alone is relatively low, the combined use of HRV measurements together with traditional risk markers (such as ventricular ectopic beats, signal‐averaged ECG, or left ventricular function) results in improved risk prediction with positive predictive accuracy in the range of 30%–50%.
Baroreflex Sensitivity as a Cardiac and Arrhythmia Mortality Risk Stratifier
Authors: LA ROVERE MARIA TERESA , SCHWARTZ PETER J.
Published: July 2006

The last two decades have provided clear evidence for the tight and casual relation existing between arrhythmic mortality and the autonomic nervous system, particularly with imbalances characterized by decreases in vagal and/or increases in sympathetic activity. A series of compelling experimental results has represented the driving force for the clinical evaluation of the potential prognostic value of baroreflex sensitivity (BBS), a measure that can provide information on the capability to augment vagal activity. This article reviews the methodology more commonly used to quantify the clinical evaluation of this parameter, and then focuses on the key clinical studies highlighting those performed in postmyocardial infarction patients. Among them the most informative is ATRAMI, a multicenter prospective study involving almost 1300 patients. The main conclusion is that both heart rate variability and BRS are strong and independent risk factors for post‐infarction mortality, thus demonstrating the clinical usefulness of autonomic markers.
Changes in Repolarization Dynamicity and the Assessment of the Arrhythmic Risk
Authors: MAISON‐BLANCHE PIERRE , COUMEL PHILIPPE
Published: July 2006

At the present time, the assessment of the arrhythmic risk from surface ECG recordings is built on time‐domain and frequenct‐domain analysis of high resolution ECG acquisition together with in‐terlead variability of QT interval duration (QT dispersion). The corresponding raw ECG tracings are obtained in resting conditions. However, the dynamic aspects of the EGG signal is a rapidly evolving matter of interest. In addition to the beat‐to‐beat oscillations of the ventricular repolarization amplitude (QT ai‐ternans), there is growing evidence that the patterns of QT interval shortening with increasing heart rate are linked to suceptibility to ventricular arhythmias. In this report, we will mailnly address the association between QT dynamicity and the risk of developing torsades de pointes.
QT Interval Dispersion and its Clinical Utility
Authors: KAUTZNER JOSEF , MALIK MAREK
Published: July 2006

QT dispersion as a measure ofin‐terlead variations of QT interval duration in the surface 12‐lead ECG is believed to reflect regional differences in repolarization heterogeneity and thus, may provide an indirect marker of arrhythmogenicity. Methodology for determining QT dispersion and reproducibility of this parameter vary significantly between studies and, together with some other unresolved problems witb QT dispersion assessment, often lead to contradictory suggestions about potential clinical utility of this parameter. The results of our own study in 213 survivors of myocardial infarction, together with a comprehensive review of the literature, suggest that most of these inconsistencies reflect incomplete understanding of electrocardiographic correlates of both normal and abnormal ventricular repolarization. The application of more objective techniques, such as spectral analysis or combined assessment of different parameters (e.g., area beneath the T wave and its symmetricity) may add a new dimension to the noninvasive assessment of ventricular repolarization.
Holter, Loop Recorder, and Event Counter Capabilities of Implanted Devices
Authors: WAKTARE JOHAN E.P. , MALIK MAREK
Published: July 2006

The current generation of cardiac pacemakers and implantable cardioverter defibrillators almost all have some capabilites to store data regarding device activity and patient events for future retrieval. This information may provide valuable information regarding device function and whether this is proving valuable in patient management. Examples include “pace‐sense” counters, which can reveal under sensing of patient events, and serial lead impedance measurements, which are able to demonstrate trends not seen on isolated measurements. Holter capabilities become vital in more advanced devices for documenting the utility of, and fine tuning the programming of, features such as antitachycardia pacing, rate‐responsiveness, and mode‐switching. Finally, the ability to store patient events as marker channels and even intrac‐ardiac electrograms adds a diagnostic capability not available through external monitoring. This role has now been advanced by the development of a purely diagnostic implantable loop recorder.
Cardioversion of Atrial Fibrillation and Subsequent Maintenance of Sinus Rbythm
Authors: VAN GELDER ISABELLE C. , CRIJNS HARRY J.G.M.
Published: July 2006

This article gives an overview of electrical cardioversion of AF and includes the discussion of newer strategies. DC external cardioversion is highly effective and carries a low risk of complications. Other approaches, like transesophageal cardioversion and high energy internal cardioversion, may improve the acute success rate but do not enhance long‐term maintenance of sinus rhythm compared to external cardioversion. An atrial defibrillator may have important advantages which relate to the fact that the duration and possibly also the number of AF episodes become reduced. Supposedly, shortening the attacks of AF may exert an antiarrhythmic effect by limiting electrical, anatomical, and neurohumoral remodeling. So far. low energy biatrial defibrillation using an atrial defibrillator seems to be effective and safe (i.e., does not induce ventricular arrhythmias). However, discomfort limits its tolerability in clinical practice. Future improvement of leads and light sedation that is easy to administer may overcome this problem. In the second part of this overview, the probability of AF recurrence using a serial cardioversion approach is discussed. In middle‐aged patients with a fair exercise tolerance and an arrhythmia duration < than 36 months this approach may be worthwhile. Young patients (age < 57 years) with an arrhythmia duration < 3 months and without hypertension may be cured from the arrhythmia with a single shock and without the institution of antiarrhythmic drugs. However, the serial electrical cardioversion approach is unlikely to succeed in elderly patients with a duration of AF exceeding 36 months and a poor exercise tolerance (NYHA Functional Class III or IV).
Risk of Complications of Atrial Fibrillation
Authors: CAPUCCI ALESSANDRO , VILLANI GIOVANNI QUINTO , ASCHIERI DANIELA
Published: July 2006

Atrial fibrillation is associated with three major risk of complications: thromboembolism, hemodynamic compromise, and arrhythmogenesis. In patients with chronic atrial fibrillation the incidence of embolization is about 5% per year. The risk of embolism and in particular of stroke can be reduced by warfarine anticoagulation. Aspirin is generally less effective than warfarin, although it is probably more effective than placebo. The hemodynamic complications which may occur during atrial fibrillation are mainly due to the loss of effective atrial contraction, the irregular ventricular rhythm, and the possible excessively rapid ventricular rate. Sudden death is a recognized manifestation of Wolff‐Parkinson‐White syndrome and is considered to be precipitated by atrial fibrillation in the majority of patients. Torsades de pointes is perhaps the most widely recognized proarrhythmia associated with treatment of atrial fibrillation, especially with 1A antiarrhythmic drugs and sotalol. The chronic treatment with type 1C drugs in 3.5%–5% of patients may induce atrial flutter with 1:1 conduction with significant hemodynamic compromise.
Ventricular Arrhythmias in Apparently Healthy Subjects
Authors: JORDAENS LUC , TAVERNIER RENE , KAZMIERCZAK JAROSLAW , DIMMER CARLO
Published: July 2006

While it is assumed that the normal heart does not predispose to serious arrhyilimias, several conditions are now being recognized as being associated with short‐lasting ventricular arrhythmias. It also becomes clear that idiopathic VT (or repetitive monomorphic VT) sometimes exists on the background of a compromised heart. Whether this dysfunction is due to the arrhythmia or vice versa is not evident. Finally, VF occurs in patients who, at a first glance, have no apparent heart disease, and it is then called idiopathic VF. These complex electrical abnormalities probably reflect disorders, which often are genetically determined. Recognition of these syndromes, often characterized by abnormal repolarization or a disturbed autonomic function is possible if appropriate techniques are used.
Steroid‐Eluting Electrodes Prevent Chronic Pacing Threshold Rise in the Atrial Chamher After Oral Propafenone Administration
Authors: CORNACCHIA DANIELE , FABBRI MAURO , MARESTA ALEARDO , PUGLISI ANDREA , RICCI RENATO , AZZOLINI PAOLO , NIGRO PASQUALE , SORRENTINO FRANCESCO , SESTU PIERO , SANNA ANTONIO , VILLANI GIOVANNI QUINTO , DIECI GIOVANNI , CAPUCCI ALESSANDRO , DE SETA FRANCESCO
Published: July 2006

The aim of the study was to evaluate chronic atrial pacing threshold increase after oral propafenone therapy. Fifty patients affected by advanced AV block and sick sinus syndrome were studied at least 6 months after pacemaker implantation, before and after oral propafenone therapy (450–900 mg/day based on body weight). The patients were subdivided into three groups as to the type of electrode implanted, all three unipolar: group I (20 patients) Medtronic CapSure 4003, group II (13 patients) Medtronic Target Tip 4011, group III (17 patients) Medtronic 4057 screw‐in leads. In all cases, Medtronic unipolar pacemakers were implanted with the same noninvasive autothreshold measurement method. Propafenone and 5‐OH‐propafenone blood levels were measured 3–5 hours after drug administration. The pacing autothreshold was measured at 0.8, 1.6, and 2.5 V by reducing the pulse width. After propafenone. groups II and III showed a statistically significant threshold rise (P ranging from < 0.01 to <0.05), whereas no significant difference was found in group I. Propafenone and 5‐OH‐propafenone blood levels did not show any significant difference among the three groups. Strength‐durution curves were drawn for the three groups before und after propafenone: at baseline the curves shifted to the left with the steep part above the knee, clearly favoring CapSure over the other two groups. After propafenone, the curves shifted to the right, with the flat part progressively more evident in groups II and III. In the atrial chamber, steroid‐eluting leads prevented threshold increase after propafenone therapy, in contrast with a significant threshold rise with conventional porous and screw‐in leads.
Dual Chamber Pacing in Hypertrophic Obstructive Cardiomyopathy: Beneficial Effect of Atrioventricular Junction Ablation for Optimal Left Ventricular Capture and Filling
Authors: JEANRENAUD XAVIER , SCHLÄPFER JÜRG , FROMER MARTIN , AEBISCHER NICOLE , KAPPENBERGER LUKAS
Published: July 2006

Clinical improvement with dual chamber pacing bas largely been reported in patients suffering from hypertrophic obstructive cardiomyopathy and mainly attributed to the reduction of the subaortic pressure gradient. To be effective, pacing must induce a permanent and complete capture of the LV. In two patients of our collective, symptoms (angina and dyspnea NYHA Class III and/or syncopes) persisted or relapsed despite pacing. This was related to the inability to obtain full LV capture due to a too‐short native PR interval. RF ablation of the AV junction was therefore performed in botb patients, resulting in permanent AV block in one and prolonged PR interval up to 310 ms in the second. Pacing was thereafter associated with an immediate and significant clinical improvement related to permanent LV capture, whatever the patient's activity. After RF ablation, the AV delay was set up to induce the best LV filling, as assessed by Doppler analysis of mitral flow. Our observations suggest that RF ablation or modification of the AV junction can be a successful procedure in some patients with residual or recurrent symptoms, when the latter result from a loss of capture or from the inability to program an AV delay tbat does not compromise the active component to LV filling. Doppler echocardiography is a simple and effective mean to assess the hemodynamic effect of AV interval modulation in this setting.
Polarity Reversal Improves Defibrillation Efficacy in Patients Undergoing Transvenous Cardioverter Defibrillator Implantation with Biphasic Sbocks
Authors: SCHAUERTE PATRICK , STELLBRINK CHRISTOPH , SCHÖNDUBE FRIEDRICH A. , LÖSER HOLCER , HALTERN GEORG , MESSMER BRUNO J. , HANRATH PETER
Published: July 2006

The purpose of this study was to determine the influence of polarity reversal on DFT in patients undergoing implantation of nonthoracotomy defibrillators with biphasic shocks. Previous studies have shown higher defibrillation efficacy with using the distal electrode as anode in implantation of nonthoracotomy defibrillators and monophasic shocks. However, it is as yet unclear whether biphasic shock defibrillation will also be influenced by polarity reversal. Using a transvenous lead system with a proximal electrode in the superior caval vein and a distal electrode in the RV apex, 27 patients undergoing defibrillator implantation were randomized to DFT testing with “initial” (distal electrode = cathode) or “reversed” polarity (distal electrode = anode). Defibrillation energy was reduced stepwise until defibrillation failure occurred. At this point, polarity was switched and testing continued until the lowest energy requirement was determined for both polarities. With reversed polarity, DFT was 11.1 ± 5.7 J versus 13.3 ± 5.8 J with initial polarity (P = 0.033). This means a 17% reduction of the DFT. In 10 patients, the threshold was lower with reversed, whereas in 3 patients it was lower with initial polarity. In conclusion, changing electrode polarity in transvenous implantable defibrillators with biphasic shocks may significantly influence defibrillation energy requirements. Therefore, polarity reversal should always be attempted before considering patch implantation.
Adequacy of Pacing Rate During Exercise in Rate Responsive Ventricular Pacing
Authors: HASEGAWA AKIRA , HATORI MASAKO , AMANO MASAO , IIJIMA TOHRU , ADACHI HITOSHI , YAMAGUCHI ETSUO , FUKUDA TAKESATORU , MURATA KAZUHIKO , NAGAI RYOZO
Published: July 2006

Our objective was to determint; the adequate pacing rate during exercise in ventricular pacing by measuring exercise capacity, cardiac output, and sinus node activity. Eighteen patients with complete AV block and an implanted pacemaker underwent cardiopulmonary exercise tests under three randomized pacing rates: fixed rate pacing (VVJ) at 60 beats/min and ventricular rate‐responsive pacing (VVIR) programmed to attain a heart rate of about 110 beats/min ar 130 beats/min (VVIR 110 and VVIR 130, respectively) at the end of exercise. Compared with VVI and VVIR 130, VVIR 110 was associated with an increased peak oxygen uptake(VVIR 110:20.3 ± 4.5 vs VVI: 16.9 ± 3.1; P < 0.01; and VVIR 130: 19.0 ± 4.1 mL/min per kg, respectively; P < 0.05) and a higher oxygen uptake at anaerobic threshold (15.3 ± 2.7, 12.7 ± 1.9; P < 0.01, and 14.6 ± 2.6 mL/min per kg; P < 0.05). The atrial rate during exercise expressed as a percentage of the expected maximal heart rate was lower in VVIR 110 than in VVI or VVIR 130 (VVIR 110: 75.9%± 14.6% vs VVI: 90.6%± 12.8%; P < 0.01; VVIR 110 vs VVIR 130: 89.1%± 23.1%; P < 0.05). There was no significant difference in cardiac output at peak exercise between VVIR 110 and VVIR 130. We conclude that a pacing rate for submaximal exercise of 110 beats/min may be preferable to that of 130 beats/min in respect to exercise capacity and sympathetic nerve activity.