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Carsten W Israel

Publications and source records attributed to Carsten W Israel.

36 records · Page 2Linked to original sources
PubMed2005

Apropos "tachycardia begets tachycardia".

It has been shown that a tachycardia can facilitate the induction of the same ("atrial fibrillation begets atrial fibrillation") or a different tachycardia. This may also apply for pacemaker-mediated tachycardia as the present case documents.

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PubMed2005

Prevention of sudden cardiac death: lessons from recent controlled trials.

Sudden cardiac death (SCD), presumably because of ventricular tachyarrhythmias, remains one of the major challenges of contemporary cardiology. Major randomized controlled trials conducted in patients with coronary artery disease (CAD) with the aim of primary prevention of SCD are providing insights. Several large-scale studies have demonstrated that treatment with beta-blockers, angiotensin-converting enzyme inhibitors, aldosterone antagonists, and statins results not only in a reduction in all-cause mortality but specifically also in SCD. On top of this optimized pharmacological therapy, implantable cardioverter-defibrillators (ICD) further decrease the risk of overall and SCD mortality in carefully selected patient groups. The sum of these trials indicates, however, that the benefit associated with ICD therapy is most prominent in patients with chronic stable CAD. In contrast, patients early after myocardial infarction derive less benefit from ICD treatment, presumably because of a high competing risk of non-arrhythmic cardiovascular death. Optimized pharmacological therapy, together with the ICD, can substantially improve the prognosis of high-risk CAD patients.

Coronary Artery Disease↗
PubMed2004

Long-term risk of recurrent atrial fibrillation as documented by an implantable monitoring device: implications for optimal patient care.

OBJECTIVES: The present study determined the incidence and time course of atrial fibrillation (AF) recurrences in patients with a history of AF and fitted with an implantable monitoring device. BACKGROUND: The long-term risk of undetected recurrence of AF in patients receiving stable antiarrhythmic therapy remains uncertain. METHODS: In 110 patients with a class I indication for physiologic pacing and a history of AF, a pacemaker with dedicated functions for AF detection and electrogram storage was implanted, and antiarrhythmic drug treatment was optimized. Patients were regularly followed up with evaluation of AF-related symptoms, a resting electrocardiogram (ECG), and interrogation of device memory. The incidence of AF recurrences lasting >48 h in asymptomatic patients presenting in sinus rhythm (SR) at the respective follow-up visit constituted the primary end point of this prospective study. RESULTS: During 19 +/- 11 months, 678 follow-up visits were performed. Atrial fibrillation was documented in 51 patients (46%) by ECG recording and in 97 patients (88%) by a review of stored electrograms (p < 0.0001). Device interrogation revealed AF recurrences lasting >48 h in 50 patients, 19 of whom (38%) were completely asymptomatic and in SR at subsequent follow-up. In 11 (16%) of 67 patients with device-confirmed freedom from AF for > or =3 months, AF lasting >48 h recurred subsequently. CONCLUSIONS: This prospective study demonstrates a high incidence of recurrent AF despite optimized antiarrhythmic therapy. Of particular note, AF relapses >48 h remained totally asymptomatic in a significant proportion of patients. Freedom from AF for > or =3 months did not preclude subsequent long-lasting AF recurrence.

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PubMed2003

Thromboembolic risk of patients referred for radiofrequency catheter ablation of typical atrial flutter without prior appropriate anticoagulation therapy.

BACKGROUND: Radiofrequency catheter ablation of isthmus dependent atrial flutter is considered the therapy of choice. There is, however, controversy with regard to the thrombogenicity of atrial flutter in comparison with atrial fibrillation. METHODS: Consecutive patients scheduled for catheter ablation of documented typical atrial flutter receiving insufficient (INR < 2.0) or no anticoagulation during the three weeks preceding the procedure underwent multiplane transesophageal echocardiography (TEE). Patients with exclusive documentation of atrial flutter were classified as group I, whereas patients with additional documentation of atrial fibrillation were classified as group II. RESULTS: The study included 201 patients, 62 of whom were not on therapeutic anticoagulation (mean age 64 +/- 9 years, 87% men). In 10 of these 62 patients (16%), TEE detected a left atrial (LA) appendage thrombus in 4, or dense spontaneous echo contrast (SEC) in 6 patients. Comparison of patients with versus without SEC or thrombus, revealed a higher incidence of valvular heart disease (60% vs 26%, P = 0.05), but no differences with respect to age, gender, LA diameter, left ventricular end-diastolic diameter, or left ventricular ejection fraction. The incidence of positive TEE findings in group I was 1 in of 36 versus 9 of 26 in group II (3% vs 35%, P < 0.001), and the relative risk for thromboembolism in group II versus group I was 12.5 (95% CI: 3-55, P < 0.001). CONCLUSION: There is a significant risk for thromboembolism in patients referred for ablation of typical atrial flutter who have not been appropriately anticoagulated.

Anticoagulants↗
PubMed2003

Immediate reinitiation of atrial tachyarrhythmias after spontaneous restoration of sinus rhythm in patients with an implanted monitoring device.

Immediate reinitiation of atrial tachyarrhythmia (IRAT) has been observed after cardioversion. After spontaneous restoration of sinus rhythm (SR), incidence and characteristics of IRAT have not been described. Therefore, in patients with atrial tachyarrhythmias (ATs) and bradycardia, a pacemaker with dedicated memory functions was implanted. Devices were interrogated after 1 month and stored episodes of AT were analyzed: incidence of IRAT, duration and rate of the preceding episode, sinus rate before AT, coupling interval of atrial premature beats (APBs) initiating AT, and incidence of repetitive APBs. A potential association with IRAT was assessed for clinical characteristics. In 36 of 68 patients, stored electrograms confirmed correct detection of AT onset and termination in 545 episodes. IRAT was present in 212 (39%, 24 patients) episodes of AT. Episodes of AT preceding IRAT were longer than those before non-IRAT (156 vs 46 s, P < 0.001), and occurred during a higher atrial rate before onset of AT (cycle length 775 +/- 111 vs 856 +/- 133 ms, P < 0.001). The coupling interval of APBs initiating IRAT was shorter (502 +/- 83 vs 538 +/- 89 ms; P < 0.001) while the percentage of episodes with repetitive APBs before AT onset and the median atrial cycle length of the preceding AT were not different. On stepwise logistic regression analysis, none of the clinical factors evaluated independently predicted IRAT. In conclusion, IRAT is frequent after spontaneous restoration of SR. Changes of atrial electrophysiological properties promoting IRAT may already develop during AT of short duration.

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PubMed2003

Pacing to prevent atrial fibrillation.

INTRODUCTION: Pacing has been proposed as a nonpharmacologic treatment option to prevent atrial tachyarrhythmias (ATs) in drug-refractory patients. This article reviews the current state of pacing to prevent ATs. METHODS AND RESULTS: Different pacing modalities have been assessed with regard to their ability to prevent AT: conventional DDDR pacing with elevated lower rate limit, biatrial pacing, dual-site right atrial pacing, atrial septal pacing, and pacing with the use of dedicated pacing algorithms. Small studies suggest a benefit of conventional pacing for AT prevention in patients with bradycardia, but a randomized trial did not reveal any AT reduction by conventional pacing in patients without bradycardia. AT prevention by biatrial or dual-site right atrial pacing has been reported in small studies, but randomized trials did not show a clear benefit of these pacing techniques. Small studies showed a reduced AT recurrence rate in patients with septal pacing at the triangle of Koch or at Bachmann's bundle. Two large randomized trials with preventive pacing algorithms showed a significant AT reduction compared to conventional pacing, but this was not confirmed in four trials. CONCLUSION: Pacing seems to be able to suppress ATs in a minority of patients; however, prospective identification of responders to different pacing modalities does not appear to be feasible at the present time.

Algorithms↗
PubMed2003

Prevention of immediate reinitiation of atrial tachyarrhythmias by high-rate overdrive pacing: results from a prospective randomized trial.

INTRODUCTION: Immediate reinitiation of atrial tachyarrhythmia (IRAT) is an important cause of failure to maintain sinus rhythm. IRAT prevention by overdrive pacing has not been evaluated in a prospective randomized trial. METHODS AND RESULTS: Patients with a DDDRP pacemaker offering temporary atrial overdrive pacing after AT termination (Post Mode Switching Overdrive Pacing [PMOP]) were enrolled into the prospective PIRAT (Prevention of IRAT) trial if paroxysmal AT episodes occurred after implantation. PMOP was randomly activated (120 beats/min for 2 min) or inactive. After 3 months, device memory was interrogated, symptoms and quality of life assessed, and patients crossed over to the alternative treatment arm for another 3 months. Primary study endpoint was the number of AT episodes; secondary endpoints were the cumulative time in AT (AT burden), percentage of AT episodes with IRAT, symptoms, and quality of life with PMOP active versus inactive. In 37 patients (21 men; 69 +/- 9 years), there was no difference in the median number of AT episodes (0.37 vs 0.34 per day), AT burden (both 1%), percentage of episodes with IRAT (30%vs 28%), symptoms, and quality of life during PMOP off versus on. With PMOP active, 29% of 439 ATs restarted during and 18% before PMOP intervention. The PMOP-induced rate increase appeared to be associated with IRAT in 9% of AT episodes. CONCLUSION: Automatic overdrive pacing after AT termination did not prevent IRAT, mainly due to insufficient overdrive suppression even at 120 beats/min and the delay between AT termination and PMOP intervention.

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PubMed2002

Analysis of mode switching algorithms in dual chamber pacemakers.

Dual chamber systems are currently implanted in an increasing number of patients with a pacing indication and paroxysmal atrial tachyarrhythmias (ATAs). To avoid tracking of high atrial rates during ATA while providing AV synchronous pacing during sinus rhythm and AV block, automatic mode switching (MS) to a nontracking mode has been developed. Several concepts of MS algorithms have been introduced differing in sensitivity and specificity of ATA detection, delay between ATA onset and MS, pacing mode during MS, rapidity of MS termination upon detection of sinus rhythm, and special algorithms pertinent to MS. This review classifies and analyzes algorithms that are integrated into MS concepts and outlines considerations on optimal MS performance. Based on simulations and clinical studies, fast MS concepts avoiding high paced ventricular rates seem preferable but require special functions to avoid loss of AV synchrony by inappropriate MS. Similarly, fast return to tracking mode after ATA cessation seems preferable but requires algorithms to prevent mode oscillations. Sudden ventricular rate changes have to be avoided by rate smoothing functions, and an appropriate ventricular rate during nontracking mode has to be provided by rate responsive pacing. Programming of the device includes individual optimization of atrial sensitivity, atrial blanking times, and tachycardia detection rates. In addition, a high signal-to-noise ratio by careful atrial lead implantation, narrowly spaced bipolar atrial leads and a good sensing amplifier, together with special algorithms for atrial sensing adjustment improve the performance of MS algorithms.

Algorithms↗
PubMed2002

Failure of atrial flutter detection by a pacemaker with a dedicated atrial flutter detection algorithm.

Detection of atrial flutter may be difficult for pacemakers with automatic mode switching algorithms. The Medtronic Kappa 700 device pacemakerfamily offers a dedicated Blanked Flutter Search algorithm specifically designed for the detection of atrial flutter. This report describes how spontaneous atrioventricular conduction, resulting in a sensed QRS complex at a critical time, inhibited the function of the Blanked Flutter Search algorithm to sense "concealed" or "blanked" atrialflutter. This observation underscores the need for further refinement of pacemaker algorithms for the detection of atrial tachyarrhythmias.

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PubMed2002

Usefulness of atrial pacing for prevention and termination of atrial tachyarrhythmias in a patient with persistent atrial fibrillation.

Atrial pacing with dedicated algorithms for prevention and termination of atrial tachyarrhythmias is under clinical evaluation. A patient is described with persistent symptomatic AF. After cardioversion and implantation of a DDDRP pacemaker before planned AVN ablation, the patient was free of symptoms. Early after implant, one cardioversion of AF was necessary. Over the course of 12 months, only five episodes of atrial tachyarrhythmia occurred, all automatically pace terminated within 24 hours. Thus, selected patients with persistent AF may benefit from preventive atrial pacing since the tachyarrhythmia can organize intermittently to a degree sufficient for pace termination.

Atrial Fibrillation↗
PubMed2002

Ventricular rate stabilization for the prevention of pause dependent ventricular tachyarrhythmias: results from a prospective study in 309 ICD recipients.

Reviews of stored electrograms from ICDs revealed a 5-30% incidence of short-long-short intervals preceding the onset of recurrent ventricular tachyarrhythmias. Rate stabilization by dedicated antibradycardia pacing algorithms has, therefore, been suggested to prevent onset of pause dependent tachyarrhythmias. However, the clinical efficacy of this approach has not been studied systematically. In a prospective multicenter crossover study, patients were randomized to activation or deactivation of an implemented ventricular rate stabilization algorithm (VRS) after first implant of a dual chamber ICD. After 3 months, all patients were crossed over to the alternate programming. The rate of appropriate spontaneous VA episodes was compared between VRS On and VRS Off. Stored electrograms were reviewed for evaluation of the mode of onset of tachyarrhythmias. Overall efficacy analysis was based on 309 patients enrolled in the study. Forty percent (124/309) of the patients experienced 4,973 VA episodes. Based on an intention-to-treat analysis, VRS Off and On arrhythmia incidence was 10.2 and 6.6 normalized to 3 months, respectively (risk reduction 35%; P = 0.18) On an on-treatment basis, a reduction from 9.0 episodes to 8.1 episodes (10% risk reduction, P = 0.24) was seen. In an extended Cox model adjusting for confounding variables, the relative risk for recurrent episodes was 0.92 during VRS On compared to Off (95% CI: 0.58-1.48; P = 0.74). During VRS Off, pause dependent onset was documented in only 36 (8%) of 427 visually analyzed episodes. There was no significant reduction in the incidence of recurrent ventricular tachyarrhythmias with VRS On compared to the Off programming in this prospective study.

Algorithms↗
PubMed2002

Suppression of atrial tachyarrhythmias by pacing.

INTRODUCTION: Treatment of atrial tachyarrhythmias (ATs) remains difficult in many patients. Accordingly, new therapeutic approaches for AT suppression are evaluated. Atrial pacing may prevent ATs by modifying the electrophysiologic conditions required for sustained ATs. METHODS AND RESULTS: New pacing algorithms for prevention of AT are aimed at permanent overdrive suppression of arrhythmic activity, reduction of dispersion of atrial refractoriness produced by short-long cycles, more aggressive overdrive pacing after spontaneous sinus conversion to prevent early reinitiation of ATs, and prevention of inadequate rate decay in patients with vagally induced ATs. AT prevention may be achieved by dedicated atrial pacing sites, e.g., pacing at the insertion of Bachmann's bundle or biatrial pacing, which compensates for interatrial conduction delay. Preexciting regions of critical conduction delay, pacing at the triangle of Koch or coronary sinus os, and dual-site right atrial pacing have shown antiarrhythmic effects. Atrial preventive pacing and pharmacologic treatment may work synergistically in the concept of hybrid therapy. To prevent atrial electrical remodeling, early termination of AT seems desirable. This may be achieved by implanted devices that automatically detect ATs and provide atrial antitachycardia pacing for organized ATs. Initial studies showed that regular AT can automatically be terminated in approximately 50% of treated episodes. CONCLUSION: Pacing for prevention of AT and termination of organized AT episodes may become important steps within the concept of hybrid therapy of AT. However, their clinical efficacy and optimal patient selection remain to be evaluated in prospective, well-designed clinical trials.

Algorithms↗