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Biomedical subjects

Kenneth A Ellenbogen

Publications and source records attributed to Kenneth A Ellenbogen.

At least 91 records · Page 5Linked to original sources
PubMed2003

Adverse effect of ventricular pacing on heart failure and atrial fibrillation among patients with normal baseline QRS duration in a clinical trial of pacemaker therapy for sinus node dysfunction.

BACKGROUND: Dual-chamber (DDDR) pacing preserves AV synchrony and may reduce heart failure (HF) and atrial fibrillation (AF) compared with ventricular (VVIR) pacing in sinus node dysfunction (SND). However, DDDR pacing often results in prolonged QRS durations (QRSd) as the result of right ventricular stimulation, and ventricular desynchronization may result. The effect of pacing-induced ventricular desynchronization in patients with normal baseline QRSd is unknown. METHODS AND RESULTS: Baseline QRSd was obtained from 12-lead ECGs before pacemaker implantation in MOST, a 2010-patient, 6-year, randomized trial of DDDR versus VVIR pacing in SND. Cumulative percent ventricular paced (Cum%VP) was determined from stored pacemaker data. Baseline QRSd <120 ms was observed in 1339 patients (707 DDDR, 632 VVIR). Cum%VP was greater in DDDR versus VVIR (90% versus 58%, P=0.001). Cox models demonstrated that the time-dependent covariate Cum%VP was a strong predictor of HF hospitalization in DDDR (hazard ratio [HR], 2.99 [95% CI, 1.15 to 7.75] for Cum%VP >40%) and VVIR (HR 2.56 [95% CI, 1.48 to 4.43] for Cum%VP >80%). The risk of AF increased linearly with Cum%VP from 0% to 85% in both groups (DDDR, HR 1.36 [95% CI, 1.09, 1.69]; VVIR, HR 1.21 [95% CI 1.02, 1.43], for each 25% increase in Cum%VP). Model results were unaffected by adjustment for known baseline predictors of HF hospitalization and AF. CONCLUSIONS: Ventricular desynchronization imposed by ventricular pacing even when AV synchrony is preserved increases the risk of HF hospitalization and AF in SND with normal baseline QRSd.

Aged↗
PubMed2003

Pacemaker therapy for prevention of syncope in patients with recurrent severe vasovagal syncope: Second Vasovagal Pacemaker Study (VPS II): a randomized trial.

CONTEXT: Three previous small randomized trials have reported that pacemaker therapy is beneficial for patients with severe recurrent vasovagal syncope. However, because these trials were not double blind, they may have been biased in their assessment of outcomes and had a placebo effect of surgery. OBJECTIVE: To determine if pacing therapy reduces the risk of syncope in patients with vasovagal syncope. DESIGN, SETTING, AND PATIENTS: A randomized double-blind trial of pacemaker therapy in outpatients referred to syncope specialists at 15 centers from September 1998 to April 2002. In the year prior to randomization, patients had had a median of 4 episodes of syncope. Patients were followed up for up to 6 months. INTERVENTION: After implantation of a dual chamber pacemaker, 100 patients were randomly assigned to receive dual-chamber pacing (DDD) with rate drop response or to have only sensing without pacing (ODO). MAIN OUTCOME MEASURE: Time to first recurrence of syncope. RESULTS: No patients were lost to follow-up. Of the 52 patients randomized to ODO, 22 (42%) had recurrent syncope within 6 months compared with 16 (33%) of 48 patients in the DDD group. The cumulative risk of syncope at 6 months was 40% (95% confidence interval [CI], 25%-52%) for the ODO group and 31% (95% CI, 17%-43%) for the DDD group. The relative risk reduction in time to syncope with DDD pacing was 30% (95% CI, -33% to 63%; 1-sided P =.14). Lead dislodgement or repositioning occurred in 7 patients. One patient had vein thrombosis, another had pericardial tamponade leading to removal of the pacemaker system, and a third had infection involving the pacemaker generator. CONCLUSIONS: In this double-blind randomized trial, pacing therapy did not reduce the risk of recurrent syncope in patients with vasovagal syncope. Because of the weak evidence of efficacy of pacemaker therapy and the risk of complications, pacemaker therapy should not be recommended as first-line therapy for patients with recurrent vasovagal syncope.

Adult↗
PubMed2003

Detection and management of an implantable cardioverter defibrillator lead failure: incidence and clinical implications.

OBJECTIVES: This study evaluated the long-term reliability of an implantable cardioverter defibrillator (ICD) lead to determine the incidence, clinical presentation, and management of lead failure. BACKGROUND: Despite recent advances in ICD technology, the long-term reliability of ICD leads remains a significant problem. METHODS: Concern about long-term reliability of coaxial polyurethane ICD leads caused us to systematically study all patients implanted with Medtronic (Minneapolis, Minnesota) 6936 lead at our institution. We performed follow-up of 74 patients with 76 ICD leads that were implanted from February 28, 1995 to September 8, 1997. Thirty-seven patients underwent routine clinical ICD follow-up testing and ventricular fibrillation induction to determine the status of their ICD lead after a mean follow-up of 68.6 +/- 8.2 months. RESULTS: The lead survival analysis shows a cumulative failure probability of 37% (confidence interval, 24% to 54%) at 68.6 months. Six patients demonstrated a previously undescribed mode of ICD lead failure: prolonged oversensing immediately after shock therapy. The use of short interval counters to monitor nonphysiologic R-R intervals and the measurement of ring-to-coil impedance detected early lead failures in five patients. CONCLUSIONS: This analysis shows: 1) problems with ICD leads may not become apparent until late during follow-up and may become a significant late problem, 2) a "signature" mode of lead failure for the 6936 consisting of oversensing of electrical noise following shocks, 3) early detection of lead failure with a short interval counter algorithm or measurement of ring-to-coil impedance may be clinically useful.

Aged↗
PubMed2003

Prospective randomized comparison of 65%/65% versus 42%/42% tilt biphasic waveform on defibrillation thresholds in humans.

BACKGROUND: The waveform tilt of biphasic shocks yielding the lowest defibrillation threshold (DFT) is not well defined. Some evidence indicates that tilts less than 65% may improve DFTs. METHODS: In 57 patients undergoing ICD implantation, DFTs were determined with truncated exponential biphasic waveform tilts at 65%/65% and at 42%/42%. An external defibrillator with custom software was used for testing. The effective capacitance of the defibrillator was 132-microF for both waveforms. DFTs were determined using a binary search method starting with 12 Joules (J). Patients were randomly assigned to initial testing with either one of the two tilts. Thirty patients (Group 1) were tested with a two electrode (active can to RV coil, or SVC coil to RV coil) and 27 patients (Group 2) were tested with a three electrode system (subcutaneous patch or active can + SVC coil to RV coil). RESULTS: Groups 1 and 2 did not differ in age, ejection fraction or antiarrhythmic medications. Group 1 delivered energy DFTs were 10.1 +/- 5.5 J with the 65%/65% tilt and 10.1 +/- 5.9 J for the 42%/42% tilt (p = 0.92). In group 2 the average DFT for the 65%/65% tilt was 8.4 +/- 5.7 J and for the 42%/42% tilt was 8.1 +/- 5.3 J (p = 0.70). There were no significant differences in DFTs for either group. The system impedance for Group 1 was 64 +/- 12 ohms and for Group 2 was 39 +/- 6 ohms (p < 0.0001). CONCLUSIONS: We found no differences in DFTs between 65%/65% tilt and 42%/42% tilt using either 2- or 3-electrode defibrillation systems. Further research is needed to optimize waveforms in order to minimize DFTs, which will result in smaller ICDs and/or greater safety margins for defibrillation.

Aged↗
PubMed2003

Post-pericardiotomy syndrome following linear left atrial radiofrequency ablation.

Post-pericardiotomy syndrome may occur after traumatic insults to the pericardium but has not been reported after radiofrequency catheter (RF) ablation. A 54 year old man underwent extensive linear left atrial RF ablation for chronic atrial fibrillation. Five days after the procedure the patient developed signs and symptoms of the post-pericardiotomy syndrome and showed new, intense pericardial inflammation on magnetic resonance imaging. After intensive medical management, the patient recovered fully. It is believed that the patient experienced a unique complication of linear left atrial ablation, i.e., post-pericardiotomy syndrome due to extensive left atrial necrosis or direct thermal pericardial injury.

Atrial Fibrillation↗
PubMed2003

Long-term outcome of patients after successful radiofrequency ablation for typical atrial flutter.

The aim of the study was to determine the long-term freedom from atrial arrhythmias after radiofrequency ablation of atrial flutter and to determine the factors associated with recurrent arrhythmias. Radiofrequency ablation has emerged as the preferred treatment for recurrent, typical atrial flutter. Although the short-term results after radiofrequency ablation of atrial flutter have been widely reported, there is insufficient data on long-term outcome with respect to the occurrence of atrial arrhythmias in patients after successful ablation. The first 108 patients to undergo successful ablation for typical atrial flutter at the authors' institutions were followed prospectively until the occurrence of typical atrial flutter, atrial fibrillation, atypical atrial flutter, or death. Several prespecified clinical and procedural factors were tested using univariate and multivariate analysis as predictors of arrhythmia recurrence. Patients were followed for a minimum of 3 years and a maximum of 8 years, or until the first arrhythmia recurrence (average duration 17 +/- 17 months). Recurrences of typical atrial flutter were usually observed within the first 6 months (73%, n = 16), with the remainder (27%, n = 6) occurring between 6 months and 2 years, and none were observed later. Freedom from recurrence of typical atrial flutter was 80% at 1 year (95% CIs 72-89%), 73% at 2 years (CIs 63-83%), and 73% at 5 years (CIs 63-83%). By contrast, freedom from occurrence of atrial fibrillation or atypical atrial flutter progressively declined over time; 80% at 1 year (CIs 71-88%), 59% at 2 years (CIs 48-70%), and 33% at 5 years (CIs 19-48%). A history of atrial fibrillation or atypical atrial flutter prior to ablation was associated with an increased risk of occurrence during follow-up (relative risk 3.4, CIs 1.5-8.1, P < 0.05). Freedom from occurrence of any atrial arrhythmia was only 27% at 5 years (CIs 15-40%). After successful ablation of typical atrial flutter, recurrence of typical flutter is relatively uncommon and usually occurs early. However, there is a progressive occurrence of atrial fibrillation and/or atypical flutter during follow-up so that many patients require further antiarrhythmic or additional ablative therapy. Radiofrequency ablation of typical atrial flutter should be considered a palliative procedure for most patients and only one component of the long-term care of the patient with atrial tachyarrhythmias.

Aged↗
PubMed2003

Predictors and clinical impact of atrial fibrillation after pacemaker implantation in elderly patients treated with dual chamber versus ventricular pacing.

The Pacemaker Selection in the Elderly (PASE) trial was a prospective, multicenter, single blind, randomized comparison of single chamber, rate adaptive, ventricular pacing (VVIR) with dual chamber, rate adaptive pacing (DDDR) in 407 patients aged > or =65 years(mean 76 +/- 7 years, 60% male)with standard bradycardia indications for dual chamber pacemaker implantation. The incidence, predictors, and clinical consequences of atrial fibrillation (AF) developing after pacemaker implantation in the PASE trial were studied prospectively. During a median follow-up of 18 months, AF developed in 73 (18%) patients. Kaplan-Meier estimated cumulative incidences of AF in patients with sinus node dysfunction (n=176) at 18 months were 28% in the VVIR and 16% in the DDDR groups (P=0.08). After adjustment for other clinical variables using a Cox multivariate regression model, randomization to VVIR compared with DDDR pacing mode among patients with sinus node dysfunction was independently associated with a 2.6-fold increased relative risk (RR) of developing AF after pacemaker implantation (P=0.01). Other independent clinical risk factors for development of postimplant AF included a preimplant history of hypertension (P=0.02) or supraventricular tachyarrhythmias(P<0.04). Patients who developed AF had similar health related quality of life scores and cardiovascular functional status after 18 months of pacing as patients who remained free of AF. The RR of death, stroke, or heart failure hospitalization was not increased in patients who developed AF. Thus, in the elderly patients with sinus node dysfunction requiring permanent pacing, DDDR pacing mode protected against the development of AF. However, development of AF after pacemaker implantation in this population was not associated with a significant impact on quality-of-life, functional status, or other clinical endpoints during 18 months of follow-up.

Aged↗
PubMed2002

Cerebral blood flow velocity declines before arterial pressure in patients with orthostatic vasovagal presyncope.

OBJECTIVES: We studied hemodynamic changes leading to orthostatic vasovagal presyncope to determine whether changes of cerebral artery blood flow velocity precede or follow reductions of arterial pressure. BACKGROUND: Some evidence suggests that disordered cerebral autoregulation contributes to the occurrence of orthostatic vasovagal syncope. We studied cerebral hemodynamics with transcranial Doppler recordings, and we closely examined the temporal sequence of changes of cerebral artery blood flow velocity and systemic arterial pressure in 15 patients who did or did not faint during passive 70 degrees head-up tilt. METHODS: We recorded photoplethysmographic arterial pressure, RR intervals (electrocardiogram) and middle cerebral artery blood flow velocities (mean, total, mean/RR interval; Gosling's pulsatility index; and cerebrovascular resistance [mean cerebral velocity/mean arterial pressure, MAP]). RESULTS: Eight men developed presyncope, and six men and one woman did not. Presyncopal patients reported light-headedness, diaphoresis, or a sensation of fatigue 155 s (range: 25 to 414 s) before any cerebral or systemic hemodynamic change. Average cerebral blood flow velocity (CBFV) changes (defined by an iterative linear regression algorithm) began 67 s (range: 9 to 198 s) before reductions of MAP. Cerebral and systemic hemodynamic measurements remained constant in nonsyncopal patients. CONCLUSIONS: Presyncopal symptoms and CBFV changes precede arterial pressure reductions in patients with orthostatic vasovagal syncope. Therefore, changes of cerebrovascular regulation may contribute to the occurrence of vasovagal reactions.

Blood Flow Velocity↗
PubMed2002

Delayed complications following pacemaker implantation.

Acute complications resulting from permanent pacemaker implantation are well known and include perforation of the right atrium or right ventricle. Recently, several reports have described the occurrence of perforation and pericarditis as late complications following pacemaker implantation. These complications may occur days to weeks following uncomplicated pacemaker implantation and may lead to death if they are not recognized early. Five patients with late complications caused by active-fixation leads are reported and the clinical features of their presentation and management are reviewed. Late perforation of the right atrium or right ventricle is an uncommon complication after pacemaker implantation but should be suspected by the general cardiologist in a patient who has a device implanted within a week to several months prior to the development of chest pain.

Adult↗
PubMed2002

Frequency of symptomatic atrial fibrillation in patients enrolled in the Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) study.

INTRODUCTION: The frequency of symptomatic paroxysmal atrial fibrillation (AF) may identify subsets with different characteristics. Because the approach to AF now is so varied, ranging from drug therapy to surgery and catheter ablation, the frequency of AF may have important therapeutic implications if the frequency identifies subsets with distinguishing features. METHODS AND RESULTS: The Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) Study is evaluating patients with AF who are at high risk for stroke. We evaluated the clinical characteristics of the patients in the AFFIRM Study in an attempt to identify features that might distinguish patients with infrequent and frequent AF occurrences. Patients were divided into five groups, based upon the historic frequency of occurrence of AF at the time the patients were enrolled in the study. Although statistically significant differences were present among the groups, no important differences were noted in clinical or echocardiographic characteristics that could differentiate patients with frequent episodes of AF from other patients in the AFFIRM population. CONCLUSION: In a large population of patients with AF at high risk for stroke, individual historic and echocardiographic characteristics failed to distinguish patients based on the frequency of AF. Those with frequent and infrequent AF were similar. Although AF frequency has been suggested as a marker of a focal etiology in young populations with little overt heart disease, it does not seem to be a distinguishing characteristic in older populations at high risk for stroke.

Age Factors↗
PubMed2002

Phased-array intracardiac echocardiography during pulmonary vein isolation and linear ablation for atrial fibrillation.

INTRODUCTION: Fluoroscopic imaging provides limited anatomic guidance for left atrial structures. The aim of this study was to determine the utility of real-time, phased-array intracardiac echocardiography during radiofrequency ablation for atrial fibrillation. METHODS AND RESULTS: In 29 patients undergoing pulmonary vein isolation (n = 16) or linear (n = 13) left atrial radiofrequency ablation for atrial fibrillation, intracardiac phased-array echocardiography was used to visualize left atrial anatomy and the pulmonary veins, as well as ablation and mapping catheters during ablation procedures. In the 16 pulmonary vein isolation patients, the mean pulmonary vein ostial diameters measured by venography and intracardiac echocardiography were similar for all veins positions, except that left common pulmonary vein diameters were larger as measured by echocardiography (2.50 +/- 0.29 cm) than by venography (1.79 +/- 0.50 cm, P = 0.001). The ostial diameters measured by echocardiography and venography were not correlated, however (r = 0.23, P = 0.19). As directed by echocardiography, only 1 of 25 circular mapping catheters (4%) used in 16 patients was replaced due to inappropriate sizing of the pulmonary veins. Mean pulmonary vein Doppler flow velocities increased after ablation for left-sided veins but ostial diameters were unchanged. In the linear ablation patients, the entire extent of the linear electrode array could be visualized in only 3 of 52 of catheter positions (6%) in the 13 patients. A portion of the catheter could be seen in only 50% of all target catheter positions. CONCLUSION: Phased-array intracardiac echocardiography (1) allows sizing and positioning of pulmonary vein mapping catheters, (2) provides measures of pulmonary vein ostial diameters, (3) continuously monitors pulmonary vein Doppler flow velocities, and (4) has limited use in positioning linear ablation catheters in the left atrium.

Alabama↗