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Eric J Rashba

Publications and source records attributed to Eric J Rashba.

At least 19 recordsLinked to original sources
PubMed2006

Coronary sinus electrode does not reduce atrial defibrillation thresholds.

BACKGROUND: Atrial defibrillation can be achieved with a conventional dual-coil, active pectoral implantable cardioverter-defibrillator (ICD) lead system. Shocking vectors that incorporate an additional electrode in the CS have been used, but it is unclear if they improve atrial DFTs. OBJECTIVE: The objective of this prospective, randomized study was to determine if a coronary sinus (CS) electrode reduces atrial defibrillation thresholds (DFTs). METHODS: This was a prospective study of 36 patients undergoing initial ICD implant for standard indications. A defibrillation lead with superior vena cava (SVC) and right ventricular (RV) shocking coils was implanted in the RV. An active can emulator (Can) was placed in a pre-pectoral pocket. A lead with a 4 cm long shocking coil was placed in the CS. Atrial DFTs were determined in the following 3 shocking configurations in each patient, with the order of testing randomized: RV --> SVC + Can (Ventricular Triad), distal CS --> SVC + Can (Distal Atrial Triad), and proximal CS --> SVC + Can (Proximal Atrial Triad). RESULTS: The Proximal and Distal Atrial Triad configurations were both associated with significant reductions in peak current (p < 0.01), but this effect was offset by significant increases in shock impedance (p < 0.01), resulting in no net change in the peak voltage or DFT energy in comparison to the Ventricular Triad configuration (Ventricular Triad: 4.9 +/- 6.6 J, Proximal Atrial Triad: 3.3 +/- 4.1J, Distal Atrial Triad: 4.4 +/- 6.7 J, p > 0.2). CONCLUSION: Shocking vectors that incorporate a CS coil do not significantly improve atrial defibrillation efficacy. Since the Ventricular Triad shocking pathway provides reliable atrial and ventricular defibrillation, this configuration should be preferred for combined atrial and ventricular ICDs.

Atrial Fibrillation↗
PubMed2006

Preserved heart rate variability identifies low-risk patients with nonischemic dilated cardiomyopathy: results from the DEFINITE trial.

BACKGROUND: The recent expansion of indications for prophylactic implantable cardioverter-defibrillator (ICD) placement in subjects with nonischemic dilated cardiomyopathy has raised concerns about the cost-effectiveness of this therapy. OBJECTIVES: The purpose of this study was to identify low-risk patients with nonischemic dilated cardiomyopathy who may not require prophylactic ICD placement. METHODS: This was a prospective study of 274 participants in the Defibrillators in Non-Ischemic Cardiomyopathy Treatment Evaluation (DEFINITE) trial, a randomized controlled trial that evaluated the role of prophylactic ICD placement in patients with nonischemic dilated cardiomyopathy. The patients underwent 24-hour Holter recording for analysis of heart rate variability (HRV). The primary HRV variable was the standard deviation of normal R-R intervals (SDNN). Patients with atrial fibrillation and frequent ventricular ectopy (>25% of beats) were excluded from HRV analysis (23% of patients). SDNN was categorized in tertiles, and Kaplan-Meier analysis was performed to compare survival in the three tertiles and excluded patients. RESULTS: The study population was 73% male, with a mean age of 59 +/- 12 years and mean left ventricular ejection fraction of 21% +/- 6%. After 3-year follow-up, significant differences in mortality rates were observed: SDNN >113 ms: 0 (0%), SDNN 81-113 ms: 5 (7%), SDNN <81 ms: 7 (10%), excluded patients: 11 (17%) (P = .03). There were no deaths in the tertile with SDNN >113 ms regardless of treatment assignment (ICD vs control). CONCLUSION: Patients with nonischemic dilated cardiomyopathy and preserved HRV have an excellent prognosis and may not benefit from prophylactic ICD placement. Patients with severely depressed HRV and patients who are excluded from HRV analysis because of atrial fibrillation and frequent ventricular ectopy have the highest mortality.

Cardiomyopathy, Dilated↗
PubMed2006

Effect of an active abdominal pulse generator on defibrillation thresholds with a dual-coil, transvenous ICD lead system.

INTRODUCTION: Many patients with implantable cardioverter defibrillators (ICDs) have older lead systems, which are usually not replaced at the time of pulse generator replacement unless a malfunction is noted. Therefore, optimization of defibrillation with these lead systems is clinically important. The objective of this prospective study was to determine if an active abdominal pulse generator (Can) affects chronic defibrillation thresholds (DFTs) with a dual-coil, transvenous ICD lead system. METHODS AND RESULTS: The study population consisted of 39 patients who presented for routine abdominal pulse generator replacement. Each patient underwent two assessments of DFT using a step-down protocol, with the order of testing randomized. The distal right ventricular (RV) coil was the anode for the first phase of the biphasic shocks. The proximal superior vena cava (SVC) coil was the cathode for the Lead Alone configuration (RV --> SVC). For the Active Can configuration, the SVC coil and Can were connected electrically as the cathode (RV --> SVC + Can). The Active Can configuration was associated with a significant decrease in shock impedance (39.5 +/- 5.8 Omega vs. 50.0 +/- 7.6 Omega, P < 0.01) and a significant increase in peak current (8.3 +/- 2.6 A vs. 7.2 +/- 2.4 A, P < 0.01). There was no significant difference in DFT energy (9.0 +/- 4.6 J vs. 9.8 +/- 5.2 J) or leading edge voltage (319 +/- 86 V vs. 315 +/- 83 V). An adequate safety margin for defibrillation (> or =10 J) was present in all patients with both shocking configurations. CONCLUSION: DFTs are similar with the Active Can and Lead Alone configurations when a dual-coil, transvenous lead is used with a left abdominal pulse generator. Since most commercially available ICDs are only available with an active can, our data support the use of an active can device with this lead system for patients who present for routine pulse generator replacement.

Abdominal Muscles↗
PubMed2005

Clinical predictors of atrial defibrillation thresholds with a dual-coil, active pectoral lead system.

OBJECTIVES: The purpose of this study was to identify clinical predictors of atrial defibrillation thresholds (DFTs) with standard implantable cardioverter-defibrillator (ICD) leads. BACKGROUND: Atrial defibrillation can be achieved with active pectoral, dual-coil transvenous ICD lead systems. If clinical predictors of atrial defibrillation efficacy with these lead systems were identified, they could be used to predict which patients may require more complex lead systems for atrial defibrillation, such as a coronary sinus electrode. METHODS: This was a prospective study of 135 consecutive patients undergoing initial ICD implant for standard indications. The lead system evaluated was a transvenous defibrillation lead with coils in the superior vena cava (SVC) and right ventricular apex (RV), and a left pectoral pulse generator emulator (CAN). The shocking pathway was RV-->SVC+CAN. Atrial DFT was measured using a step-up protocol. Clinical and echocardiographic parameters were evaluated as predictors of atrial DFT and multiple linear regression was performed. RESULTS: Mean atrial DFT was 4.6 +/- 3.8 J. Atrial DFT was < or =3 J in 70 patients (52%) and < or = 10 J in 97% of patients. The highest atrial DFT was 20 J (one patient). Left atrial size (r = 0.21, P = .01) and left ventricular end-diastolic diameter (r = 0.19, P = .02) were independent predictors of atrial DFT. However, these two predictors accounted for only 6% of the variability in atrial DFT. CONCLUSIONS: Clinical parameters are of limited use in predicting atrial DFT with a dual-coil, active pectoral ICD lead system. Because the RV--> SVC + CAN shocking pathway provides reliable atrial and ventricular defibrillation, this configuration should be preferred for combined atrial and ventricular ICDs.

Atrial Fibrillation↗
PubMed2004

Efficacy of transthoracic cardioversion of atrial fibrillation using a biphasic, truncated exponential shock waveform at variable initial shock energies.

Biphasic shocks are more effective than damped sine wave monophasic shocks for transthoracic cardioversion (CV) of atrial fibrillation (AF), but the optimal protocol for CV with biphasic shocks has not been defined. We conducted a prospective, randomized study of 120 consecutive patients with persistent AF to delineate the dose-response curve for CV of AF with a biphasic truncated exponential shock waveform and to identify clinical predictors of shock efficacy. Our data suggest that the initial shock energy for CV with this waveform should be 200 J if the patient weighs <90 kg and 360 J if the patient weighs >/=90 kg.

Aged↗
PubMed2004

Enhanced detection of arrhythmia vulnerability using T wave alternans, left ventricular ejection fraction, and programmed ventricular stimulation: a prospective study in subjects with chronic ischemic heart disease.

INTRODUCTION: In previous studies, the prognostic value of T wave alternans (TWA) was similar to that of programmed ventricular stimulation (PVS). However, presently it is unclear if TWA and PVS identify the same patients or provide complementary risk stratification information. In addition, the effects of left ventricular ejection fraction (LVEF) on the prognostic value of TWA are unknown. The aim of this study was to determine if combined assessment of TWA, LVEF, and PVS improves arrhythmia risk stratification. METHODS AND RESULTS: This was a prospective study of 144 patients with coronary artery disease and LVEF < or =40% who were referred for PVS for standard clinical indications. The endpoint was the combined incidence of death, sustained ventricular arrhythmias, and appropriate implantable cardioverter defibrillator (ICD) therapy. TWA (hazard ratio 2.2, P = 0.03) and PVS (hazard ratio 1.9, P = 0.05) both were significant predictors of endpoint events, and TWA was the only independent predictor. LVEF markedly influenced the prognostic value of TWA, which was a potent predictor of events in subjects with LVEF between 30% and 40% (event rates: TWA+ 36%, TWA- 0%, P = 0.001) but did not predict events in subjects with LVEF <30% (hazard ratio 1.1, P > 0.5). PVS successfully identified additional low-risk patients within the cohort with negative or indeterminate TWA results (hazard ratio 4.7, P = 0.015) but did not provide incremental prognostic information for TWA+ patients (hazard ratio 0.9, P > 0.5). CONCLUSION: The combined use of TWA, LVEF, and PVS is a promising new approach to arrhythmia risk stratification that permits identification of high-risk and very-low-risk patients.

Aged↗
PubMed2004

Optimization of atrial defibrillation with a dual-coil, active pectoral lead system.

INTRODUCTION: Atrial defibrillation can be achieved with standard implantable cardioverter defibrillator (ICD) leads, but the optimal shocking configuration is unknown. The objective of this prospective study was to compare atrial defibrillation thresholds (DFTs) with three shocking configurations that are available with standard ICD leads. METHODS AND RESULTS: This study was a prospective, randomized, paired comparison of shocking configurations on atrial DFTs in 58 patients. The lead system evaluated was a transvenous defibrillation lead with coils in the superior vena cava (SVC) and right ventricular apex (RV) and a left pectoral pulse generator emulator (Can). In the first 33 patients, atrial DFT was measured with the ventricular triad (RV --> SVC + Can) and unipolar (RV --> Can) shocking pathways. In the next 25 patients, atrial DFT was measured with the ventricular triad and the proximal triad (SVC --> RV + Can) configurations. Delivered energy at DFT was significantly lower with the ventricular triad compared to the unipolar configuration (4.7 +/- 3.7 J vs 10.1 +/- 9.5 J, P < 0.001). Peak voltage and shock impedance also were significantly reduced (P < 0.001). There was no significant difference in DFT energy when the ventricular triad and proximal triad shocking configurations were compared (3.6 +/- 3.0 J vs 3.4 +/- 2.9 J for ventricular and proximal triad, respectively, P = NS). Although shock impedance was reduced by 13% with the proximal triad (P < 0.001), this effect was offset by an increased current requirement (10%). CONCLUSION: The ventricular triad is equivalent or superior to other possible shocking pathways for atrial defibrillation afforded by a dual-coil, active pectoral lead system. Because the ventricular triad is also the most efficacious shocking pathway for ventricular defibrillation, this pathway should be preferred for combined atrial and ventricular defibrillators.

Aged↗
PubMed2004

Comparison of step-down and binary search algorithms for determination of defibrillation threshold in humans.

Determination of DFT is an integral part of ICD implantation. Two commonly used methods of DFT determination, the step-down method and the binary search method, were compared in 44 patients undergoing ICD testing for standard clinical indications. The step-down protocol used an initial shock of 18 J. The binary search method began with a shock energy of 9 J and successive shock energies were increased or decreased depending on the success of the previous shock. The DFT was defined as the lowest energy that successfully terminated ventricular fibrillation. The binary search method has the advantage of requiring a predetermined number of shocks, but some have questioned its accuracy. The study found that (mean) DFT obtained by the step-down method was 8.2 +/- 5.0, whereas by the binary search method DFT was 8.1 +/- 0.7 J, P = NS. DFT differed by no more than one step between methods in 32 (71%) of patients. The number of shocks required to determine DFT by the step-down method was 4.6 +/- 1.4, whereas by definition, the binary search method always required three shocks. In conclusion, the binary search method is preferable because it is of comparable efficacy and requires fewer shocks.

Aged↗
PubMed2003

Effect of shock polarity on defibrillation thresholds with a hybrid patch-coil lead system.

INTRODUCTION: Understanding the factors that affect defibrillation thresholds (DFTs) has important implications both for optimization of defibrillation efficacy and for the design of new lead systems. The objective of this prospective study was to evaluate the effect of shock polarity on defibrillation efficacy at the time of routine pulse generator replacement in patients with a hybrid patch-coil lead system. METHODS: Each patient underwent 4 assessments of DFT: monophasic or biphasic shock with standard or reversed polarity, with the order of testing with respect to polarity randomized. In standard polarity, the right atrial coil is the anode and the left ventricular patch is the cathode. RESULTS: The study population of 30 patients was 80% men with a mean age of 65 +/- 9 years and a mean left ventricular ejection fraction of 33 +/- 12%. There was a significant 21% decrease in the mean monophasic DFT with reversed polarity shocks (13.1 +/- 5.9 J vs. 16.6 +/- 6.5 J, p < 0.01). Reversal of shock polarity did not have a significant effect on the mean biphasic DFT (8.0 +/- 4.8 J vs. 8.5 +/- 4.3 J for reversed and standard polarity respectively, p = NS). However, when an elevated biphasic DFT (>or=15 J) was present in either standard or reversed polarity, a significant decrease in DFT was observed when the opposite polarity was used (16.7 +/- 2.5 J vs. 9.1 +/- 2.7 J, n = 9, p < 0.0001). CONCLUSION: Reversal of shock polarity markedly improves monophasic DFTs with the patch-coil lead configuration. The DFT should be determined with both shock polarities to optimize defibrillation efficacy for patients with high biphasic DFTs (>or=15 J).

Aged↗
PubMed2003

Safety of a single successful conversion of ventricular fibrillation before the implantation of cardioverter defibrillators.

UNLABELLED: Multiple successful conversions of ventricular fibrillation (VF) at 10 J below the maximum output of implantable cardioverter defibrillator (ICD) have been recommended as a minimum device implantation criterion. This recommendation is based on the probabilistic properties of defibrillation that necessitates multiple shocks to establish an adequate safety margin for the conversion of subsequent spontaneous arrhythmias. We hypothesized that a single successful shock at a 14 J may suffice. METHODS AND RESULTS: The Low Energy Safety Study (LESS) enrolled 720 patients undergoing initial ICD implantation with a dual-coil transvenous lead and active pulse generator. At implant, an enhanced defibrillation threshold (DFT++) was determined by a rigorous protocol beginning at 14 J, and requiring at least 4 shocks. Fifty percent of all patients were then randomized to full output shock energy and the conversion rates for spontaneous ventricular tachyarrhythmias at rates > 200 beats/min were measured. There were 318 patients randomized to 31 J, of whom 254 were successfully defibrillated by an initial 14 J shock. During a mean follow-up of 24 +/- 12 months, 112 spontaneous VF episodes occurred in 31 patients. The combined conversion success of the first and second shock (when needed) did not differ between the subgroup of patients who were successfully defibrillated by an initial 14 J shock, regardless of the results of additional testing, and the whole cohort who underwent more systematic testing (97% vs 97%). All spontaneous episodes of VF were successfully treated during long-term follow-up. CONCLUSIONS: A first successful shock of 14 J may be a sufficient endpoint to allow the implantation of ICDs with the Triad lead configuration, when programming all shocks to 31 J.

Aged↗
PubMed2003

Distal right ventricular coil position reduces defibrillation thresholds.

UNLABELLED: Distal RV Coil Position Reduces DFTs. INTRODUCTION: Understanding the factors that affect defibrillation thresholds (DFTs) has important implications both for optimization of defibrillation efficacy and for the design of new transvenous leads. The aim of this prospective study was to test the hypothesis that defibrillation efficacy is improved with the right ventricular (RV) coil in a distal position compared with a more proximal RV coil position. METHODS AND RESULTS: A novel defibrillation lead with three adjacent RV defibrillation coils (distal 0.8 cm, middle 3.7 cm, proximal 0.8 cm) was used for this study to permit comparison of DFTs with the proximal and distal RV coil positions without lead repositioning. In the distal RV configuration, the distal and middle RV coils were connected electrically as the anode for defibrillation. In the proximal RV configuration, the middle and proximal coils were the anode. A superior vena cava (SVC) coil and active can were connected electrically as the cathode (reversed polarity, RV-->Can+SVC). In each patient, the DFT was measured twice using a binary search protocol with the distal RV and proximal RV configurations, with the order of testing randomized. The study cohort consisted of 31 subjects (mean age 65 +/- 12 years, mean left ventricular ejection fraction 30% +/- 16%, 81% male predominance). The mean delivered energy (8.2 +/- 5.3 J vs 11.2 +/- 6.1 J), leading-edge voltage (335 +/- 109 V vs 393 +/- 118 V), and peak current (11.6 +/- 5.2 A vs 14.9 +/- 7.3 A) at DFT all were significantly lower with the distal RV configuration compared to the proximal RV configuration (P < 0.01 for all comparisons). CONCLUSION: DFTs are significantly reduced with the distal RV configuration compared to the proximal RV configuration. Defibrillation leads should be designed with the shortest tip to coil distance that can be achieved without compromising ventricular fibrillation sensing.

Aged↗
PubMed2002

Effects of selective autonomic blockade on T-wave alternans in humans.

BACKGROUND: T-wave alternans (TWA) is an important noninvasive measure of ventricular arrhythmia vulnerability. This study tested the hypothesis that the autonomic nervous system influences TWA measurement in high-risk subjects with coronary artery disease. METHODS AND RESULTS: T-wave alternans was measured in 60 patients with coronary artery disease, left ventricular dysfunction, and inducible sustained ventricular tachycardia during electrophysiological studies. All patients had TWA measured at baseline with atrial pacing at 100 bpm (600 ms), 109 bpm (550 ms), and 120 bpm (500 ms). After a 10-minute recovery period, TWA was measured again after sympathetic blockade (esmolol, n=20), parasympathetic blockade (atropine, n=20), or no intervention (control subjects, n=20). The prevalence of significant TWA was unchanged compared with baseline after atropine infusion and in the control group. In contrast, the amplitude of TWA in the vector magnitude lead was significantly reduced after esmolol infusion (P<0.001), and the number of positive TWA tests was reduced by 50% (70% versus 35%, P<0.05). CONCLUSIONS: Our findings have important implications for the use of TWA to risk-stratify patients for life-threatening ventricular arrhythmias and provide a new potential mechanism for the reduction in sudden cardiac death conferred by beta-blockers among patients with coronary artery disease and congestive heart failure.

Adrenergic beta-Antagonists↗
PubMed2002

Lack of benefit of an active pectoral pulse generator on atrial defibrillation thresholds.

INTRODUCTION: Atrial defibrillation can be achieved with standard implantable cardioverter defibrillator leads, which has led to the development of combined atrial and ventricular devices. For ventricular defibrillation, use of an active pectoral electrode (active can) in the shocking pathway markedly reduces defibrillation thresholds (DFTs). However, the effect of an active pectoral can on atrial defibrillation is unknown. METHODS AND RESULTS: This study was a prospective, randomized, paired comparison of two shock configurations on atrial DFTs in 33 patients. The lead system evaluated was a dual-coil transvenous defibrillation lead with a left pectoral pulse generator emulator. Shocks were delivered either between the right ventricular coil and proximal atrial coil (lead) or between the right ventricular coil and an active can in common with the atrial coil (active can). Delivered energy at DFT was 4.2 +/- 4.1 J in the lead configuration and 5.0 +/- 3.7 J in the active can configuration (P = NS). Peak current was 32% higher with an active can (P < 0.01), whereas shock impedance was 18% lower (P < 0.001). Moreover, a low threshold (< or = 3 J) was observed in 61% of subjects in the lead configuration but in only 36% in the active can configuration (P < 0.05). There were no clinical predictors of the atrial DFT. CONCLUSION: These results indicate that low atrial DFTs can be achieved using a transvenous ventricular defibrillation lead. Because no benefit was observed with the use of an active pectoral electrode for atrial defibrillation, programmable shock vectors may be useful for dual-chamber implantable cardioverter defibrillators.

Atrial Fibrillation↗
PubMed2002

Influence of QRS duration on the prognostic value of T wave alternans.

INTRODUCTION: T wave alternans (TWA) is a promising new noninvasive marker of arrhythmia vulnerability that quantifies beat-to-beat changes in ventricular repolarization. Secondary repolarization abnormalities are common in subjects with wide QRS complexes. However, the relationship between TWA and QRS prolongation has not been evaluated. The goal of this study was to determine if QRS prolongation influences the prevalence or prognostic value of TWA. METHODS AND RESULTS: The study consisted of 108 consecutive patients with coronary artery disease and left ventricular ejection fraction < or = 40% who were referred for electrophysiologic studies. Patients underwent TWA testing using bicycle ergometry in the absence of beta-blockers or antiarrhythmic drugs. The primary endpoint was the combined incidence of death, sustained ventricular arrhythmias, and appropriate implantable cardioverter defibrillator therapy. The prognostic value of TWA was assessed in the entire cohort and in two subgroups: QRS < 120 msec (normal, n = 62) and QRS > or = 120 msec (prolonged, n = 46). TWA (hazard ratio 2.2, P = 0.03) and QRS prolongation (hazard ratio 2.2, P = 0.01) were both significant and independent predictors of arrhythmic events. QRS prolongation had no effect on the prevalence of positive TWA tests (QRS < 120 msec: 48%, QRS > or = 120 msec: 50%, P = NS). TWA was a highly significant predictor of events in patients with a normal QRS (hazard ratio 5.8, P = 0.02). In contrast, TWA was not useful for risk stratification in subjects with QRS prolongation (hazard ratio 1.1, P = 0.8). CONCLUSION: TWA is useful only for risk stratification in the absence of QRS prolongation. The presence of QRS prolongation and left ventricular ejection fraction < or = 40% may be sufficient evidence of an adverse prognosis that additional risk stratification is not useful or necessary.

Adult↗
PubMed2002

Exercise is superior to pacing for T wave alternans measurement in subjects with chronic coronary artery disease and left ventricular dysfunction.

INTRODUCTION: T wave alternans (TWA) is a heart rate-dependent marker of vulnerability to ventricular arrhythmias. Atrial pacing and exercise both are used as provocative stimuli to elicit TWA. However, the prognostic value of the two testing methods has not been compared. The aim of this prospective study was to compare the prognostic value of TWA measured during bicycle exercise and atrial pacing in a large cohort of high-risk patients with ischemic heart disease and left ventricular dysfunction. METHODS AND RESULTS: This was a prospective study of 251 patients with coronary artery disease and left ventricular dysfunction who were referred for electrophysiologic studies (EPS) for standard clinical indications. Patients underwent TWA testing using bicycle ergometry (exercise TWA, n = 144) and/or atrial pacing (pacing TWA, n = 178). The primary endpoint was the combined incidence of death, sustained ventricular arrhythmias, and appropriate implantable cardioverter defibrillator therapy. The predictive value of exercise and pacing TWA for EPS results and for endpoint events was determined. Exercise and pacing TWA both were significant predictors of EPS results (odds ratios 3.0 and 2.9 respectively, P < 0.02). Kaplan-Meier survival analysis of the primary endpoint revealed that exercise TWA was a significant predictor of events (hazard ratio 2.2, P = 0.03). In contrast, pacing TWA had no prognostic value for endpoint events (hazard ratio 1.1, P = 0.8). CONCLUSION: TWA should be measured during exercise when it is used for clinical risk stratification. EPS results may not be an adequate surrogate for spontaneous events when evaluating new risk stratification tests.

Aged↗