Publications (13)90.83 Total impact
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Article: Sensing failure associated with the Medtronic Sprint Fidelis defibrillator lead.
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ABSTRACT: The diameter of implantable cardioverter-defibrillator (ICD) leads has become progressively smaller over time. However, the long-term performance characteristics of these smaller ICD leads are unknown. We retrospectively evaluated 357 patients who underwent implantation of a Medtronic Sprint Fidelis defibrillating lead at two separate centers between September 2004 and October 2006. Lead characteristics were measured at implant, at early follow-up (1-4 days post implant), and every 3-6 months thereafter. During the study period, 357 patients underwent implantation of the Medtronic Sprint Fidelis lead. The mean R-wave measured at implant through the device was not different (P = NS) when compared with that measured at first follow-up (10.5 +/- 5.0 mV vs 10.7 +/- 5.1 mV). Forty-one patients (13%) had an R-wave amplitude <or= 5 mV measured through the device at implant. Of those patients with an R-wave amplitude <or= 5 mV at implant measured through the device, 63% (n = 26) remained <or= 5 mV for the duration of follow-up. The mean time to R-wave amplitude <or= 5 mV was 96.2 +/- 123 days. During follow-up, 65 (18%) patients developed R-wave <or= 5 mV. Overall 10 lead revisions (2.8%) were performed during the first year of follow-up. Abnormal R-wave sensing is frequently observed during follow-up with the Medtronic Fidelis ICD lead. Lead revision was necessary in 2.8% of the patients, most often (8 of 10) due to abnormal R-wave sensing along with elevated pacing threshold. Whether this issue is limited to this lead or reflects a potential problem with all downsized ICD leads merits further investigation.Journal of Cardiovascular Electrophysiology 03/2008; 19(3):270-4. · 3.06 Impact Factor -
Article: Predictive value of microvolt T-wave alternans in patients with left ventricular dysfunction.
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ABSTRACT: The purpose of this study was to prospectively evaluate the utility of microvolt T-wave alternans (TWA) in predicting arrhythmia-free survival and total mortality in patients with left ventricular (LV) dysfunction. Microvolt TWA has been proposed as a useful tool in identifying patients unlikely to benefit from prophylaxis with implantable cardioverter-defibrillator (ICD) prophylaxis. We evaluated 286 patients with an LV ejection fraction </=35% who underwent TWA and electrophysiologic testing (EPS) owing to nonsustained ventricular tachycardia and/or syncope. Positive and indeterminate TWA results were grouped as non-negative. The primary end point was arrhythmia-free survival; the secondary end point was all-cause mortality. Patients were followed for a mean of 38 +/- 11 months. There was no significant difference between the TWA-negative (n = 90; 31%) and non-negative (n = 196; 69%) groups with respect to ICD implant rates (54% vs. 64%, respectively; p = 0.95) or etiology of cardiomyopathy (ischemic: 73% vs. 76%; p = 0.71). The Kaplan-Meier curves demonstrated improved arrhythmia-free survival in TWA-negative patients (81% vs. 66% at 2 years; p < 0.001), including in both ischemic (79% vs. 64% at 2 years; p = 0.004) and nonischemic (88% vs. 71% at 2 years; p = 0.015) subgroups. Total mortality was lower in the TWA-negative group (10% vs. 18% at 2 years; p = 0.04). The negative predictive value of TWA for (2-year) total mortality was 90%, and 83% for EPS. Microvolt TWA predicts arrhythmia-free survival among patients with LV dysfunction. However, the event rate in the TWA-negative group suggests that TWA may not be capable of identifying a sufficiently low-risk subset in this population to obviate the need for ICD implantation.Journal of the American College of Cardiology 08/2007; 50(2):166-73. · 14.16 Impact Factor -
Article: Effect of bundle branch block on microvolt T-wave alternans and electrophysiologic testing in patients with ischemic cardiomyopathy.
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ABSTRACT: T-wave alternans (TWA) and electrophysiology study (EPS) are used for risk stratification for sudden death. The purpose of the study was to determine the effect of bundle branch block or intraventricular conduction delay on TWA and EPS. 386 patients with coronary artery disease, nonsustained ventricular tachycardia, and left ventricular ejection fraction < or =40% underwent TWA and EPS, and were followed for 40 +/- 19 months. Patients with wide QRS were more likely than narrow QRS patients to have nonnegative TWA (77% vs 63%, P <.01) or positive EPS (60% vs 48%, P = .03). Nonnegative TWA predicted the combined endpoint of ventricular tachyarrhythmia or death in narrow QRS (HR = 1.64, P = .04) but not wide QRS patients (HR = 1.04, P = .91). Similarly, positive EPS predicted the combined endpoint in narrow QRS (HR = 2.28, P <.001) but not wide QRS patients (HR = 0.94, P = .84). In multivariate analysis, QRS width and TWA, as well as QRS width and EPS, were independent predictors of events. There was no TWA- or EPS-based difference in arrhythmia-free survival within any specific wide QRS morphology. TWA and EPS are more often abnormal in patients with a wide QRS than in those with a narrow QRS. In patients with narrow QRS, both TWA and EPS stratify patients according to their risk of ventricular tachyarrhythmia or death. However, among patients with a wide QRS, regardless of specific QRS morphology, the risk is high and comparable regardless of TWA or EPS results. Therefore, the only truly low-risk group consists of those patients with negative test results and a narrow QRS.Heart Rhythm 08/2007; 4(7):904-12. · 4.10 Impact Factor -
Article: Clinical and electrophysiological spectrum of idiopathic ventricular outflow tract arrhythmias.
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ABSTRACT: This study sought to compare and contrast the clinical and electrophysiological characteristics of outflow tract arrhythmias. Idiopathic ventricular outflow tract arrhythmias manifest clinically in 3 forms: 1) paroxysmal sustained monomorphic ventricular tachycardia (SMVT), 2) repetitive nonsustained ventricular tachycardia (NSVT), or 3) premature ventricular contractions (PVCs). Although these arrhythmias have a similar site of origin, it is unknown whether they share a common mechanism or similar clinical features. A total of 127 patients (63 female [50%], mean age 51 +/- 15 years) were evaluated for outflow tract arrhythmias. A total of 36 (28%) presented with the index clinical arrhythmia of SMVT, 46 (36%) with NSVT, and 45 (35%) with PVCs. The sites of origin of the arrhythmias were similar among the 3 groups, occurring in the right ventricular outflow tract in 82%. Sustained ventricular tachycardia was more likely to be induced during exercise in the SMVT (10 of 15 patients [67%]) than NSVT or PVCs groups (p < 0.01). Sustained outflow tract ventricular tachycardia was induced at electrophysiology study in 78% of SMVT patients, 48% of NSVT patients, and 4% of PVCs patients. Adenosine was similarly effective in all 3 groups (p = NS). Patients with outflow tract arrhythmias can be differentiated based on the subtype of arrhythmia. However, the observation that approximately 50% of patients with NSVT and approximately 5% of patients with PVCs have inducible sustained ventricular tachycardia that behaves in an identically unique manner to those who present with sustained ventricular tachycardia (e.g., adenosine-sensitive) suggests that rather than representing distinct entities, outflow arrhythmias may be considered a continuum of a single mechanism.Journal of the American College of Cardiology 05/2007; 49(20):2035-43. · 14.16 Impact Factor -
Article: Adenosine-insensitive focal atrial tachycardia: evidence for de novo micro-re-entry in the human atrium.
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ABSTRACT: The purpose of this work was to describe the entity and mechanism of adenosine-insensitive focal atrial tachycardia (AT). The majority of regular focal ATs demonstrate properties consistent with triggered activity, including termination by adenosine. Less commonly, AT may be due to enhanced automaticity, which is transiently suppressed by adenosine. Small re-entrant circuits may also give rise to focal AT, but limited data exist regarding this entity as a de novo arrhythmia in the human atrium. Eighty cases of focal AT were mapped in the electrophysiology laboratory and challenged with adenosine. Adenosine-sensitive and -insensitive groups were compared with regard to demographics, anatomical distribution, and electrogram characteristics at the tachycardia origin. In response to adenosine, termination occurred in 67 cases (84%), transient suppression in 5 (6%), 6 were insensitive (8%), and 2 exhibited nonspecific responses. Adenosine-insensitive AT arose near the pulmonary vein ostia (4) and from the right atrium (2), whereas adenosine-sensitive AT arose from a wide distribution in both atria. Electrograms at the site of origin for adenosine-insensitive AT were highly fractionated, with longer durations and lower amplitudes compared with AT that terminated or was transiently suppressed. The electrograms at the origin of adenosine-insensitive ATs comprised 22% to 69% of the tachycardia cycle length, compared with 4% to 21% for adenosine-sensitive ATs. In 3 adenosine-insensitive ATs, entrainment was demonstrated with post-pacing intervals equivalent to the tachycardia cycle length. The characteristics of adenosine-insensitive focal AT differ from adenosine-sensitive AT and are consistent with small re-entrant circuits. These data provide evidence that focal re-entry is a mechanism of AT and has an electropharmacologic profile that differs from AT due to automaticity and triggered activity.Journal of the American College of Cardiology 03/2007; 49(12):1324-33. · 14.16 Impact Factor -
Article: Effect of oral beta-blocker therapy on microvolt T-wave alternans and electrophysiology testing in patients with ischemic cardiomyopathy.
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ABSTRACT: Prior investigation has shown that intravenous beta-blockers decrease T-wave alternans (TWA) positivity in patients undergoing electrophysiology study (EPS). The present study examined whether oral beta-blocker use within 24 hours of TWA influences yield and predictive value of TWA and EPS. We prospectively evaluated 387 patients (312 [81%] men, mean age 67 +/- 11 years) with coronary artery disease, left ventricular ejection fraction < or = 40%, and nonsustained ventricular tachycardia who underwent EPS and were followed for a mean of 2.8 +/- 1.4 years. T-Wave alternans was performed using an atrial pacing protocol and interpreted using standard criteria. Beta-blocker status was determined based on oral beta-blocker use in the 24 hours preceding the test: beta-blocker (-) (n = 62), beta-blocker (+) (n = 325). Follow-up for ventricular tachycardia, ventricular fibrillation, and death was obtained from chart review, device interrogation, and the Social Security Death Index. Estimated sensitivity and specificity of TWA and EPS stratified by beta-blocker use were calculated based on event-free 2-year survival. There was no difference in EPS (31 [50%] inducible off beta-blockers vs 166 [51%] on beta-blockers [P = .89]) or TWA (26 [42%] positive, 17 [27%] indeterminate off beta-blockers vs 136 [42%] positive, 81 [25%] indeterminate on beta-blockers [P = .89]). Beta-blocker use within 24 hours of testing did not affect the predictive value of TWA or EPS for overall or 2-year event-free survival. Oral beta-blocker therapy appears to have no effect on yield or predictive value of EPS or TWA in patients with coronary artery disease, diminished left ventricular function, and a history of nonsustained ventricular tachycardia.American heart journal 03/2007; 153(3):392-7. · 4.65 Impact Factor -
Article: Newly detected atrial fibrillation following dual chamber pacemaker implantation.
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ABSTRACT: Pacemaker (PPM)-detected atrial high-rate episodes (AHREs) of even 5-minute duration may identify patients at increased risk for stroke and death. In this study, we sought to determine the incidence of newly detected atrial fibrillation (AF defined as an AHRE > or = 5 minutes) in patients following dual-chamber PPM implantation and to define the clinical predictors of developing AF. We evaluated 262 patients (142 male; age 74 +/- 12 years) without documented AF who underwent PPM implantation for sinus node dysfunction (n = 122) or atrioventricular block (n = 140). Information regarding patient demographics, cardiovascular diseases, and medication history was obtained. The cumulative percentages of ventricular pacing as well as the frequency, duration, and time to first episode of an AHRE were also determined. During follow-up of 596 +/- 344 days, an AHRE > or = 5 minutes was detected in 77 (29%) patients. Of these, 47 (61%) patients had an AHRE > or = 1 hour, 22 (29%) patients had an AHRE > or = 1 day, and 12 (16%) patients had an AHRE > or = 1 week. An AHRE > or = 5 minutes was seen in 24% and 34% of patients at 1 year and 2 years, respectively. Among patients with sinus node dysfunction, > or = 50% cumulative ventricular pacing was the only significant predictor of an AHRE > or = 5 minutes (HR 2.2; CI 1.0-4.7; P = 0.04). Within 1 year of PPM implantation, AF is detected in 24% of patients without history of AF. In patients with sinus node dysfunction, > or = 50% cumulative right ventricular pacing is associated with a 2-fold increase in risk of developing AF.Journal of Cardiovascular Electrophysiology 12/2006; 17(12):1323-8. · 3.06 Impact Factor -
Article: Right and left ventricular outflow tract tachycardias: evidence for a common electrophysiologic mechanism.
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ABSTRACT: "Idiopathic" ventricular arrhythmias most often arise from the right ventricular outflow tract (RVOT), although arrhythmias from the left ventricular outflow tract (LVOT) are also observed. While previous work has elucidated the mechanism and electropharmacologic profile of RVOT arrhythmias, it is unclear whether those from the LVOT share these properties. The purpose of this study was to characterize the electropharmacologic properties of RVOT and LVOT arrhythmias. One hundred twenty-two consecutive patients (61 male; 50.9 +/- 15.2 years) with outflow tract arrhythmias comprise this series, 100 (82%) with an RVOT origin, and 22 (18%) with an LVOT origin. The index arrhythmia was similar: sustained ventricular tachycardia (VT) (RVOT = 28%, LVOT = 36%), nonsustained VT (RVOT = 40%, LVOT = 23%), and premature ventricular complexes (RVOT = 32%, LVOT = 41%) (P = 0.32). Cardiac magnetic resonance imaging and microvolt T-wave alternans results (normal/indeterminate) were also comparable. In addition, 41% with RVOT foci and 50% with LVOT foci were inducible for sustained VT (P = 0.48), and induction of VT was catecholamine dependent in a majority of patients in both groups (66% and 73%; RVOT and LVOT, respectively; P = 1.0). VT was sensitive to adenosine (88% and 78% in the RVOT and LVOT groups, respectively, P = 0.59) as well as blockade of the slow-inward calcium current (RVOT = 70%, LVOT = 80%; P = 1.00) in both groups. Electrophysiologic and pharmacologic properties, including sensitivity to adenosine, are similar for RVOT and LVOT arrhythmias. Despite disparate sites of origin, these data suggest a common arrhythmogenic mechanism, consistent with cyclic AMP-mediated triggered activity. Based on these similarities, these arrhythmias should be considered as a single entity, and classified together as "outflow tract arrhythmias."Journal of Cardiovascular Electrophysiology 11/2006; 17(10):1052-8. · 3.06 Impact Factor -
Article: Reversal of cardiomyopathy in patients with repetitive monomorphic ventricular ectopy originating from the right ventricular outflow tract.
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ABSTRACT: Tachycardia-induced cardiomyopathy caused by ventricular tachycardia is a well-defined clinical entity. Less well appreciated is whether simple ventricular ectopy can result in cardiomyopathy. We sought to examine a potential causal relationship between repetitive monomorphic ventricular ectopy originating from the right ventricular outflow tract and cardiomyopathy and the role of ablation in reversing this process. The study consisted of 27 patients (11 men; age, 47+/-15 years) with repetitive monomorphic ventricular ectopy, including 8 patients (30%) with depressed ventricular function (ejection fraction < or =45%). All patients underwent assessment of cardiac structure and function. The burden of ectopy was quantified through 24-hour Holter monitoring. Patients then underwent ablation guided by 3D mapping. After ablation, patients underwent repeated Holter monitoring and reassessment of cardiac function. Patients with depressed ventricular function were more likely to be older than patients with normal function (58+/-14 versus 42+/-18 years; P=0.013). However, the burden of ventricular ectopy was similar in patients with (17,859+/-13,488 ectopic beats per 24 hours) and without (17,541+/-11,479 ectopic beats per 24 hours; P=0.800) preserved ventricular function. Successful ablation was performed in 23 patients (85%), including 7 of 8 patients with depressed ventricular function. In this latter group, ventricular function improved in all patients (from 39+/-6% to 62+/-6%; P=0.017). Repetitive monomorphic ventricular ectopy (in the absence of sustained ventricular tachycardia) originating from the right ventricular outflow tract is an underappreciated cause of unexplained cardiomyopathy. Successful ablation of the focal source of ventricular ectopy results in normalization of left ventricular function. Patients with ectopy-induced cardiomyopathy are significantly older than patients with preserved ventricular function, which suggests either that older patients are more susceptible to the development of a cardiomyopathy or that the cardiomyopathy has had a longer period of time in which to evolve.Circulation 08/2005; 112(8):1092-7. · 14.74 Impact Factor -
Article: Pseudoblock and pseudoconduction across the cavotricuspid isthmus.
Heart Rhythm 08/2005; 2(7):750-3. · 4.10 Impact Factor -
Article: Three-dimensional identification of the esophagus during ablation of atrial fibrillation.
Heart Rhythm 06/2005; 2(5):565. · 4.10 Impact Factor -
Article: Usefulness of prolonged QRS duration to identify high-risk ischemic cardiomyopathy patients with syncope and inducible ventricular tachycardia.
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ABSTRACT: We evaluated 61 consecutive patients who had coronary artery disease, decreased left ventricular function, and syncope and underwent implantation of a cardioverter-defibrillator because sustained ventricular tachycardia was inducible at electrophysiologic testing. During a follow-up of 3.0 +/- 1.8 years, 23 patients (38%) developed ventricular tachycardia. Prolonged QRS duration (>/=120 ms) was the only significant predictor of arrhythmia. The 1- and 2-year rates without ventricular arrhythmia were 82% and 77%, respectively, in patients whose QRS duration was <120 ms. In contrast, 1- and 2-year rates without ventricular arrhythmia were only 64% and 51%, respectively, in patients whose QRS duration was >/=120 ms (risk ratio 3.7, 95% confidence interval 1.4 to 9.8, p = 0.0092).The American Journal of Cardiology 03/2005; 95(3):391-4. · 3.37 Impact Factor -
Article: Significance of adenosine-induced atrioventricular block in patients with unexplained syncope.
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ABSTRACT: The purpose of this study was to test whether a prolonged (>/=6 seconds) period of AV block in response to adenosine triphosphate (ATP) identifies additional patients at risk for bradycardia who may benefit from pacemaker implantation. Bradycardia is a common etiology for syncope in patients without underlying structural heart disease. Conventional testing using electrophysiologic and tilt table studies often fail to identify patients prone to episodes of symptomatic bradycardia. Adenosine testing was performed in 92 consecutive patients (64 women, age 55 +/- 21 years) with syncope of uncertain origin referred for tilt table testing. The adenosine test measured the maximal R-R interval after bolus administration of intravenous adenosine 150 mug/kg to upright patients. A positive adenosine AV block response was defined as a maximal R-R interval > or =6 seconds. A total of 21 patients (23%) had a positive response. During mean follow-up of 14.3 +/- 5.9 months, 14 patients (16%) had recurrent syncope. Among patients with a positive adenosine response, 3 patients (14%) had recurrent syncope. In comparison, 11 of 69 patients (16%) without adenosine-induced AV block had recurrent syncope (P = 1.00). Prolonged adenosine-induced AV block in patients with unexplained syncope failed to predict recurrent syncopal episodes. These data do not support therapeutic interventions (e.g., pacemaker implantation) based on a positive adenosine AV block response alone.Heart Rhythm 12/2004; 1(6):664-8. · 4.10 Impact Factor
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Institutions
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2004–2007
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Cornell University
- Department of Medicine
Ithaca, NY, USA
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