CONGESTIVE HEART FAILURE, Issue 6 2008
Stefan Toggweiler MD
The intention of this study was to evaluate the short-term effect of right ventricular (RV) pacing on cardiorespiratory function in patients with a biventricular pacemaker. A group of 26 patients with a biventricular pacemaker was enrolled in this cross-over, single-blind study. All patients underwent spiroergometry and electrocardiography in RV and biventricular pacing mode. Peak work capacity (102±32 W and 107±34 W for RV and biventricular pacing mode, respectively; P<.01) and peak oxygen consumption (21.4±6.7 mL/min/kg and 22.6±7.0 mL/min/kg for RV and biventricular pacing mode, respectively; P<.01) were significantly lower in the RV pacing mode. Heart rate at rest was significantly higher with active RV pacing. Short-term RV pacing in patients with a biventricular pacemaker resulted in a higher heart rate at rest, a lower peak work capacity, and a lower peak oxygen consumption compared with that in the biventricular pacing mode. [source]

Feasibility of Biventricular Pacing in Patients With Recent Myocardial Infarction: Impact on Ventricular Remodeling

CONGESTIVE HEART FAILURE, Issue 1 2007
Eugene S. Chung MD
To test the hypothesis that biventricular pacing after a myocardial infarction with reduced ejection fraction can attenuate left ventricular (LV) remodeling, the authors studied 18 patients (myocardial infarction within 30,45 days, ejection fraction ,30%, narrow QRS) randomized to biventricular therapy (biventricular therapy + defibrillator) (biventricular group) or implantable cardioverter-defibrillator alone (control group). At 1, 6, and 12 months, there were no differences in functional or clinical parameters (New York Heart Association, quality of life, 6-minute walk). Twelve-month LV volume remained stable in the biventricular group, but increased in the control group (median LV end-diastolic volume increase, 6.5 mL in biventricular vs 35 mL in control; P=.03; median LV end-diastolic volume decrease, 5.5 mL in biventricular vs 30.5-mL increase in control; P=.11). Biventricular therapy also prevented an increase in sphericity index at 12 months (median, ,2% in biventricular vs 37% in control; P=.06). Delivery of biventricular therapy early after myocardial infarction appears safe and feasible and may attenuate subsequent LV dilation. [source]

Acute Pulmonary Hypertension Secondary to Right Ventricular Pacing in a Patient With Sinus Node Dysfunction and Severe Ischemic Cardiomyopathy

CONGESTIVE HEART FAILURE, Issue 3 2005
Giancarlo H. Speziani MD
Right ventricular pacing has been associated with worsening symptoms of heart failure in patients with cardiomyopathy. We describe a patient with severe ischemic cardiomyopathy and sinus node dysfunction who developed acute worsening of pulmonary hypertension immediately after right ventricular pacing. [source]

Intracardiac Echocardiography in Patients with Pacing and Defibrillating Leads: A Feasibility Study

ECHOCARDIOGRAPHY, Issue 6 2008
Maria Grazia Bongiorni M.D.
Background: Lead extraction, an important and necessary component of treatment for many common device and lead-related complications, is a procedure that can provoke much anxiety in even the most experienced operators given the potentially serious complications. The principal impediment to lead extraction is the body's response to an intravascular foreign body with matrix intravascular neoformation, which causes the lead to adhere to the endocardium or vascular structure, increasing the risk of vascular or myocardial damage with lead removal. Fluoroscopic visualization, the commonly visualization used tool, has several limits in terms of anatomical structures visualization. The aim of this study was to assess the safety and feasibility of intracardiac echocardiography (ICE) in patients undergoing pacing and defibrillating leads before and during a transvenous device removal, and its potential role in detecting intracardiac leads and areas of fibrous adherence. Methods: ICE interrogation was performed in 25 consecutive patients with pacing and defibrillating implantable cardioverter defibrillators (ICD) leads before and during device removal. Results: A programmed ICE analysis was completed in 23 out of 25 patients with excellent resolution, providing a "qualitative-quantitative" information on anatomical structures, cardiac leads, and related areas of fibrous adherence. No ICE-related complications occurred. Conclusions: ICE evaluation is safe and feasible in patients with pacing and defibrillating leads before and during transvenous lead removal, offering an excellent visualization of cardiac leads and related areas of adherence. ICE can assist pacing and ICD lead removal and could improve procedure efficacy and safety. [source]

Echocardiographic Features of Patients With Heart Failure Who May Benefit From Biventricular Pacing

ECHOCARDIOGRAPHY, Issue 3 2003
Amgad N. Makaryus
Background: Recent studies suggest that cardiac resynchronization therapy through biventricular pacing (BVP) may be a promising new treatment for patients with advanced congestive heart failure (CHF). This method involves implantation of pacer leads into the right atrium (RA), right ventricle (RV), and coronary sinus (CS) in patients with ventricular dyssynchrony as evidenced by a bundle branch block pattern on electrocardiogram (ECG). Clinical trials are enrolling stable patients with ejection fractions (EF) , 35%, left ventricular end-diastolic diameters (LVIDd) , 54 mm, and QRS duration ,140 msec. We compared echocardiography features of these patients (group 1) with other patients with EF , 35%, LVIDd , 54 mm, and QRS < 140 msec (group 2 = presumably no dyssynchrony). Methods: Nine hundred fifty-one patients with CHF, LVID 54 mm, EF 35% by echocardiography were retrospectively evaluated. One hundred forty-five patients remained after those with primary valvular disease, prior pacing systems, or chronic atrial arrhythmias were excluded. From this group of 145 patients, a subset of 50 randomly selected patients were further studied (25 patients [7 females, 18 males] from group 1, and 25 patients [7 females, 18 males] from group 2). Mean age group 1 = 75 years old, mean age group 2 = 67 years old. Mean QRS group 1 = 161 msec, mean QRS group 2 = 110 msec. Each group was compared for presence of paradoxical septal motion, atrial and ventricular chamber sizes, LV mass, LVEF, and RV systolic function. Results: Of the initial group of 951 patients, 145 (15%) met inclusion criteria. In the substudy, 20/25 (80%) of group l and 7/25 (28%) of group 2 subjects had paradoxical septal motion on echo (Fisher's exact test, P = 0.0005). The t-tests performed on the other echocardiography variables demonstrated no differences in chamber size, function, or LV mass. Conclusions: Cardiac resynchronization therapy with BVP appears to target a relatively small population of our advanced CHF patients (15% or less). Although increasing QRS duration on ECG is associated with more frequent paradoxical septal motion on echo, it is not entirely predictive. Paradoxical septal motion on echo may therefore be more sensitive at identifying patients who respond to BVP. Further prospective studies are needed. (ECHOCARDIOGRAPHY, Volume 20, April 2003) [source]

Robustness of a 3 min all-out cycling test to manipulations of power profile and cadence in humans

EXPERIMENTAL PHYSIOLOGY, Issue 3 2008
Anni Vanhatalo
The purpose of this study was to assess whether end-test power output (EP, synonymous with ,critical power') and the work done above EP (WEP) during a 3 min all-out cycling test against a fixed resistance were affected by the manipulation of cadence or pacing. Nine subjects performed a ramp test followed, in random order, by three cadence trials (in which flywheel resistance was manipulated to achieve end-test cadences which varied by ,20 r.p.m.) and two pacing trials (30 s at 100 or 130% of maximal ramp test power, followed by 2.5 min all-out effort against standard resistance). End-test power output was calculated as the mean power output over the final 30 s and the WEP as the power,time integral over 180 s for each trial. End-test power output was unaffected by reducing cadence below that of the ,standard test' but was reduced by ,10 W on the adoption of a higher cadence [244 ± 41 W for high cadence (at an end-test cadence of 95 ± 7 r.p.m.), 254 ± 40 W for the standard test (at 88 ± 6 r.p.m.) and 251 ± 38 W for low cadence (at 77 ± 5 r.p.m.)]. Pacing over the initial 30 s of the test had no effect on the EP or WEP estimates in comparison with the standard trial. The WEP was significantly higher in the low cadence trial (16.2 ± 4.4 kJ) and lower in the high cadence trial (12.9 ± 3.6 kJ) than in the standard test (14.2 ± 3.7 kJ). Thus, EP is robust to the manipulation of power profile but is reduced by adopting cadences higher than ,standard'. While the WEP is robust to initial pacing applied, it is sensitive to even relatively minor changes in cadence. [source]

Long-Term Mechanical Consequences of Permanent Right Ventricular Pacing: Effect of Pacing Site

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 10 2010
DARRYL P. LEONG M.B.B.S.
Optimal Right Ventricular Pacing,Introduction: Long-term right ventricular apical (RVA) pacing has been associated with adverse effects on left ventricular systolic function; however, the comparative effects of right ventricular outflow tract (RVOT) pacing are unknown. Our aim was therefore to examine the long-term effects of septal RVOT versus RVA pacing on left ventricular and atrial structure and function. Methods: Fifty-eight patients who were prospectively randomized to long-term pacing either from the right ventricular apex or RVOT septum were studied echocardiographically. Left ventricular (LV) and atrial (LA) volumes were measured. LV 2D strain and tissue velocity images were analyzed to measure 18-segment time-to-peak longitudinal systolic strain and 12-segment time-to-peak systolic tissue velocity. Intra-LV synchrony was assessed by their respective standard deviations. Interventricular mechanical delay was measured as the difference in time-to-onset of systolic flow in the RVOT and LV outflow tract. Septal A' was measured using tissue velocity images. Results: Following 29 ± 10 months pacing, there was a significant difference in LV ejection fraction (P < 0.001), LV end-systolic volume (P = 0.007), and LA volume (P = 0.02) favoring the RVOT-paced group over the RVA-paced patients. RVA-pacing was associated with greater interventricular mechanical dyssynchrony and intra-LV dyssynchrony than RVOT-pacing. Septal A' was adversely affected by intra-LV dyssynchrony (P < 0.05). Conclusions: Long-term RVOT-pacing was associated with superior indices of LV structure and function compared with RVA-pacing, and was associated with less adverse LA remodeling. If pacing cannot be avoided, the RVOT septum may be the preferred site for right ventricular pacing. (J Cardiovasc Electrophysiol, Vol. 21, pp. 1120-1126) [source]

Age-Related Increase in Atrial Fibrillation Induced by Transvenous Catheter-Based Atrial Burst Pacing: An In Vivo Rat Model of Inducible Atrial Fibrillation

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 1 2010
DONGZHU XU M.D.
AF Rat Model Induced by Transvenous Catheter Pacing.,Introduction: Large animal models of atrial fibrillation (AF) are well established, but limited experimental reports exist on small animal models. We sought to develop an in vivo rat model of AF using a transvenous catheter and to evaluate the model's underlying characteristics. Methods and Results: Echocardiogram, surface electrocardiogram (ECG), and atrial effective refractory period (AERP) were recorded at baseline in young (3 months) and middle-aged (9 months) Wistar rats. AF inducibility and duration were measured through transvenous electrode catheter in young (n = 11) and middle-aged rats (n = 11) and middle-aged rats treated with either pilsicainide (1 mg/kg iv, n = 7) or amiodarone (10 mg/kg iv, n = 9). Degrees of interstitial fibrosis and cellular hypertrophy in the atria were assessed histologically. The P-wave duration and AERP were significantly longer and echocardiographic left atrial dimension significantly larger in middle-aged versus young rats. AF was inducible in >90% of all procedures in both untreated rat groups, whereas AF inducibility was reduced by the antiarrhythmic drugs. The AF duration was significantly longer in middle-aged than in young rats and was significantly shortened by treatment with either pilsicainide or amiodarone. Histologic analysis revealed significant increases in atrial interstitial fibrosis and cellular diameter in middle-aged versus young rats. Conclusions: Transvenous catheter-based AF is significantly longer in middle-aged than in young rats and is markedly reduced by treatment with antiarrhythmic drugs. This rat model of AF is simple, reproducible, and reliable for examining pharmacologic effects on AF and studying the process of atrial remodeling.(J Cardiovasc Electrophysiol, Vol. 21, pp. 88,93, January 2010) [source]

Synchronous Ventricular Pacing without Crossing the Tricuspid Valve or Entering the Coronary Sinus,Preliminary Results

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 12 2009
BENHUR D. HENZ M.D.
Background: Right ventricular apical (RVA) pacing promotes tricuspid regurgitation (TR), electromechanical dyssynchrony, and ventricular dysfunction. We tested a novel intramyocardial bipolar lead to assess whether stimulation of the atrioventricular septum (AVS) produces synchronous ventricular activation without crossing the tricuspid valve (TV). Methods: A lead with an active external helix and central pin was placed on the AVS and the RVA in three dogs. High-density electroanatomic (EA) mapping was performed of both ventricles endocardially and epicardially. Intracardiac echocardiography was used to access ventricular synchrony. Results: The lead was successfully deployed into the AVS in all cases with consistent capture of the ventricular myocardium without atrial capture or sensing. The QRS duration was less with AVS compared with RVA pacing (89 ± 4 ms vs. 100 ± 11 ms [P < 0.0001, GEE P = 0.03]). There was decreased delay between color Doppler M-mode visualized peak contraction of the septum and the mid left ventricular free wall with AVS compared with RVA pacing (89 ± 91 ms vs. 250 ± 11 ms [P < 0.0001, GEE P = 0.006]). Activation time between the mid septum and mid free wall was shorter with AVS versus RVA pacing (20.4 ± 7.7 vs. 30.8 ± 11.6 [P = 0.01, GEE P = 0.07]). The interval between QRS onset to earliest free wall activation was shorter with AVS vs. RVA pacing (19.2 ± 6.4 ms vs. 31.1 ± 11.7 ms [P = 0.005, GEE P = 0.02]). Conclusion: The AVS was successfully paced in three dogs resulting in synchronous ventricular activation without crossing the TV. [source]

Implantable Cardioverter Defibrillators: Do Women Fare Worse Than Men?

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 9 2009
Gender Comparison in the INTRINSIC RV Trial
Introduction: Due to limited enrollment of women in previous trials, there is a paucity of data comparing outcome and arrhythmic events in men versus women with implantable cardioverter defibrillators (ICDs). Methods and Results: We analyzed outcome of patients in the INTRINSIC RV (Inhibition of Unnecessary RV Pacing with AV Search Hysteresis in ICDs) trial based on gender. Women comprised 19% (293/1530) of the INTRINSIC RV population. Compared with men, women were less likely to have coronary disease, ischemic cardiomyopathy, and hyperlipidemia, and were more likely to have congestive heart failure and diabetes. Women were less likely to receive beta blockers and ACE inhibitors, and more likely to receive diuretics. Over 10.8 ± 3.5 months of follow-up, unadjusted mortality was higher in women than men (6.8% vs 4.1%, P = 0.04). Heart failure hospitalizations occurred in 7.9% of women versus 5.7% of men (P = 0.13). After adjustment for baseline differences and drug therapy, there was no significant difference in mortality between men and women. Adverse events were observed more often in women. There were no gender differences in the percentage of patients receiving appropriate or inappropriate ICD shocks. Conclusions: In INTRINSIC RV, women receiving ICDs differed from men regarding baseline characteristics and drug therapy. After adjusting for baseline differences and medical therapy, there were no differences in heart failure hospitalization, survival, or ICD shock therapy during follow-up. Apparent undertreatment of heart failure and greater frequency of adverse advents in women receiving ICDs warrant further investigation. [source]

Severe Atrioventricular Decoupling, Uncoupling, and Ventriculoatrial Coupling During Enhanced Atrial Pacing: Incidence, Mechanisms, and Implications for Minimizing Right Ventricular Pacing in ICD Patients

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 11 2008
MICHAEL O. SWEENEY M.D.
Background: Enhanced AAI/R pacing minimizes right ventricular pacing but may permit or induce AV decoupling (AV-DC) due to unrestricted AV intervals (AVIs). The purpose of this study was to characterize and quantify AVI behavior in a randomized trial of enhanced AAI/R pacing in ICD patients. Methods: One hundred twenty-one patients in the Marquis ICD MVPÔ Study, a randomized 1-month crossover comparison of cumulative% ventricular pacing (Cum%VP) in enhanced AAIR (MVP) vs DDD/R, were analyzed. AV-DC was defined as ,40% AVIs >300 ms; VA coupling (VA-C) was defined as%V-atrial pace (AP) intervals <300 ms. Dynamic AVI behavior and increases in Cum%VP due to AV block (AV uncoupling, AV-UC) were characterized using Holters with real-time ICD telemetry. Results: AV-DC occurred in 17 (14%) of patients. Baseline PR, amiodarone, nighttime, lower rate >60 beats/min, rate response, and Cum%AP were associated with longer AVIs. Logistic regression identified baseline PR (odds ratio [OR]= 1.024, 95% confidence interval [CI] 1.007,1.042; P = 0.005), and Cum%AP (OR = 1.089, 95% CI 1.027,1.154; P = 0.004) as predictors of AV-DC. AV-DC was associated with ,10-fold increases in both Cum%VP (13.6 ± 28.3% vs 1.2 ± 3.9%; P = 0.023) due to transient AV-UC) and VA-C (6.0 ± 17.5% vs 0.5 ± 1.2%, P = 0.028). AV coupling (<40% AVIs >300 ms) was preserved in 104 (86%) patients. Conclusions: AV-DC, VA-C, and AV-UC may be worsened or induced by enhanced AAI/R pacing. Conservative programming of lower rate and rate response should reduce the risk of AV-DC by reducing Cum%AP. [source]

Predictors of All-Cause Mortality for Patients with Chronic Chagas' Heart Disease Receiving Implantable Cardioverter Defibrillator Therapy

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 12 2007
AUGUSTO CARDINALLI-NETO M.D., Ph.D.
Background: Implantable Cardioverter Defibrillators (ICD) have sporadically been used in the treatment of either Sustained Ventricular Tachycardia (VT) or Ventricular Fibrillation (VF) in Chagas' disease patients. This study aimed at determining predictors of all-cause mortality for Chagas' disease patients receiving ICD therapy. Methods and Results: Ninety consecutive patients were entered the study. Mean left ventricular ejection fraction was 47 ± 13%. Twenty-five (28%) patients had no left ventricular systolic dysfunction. After device implantation, all patients were given amiodarone (mean daily dose = 331, 1 ± 153,3 mg), whereas a B-Blocking agent was given to 37 (40%) out of 90 patients. Results: A total of 4,274 arrhythmias were observed on stored electrogram in 64 (71%) out of 90 patients during the study period; SVT was observed in 45 out of 64 (70%) patients, and VF in 19 (30%) out of 64 patients. Twenty-six (29%) out of 90 patients had no arrhythmia. Fifty-eight (64%) out of 90 patients received appropriate shock, whereas Antitachycardia Pacing was delivered to 58 (64%) out of 90 patients. There were 31 (34%) deaths during the study period. Five patients were lost to follow up. Sudden cardiac death affected 2 (7%) out of 26 patients, whereas pump failure death was detected in the remaining 24 (93%) patients. Number of shocks per patient per 30 days was the only independent predictor of mortality. Conclusion: Number of shocks per patient per 30 days predicts outcome in Chagas' disease patients treated with ICD. [source]

The VA Relationship After Differential Atrial Overdrive Pacing: A Novel Tool for the Diagnosis of Atrial Tachycardia in the Electrophysiologic Laboratory

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 11 2007
MITSUNORI MARUYAMA M.D.
Introduction: Despite recent advances in clinical electrophysiology, diagnosis of atrial tachycardia (AT) originating near Koch's triangle remains challenging. We sought a novel technique for rapid and accurate diagnosis of AT in the electrophysiologic laboratory. Methods: Sixty-two supraventricular tachycardias including 18 ATs (10 ATs arising from near Koch's triangle), 32 atrioventricular nodal reentrant tachycardias (AVNRTs), and 12 orthodromic reciprocating tachycardias (ORTs) were studied. Overdrive pacing during the tachycardia from different atrial sites was performed, and the maximal difference in the postpacing VA intervals (last captured ventricular electrogram to the earliest atrial electrogram of the initial beat after pacing) among the different pacing sites was calculated (delta-VA interval). Results: The delta-VA intervals were >14 ms in all AT patients and <14 ms in all AVNRT/ORT patients, and thus, the delta-VA interval was diagnostic for AT with the sensitivity, specificity, and positive and negative predictive values all being 100%. When the diagnostic value of the delta-VA interval and conventional maneuvers were compared for differentiating AT from atypical AVNRT, both a delta-VA interval >14 ms and "atrial-atrial-ventricular" response after overdrive ventricular pacing during the tachycardia were diagnostic. However, the "atrial-atrial-ventricular" response criterion was available in only 52% of the patients because of poor ventriculoatrial conduction. Conclusions: The delta-VA interval was useful for diagnosing AT irrespective of patient conditions such as ventriculoatrial conduction. [source]

Biventricular Versus Right Ventricular Pacing in Patients with AV Block (BLOCK HF): Clinical Study Design and Rationale

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 9 2007
ANNE B. CURTIS M.D.
Background: Right ventricular (RV) pacing restores ventricular systole in patients with atrioventricular (AV) block, yet recent studies have suggested that in patients with AV block and left ventricular (LV) dysfunction, RV pacing may exacerbate the progression to heart failure (HF). BLOCK HF is a prospective, multi-center, randomized, double-blind, controlled trial designed to determine whether patients with AV block, LV dysfunction (EF , 50%), and mild to moderate HF (NYHA I-III) who require pacing benefit from biventricular (BiV) pacing, compared with RV pacing alone. Objective: The primary objective of this trial is to determine whether the time to first event (all-cause mortality, heart failure-related urgent care, or a , 15% increase in left ventricular end systolic volume index [LVESVI]) for patients with BiV pacing is superior to that of patients with RV pacing. Methods: Patients with AV block and LV dysfunction who require permanent pacing and undergo successful implantation of a commercial Medtronic CRT device, with or without an ICD, will be randomized to BiV or RV pacing. Patients are followed at least every 6 months until study closure. Up to 1,636 patients may be enrolled in 150 centers worldwide. Conclusion: BLOCK HF is a large, randomized, clinical study in pacing-indicated patients with AV block, mild to moderate HF symptoms, and LV dysfunction to determine whether BiV pacing is superior to RV pacing in slowing the progression of HF. [source]

A Novel Pacing Maneuver to Localize Focal Atrial Tachycardia

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 1 2007
F.R.A.C.P., UWAIS MOHAMED M.B.B.S.
Background: Although focal atrial tachycardias cannot be entrained, we hypothesized that atrial overdrive pacing (AOP) can be an effective adjunct to localize the focus of these tachycardias at the site where the post-pacing interval (PPI) is closest to the tachycardia cycle length (TCL). Methods: Overdrive pacing was performed in nine patients during atrial tachycardia, and in a comparison group of 15 patients during sinus rhythm. Pacing at a rate slightly faster than atrial tachycardia in group 1 and sinus rhythm in group 2 was performed from five standardized sites in the right atrium and coronary sinus. The difference between the PPI and tachycardia or sinus cycle length (SCL) was recorded at each site. The tachycardia focus was then located and ablated in group 1, and the atrial site with earliest activation was mapped in group 2. Results: In both groups the PPI-TCL at the five pacing sites reflected the distance from the AT focus or sinus node. In group 1, PPI-TCL at the successful ablation site was 11 ± 8 msec. In group 2, PPI-SCL at the site of earliest atrial activation was 131 ± 37 msec (P < 0.001 for comparison). In groups 1 and 2, calculated values at the five pacing sites were proportional to the distance from the AT focus or sinus node, respectively. Conclusions: The PPI-TCL after-AOP of focal atrial tachycardia has a direct relationship to proximity of the pacing site to the focus, and may be clinically useful in finding a successful ablation site. [source]

Simultaneous Atrial and Ventricular Anti-Tachycardia Pacing as a Novel Method of Rhythm Discrimination

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 7 2006
SAMIR SABA M.D.
Background: Inappropriate shocks remain a problem in patients with defibrillators (ICD). Objective: To evaluate a new discrimination algorithm for supraventricular (SVT) and ventricular (VT) tachycardias, based on the response to simultaneous (A+V) atrial (A) and ventricular (V) anti-tachycardia pacing (ATP). Methods: Patients undergoing electrophysiological testing or dual-chamber implantable cardioverter-defibrillator (ICD) implantation were enrolled (N = 32) and underwent A+V ATP through a Marquis ICD with investigational software. If persisting after ATP, the rhythm was classified as VT if the first electrical event was sensed on the V channel and as an SVT otherwise. Results: Arrhythmia sequences (N = 275; 53 VT; 222 SVT) were analyzed in 26 patients (age = 51 ± 17 years, 13 men, LVEF = 0.49 ± 0.14). In response to A+V ATP, 55% of SVT versus 41% of VT episodes were terminated (P = NS). Termination of VT but not of SVT was more likely with faster (50% at ATP/arrhythmia cycle length (CL) = 0.81 vs 8% at ATP/arrhythmia CL = 0.88, P = 0.02) but not with longer ATP bursts (P = NS). Of the 115 arrhythmias that persisted after A+V ATP, the algorithm correctly classified 24 of 24 VT (GEE-adjusted sensitivity = 100%) and 85 of 91 SVT (GEE-adjusted specificity = 93%). Proarrhythmia was noted after two A+V ATP, in the form of atrial fibrillation induction and VT acceleration. Conclusions: We describe a new algorithm that can discriminate between SVT and VT with a high sensitivity and specificity. This form of ATP can terminate 55% of SVT sequences. The performance of this new algorithm merits further testing in a large population of dual-chamber ICD patients. [source]

Two Different Cycle Lengths During Left Ventricular Pacing: What Is the Mechanism?

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 6 2006
JOSEPH Y. CHAN M.R.C.P.
[source]

Cardiac Reflexes During Pacing: Are We Getting to the Heart of the Matter?

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 5 2006
CARLOS A. MORILLO M.D., F.A.C.C., F.R.C.P.C.
[source]

Enalapril Preserves Sinus Node Function in a Canine Atrial Fibrillation Model Induced by Rapid Atrial Pacing

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 11 2005
MASAO SAKABE M.D.
Effects of enalapril on canine sinus node (SN) dysfunction induced by long-term rapid atrial pacing were investigated. Methods and Results: Seventeen beagles were pretreated with either placebo (group I, n = 9) or enalapril 1 mg/kg/day (group II, n = 8) and paced at 500/min from the right atrial appendage for 4 weeks. Every week, corrected sinus node recovery time (CSNRT) and sinus cycle length (SCL) were measured. Quantitative analysis of interstitial fibrosis (IF) and adipose tissue (AT) in the SN was performed with Masson's trichrome stain, and apoptosis of the sinus nodal cells were detected with terminal deoxynucleotidyl transferase nick end-labeling. In group I, rapid atrial pacing prolonged both CSNRT and SCL. After 4 weeks of pacing, CSNRT and SCL were significantly shorter in group II (CSNRT, 410 ± 37 msec; SCL, 426 ± 34 msec) than in group I (CSNRT, 717 ± 52 msec, P < 0.005; SCL, 568 ± 73 msec, P < 0.05). Both IF and AT of the SN were greater in group I (IF, 9.7 ± 1.9%; AT, 32.6 ± 5.9%) than in seven sham dogs (IF, 2.4 ± 0.9%, P < 0.05; AT, 4.0 ± 1.7%, P < 0.05) and in group II dogs (IF, 4.0 ± 2.0%, P < 0.05; AT, 4.0 ± 1.7%, P < 0.05). End-labeling assay was positive in three of nine dogs in group I, but negative in group II and sham dogs. Conclusions: Rapid atrial pacing impaired SN function through IF and AT of the SN. Enalapril prevented these pacing-induced degenerative changes and improved SN function. [source]

The Clinical Implications of Cumulative Right Ventricular Pacing in the Multicenter Automatic Defibrillator Trial II

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 4 2005
JONATHAN S. STEINBERG M.D.
Introduction: This study was designed to assess whether right ventricular pacing in the implantable cardioverter defibrillator (ICD) arm of the Multicenter Automatic Defibrillator Implantation Trial (MADIT) II was associated with an unfavorable outcome. Methods and Results: Data on the number of ventricular paced beats were available in 567 (76%) of 742 MADIT II patients with ICDs. The number of ventricular paced beats over the total number of beats showed a bimodal distribution with patients being predominantly paced or nonpaced. Therefore, patients were dichotomized at 0,50% and 51,100% of cumulative pacing with median pacing rate 0.2% and 95.6%, respectively. Endpoints included new or worsening heart failure, appropriate ICD therapy for VT/VF, and the combined endpoint of heart failure or death. Clinical features associated with frequent ventricular pacing included age ,65 years, advanced NYHA heart failure class, LVEF < 0.25, first degree AV and bundle branch block, and amiodarone use. During follow-up, 119 patients (21%) had new or worsened heart failure, 130 (23%) had new or worsened heart failure or death, and 142 (25%) had appropriate therapy for VT/VF. In comparison to patients with infrequent pacing, those with frequent pacing had significantly higher risk of new or worsened heart failure (hazard ratio = 1.93; P = 0.002) and VT/VF requiring ICD therapy (HR = 1.50; P = 0.02). Conclusions: Patients in MADIT II who were predominantly paced had a higher rate of new or worsened heart failure and were more likely to receive therapy for VT/VF. These results suggest the deleterious consequences of RV pacing, particularly in the setting of severe LV dysfunction. [source]

Termination of Epicardial Left Ventricular Tachycardia by Pacing without Global Capture

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 1 2005
ASEEM D. DESAI M.D.
It is generally accepted that the diagnosis of an epicardial origin of ventricular tachycardia (VT) can be made indirectly by observing VT termination during ablation on the epicardial surface of the heart. There is a caveat, however, which is that termination of VT during radiofrequency current application on the epicardial surface could be due to extension of the lesion beyond the epicardium. Therefore, successful ablation of VT using an epicardial approach does not necessarily prove the reentrant circuit is located superficially. We present a case of a 44-year-old man with VT storm who demonstrated successful termination of VT with radiofrequency current application on the epicardial surface of the heart. This site corresponded to a site where pacing during VT resulted in termination of VT without global capture. Isolated mid-diastolic potentials were only seen at this site as well. We hypothesize that the finding of termination of VT by pacing without global capture supports the argument that the site of pacing is a critical part of the VT circuit. [source]

Biventricular Pacing and Left Ventricular Pacing in Heart Failure:

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 12 2004
Similar Hemodynamic Improvement Despite Marked Electromechanical Differences
Introduction: We conducted an acute echocardiographic study comparing hemodynamic and ventricular dyssynchrony parameters during left ventricular pacing (LVP) and biventricular pacing (BVP). We sought to clarify the mechanisms responsible for similar hemodynamic improvement despite differences in electrical activation. Methods and Results: Thirty-three patients underwent echocardiography prior to implantation with a multisite pacing device (spontaneous rhythm [SR]) and 2 days after implantation (BVP and LVP). Interventricular dyssynchrony (pulsed-wave Doppler), extent of myocardium displaying delayed longitudinal contraction (%DLC; tissue tracking), and index of LV dyssynchrony (pulsed-wave tissue Doppler imaging) were assessed. Compared to SR, BVP and LVP caused similar significant improvement of cardiac output (LVP: 3.2 ± 0.5, BVP: 3.1 ± 0.7, SR: 2.3 ± 0.6 L/min; P < 0.01) and mitral regurgitation (LVP: 25.1 ± 10, BVP: 24.7 ± 11, baseline: 37.9 ± 14% jet area/left atria area; P < 0.01). LVP resulted in a smaller index of LV dyssynchrony than BVP (29 ± 10 vs 34 ± 14; P < 0.05). However, LVP exhibited a longer aortic preejection delay (220 ± 34 vs 186 ± 28 msec; P < 0.01), longer LV electromechanical delays (244.5 ± 39 vs 209.5 ± 47 msec; P < 0.05), greater interventricular dyssynchrony (56.6 ± 18 vs 31.4 ± 18; P < 0.01), and higher%DLC (40.1 ± 08 vs 30.3 ± 09; P < 0.05), leading to shorter LV filling time (387 ± 54 vs 348 ± 44 msec; P < 0.05) compared to BVP. Conclusion: Although LVP and BVP provide similar hemodynamic improvement, LVP results in more homogeneous but substantially delayed LV contraction, leading to shortened filling time and less reduction in postsystolic contraction. These data may influence the choice of individual optimal pacing configuration. [source]

High-Density Mapping of Left Atrial Endocardial Activation During Sinus Rhythm and Coronary Sinus Pacing in Patients with Paroxysmal Atrial Fibrillation

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 10 2004
TIMOTHY R. BETTS M.D.
Introduction: This study was designed to record global high-density maps of left atrial endocardial activation during sinus rhythm and coronary sinus pacing. Method and Results: Noncontact mapping of the left atrium was performed in nine patients with paroxysmal atrial fibrillation undergoing pulmonary vein ablation procedures. High-density isopotential and isochronal activation maps were superimposed on three-dimensional reconstructions of left atrial geometry. Mapping was repeated during pacing from sites within the coronary sinus. Earliest left atrial endocardial activation occurred anterior to the right pulmonary veins in seven patients and on the anterosuperior septum in two patients. A line of conduction block was seen in the posterior wall and inferior septum in all patients. The direction of activation in the left atrial myocardium overlying the coronary sinus was different from the electrogram sequence in the coronary sinus catheter in 6 of 9 patients. During coronary sinus pacing, activation entered the left atrium a mean (SD) of 41 (13) ms after the pacing stimulus at a site 12 (10) mm from the endocardium overlying the pacing electrode. Lines of conduction block were present in the posterior wall and inferior septum. Conclusion: In patients with paroxysmal atrial fibrillation, lines of conduction block are present in the left atrium during sinus rhythm and coronary sinus pacing. Electrograms recorded in the coronary sinus infrequently correspond to the direction of activation in the overlying left atrial myocardium. [source]

Reentrant Ventricular Tachycardia Originating from the Aortic Sinus Cusp:

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 10 2004
A Case Report
We report a case of idiopathic reentrant ventricular tachycardia (VT) originating from the left aortic sinus cusp. A prepotential preceding the QRS complex by 58 ms was recorded from the posterior right ventricular (RV) outflow tract. During VT entrainment observed by pacing from the midseptal RV, it initially was orthodromically captured with a long conduction time but then antidromically captured as the pacing cycle rate was increased. Pacing at that site failed to show concealed entrainment despite a postpacing interval similar to the VT cycle length. Radiofrequency catheter ablation abolished the VT in the left aortic sinus cusp where a prepotential preceding the QRS complex by 78 ms with a postpacing interval similar to the VT cycle length was recorded in addition to concealed entrainment. The findings suggest that, in this VT, a critical slow conduction zone is partially present extending from the left aortic sinus cusp to the posterior right ventricular outflow tract. The patient has remained free from VT recurrence after 5-month follow-up. [source]

Improvement of Defibrillation Efficacy with Preshock Synchronized Pacing

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 5 2004
HUI-NAM PAK M.D., Ph.D.
Introduction: We previously demonstrated that wavefront synchronization by spatiotemporal excitable gap pacing (Sync P) is effective at facilitating spontaneous termination of ventricular fibrillation (VF). Therefore, we hypothesized that a spatiotemporally controlled defibrillation (STCD) strategy using defibrillation shocks preceded by Sync P can improve defibrillation efficacy. Method and Results: We explored the STCD effects in 13 isolated rabbit hearts. During VF, a low-voltage gradient (LVG) area was synchronized by Sync P for 0.92 second. For Sync P, optical action potentials (OAPs) adjacent to four pacing electrodes (10 mm apart) were monitored. When one of the electrodes was in the excitable gap, a 5-mA current was administered from all electrodes. A shock was delivered 23 ms after the excitable gap when the LVG area was unexcitable. The effects of STCD was compared to random shocks (C) by evaluating the defibrillation threshold 50% (DFT50; n = 35 for each) and preshock coupling intervals (n = 208 for STCD, n = 172 for C). Results were as follows. (1) Sync P caused wavefront synchronization as indicated by a decreased number of phase singularity points (P < 0.0001) and reduced spatial dispersion of VF cycle length (P < 0.01). (2) STCD decreased DFT50 by 10.3% (P < 0.05). (3) The successful shocks showed shorter preshock coupling intervals (CI; P < 0.05) and a higher proportion of unexcitable shock at the LVG area (P < 0.001) than failed shocks. STCD showed shorter CIs (P < 0.05) and a higher unexcitable shock rate at LVG area (P < 0.05) than C. Conclusion: STCD improves defibrillation efficacy by synchronizing VF activations and increasing probability of shock delivery to the unexcitable LVG area. (J Cardiovasc Electrophysiol, Vol. 15, pp. 581-587, May 2004) [source]

Evaluation of Myocardial Performance with Conventional Single-Site Ventricular Pacing and Biventricular Pacing in a Canine Model of Atrioventricular Block

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 9 2003
PATRICIO A. FRIAS M.D.
Introduction: The aim of this study was to evaluate epicardial biventricular pacing as a means of maintaining synchronous ventricular activation in an acute canine model of AV block with normal ventricular anatomy and function. Chronic single-site ventricular pacing results in dyssynchronous ventricular activation and may contribute to ventricular dysfunction. Biventricular pacing has been used successfully in adult patients with congestive heart failure. Methods and Results: This was an acute study of open chest mongrel dogs (n = 13). ECG, left ventricular (LV), aortic, and pulmonary arterial pressures were measured. LV impedance catheters were used to assess cardiodynamics using instantaneous LV pressure-volume relations (PVR). Following radiofrequency ablation of the AV node, a temporary pacemaker was programmed 10 beats/min above the intrinsic atrial rate, with an AV interval similar to the baseline intrinsic PR interval. The pacing protocol consisted of 5-minute intervals with the following lead configurations: right atrium-right ventricular apex (RA-RVA), RA-LV apex (LVA), and RA-biventricular using combinations of four ventricular sites (RVA, RV outflow tract [RVOT], LVA, LV base [LVB]). RA-RVA was used as the experimental control. LV systolic mechanics, as measured by the slope of the end-systolic (Ees) PVR (ESPVR, mmHg/cc), was statistically greater (P < 0.05) with all modes of biventricular pacing (RA-RVA/LVA 20.0 ± 2.9, RA-RVA/LVB 18.4 ± 2.9, RA-RVOT/LVA 15.1 ± 1.8, RA-RVOT/LVB 17.6 ± 2.9) compared to single-site ventricular pacing (RA-RVA 12.8 ± 1.6). Concurrent with this improvement in myocardial performance was a shortening of the QRS duration (RA-RVA 97.7 ± 2.9 vs RA-RVA/LVA 75.7 ± 4.9, RA-RVA/LVB 70.3 ± 4.9, RA-RVOT/LVA 65.3 ± 4.4, and RA-RVOT/LVB 76.7 ± 5.9, P < 0.05). Conclusion: In this acute canine model of AV block, QRS duration shortened and LV performance improved with epicardial biventricular pacing compared to standard single-site ventricular pacing. (J Cardiovasc Electrophysiol, Vol. 14, pp. 996-1000, September 2003) [source]

International Consensus on Nomenclature and Classification of Atrial Fibrillation: A Collaborative Project of the Working Group on Arrhythmias and the Working Group of Cardiac Pacing of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 4 2003
SAMUEL LÉVY M.D.
No abstract is available for this article. [source]

Inappropriate Shock and Pacing?

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 2 2003
AMIN AL-AHMAD M.D.
[source]

Exercise is Superior to Pacing for T Wave Alternans Measurement in Subjects with Chronic Coronary Artery Disease and Left Ventricular Dysfunction

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 9 2002
ERIC J. RASHBA M.D.
Exercise vs Pacing for TWA Measurement.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. [source]

Microvolt T Wave Alternans Inducibility in Normal Newborn Puppies: Effects of Development

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 6 2002
Ph.D., SALIM F. IDRISS M.D.
T Wave Alternans in Normal Newborn Puppies.Introduction: The cause of sudden infant death syndrome is unknown, but increased cardiac vulnerability due to repolarization instability may be a contributing factor. The QT interval normally is long at birth and increases further during the first few postnatal months. Although excessive QT intervals indicate increased cardiac vulnerability in the long QT syndrome, the impact of less pronounced QT prolongation during this developmental period is unclear. In adults and older children, the ease of inducing microvolt-level T wave alternans (TWA) is used as a measure of repolarization instability and arrhythmia vulnerability. The aim of this study was to determine if TWA is inducible in normal newborn puppies. Methods and Results: Atrial pacing was performed in 15 anesthetized beagle puppies 7 to 35 days old. The pacing drive cycle length was systematically decreased in 20-msec steps from baseline until AV conduction blocked. Pacing was performed for 8 minutes at each cycle length. Three-lead ECGs were recorded continuously during the last 5 minutes of pacing at each cycle length. The recordings were analyzed off-line for the presence of microvolt-level TWA using a sensitive spectral analysis technique. Microvolt-level TWA was present in all puppies. TWA was not present at baseline but developed and increased in amplitude as heart rate increased. The threshold heart rate for TWA did not correlate with age. However, due to age-dependent changes in baseline heart rate, the 7- to 14-day-old animals needed a 50% to 78% increase in heart rate to reach threshold heart rate, whereas the oldest animals needed only a 5% to 25% increase. Conclusion: These data suggest that developmentally dependent dynamic repolarization instability exists in puppies as manifest by the inducibility of TWA. [source]