Heart Rhythm - Articles in Press

R-Wave Peak Time at DII: A New Criterion to Differentiate Between Wide Complex QRS Tachycardias - Accepted Manuscript

2010-03-08

Abstract: Background:: Differential diagnosis of wide QRS complex tachycardias using the12 lead electrocardiogram may be difficult in many clinical settings.Objectives: We sought to determine the value of the electrocardiographic lead II, specifically the duration at its beginning defined as R-Wave Peak Time (RWPT) for differentiating wide QRS complex tachycardias between ventricular and supra-ventricular tachycardias.Methods: 218 ECG with wide QRS complex tachycardias were evaluated. Two cardiologists blinded to the diagnosis measured the RWPT duration on lead II (from the isoelectric line to the point of first change in polarity) and the results were compared between VT and SVT using the EPS results as the gold standard.Results: 163 VTs had a significantly longer RWPT at DII (76.7 ± 21.7 versus 26.8 ± 9.5 ms in 55 SVT, p = 0.00001). The ROC identified a RWPT at lead II ≥ 50 ms as having a greater specificity and sensitivity to discriminate VTs from SVTs. The AUC was 0.97 (CI 95% 0.95 - 0.99), the +LR 34.8 and kappa coefficient 0.86. Bivariate analysis identified higher age in VT patients (60.7 versus 50.1 y/o, p ≤ 0.01) and wider QRS complex duration in lead II in VT patients (169.4 versus 128.3 ms, p < 0.0001). The QRS width at DII was not superior to the RWPT in diagnosing VT.Conclusion:: A R-wave peak time ≥ 50 ms at DII is a simple and highly sensitive criterion that discriminates VT from SVT in patients with wide QRS complex tachycardias.

Relationship of Common Candidate Gene Variants to Electrocardiographic T-Wave Peak to T-Wave End Interval and T-Wave Morphology Parameters - Accepted Manuscript

2010-03-08

Abstract: Background: Single-nucleotide polymorphisms (SNPs) in genes encoding cardiac ion channels and nitric oxide synthase 1 adaptor protein (NOS1AP) are associated with electrocardiographic (ECG) QT-interval duration, but the association of these SNPs with new prognostically important ECG measures of ventricular repolarization has been unknown.Objective: Our aim was to examine the relationship of SNPs to ECG T-wave peak to T-wave end (TPE) interval and T-wave morphology parameters.Methods: We studied 5,890 adults attending the Health 2000 Study, a Finnish epidemiological survey. TPE interval and four T-wave morphology parameters were measured from digital 12-lead ECGs and related to those seven SNPs showing a phenotypic effect on QT-interval duration in the Health 2000 Study population.Results: In multivariable analyses, the KCNH2K897T minor allele was associated with a 1.2 ms TPE-interval shortening ( P =.00005) and the KCNH2intronic rs3807375 minor allele was associated with a 0.8 ms TPE-interval prolongation ( P =.001), whereas the KCNE1D85N variant had no TPE-interval effect ( P =.20). NOS1AP minor alleles (rs2880058, rs4657139, rs10918594, rs10494366) were associated with shorter TPE interval (effects from 0.5 to 0.8 ms, P from .032 to .002), which resulted from their stronger effects on QTpeak than QTend interval. None of the SNPs showed a consistent association with T-wave morphology parameters.Conclusions: KCNH2K897T and rs3807375 as well as the four studied NOS1AP variants have modest effects on ECG TPE interval but are not related to T-wave morphology measures. The previously observed prognostic value of T-wave morphology parameters is unlikely to be based on these SNPs.

Total Pulmonary Vein Occlusion Complicating Pulmonary Vein Isolation: Diagnosis and Treatment - Accepted Manuscript

Lourdes R. Prieto, Yu Kawai, Sarah E. Worley — 2010-03-08

Abstract: Background: Pulmonary vein stenosis (PVS) complicating pulmonary vein isolation (PVI) can progress to total occlusion (PVO). Little is known about the accuracy of non-invasive diagnosis and treatment of PVO.Objectives: To study the diagnostic accuracy of non-invasive testing and the feasibility and outcome of percutaneous intervention for PVO.Methods: CT diagnosed and angiographically confirmed PVOs were identified from percutaneous interventions for PVS complicating PVI between 12/00-12/08. Diagnostic accuracy of CT combined with lung perfusion scan was studied. Outcome of percutaneous intervention was reviewed.Results: CT diagnosed “PVO” in 53 PVs, only 20/53 were totally occluded angiographically. True PVO had lower perfusion (4.0%) compared with CT diagnosed “PVO” (7.3%), P=0.024. Recanalization was attempted in 9 and successful in 8. Of the 8, 7 were dilated with 4.5-7 mm balloons and 1 stented primarily (7 mm). At repeat catheterization 2.9±0.8 months later, 6/7 PVs were stented to 5-10 mm. At 11.3±8.7 months follow-up, all but one PV remain patent with mean diameter 6.9±1.7 mm. Flow to the lung quadrant increased from 5.6% before recanalization to 12.2% at last follow-up (P=0.016). Symptoms improved in all but one patient.Conclusions: PVO is overestimated by CT. Quantification of lung perfusion improves diagnostic accuracy, but angiography remains the gold standard. Recanalization of PVO can be attempted when a remnant of the PV is visible. Good mid-term patency rates and improved perfusion were observed with a 2-stage approach of initial dilation and subsequent stenting. Longer follow-up and larger numbers are needed to better understand when to intervene for PVO.

The Prognostic Impact of Shocks for Clinical and Induced Arrhythmias on Morbidity and Mortality among Patients with Implantable Cardioverter-Defibrillators - Accepted Manuscript

2010-03-08

Abstract: Background: Recent investigations have demonstrated that the occurrence of implantable cardioverter defibrillator (ICD) shocks is associated with adverse long-term outcomes. These studies have emphasized that the risk is most reasonably due to arrhythmias rather than the shock itself. We sought to compare the impact of shock delivery for induced ventricular arrhythmias during implantation defibrillation threshold testing and non-invasive electrophysiology study (NIPS) to clinical shocks on long term outcomes among patients with ICDs.Methods and Results: This was a cohort evaluation of 1,372 patients undergoing ICD implantation at a tertiary hospital from December 1997 - January 2007. The probability of all-cause mortality and hospitalization for acute decompensated heart failure (ADHF) was evaluated based upon the type of ICD shock received using multivariable Cox proportional analyses. The four shock types analyzed were implantation shocks only (n=694) additional NIPS shocks only (n=319), additional appropriate shocks only (n=128), or additional inappropriate shocks only (n=104). The risk of death [adjusted HR 0.91 (95% CI 0.69 – 1.20), p=0.491] or ADHF [AHR 0.71 (95% CI 0.46 – 1.16), p=0.277] were similar between recipients of NIPS shocks and recipients of implantation shocks. Receiving an appropriate ICD shock increased the risk of death [AHR 2.09 (95% CI 1.38 – 2.69) p<0.001] and ADHF [AHR 2.40 (95% CI 1.51 – 3.81), p<0.002] as compared to implantation shocks and also increased the risk of death [AHR 2.61 (95% CI 1.86 – 3.67) p<0.001] and ADHF [AHR 2.29 (95% CI 1.33 – 3.97), p=0.003] as compared to NIPS shocks.Conclusions: ICD shocks delivered during induced ventricular arrhythmias at the time of NIPS testing does not increase the risk of death or ADHF as compared to recipients of appropriate ICD shocks. The occurrence of spontaneous arrhythmias in vulnerable substrates may explain the increased risk.

Why do Thrombi form in the Left but not the Right Atrium in Atrial Fibrillation: Differences in Platelet P-selectin Levels? - Accepted Manuscript

John M. Jennings, Raymond E. Ideker — 2010-03-04

Stereotactic Robotic Radiosurgery (CyberHeart™): A Cyber Revolution in Cardiac Ablation? - Accepted Manuscript

Renee M. Sullivan, Alexander Mazur — 2010-03-04

Dynamic and Site-Specific Impact of Ventricular Pacing On Left Ventricular Ejection Fraction - Accepted Manuscript

2010-03-04

Abstract: Background:: Some studies suggest that right ventricular (RV) pacing has an adverse impact on left ventricular ejection fraction (EF), particularly in subjects with preexisting left ventricular (LV) dysfunction, and that direct LV pacing may be relatively protective. Interactions between pacing site and EF remain unclear.Objectives:: To examine the relative impact of RV and LV pacing on EF by serial study during a period in which LV dysfunction, induced by tachypacing, was introduced and then resolved.Methods:: In each of five dogs, RV, LV and simultaneous RV+LV (BiV) pacing modes were compared to native ventricular activation: 1. prior to tachypacing (baseline), 2. weekly during a five week continuous tachypacing period, and 3. weekly during a three week post-tachypacing recovery period. At each evaluation, EF and LV contraction synchrony were assessed during each pacing mode.Results:: The decrease in EF during the tachypacing period was more pronounced during RV pacing than during native activation, LV or BiV pacing. The magnitude of this effect was correlated with a diminishment in LV contraction synchrony not observed during native activation, LV, or BiV pacing. During the post-tachypacing period, gradual reversal of these changes toward the baseline state was observed.Conclusions:: Compared to native activation, RV pacing worsens EF in a manner proportional to the severity of preexisting LV dysfunction, attributable to reduced LV contraction synchrony. In comparison, both LV and BiV pacing preserve EF and contraction synchrony.

Therapeutic hypothermia and VF storm in early repolarization syndrome - Accepted Manuscript

Rachel Bastiaenen, Paula L. Hedley, Michael Christiansen, Elijah Behr — 2010-03-04

Ablation of Long-standing Persistent Atrial Fibrillation with Multi-electrode Ablation Catheter - Accepted Manuscript

Shinsuke Miyazaki, Matthew Wright, Michel Haïssaguerre, Mélèze Hocini — 2010-03-04

Catheter Ablation of Idiopathic Left and Right Ventricular Tachycardias in the Pediatric Population Using Noncontact Mapping - Accepted Manuscript

2010-03-02

Abstract: Background: Idiopathic ventricular tachycardia (VT) in children with a structurally normal heart can cause significant morbidity and, although rare, mortality. Conventional activation and pace mapping may be limited by nonsustained tachycardia or unstable hemodynamics.Objective: The aim of this study was to assess feasibility of catheter ablation of idiopathic VT in the pediatric population guided by noncontact mapping.Methods: 20 consecutive pediatric patients with idiopathic VT underwent electrophysiologic study with the intention to use the noncontact mapping system EnSite 3000. The multielectrode balloon array was introduced into the left or right ventricle, respectively, and tachycardia was analyzed using color-coded isopotential maps as well as reconstructed unipolar electrograms on the virtual geometry. Region of origin was identified in all of them and the site of earliest activation with a QS pattern of the unipolar electrograms guided for sites of ablation.Results: Idiopathic VT originated from the RVOT in 6 patients, from the LV in 8, and from the aortic sinus cusp in 6 in this cohort with a mean age of 14.4 (4.8 - 20.9) years. Ablation was attempted in 18/20 children and was acutely successful in 17 of these 18 (94%). During mean follow-up of 2.3±1.7 years, VT recurred in three, two of them have been treated with a second procedure, resulting in an overall intermediate-term success in 16/18 (89%) children with idiopathic VT.Conclusion: Noncontact mapping can safely and effectively be used to map and guide catheter ablation of the tachycardia substrate of idiopathic VT in pediatric patients.

Congenital Long QT Syndrome and 2:1 Atrioventricular Block: An Optimistic Outcome in the Current Era - Accepted Manuscript

2010-03-02

The Epicardial Neural Ganglionated Plexus of the Ovine Heart: Anatomical Basis for Experimental Cardiac Electrophysiology and Nerve Protective Cardiac Surgery - Accepted Manuscript

2010-03-02

Abstract: Background: The sheep is routinely used in experimental cardiac electrophysiology and surgery.Objective: We aimed at (1) ascertaining the topography and architecture of the ovine epicardial neural plexus (ENP), (2) determining the relationships of the ENP with the vagal and sympathetic cardiac nerves and ganglia, and (3) evaluating gross anatomical differences and similarities among ENPs in humans, sheep and other species.Methods: The ovine ENP, extrinsic sympathetic and vagal nerves were revealed histochemically for acetylcholinesterase on whole heart and/or thorax-dissected preparations from 23 newborn lambs with subsequent examination by a stereomicroscope.Results: The intrinsic cardiac nerves extend from the venous part of the ovine heart hilum (HH) along the roots of the cranial (superior) caval and left azygos veins to both atria and ventricles via five epicardial routes; i.e. the dorsal right atrial (DRA), middle (MD), left dorsal (LD), right ventral (VR) and ventral left atrial (VLA) nerve subplexuses. Intrinsic nerves proceeding from the arterial part of the HH along the roots of the aorta and pulmonary trunk extend exclusively into the ventricles as the right and left coronary subplexuses. The DRA, RV, and MD subplexuses receive the main extrinsic neural input from the right cervicothoracic and the right thoracic sympathetic T2, T3 ganglia, as well as from the right vagal nerve. The LD is supplied by sizeable extrinsic nerves from the left thoracic T4-T6 sympathetic ganglia and the left vagal nerve. Sheep hearts contained on average 769±52 epicardial ganglia. Cumulative areas of epicardial ganglia on the root of the cranial vena cava and on the wall of the coronary sinus were the largest of all regions (p<0.05).Conclusion: Despite substantial interindividual variability in the morphology of the ovine ENP, the right-sided epicardial neural subplexuses supplying the sinuatrial and atrioventricular nodes are mostly concentrated at a fat pad between the right pulmonary veins and the cranial vena cava. This is in sharp contrast with a solely left lateral neural input to the human atrioventricular node which extends mainly from the LD and MD subplexuses. The abundance of epicardial ganglia distributed widely along the ovine ventricular nerves over respectable distances below the coronary groove implies a distinctive neural control of the ventricles in human and sheep hearts.

EP News: Basic and Translational - Uncorrected Proof

Peng-Sheng Chen — 2010-02-26

Schnabel et al (Circulation 2010;121:200, PMID 20048208) studied 3,120 Framingham cohort participants and related 10 biomarkers to incident atrial fibrillation (AF, n = 209) over a median follow-up of 9.7 years. In multivariable-adjusted analyses, the biomarker panel was associated with incident AF. In stepwise-selection models, log-transformed B-type natriuretic peptide (BNP) and C-reactive protein were chosen. Addition of BNP to variables recently combined in a risk score for AF increased the C-statistic and showed an integrated discrimination improvement. Combined analysis of BNP and C-reactive protein did not appreciably improve risk prediction over the model that incorporated BNP in addition to the risk factors. The authors conclude that BNP is a predictor of incident AF that improves risk stratification based on well-established clinical risk factors.

EP News: Clinical - Uncorrected Proof

N.A. Mark Estes — 2010-02-26

Haugaa et al (Europace 2010;Epub ahead of print, PMID 20106799) investigated exercise-induced arrhythmias and efficacy of beta-blocker (BB) treatment in mutation-positive family members with catecholaminergic polymorphic ventricular tachycardia (CPVT). Relatives of six unrelated CPVT patients were tested for a mutation in the ryanodine receptor-2 gene. Mutation carriers underwent exercise testing at baseline and after 3 months of BB therapy at the highest tolerable dose. Exercise-induced ventricular arrhythmias developed in 23 of the 30 mutation-positive family members. Previously undiagnosed CPVT-related symptoms were reported by 8 subjects. With BB treatment, exercise-induced arrhythmias occurred at a lower heart rate (117 bpm vs 135 bpm, P = .02) but at similar workload (P = .78). BB treatment suppressed exercise-induced nonsustained VT in 3 of the 4 patients with this arrhythmia, but less severe arrhythmias were unchanged. One patient died during follow-up. The authors conclude that the exercise test revealed a high prevalence of arrhythmias in CPVT mutation carriers. BB therapy suppressed the most severe exercise-induced arrhythmias, but less severe arrhythmias occurred at a lower heart rate.

ICD Shocks : Not just the “Straw That Broke The Camel’s Back” - Accepted Manuscript

Harikrishna Tandri — 2010-02-26

Identification of a high Risk Population for Esophageal Injury during Radiofrequency Catheter Ablation of Atrial Fibrillation: Procedural and Anatomical Considerations - Accepted Manuscript

2010-02-26

Abstract: Background:: Atrio-esophageal fistula is an uncommon but life-threatening complication of atrial fibrillation (AF) ablation. Esophageal ulcerations (ESUL) have been proposed to be potential precursor lesions.Objectives:: The purpose of our study was to prospectively investigate the incidence of ESUL in a large patient population undergoing radiofrequency catheter ablation (RFA). Additionally, we aimed to link demographic data and lesion sets with anatomical information given by multislice computed tomography imaging and correlate these data with the development of ESUL.Methods:: 267 patients were included in this study consecutively screening all individuals for evidence of ESUL 24 hours after RFA of AF by endoscopy of the esophagus. A standardized ablation approach using 25W energy maximum at the posterior left atrial (LA) wall without esophagus visualization, temperature monitoring, or intracardiac ultrasound was performed.Results:: In total, we found 2.2% of patients (6/267) presenting with ESUL. Parameters exposing a specific patient to risk for developing ESUL in univariate analysis were persistent AF (5/95, p=0.023), additional lines performed (roofline: 6/114, p=0.006; LA isthmus: 4/49, p=0.011; Coronary Sinus: 5/66, p=0.004), and LA enlargement (p=0.001) leading to “sandwiching” of the esophagus between the LA and thoracic spine. Multivariate analysis revealed LA to esophagus distance as the only significant risk factor.Conclusion:: This study is the first to link anatomical information and procedural considerations to the development of ESUL in radiofrequency ablation for AF. Furthermore, it reveals the correlation and individual impact of these factors. No single patient with pulmonary vein isolation alone developed ESUL while performing a standardized ablation approach.

Electrophysiological Characteristics of the Marshall Bundle in Humans - Accepted Manuscript

2010-02-26

Abstract: Background: Marshall bundles (MBs) are the muscle bundles within the ligament of Marshall.Objective: To study the electrophysiological characteristics of the MB and the anatomical connections between MB and left atrium (LA) in patients with persistent atrial fibrillation (AF).Methods: We enrolled 72 patients (M: F=59:13, age 59.9±9.4 years) who underwent MB mapping and ablation for AF. MB mapping was done via endocardial or epicardial approach during sinus rhythm, and AF.Results: Recordings were successful in 64 of 72 patients (89%). A single connection was noted in 11/64 patients between the MB and the coronary sinus (CS) muscle sleeves. The MB recordings exhibited distinct MB potentials with a proximal to distal activation pattern during sinus rhythm. During AF, organized passive activations and dissociated slow MB ectopic activities were commonly observed in this type of connection. Double connections to both CS and left atrium around left pulmonary veins were noted in 23/64 patients (36%). After the ablation of the distal connection, MB recording showed typical double potentials as in single connection. Multiple connections were noted in 30/64 patients (47%). During sinus rhythm, the earliest activation was in the middle of the MB. The activation patterns were irregular and variable in each patient. During AF, rapid and fractionated complex activations were noted in all patients of this group.Conclusion: We documented three different types of MB-LA connections. Rapid and fractionated activations were most commonly observed in the MB that had multiple LA connections.

Atrioventricular Conduction and Cardiovascular Mortality: Assessment of Recovery PR Interval Is Superior To Pre-Exercise Measurement - Accepted Manuscript

2010-02-26

Abstract: Background: Prolonged electrocardiographic PR interval at rest has been considered a benign phenomenon until recently.Objective: We hypothesized that measurement of PR interval during recovery from physical exertion could improve cardiovascular mortality risk stratification, as it would track the dynamic influences of homeostatic mechanisms controlling atrioventricular (AV) conduction.Methods: A total of 1979 patients (1244 men and 735 women) with clinically indicated bicycle ergometer tests enrolled in the Finnish Cardiovascular Study (FINCAVAS) were included in the study. PR interval was measured at 1 min prior to and at 2 min after exercise.Results: During the mean follow-up period of 47 months (interquartile range 37-59 months), 50 cardiovascular deaths (endpoint) were registered. The unadjusted hazard ratios (HR) in Cox regression analyses were significant for both continuous PR interval and first-degree atrioventricular (AV) block for pre- and post-exercise phases. After adjustment for standard markers, the PR interval for 20 ms increments (HR 1.17, p=0.117) and first-degree AV block (HR 1.85, p=0.138) during the pre-exercise phase were not prognostic. However, during recovery from exercise, prolonged AV conduction achieved significance both in continuous (HR 1.29, p=0.006) and dichotomized analyses (HR 2.41, p=0.045).Conclusion: The PR interval prior to exercise is not a robust risk stratifier for cardiovascular death during a four-year follow-up. Post-exercise assessment of AV conduction may offer improved prediction because of functional abnormalities that become manifest only during this physiologic challenge to the heart.

Abnormal right atrial pouch in a patient with heart failure and cavotricuspid isthmus dependent atrial flutter - Accepted Manuscript

Antonio Sorgente, Tiziano Moccetti — 2010-02-26

Continuing Warfarin Therapy Is Superior to Interrupting Warfarin With or Without Bridging Anticoagulation Therapy in Patients Undergoing Pacemaker and Defibrillator Implantation - Accepted Manuscript

2010-02-22

Abstract: Background:: Current guidelines recommend stopping oral anticoagulation and starting bridging anticoagulation with intravenous heparin or subcutaneous enoxaparin for implanting pacemaker or defibrillator in patients at moderate or high risk for thromboembolic events. A limited body of literature suggests that device surgery without cessation of oral anticoagulation may be feasible.Objective:: This study was designed to evaluate the safety of device surgery in orally anticoagulated patients without interruption of warfarin therapy.Methods:: We performed a retrospective study of 459 consecutive patients on chronic warfarin therapy who underwent device surgery from April 2004 to September 2008. Warfarin was continued in 222 patients during the perioperative period. Warfarin was temporarily held and bridging therapy was administered in 123 patients. Warfarin was temporarily held without bridging therapy in 114 patients.Results:: There were no significant differences in age, sex and risk factors for thromboembolism in the three groups. Patients continuing warfarin had a lower incidence of pocket hematoma (p=0.004) and a shorter hospital stay (p<0.0001) compared to the bridging group. Holding warfarin without bridging is associated with a higher incidence of transient ischemic attacks (p=0.01).Conclusion:: Temporarily interrupting anticoagulation is associated with increased thromboembolic events, whereas cessation of warfarin with bridging anticoagulation is associated with a higher rate of pocket hematoma and a longer hospital stay. Continuing warfarin with a therapeutic international normalized ratio (INR) appears to be a safe and cost-effective approach for implanting pacemaker or defibrillator in patients with moderate to high thromboembolic risk.

Upstream therapy in atrial fibrillation: Traveling up the river to find the source - Uncorrected Proof

Wim Anné, Mattias Duytschaever — 2010-02-22

Like other arrhythmias, atrial fibrillation (AF) is most often treated with direct ion channel blockers or catheter ablation. In many patients, however, a “structural substrate” of AF predominates a “pure electrical substrate.” The structural substrate of AF is due to preexistent underlying heart disease, aging, or the arrhythmia itself. Biopsies in patients with AF revealed that structural changes consist of extracellular matrix changes (fibrosis, inflammation, amyloidosis) and cellular changes (hypertrophy, loss of myofibrils and replacement with glycogen, changes in size and shape of mitochondria). The above changes may lead to heterogeneity in electrical properties such as areas of conduction slowing, zones of conduction block, and zones of (electrical) scarring, making the atria prone to the development of AF. The development of the structural substrate for AF may take years and even decades. These findings suggest that there is a considerable window of opportunity for preventing the onset or modifying the natural course of AF. Possible candidate drugs that interfere with structural remodeling are those interacting with fibrogenesis and inflammation: blockers of the renin-angiotensin pathway, statins, and polyunsaturated fatty-acids (PUFA), as described in the present paper.

The Infinite Value in Subcutaneous Defibrillation - Accepted Manuscript

Martin C. Burke — 2010-02-22

A Small Epidemic of “Frozen” Pacemaker and Defibrillator Leads - Accepted Manuscript

Elizabeth S. Kaufman — 2010-02-22

High Frequency Vagal Stimulation Pacing fast to slow down - Accepted Manuscript

Stephen Shorofsky — 2010-02-22

The A, B, C’s of Sudden Infant Death Syndrome (SIDS): An Electrical Disorder? - Accepted Manuscript

Jeffrey A. Towbin — 2010-02-22

Mortality and Safety of Catheter Ablation for Antiarrhythmic Drug Refractory Ventricular Tachycardia in Elderly Patients with Coronary Artery Disease - Accepted Manuscript

2010-02-17

Abstract: Background:: As the population ages, recurrent ventricular tachycardia (VT) is increasingly encountered in elderly patients with ischemic heart disease. Radiofrequency catheter ablation (RFCA) is useful for reducing VT therapies in patients with implantable defibrillators. The utility of RFCA in the elderly is not well defined.Objective:: The purpose of this study was to evaluate the prognosis and safety of RFCA of post-infarct VT in elderly patients.Methods:: RFCA was performed in 285 consecutive patients with recurrent post-infarct VT refractory to antiarrhythmic drugs. Mortality and outcomes were compared for the elderly (age: ≥75 years, n=72) and younger group (age: <75 years, n=213).Results:: The groups were similar in their baseline characteristics except for more females in the elderly group (20.8% vs 10.8%, p=0.03). Inducible VTs were abolished or modified in 79.2% of the elderly and 87.8% of the younger group (p=0.12). Major complications occurred in 5.6% of the elderly and 2.3% of younger patients (p=0.48). Periprocedural mortality was similar between both groups (2/72 in elderly and 9/213 in younger group, p=0.74). During a mean follow-up period of 42±33 months, 50.0% of the elderly and 35.2% of the younger group died (p=0.08). No VT was observed in 63.9% of the elderly and 60.1% of the younger patients, respectively (mean follow-up period: 18±24 months, p=0.80).Conclusion:: Outcomes of catheter ablation are similar for selected elderly and younger patients. Advanced age should not preclude ablation when recurrent VT is adversely affecting quality of life in elderly patients who otherwise have a reasonable expectation for survival.

Safety and efficacy of a new MRI compatible pacing system: early results of a prospective comparison with conventional dual-chamber implant outcomes - Accepted Manuscript

2010-02-17

Abstract: Background: A new pacing system has been designed and pre-clinically tested for safe use in the MRI environment. However, no previous experience with this innovative system has yet been reported.Objective: This study aims to verify the safety and effectiveness of this newly designed system compared to conventional DDD implant outcomes.Methods: Over a period of 11 months, 107 consecutive patients (71 males, age 72.6 ± 8.5) were implanted either with the MRI-system (n=50; MRI group) or with a dual-chamber and active-fixation leads (Medtronic 4076) non-MRI system (n=57; DDD group). Data were collected at implant and during postoperative follow-up at 1,3, 6 and 12 months. Procedural and fluoroscopic time at implant, as well as lead measurements, handling characteristics and procedural-related complications were prospectively analyzed.Results: The implantation success rate in both groups was 100%. Cephalic access was 63% for MRI patients and 70% for DDD patients (p=NS). Follow-up was obtained in all patients (median 6.8 months; range 3 to 12). At implant and at the end of follow-up, we found acceptable stimulation thresholds, sensing, and impedance. There were no cases of high pacing thresholds or inadequate sensing. There were no complications and no patient experienced subsequent lead displacement.Conclusions: This prospective, controlled study provides strong evidence that feasibility and safety of this novel technology compares favorably with the conventional technique.

Non-Invasive Stereotactic Radiosurgery (CyberHeart™) for the Creation of Ablation Lesions in the Atrium - Accepted Manuscript

2010-02-15

Abstract: Background: This first in the literature study examined the experimental feasibility of a non-invasive method using Stereotactic Robotic Radiosurgery (SRS) to create cardiac lesions.Method: Sixteen (16) Hanford-Sinclair mini swine (40-70kg) were studied under general anesthetic. Baseline CT scans were performed followed by electroanatomical mapping using CARTO® (J & J Biosense Webster, Diamond Bar, CA. The animals then underwent SRS using the Cyberheart® system with predetermined targets at the cavo-tricuspid isthmus, AV node, the pulmonary vein- left atrial junction, or the left atrial appendage. The swine underwent investigation 25 days to 196 days following treatment, with repeat electroanatomic voltage mapping, and transesophageal echocardiography when possible. Finally the animals were sacrificed and pathology specimens taken.Results: The dose ranging suggested that 25 Gy was needed to produce an electrophysiologic effect. The time course showed an electrophysiologic effect consistently by 90 days. It was feasible to produce bidirectional cavo-tricuspid isthmus block, and AV nodal conduction block. The pulmonary vein-left atrial junction and left atrial appendage showed marked reduction in voltage to less than .05mV. No spontaneous arrhythmias were observed. Pathology showed no evidence of radiation damage outside the target. Histology at the target sites was consistent with x-beam radiation.Conclusion: SRS can produce cavo-tricuspid isthmus block, AV nodal block, and significant decreased voltage at the pulmonary vein-left atrial junction. No other organ damage was seen. This demonstrates the feasibility of this non-invasive treatment method to create cardiac lesions and this approach merits further investigation in the treatment of arrhythmias.

Atrioventricular Nodal Ablation Predicts Survival Benefit in Patients with Atrial Fibrillation and Receiving Cardiac Resynchronization Therapy - Accepted Manuscript

2010-02-15

Abstract: Background:: Cardiac resynchronization therapy (CRT) benefits patients with advanced heart failure. The role of atrioventricular node (AVN) ablation to improve CRT outcomes, including survival benefit in CRT recipients with atrial fibrillation (AF), is uncertain.Methods:: Of 154 patients who had AF and received CRT-D, 45 (29%) underwent AVN-ABL (+AVN-ABL group), while 109 (71%) received drug therapy for rate control during CRT (–AVN-ABL group). New York Heart Association (NYHA) class, electrocardiogram, and echocardiography were assessed before and after CRT. Survival data were obtained from the national death and location database (Accruint).Results:: CRT comparably improved left ventricular ejection fraction (8.1±10.7% vs 6.8±9.6%, P=0.49) and LV end-diastolic diameter (–2.1±5.9 mm vs –2.1±6.7 mm, P=0.74) in both +AVN-ABL and –AVN-ABL groups. Improvement in NYHA class was significantly greater in +AVN-ABL group than in –AVN-ABL group (–0.7±0.8 vs –0.4±0.8, P=0.04). Survival estimates at 2 years were 96.0% (95% confidence interval [CI], 88.6%-100%) for the +AVN-ABL group and 76.5% (95% CI, 68.1%-85.8%) for the –AVN-ABL group (P=0.008). AVN ablation was independently associated with survival benefit from death (hazard ratio [HR] 0.13; 95% CI, 0.03-0.58, P=0.007) and from combined death, heart transplant, and left ventricular assisted device (HR 0.19; 95% CI, 0.06-0.62, P=0.006) after CRT.Conclusion:: Among patients with atrial fibrillation and heart failure receiving CRT, AVN ablation for definitive biventricular pacing provides greater improvement in NYHA class and survival benefit. Larger-scale randomized trials are needed to assess the clinical and survival outcomes of this therapy.

Microvolt T-wave Alternans and Electrophysiological Testing Predict Distinct Arrhythmia Substrates: Implications for Identifying Patients at Risk for Sudden Cardiac Death - Accepted Manuscript

Guy Amit, David S. Rosenbaum, Dennis M. Super, Otto Costantini — 2010-02-15

Abstract: Objectives:: Although microvolt T-wave Alternans (MTWA) and electrophysiological study (EPS) are independent markers for sudden cardiac death (SCD), the Alternans Before Cardioverter Defibrillator (ABCD) Trial found the combination to be more predictive than either one alone. We hypothesized that the two tests measured different elements of the arrhythmogenic substrate and, therefore, predict distinct arrhythmia outcomes.Background:: There is a need for better risk stratification of patients receiving implantable cardioverter defibrillator (ICD) for the primary prevention of sudden cardiac death.Methods:: The ABCD Trial enrolled 566 patients with ischemic cardiomyopathy, left ventricular ejection fraction (LVEF) ≤ 0.40, and non-sustained ventricular tachycardia. All patients underwent both a MTWA test and an EPS. The performance of MTWA and EPS in predicting a Stable Monomorphic Ventricular Tachyarrhythmic Events (S-VTE) vs. Unstable Ventricular Tachyarrhythmic Events (U-VTE), defined as either polymorphic ventricular tachycardia (PVT) or ventricular fibrillation (VF), was analyzed Using Kaplan-Meier event rates and the log rank test.Results:: MTWA and EPS were abnormal in 71% and 39% of patients, respectively. There were 28 S-VTEs and 10 U-VTEs. MTWA was predictive of U-VTEs (event rate of 2.7% in abnormals vs. 0% in normals; p=0.04), while EPS was not (1.5% vs. 3.2%; p=0.55). In contrast, EPS predicted S-VTEs (9.7% vs. 2.2%; p<0.01), but MTWA did not (5.5% vs. 4.4%; p=0.57). While the extent of LV contractile dysfunction alone (LVEF ≤ 0.30 vs. LVEF 0.31-0.40) did not predict events, MTWA predicted events better than EPS in subjects with LVEF ≤0.30. By contrast, EPS predicted events better than MTWA test in subjects with LVEF > 0.30.Conclusions:: These data suggest that EPS and MTWA identify distinct arrhythmogenic substrates, and when used in combination may better predict the complex electro-anatomical substrates which underlie the risk for SCD.

The molecular mechanisms of adrenergic stimulation in the heart - Accepted Manuscript

Kevin J. Sampson, Robert S. Kass — 2010-02-15

Abstract: Increased cardiac output in response to β-adrenergic receptor (β-AR) stimulation is achieved by rapid alteration of the activity of cardiac ion channels, pumps, and exchangers. Over the past decade, the discovery of macromolecular complexes that include the ion channels and pumps and the kinases that control their level of phosphorylation have led to an increased understanding of the molecular mechanisms behind the cardiac adrenergic response. This increased understanding has led to the discovery of a new long QT gene encoding an accessory protein in one of these macromolecular complexes. The following provides a brief review of the major components of the β-adrenergic pathway in the heart and discusses the direction of current and future research.

Functional anatomy of intrathoracic neurons innervating the atria and ventricles - Accepted Manuscript

J.A. Armour — 2010-02-15

Uncorrected Proof

Kenneth Stein, Arjun Sharma, Robert Harguth — 2010-02-15

Germano et al recently published a case report alleging that clinical observations of oversensing and high impedance in a Boston Scientific Model N119 CRT-D were caused by header case separation. We are disappointed that this manuscript was submitted and accepted for publication before engineering analysis of the explanted device. Boston Scientific has completed laboratory analysis and discussed the results with the lead author. In brief, we determined that although the header bond was weakened, device function was not compromised and that the weakened header bond could not have caused the oversensing and impedance changes reported. This letter seeks to correct errors in the manuscript and clarify the observed rate of weakened header bonds in the subcutaneous implant population:

Uncorrected Proof

Joseph J. Germano, William H. Maisel — 2010-02-15

The case report describing the malfunction of a Boston Scientific Cognis cardiac resynchronization therapy implantable defibrillator contains no “errors.” The patient described in the case report experienced repeated noise that was only alleviated by replacing the defective device. The visible header abnormality was confirmed by manufacturer analysis. Bench testing yields important insights into device function, but its limitations must be recognized. For example, Boston Scientific's own bench testing initially failed to detect the weakened header bonds. In this case, manufacturer analysis has failed to explain the observed anomalous device behavior.

Ion Channel Trafficking: A New Therapeutic Horizon for Atrial Fibrillation - Accepted Manuscript

Sarah M. Schumacher, Jeffrey R. Martens — 2010-02-15

Abstract: Atrial fibrillation (AF) is a common cardiac arrhythmia with potentially life-threatening complications. Drug therapies for treatment of AF that seek long-term maintenance of normal sinus rhythm remain elusive due in large part to proarrhythmic ventricular actions. Kv1.5, which underlies the atrial specific IKur current, is a major focus of research efforts seeking new therapeutic strategies and targets. Recent work has shown a novel effect of antiarrhythmic drugs where compounds that block Kv1.5 channel current can also alter ion channel trafficking. This work further suggests that the pleiotropic effects of antiarrhythmic drugs may be separable. Although this highlights the therapeutic potential for selective manipulation of ion channel surface density, it also reveals an uncertainty regarding specificity of modulating trafficking pathways without risk of off-target effects. Future studies may show that specific alteration of Kv1.5 trafficking can overcome the proarrhythmic limitations of current pharmacotherapy and provide an effective method for long-term cardioversion in AF.

Uncorrected Proof

Kyndaron Reinier, Sumeet S. Chugh — 2010-02-12

We thank Dr. Wu for her comments in response to our population-based analysis of sudden death in children from the Oregon Sudden Unexpected Death Study (Oregon SUDS). In her letter, Dr. Wu asserts that the denominators used in our study were different from those used in previous studies of pediatric sudden death; therefore, she recalculates an incidence rate for pediatric sudden death using data from Oregon SUDS and suggests that the annual incidence of sudden death in our study is much higher than reported in previous studies.

Early repolarization and ventricular fibrillation: Vagally familiar? - Uncorrected Proof

Gil J. Gross — 2010-02-12

In an age characterized by the rapid emergence of dazzling new biomedical technology, standard surface ECG arguably should have been relegated long ago to the status of an anachronistic curiosity. Instead, it continues to present cardiologists with unexpected intellectual challenges and clinical conundrums. The latest of these is the “old/new” phenomenon of “early repolarization,” a widely recognized ECG pattern, first noted more than 60 years ago, whose central feature is inferolateral lead J-point elevation.

Ten Questions: Understanding ethical issues, ICD, and DNR orders: An obstacle to imminent death? - Accepted Manuscript

Michelle A. Mullen, Robert M. Gow — 2010-02-12

Neural modulation of ion channels in cardiac arrhythmias: clinical implications and future investigations - Accepted Manuscript

Gildas Loussouarn, Isabelle Baró — 2010-02-08

Uncorrected Proof

Mei-Hwan Wu — 2010-02-08

We read with interest the article entitled “Population-based analysis of sudden death in children: the Oregon Sudden Unexpected Death Study,” in the November 2009 issue of Heart Rhythm. Chugh et al conducted a nice prospective study from 2002 to 2005 in Multnomah County, Oregon (population 660,486), to determine an incidence rate of sudden death (SD) in a pediatric population. They found 33 children met the criteria for SD (58% female; median age 0.37 years, range 0.03–12.3 years), yielding an annual incidence per 100,000 population of 1.7 [95% confidence interval (CI) 1.1–2.3] and an annual incidence per 100,000 children of 7.5 (95% CI 5.1–10.5). They concluded that this incidence was closer to the lower estimate for pediatric SD reported in previous studies (0.8–6.2/100,000) and was in agreement with a study by Driscoll and Edwards.

Weakened implantable cardioverter-defibrillator header bond: Abnormality not limited to subpectoral implants - Uncorrected Proof

Joseph J. Germano, Alicia Darge, William H. Maisel — 2010-02-04

In December 2009, Boston Scientific (Natick, MA) issued a product advisory reporting that mechanical stress associated with subpectoral implantable cardioverter-defibrillator (ICD) implantation may weaken the bond between the header and the titanium case in Cognis cardiac resynchronization therapy defibrillators (CRT-Ds) and Teligen ICDs. Boston Scientific specifically noted that the product advisory did not affect subcutaneous implants.

Cardiac resynchronization therapy: How far is too far? - Uncorrected Proof

Matthew Ortman, Daniel R. Frisch — 2010-02-04

There is unequivocal evidence that cardiac resynchronization therapy (CRT) improves heart failure symptoms and mortality in selected populations. However, for reasons that are not completely defined, up to one-third of patients do not respond to therapy. There is a general consensus that the radial position of the left ventricular (LV) lead in a lateral or posterolateral location is preferable, but studies have questioned the significance of LV lead position entirely. There has been little focus on the longitudinal position of the LV lead, despite the fact that plausible mechanisms, the delayed inferobasal LV activation seen in left bundle branch block and the hemodynamic benefit seen with increased right ventricular-LV interelectrode distance, for example, can explain the potential advantage of a basal location.

New hopes in the echocardiography of cardiac resynchronization therapy? Merits of a combined assessment of left ventricular dyssynchrony and contractility - Uncorrected Proof

Erwan Donal, Christophe Leclercq, J.-Claude Daubert — 2010-02-04

Cardiac resynchronization therapy (CRT) is an effective therapy for patients presenting with heart failure due to left ventricular (LV) systolic dysfunction and prominent intraventricular conduction delays. The most recent trials of CRT (REVERSE and MADIT CRT) have confirmed the importance of the baseline QRS duration as well as its shortening during biventricular stimulation. However, the role played by imaging techniques, echocardiography in particular, in the selection of candidates for CRT and optimization of leads implantation remains a subject of major controversy.

Atrial Platelet Reactivity in Patients with Atrial Fibrillation - Accepted Manuscript

2010-02-04

Abstract: Background:: Atrial fibrillation (AF) is associated with an increased risk of thrombus formation in the left but not the right atrium. The mechanisms underlying this differential effect on the atria are unknown.Objective:: To examine whether there are atrial specific differences in platelet activation in patients with AF.Methods:: 19 patients (13 males: 60±2 years) with AF undergoing ablation in sinus rhythm were studied. Blood samples were obtained at the start of the procedure from the left and right atria, and the femoral vein and analysed by whole blood flow cytometry for expressions of platelet P-selectin (CD62P), vitronectin receptor (CD51/61) and active glycoprotein IIb/IIIa receptor (PAC-1). Platelet aggregation was evaluated utilizing ADP-induced whole blood impedance aggregometry. We also studied 7 patients with left sided accessory pathway as a reference group for the effect of transseptal puncture on platelet reactivity.Results:: Platelet P-selectin levels were significantly elevated in the left atrium compared to the right atrium (10.2±2.5%versus 8.6±2.3%; p<0.05). CD51/61 and PAC-1 levels did not differ between sampling sites. ADP-induced platelet aggregation was significantly higher in the left atrium compared to the right atrium and femoral vein (p<0.05 for both). Platelet P-selectin levels and ADP-induced platelet aggregation did not differ between sampling site in the reference group.Conclusion:: In patients with AF, left atrial platelet reactivity is increased compared to the right atria and peripheral circulation. These data suggest that the presence of chamber specific platelet activation may in part explain the propensity to form left atrial thrombus in patients with AF.

Vagal tone augmentation to the atrioventricular node in humans: Efficacy and safety of burst endocardial stimulation - Uncorrected Proof

2010-02-01

Background: Control of atrioventricular (AV) nodal conduction by endocardial stimulation of efferent AV nodal vagal fibers [atrioventricular nodal vagal stimulation (AVNS)] is a promising approach for long-term device-based modulation of ventricular rate during atrial fibrillation (AF). However, few data on the efficacy of AVNS delivered as high-frequency stimulus packages (burst AVNS) in humans are available.Objective: The purpose of this study was to determine whether burst AVNS can to modulate AV nodal conduction during AF and whether burst AVNS delivered during sinus rhythm (SR) in the effective atrial refractory period allows safe implantation of a permanent lead in a position suitable for AVNS.Methods: Twenty patients (10 in SR and 10 in AF) who were candidates for dual-chamber pacemaker implantation for sick sinus syndrome were enrolled in the study. The posteroseptal right atrium was mapped to identify a location at which burst AVNS would achieve AV nodal conduction modulation (lengthening of PR interval in SR and reduction of ventricular rate in AF). Subsequently, a lead was screwed in at that site and burst stimulation (pulse rate 50 Hz, burst duration 180 ms) was delivered at different burst rates, pulse durations, and amplitudes.Results: In all SR patients, PR-interval prolongation was evoked at 90 and 120 bursts/minute with pulse durations ≤1 ms. Specifically, the mean voltages required to obtain PR-interval prolongation and advanced AV block were 4.3 ± 2.2 V and 5.4 ± 1.8 V (at 90 bursts/minute and 1 ms), respectively. Similarly, ventricular rate reduction was obtained in all AF patients, starting from 90 bursts/minute and 0.5-ms pulse duration (at 5.4 ± 1.8 V). Ventricular arrhythmias were never induced during AVNS.Conclusion: Endocardial right atrial burst AVNS reduces ventricular rate during AF. Burst AVNS delivered during SR in the effective atrial refractory period allows optimization of lead positioning for AVNS.

Finite element modeling of subcutaneous implantable defibrillator electrodes in an adult torso - Accepted Manuscript

2010-02-01

Abstract: Background:: Total subcutaneous implantable subcutaneous defibrillators are in development, but optimal electrode configurations are not known.Objective:: We used image-based finite element models (FEM) to predict the myocardial electric field generated during defibrillation shocks (pseudo-DFT) in a wide variety of reported and innovative subcutaneous electrode positions, to determine factors affecting optimal lead positions for subcutaneous ICDs (S-ICD).Methods:: An image-based FEM of an adult male was used to predict pseudo-DFTs across a wide range of technically feasible S-ICD electrode placements. Generator location, lead location, length, geometry and orientation, and spatial relation of electrodes to ventricular mass were systematically varied. Best electrode configurations were determined, and spatial factors contributing to low pseudo-DFTs were identified using regression and general linear models.Results:: 122 single-electrode/array configurations and 28 dual-electrode configurations were simulated. Pseudo-DFTs for single-electrode orientations ranged from 0.60 – 16.0 (mean 2.65 ± 2.48) times that predicted for the base case, an anterior posterior configuration recently tested clinically. 32/150 tested configurations (21%) had pseudo-DFT ratios ≤ 1, indicating the possibility of multiple novel, efficient, and clinically relevant orientations. Favorable alignment of lead-generator vector with ventricular myocardium and increased lead length were the most important factors correlated with pseudo-DFT, accounting for 70% of the predicted variation (R2=0.70, each factor p <0.05) in a combined general linear model in which parameter estimates were calculated for each factor.Conclusions:: Further exploration of novel and efficient electrode configurations may be of value in the development of the S-ICD technologies and implant procedure. FEM modeling suggests that the choice of configurations which maximizes shock vector alignment with the center of myocardial mass and use of longer leads is more likely to result in lower DFT.

Sudden Infant Death Syndrome-Associated Mutations in the Sodium Channel Beta Subunits - Accepted Manuscript

2010-02-01

Abstract: Background:: Approximately 10% of sudden infant death syndrome (SIDS) may stem from potentially lethal cardiac channelopathies, with approximately half of channelopathic SIDS involving the NaV1.5 cardiac sodium channel. Recently, NaV beta subunits have been implicated in various cardiac arrhythmias. Thus, the four genes encoding NaV beta subunits represent plausible candidate genes for SIDS.Objective:: To determine the spectrum, prevalence and functional consequences of sodium channel beta subunit mutations in a SIDS cohort.Methods:: In this IRB-approved study, mutational analysis of the 4 beta subunit genes: SCN1B – 4B was performed using PCR, DHPLC, and direct DNA sequencing of DNA derived from 292 SIDS cases. Engineered mutations were co-expressed with SCN5A in HEK 293 cells, and whole cell patch clamped. One of the putative SIDS-associated mutations was similarly studied in adenovirally transduced adult rat ventricular myocytes.Results:: 3 rare (absent in 200-800 reference alleles) missense mutations (β3-V36M, β3-V54G and β4-S206L) were identified in 3/292 SIDS cases. Compared to SCN5A+β3-WT, β3-V36M significantly decreased peak I Na and increased late I Na while β3-V54G resulted in a marked loss-of-function. β4-S206L accentuated late I Na and positively shifted the midpoint of inactivation compared to SCN5A+β4-WT. In native cardiomyocytes, β4-S206L accentuated late I Na and increased the ventricular action potential duration (APD) compared to β4-WT.Conclusion:: This study provides the first molecular and functional evidence to implicate the NaV beta subunits in SIDS pathogenesis. Altered NaV1.5 sodium channel function due to beta subunit mutations may account for the molecular pathogenic mechanism underlying approximately 1% of SIDS.

Is verapamil a double-edged sword in rate control of paroxysmal atrial fibrillation? - Uncorrected Proof

M.J. Pekka Raatikainen — 2010-02-01

Over the last decade, remarkable progress has been made in the field of atrial fibrillation (AF) pathophysiology and management. There is no doubt that radiofrequency catheter ablation therapy improves the quality of life and left ventricular function in patients with symptomatic AF by improving the maintenance of sinus rhythm. A new antiarrhythmic agent, dronedarone, was recently shown to reduce the composite outcome of cardiovascular hospitalization and death in patients with AF. Moreover, novel approaches such as the dominant frequency (DF) analysis of atrial electrograms have offered clinicians a better insight into the pathogenesis of AF. Despite these advancements, long-term maintenance of sinus rhythm is challenging, and persistent or permanent AF still develops in many patients. In these cases, control of the ventricular rate has an essential role in alleviating the symptoms and preventing the development of tachycardia-induced cardiomyopathy.

Discordance of complex fractionated atrial electrograms and the dominant frequency within the superior vena cava - Uncorrected Proof

Shih-Yu Huang, Shih-Lin Chang, Yenn-Jiang Lin, Shih-Ann Chen — 2010-02-01

A 68-year-old woman underwent radiofrequency ablation for symptomatic drug-refractory paroxysmal atrial fibrillation. The intracardiac electrograms showed that the most rapid activation site was located at the superior vena cava (SVC) ostium and showed 2:1 block (, signal 1) and conducted to the rest of the atrium during atrial fibrillation (signal 3). The electrogram at the ostium of the coronary sinus is shown by CSO. Substrate mapping using a NavX system (St. Jude Medical, Irvine, California) during atrial fibrillation showed that the highest dominant frequency (DF) site was located at the anterior SVC ostium (signal 1), and complex fractionated atrial electrograms with a fractional interval of 46 ms were observed at the boundary of the SVC ostium (signal 2). The fractional interval of complex fractionated atrial electrograms was based on the mean interval between the multiple, discrete deflections during the atrial fibrillation over a 5-s recording period. Of note, the discordance between the DF site and complex fractionated atrial electrograms site was observed. After successful isolation of the SVC, performed with a Cool-Path irrigated catheter (St. Jude Medical) connected to an EPT-1000 generator (EP technologies, Boston Scientific, Inc, San Jose, California), no tachycardia could be induced by high-current rapid pacing. The low-voltage area (<0.5 mV in gray color) at the boundaries of the highest DF site are shown in the voltage map during sinus rhythm ().

Impact of Segmental Left Ventricle Lead Position on Cardiac Resynchronization Therapy Outcomes - Accepted Manuscript

2010-02-01

Abstract: Background:: The optimal pacing site for cardiac resynchronization therapy (CRT) is along the left ventricle (LV) lateral or posterolateral wall. However, little is known about the impact of segmental pacing site on outcomes.Objective:: We assessed the impact of segmental LV lead position on CRT outcomes.Methods:: Patients (n=115) undergoing CRT were followed prospectively. Segmental LV lead position along the longitudinal axis (apical, mid-ventricle or basal) was determined retrospectively by examining coronary sinus (CS) venograms and chest X-rays. Primary outcome was a combined endpoint of heart failure hospitalization, cardiac transplantation or all-cause mortality. Secondary outcomes included change in New York Heart Association (NYHA) functional class and degree of LV reverse remodeling.Results:: Patients were divided into two groups based on LV lead position: apical (n=25) and basal/mid-ventricle (n=90). The apical group was older (72.9 ± 8.9 vs. 66.5 ± 13.3 yrs, p = 0.010) and more likely to have ischemic cardiomyopathy (77% vs. 52%, p <0.001). During a mean follow-up of 15.1 ± 9.0 months, event free survival was significantly lower in the apical group: 52% vs. 79%, HR 2.7 (95% confidence interval [CI] 1.5-5.5, p=0.006). The adverse impact of apical lead placement remained significant after adjusting for clinical covariates: HR 2.3 (95% CI 1.1-4.8, p = 0.03). The apical group also experienced less improvement in NYHA functional class and less LV reverse remodeling.Conclusions:: Apical LV lead placement is associated with worse CRT outcomes. Preferential positioning of LV leads in the basal/mid-ventricle segments may improve outcomes.