Faculty Bibliography

Introduction: Brugada syndrome (BrS) is a heritable arrhythmogenic disease characterized by an augmented risk of sudden cardiac arrest (SCA). Studies on the pediatric population are few and on a limited number of patients. We describe the natural history of 90 children with BrS and on 48 genotyped patients with BrS, representing the largest series of child carriers of SCN5A mutations reported to date. Methods: 90 children (63 males) clinically and/or genetically affected by BrS, mean 10+/-6y, from 64 different families were studied using retrospective case review. Results: Type I or II ECG was observed in 40 patients (pts); 21 pts had ECG type I and 19 pts had ECG type II; 25 during protocol drug infusion and 5 with fever; 46 pts were studied because carriers of BrS mutations, despite normal ECG. Among the 21 patients with a spontaneous type I ECG, 4 were symptomatic (19%) and among the 19 patients with a spontaneous type II ECG, 5 were symptomatic (26%). 2/25, patients with a drug-induced phenotype were symptomatic (8%). Male predominance was observed in the symptomatic group (boys, 77%; girls, 30%). Family history of SCA was present in 35/90 pts. EP study, performed in 16 pts, was positive in only 1. ICD was implanted in 6 pts. During a mean follow-up of 50+/-34 months, 1 child experienced syncope; all other pts remained asymptomatic. Genetic screening for SCN5A was performed in 32 probands (pbs): 16 were carriers of a genetic defect. 57 pts were studied because of family history of BrS; 52 were carriers of the mutation found in their pbs, 5 belong to families with unknown genotype, but were clinically affected. Conclusions: In the pediatric population, ECG pattern and clinical manifestation of BrS are present in a small percentage of pts, suggesting a more subtle phenotype. Symptoms or ECG pattern can be precipitated by fever. Also, the role of EP study is not conclusive in pediatric BrS. In contrast to adults, some 50% of pediatric pbs are genetically affected, suggesting that a strict clinical selection of pts for SCN5A screening may lead to higher genotyping success

Introduction: Left ventricular diverticulum is a rare abnormality for which the etiology, management, and natural history are poorly understood. LV diverticuli are reported to be associated with ventricular tachycardia and sudden cardiac death, though the mechanisms of these ventricular arrhythmias have not been well characterized. Conversely, focal PVC triggers of idiopathic VF emanating from the distal Purkinje system have been well described. Here we report the first case of Purkinje fiber-mediated VF mapping to a LV diverticulum that was successfully treated with catheter ablation. Methods: N/A Results: An otherwise healthy 38 year old woman presented with sudden cardiac arrest. Electrocardiography demonstrated repeated episodes of polymorphic VT/VF. The initiating beats of VF were of a left-bundle branch pattern and were identical in ECG morphology to isolated PVCs that were observed in the aftermath of resuscitation. Cardiac MRI demonstrated a normal LVEF and, notably, a focal diverticulum at the inferoseptal wall. At electrophysiology study, a mapping/ablation catheter was positioned in the LV diverticulum via retrograde approach, where distinct purkinje potentials were noted to precede the onset of QRS complexes during sinus rhythm. Pace mapping from within the diverticulum demonstrated a 11/12 lead match for the index PVCs. Delivery of RF energy to this region terminated both the PVCs and future VF events. Conclusions: This is the first description of purkinje-fiber mediated VF mapping to a LV diverticulum and successfully treated with RF ablation. (Figure presented)

Introduction: Although the majority of rapid monomorphic VTs (faster than 320ms) can be ATP terminated, only Medtronic (MDT) has validated the clinical safety of its detection algorithm to distinguish rapid VT from VF. We set out to determine the performance characteristics of the Boston Scientific (BSC), MDT, and St. Jude Medical (SJM) ICD detection algorithms for VF at the time of ICD implantation and testing. Methods: Data on the detection of induced-VF at device implantation was collected on 62 consecutive patients in a non-randomized prospective cohort. Multi-zone programming for the BSC, MDT and SJM devices was based on data from the PAINFREE-II Trial. R-wave sensing at all implantations was performed with a Medtronic analyzer. Results: 62 patients were included and 124 tests for VFdetection were performed (Table). There were no differences in R-wave sensing or programmed sensitivity among groups. Compared to MDT and SJM, the BSC group had a significantly greater percentage of tests where charging occurred >5s from VF-induction. Mean time to charge initiation was 8s in 19.4% of tests in the BSC group. Marker channel/EGM analysis revealed that prolonged charge times resulted from inappropriate ATP and/or delayed VT/VF discrimination. Conclusions: The BSC VT/VF discrimination algorithm commonly results in delayed VF-detection when programmed with a VT zone from 240 to 320ms. This frequently translates into a prolonged time to device charge initiation. Further studies are needed to determine whether this prolonged detection time leads to clinically significant events. (Table presented)

Introduction: The Medtronic Fidelis lead family is associated with an unacceptable incidence of premature lead failure. Multiple studies have attempted to identify risk factors for lead failure and include younger age, better ejection fraction, and non-cephalic access. We hypothesized that other factors leading to potential increased forces on the lead including right-sided implantation or subpectoral positioning may be associated with premature lead failure. Methods: We reviewed the implant data from our group and identified 220 patients who received a Medtronic 6949 (dual coil) or 6931 (single coil) Fidelis lead. Implant data including age, sex, venous access site, implant side, implant location, lead length, and number of venous leads was reviewed. Hospital, Pacemaker Clinic, and Medtronic registration database were reviewed for evidence of lead failure, replacement, or abandonment. Data was evaluated in a univariate and multivariate analysis. Results: Of the 220 Fidelis leads implanted, 9 (4%) were noted to develop malfunction. This presented as inappropriate shocks from sensed noise, or elevated impedance measurements. Of the above noted implant features, only right-sided (vs. left-sided) implant, and subpectoral implant (vs. prepectoral) were found in uni- and multivariate analysis to be predictive of lead failure. Of 13 right-sided lead implants, 4 (30.7%) fractured (p<0.001). Of 14 subpectoral implants, 3 (21%) had lead failure (p<0.001). Conclusions: We have identified both right sided implantation and subpectoral generator positioning as factors associated with premature lead malfunction in the Fidelis lead family. Clinical decisions regarding patient management should incorporate these findings in regard to lead replacement in high risk patients

BACKGROUND: Atrial fibrillation catheter ablation is frequently guided by identification of fractionated electrograms, which are thought to be critical for maintenance of the arrhythmia. Objective automated means for identifying fractionation independent of physician interpretation have not been standardized or validated. OBJECTIVE: The purpose of this study was to standardize and validate an automated algorithm to rapidly identify fractionated electrograms for high-density atrial fibrillation fractionation mapping. METHODS: Left and right atrial fractionation maps were generated by EnSite NavX 6.0 software, using standardized ablation catheters in eight patients with atrial fibrillation. Two blinded electrophysiologists interpreted all electrograms as either fractionated or not fractionated. A stepwise approach was used to optimize automated settings to accurately identify fractionation. High-density fractionation maps were generated with a 20-pole mapping catheter in eight other patients. Two blinded electrophysiologists interpreted all electrograms as near field or far field. The algorithm was refined to optimize settings to exclude far-field signals and retain near-field signals. The sampling segment length was adjusted to optimize recording time to ensure reproducibility. RESULTS: Using 1,514 points, the automated software achieved sensitivity of 0.75 and specificity of 0.80 for identification of fractionated electrograms. Using 725 points collected via multipole catheters with optimal automated settings, 94% of near-field fractionated electrograms were accurately identified. A 6-second sampling length was needed for reproducible fractionation measurements. CONCLUSION: Standardized settings of EnSite NavX 6.0 software with 6-second data collection per point can rapidly and accurately generate high-density fractionation maps independent of physician electrogram interpretation. This may allow for an automated, standardized approach to atrial fibrillation fractionated ablation

This study assessed the effect of transtricuspid placement of permanent pacemaker (PPM) and implantable cardioverter defibrillator (ICD) leads on tricuspid regurgitation (TR) in 248 patients with echocardiograms before and after placement. Some 21.2% of patients with baseline mild TR or less developed abnormal TR (3.4% mild-moderate, 12.8% moderate, 1.1% moderate-severe, 3.9% severe) after implant. TR worsened by 1 grade or more after implant in 24.2% (20.7% of PPMs vs. 32.4% of ICDs; P < .05). TR worsening was more common with ICDs than PPMs in patients with baseline mild TR or less. After lead implantation, abnormal TR developed in 21.2% and severe TR developed in 3.9% of patients with initially normal TR. TR worsened by at least 1 grade in 24.2%. Patients with ICDs had a higher rate of TR worsening compared with patients with PPMs (32.4% vs. 20.1%; P < .05)