Faculty Bibliography

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

A 21-year-old woman presented with a pacemaker-associated superior vena cava (SVC) syndrome refractory to medical therapy. In the past, treatment of this condition has involved surgical exploration which is invasive. With the evolution of percutaneous techniques, treatment has included venoplasty and stenting over the pacemaker lead. There is limited experience with a more advanced percutaneous technique in which the lead is extracted by an excimer laser sheath. The extraction is immediately followed by venoplasty and stenting at the site of stenosis with subsequent implantation of a new permanent pacemaker at the previously occluded access site. The patient underwent this procedure which proved to be safe, minimally invasive, and an efficient method of treating SVC syndrome secondary to a single chamber atrial pacemaker

The utility of programmed ventricular stimulation to predict future arrhythmic events in patients with cardiac sarcoidosis is unknown. Similarly, the long-term benefit of implantable cardioverter-defibrillators (ICDs) in cardiac sarcoidosis has not been established. Thirty-two consecutive patients with cardiac sarcoidosis underwent programmed ventricular stimulation. Patients with spontaneous or inducible sustained ventricular arrhythmias (n = 12) underwent ICD insertion. All study patients were followed for the combined arrhythmic event end point of appropriate ICD therapies or sudden death. Mean length of follow-up to sustained ventricular arrhythmia or sudden death was 32 +/- 30 months. Five of 6 patients (83%) with spontaneous sustained ventricular arrhythmias and 4 of 6 patients (67%) without spontaneous but with inducible sustained ventricular arrhythmias received appropriate ICD therapy. Two of 20 patients (10%) with neither spontaneous nor inducible sustained ventricular arrhythmias experienced sustained ventricular arrhythmias or sudden death. Programmed ventricular stimulation predicted subsequent arrhythmic events in the entire population (relative hazard 4.47, 95% confidence interval [CI] 1.30 to 15.39) and in patients who presented without spontaneous sustained ventricular arrhythmias (relative hazard 6.97, 95% CI 1.27 to 38.27). No patient with an ICD died of a primary arrhythmic event. In patients with spontaneous or inducible sustained ventricular arrhythmias, mean survival from first appropriate ICD therapy to death or cardiac transplant was 60 +/- 46 months, with only 2 patients dying or reaching transplant at study end. In conclusion, programmed ventricular stimulation identifies patients with cardiac sarcoidosis at high risk for future arrhythmic events. ICDs effectively terminate life-threatening arrhythmias in high-risk patients, with significant survival after first appropriate therapy