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

BACKGROUND: Ultrasound evaluation of the abdominal aorta and its branches is usually performed transabdominally. Not infrequently, the image quality is suboptimal. Recently, an intracardiac echocardiography probe has become commercially available. These probes are usually inserted intravenously and advanced to the right heart for diagnostic and monitoring purposes during procedures such as atrial septal defect closure and pulmonary vein isolation. Because of the close anatomic relation between the abdominal aorta and the inferior vena cava, we hypothesized that these probes would be useful in the evaluation of the abdominal aorta and the renal arteries. METHODS: Sixteen patients with normal renal function and no history of hypertension who were undergoing a pulmonary vein isolation procedure or atrial septal defect closure were studied. In each patient, the intracardiac echocardiography probe was inserted in the femoral vein and advanced to the right atrium for the evaluation of the left atrium and the pulmonary veins during the procedure. At the end of the therapeutic procedure, the probe was withdrawn into the inferior vena cava for the evaluation of the aorta and renal arteries. RESULTS: High-resolution images of the abdominal aorta from the diaphragm to its bifurcation were easily obtained in all patients. These images allowed for the evaluation of arterial size, shape, and blood flow. Both renal arteries were easily visualized in each patient. With the probe in the inferior vena cava, both renal arteries were parallel to the imaging plane and, therefore, accurate measurement of renal blood flow velocity and individual renal blood flow were measured

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