Faculty Bibliography

Background: The Medtronic Sprint Fidelis (Medtronic Inc., Minneapolis, MN, USA) lead family is associated with an unacceptable incidence of premature lead failure. There are limited data on risk factors for lead fracture. We hypothesized that factors leading to potential increased forces on the lead related to device implantation or technique may be associated with premature lead failure. Methods: We reviewed the implant data from our group and identified 176 patients who received active fixation Medtronic Fidelis (Model 6931, single coil and Model 6949, dual coil) leads. Implant data, including age, sex, venous access site, implant side, implant location, and number of venous leads were reviewed. Hospital, pacemaker clinic, and Medtronic registration databases were reviewed for evidence of lead failure, replacement, or abandonment. Data was evaluated in univariate and multivariate regression analyses. Results: Of the 176 leads implanted, 10 (5.7%) 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 (hazard ratio [HR] 18.8, 95% confidence intervals [CI] 3.8, 93.3), and subpectoral implant (vs prepectoral; HR 14.31, 95% CI 3.2, 64.0) were predictive of lead failure in maximally adjusted models. Conclusions: We have identified both right-sided implantation and subpectoral generator positioning as factors associated with premature lead malfunction in Fidelis active fixation leads. Clinical decisions regarding patient management should incorporate these findings in regard to lead replacement in high-risk patients. (PACE 2012; 35:659-664).

BACKGROUND: There are little data on the appropriate endpoint for slow pathway ablation that balances acceptable procedural times, recurrence rates, and complication rates. This study compared recurrence rates of three commonly utilized endpoints of slow pathway ablation for atrioventricular nodal reentrant tachycardia (AVNRT). METHODS: We performed a meta-analysis of AVNRT slow pathway ablation cohorts by searching electronic databases, the Internet, and conference proceedings. Inclusion criteria were age >18 years, >20 human subjects per study, primary AVNRT ablation, English language publication, and >1 month of follow-up. Data were analyzed with a fixed-effects model using Comprehensive Meta-Analysis software version 2.2.046 (Biostat, Englewood, NJ, USA). RESULTS: We included 10 studies encompassing 1,204 patients with a mean age of 41-53 years. Endpoints were complete slow pathway ablation, residual jump only, and single remaining echo beat. Pooled estimates revealed 28 of 641 patients (4.4%) with complete slow pathway ablation, 13 of 192 patients (6.8%) with a residual jump only, and 24 of 371 patients (6.5%) with one echo had recurrences. With uniform isoproterenol use after ablation, there was no significant difference in recurrence rates among the endpoints. However, when isoproterenol was utilized after ablation only if needed to induce AVNRT before ablation, a significantly higher recurrence rate occurred in patients with a residual jump (P = 0.002), a single echo (P = 0.003), or the combined group of a residual jump and/or one echo (P = 0.001). CONCLUSIONS: Isoproterenol should be used routinely after slow pathway modification, when a residual jump and/or single echo remain

Introduction : With the increase in anesthesia utilization in the electrophysiology laboratory, there is greater potential for arrhythmia suppression during electrophysiology study. Intravenous isoproterenol is frequently used to counteract the significant antiadrenergic impact of anesthesia, as well as induce arrhythmias and identify reconnection of pulmonary vein conduction. The effects of isoproterenol on cerebral and respiratory function during the sedated state have not been well studied. The Bispectral (BIS) Vista TM Monitor is a non-invasive device that measures electrical activity of the brain and computes a BIS value, which corresponds to a level of consciousness. The purpose of this study was to determine changes in BIS values during isoproterenol administration. Methods : Twenty consecutive patients underwent electrophysiology study under total intravenous anesthesia using propofol and remifentanil infusions. Isoproterenol was infused at a rate of 5mcg/kg/min and escalated to up to 20mcg/kg/min over 20 minutes. BIS levels were recorded before and throughout isoproterenol administration. Results : Patients demonstrated significant elevation in BIS value during isoproterenol infusion. The mean difference between pre- and post- BIS values was 21.3 [5.4, 37.2] (p = 0.00013). The isoproterenol doses which triggered a BIS spike ranged from 10.8 mcg to 90.8 mcg. The median effective isoproternol dose was 25.2 mcg. The median onset time for an isoproternol stimulated BIS spike was 6.9 minutes with rates from 2 to 20 mcg/minute. Discussion : Isoproterenol significantly increases BIS values during sedated electrophysiology study. Monitoring BIS values may be helpful in assessing the isoproterenol dosage required to overcome the suppressive effects of anesthesia on arrhythmia induction, as well as the potential need for additional anesthetics to prevent patient arousal. Conversely, decreasing BIS values are known to correlate with hypotensive episodes signaling cerebral hypoperfusion. This may be relevant in cases of hemodynamically unstable tachycardias. BIS appears to be an important tool for the optimization of anesthesia when isoproterenol is administered during electrophysiology study

Atrial fibrillation (AF), a very common cardiac arrhythmia, is a well-recognized predisposing factor for embolic stroke. While warfarin remains the cornerstone of anticoagulant treatment in patients with AF, it is often underutilized because of increased bleeding complications and frequent monitoring requirements. It has been documented that the left atrial appendage (LAA) is the main source of left atrial thrombus that causes strokes in AF patients. Thus, closure of the LAA may be an effective strategy in stroke reduction. Several devices have been used in closure of the LAA. The WATCHMAN device appears to be a safe and efficacious device for closure of the LAA as recently demonstrated in the PROTECT AF trial

A 64-year-old man with complete heart block, status post-Medtronic dual chamber pacemaker insertion, failed ablation for atrial tachycardia at an outside institution. Despite persistent palpitations and known unsuccessful ablation, pacemaker interrogation revealed no evidence of atrial arrhythmias. At electrophysiology study, burst pacing from the high right atrium and distal coronary sinus at 370 ms revealed bidirectional 2:1 interatrial conduction block. Left atrial burst pacing at 260 ms induced an atrial tachycardia (cycle length 340 ms) with 2:1 left to right atrial block and right atrial activation at 680 ms. The tachycardia was localized to the lateral left atrial roof. A series of ablation lesions from left to right superior pulmonary vein terminated the tachycardia. Left to right interatrial conduction block is a mechanism for underdetection of atrial arrhythmias with implantable devices not previously described. As the extent of atrial ablation increases, the incidence of this mechanism of underdetection may increase. Though devices are often considered ideal for atrial arrhythmia detection and are used in multiple trials, detection failures can occur despite appropriate device function. This case underscores the need for electrocardiographic monitoring in addition to device-based electrogram monitoring

Background: Electrocardiographic (ECG) criteria for left ventricular (LV) hypertrophy have been shown to have modest predictive values when compared to LV hypertrophy measured by cardiac magnetic resonance (CMR). Prior studies have excluded patients with cardiomyopathies and have not evaluated regional wall thickness in addition to overall LV mass and wall thickness. Thus it remains unknown how well ECG criteria will predict both regional wall thickness and overall LV mass/wall thickness compared to CMR in this population. Objective: To determine if common criteria for LV hypertrophy on ECG are predictive of regional wall thickness and overall LV mass as determined by CMR in patients with cardiomyopathy. Methods: A total of 41 consecutive patients (34 male) greater than 40 years old who underwent CMR for evaluation of cardiomyopathy (both ischemic and non-ischemic) were evaluated. Recent ECG's (mean of 8 days from CMR) were blindly evaluated and patients with a QRS > 120 were excluded from analysis. LV mass and regional wall thickness (anterior, septal, inferior, lateral) were measured at end-diastole on CMR. ECG voltage was examined by two commonly used determinants of LV hypertrophy: 1) Sokolow (SV1+RV5 or V6) and 2) Cornell (SV3 +RaVL) criteria. Pearson r correlations were used to examine the relationship between the CMR and ECG parameters. Results: Mean LV mass was 154 +/- 55 grams, and LV mass index was 76 +/- 31 grams/meters². Sokolow ECG voltage showed good to high correlations with overall LV mass and regional wall thickness, with no significant differences between LV regions (Table 1). Cornell ECG voltage correlated less strongly with CMR parameters, and also showed no significant regional differences. Conclusion: Sokolow ECG voltage criteria for LV hypertrophy demonstrates good to high correlations with LV mass and (Table presented) regional LV wall thickness in patients with cardiomyopathy. Cornell criteria performed worse in this population. No significant differences existed between LV regional wall thickness for either criteria

Limited data suggest that athletes may have a higher risk of developing atrial fibrillation (AF); however, there has been no large prospective assessment of the relation between vigorous exercise and AF. Logistic regression analyses stratified by time were used to assess the association between frequency of vigorous exercise and risk of developing AF in 16,921 apparently healthy men in the Physicians' Health Study. During 12 years of follow-up, 1,661 men reported developing AF. With increasing frequency of vigorous exercise (0, 1, 1 to 2, 3 to 4, 5 to 7 days/week), multivariate relative risks for the full cohort were 1.0 (referent), 0.90, 1.09, 1.04, and 1.20 (p = 0.04). This risk was not significantly increased when exercise habits were updated or in models excluding variables that may be in the biological pathway through which exercise influences AF risk. In subgroup analyses, this increased risk was observed only in men <50 years of age (1.0, 0.94, 1.20, 1.05, 1.74, p <0.01) and joggers (1.0, 0.91, 1.03, 1.30, 1.53, p <0.01), where risks remained increased in all analyses. In conclusion, frequency of vigorous exercise was associated with an increased risk of developing AF in young men and joggers. This risk decreased as the population aged and was offset by known beneficial effects of vigorous exercise on other AF risk factors

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)