Faculty Bibliography

INTRODUCTION: The objective of this study was to determine the effects of isoproterenol infusion on level of consciousness during ablation using total intravenous anesthesia. METHODS AND RESULTS: Seven patients undergoing total intravenous anesthesia for atrial fibrillation ablation were monitored for level of consciousness using bispectral EEG levels (BIS). Isoproterenol infusion was performed after the ablation during anesthesia. BIS levels prior to, during, and post-isoproterenol infusion were recorded and correlated to isoproterenol infusion doses. In all patients, BIS levels significantly increased during isoproterenol infusion (median BIS prior to infusion, 46; during infusion, 64 (p < 0.02)). With a subsequent increase in anesthetic medication, BIS levels could again be reduced. CONCLUSION: Isoproterenol infusion alters consciousness level during total intravenous anesthesia for atrial fibrillation ablation. BIS monitoring is a novel way to modulate anesthesia during ablation to potentially optimize patient comfort and ablation success.

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).

Introduction: Spinal cord stimulation (SCS) has been shown to modulate atrial electrophysiology and confer protection against ischemia and ventricular arrhythmias in animal models. We hypothesized that SCS would reduce the susceptibility to tachypacing (TP) induced atrial fibrillation (AF). Methods: In 21 canines, an upperthoracicSCS system (EonC Model 3688, Octrode Model 3186, St. Jude Medical, Piano TX) and custom cardiac pacing system (PM, Model 5386 or 2215-36, St. Jude Medical, Sylmar CA) were implanted. Atrial effective refractory periods (ERPs) in the high right atrium (RA) and distal coronary sinus (LA) were measured at baseline and after 15 min of SCS, after which AV nodal ablation was performed. Following recovery in a subset of canines, PM was turned on to create TP induced AF by alternately delivering TP and searching for AF. TP was interrupted by detection of AF and resumed after return to sinus rhythm. Upon initiation of TP, canines were randomized to no SCS therapy (CTL, n=6) or intermittent SCS therapy (SCS-ON, n=4) and followed for 15 weeks. AF burden, defined as the percent of time in AF relative to the total sense time, and AF inducibility, defined as the percent of TP periods resulting in AF induction, were monitored weekly. Data are presented as mean +/- standard error. Results: ERPs were significantly longer after SCS compared to baseline, byan average of21 +/-14ms (p=0.001) in LA and 29+/-12ms (p=0.002) in RA. The AF burden was significantly decreased by 34 percentage points at week 15in SCS-ON compared to CTL (56 +/- 21% vs 90 +/- 12%, p<0.05). AF inducibility was significantly reduced by 60 percentage points at week 15 in SCS-ON compared to CTL (32 +/- 10% vs 91 +/- 6%, p<0.05). Conclusions: SCS prolonged atrial ERPs and reduced AF burden and inducibility in a canine atrial TP induced AF model. These data suggest that SCS therapy may represent a treatment option for AF

Atrial fibrillation is a common, clinically significant arrhythmic disorder that results in increased risk of morbidity and mortality in affected patients. Atrial fibrillation is more prevalent among men compared with women and the risk for developing atrial fibrillation increases with advancing age. Ischaemic stroke is the most common clinical manifestation of embolic events from atrial fibrillation. While anticoagulation treatment is the preferred treatment, unfortunately, many patients have contraindications for anticoagulation treatment making this option unavailable to them. Previous data have shown that most thrombi that form in association with non-valvular atrial fibrillation occur in the left atrial appendage (LAA). It has been suggested that isolating the LAA from the body of the left atrium might reduce the risk of embolic events and that LAA obliteration may be a treatment option for patients with atrial fibrillation who are not candidates for anticoagulation treatment. Several procedures have been developed for isolation of the LAA, including surgical procedures as well as catheter-based ones. In this paper, we will review the currently available techniques, emphasizing the catheter-based ones. We will examine the increasing role of real-time three-dimensional transoesophageal echocardiography for appropriate screening and patient selection for these procedures, intra-procedural guidance, and follow-up care.

A potentially life-threatening arrhythmia appeared on the preinduction electrocardiogram of an asymptomatic young woman prior to spine surgery. The patient was evaluated by electrophysiology and had a rare accessory pathway, a Mahaim Fiber

BACKGROUND: Transmural lesions are essential for efficacious ablation. There are, however, no accurate means to estimate lesion depth. OBJECTIVE: Explore use of the electrical coupling index (ECI) from the EnSite Contact System as a potential variable for lesion depth estimation. METHODS: Radiofrequency (RF) ablation lesions were created in atria and the thighs of swine using an irrigated RF catheter. Power was 30 W for 20 or 30 seconds intracardiac and 30-50 W for 10-60 seconds for the thigh. Intracardiac, the percentage change in ECI during ablation was compared with transmurality and collateral damage occurrence. For the thigh model, an algorithm estimating lesion depth was derived. Factors included: power, duration, and change in the ECI subcomponents (DeltaECI+) during ablation. The DeltaECI+ algorithm was compared to one using power and duration (PD) alone. RESULTS: Intracardiac, lesions with >/=12% reduction in ECI were more likely to be transmural (92.3% vs. 59.4%, P < 0.001). Twenty-second lesions were less likely to cause collateral damage compared to 30 seconds (33% vs. 70%, P = 0.003), while transmurality was similar. With the thigh model, DeltaECI+ had a better correlation than the PD algorithm (P < 0.01). Accuracy of the DeltaECI+ algorithm was unimproved with inclusion of tip orientation, while PD improved (R(2) = 0.64). DISCUSSION: Change in ECI provides evidence of transmural versus nontransmural swine intracardiac atrial lesions. A lesion depth estimation algorithm using ECI subcomponents is unaffected by tip orientation and is more accurate than using PD alone. CONCLUSION: Use of ECI as a factor in a lesion depth algorithm may provide clinically valuable information regarding the efficacy of intracardiac RF ablation lesions

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: Spinal cord stimulation (SCS) has been shown to modulate atrial electrophysiology and confer protection against ischemia and ventricular arrhythmias. We hypothesized that SCS may reduce susceptibility to tachypacing (TP) induced atrial fibrillation (AF). Methods: Spinal cord leads (Octrode, St. Jude Medical) were implanted in the upper thoracic spine (T1-T5) of canines and connected to pulse generators (EonC, St. Jude Medical). The AV node was ablated and atrial effective refractory period (AERP) was measured at baseline and with SCS (n=10). In separate animals the AV node was ablated and endocardial RA and RV pacing leads were connected to dual chamber pacemakers for ambulatory AF induction. Custom firmware provided continuous 30s periods of atrial TP followed by 6s sense windows. TP was interrupted by detection of AF (atrial rate >250 bpm) and resumed upon return to sinus rhythm. AF Index was defined as the fraction of time the animal did not receive TP relative to the total allowable TP time. The effect of SCS delivered intermittently for 6 hr/day (SCS ON; n=3) on AF index was followed for 8 weeks and compared to control (SCS OFF; n=3). Results: Right (p=0.002) and left (p=0.009) AERP were significantly longer during SCS (168+/-15.1, 168+/-14.8 ms) compared to baseline (130+/-8.7, 152+/-10.3 ms). AF Index was significantly decreased in the SCS ON compared to SCS OFF (p<0.0001). AF Index was >70% in the SCS OFF group and <5% in the SCS ON animals starting at week 3 (Figure). Conclusions: These data demonstrate that SCS prolongs AERP and prevents TP-induced AE (Graph presented)

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