Epicardial Pulsed Field Ablation of Ganglionated Plexi: Computational and Pre-Clinical Evaluation of a Bipolar Sub-Xiphoid Catheter for the Treatment of Atrial Fibrillation

Epicardial pulsed field ablation (PFA) of ganglionated plexi (GPs) is being explored as a potential treatment for atrial fibrillation. Initial work using open-chest access with a monopolar ablation device has been completed. This study describes the early development work for a device that can be used with subxiphoid access and deliver bipolar ablation pulses. Electric field computational models have been used for the initial guidance on pulse parameters. An in vivo assessment of these ablation parameters has been performed in an open-chest canine study, while subxiphoid access and navigation of the device has been demonstrated in a porcine model. Results from this acute study have demonstrated the promising potential of this approach.

Targeted ablation of epicardial ganglionated plexi during cardiac surgery with pulsed field electroporation (NEURAL AF)

BACKGROUND

Modulation of the cardiac autonomic nervous system (ANS) is a promising adjuvant therapy in the treatment of atrial fibrillation (AF). In pre-clinical models, pulsed field (PF) energy has the advantage of selectively ablating the epicardial ganglionated plexi (GP) that govern the ANS. This study aims to demonstrate the feasibility and safety of epicardial ablation of the GPs with PF during cardiac surgery with a primary efficacy outcome of prolongation of the atrial effective refractory period (AERP).

METHODS

In a single-arm, prospective analysis, patients with or without a history of AF underwent epicardial GP ablation with PF during coronary artery bypass grafting (CABG). AERP was determined immediately pre- and post- GP ablation to assess cardiac ANS function. Holter monitors were performed to determine rhythm status and heart rate variability (HRV) at baseline and at 1-month post-procedure.

RESULTS

Of 24 patients, 23 (96%) received the full ablation protocol. No device-related adverse effects were noted. GP ablation resulted in a 20.7 ± 19.9% extension in AERP (P < 0.001). Post-operative AF was observed in 7 (29%) patients. Holter monitoring demonstrated an increase in mean heart rate (74.0 ± 8.7 vs. 80.6 ± 12.3, P = 0.01). There were no significant changes in HRV. There were no study-related complications.

CONCLUSIONS

This study demonstrates the safety and feasibility of epicardial ablation of the GP using PF to modulate the ANS during cardiac surgery. Large, randomized analyses are necessary to determine whether epicardial PF ablation can offer a meaningful impact on the cardiac ANS and reduce AF.

TRIAL REGISTRATION

Clinical trial registration: NCT04775264.

Nonthrombogenic Roles of the Left Atrial Appendage: JACC Review Topic of the Week

The atrial appendage (LAA) is a well-established source of cardioembolism in patients with atrial fibrillation. Therefore, research involving the LAA has largely focused on its thrombogenic attribute and the utility of its exclusion in stroke prevention. However, recent studies have highlighted several novel functions of the LAA that may have important therapeutic implications. In this paper, we provide a concise overview of the LAA anatomy and summarize the emerging data on its nonthrombogenic roles.

Transformation of computerized electrocardiogram data into novel means to differentiate wide complex tachycardias

Background

Accurate automated wide QRS complex tachycardia (WCT) discrimination between ventricular tachycardia (VT) and supraventricular wide complex tachycardia (SWCT) can be accomplished using novel calculations derived from computerized electrocardiogram (ECG) data from paired WCT and baseline ECGs.

Purpose

Our aim was to develop and trial novel WCT discrimination approaches for WCT patients with and without a corresponding baseline ECG. Central to this analysis was the creation and use of a novel parameter (i.e., percent monophasic time-voltage area [PMonoTVA] [%]) that may be derived from computerized ECG measurements present on the WCT ECG alone.

Methods

In a two-part study, we derived and tested WCT differentiation models comprised of novel and previously established parameters formulated from computerized data of paired WCT and baseline ECGs. In Part 1, novel and established parameters generated from WCT and baseline ECG data were used to derive, validate, and compare five different binary classification models: (i) logistic regression [LR], (ii) artificial neural network [ANN], (iii) Random Forests [RF], (iv) support vector machine [SVM], and (v) ensemble learning (EL). In Part 2, two unique LR models were derived, validated, and compared using parameters generated from computerized data of the (i) WCT ECG alone (i.e., Solo Model) and (ii) paired WCT and baseline ECGs (i.e., Paired Model).

Results

In Part 1, among 103 patients with VT or SWCT diagnoses established from corroborating electrophysiology studies or intra-cardiac device recordings, favorable diagnostic performance was achieved by all modeling technique subtypes: LR (area under the receiver operating characteristic curve [AUC] 0.95), ANN (AUC 0.91), RF (AUC 0.97), SVM (AUC 0.98), and EL (AUC 0.97). In Part 2, among 235 patients with a VT or SWCT diagnosis established with (Gold Standard cohort) or without (Non-Gold Standard cohort) a corroborating electrophysiology procedure or intra-cardiac device recording, favorable diagnostic performance was achieved by the Solo Model (AUC 0.86) and Paired Model (AUC 0.95) (Table).

Conclusion

Accurate WCT discrimination may be accomplished using novel parameters derived from computerized data of the WCT ECG alone and paired WCT and baseline ECGs.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): National Institute of Health

The Mitral Annular Disjunction of Mitral Valve Prolapse: Presentation and Outcome

OBJECTIVES

The aim of this study was to assess in patients with mitral valve prolapse (MVP) mitral annular disjunction (MAD) prevalence, phenotypic characteristics, and long-term outcomes (clinical arrhythmic events and excess mortality).

BACKGROUND

Clinical knowledge regarding MAD of MVP remains limited and controversial, and its potential link with untoward outcomes is unsubstantiated.

METHODS

A cohort of 595 (278 women, mean age 61 ± 16 years) consecutive patients with isolated MVP, with comprehensive clinical, rhythmic, Doppler echocardiographic, and consistent MAD assessment, were examined. MAD prevalence, associated MVP phenotypes, and outcomes (survival, clinical arrhythmic events) starting at diagnostic echocardiography were analyzed. To balance important baseline differences, propensity scoring matching was conducted among patients with and those without MAD.

RESULTS

The presence of MAD was common (n = 186 [31%]) in patients with MVP, generally in younger patients, and was not random but was independently associated with severe myxomatous disease involving bileaflet MVP and marked leaflet redundancy (both P ≤ 0.0002). The presence of MAD was also independently associated with a larger left ventricle (P = 0.005). Age-matched cohort survival after MVP diagnosis was not worse with MAD (10-year survival 93% ± 2% for patients without MAD and 97% ± 1% for those with MAD; P = 0.40), even adjusted comprehensively for MVP characteristics (P = 0.80) and accounting for time-dependent mitral surgery (P = 0.60). During follow-up, 170 patients had clinical arrhythmic events (ventricular tachycardia, n = 159; arrhythmia ablation, n = 14; cardioverter-defibrillator implantation, n = 14; sudden cardiac death, n = 3). MAD was independently associated with higher risk for arrhythmic events (adjusted HR: 2.60; 95% CI: 1.87-3.62; P < 0.0001). The link between MAD and arrhythmic events persisted with time-dependent mitral surgery (adjusted HR: 2.54; 95% CI: 1.84-3.50; P < 0.0001), was strong under medical management (adjusted HR: 3.21; 95% CI: 2.03-5.06; P < 0.0001) but was weaker after mitral surgery (adjusted HR: 2.07; 95% CI: 1.24-3.43; P = 0.005).

CONCLUSIONS

This large cohort with MVP comprehensively characterized shows that MAD is frequent at MVP diagnosis and is strongly linked to advanced myxomatous degeneration. The presence of MAD was independently associated with long-term excess incidence of clinical arrhythmic events. However, within the first 10 years post-diagnosis, MAD was not linked to excess mortality, and although reassurance should be provided from the survival point of view, careful monitoring for arrhythmias is in order for MAD.

Activation pattern during his pacing: how close are we to normal physiology?

Background

His bundle pacing aims to mimic the activation pattern of normal conduction to maintain ventricular synchrony. However, selective His capture can be challenging, and the activation sequence during His pacing may not replicate normal conduction.

Purpose

Compare the right ventricular (RV) and left ventricular (LV) activation pattern in sinus rhythm and His bundle pacing.

Methods

Baseline LV and RV map was created in sinus rhythm using Rhythmia mapping system (Boston Scientific Corporation) in canine animal model. Medtronic 3830 lead was placed near the bundle of His under fluoroscopic, intracardiac echocardiogram, and electroanatomic guidance. Conduction system capture was confirmed by observing a QRS duration &lt;120ms and an isoelectric segment between pacing artifact and QRS on surface ECG. Repeat LV and RV activation map was obtained during His pacing. Average QRS, HV and pacing to V intervals were calculated with standard deviation.

Results

Mapping was performed successfully in four animals. At baseline, the average QRS duration was 44±2.6ms and HV interval was 32±4.2ms. Earliest site of myocardial activation was in the mid-septal LV region. The earliest RV myocardial activation was also at the septum closer to the apex, but later than the LV (Figure1A). With His pacing, the average QRS duration was 70±17.0ms and the average stim to V interval was 31±8.7ms. During His pacing, the earliest site of activation was in the RV septum, with an activation pattern from base to apex in both the RV and LV.

Conclusion

Unlike normal physiology, the activation pattern during conduction system pacing is from base to apex with earliest site in the RV.

Funding Acknowledgement

Type of funding source: Public hospital(s). Main funding source(s): Mayo Clinic

A cool modality to restore sinus rhythm

Background

Slowing electrical conduction by cooling the myocardium can be used for defibrillation. We previously demonstrated the efficacy of a small cold device placed in oblique sinus (OS) in terminating atrial fibrillation (AF). However, the parameters needed to achieve effective atrial defibrillation are unknown.

Purpose

Assess effect of the size of cooled myocardium on frequency of AF termination in acute canine animal models.

Methods

Sternotomy was performed under general anesthesia in 10 acute canine experiments. AF was induced using rapid atrial pacing and intra-myocardial epinephrine and acetylcholine injections. Once AF sustained for at least 30s, either a cool (7–9°C) or placebo (body temperature) device was placed in the OS. Four device sizes were tested; ½X½, ¾X¾, and 1X1 inch devices and two ¾X¾ inch devices placed side by side simultaneously. Time to AF termination was recorded. Chi-squared or Fisher's exact test were used to compare the frequency of arrhythmia termination with cooling versus placebo.

Results

A total of 166 applications were performed (89 cool vs 77 placebo) in 10 animal experiments. Overall, AF terminated in 82% of the cooling applications vs. 67.5% of placebo (P=0.03, Figure 1). For the ½X½ inch device 88% of cold applications restored sinus rhythm vs. 63.6% for placebo (P=0.05). The frequency of sinus restoration for cold ¾X¾, 1X1 and two ¾X¾ side by side devices was 86.7%, 83.3% and 70% respectively. Time to sinus restoration when achieved was within three minutes was also not significantly changed.

Conclusion

Placing a cool device in the oblique sinus can terminate AF and efficacy is not affected by the size of device.

Funding Acknowledgement

Type of funding source: Private grant(s) and/or Sponsorship. Main funding source(s): MediCool Technologies

Meta-Analysis Comparing WatchmanTM and Amplatzer Devices for Stroke Prevention in Atrial Fibrillation

Background: For patients with atrial fibrillation who are at high risk for bleeding or who cannot tolerate oral anticoagulation, left atrial appendage (LAA) closure represents an alternative therapy for reducing risk for thromboembolic events. Objectives: To compare the efficacy and safety of the Amplatzer and Watchman^TM LAA closure devices. Methods: A meta-analysis was performed of studies comparing the safety and efficacy outcomes of the two devices. The Newcastle-Ottawa Scale was used to appraise study quality. Results: Six studies encompassing 614 patients were included in the meta-analysis. Overall event rates were low for both devices. No significant differences between the devices were found in safety outcomes (i.e., pericardial effusion, cardiac tamponade, device embolization, air embolism, and vascular complications) or in the rates of all-cause mortality, cardiac death, stroke/transient ischemic attack, or device-related thrombosis. The total bleeding rate was significantly lower in the Watchman^TM group (Log OR = -0.90; 95% CI = -1.76 to -0.04; p = 0.04), yet no significant differences was found when the bleeding rate was categorized into major and minor bleeding. Total peridevice leakage rate and insignificant peridevice leakage rate were significantly higher in the Watchman^TM group (Log OR = 1.32; 95% CI = 0.76 to 1.87; p < 0.01 and Log OR = 1.11; 95% CI = 0.50 to 1.72; p < 0.01, respectively). However, significant peridevice leakages were similar in both the devices. Conclusions: The LAA closure devices had low complication rates and low event rates. Efficacy and safety were similar between the systems, except for a higher percentage of insignificant peridevice leakages in the Watchman^TM group. A randomized controlled trial comparing both devices is underway, which may provide more insight on the safety and efficacy outcomes comparison of the devices.

650The arrhythmic mitral valve prolapse: presentation and outcome

Background

The majority of patients with of Mitral-valve-prolapse (MVP) have a excellent prognosis. Until recently most cases of mortality were thought to be related to mitral regurgitation and left ventricular dysfunction. The concept of the arrhythmic MVP emerged to describe cases of sudden cardiac death (SCD) in the presence of isolated MVP yet it’s phonotype remains incompletely and inconsistently defined.

Purpose

To analyze the prevalence, severity and characteristics of ventricular-arrhythmia (VA), to determine it’s phenotypical context and independent impact on outcome in patients with MVP.

Methods

A cohort of 595 (65 ± 16 years, 278 female) consecutive patients with MVP and comprehensive clinical, arrhythmia (24hour-Holter) and Doppler-echocardiographic characterization, was identified and long-term outcome analyzed.

Results

VA was frequent, present in 43% of patients with at least ventricular ectopy≥5%, but was most often moderate (ventricular-tachycardia—VT 120-179bpm) in 27% and rarely severe (VT≥180/min) in 8.6%.  Presence of VA was associated with older age, male sex, bileaflet-prolapse, marked leaflet redundancy, mitral-annulus-disjunction (MAD), larger left-atrium and left ventricular end-systolic diameter, and T-wave-inversion/ST-depression (all P ≤ 0.001).  Severe VA was independently associated with presence of MAD, leaflet-redundancy and T-wave-inversion/ST-depression (all P &lt; 0.0001) but not with mitral regurgitation severity or ejection-fraction.  Outcome primary endpoint of overall survival after arrhythmia diagnosis (8-year 87 ± 2%) was strongly associated with arrhythmia-severity (8-year 90 ± 2% for no/trivial arrhythmia, 85 ± 3% for mild/moderate and 76 ± 7% for severe arrhythmia. P = 0.02, Figure). Excess-mortality was substantial for severe-arrhythmia (univariate-hazard-ratio 2.70[1.27-5.77], P = 0.01 vs. no/trivial arrhythmia), even adjusted comprehensively including for MVP-characteristics (adjusted-hazard-ratio 2.94[1.36-6.36], P = 0.006) ). 

Conclusions

This large cohort of isolated consecutive MVP characterized with 24-hour-Holter monitoring, clinical and Echocardiographic assessment, demonstrates that VA are frequent with MVP but rarely severe. The arrhythmic MVP was independently and strongly associated with specific ECG and morphologic patterns, particularly ST-T changes, MAD presence and marked leaflet redundancy, suggestive of a specific arrhythmic MVP phenotype, independently of MR-severity. Arrhythmia, particularly severe, is associated with long-term excess-mortality, independently of any other characteristics, including MR severity and LVEF. These findings lay the foundation for novel risk-stratification of MVP for the conduct of prospective controlled studies evaluating the management of MVP high-risk patients.

Figure – Impact on survival of ventricular arrhythmia

Overall survival of MVP stratified by ventricular arrhythmia (Panel A) or ventricular arrhythmia severity (Panel B) throughout follow-up.

Abstract Figure.

Feasibility of High-Resolution Electrical Mapping for Characterizing Conduction Blocks Created by Gastric Ablation

The interstitial cells of Cajal (ICC) initiate, coordinate and propagate bioelectrical slow wave activity that drives gastric motility. In the healthy human stomach, slow wave activity is highly organized. Gastric motility disorders are associated with dysrhythmias. While ablation is widely used to treat cardiac dysrhythmias, this approach has yet to be trialed in the stomach. In this study, radiofrequency (RF) ablation was applied in pig stomachs in vivo to create targeted electrical conduction blocks. Ablations were performed at temperature control mode (55-70°C), and resultant conduction blocks were identified and verified using high-resolution electrical mapping. Termination of slow wave propagation at ablation sites was confirmed by a decrease in extracellular slow wave amplitude from 1.7 ± 0.2 mV to an undetectable amplitude, as well as spatiotemporal pattern analysis of conduction blocks. The use of high-resolution electrical mapping can now be employed to investigate ablation as a potential therapy for gastric dysrhythmias in motility disorders.

Routine Continuous Electrocardiographic Monitoring Following Percutaneous Coronary Interventions

BACKGROUND

The clinical utility of routine electrocardiographic monitoring following percutaneous coronary interventions (PCI) is not well studied.

METHODS

We prospectively evaluated the incidence, cost, and the clinical implications of actionable arrhythmia alarms on telemetry monitoring following PCI. One thousand three hundred fifty-eight PCI procedures (989 [72.8%] for acute coronary syndrome and 369 [27.2%] for stable angina) on patients admitted to nonintensive care unit were identified and divided into 2 groups; group 1, patients with actionable alarms (AA) and group 2, patients with non-AA. AA included (1) ≥3 s electrical pause or asystole; (2) high-grade Mobitz type II atrioventricular block or complete heart block; (3) ventricular fibrillation; (4) ventricular tachycardia (>15 beats); (5) atrial fibrillation with rapid ventricular response; (6) supraventricular tachycardia (>15 beats). Primary outcomes were 30-day all-cause mortality. Cost-savings analysis was performed.

RESULTS

Incidence of AA was 2.2% (37/1672). Time from end of procedure to AA was 5.5 (0.5, 24.5) hours. Patients with AA were older, presented with acute congestive heart failure or non-ST-segment-elevation myocardial infarction, and had multivessel or left main disease. The 30-day all-cause mortality was significantly higher in patients with AA (6.5% versus 0.3% in non-AA [P<0.001]). Applying the standardized costing approach and tailored monitoring per the American Heart Association guidelines lead to potential cost savings of $622 480.95 for the entire population.

CONCLUSIONS

AA following PCI were infrequent but were associated with increase in 30-day mortality. Following American Heart Association guidelines for monitoring after PCI can lead to substantial cost saving.

P4126Safety of magnetic resonance imaging in patients with non-conditional cardiac implantable electronic devices: A systematic review and meta-analysis

Objective

We aimed to systematically review the literature to identify the adverse events and significance of changes in device function associated with performing MRI in patients with CIEDs

Methods

A comprehensive literature search of the databases was performed between 1980- 2017. Two independent reviewers selected studies and extracted data. A random-effects model was used for meta-analysis.

Results

A total of 7,422 patients underwent 8,865 MRI studies. No death occurred post MRI. Clinical adverse events were extremely rare (mostly less than 1%) and are summarized in Table 1. No significant changes in the pooled mean effect size estimate was noted for the changes in the lead parameters (pacing threshold, sensing and impedance)

Binary outcomes post magnetic resonance imaging in patients with non-conditional cardiac implantable electronic devices Outcome Sample size Number of patients Rate SE LL of CI UL of CI Death 7401 0 0 0 0 0 Atrial arrhythmia 7173 10 0.001 0.0004 0.0007 0.0024 Ventricular arrhythmia 7371 9 0.0012 0.0004 0.0006 0.0022 Oversensing 4981 17 0.0034 0.0008 0.0020 0.0053 Inhibition of pacing 7371 6 0.0008 0.0003 0.0003 0.0016 Lead Failure/Generator Failure 7475/7475 2/8 0.0002/0.0011 0.0001/0.0004 0.0001/0.0005 0.0009/0.002 Power on Reset 1388 105 0.0131 0.0014 0.0107 0.0161 Did not complete scan 6851 13 0.0019 0.0005 0.0011 0.0031 Chest pain 7080 11 0.0021 0.0004 0.0008 0.0027. Lead threshold rise (>0.5v/>50%-A/V) 5076/6246 12/16 0.0024/0.0026 0.0007/0.0006 0.0013/0.0015 0.0040/0.0041 Change in Battery voltage >0.04V 7132 42 0.0061 0.0009 0.0043 0.0079 Sensing decrease >50%-A/V 5087/5834 17/9 0.0033/0.0015 0.0008/0.0005 0.0020/0.0008 0.0052/0.0028 Impedance changes >50ohms/>50% 5810 22 0.0038 0.0008 0.0024 0.0057 Rise in cardiac enzymes 1703 26 0.0152 0.0030 0.0102 0.0219 A, atrial; V, ventricular; SE, standard Error; LL, lower limit; UL, upper limit; CI, Confidence intervals.

Conclusions

MRI in patients with non-conditional CIEDs can be performed with high degree of safety and low rate of clinical events when performed under standardized protocols

Acknowledgement/Funding

None

P5703The anterior interventricular crux: anatomic basis for ablation below the left sinus of valsalva (LSOV) of varied ECG morphology PVCs

Background

Outflow tract premature ventricular complexes (PVCs) may be ablated at sites where the local electrogram is early. We describe ablation of PVCs of varying morphology at a cruciate structure extending from the inflection of the great cardiac vein to the junction of the distal RVOT and from the left ventricular (LV) inflow myocardium through the aortic mitral continuity (AMC) to the right coronary sinus of Valsalva centered below LSOV, termed the LV crux.

Purpose

Evaluate a novel target for ablation of PVCs with varied QRS morphologies.

Methods

A series of 51 patients undergoing ablation for PVCs between 2013–2018 was identified. In all cases, ICE-guided ablation occurred at the center of the LV crux.

Results

All patients had high PVC burden >20% (28±8%); EF<50% in 40/51 (78%). QRS morphology of PVCs is summarized in Table 1. 50% had prior ablation attempted at early sites. Mapping and ICE-guided ablation at the LV crux (Figure 1 A-B) revealed early activation with near-field ventricular or fascicular signal in 31 (61%), while others had early sites at extensions of the crux. PVCs were eliminated in 50/51 (98%) with continued suppression at 3-months. EF normalized in all 51.

Table 1. ECG charactaeristics ECG characteristics Number of patients (%) Inferior morphology 51/51 (100%) Lead I morphology   Monophasic R 8/51 (16%)   Rs 9/51 (18%)   rS 34/51 (66%) Precordial transition   Positive across precordium 40 (78%)   V2 transition 7 (14%)   V3 transition 4 (8%) Maximum deflection index   <0.55 37 (73%)   >0.55 14 (27%)

Figure 1. Mapping and ablation

Conclusions

A cruciate interventricular multidimensional crux centered below the LSOV is a site for successful ablation of varied PVC morphologies and should be considered for detailed mapping and ablation, particularly when multiple morphologies are present or prior ablation at early sites is unsuccessful. Ventricular myocardial architecture along with conduction system remnants may be the basis for this phenomenon.

Putting down the phone: the obsolescence of transtelephonic monitoring for pacemaker follow-up

PURPOSE

The evolution of heart rhythm monitoring technology over the past few decades has seen a decline in the use and need of transtelephonic monitoring (TTM). We sought to establish a predicted date for the sun setting of TTM at our institution, as well as establish the current demographics of the patients still using this technology.

METHODS

We retrospectively reviewed all patients with permanent pacemakers receiving routine device follow-up at our institution (Mayo Clinic-Rochester) between 2015 and 2018. From this cohort, we reviewed and analyzed patients using TTM for device follow-up and utilized projected battery longevity to determine cessation date. Pacemaker implantation date, underlying arrhythmia, and most recent device interrogation reports were also collected.

RESULTS

As of March 2018, a total of 3543 patients with permanent pacemakers were being followed at our institution and 289 (8.2%) are using TTM for monitoring device function (147 male, mean age 79.9 ± 12.0 years). Of those currently using TTM, by January of 2020, only 122 (42.2%) are predicted to be using this technology for device follow-up, 40 (13.8%) by January 2022, with zero patients by November of 2024.

CONCLUSIONS

The use of TTM will continue to significantly diminish over the next few years. Based on battery longevity estimates, we predict that by the end of 2024 TTM will no longer be used for device follow-up at our institution.

Atrial Fibrillation: Beyond Rate Control

Atrial fibrillation is the most common cardiac dysrhythmia encountered in the primary care setting. Although a rate control strategy is pursued by physicians for the initial treatment of atrial fibrillation, the efficacy of a rhythm control approach is often undervalued despite offering effective treatment options. There are many pharmacological therapies available to patients, with drug choice often dictated by safety concerns (toxicities and proarrhythmic adverse effects) as well as patient characteristics and comorbidities. This article presents a simplified approach to understanding the rhythm control strategy, including the advantages and disadvantages of various antiarrhythmic drugs and common drug-drug interactions encountered in the primary care setting.

Abstract 371: Assessment of Catheter Position Above or Below the Aortic Valve by Evaluation of Characteristics of the Local Electro Gram: an Acute Canine Study

Background: Ablation in the sinuses of Valsalva (SoV) within the aorta is fraught with risk, owing to the proximity of the coronary arteries. Assessment of catheter tip position is not very easy at this location owing to complex local anatomy and poor images from available modalities.

Objectives: We propose the use of novel local unipolar electrogram characteristics using a new signal recording system to guide the assessment of catheter tip position in this region.

Methods: We recorded unipolar signals from above the SoV, within the coronaries and below the SoV using the PURE-EP™ (BioSig Technologies, MN) signal processing system in 4 anesthetized canines in the setting of an acute study. We used fluoroscopy, intracardiac echocardiography and angiography for confirmation of the position of the catheter tip. We recorded changes in the signals when transitioning between (1) the coronary arteries and the SoV and (2) the SoV and below the SoV.

Results: The unipolar signal showed a negative current of injury (COI) when the catheter tip was present in the SoV, whereas within the coronary artery or below the SoV, the COI was positive. We propose that the difference in the distribution of ventricular muscle below and above the SoV is responsible for this phenomenon. These changes in the COI were noted immediately when transitioning from one location to another and were present reproducibly in all the dogs. ( Figure 1 )

Conclusions: Analysis of the changes on the local electrogram can provide information about the location of the catheter tip which could prove critical in saving lives.

Abstract 55: Use of a Novel Electrogram Filter to Visualise the Conduction Tissue Signals in the Ventricle in Sinus Rhythm and Arrhythmia: Canine Studies

Background: Conduction tissue in the ventricles is closely intertwined with myocardium. Owing to high velocity of conduction, there is near simultaneous activation , making it difficult to discern. Restricted sampling rates and limited dynamic range make real time signal processing challenging for these signals in routine recording systems.

Objectives: We aimed to use novel signal processing techniques in a new system to isolate the conduction tissue signals from the rest of the myocardial activation.

Methods: We used the PURE-EP™ (BioSig Technologies, MN) signal processing system to record endocardial and epicardial signals from 6 anesthetized canines in an acute study setting. A novel filter based on proprietary algorithms to isolate the high frequency signal was applied at sites where the electrogram signals were thought to have a conduction tissue component to them. . In addition, ventricular fibrillation (VF) was induced at the end of the experiment and signals were then recorded from the endocardium and the conduction system.

Results: This filter was successfully able to isolate conduction tissue signals in the myocardium from those of the ventricular muscle. It did over sense atrial signals at the basal left ventricular septum owing to the high frequency components of the atrial signal at this location. When applied to epicardial signals, it did not pick up any conduction tissue signals. In VF, we could discern signals originating from the conduction system endocardially. (Figure 1)

Conclusions: This filter can isolate conduction tissue signals from those of the myocardium and may prove to be a useful adjunct in mapping arrhythmias originating near the conduction system.

Initial Experience with the BioSig PURE EP™ Signal Recording System: An Animal Laboratory Experience

Current signal recording and processing systems have come a long way since their initial inception and use. There is, however, still ample scope for improvement, not only in the troubleshooting of their limitations, but also in the expansion of the boundaries in the recording of intracardiac signals. Here, we recount our experience with the use of the PURE EP™ signal recording system (BioSig Technologies, Inc., Minneapolis, MN, USA) in the animal laboratory.