Posterior LA Research Articles

Ventricular Fibrosis Improves Following AF Ablation in Patients with Persistent AF and Heart Failure

Introduction: AF ablation improves symptoms and systolic function in patients with comorbid persistent AF (PeAF) and idiopathic cardiomyopathy (IDCM). We investigated if diffuse ventricular fibrosis, as measured by cardiac MRI, improves in concert with LVEF following catheter ablation. Methods: Patients with IDCM (LVEF≤45%) and PeAF undergoing AF ablation and no contraindication to cardiac MRI (CMR) were prospectively enrolled and implanted with loop recorders. All patients underwent CMR with native ventricular T1 mapping, a histologically validated index of diffuse ventricular fibrosis, and BNP, prior to and at 6 months post ablation. Results: 18 patients were enrolled (age 59 ± 13, 92% male, mean AF duration 12 ± 5.4 months, NYHA class 2.5 ± 0.5, mean heart rate 81 ± 12bpm and LA size: 34 ± 4.0 cm2). All patients underwent catheter ablation (PVI and posterior LA isolation) and were in SR at 6-month follow-up (AF burden <5% in 94% patients). There was a significant improvement in LVEF from baseline (33 ± 8.0% vs 47 ± 11%, p < 0.001) and a reduction in BNP (-351 ± 213 vs 109 ± 100 ng/L, p < 0.001) and NYHA class (2.5 ± 0.5 vs 1.3 ± 0.6, p < 0.001). This was associated with reduction in average native T1 time from baseline to 6 months (1285 ± 120ms vs 1199 ± 73ms, p = 0.014). Conclusion: Recovery of LVEF in patients with PeAF and IDCM undergoing AF ablation is associated with a shortening of native T1 times consistent with regression of ventricular fibrosis. The restoration of SR with AF ablation promotes reverse ventricular structural remodelling in patients with IDCM and PeAF.

Panoramic characterization of endocardial left atrial activation during human persistent AF: Insights from non-contact mapping

The relative importance of focal drivers, multiple wavelets, rotors and endocardial-epicardial circuits in the maintenance of persistent AF remains unclear. Our objective was to characterize AF wavefront (WF) dynamics during persistent AF. The Ensite 3000 (St Jude Medical) non-contact mapping system was used to map the LA of 15 patients with persistent AF. Wavefronts were classified into planar WFs, rotors or focal WFs. For each new WF the site of origin, the unipolar electrogram, and propagation patterns were determined. AF was characterized by highly unstable patterns of activation with random combinations of 1-2 propagating planar wavefronts alternating with focal activations in a dynamic process. Stable reentry circuits and rotors were never seen. A total of 499 wavefront patterns were analyzed in this study (416 planar wavefronts and 83 focal wavefronts). In an individual patient planar WFs accounted for 67±35% of activations with lifespans of 98±86ms. Focal activations accounted for 29.7±33.5% of activations with lifespans of 76±95ms. The most common sites for new WF generation were the PVs (33%), LA roof (23%), anterior LA (15%), LAA (11%), and posterior LA (8%). The most common unipolar electrogram morphologies observed were QS pattern (34%), rS (29%), CFAE (26%), QR (7%) and Rs (4%), suggesting that WFs may originate from both the endocardial and epicardial surfaces. Human persistent AF is characterized by the formation of highly unstable WFs consisting of various combinations of one to two planar WFs and brief focal activations without any evidence of rotors or sustained focal sources.

18-06: AF Voltage as a Functional Marker for Atrial Fibrosis: Assessing the spatio-temporal correlation of low voltage regions during AF vs SR with late-gadolinium enhanced CMRI defined fibrosis in patients with persistent AF

Background: Endocardial voltage and late-gadolinium enhancement (LGE) are utilised as surrogate markers of fibrosis. Ablation of low voltage regions in PsAF has shown promising results, and LGE-CMRI defined scar guided ablation will be investigated in DECAAFII. We have reported the lack of correlation between AF voltage mapped over 1-2 AF cycles and LGE-scar. We hypothesised that increasing the sampling duration of AF voltage mapping allows for more accurate representation of the underlying structural substrate defined by LGE CMRI. Methods: Ten patients undergoing PsAF ablation underwent pre-procedural LGE-CMRI. Intra-procedural bipolar voltage mapping in AF was performed over 8s during 2 different AF epochs, where the mean peak-to-peak voltage (AF-V) at each site evaluated offline. A subset of patients underwent SR voltage (SR-V) mapping. Only data from the posterior LA wall as analysed as they represent best fidelity. The AF-V and SR-V in areas of LGE-scar, and areas of overlap of low voltage (LVA) (MPV <0.4mV) and LGE-scar, were quantified. Reproducibility of the AF-V (with varying sampling durations) over 2 distinct AF epochs was also evaluated.

Modification of the structural and functional response of the heart and systemic hemodynamics to the cardioselective β1-blockers in patients with arterial hypertension and adaptation to cold

We investigated the features of the structural and functional organization of the left heart (ventricle—LV, atrium—LA) and the state of systemic hemodynamics at rest and in response to a single dose of cardioselective β1-blocker (BB) Egilok. We examined the patients with stage II (1–2 degrees) of arterial hypertension (AH); the study was performed in summer and winter in the northern regions of Russia. It was found that the process of adaptation to cold is accompanied by the inhibition of the pacemaker, a decrease in the rate of active diastolic blood filling of the LV and transaortic blood flow in the aortic root (VAo), an increase in the contractility of the LV posterior wall and interventricular septum (IVS). The negative chronotropic cardiac effect in these conditions results in the reduction of heart productivity per minute in 65% of cases. In winter we observed a more pronounced diastolic LV dysfunction and a decrease in the connectivity of active relaxation of LV posterior wall and LA walls with certain structural and functional cardiac parameters. In contrast to summer, in winter period BB causes a decrease in the active relaxation of LA walls and IVS and LA contractility, which leads to a decrease in the blood filling of passive and active LV. At the same time, LV systolic function (ejection fraction, VAo) and the rhythm and the performance of the heart (stroke volume and cardiac output) decreases; the hypotensive effect accompanied by an increase in peripheral vascular resistance is more pronounced. In winter, the effect of BB reduces the correlation between IVS and LV posterior wall contractions, but the feedback rate or passive to active LV diastolic hyperemia and after load increases. We suggest that in winter component “contractile apparatus” retains its the leading role in the organization of intracardiac response to the BB in patients with hypertension; in addition, new dominant components were formed: “contingency of the LV wall contraction with afterload” and “reverse contingency of early and late diastolic LV function.”

Abstract 13074: Convergent Ablation for Long-Standing Persistent Atrial Fibrillation: Single Center Experience From a Large Regional Medical Center

Introduction: The treatment of long-standing, persistent AF is challenging. Conventional transvenous radiofrequency (RF) ablation strategies have provided only modest success, often requiring multiple procedures to maintain normal sinus rhythm. The convergent ablation procedure is a hybrid approach, involving a minimally invasive epicardial ablation combined with a traditional transvenous endocardial ablation. This comprehensive approach may offer a more effective treatment for long-standing persistent AF. Methods: From 12/2013 through 05/2015, we performed 50 convergent ablations (40 male; 10 female) for symptomatic, long-standing persistent AF. Mean age was 64.1±9.2 years with a mean CHADS-VASC score of 2.5±1.5. Mean LA volume was 161.5±44.5 cc. Mean weight was 103.3 kg ± 23.1 kg, and mean LVEF was 51.7%±21.7%. All patients had failed at least one anti-arrhythmic medication. Epicardial ablation was performed via a sub-xyphoid, endoscopic approach followed by transvenous endocardial ablation (32 RF and 18 cryoablation). Transvenous cavo-tricuspid isthmus (CTI) ablation was performed in all patients using RF energy. Results: Mean procedural time was 2.4±0.6 hours (epicardial) and 2.9±0.75 hours (endocardial). Acute procedural success was 100%, defined as complete pulmonary vein isolation, comprehensive ablation of the posterior LA, and CTI block. Mean hospital stay was 3.4±1.7 days. At mean follow-up of 206±150 days, 47 remain in NSR (94%). Of those patients who underwent transvenous radiofrequency (RF) ablation, 29 of 32 were in sinus rhythm (91%), while 18 of 18 of those who underwent cryo-ablation were in sinus rhythm (100%). At last follow-up, anti-arrhythmic therapy was discontinued in 22 patients (44%). Major complications occurred in 2 patients (4%): rectus hematoma and pericardial tamponade. Conclusions: Convergent ablation is an effective treatment for long-standing persistent AF, demonstrating high success rates with low complication rates. Longer follow-up and prospective, randomized trials are needed.

A Case of Esophageal Thermal Injury Following Radiofrequency Catheter Ablation Therapy

Introduction: Radiofrequency ablation (RFA) is a catheter based ablation technique used in patients with atrial fibrillation(AF) to achieve rhythm control.There is risk of esophageal thermal injury during RFA to the posterior left atrium given its close proximity to the anterior esophagus.We describe a case of thermal injury to the esophagus following RFA therapy to the left atrium. Case Report: A 69-year-old female with a history of hypertension, AF was seen with a two day history of melena.The patient's melenic stools began one day following RFA therapy.The patient reported a “gassy feeling” in her stomach but denied abdominal pain,nausea,vomiting,chest pain,heartburn,dysphagia,o dynophagia,fever/chills.No history of GI bleed or change in stool consistency/color were reported in the past.On exam patient was afebrile,hypertensive(178/78) with heart rate of 80. Abdomen was soft/nontender/nondistended with normoactive bowel sounds, no abdominal masses, organomegaly. Lungs were clear to ausculation as no abnormal heart sounds were noted. Lab results demonstrated Potassium 3.5mmol/L,Sodium 142mmol/L,Chloride 102mmol/L,hemoglobin 13.9 g/dL,platelet count 219 10(3)/mcl,PT 15.6, INR 1.4,PTT 31.5.Liver enzymes were normal.An EGD demonstrated a 6-7 mm healing ulcer in the mid esophagus with no evidence of active bleeding.The submucosa was not seen and no evidence of perforation was noted.She was discharged home with pantoprazole 40mg twice daily,sucralfate 1g four times daily and instructions to follow up in the GI clinic. Discusion: Esophageal injury is one complication of RFA therapy.This is due to the close anatomical proximity between the esophagus and the posterior LA wall which is estimated to be ≤ 5 mm in 40% of the population.The intestinal tissue is also far more susceptible to radiofrequency induced thermal injury than the muscular tissue of the heart. Therefore,direct contact of a probe is not required for thermal injury, as convection heat generated within the LA is enough energy to cause esophageal injury.Early diagnosis is vital to prevent fatal outcomes from complication such as perforation and fistula formation. Atrial fibrillation is projected to surge 2.5-fold in the near future due to the aging demographic leading to an increase use of RFA therapy. This may result in a higher incident of RFA related thermal esophageal injury.Further research is needed to identify risk factors,preventive strategies and optimal treatment for esophageal thermal injury related to left atrial RFA.Figure 1

Electrophysiological, Electroanatomical, and Structural Remodeling of the Atria as Consequences of Sustained Obesity

Obesity and atrial fibrillation (AF) are public health issues with significant consequences. This study sought to delineate the development of global electrophysiological and structural substrate for AF in sustained obesity. Ten sheep fed ad libitum calorie-dense diet to induce obesity over 36 weeks were maintained in this state for another 36 weeks; 10 lean sheep with carefully controlled weight served as controls. All sheep underwent electrophysiological and electroanatomic mapping; hemodynamic and imaging assessment (echocardiography and dual-energy x-ray absorptiometry); and histology and molecular evaluation. Evaluation included atrial voltage, conduction velocity (CV), and refractoriness (7 sites, 2 cycle lengths), vulnerability for AF, fatty infiltration, atrial fibrosis, and atrial transforming growth factor (TGF)-β1 expression. Compared with age-matched controls, chronically obese sheep demonstrated greater total body fat (p < 0.001); LA volume (p < 0.001); LA pressure (p < 0.001), and PA pressures (p < 0.001); reduced atrial CV (LA p < 0.001) with increased conduction heterogeneity (p < 0.001); increased fractionated electrograms (p < 0.001); decreased posterior LA voltage (p < 0.001) and increased voltage heterogeneity (p < 0.001); no change in the effective refractory period (ERP) (p > 0.8) or ERP heterogeneity (p > 0.3). Obesity was associated with more episodes (p = 0.02), prolongation (p = 0.01), and greater cumulative duration (p = 0.02) of AF. Epicardial fat infiltrated the posterior LA in the obese group (p < 0.001), consistent with reduced endocardial voltage in this region. Atrial fibrosis (p = 0.03) and TGF-β1 protein (p = 0.002) were increased in the obese group. Sustained obesity results in global biatrial endocardial remodeling characterized by LA enlargement, conduction abnormalities, fractionated electrograms, increased profibrotic TGF-β1 expression, interstitial atrial fibrosis, and increased propensity for AF. Obesity was associated with reduced posterior LA endocardial voltage and infiltration of contiguous posterior LA muscle by epicardial fat, representing a unique substrate for AF.

26Good medium term success of convergent hybrid AF ablation in persistent AF

Introduction: Catheter ablation of persistent and long-standing persistent AF ablation has significantly worse success rates than for paroxysmal AF with only about 50% of patients remaining in SR at 12 months. This has led to the development of a number of alternative treatment strategies. The Convergent AF ablation is a minimally invasive surgical epicardial ablation (providing a box lesion to isolate the posterior LA) with an endocardial approach to isolate the pulmonary veins. 80% maintenance of SR has been reported in small European/US studies and here we report our medium term results as the 1stparticipating UK centre. Patient Selection: 17 patients with symptomatic persistent and long-standing persistent AF have undergone a Convergent AF ablation since July 2012. They were selected due to adverse success features for endocardial ablation (AF duration, LA size, multiple failed catheter ablations etc). Mean age was 64 years (43-82), average AF duration 6.7 years, 8 patients had previously failed persistent AF ablations, mean LA diameter 45mm (4 patients >50 mm, 2 patients >60mm), LVEF 51% (25-60%). Results: SR at discharge was achieved in all patients. Early recurrences (<6 months) were relatively common (42%, AF n=2, Aflutter n=4, with 5 patients requiring elective DCCV and 1 spontaneously cardioverted). Subsequent practice change led to antiarrhythmics being continued for 6 months post procedure. Despite these early recurrences longer term SR maintenance was good (electrocardiogram evidence of SR at 3, 6, 9, 12 and 18 months were 8/14 (57%), 10/14 (71%). 7/8 (88%), 7/8 (86%) and 2/2 (see figure for rhythm breakdown). Holter monitoring confirmed SR in 7/8 (88%) at 12 months (6/8 in SR off antiarrhythmics). Mean follow up was 11.4 months. In total 7 patients underwent DCCV during follow-up and there have been no repeat ablations. Procedural complications were 1 wound infection and 1 coronary sinus bleed (sutured laparoscopically during the procedure). Conclusions: The Convergent Hybrid AF ablation appears to be a good treatment option for persistent AF. Despite relatively common early recurrences the medium term success rates were better than predicted by standard therapy, even in our patient group with multiple adverse features. ![Graphic][1] [1]: /embed/inline-graphic-1.gif

Abstract 198: Noninvasive Approach Assessing Atrial Mechanics and Serum Biomarkers of Collagen Turnover Provides a Surrogate for Fibrosis and Atrial Fibrillation

Introduction: Atrial fibrosis alters myocardial electrophysiological properties, increasing susceptibility to postoperative atrial fibrillation (PoAF); however, its estimation is problematic. We hypothesized that a noninvasive approach using history of AF (HxAF), LA mechanics and serum biomarkers of collagen turnover provides a surrogate for the extent of interstitial atrial fibrosis to identify patients at risk for PoAF. Methods: In patients undergoing cardiac surgery from April-Dec 2013, concentrations of biomarkers reflecting collagen synthesis/degradation and extracellular matrix remodeling were determined in serum from preoperative blood using an enzyme-linked immunosorbent assay, and echocardiographic evaluation was performed using M-mode, 2D, Doppler and 3D speckle tracking. Results: Of 66 patients (68 ±11 y, 67% men), 15 had HxAF and 11 of 51 with no HxAF (22%) developed new onset PoAF. In patients with HxAF, biomarkers for collagen turnover were elevated (Fig A) and correlated with a reduction in LA ejection fraction and global and regional relaxation of the LA wall (p=0.01, Fig B). In patients with no HxAF, procollagen type III (PIIINP) was significantly different in those who developed PoAF (p=0.01) and correlated with reduction in contractility in the posterior LA roof (p=&lt;0.001) with a prolonged time to peak end-diastolic volume (p=0.03). LA size or ventricular structure and function were not different between groups. Conclusion: Surrogate serum and imaging biomarkers correlate with the substrate abnormality that promotes AF. These results need to be validated in larger cohorts to assess the power of these parameters in predicting new onset PoAF.

Epicardial wave mapping in human long-lasting persistent atrial fibrillation: transient rotational circuits, complex wavefronts, and disorganized activity

To characterize the nature of atrial fibrillation (AF) activation in human persistent AF (PerAF) using modern tools including activation, directionality analyses, complex-fractionated electrogram, and spectral information. The mechanism of PerAF in humans is uncertain. High-density epicardial mapping (128 electrodes/6.75 cm(2)) of the posterior LA wall (PLAW), LA and RA appendage (LAA, RAA), and RSPV-LA junction was performed in 18 patients with PerAF undergoing open heart surgery. Continuous 10 s recordings were analysed offline. Activation patterns were characterized into four subtypes (i) wavefronts (broad or multiple), (ii) rotational circuits (≥2 rotations of 360°), (iii) focal sources with centrifugal activation of the entire mapping area, or (iv) disorganized activity [isolated chaotic activation(s) that propagate ≤3 bipoles or activation(s) that occur as isolated beats dissociated from the activation of adjacent bipole sites]. Activation at a total of 36 regions were analysed (14 PLAW, 3 RSPV-LA, 12 LAA, and 7 RAA) creating a database of 2904 activation patterns. In the majority of maps, activation patterns were highly heterogeneous with multiple unstable activation patterns transitioning from one to another during each recording. A mean of 3.8 ± 1.6 activation subtypes was seen per map. The most common patterns seen were multiple wavefronts (56.2 ± 32%) and disorganized activity (24.2 ± 30.3%). Only 2 of 36 maps (5.5%) showed a single stable activation pattern throughout the 10-s period. These were stable planar wavefronts. Three transient rotational circuits were observed. Two of the transient circuits were located in the posterior left atrium, while the third was located on the anterior surface of the LAA. Focal activations accounted for 11.3 ± 14.2% of activations and were all short-lived (≤2 beats), with no site demonstrating sustained focal activity. Human long-lasting PerAF is characterized by heterogeneous and unstable patterns of activation including wavefronts, transient rotational circuits, and disorganized activity.

Abstract 9976: Human Atrial Fibrillation Initiates by Formation of a Dominant Spiral Wave at the Site Where Triggers Cause Dynamic Conduction Slowing

Introduction Triggers may initiate human atrial fibrillation (AF), but by unclear mechanisms. We hypothesized that triggers would dynamically slow atrial conduction velocity, to enable the formation of a single localized spiral wave or repetitive focal beat that may drive the atria into AF. Methods We studied 13 patients at clinically-indicated AF ablation (5 persistent, age 63±11 years, LA size 43±6mm) in whom we placed 64-pole basket catheters (Boston Scientific, Natick, MA) in both atria. AF was initiated by accelerating pacing initially from 120 beats/min to AF onset. We constructed isochronal maps of both atria for beats leading to and including the first cycles of AF. We computed conduction time to each bi-atrial electrode at each rate, thus defining rate-dependence (restitution) of conduction throughout the atria. Results AF initiated in the left atrium in 13/13 patients. Notably, atrial conduction slowed dynamically with rate at the site of AF onset in 8 patients, either gradually (Figure A) or abruptly. In all patients, spatial mapping showed that triggers initiated AF at a site of dynamic conduction slowing (76%±60%) by the formation of a single spiral wave (n=7; figure B) or repetitive focal beat (n=1). Notably, these regions were not the slowest to activate at baseline. Figure A shows dynamic conduction velocity slowing only at faster rates (Fig A, steep curve) at a site in the septal posterior LA, which enabled block (Figure B, site marked *) and formation of a spiral wave (Fig B, curved arrow) that initiates AF. Conclusions Triggers initiate human AF by causing dynamic conduction slowing, enabling the formation of a single reentrant spiral wave (or repetitive focal beat) that drives the atria into AF. Of note, these sites did not exhibit conduction slowing at baseline, showing the central dynamic role of the trigger in AF initiation. Future studies should modulate conduction slowing from a trigger to prevent AF initiation.

Early Experience with Robotic Navigation for Catheter Ablation of Atrial Fibrillation – Initial Procedural Details and Outcomes

Results: PV anatomy was conventional (two left, two right) in 35 patients with the next most common variant two left and three right veins (nine patients). The oesophagus was midline in 27 patients, closer to the left veins in 17, to the right in nine. Linear delayed enhancement (DE) frequently seen in the anteriorwall, septum,posteriorwall and lateral wall (table below). Septal Anterior Posterior Lateral LA appendage Roof Inferior Linear DE 22 25 19 22 1 1 2 Conclusion: Cardiac magnetic resonance imaging can provide useful anatomical information for guidance of atrial fibrillation ablation. The distribution of atrial scarring can help in selection of themost appropriate ablation strategy. doi:10.1016/j.hlc.2011.05.231

Noninvasive real-time mapping of an incomplete pulmonary vein isolation using electrocardiographic imaging

Establishing entrance and exit block from pulmonary veins is an endpoint for pulmonary vein isolation (PVI) procedures (1). Reestablished pulmonary vein connection is a common cause of atrial fibrillation (AF) recurrence in patients who have previously undergone PVI. Here we provide images from a noninvasive cardiac electrophysiology imaging system (ECGI) performed during PVI. The ECGI procedure has been described previously (2) (3). 250 carbon electrodes were applied to the patient’s torso before a pre-procedural contrast-enhanced CT scan, which provided torso-electrode positions and atrial geometry in the same reference frame. The electrodes were removed, then replaced on the day of the PVI procedure in the same configuration, and remained on the patient throughout the procedure. ECGI performed during the procedure noninvasively generated epicardial isochrone activation maps. After circumferential ablation around the antrum of the right pulmonary veins, a lasso catheter in the right inferior pulmonary vein (RIPV) demonstrated entrance block. However, high-output pacing from within the RIPV captured the atrium, revealing incomplete exit block. Panel A displays the real-time ECGI isochrone map during RIPV pacing, showing earliest activation in the superior-posterior antrum of the RIPV (red is earliest), with radial spread across the posterior LA. A 60-ms delay is seen from the pacing breakthrough (red) to posterior LA (green) activation, consistent with incomplete line of block created by the ablation. The invasive electroanatomic map (Panel B) shows the final ablation lesion set and the additional ablation necessary for exit block from the RIPV (pink marker). This location on the invasive electroanatomic map corresponds closely to the exit site determined by ECGI in Panel A. Panel C shows an ECGI isochrone map during high-output pacing from within the RIPV after the complete ablation. Pacing failed to capture the atrium, and the earliest LA activation in sinus rhythm was near Bachmann’s bundle (red). Posterior LA activation is limited superiorly and inferiorly with lines of block (white dotted lines) corresponding to the ablation lines on the LA roof and posterior wall seen in panel B. Three PV’s also demonstrate electrical isolation (blue). Although the RSPV in Panel C appears to have electrical connection in sinus rhythm, the appearance of activation is due to far-field signal from the posterior right atrium in close proximity. Invasive testing of the RSPV demonstrated entrance and exit block. Rigorous prospective study is needed, but if real-time ECGI can accurately identify areas of incomplete PVI isolation, it may shorten procedure time and improve long-term success rates by pinpointing sites of incomplete linear ablation.

Dominant frequency differences in atrial fibrillation patients with and without left ventricular systolic dysfunction

The aim of this study was to determine the mechanisms of atrial fibrillation (AF) in patients with left ventricular systolic dysfunction (LVSD). Dominant frequency (DF) spatiotemporal stability was studied in 15 patients with persistent AF (PEAF) and LVSD (Group I), 15 with PEAF without LVSD (Group II), and 10 with paroxysmal AF (PAAF) without LVSD (Group III). Dominant frequencies were analysed at 536 sites at baseline (DF1) and 26 +/- 12 min later (DF2). A DF1-DF2 difference of <or=0.5 Hz was found in 77, 70, and 48% of sites in Groups I, II, and III (P < 0.001). Maximal DF1 and DF2 were recorded at the same site in 12/15, 11/15, and 0/10 patients in Groups I, II, and III, respectively (P < 0.01). Gradient differences: Group I, DFs were higher at left atrium appendage (LAA) than at anterior (A) LA (ALA), pulmonary vein-left atrial junction (PV-LAJ), and posterior (P) LA (PLA) (7.4 +/- 1.1 vs. 6.6 +/- 1 vs. 6.8 +/- 0.8 vs. 6.8 +/- 0.7 Hz, P < 0.05); Group II, no differences; Group III, DF was higher at PV-LAJ than at LAA, AL, and PLA (6 +/- 1.2 vs. 5.3 +/- 1.1 vs. 5.2 +/- 0.9 vs. 5.4 +/- 1.1 Hz, P < 0.05). Dominant frequency stability supports stable arrhythmia sources as the mechanism of PEAF with (without) LVSD, but not of PAAF.

Abstract 2250: Is Atrial Fibrillation in Hypertrophic Cardiomyopathy Due to Left Atrial Structural Remodeling as Determined by Speckle-Derived Atrial Strain Imaging?

Background: Atrial fibrillation (AF) is common in HCM yet the mechanisms are poorly understood but are likely secondary to either the consequences of left atrial structural remodeling (LASR) or myopathy, or triggers arising from pulmonary and other thoracic veins. The presence and severity of LASR as characterized by left atrial strain (LA ϵ), and its relationship to AF in HCM, has not been determined. Therefore, we measured LA ϵ and strain rate (SR) in Pts with HCM both with (AF+) and without (AF−) prior AF and compared these measures to those in age and gender matched controls without HCM or AF. Methods: Two-dimensional speckle-derived LA longitudinal peak ϵ, SR during systole (SR S ), early (SR E ) and late diastole (SR A ) were measured at the basal and mid portions of the lateral, septal, and posterior LA walls using Vector Velocity Imaging during sinus rhythm and were averaged. Results: Mean age of Pts in each of the matched groups was 56 ± 2 years (16 males; 59%). Significant left ventricular outflow tract obstruction was present in all Pts with HCM. Diastolic dysfunction was similar in both HCM groups and worse when compared to controls. Peak LA 3 , SR S , SR E , and SR A for each group is shown (table 1 ). HCM was associated with significantly lower LA ϵ and SR compared to controls. Although LA size was increased in Pts with HCM when compared to controls there was no correlation between LA size and ϵ or SR (p&gt;0.05 for all). No differences in LA ϵ and SR were found between AF+ versus AF− Pts. Conclusion: HCM is associated with LASR as determined by decreased LA ϵ and SR. However, LA ϵ and SR were similar in AF+ versus AF− Pts suggesting that the occurrence of AF in HCM is not due to LASR alone. Table 1. Left Atrial Strain and Strain Rate in Hypertrophic Cardiomyopathy

Isolating the Posterior Left Atrium and Pulmonary Veins with a “Box” Lesion Set: Use of Epicardial Ablation to Complete Electrical Isolation

Similar to the surgical mini-maze procedure, the posterior "box" lesion set employs linear ablation lesions along the anterior aspects of both sets of PVs connected by a roof line and an inferior line to electrically isolate the PVs and complete posterior LA wall en masse. However, creating fully transmural linear atrial lesions can be difficult to achieve, even with an irrigated ablation catheter. This report details a case wherein a combined endocardial and epicardial approach was required to create an electrically continuous posterior box lesion in a patient with persistent AF.

Abstract 2023: Effect Of Chronic Stretch Reversal On Atrial Remodeling In Humans: Implications For The Atrial Fibrillation Substrate

Background : Chronic atrial stretch is an important determinant for atrial fibrillation (AF). Whether relief of stretch reverses the substrate predisposed to AF is unknown. Methods: Twenty one pts (31±9 years) with mitral stenosis (MS; MVA 0.89±0.1cm 2 ) undergoing mitral commissurotomy (MC) were studied by electrophysiological or electroanatomical mapping of both atria before and after MC. Multipolar catheters were placed in the lateral RA, Crista (CT), coronary sinus (CS), septal RA and LA. We measured: effective refractory period (ERP) at the LA appendage, septal/lateral LA roof, posterior LA, inferior LA, proximal/distal CS, low/high LRA and SRA at 600 and 450ms; P wave duration (PWD); double potentials (DP) or fractionated signals (FS) along CT; and conduction time along CS, LRA, inferior LA and LA roof. Activation and voltage maps were created to evaluate changes in conduction and voltage. In 14 pts, RA studies were repeated ≥6 months after MC. Results : Following MC, there was significant increase in MVA (2.1±0.3 cm 2, p&lt;0.0001) with decrease in LA (23±8 to 10±4 mmHg, p&lt;0.0001) and PA pressures (38±17 to 27±14mmHg, p&lt;0.0001) and LA volume (75±12 to 52±13ml, p&lt;0.0001). This was associated with no change in ERP and No. of DP/FS along the CT but with reduction in PWD (139±19 to 135±20ms, p=0.047), increase in conduction velocity (CV) in LA (1.3±0.3 to 1.7±0.2m/s, p=0.005) and RA (1.0±0.1 to 1.3±0.3 m/s, p=0.007) and increase in LA voltage (1.7±0.6 to 2.5±1.0 mV, p=0.05). Late after MC, there was a further decrease in PWD and RA ERP, with increase in RA CV (1.0±0.1 to 1.3±0.2 m/s, p=0.01) and voltage (1.7±0.7 to 2.8±0.6 mV, p=0.004) but with no change in other parameters. See table for details of pts studied late after MC. Conclusion: The electrophysiologic and electroanatomic abnormalities within the atria that result from MS are reversed after MC. These observations suggest that the substrate predisposing to atrial arrhythmias may be reversed. Results

Abstract 1367: Altered Transmural Expression Of I Kr In Cardiac Memory Is Regulated By The Transcription Factor, Activator Protein-1

Introduction: We previously reported that the transient outward current (I to ) and mRNA and protein levels of its accessory subunit KChIP2 decrease in ventricular pacing-induced cardiac memory (CM). These changes appear dependent on a decrease of the cAMP response element binding protein (CREB). We have also reported that the transmural gradients of the delayed rectifier potassium current component, I kr and the mRNA and protein of its subunit ERG (all showing epicardium (EPI) &gt; endocardium (ENDO)), are diminished in CM. However, there is no CREB binding site in the ERG promoter region to explain the change in ERG. We now tested the hypothesis that 1) the normal transmural gradient of ERG expression in canine left ventricle (LV) is paralleled by a transmural gradient of the Activator protein-1 (AP-1) components c-Jun and c-Fos, and 2) altered transmural expression of c-Jun and c-Fos parallels the altered transmural ERG in CM. Methods: We screened 2000bp upstream from the first exon of ERG for transcription factor binding sites. Then 10 dogs were chronically instrumented with LV posterior wall and LA pacing electrodes. Five underwent 3w AV-sequential pacing (CM), and 5, 3w of atrial pacing (Sham). CM was quantified as change in T wave vector displacement (TVD). At 3w biopsies were taken 1–2 cm from the LV pacing site. Real time PCR was used to determine c-Jun and c-Fos. Results: Screening revealed an AP-1 response element upstream to the ERG promoter region, supporting the hypothesis that c-Jun and c-Fos might be reasonable candidate transcription factors here. TVD increased in CM compared to Sham. As previously, mRNA and protein transmural gradients of ERG decreased in CM. C-jun and c-Fos exhibited transmural gradients, EPI&gt;ENDO, in Sham (Table ). This gradient was lost in CM. Conclusion AP-1 is a transcription factor for ERG and the altered ERG transmural gradient in CM may be regulated by the altered c-Jun and c-Fos gradient. T vector displacement (TVD) and mRNA of c-Jun and c-Fos

Lethal atrioesophageal fistula after pulmonary vein isolation using high-intensity focused ultrasound (HIFU)

d e d 1 f ( s o s n M w t w p a u D c a R j e e p r t r a a R s 5 e s ntroduction eft atrial (LA) catheter ablation has become a successful herapy for patients with atrial fibrillation (AF) and is conidered a class IIa indication by the recently published CC/AHA/ESC guidelines for the management of patients ith this arrhythmia. To minimize the risk of pulmonary ein (PV) stenosis, the currently preferred approach consists f the creation of circular lesions at the PV antrum for PV solation (PVI). As a consequence of the close vicinity of he posterior LA to the esophagus, thermal injury of the sophagus with development of atrioesophageal fistula AEF) has been reported after surgical radiofrequency (RF) blation and, more recently, after percutaneous catheterased interventions. To enhance the safety and efficacy of VI, new energy sources such as cryoablation have been ested, as well as, more recently, high-intensity focused ltrasound (HIFU). Until now, major complications with IFU have been limited to transient or permanent phrenic erve palsy during ablation of the right superior PV RSPV), and one case of right femoral artery pseudoaneuysm was described. We report for the first time the develpment of an AEF after PVI using a HIFU balloon catheter.

Normal Atrial Activation and Voltage During Sinus Rhythm in the Human Heart: An Endocardial and Epicardial Mapping Study in Patients with a History of Atrial Fibrillation

The three-dimensional contributions to human atrial activation in sinus rhythm have not been specifically characterized. We evaluated the sequence of endocardial and epicardial activation and voltage of the atria during normal sinus rhythm. The study group includes 35 patients with history of symptomatic atrial fibrillation. Prior to catheter ablation of atrial fibrillation, we performed multielectrode electroanatomic mapping during sinus rhythm, endocardially of the RA, LA, and coronary sinus (CS) and, in 10 patients, epicardially of the transverse sinus and oblique sinus. Following activation of the atrial region of the sinus node, the epicardial transverse sinus was activated 11 +/- 18 msec later, while the earliest endocardial LA activation occurred in the region of Bachmann's bundle at 31 +/- 13 msec, significantly earlier than the earliest epicardial LA activation of the oblique sinus at 54 +/- 10 msec (P < 0.002). The posterior LA revealed complex types of activation in 66% of patients analyzed, due to the convergence of wavefront propagation from the CS, oblique sinus, and endocardial LA. Bipolar voltage measurements revealed significantly higher values for the epicardium (mean 3.05 +/- 1.31 mv) than for the endocardium (mean 1.65 +/- 0.75 mv), P < 0.0001 between both groups. In sinus rhythm, we have characterized endocardial and epicardial atrial activation and voltage, and provide an analysis and understanding of the genesis of the P wave complex in humans.