Intramyocardial mapping of ventricular premature depolarizations via septal venous perforators: Differentiating the superior intraseptal region from left ventricular summit origins.

BACKGROUND: The intramyocardial aspect of the left ventricular summit (LVS) can be mapped by advancing a unipolar guidewire into septal perforator branches of the anterior interventricular vein. OBJECTIVE: The purpose of this study was to differentiate between ventricular premature depolarizations (VPDs) with a basal superior intraseptal (SIS) site of origin and those originating from the epicardial LVS using septal intramyocardial mapping. METHODS: A retrospective cohort of patients with suspected LVS VPDs who underwent SIS unipolar mapping were reviewed for their clinical characteristics, mapping findings, and procedural outcomes. RESULTS: SIS mapping was successful in 44 of 47 cases (93.6%). VPD origin was SIS (defined as earliest activation from the intraseptal wire) in 20 patients (45.5%; median 23 ms pre-QRS). Procedure success was similar in patients with (group 1) and without (group 2) SIS origin (84% vs 87.5%, respectively; P = .842). Of the 10 patients in group 1 without presystolic endocardial activation, 5 (11.3% of all 44 cases) were successfully ablated from the left ventricular endocardium by using an anatomical approach targeting the endocardium closest to the earliest intraseptal activation site. CONCLUSION: A significant proportion (45.5%) of VPDs that appear to arise from the left ventricular summit can be demonstrated to have a SIS origin using septal perforator venous mapping. A significant minority (11.3%) of these can be ablated from the endocardium by targeting from an anatomic vantage point closest to the earliest intraseptal activation site. The described strategy may help differentiate true LVS VPDs from those with SIS sites of origin.

Half-Dose Direct Oral Anticoagulation Versus Standard Antithrombotic Therapy After Left Atrial Appendage Occlusion.

OBJECTIVES: This study evaluated the long-term efficacy of a standard antithrombotic strategy versus half-dose direct oral anticoagulation (DOAC) after Watchman implantation. BACKGROUND: No consensus currently exists on the selection of the most effective antithrombotic strategy to prevent device-related thrombosis (DRT) in patients undergoing endocardial left atrial appendage closure. METHODS: After successful left atrial appendage closure, consecutive patients were prescribed a standard antithrombotic strategy (SAT) or long-term half-dose DOAC (hdDOAC). The primary composite endpoint was DRT and thromboembolic (TE) and bleeding events. RESULTS: Overall, 555 patients (mean age 75 ± 8 years, 63% male; median CHA2DS2-VASc [congestive heart failure, hypertension, age ≥75 years, diabetes mellitus, prior stroke or transient ischemic attack or thromboembolism, vascular disease, age 65-74 years, sex category] score 4 [interquartile range (IQR): 3-6]; median HAS-BLED [hypertension, abnormal renal or liver function, stroke, bleeding, labile international normalized ratio, elderly, drugs or alcohol] score 3 [IQR: 2-4]) were included. Patients were categorized into 2 groups (SAT: n = 357 vs hdDOAC: n = 198). Baseline clinical characteristics were similar between groups. The median follow-up duration was 13 months (IQR: 12-15 months). DRT occurred in 12 (2.1%) patients, all in the SAT group (3.4% vs 0.0%; log-rank P = 0.009). The risk of nonprocedural major bleeding was significantly more favorable in the hdDOAC group (0.5% vs. 3.9%; log-rank P = 0.018). The rate of the primary composite endpoint of DRT and TE and major bleeding events was 9.5% in SAT patients and 1.0% in hdDOAC patients (HR: 9.8; 95% CI: 2.3-40.7; P = 0.002). CONCLUSIONS: After successful Watchman implantation, long-term half-dose DOAC significantly reduced the risk of the composite endpoint of DRT and TE and major bleeding events compared with a standard, antiplatelet-based, antithrombotic therapy.

First-line ablation of ventricular tachycardia in ischemic cardiomyopathy: stratification of outcomes by left ventricular function.

PURPOSE: First-line catheter ablation of ventricular tachycardia/ventricular fibrillation (VT/VF) in patients with ischemic cardiomyopathy (ICM) has been associated with improved outcomes; however, most benefit seems to be in patients with moderately depressed left ventricular ejection fraction (LVEF). Herein, outcomes were stratified based on LVEF. METHODS: A meta-analysis of randomized controlled trials (RCTs) evaluating first-line ablation versus medical therapy in patients with VT and ICM was performed. Risk estimates and 95% confidence intervals (CI) were measured. RESULTS: Four RCTs with a total of 505 patients (mean age 66 ± 9 years, 89% male, 80% with previous revascularization) were included. Mean LVEF was 35 ± 8%. At a mean follow-up of 24 ± 9 months, a significant benefit in survival-free from appropriate implantable cardioverter-defibrillator (ICD) therapies was observed in all patients undergoing first-line catheter ablation compared with medical management (RR 0.70, 95% CI 0.56-0.86). In patients with moderately depressed LVEF (> 30-50%), first-line VT ablation was associated with a statistically significant reduction in the composite endpoint of survival free from VT/VF and appropriate ICD therapies (HR 0.52, 95% CI 0.36-0.76), whereas there was no difference in patients with severely depressed LVEF (≤30%) (HR 0.56, 95% CI 0.24-1.32). Funnel plots did not show asymmetry suggesting lack of bias. CONCLUSIONS: Patients with ICM and VT undergoing first-line ablation have a significantly lower rate of appropriate ICD therapies without a mortality difference compared with patients receiving an initial approach based on medical therapy. The beneficial effect of a first-line ablation approach was only observed in patients with moderately depressed LVEF (> 30-50%).

Non-pulmonary vein triggers in nonparoxysmal atrial fibrillation: Implications of pathophysiology for catheter ablation.

Rhythm control of persistent atrial fibrillation (AF) patients represents a challenge for the modern interventional cardiac electrophysiologist; as a matter of fact, there is still divergence regarding the best ablative approach to adopt in this population. Different investigational endpoints, variability of techniques and tools, significant technological evolution, and the lack of universally accepted pathophysiological models engendered a considerable heterogeneity in terms of techniques and outcomes, so much that the treatment of persistent subtypes of AF commonly still relies mainly on pulmonary vein (PV) isolation. The purpose of the present review is to report the current experimental and clinical evidence supporting the importance of mapping and ablating non-PV triggers and describe our institutional approach for the ablation of nonparoxysmal AF.

QRS morphology in lead V1 for the rapid localization of idiopathic ventricular arrhythmias originating from the left ventricular papillary muscles: A novel electrocardiographic criterion.

BACKGROUND: Twelve-lead electrocardiogram (ECG) criteria have been developed to identify idiopathic ventricular arrhythmias (VAs) from the left ventricular (LV) papillary muscles (PAPs), but accurate localization remains a challenge. OBJECTIVE: The purpose of this study was to develop ECG criteria for accurate localization of LV PAP VAs using lead V1 exclusively. METHODS: Consecutive patients undergoing mapping and ablation of VAs from the LV PAPs guided by intracardiac echocardiography from 2007 to 2018 were reviewed (study group). The QRS morphology in lead V1 was compared to patients with VAs with a "right bundle branch block" morphology from other LV locations (reference group). Patients with structural heart disease were excluded. RESULTS: One hundred eleven patients with LV PAP VAs (mean age 54 ± 16 years; 65% men) were identified, including 64 (55%) from the posteromedial PAP and 47 (42%) from the anterolateral PAP. The reference group included patients with VAs from the following LV locations: fascicles (n = 21), outflow tract (n = 36), ostium (n = 37), inferobasal segment (n = 12), and apex (5). PAP VAs showed 3 distinct QRS morphologies in lead V1 93% of the time: Rr (53%), R with a slurred downslope (29%), and RR (11%). Sensitivity, specificity, positive predictive value, and negative predictive value for the 3 morphologies combined are 93%, 98%, 98%, and 93%, respectively. The intrinsicoid deflection of PAP VAs in lead V1 was shorter than that of the reference group (63 ± 13 ms vs 79 ± 24 ms; P < .001). An intrinsicoid deflection time of <74 ms best differentiated the 2 groups (sensitivity 79%; specificity 87%). CONCLUSION: VAs originating from the LV PAPs manifest unique QRS morphologies in lead V1, which can aid in rapid and accurate localization.

Beyond Pulmonary Vein Isolation in Nonparoxysmal Atrial Fibrillation: Posterior Wall, Vein of Marshall, Coronary Sinus, Superior Vena Cava, and Left Atrial Appendage.

The optimal ablation strategy for non-paroxysmal atrial fibrillation remains controversial. Non-PV triggers have been shown to have a major arrhythmogenic role in these patients. Common sources of non-PV triggers are: posterior wall, left atrial appendage, superior vena cava, coronary sinus, vein of Marshall, interatrial septum, crista terminalis/Eustachian ridge, and mitral and tricuspid valve annuli. These sites are targeted empirically in selected cases or if significant ectopy is noted (with or without a drug challenge), to improve outcomes in patients with non-paroxysmal atrial fibrillation. This article focuses on summarizing the current evidence and the approach to mapping and ablation of these frequent non-PV trigger sites.

Radiofrequency-Assisted Transseptal Access for Atrial Fibrillation Ablation Via a Superior Approach.

OBJECTIVES: This study describes the technique and outcomes of atrial fibrillation (AF) ablation via a superior approach in patients with interrupted or absent inferior vena cavas (IVCs). BACKGROUND: In patients with interrupted or absent IVCs, transseptal access cannot be obtained via standard femoral venous access. In these patients, alternative strategies are necessary to permit catheter ablation in the left atrium (LA). This study reports on the outcomes of AF ablation from a superior venous access with a radiofrequency (RF)-assisted transseptal puncture (TSP) technique. METHODS: This study identified patients with interrupted or absent IVCs who underwent AF ablation via a superior approach at 2 ablation centers from 2010 to 2019. RESULTS: Fifteen patients (mean age: 50.8 ± 11.2 years; 10 men; 10 with paroxysmal AF) with interrupted or absent IVCs underwent AF ablation with transseptal access via a superior approach. Successful TSP was performed either with a manually bent RF transseptal needle (early cases: n = 4) or using a RF wire (late cases: n = 11); this approach permitted LA mapping and ablation in all patients. Mean time required to perform single (n = 8) or double (n = 7) TSP was 16.1 ± 4.8 min, and mean total procedure time was 227.9 ± 120.7 min (fluoroscopy time: 57.0 ± 28.5 min). LA mapping and ablation were successfully performed in all patients. CONCLUSIONS: In patients with AF undergoing catheter ablation and who had a standard transseptal approach via femoral venous approach is impossible due to anatomic constraints, RF-assisted transseptal access via a superior approach can be an effective alternative strategy to permit LA mapping and ablation.

Characterization of Structural Changes in Arrhythmogenic Right Ventricular Cardiomyopathy With Recurrent Ventricular Tachycardia After Ablation: Insights From Repeat Electroanatomic Voltage Mapping.

BACKGROUND: Data characterizing structural changes of arrhythmogenic right ventricular (RV) cardiomyopathy are limited. METHODS: Patients presenting with left bundle branch block ventricular tachycardia in the setting of arrhythmogenic RV cardiomyopathy with procedures separated by at least 9 months were included. RESULTS: Nineteen consecutive patients (84% males; mean age 39±15 years [range, 20-76 years]) were included. All 19 patients underwent 2 detailed sinus rhythm electroanatomic endocardial voltage maps (average 385±177 points per map; range, 93-847 points). Time interval between the initial and repeat ablation procedures was mean 50±37 months (range, 9-162). No significant progression of voltage was observed (bipolar: 38 cm2 [interquartile range (IQR), 25-54] versus 53 cm2 [IQR, 25-65], P=0.09; unipolar: 116 cm2 [IQR, 61-209] versus 159 cm2 [IQR, 73-204], P=0.36) for the entire study group. There was a significant increase in RV volumes (percentage increase, 28%; 206 mL [IQR, 170-253] versus 263 mL [IQR, 204-294], P<0.001) for the entire study population. Larger scars at baseline but not changes over time were associated with a significant increase in RV volume (bipolar: Spearman ρ, 0.6965, P=0.006; unipolar: Spearman ρ, 0.5743, P=0.03). Most patients with progressive RV dilatation (8/14, 57%) had moderate (2 patients) or severe (6 patients) tricuspid regurgitation recorded at either initial or repeat ablation procedure. CONCLUSIONS: In patients with arrhythmogenic RV cardiomyopathy presenting with recurrent ventricular tachycardia, >10% increase in RV endocardial surface area of bipolar voltage consistent with scar is uncommon during the intermediate term. Most recurrent ventricular tachycardias are localized to regions of prior defined scar. Voltage indexed scar area at baseline but not changes in scar over time is associated with progressive increase in RV size and is consistent with adverse remodeling but not scar progression. Marked tricuspid regurgitation is frequently present in patients with arrhythmogenic RV cardiomyopathy who have progressive RV dilation.

Electrocardiographic and Electrophysiologic Characteristics of Idiopathic Ventricular Arrhythmias Originating From the Basal Inferoseptal Left Ventricle.

OBJECTIVES: This study sought to characterize ventricular arrhythmia (VA) ablated from the basal inferoseptal left ventricular endocardium (BIS-LVe) and identify electrocardiographic characteristics to differentiate from inferobasal crux (IBC) VA. BACKGROUND: The inferior basal septum is an uncommon source of idiopathic VAs, which can arise from its endocardial or epicardial (crux) aspect. Because the latter are often targeted from the coronary venous system or epicardium, distinguishing between the 2 is important for successful ablation. METHODS: Consecutive patients undergoing ablation of idiopathic VA from the BIS-LVe or IBC from 2009 to 2018 were identified and clinical characteristics and electrocardiographs of VA were compared. RESULTS: Of 931 patients undergoing idiopathic VA ablation, Virginia was eliminated from the BIS-LVe in 19 patients (2%) (17 male, age 63.7 ± 9.2 years, LV ejection fraction: 45.0 ± 9.3%). QRS complexes typically manifested right bundle branch block morphology with "reverse V2 pattern break" and left superior axis (more negative in lead III than II). VA elimination was achieved after median of 2 lesions (interquartile range [IQR]: 1-6; range 1 to 20) (radiofrequency ablation time: 123 s [IQR: 75-311]). Compared with 7 patients with IBC VA (3 male, age 51.9 ± 20.1 years, LV ejection fraction: 51.4 ± 17.7%), BIS-LVe VA less frequently had initial negative forces (QS pattern) in leads II, III, and/or aVF (p < 0.001), R-S ratio <1 in lead V1 (p = 0.005), and notching in lead II (p = 0.006) were narrower (QRS duration: 178.2 ± 22.4 vs. 221.1 ± 41.9 ms; p = 0.04) and more frequently had maximum deflection index of <0.55 (p < 0.001). CONCLUSIONS: The BIS-LVe region is an uncommon source of idiopathic VA. Distinguishing these from IBC VA is important for procedural planning and ablation success.

Clinical and electrophysiological characteristics of idiopathic ventricular arrhythmias originating from the slow pathway region.

BACKGROUND: The slow pathway region (SPR) is commonly targeted during ablation of atrioventricular nodal reentrant tachycardia. However, its role in idiopathic ventricular arrhythmias (IVAs) remains unknown. OBJECTIVE: The purpose of this study was to describe the electrocardiographic and electrophysiological characteristics of IVAs that were successfully ablated from the SPR. METHODS: Medical records of consecutive patients undergoing ablation of IVAs in the para-Hisian region between 2010 and 2018 were reviewed to identify subjects whose ventricular arrhythmias were targeted from the SPR. RESULTS: Among 63 patients with para-Hisian IVAs undergoing ablation, the SPR was targeted in 12 (20%; mean age 64 ± 7 years; 9 men). All patients presented with ventricular premature depolarizations manifesting left bundle branch block morphology with variable precordial transition (leads V2-V5) and a mean QRS duration of 131 ± 11 ms. In all cases, leads I and aVL had positive forces (R or Rs) and lead aVR had negative forces (QS or Qr). In the majority of cases, lead II had positive forces (R or Rs; n = 9 [75%]) and lead III had negative forces (rS or QS; n = 9 [75%]). Mean activation at the SPR was 31 ± 5 ms pre-QRS. All patients had initial ablation with radiofrequency, resulting in junctional rhythm in 9 (75%); 3 (25%) patients required additional cryoablation. Ablation was successful in 11 patients (92%). One patient required a permanent pacemaker for heart block but subsequently recovered intrinsic conduction. CONCLUSION: The SPR can be a source of IVAs, which can be safely and successfully ablated in most cases using radiofrequency energy. IVAs arising from this location manifest unique electrocardiographic features.

Septal Coronary Venous Mapping to Guide Substrate Characterization and Ablation of Intramural Septal Ventricular Arrhythmia.

OBJECTIVES: This study describes the use of septal coronary venous mapping to facilitate substrate characterization and ablation of intramural septal ventricular arrhythmia (VA). BACKGROUND: Intramural septal VA represents a challenge for substrate definition and catheter ablation. METHODS: Between 2015 and 2018, 12 patients with structural heart disease, recurrent VA, and suspected intramural septal substrate underwent a septal coronary venous procedure in which mapping was performed by advancement of a wire into the septal perforator branches of the anterior interventricular vein. A total of 5 patients with idiopathic VA were also included as control subjects to compare substrate characteristics. RESULTS: Patients were 63 ± 14 years of age, and 11 (92%) were men. Most patients with structural heart disease had nonischemic cardiomyopathy (83%). Six patients underwent ablation for premature ventricular contractions (PVC) and 6 for ventricular tachycardia. All patients had larger septal unipolar voltage abnormalities than bipolar voltage abnormalities (mean area 35.3 ± 16.8 cm2 vs. 10.7 ± 8.4 cm2, respectively; p = 0.01), Patients with idiopathic VA had normal voltage. Septal coronary venous mapping revealed low-voltage, fractionated, and multicomponent electrograms in sinus rhythm in all patients with substrate compared to that in patients with idiopathic VA (amplitude 0.9 ± 0.9 mV vs. 4.4 ± 3.7 mV, respectively; p = 0.007; and duration 147 ± 48 ms vs. 92 ± 10 ms, respectively; p = 0.03). Ablation targeted early activation, pace map match, and/or good entrainment sites from intraseptal recording. Over a mean follow-up of 339 ± 240 days, the PVC and insertable cardioverter-defibrillator therapies burden were significantly reduced (from a mean of 22 ± 11% to 4 ± 8%; p = 0.005; and a mean 5 ± 2 to 1 ± 1; p = 0.001, respectively). Most patients (80%) with idiopathic VA remained arrhythmia free. CONCLUSIONS: In patients with suspected intramural septal VA, mapping of the septal coronary veins may be helpful to characterize the arrhythmia substrate, identify ablation targets, and guide endocardial ablation.

Electrophysiologic Substrate, Safety, Procedural Approaches, and Outcomes of Catheter Ablation for Ventricular Tachycardia in Patients After Aortic Valve Replacement.

OBJECTIVES: This study sought to investigate the substrate, procedural strategies, safety, and outcomes of catheter ablation (CA) for ventricular tachycardia (VT) in patients with aortic valve replacement (AVR). BACKGROUND: VT ablation in patients with AVR is challenging, particularly when mapping and ablation in the periaortic region are necessary. METHODS: We identified consecutive patients with mechanical, bioprosthetic, and transcatheter AVR who underwent CA for VT refractory to antiarrhythmic drugs and analyzed VT substrate, approach to LV access, complications, and long-term outcomes. RESULTS: Overall, 29 patients (87% men, mean age 67.9 ± 9.8 years, left ventricular ejection fraction 39 ± 10%) with prior AVR (13 mechanical, 15 bioprosthetic, 1 transcatheter AVR) underwent 40 ablations from 2004 to 2016. Left-sided mapping/CA was performed in 27 patients (36 procedures). Access was retrograde aortic in 11 procedures (all bioprosthetic), transseptal in 24 (13 mechanical; 10 bioprosthetic; 1 transcatheter AVR), or transventricular septal in 1. Periaortic bipolar or unipolar scar was detected in all 24 patients in whom detailed periaortic mapping was performed. Clinical VT circuit(s) involved the periaortic region in 10 patients (34%), 2 (7%) had bundle branch re-entry VT, and 17 (59%) had substrate unrelated to AVR. There were 2 major complications (both related to vascular access). Only 2 patients (9.1%) had VT recurrence. Over median follow-up of 12.8 months, 11 patients died (none as a result of recurrent VT). CONCLUSIONS: Whereas most patients undergoing CA for VT after AVR had VT from substrate unrelated to AVR, periaortic scar is universally present and bundle branch re-entry can be the VT mechanism. CA can be safely performed with excellent long-term VT elimination.

Case report and systematic review of pulmonary embolism mimicking ST-elevation myocardial infarction.

BACKGROUND: To study trends in the clinical presentation, electrocardiograms, and diagnostic imaging in patients with pulmonary embolism presenting as ST segment elevation. METHODS: We performed a systematic literature search for all reported cases of pulmonary embolism mimicking ST-elevation myocardial infarction. Pre-specified data such as clinical presentation, electrocardiogram changes, transthoracic echocardiographic findings, cardiac biomarkers, diagnostic imaging, therapy, and outcomes were collected. RESULTS: We identified a total of 34 case reports. There were 23 males. Mean age of the population was 56.5 ± 15.5 years. Patients presented with dyspnea (76.4%), chest pain (63.6%), and tachycardia (71.4%). All patients presented with ST-elevations, with the most common location being in the anterior-septal distribution, lead V3 (74%), V2 (71%), V1 (62%) and V4 (47%). ST-segment elevations in the inferior distribution were present in lead II (12%), III (18%), and aVF (21%). Presentation was least likely in the lateral distribution. Troponin was elevated in 78.9% of cases. Right ventricular strain was the most common echocardiographic finding. Over 80% of patients had findings consistent with elevated right ventricular pressure, with 50% reported RV dilatation and 20% RV hypokinesis. The most commonly used imaging modality was contrast-enhanced pulmonary angiography. There was a greater incidence of bilateral compared to unilateral pulmonary emboli (72.4% vs. 10%). About 65% patients received anticoagulation and 36.3% were treated with thrombolytics. Forty-six percent of patients required intensive care and 18.7% intubation. Overall mortality was 25.8%. CONCLUSIONS: A review of the literature reveals that in patients presenting with pulmonary embolism, electrocardiogram findings of ST-segment elevations will occur predominantly in the anterior-septal distribution.

Catheter ablation versus conventional treatment of atrial fibrillation in patients with heart failure with reduced ejection fraction: a systematic review and meta-analysis of randomized controlled trials.

PURPOSE: To evaluate whether catheter ablation is superior to conventional therapy for atrial fibrillation (AF) in patients with heart failure with reduced ejection fraction (HFrEF). METHODS: Electronic databases were searched for randomized, controlled trials of AF ablation compared with conventional therapy in adults with AF and HFrEF. Odds ratio (OR), standard mean difference (SMD), and 95% confidence intervals (CIs) were measured using the Mantel-Haenszel method. RESULTS: There were seven trials including 856 patients (mean age 62 years, male 86%). All-cause mortality in patients who underwent ablation was 10% vs. 19% in those who received conventional treatment (four trials, 668 patients, 47% relative reduction, 9% absolute reduction; OR 0.46, 95% CI 0.29-0.72). Improvement in the left ventricular ejection fraction was significantly higher for patients undergoing ablation (+ 9 ± 10%) compared to conventional treatment (+ 2 ± 7%) (seven trials, 856 patients, SMD 0.68, 95% CI 0.28-1.08). Freedom from AF was higher in patients undergoing ablation (seven trials, 856 patients, 70% vs. 18%, respectively; 64% relative reduction, 52% absolute reduction; OR 0.03 95% CI 0.01-0.11). There was no significant difference in major complications between both strategies (OR 1.13, 95% CI 0.58-2.20). CONCLUSIONS: Catheter ablation for AF in patients with HFrEF decreases mortality and AF recurrence and improves left ventricular function, functional capacity, and quality of life, when compared to conventional management, without increasing complications.

Bailout Atrial Balloon Septoplasty to Overcome Challenging Left Atrial Transseptal Access for Catheter Ablation of Atrial Fibrillation.

OBJECTIVES: This study reports outcomes of bailout atrial balloon septoplasty (ABS) to overcome challenging left atrial (LA) access in patients undergoing atrial fibrillation (AF) ablation. BACKGROUND: Transseptal puncture (TSP) and LA access for AF ablation can be challenging in patients with prior atrial septal surgery, percutaneous closure, or scarred septum due to multiple prior TSPs. METHODS: The study identified patients who underwent AF ablation at 2 ablation centers from 2011 to 2017 with challenging TSP in whom bailout percutaneous ABS was performed to allow LA access. Following TSP, the transseptal sheath could not be advanced to the LA despite multiple attempts or approaches including use of a stiff wire sequentially in the left and right pulmonary veins, use of a stiff pigtail exchange wire advanced in the LA or left ventricle, or sequential dilation with progressively larger diameter long dilators. ABS was performed using a noncompliant balloon (diameter 4 to 10 mm) advanced over a stiff wire deployed in the left superior pulmonary vein, allowing passage of the transseptal sheaths for completion of the AF ablation procedure. RESULTS: Fifteen patients (mean age 54.4 ± 15.5 years, 9 women) with challenging TSP (7 patients with prior surgical ASD repair, 2 with percutaneous ASD closure devices, and 13 with ≥1 previous TSP) underwent bailout ABS for AF ablation. After TSP (radiofrequency assisted in 10 cases), ABS was successful and permitted access to the LA for ablation in all patients. Mean time required to perform ABS was 21.3 ± 19.4 min, and mean total procedure time was 241.1 ± 114.6 min (fluoroscopy time 62.0 ± 29.9 min). There were no procedural complications. CONCLUSIONS: In patients undergoing AF ablation with difficult transseptal access due to scarred, surgically, or percutaneously repaired atrial septum, ABS is a safe and effective bailout strategy to obtain transseptal access.