Practicality and Safety of Electrical Pulmonary Vein Isolation and Left Atrial Appendage Ligation in Lung Transplant Recipients With Pretransplant Atrial Fibrillation.

Background: Lung transplant surgery creates surgical pulmonary vein isolation (PVI) as a routine part of the procedure. However, many patients with pretransplant atrial fibrillation continue to have atrial fibrillation at 1 y. We hypothesized that the addition of electrical PVI and left atrial appendage isolation/ligation (LAL) to the lung transplant procedure restores sinus rhythm at 1 y in patients with pretransplant atrial fibrillation. Methods: We retrospectively reviewed all adult lung transplant recipients at the University of California Los Angeles from April 2006 to August 2021. All patients with pretransplant atrial fibrillation underwent concomitant PVI/LAL and were compared with lung transplant recipients without preoperative atrial fibrillation. In-hospital outcomes; 1-y survival; and the incidence of stroke, cardiac readmissions, repeat ablations, and sinus rhythm (composite endpoint) were examined at 1 y for the PVI/LAL cohort. Results: Sixty-one lung transplant recipients with pretransplant atrial fibrillation underwent concomitant PVI/LAL. No patient in the PVI/LAL cohort required cardiac-related readmission or catheter ablation for atrial fibrillation within 1 y of transplantation. Freedom from the composite endpoint of death, stroke, cardiac readmission, and repeat ablation for atrial fibrillation at 1 y was 85% (95% confidence interval, 73%-92%) for lung transplant recipients treated with PVI/LAL. Conclusions: The addition of PVI/LAI to the lung transplant operation in patients with pretransplant atrial fibrillation was safe and effective in maintaining sinus rhythm and baseline risk of stroke at 1 y.

Cryothermal energy demonstrates shorter ablation time and lower complication rates compared with radiofrequency in surgical hybrid ablation for recurrent ventricular tachycardia.

BACKGROUND: Recurrent ventricular tachycardia (VT) after prior endocardial catheter ablation(s) presents challenges in the setting of prior cardiac surgery where percutaneous epicardial access may not be feasible. OBJECTIVE: The purpose of this study was to compare the outcomes of cryothermal vs radiofrequency ablation in direct surgical epicardial access procedures. METHODS: We performed a retrospective study of consecutive surgical epicardial VT ablation cases. Surgical cases using cryothermal vs radiofrequency ablation were analyzed and outcomes were compared. RESULTS: Between 2009 and 2022, 43 patients underwent either a cryothermal (n = 17) or a radiofrequency (n = 26) hybrid epicardial ablation procedure with direct surgical access. Both groups were similarly matched for age, sex, etiology of VT, and comorbidities with a high burden of refractory VT despite previous endocardial and/or percutaneous epicardial ablation procedures. The surgical access site was lateral thoracotomy (76.5%) in the cryothermal ablation group compared with lateral thoracotomy (42.3%) and subxiphoid approach (38.5%) in the radiofrequency group, with the remainder in both groups performed via median sternotomy. The ablation time was significantly shorter in those undergoing cryothermal ablation vs radiofrequency ablation (11.54 ± 15.5 minutes vs 48.48 ± 23.6 minutes; P < .001). There were no complications in the cryothermal ablation group compared with 6 patients with complications in the radiofrequency group. Recurrent VT episodes and all-cause mortality were similar in both groups. CONCLUSION: Hybrid surgical VT ablation with cryothermal or radiofrequency energy demonstrated similar efficacy outcomes. Cryothermal ablation was more efficient and safer than radiofrequency in a surgical setting and should be considered when surgical access is required.

Pulmonary vein and left atrial posterior wall isolation for the treatment of atrial fibrillation: Comparable outcomes for adults with congenital heart disease.

INTRODUCTION: Optimal treatment strategies for ACHD with AF are unknown. This study sought to assess outcomes of pulmonary vein isolation (PVI) ± left atrial (LA), posterior wall isolation (PWI) for adults with congenital heart disease (ACHD), and atrial fibrillation (AF). METHODS: A retrospective review of all cryoballoon (CB) PVI ± PWI procedures at a single center over a 3-year period were performed. Clinical characteristics and outcomes for patients with and without ACHD were compared. The primary outcome was the occurrence of atrial tachyarrhythmia at 12-months postablation after a 90-day blanking period. RESULTS: Three-hundred and sixteen patients (mean: 63 ± 12 years, [63% male]) underwent CB PVI ± PWI during the study, including 31 (10%) ACHD (simple 35%, moderate 39% complex 26%; nonparoxysmal AF in 52%). ACHD was younger (51 vs. 64 years; p < .001) with a lower CHADS2 DS2 -VASc score (1.2 vs. 2.1; p = .001) but had a greater LA diameter (4.9 vs. 4.0 cm; p < .001) and a number of prior cardioversions (0.9 vs. 0.4; p < .001) versus controls. 12-month freedom from recurrent AF was similar for ACHD and controls (76% vs. 80%; p = .6) and remained nonsignificant in multivariate analysis (hazard ratio: 1.8, 95% confidence interval: 0.7-5.1; p = .22). At 12-months postablation, 75% of ACHD versus 93% of control patients were off antiarrhythmic drug therapy (p = .07). CONCLUSION: This study demonstrates younger age and lower conventional stroke risk, yet clinically advanced AF for ACHD relative to controls. CB PVI ± PWI was an effective strategy for the treatment of AF among all forms of ACHD with similar 12-month outcomes as compared to controls.

Left atrial posterior wall isolation in conjunction with pulmonary vein isolation using cryoballoon for treatment of persistent atrial fibrillation (PIVoTAL): study rationale and design.

BACKGROUND: There is growing evidence in support of pulmonary vein isolation (PVI) with concomitant posterior wall isolation (PWI) for the treatment of patients with symptomatic persistent atrial fibrillation (persAF). However, there is limited data on the safety and efficacy of this approach using the cryoballoon. OBJECTIVE: The aim of this multicenter, investigational device exemption trial (G190171) is to prospectively evaluate the acute and long-term outcomes of PVI versus PVI+PWI using the cryoballoon in patients with symptomatic persAF. METHODS: The PIVoTAL is a prospective, randomized controlled study ( ClinicalTrials.gov : NCT04505163) in which patients with symptomatic persAF refractory/intolerant to ≥ 1 class I-IV antiarrhythmic drug, undergoing first-time catheter ablation, will be randomized to PVI (n = 183) versus PVI+PWI (n = 183) using the cryoballoon in a 1:1 fashion. The design will be double-blind until randomization immediately after PVI, beyond which the design will transform into a single-blind. PVI using cryoballoon will be standardized using a pre-specified dosing algorithm. Other empiric ablations aside from documented arrhythmias/arrhythmias spontaneously induced during the procedure will not be permitted. The primary efficacy endpoint is defined as AF recurrence at 12 months, after a single procedure and a 90-day blanking period. Arrhythmia outcomes will be assessed by routine electrocardiograms and 7-14 day ambulatory electrocardiographic monitoring at 3, 6, and 12 months post-ablation. CONCLUSION: The PIVoTAL is a prospective, randomized controlled trial designed to evaluate the outcomes of PVI alone versus PVI+PWI using the cryoballoon, in patients with symptomatic persAF. We hypothesize that PVI+PWI will prove to be superior to PVI alone for prevention of AF recurrence.

Non-invasive stereotactic body radiation therapy for refractory ventricular arrhythmias: an institutional experience.

BACKGROUND: Initial studies have reported excellent safety and efficacy for stereotactic body radiation therapy (SBRT) in patients with refractory ventricular tachycardia (VT). METHODS: This is a single-center retrospective analysis of eight consecutive patients who underwent SBRT for refractory, scar-related VT. The anatomic target for radioablation was defined based on surface 12-lead ECG VT morphology, cardiac magnetic resonance imaging, and electroanatomic mapping data when available. The target volume treated and the prescribed radiation dose (15-25 Gy) was based on the combined clinical assessment of the cardiac electrophysiologist and radiation oncologist. Ventricular arrhythmias, radiation-related outcomes, and adverse events were monitored at follow-up. RESULTS: Eight patients underwent nine SBRT sessions. All patients were male with an average age of 75 ± 7.3 years and mean ejection fraction of 21 ± 7%. SBRT was performed with delivery of an average of 22.2 ± 3.6 Gy in a single session with a procedure time of 18.2 ± 6.0 min. All but one session was performed on an inpatient basis. No acute complications occurred. During a median follow-up of 7.8 months (IQR 4.8, 9.9), ICD therapies decreased from median 69.5 (43.5, 115.8) pre-SBRT to 13.3 (IQR 7.7, 35.8) post-SBRT (p = 0.036). There were three patient deaths in the follow-up period, unrelated to SBRT. Apparent clinical benefit occurred 33% of the time after SBRT. CONCLUSIONS: The patients experienced overall reduction in VT burden following SBRT, though not with the immediate effect seen in other patient series. Further studies (basic, translational, and clinical) are essential to determine the benefit of SBRT and if so, the optimal protocols and patient selection.

Hybrid surgical vs percutaneous access epicardial ventricular tachycardia ablation.

BACKGROUND: There is limited experience of surgical epicardial access in the contemporary era of ventricular tachycardia ablation after cardiac surgery. OBJECTIVES: The purpose of this study was to describe our institutional experience with surgical epicardial access and the influence of surgical approach and compare outcomes with those of a propensity-matched percutaneous epicardial access control group. METHODS: We performed a retrospective study of consecutive surgical epicardial ventricular tachycardia (VT) ablation cases from a single center. Surgical cases were propensity-matched to percutaneous epicardial ablation controls and short-term and long-term outcomes were compared. RESULTS: Between 2004 and 2016, 38 patients underwent 40 surgical epicardial access procedures (subxiphoid, n = 22; thoracotomy, n = 18). The commonest indication was prior coronary artery bypass grafting (45%), valve surgery (22%), or ventricular assist device (VAD) (10%). The mean procedure time was 444 minutes (standard deviation, 107 minutes). Mapped epicardial geometry area was 149 cm2 (interquartile range 182 cm2), which comprised 36% of the mapped epicardial geometric area of a percutaneous control group. Subxiphoid access gave preferential access to the inferior and inferolateral left ventricular segments and was less frequently able to access the anterior, anterolateral, and apical segments compared with a thoracotomy approach. When compared with results from a propensity-matched percutaneous-access group, short-term outcomes, complication rates, and 1-year survival free from a combined end point of VT recurrence, death, or transplantation were not statistically different. CONCLUSIONS: Surgical epicardial access after cardiac surgery for ablation of VT in patients with careful preprocedure evaluation can be performed with acceptable safety with no statistical difference in long-term outcomes compared with a propensity-matched percutaneous epicardial cohort. The region of left ventricular epicardium that can be mapped is limited compared with that of percutaneous cases and is determined by the surgical approach.

Incidence and significance of adhesions encountered during epicardial mapping and ablation of ventricular tachycardia in patients with no history of prior cardiac surgery or pericarditis.

BACKGROUND: Pericardial adhesions can prevent epicardial access and restrict catheter movement during mapping and ablation of ventricular tachycardia (VT). The incidence of adhesions in patients without prior cardiac surgery or clinically evident pericarditis is not known. OBJECTIVE: To describe the incidence of pericardial adhesions and explore their impact in patients without prior cardiac surgery or pericarditis. METHODS: A retrospective search of our ablation database containing patients who underwent epicardial ablation for VT was undertaken. Adhesions were diagnosed with routine contrast pericardiography after pericardial entry. Demographics and long-term outcomes were compared between patients with and without adhesions. RESULTS: Between 2004 and 2016, successful epicardial entry was achieved in 188 of 192 attempts (98%). In 155 first-time epicardial access attempts, pericardial adhesions were diagnosed in 13 (8%). When comparing baseline demographics, there was no significant difference. However, adhesions tended to occur more frequently with severe renal impairment (2% of patients without adhesions vs 15% of patients with adhesions, P = .07). No patient with a structurally normal heart had adhesions present. Adhesions were associated with limited epicardial mapping (3% of patients without adhesions vs 85% of patients with adhesions, P < .001) and lower short-term procedural success (68% of patients without adhesions vs 46% of patients with adhesions, P = .02), but complication rates were similar. The presence of adhesions did not translate into lower VT-free survival (P = .64) or freedom from a combined end point of VT recurrence, death, or transplant at 1 year (P = .93). CONCLUSION: Adhesions may be unexpectedly encountered in patients without prior cardiac surgery or pericarditis. When present, they can limit mapping and may be associated with lower short-term success. Larger studies are required to determine their impact on long-term outcomes.

Atrioesophageal Fistula After Atrial Fibrillation Ablation: A single center series.

BACKGROUND: The incidence of atrioesophageal fistula (AEF) after atrial fibrillation catheter ablation is reported to be 0.015%-0.04%, though it is likely underreported due to a number of factors including misdiagnosis. We report our institutional experience with AEF. METHODS: Patients with confirmed diagnosis of AEF between 2004 and 2016 at our institution were identified (n=5) and their clinical characteristics and outcome were analyzed. RESULTS: AEF occurred in 5 patients who underwent AF catheter ablation (3 ablated at our institution; 2 transferred from outside hospitals after diagnosis of AEF). Symptoms were chest pain (n=3), fever (n=3), TIA/stroke (n=3), dysphagia (n=1), and headache (n=1). Chest pain was the earliest symptom and occurred 21-24 days post-RFA. One patient had sudden death without preceding symptoms. Findings included leukocytosis (WBC count range of 17200-19,000) and sepsis. Chest CT was obtained in 3 patients and showed air in the left atrium or mediastinum. Three patients had evidence of multifocal stroke on MRI. Three patients died before surgery could be performed. Two patients (40%) underwent emergent surgery which included partial excision of atrial wall, closure with bovine pericardial patch and closure of esophageal lesion. Surgical outcomes were favorable (100% survival). CONCLUSION: Chest pain and fever were the early symptoms of AEF and occurred before the neurologic complications. Chest CT was an excellent tool for detection of AEF. All patients who were diagnosed correctly and underwent surgery survived. Early detection is imperative as prompt surgery may improve survival. Health-care community education is the key to ensure early detection and transfer to a qualified surgical center.

Predicting postoperative atrial fibrillation using CHA2DS2-VASc scores.

BACKGROUND: Postoperative atrial fibrillation (POAF) is the most frequent complication of cardiac surgery and is associated with increased morbidity and mortality. Pharmacologic prophylaxis is the main method of preventing POAF but needs to be targeted to patients at high risk of developing POAF. The CHA2DS2-VASc scoring system is a clinical guideline for assessing ischemic stroke risk in patients with atrial fibrillation. The present study evaluated the utility of this scoring system in predicting the risk of developing de novo POAF in cardiac surgery patients. MATERIALS AND METHODS: A total of 2385 patients undergoing cardiac surgery at our institution from 2008-2014 were identified for analysis. Each patient was assigned a CHA2DS2-VASc score and placed into a low- (score of 0), intermediate- (1), or high-risk (≥2) group. A multivariate regression model was created to control for known risk factors of atrial fibrillation. RESULTS: POAF occurred in 380 of 2385 patients (15.9%). Mean CHA2DS2-VASc scores among patients with POAF and without POAF were 3.6 ± 1.7 and 2.8 ± 1.7, respectively (P < 0.0001). Using multivariate analysis, as a patient's CHA2DS2-VASc score rose from 0-9, the risk of developing POAF increased from 8.2%-42.3%. Each point increase was associated with higher odds of developing POAF (adjusted odds ratio, 1.27; 95% confidence interval, 1.18-1.36, P < 0.0001). Compared with low-risk patients, patients in the high-risk group were 5.21 times more likely to develop POAF (P < 0.0001). CONCLUSIONS: The CHA2DS2-VASc algorithm is a simple risk-stratification tool that could be used to direct pharmacologic prophylaxis toward patients most likely to experience POAF.

Catheter ablation of scar-based ventricular tachycardia: Relationship of procedure duration to outcomes and hospital mortality.

BACKGROUND: Ablation has become an important option for treatment of ventricular tachycardia (VT). The influence of procedure duration on outcomes remains unexamined. OBJECTIVE: The purpose of this study was to determine the influence of procedure duration on outcomes and complications over an 8-year period METHODS: Patients referred for scar-mediated VT ablation from 2004 to 2011 were retrospectively analyzed. Procedure duration was defined as the time from the insertion of catheters through the femoral vein to the time of their withdrawal. Procedure duration was analyzed in relationship with baseline and intraoperative covariates, acute procedural outcomes, complications, and 6-month clinical outcomes. RESULTS: One hundred forty-eight patients underwent VT ablation with mean procedure duration of 5.7 ± 1.8 hours. VT recurrence and survival at 6 months were 46% and 82%, respectively, and were not associated with procedure duration. Hospital mortality increased with intraoperative intraaortic balloon pump insertion (adjusted odds ratio [OR] 13.7, 95% confidence interval [CI] 2.35-79.94, P = .004) and was improved with successful ablation of the clinical VT as a procedural end-point (adjusted OR 0.13, 95% Cl 0.03-0.54, P = .005). The association between procedure duration and hospital mortality remained after adjusting for significant baseline variables (adjusted OR 1.75, 95% CI 1.14-2.68, P = .0098) and intraoperative variables (adjusted OR 1.6, 95% CI 1.12-2.29, P = .0104). CONCLUSION: Hospital mortality was significantly increased by unsuccessful clinical VT ablation as a procedural end-point and intraoperative intraaortic balloon pump insertion. However, after adjusting for significant baseline and intraoperative covariates, procedure duration still was associated with increased hospital mortality. Procedure duration had no impact on VT recurrence and survival at 6 months.

Do preoperative ß-blockers improve postoperative outcomes in patients undergoing cardiac surgery? Challenging societal guidelines.

Preoperative ß-blockers (BBs) are widely administered to reduce morbidity and mortality among surgical patients. In fact, the Society of Thoracic Surgeons uses the administration of preoperative BBs as a quality metric. Recent reports, however, have questioned the benefit and safety of preoperative BB administration. The aim of our study was to investigate whether preoperative BBs lead to improved surgical outcomes in patients undergoing cardiac surgery. A review of our prospectively maintained institutional database was done to identify adults undergoing cardiac operations at our institution from 2008 to 2013. Survival to discharge was the primary outcome with several additional secondary measures of morbidity included. A total of 2120 patients were included in the analysis and a multivariate logistic regression model was developed to adjust for differences between patient groups. After adjustment, BB administration was associated with lower odds of both prolonged ventilation (odds ratio [OR], 0.73; P = 0.032) and prolonged length of stay (OR, 0.79; P = 0.044). BB use was not associated with significant differences in other outcomes such as mortality or postoperative atrial fibrillation. Our study found that preoperative BBs may not be associated with sufficiently improved outcomes to justify their use as a quality metric in this population. Thus, prospective studies are warranted.

CHADS2 score predicts atrial fibrillation following cardiac surgery.

BACKGROUND: Atrial fibrillation (AF) following cardiac surgery portends higher morbidity and increased health expenditure. Although many anatomic and patient risk factors have been identified, a simple clinical scoring system to identify high-risk patients is lacking. The CHADS2 score is widely used to predict the risk of stroke in patients with AF. We assessed the utility of this scoring algorithm in predicting the development of de novo postoperative atrial fibrillation (POAF) in cardiac surgery patients. MATERIAL AND METHODS: A total of 2120 patients from 2008 to 2013 were identified for inclusion in our analysis. CHADS2 scores were calculated, and patients grouped into low- (0), intermediate- (1) and high-risk (≥2) categories. A multivariate regression model was developed to account for known risk factors of AF. RESULTS: Of the 2120 patients, 344 (16.2%) patients developed de novo POAF during their primary hospitalization. Mean CHADS2 scores for POAF patients and no POAF patients were 2.1 ± 1.2 and 1.7 ± 1.3 (P < 0.0001), respectively. CHADS2 score was a significant predictor of AF on multivariate regression analysis (adjusted odds ratio, 1.26; 95% confidence interval, 1.14-1.40). As CHADS2 score increased from 0 to 6, the probability of POAF increased from 11.1% to 32.7% (P < 0.0001). Compared with the low-risk group, the intermediate-risk and high-risk groups had a 1.73- and 2.58-fold increase in odds of developing POAF, respectively (P < 0.02 and P < 0.0001). CONCLUSIONS: CHADS2 score is a powerful and convenient predictor of developing POAF. We recommend its utilization in identifying high-risk patients that may benefit from pharmacologic prophylaxis.

Unipolar and bipolar electrogram characteristics predict exit block during pulmonary vein antral isolation.

INTRODUCTION: The usefulness of unipolar electrograms (EGMs) has been reported in assessing lesion transmurality and conduction block along ablation lines. It is unknown whether unipolar and bipolar EGM characteristics predict exit block during pulmonary vein isolation (PVI) procedures. METHODS AND RESULTS: Twenty patients (63 ± 7 years; 14 males [70%]) undergoing PVI with a circular mapping catheter (CMC) placed outside each PV ostium were retrospectively studied. After entrance block was achieved, pacing at each bipole around the CMC was performed to assess for absence of atrial capture (exit block). Bipolar EGMs recorded before pacing were examined for voltage, duration, fractionation, and monophasic morphology. Unipolar EGMs were examined for positive and negative amplitude, PQ segment elevation, fractionation, and monophasic morphology. The association of these parameters with atrial capture (absence of exit block) at each site was analyzed. After achievement of entrance block, only 23 of 64 PV antra (36%) exhibited exit block. Unipolar EGMs at sites with persistent capture were more likely to be fractionated and had larger negative deflections. Bipolar EGMs at sites with persistent capture showed higher amplitude, longer duration, were more likely to be fractionated, and were less likely to be monophasic. In a multivariate logistic regression model, bipolar and unipolar fractionation, bipolar duration, and lack of bipolar monophasic morphology were independently associated with persistent atrial capture. CONCLUSION: Specific unipolar and bipolar EGM characteristics are associated with left atrium capture after PV antral isolation. These parameters might be useful in predicting the need for further ablation to achieve exit block.

Ultra high-density multipolar mapping with double ventricular access: a novel technique for ablation of ventricular tachycardia.

UNLABELLED: Ultra High-Density Multipolar Mapping With Double Ventricular Access. BACKGROUND: Analogous to the use of circular loop catheters to guide ablation around the pulmonary veins, it may be advantageous to use a multipolar catheter in the ventricle for rapid mapping and to guide ablation. We describe a technique using double access into the left ventricle for multipolar electroanatomic mapping and ablation of scar-mediated ventricular tachycardia (VT). METHODS: Double access into the left ventricle was obtained via transseptal technique. Endocardial mapping was performed via the first transseptal sheath using a steerable duodecapolar catheter. Higher density mapping was performed in areas of dense scar (<0.5 mV) and border zone (0.5-1.5 mV). All late potentials (LPs) observed on the 20 poles were tagged and pacemapping was performed at these sites for comparison with the clinical or induced VT 12-lead template. If VT was hemodynamically tolerated, entrainment mapping was attempted at sites demonstrating diastolic activity. Ablation was performed through the second transseptal sheath with an open-irrigated catheter at target sites identified by LPs, pacemapping, and/or entrainment on the duodecapolar catheter. RESULTS: Seventeen patients (88% ischemic cardiomyopathy) underwent electroanatomic mapping and ablation with double transseptal access. The mean number of endocardial mapping points was 819 ± 357 with an average mapping time of 31 ± 7 minutes. The mean number of VTs induced was 2.8 ± 1.6, mean cycle length 418 ms ± 101. LPs were seen in all patients during endocardial mapping with the duodecapolar catheter. Good (56%) and perfect (44%) pacemaps were seen in all patients when performed. Concealed entrainment, guided by the earliest diastolic activity seen on the duodecapolar catheter, was demonstrated in 4 patients (24%). Acute success was achieved in 94% of patients with complete success in 47% and partial success in 47%. The intermediate success rate (free of VT recurrence) was 69%, with an average follow-up of 8 ± 3 months. CONCLUSION: Mapping and ablation of scar-mediated VT using a multipolar catheter results in ultra high-density delineation of the left ventricular substrate. A novel double ventricular access strategy has the potential to facilitate identification of LPs, pacemapping, and entrainment mapping.

Characterization of the arrhythmogenic substrate in ischemic and nonischemic cardiomyopathy implications for catheter ablation of hemodynamically unstable ventricular tachycardia.

OBJECTIVES: The purpose of this study was to compare the characteristics and prevalence of late potentials (LP) in patients with nonischemic cardiomyopathy (NICM) and ischemic cardiomyopathy (ICM) etiologies and evaluate their value as targets for catheter ablation. BACKGROUND: LP are frequently found in post-myocardial infarction scars and are useful ablation targets. The relative prevalence and characteristics of LP in patients with NICM is not well understood. METHODS: Thirty-three patients with structural heart disease (NICM, n = 16; ICM, n = 17) referred for catheter ablation of ventricular tachycardia were studied. Electroanatomic mapping was performed endocardially (n = 33) and epicardially (n = 19). The LP were defined as low voltage electrograms (<1.5 mV) with onset after the QRS interval. Very late potentials (vLP) were defined as electrograms with onset >100 ms after the QRS. RESULTS: We sampled an average of 564 +/- 449 points and 726 +/- 483 points in the left ventricle endocardium and epicardium, respectively. Mean total low voltage area in patients with ICM was 101 +/- 55 cm(2) and 56 +/- 33 cm(2), endocardial and epicardial, respectively, compared with NICM of 55 +/- 41 cm(2) and 53 +/- 28 cm(2), respectively. Within the total low voltage area, vLP were observed more frequently in ICM than in NICM in endocardium (4.1% vs. 1.3%; p = 0.0003) and epicardium (4.3% vs. 2.1%, p = 0.035). An LP-targeted ablation strategy was effective in ICM patients (82% nonrecurrence at 12 +/- 10 months of follow-up), whereas NICM patients had less favorable outcomes (50% at 15 +/- 13 months of follow-up). CONCLUSIONS: The contribution of scar to the electrophysiological abnormalities targeted for ablation of unstable ventricular tachycardia differs between ICM and NICM. An approach incorporating LP ablation and pace-mapping had limited success in patients with NICM compared with ICM, and alternative ablation strategies should be considered.

Functional characterization of atrial electrograms in sinus rhythm delineates sites of parasympathetic innervation in patients with paroxysmal atrial fibrillation.

OBJECTIVES: This study sought to characterize left atrial (LA) sinus rhythm electrogram (EGM) patterns and their relationship to parasympathetic responses during atrial fibrillation (AF) ablation. BACKGROUND: The mechanistic basis of fractionated LA EGMs in patients with paroxysmal AF is not well understood. METHODS: We analyzed 1,662 LA ablation sites from 30 patients who underwent catheter ablation for paroxysmal AF. Pre-ablation EGM characteristics (number of deflections, amplitude, and duration) were measured in sinus rhythm. Parasympathetic responses during radiofrequency application (increase of atrial-His interval by > or =10 ms or decrease of sinus rate by > or =20%) were assessed at all sites. We also prospectively studied the effect of adenosine, a pharmacological agent mimicking acetylcholine signaling in myocytes, on LA EGMs. Finally, we performed mathematical simulations of atrial tissue to delineate possible mechanisms of fractionated EGMs in sinus rhythm. RESULTS: A specific pattern of pre-ablation sinus rhythm EGM (deflections > or =4, amplitude > or =0.7 mV, and duration > or =40 ms) was strongly associated with parasympathetic responses (sensitivity 72%, specificity 91%). The sites associated with these responses were found to be located mainly in the posterior wall of the LA. Adenosine administration and mathematical simulation of the effect of acetylcholine were able to reproduce a similar EGM pattern. CONCLUSIONS: Parasympathetic activation during AF ablation is associated with the presence of pre-ablation high-amplitude fractionated EGMs in sinus rhythm. Local acetylcholine release could potentially explain this phenomenon.