Pulmonary Vein Isolation With or Without Left Atrial Appendage Ligation in Atrial Fibrillation: The aMAZE Randomized Clinical Trial.

Importance: Left atrial appendage elimination may improve catheter ablation outcomes for atrial fibrillation. Objective: To assess the safety and effectiveness of percutaneous left atrial appendage ligation adjunctive to catheter pulmonary vein isolation for nonparoxysmal atrial fibrillation. Design, Setting, and Participants: This multicenter, prospective, open-label, randomized clinical trial evaluated the safety and effectiveness of percutaneous left atrial appendage ligation adjunctive to planned pulmonary vein isolation for nonparoxysmal atrial fibrillation present for less than 3 years. Eligible patients were randomized in a 2:1 ratio to undergo left atrial appendage ligation and pulmonary vein isolation or pulmonary vein isolation alone. Use of a 2:1 randomization ratio was intended to provide more device experience and safety data. Patients were enrolled from October 2015 to December 2019 at 53 US sites, with the final follow-up visit on April 21, 2021. Interventions: Left atrial appendage ligation plus pulmonary vein isolation compared with pulmonary vein isolation alone. Main Outcomes and Measures: A bayesian adaptive analysis was used for primary end points. Primary effectiveness was freedom from documented atrial arrythmias of greater than 30 seconds duration 12 months after undergoing pulmonary vein isolation. Rhythm was assessed by Holter monitoring at 6 and 12 months after pulmonary vein isolation, symptomatic event monitoring, or any electrocardiographic tracing obtained through 12 months after pulmonary vein isolation. Primary safety was a composite of predefined serious adverse events compared with a prespecified 10% performance goal 30 days after the procedure. Left atrial appendage closure was evaluated through 12 months after pulmonary vein isolation. Results: Overall, 404 patients were randomized to undergo left atrial appendage ligation plus pulmonary vein isolation and 206 were randomized to undergo pulmonary vein isolation alone. Primary effectiveness was 64.3% with left atrial appendage ligation and pulmonary vein isolation and 59.9% with pulmonary vein isolation only (difference, 4.3% [bayesian 95% credible interval, -4.2% to 13.2%]; posterior superiority probability, 0.835), which did not meet the statistical criterion to establish superiority (0.977). Primary safety was met, with a 30-day serious adverse event rate of 3.4% (bayesian 95% credible interval, 2.0% to 5.0%; posterior probability, 1.0) which was less than the prespecified threshold of 10%. At 12 months after pulmonary vein isolation, complete left atrial appendage closure (0 mm residual communication) was observed in 84% of patients and less than or equal to 5 mm residual communication was observed in 99% of patients. Conclusions and Relevance: Percutaneous left atrial appendage ligation adjunctive to pulmonary vein isolation did not meet prespecified efficacy criteria for freedom from atrial arrhythmias at 12 months compared with pulmonary vein isolation alone for patients with nonparoxysmal atrial fibrillation, but met prespecified safety criteria and demonstrated high rates of closure at 12 months. Trial Registration: ClinicalTrials.gov Identifier: NCT02513797.

Incidence, Risk Score Performance, and In-Hospital Outcomes of Postoperative Atrial Fibrillation After Cardiac Surgery.

BACKGROUND: Postoperative atrial fibrillation (POAF) frequently complicates cardiac surgery. Predicting POAF can guide interventions to prevent its onset. This study assessed the incidence, risk factors, and related adverse outcomes of POAF after cardiac surgery. METHODS: A cohort of 1,606 patients undergoing cardiac surgery at a tertiary referral center was analyzed. Postoperative AF was defined based on the Society of Thoracic Surgeons' criteria: AF/atrial flutter after operating room exit that either lasted longer than 1 hour or required medical or procedural intervention. Risk factors for POAF were evaluated, and the performance of established risk scores (POAF, HATCH, COM-AF, CHA2DS2-VASc, and Society of Thoracic Surgeons risk scores) in predicting POAF was assessed using discrimination (area under the receiver operator characteristics curve) analysis. The association of POAF with secondary outcomes, including length of hospital stay, ventilator time, and discharge to rehabilitation facilities, was evaluated using adjusted linear and logistic regression models. RESULTS: The incidence of POAF was 32.2% (n = 517). Patients who developed POAF were older, had traditional cardiovascular risk factors and higher Society of Thoracic Surgeons risk scores, and often underwent valve surgery. The POAF risk score demonstrated the highest area under the receiver operator characteristics curve (0.65), but risk scores generally underperformed. Postoperative AF was associated with extended hospital stays, longer ventilator use, and higher likelihood of discharge to rehabilitation facilities (odds ratio, 2.30; 95% CI, 1.73-3.08). CONCLUSION: This study observed a high incidence of POAF following cardiac surgery and its association with increased morbidity and resource utilization. Accurate POAF prediction remains elusive, emphasizing the need for better risk-prediction methods and tailored interventions to diminish the effect of POAF on patient outcomes.

Risk Stratification in Patients Who Underwent Percutaneous Left Atrial Appendage Occlusion.

Left atrial appendage occlusion (LAAO) is effective in preventing thromboembolism. Risk stratification tools could help identify patients at risk for early mortality after LAAO. In this study, we validated and recalibrated a clinical risk score (CRS) to predict risk of all-cause mortality after LAAO. This study used data from patients who underwent LAAO in a single-center, tertiary hospital. A previously developed CRS using 5 variables (age, body mass index [BMI], diabetes, heart failure, and estimated glomerular filtration rate) was applied to each patient to assess risk of all-cause mortality at 1 and 2 years. The CRS was recalibrated to the present study cohort and compared with established atrial fibrillation-specific (CHA2DS2-VASc and HAS-BLED) and generalized (Walter index) risk scores. Cox proportional hazard models were used to assess the risk of mortality and discrimination was assessed by Harrel C-index. Among 223 patients, the 1- and 2-year mortality rates were 6.7% and 11.2%, respectively. With the original CRS, only low BMI (<23 kg/m2) was a significant predictor of all-cause mortality (hazard ratio [HR] [95% CI] 2.76 [1.03 to 7.35]; p = 0.04). With recalibration, BMI <29 kg/m2 and estimated glomerular filtration rate <60 ml/min/1.73 m2 were significantly associated with an increased risk of death (HR [95% CI] 3.24 [1.29 to 8.13] and 2.48 [1.07 to 5.74], respectively), with a trend toward significance noted for history of heart failure (HR [95% CI] 2.13 [0.97 to 4.67], p = 0.06). Recalibration improved the discriminative ability of the CRS from 0.65 to 0.70 and significantly outperformed established risk scores (CHA2DS2-VASc = 0.58, HAS-BLED = 0.55, Walter index = 0.62). In this single-center, observational study, the recalibrated CRS accurately risk stratified patients who underwent LAAO and significantly outperformed established atrial fibrillation-specific and generalized risk scores. In conclusion, clinical risk scores should be considered as an adjunct to standard of care when evaluating a patient's candidacy for LAAO.

Detection of atrial fibrillation in real world setting in patients with cryptogenic stroke and an implantable loop recorder.

INTRODUCTION: Implantable loop recorders (ILR) are used to screen for atrial fibrillation (AF) in patients with cryptogenic stroke (CS). However, there is limited real-world data regarding the long-term rate of AF detection using ILR and management consequences in patients with CS. The objective is to assess the rate of AF detection in patients with CS in a real-world study over 36 months of follow-up and its consequences on stroke prevention. METHODS: This retrospective study included patients with an ILR placed for CS at Baylor College of Medicine and Baylor St. Luke's Medical Center between January 2014 and July 2021. The primary outcome was AF detection in patients with ILR. The secondary outcome was the rate of subsequent strokes after ILR placement in patients with or without diagnosed AF. The AF detection rate in our cohort was compared to the rate in CRYSTAL-AF Trial at 36-month follow-up. The impact of AF detection on clinical management was examined. RESULTS: We identified 225 patients. 51.1% were women and 38.2% African American. Among 85 patients with ILR labeled AF, 43 patients had true AF, and 42 had incorrectly labeled AF (48.3% false positive). The estimated AF detection rate at 36 months follow-up was 28.6% (95% CI, 26.6%-30.6%). 58.1% of patients with AF were initiated on oral anticoagulation, 80.0% of whom were started on a direct oral anticoagulant. 13.8% of patients had recurrent strokes after ILR implantation; 4 of whom were diagnosed with AF. CONCLUSION: Compared to CRYSTAL-AF, the AF detection rate in our cohort is similar, but this cohort includes a higher proportion of female and African American patients. Most patients with recurrent strokes after ILR implant did not have AF during 36 months of monitoring.

Contact-force recovery predicts the absence of cardiac perforation during steam pops.

PURPOSE: Cardiac perforation (CP) is an uncommon but clinically important complication of radiofrequency ablation (RFA). We previously showed that contact-force recovery after a steam pop predicts the absence of CP in an open-chest animal model after pericardial dissection. We attempted to determine whether this also applies when pericardium is present. METHODS: In 5 open-chest sheep, left atrial RFA was performed under direct observation with a 7.5F ThermoCool SmartTouch force-sensing catheter (Biosense Webster Inc., Irvine, CA, USA). The catheter's contact force was measured every 50 ms during RFA. After each steam pop, the presence (+) or absence (-) of CP was noted, as well as whether pericardium was present over the ablation site. Contact-force signals were analyzed to detect contact-force recovery. Perforation rates were compared between sites with or without pericardium. RESULTS: Ninety-six steam pops occurred: 77 with pericardium and 19 without. For the pericardial steam pops, contact-force recovery occurred in 31/60 CP- events (52%) and 1/17 CP+ events (6%; P = 0.0006). For nonpericardial steam pops, contact-force recovery occurred in 4/9 CP- events (44%) and 1/10 CP+ events (P = 0.14). The rate of CP was 22% with pericardium and 52% without (P = 0.02). Pericardial tissue charred extensively during steam pop induction, even in the absence of CP. CONCLUSIONS: Contact-force recovery predicts the absence of CP during RFA independently of whether the pericardium is present. The presence of the pericardium may decrease the likelihood of perforation, perhaps by acting as a thermal sink. Additional studies are needed to correlate these results with clinical experience.

Slow-pathway visualization by using voltage-time relationship: A novel technique for identification and fluoroless ablation of atrioventricular nodal reentrant tachycardia.

BACKGROUND: Atrioventricular nodal reentrant tachycardia (AVNRT) is treatable by catheter ablation. Advances in mapping-system technology permit fluoroless workflow during ablations. As national practice trends toward fluoroless approaches, easily obtained, reproducible methods of slow-pathway identification, and ablation become increasingly important. We present a novel method of slow-pathway identification and initial ablation results from this method. METHODS AND RESULTS: We examined AVNRT ablations performed at our institution over a 12-month period. In these cases, the site of the slow pathway was predicted by latest activation in the inferior triangle of Koch during sinus rhythm. Ablation was performed in this region. Proximity of the predicted site to the successful ablation location, complication rates, and patient outcomes were recorded. Junctional rhythm was seen in 40/41 ablations (98%) at the predicted site (mean, 1.3 lesions and median, 1 lesion per case). One lesion was defined as 5 mm of ablation. The initial ablation was successful in 39/41 cases (95%); in two cases, greater or equal to 2 echo beats were detected after the initial ablation, necessitating further lesion expansion. In 8/41 cases (20%), greater than one lesion was placed during initial ablation before attempted reinduction. Complications included one transient heart block and one transient PR prolongation. During follow-up (median, day 51), one patient had lower-extremity deep-vein thrombosis and pulmonary embolus, and one had a lower-extremity superficial venous thrombosis. There was one tachycardia recurrence, which prompted a redo ablation. CONCLUSIONS: Mapping-system detection of late-activation, low-amplitude voltage during sinus rhythm provides an objective, and fluoroless means of identifying the slow pathway in typical AVNRT.

Confirming pericardial access by using impedance measurements from a micropuncture needle.

BACKGROUND: Pericardial access is complicated by two difficulties: confirming when the needle tip is in the pericardial space, and avoiding complications during access, such as inadvertently puncturing other organs. Conventional imaging tools are inadequate for addressing these difficulties, as they lack soft-tissue markers that could be used as guidance during access. A system that can both confirm access and avoid inadvertent organ injury is needed. METHODS: A 21G micropuncture needle was modified to include two small electrodes at the needle tip. With continuous bioimpedance monitoring from the electrodes, the needle was used to access the pericardium in porcine models (n  =  4). The needle was also visualized in vivo by using an electroanatomical map (n  =  2). Bioimpedance data from different tissues were analyzed retrospectively. RESULTS: Bioimpedance data collected from the subcutaneous space (992.8 ± 13.1 Ω), anterior mediastinum (972.2 ± 14.2 Ω), pericardial space (323.2 ± 17.1 Ω), mid-myocardium (349.7 ± 87.6 Ω), right ventricular cavity (235.0 ± 9.7 Ω), lung (1142.0 ± 172.0 Ω), liver (575.0 ± 52.6 Ω), and blood (177.5 ± 1.9 Ω) differed significantly by tissue type (P < .01). Phase data in the frequency domain correlated well with the needle being in the pericardial space. A simple threshold analysis effectively separated lung (threshold  =  1120.0 Ω) and blood (threshold  =  305.9 Ω) tissues from the other tissue types. CONCLUSIONS: Continuous bioimpedance monitoring from a modified micropuncture needle during pericardial access can be used to clearly differentiate tissues. Combined with traditional imaging modalities, this system allows for confirming access to the pericardial space while avoiding inadvertent puncture of other organs, creating a safer and more efficient needle-access procedure.

Thromboembolism in Atrial Fibrillation: Role of the Left Atrial Appendage.

Atrial fibrillation (AF) is the most common arrhythmia. Patients with AF have a higher risk for thromboembolism than individuals without AF. The left atrial appendage (LAA) is the main source of thromboembolism because of its anatomic, mechanical, and electrophysiologic properties, and accounts for more than 90% of thrombus formation in patients with AF. Advancement in imaging expands knowledge about anatomic and physiologic characteristics of LAA. The risk of thromboembolism events in patients with AF depends on clinical comorbidities and structural and physiologic parameters of atria, especially LAA. This article discusses AF-related thromboembolic events and the role of the LAA.

Exclusion of electrical and mechanical function of the left atrial appendage in patients with persistent atrial fibrillation: differences in efficacy and safety between endocardial ablation vs epicardial LARIAT ligation (the EXCLUDE LAA study).

BACKGROUND: Electrical isolation of the left atrial appendage (LAA) may provide incremental benefits for arrhythmia management in patients undergoing radiofrequency ablation (RFA) for persistent atrial fibrillation (AF). OBJECTIVE: The aim of this study was to compare efficacy and safety of endocardial ablation and LAA exclusion with LARIAT device for electrical and mechanical exclusion of LAA. METHODS: We compared patients who underwent endocardial LAA isolation during index RFA for persistent AF and underwent a repeat RFA to patients who underwent LAA exclusion with LARIAT device followed by RFA for AF in this multicenter registry. Efficacy of electrical and mechanical isolation of LAA was assessed. RESULTS: We included 182 patients of which 91 patients underwent endocardial LAA isolation during RFA for AF, and 91 patients underwent LAA exclusion with LARIAT device followed by RFA for AF. Baseline characteristics were similar except for higher CHA2DS2-VASc score, coronary artery disease, and prior stroke rate in LARIAT arm. Persistence of electrical isolation (measured at beginning of second procedure) after LARIAT procedure was higher than one-time AF-RFA (96.7% vs 52.8%, p < 0.01). Acute pulmonary vein isolation rates were similar in both arms. AF recurrence rate after second isolation attempts at 1 year was similar in both arms. No difference in major complications was noted between both arms. CONCLUSIONS: LAA exclusion with LARIAT device appears to be more efficacious as compared to one-time endocardial ablation, but not compared to repeat isolation, in achieving complete electrical isolation of LAA for persistent AF.

Long-term clinical outcomes from real-world experience of left atrial appendage exclusion with LARIAT device.

BACKGROUND: Left atrial appendage closure (LAAC) with LARIAT has emerged as one of the alternatives to oral anticoagulation (OAC) in patients with nonvalvular atrial fibrillation (AF). Our aim was to study long-term outcomes in patients undergoing LARIAT procedure. METHODS: We analyzed patients screened for LARIAT device in four centers between December 2009 and June 2012. Out of these, patients who didn't undergo LAAC with the LARIAT device due to unfavorable LAA morphology and other preprocedural contraindications were included in control group. We analyzed thromboembolism, bleeding events, and mortality between LAA and control group. RESULTS: About 153 patients were screened. Out of these, 108 (70.6%) patients underwent LARIAT placement (LAA arm) and 45 (29.4%) excluded patients were included in control arm. There were no differences in CHADS2 and CHA2 DS2 -VASc score. Mean HAS-BLED score was significantly higher in the LARIAT group (3.5 ± 1.06 vs 3.09 ± 1.22, P = .04). Mean follow-up time (in years) was 6.56 ± 0.84 in LAA and 6.5 ± 1.26 in control arm. During follow-up period, the LARIAT group was associated with significantly less thromboembolic events (1.9% vs 24%, P < .001), bleeding events (9.2% vs 24.4%, P = .03), and mortality (5.6% vs 20%, P = .01) as compared with the control group. CONCLUSIONS: Long-term data from routine clinical practice from our study suggests that LAA exclusion with LARIAT device is an effective treatment in management of nonvalvular AF patients with high risk of stroke, bleeding, and mortality. Further randomized trials, such as aMAZE, will provide more insight in this expanding field.

Complex Left Atrial Appendage Morphology Is an Independent Risk Factor for Cryptogenic Ischemic Stroke.

Importance: Ischemic strokes pose a significant health burden. However, the etiology of between 20 and 40% of these events remains unknown. Left atrial appendage morphology may influence the occurrence of thromboembolic events. Design: A retrospective cross-sectional study was conducted to investigate the role of LAA morphology in patients with atrial fibrillation (AF) and cardioembolic-associated stroke and patients with cryptogenic stroke without atrial fibrillation. LAA morphology is classified into two groups: (1) simple (chicken-wing) vs. (2) complex (non-chicken wing) based on transesophageal echocardiography (TEE) findings. In addition to the LAA morphology, left atrial parameters, including orifice diameter, depth, emptying velocity, and filling velocity, were collected for both groups. Mathematical, computational models were constructed to investigate flow velocities in chicken-wing and non-chicken wing morphological patterns to assess LAA function further. Findings: TEE values for volume, size, emptying, and filling velocities were similar between simple and complex LAA morphology groups. Patients with cryptogenic stroke without coexisting AF were noted to have significantly higher rates of complex LAA morphology. Chicken-wing LAA morphology was associated with four-fold higher flow rate (kg/s) in computational simulations. Conclusions: Complex LAA morphology may be an independent contributing factor for cryptogenic strokes. Further studies are warranted to investigate the mechanism involved in LAA morphology and thromboembolic events.

Epicardial Left Atrial Appendage Exclusion Reduces Blood Pressure in Patients With Atrial Fibrillation and Hypertension.

BACKGROUND: Percutaneous left atrial appendage exclusion (LAAE) has evolved as an alternative strategy for stroke prevention in atrial fibrillation (AF). Recent observational data have suggested that epicardial LAAE can have substantial impact on arrhythmia burden and hemodynamic profile. OBJECTIVES: The authors aimed to study the impact of epicardial versus endocardial LAAE on systemic blood pressure in hypertensive AF patients. METHODS: This was a prospective, nonrandomized study comparing 247 patients who underwent epicardial LAAE with 124 patients with endocardial exclusion. Clinical outcomes were measured at 3 months and 1 year. Primary outcome was improvement in systolic blood pressure (SBP) between both groups compared with baseline. Secondary outcome included changes in diastolic pressures (DBP), serum electrolytes, and creatinine. RESULTS: There was no significant difference in baseline SBP between epicardial and endocardial groups. SBP was significantly lower in the epicardial group both at 3 months (122 ± 11.8 mm Hg vs. 129.7 ± 8.2 mm Hg; p < 0.001) and 1 year (123 ± 11.6 mm Hg vs. 132.2 ± 8.8 mm Hg; p < 0.001) compared with the endocardial group. An adjusted multivariate linear mixed effects model demonstrated that epicardial LAAE significantly decreased SBP by 7.4 mm Hg at 3 months and by 8.9 mm Hg at 1 year (p < 0.0001). There was a trend toward lower DBP with epicardial LAAE at 3 months by 1.3 mm Hg (p = 0.2) and at 1 year by 1.8 mm Hg (p = 0.09). There was no significant difference in serum electrolytes and creatinine between both groups. CONCLUSIONS: In hypertensive AF patients, epicardial LAAE significantly decreases SBP both at 3 and 12 months compared with endocardial exclusion.

Anatomical and electrical remodeling with incomplete left atrial appendage ligation: Results from the LAALA-AF registry.

BACKGROUND: The anatomical, electrical, and clinical impact of incomplete Lariat left atrial appendage ligation remains unclear. METHODS: We studied LAA anatomy pre- and postligation using contrast enhanced-computed tomography (CT) scans in 91 patients with atrial fibrillation (AF) who subsequently underwent catheter ablation (CA). RESULTS: Eleven patients had an incomplete exclusion (12%) with a central leak ranging from 1 to 5 mm. Despite incomplete ligation; the LAA volume were reduced by 67% postprocedurally when compared to preprocedure. In 7 patients with a leak between 1 and 3 mm, there was a 77% reduction in LAA volume beyond the ligation site suggestive of remodeling of the LAA. In 4 patients with larger (4-5 mm) leak the LAA remnants (LAARs) were slightly larger than those with smaller leaks on follow-up CT scan. Three out of the 4 demonstrated LAA electrical activity during CA and underwent isolation of the LAA ostium. Follow-up imaging showed two of these LAARs completely sealed with no communication with the left atrium. There was no significant difference in the AF recurrence rates between the patients who had a leak versus those with complete ligation (4 of 11 [36%] vs. 22 of 80 [27%]; P  =  0.6). Oral anticoagulation was discontinued in all patients with small leaks and 2 patients with large leaks that sealed completely upon follow-up imaging. There were no strokes or TIAs at 12 months. CONCLUSION: Despite incomplete LAA ligation by Lariat device there is significant anatomical and electrical remodeling that resulted in reduction in LAA size, volume, and electrical activity.

Near-field impedance accurately distinguishes among pericardial, intracavitary, and anterior mediastinal position.

INTRODUCTION: Epicardial catheter ablation is increasingly used to treat arrhythmias with an epicardial component. Nevertheless, percutaneous epicardial access remains associated with a significant risk of major complications. Developing a technology capable of confirming proper placement within the pericardial space could decrease complication rates. The purpose of this study was to examine differences in bioimpedance among the pericardial space, anterior mediastinum, and right ventricle. METHODS: An ovine model (n = 3) was used in this proof-of-concept study. A decapolar catheter was used to collect bipolar impedance readings; data were collected between each of five electrode pairs of varying distances. Data were collected from three test regions: the pericardial space, anterior mediastinum, and right ventricle. A control region in the inferior vena cava was used to normalize the data from the test regions. Analysis of variance was used to test for differences among regions. RESULTS: A total of 10 impedance values were collected in each animal between each of the five electrode pairs in the three test regions (n = 340) and the control region (n = 145). The average normalized impedance values were significantly different among the pericardial space (1.760 ± 0.370), anterior mediastinum (3.209 ± 0.227), and right ventricle (1.024 ± 0.207; P < 0.0001). In post hoc testing, the differences between each pair of regions were significant, as well (P < 0.001 for all). CONCLUSION: Impedance values are significantly different among these three anatomical compartments. Therefore, impedance can be potentially used as a means to guide percutaneous epicardial access.

Anesthetic Management of Patients Undergoing Percutaneous Endocardial and Epicardial Left Atrial Appendage Occlusion.

Atrial fibrillation is the most common cardiac arrhythmia in adults affecting almost 6 million adults in the United States. The 2 most common comorbidities associated with atrial fibrillation are heart failure and thromboembolic events. Heart failure symptoms may be treated with rate control, antiarrhythmic medications or by catheter ablation. Unfortunately, despite optimal medical management, thromboembolic events still occur. Recently, there has been a great deal of interest and innovation in finding an alternative to chronic anticoagulation. Several percutaneous left atrial appendage occlusion devices have been developed over recent years, some of which have proven to be noninferior to anticoagulation in preventing strokes in atrial fibrillation patients. The 2 most widely used left atrial appendage occlusion devices are the WATCHMAN (Atritech Inc, Plymouth, MN, USA) and the LARIAT (SentreHEART, Palo Alto, CA, USA) devices. After a detailed description of the procedures, the anesthetic considerations of each procedure and management of specific adverse events are discussed within this review.

Accuracy of Voltage Signal Measurement During Radiofrequency Delivery Through the SMARTTOUCH Catheter.

INTRODUCTION: Current methods for measuring voltage during radiofrequency (RF) ablation (RFA) necessitate turning off the ablation catheter. If voltage could be accurately read without signal attenuation during RFA, turning off the catheter would be unnecessary, allowing continuous ablation. We evaluated the accuracy of the Thermocool SMARTTOUCH catheter for measuring voltage while RF traverses the catheter. METHODS AND RESULTS: We studied 26 patients undergoing RFA for arrhythmias. A 7.5F SMARTTOUCH catheter was used for sensing voltage and performing RFA. Data were collected from the Carto-3 3-dimensional mapping system. Voltages were measured during ablation (RF-ON) and immediately before or after ablation (RF-OFF). In evaluating the accuracy of RF-ON measurements, we utilized the RF-OFF measure as the gold standard. We measured 465 voltage signals. The median values were 0.2900 and 0.3100 for RF-ON and RF-OFF, respectively. Wilcoxon signed rank testing showed no significant difference in these values (P = 0.608). The intraclass correlation coefficient (ICC) was 0.96, indicating that voltage measurements were similarly accurate during RF-OFF versus RF-ON. Five patients had baseline atrial fibrillation (AF), for whom 82 ablation points were measured; 383 additional ablation points were measured for the remaining patients. The voltages measured during RF-ON versus RF-OFF were similar in the presence of AF (P = 0.800) versus non-AF rhythm (P = 0.456) (ICC, 0.96 for both). CONCLUSION: Voltage signal measurement was similarly accurate during RF-ON versus RF-OFF independent of baseline rhythm. Physicians should consider not turning off the SMARTTOUCH ablation catheter when measuring voltage during RFA.

Subcutaneous Versus Transvenous Implantable Defibrillator Therapy: A Meta-Analysis of Case-Control Studies.

OBJECTIVES: This study aims to conduct a meta-analysis comparing efficacy and safety outcomes between subcutaneous implantable cardioverter-defibrillator (S-ICD) and transvenous implantable cardioverter-defibrillator (TV-ICD). BACKGROUND: The S-ICD was developed to minimize complications related to the conventional TV-ICD. Direct comparison of clinical outcomes between the 2 devices has been limited by varying patient characteristics and definitions of complications with no randomized trials completed comparing these systems. METHODS: Studies in the PubMed and Embase databases and secondary referencing sources were systematically reviewed. Studies meeting criteria were included in the meta-analysis. Baseline characteristics and outcome data of the S-ICD and TV-ICD groups were appraised and analyzed. A random-effects model was used to derive odds ratio (OR) with 95% confidence interval (CI). RESULTS: Five studies met inclusion criteria. Baseline characteristics were similar between the S-ICD and TV-ICD groups. Fewer lead complications occurred in the S-ICD group compared to the TV-ICD group (OR: 0.13; 95% CI: 0.05 to 0.38). The infection rate was similar between the S-ICD and TV-ICD groups (OR: 0.75; 95% CI: 0.30 to 1.89). There were no differences in system or device failures between groups (OR: 1.13; 95% CI: 0.43 to 3.02). Overall, inappropriate therapy (T-wave oversensing, supraventricular tachycardia, episodes of inappropriate sensing) was similar between the 2 groups (OR: 0.87; 95% CI: 0.51 to 1.49). However, the nature of inappropriate therapy was different between the S-ICD and TV-ICD groups. Both devices appear to perform equally well with respect to appropriate shocks. CONCLUSIONS: S-ICD reduced lead-related complications but was similar to TV-ICD with regard to non-lead-related complications, including inappropriate therapy. These results support the concept that S-ICD is a safe and effective alternative to TV-ICD in appropriate patients.