Trends in Use of Single- vs Dual-Chamber Implantable Cardioverter-Defibrillators Among Patients Without a Pacing Indication, 2010-2018.

Importance: Use of dual-chamber implantable cardioverter-defibrillator (ICD) systems among patients without a pacing indication is an example of low-value care given higher procedural risks, higher costs, and little evidence for benefit from an atrial lead. However, variation in the use of dual-chamber systems was present among patients without a pacing indication. Objective: To examine the temporal trends and hospital variation in use of single- and dual-chamber ICD implantation among patients without a pacing indication undergoing first-time ICD implantation. Design, Setting, and Participants: A multicenter cross-sectional study was conducted using the US National Cardiovascular Data Registry ICD Registry. A total of 266 182 patients undergoing initial implantation of a single- or dual-chamber transvenous ICD without a bradycardia pacing indication, class I or II cardiac resynchronization therapy indication, or history of atrial fibrillation or atrial flutter were included. The study was conducted from April 1, 2010, to December 31, 2018; data analysis was performed from October 19, 2020, to January 5, 2022. Exposures: Implantation of a single- or dual-chamber ICD. Main Outcomes and Measures: Temporal trends among patients undergoing single- vs dual-chamber ICDs were determined using the Cochran-Armitage trend test, and hospital-level variation using adjusted hospital median odds ratios was examined. Results: A total of 266 182 patients (single-chamber ICD, 134 925; dual-chamber ICD, 131 257) were included in this analysis; mean (SD) age was 58.0 (14.0) years and 91 990 patients (68.2%) were men. The use of dual-chamber ICDs decreased from 64.7% (n = 15 694) in 2010 to 42.2% (n = 9762) in 2018 (P < .001). Adjusted for patient characteristics, the median hospital-level proportion of single-chamber ICDs increased from 42.9% (95% CI, 42.6%-45.0%) in 2010 to 50.0% (95% CI, 47.8%-51.0%) in 2018. The median odds ratio for the use of dual-chamber ICDs, adjusted for patient characteristics, was 1.6 (95% CI, 1.6-1.8) in 2010 and 1.5 (95% CI, 1.5-1.8) in 2018, indicating decreasing but persistent variation in use. Conclusions and Relevance: In this national study of US patients undergoing first-time ICD implantation without a clinical indication for an atrial lead, the use of dual-chamber devices decreased. However, institutional variability in the use of atrial leads persists, suggesting differences in individual or institutional cultures of real-world practice and opportunity to reduce this low-value practice.

Increased incidence of cavotricuspid isthmus atrial flutter following slow pathway ablation.

PURPOSE: The incidence of atrial flutter following radiofrequency ablation of supraventricular tachycardias is poorly understood. Ablation of atrioventricular nodal reentry tachycardia may place patients at risk of flutter because ablation of the slow pathway is in close proximity to the cavotricuspid isthmus. This study aims to evaluate the risk of atrial flutter following ablation of atrioventricular nodal reentry tachycardia relative to ablation of other supraventricular tachycardias. METHODS: A single-center retrospective analysis was completed for all supraventricular tachycardia ablations performed between July 2006 and July 2016. Patient and procedural details were collected for 544 patients who underwent atrioventricular nodal reentry tachycardia ablation (n = 342), atrioventricular reentry tachycardia ablation (n = 125), or atrial tachycardia ablation (n = 60). Follow-up for flutter after ablation of their incident arrhythmia was assessed. RESULTS: Patients who underwent atrioventricular nodal reentry tachycardia ablation were more likely to develop CTI-dependent flutter than patients who underwent ablation of other supraventricular tachycardias (4.97% vs. 0%; p = 0.002). Compared with patients who did not develop flutter, patients who developed flutter after atrioventricular nodal reentry tachycardia ablation were more likely to have undergone ablation of atypical atrioventricular nodal reentry tachycardia (11.8% vs. 2.15%; p = 0.016). CONCLUSIONS: We identified an association between atrioventricular nodal reentry tachycardia ablation and development of CTI-dependent atrial flutter. This finding may have implications for the management and follow-up after atrioventricular nodal reentry tachycardia ablation.

Machine Learning Methodologies for Prediction of Rhythm-Control Strategy in Patients Diagnosed With Atrial Fibrillation: Observational, Retrospective, Case-Control Study.

BACKGROUND: The identification of an appropriate rhythm management strategy for patients diagnosed with atrial fibrillation (AF) remains a major challenge for providers. Although clinical trials have identified subgroups of patients in whom a rate- or rhythm-control strategy might be indicated to improve outcomes, the wide range of presentations and risk factors among patients presenting with AF makes such approaches challenging. The strength of electronic health records is the ability to build in logic to guide management decisions, such that the system can automatically identify patients in whom a rhythm-control strategy is more likely and can promote efficient referrals to specialists. However, like any clinical decision support tool, there is a balance between interpretability and accurate prediction. OBJECTIVE: This study aims to create an electronic health record-based prediction tool to guide patient referral to specialists for rhythm-control management by comparing different machine learning algorithms. METHODS: We compared machine learning models of increasing complexity and used up to 50,845 variables to predict the rhythm-control strategy in 42,022 patients within the University of Colorado Health system at the time of AF diagnosis. Models were evaluated on the basis of their classification accuracy, defined by the F1 score and other metrics, and interpretability, captured by inspection of the relative importance of each predictor. RESULTS: We found that age was by far the strongest single predictor of a rhythm-control strategy but that greater accuracy could be achieved with more complex models incorporating neural networks and more predictors for each participant. We determined that the impact of better prediction models was notable primarily in the rate of inappropriate referrals for rhythm-control, in which more complex models provided an average of 20% fewer inappropriate referrals than simpler, more interpretable models. CONCLUSIONS: We conclude that any health care system seeking to incorporate algorithms to guide rhythm management for patients with AF will need to address this trade-off between prediction accuracy and model interpretability.

Open surgical ablation of ventricular tachycardia: Utility and feasibility of contemporary mapping and ablation tools.

BACKGROUND: Ventricular tachycardia (VT) catheter ablation success may be limited when transcutaneous epicardial access is contraindicated. Surgical ablation (SurgAbl) is an option, but ablation guidance is limited without simultaneously acquired electrophysiological data. OBJECTIVE: We describe our SurgAbl experience utilizing contemporary electroanatomic mapping (EAM) among patients with refractory VT storm. METHODS: Consecutive patients with recurrent VT despite antiarrhythmic drugs (AADs) and prior ablation, for whom percutaneous epicardial access was contraindicated, underwent open SurgAbl using intraoperative EAM guidance. RESULTS: Eight patients were included, among whom mean age was 63 ± 5 years, all were male, mean left ventricular ejection fraction was 39% ± 12%, and 2 (25%) had ischemic cardiomyopathy. Reasons for surgical epicardial access included dense adhesions owing to prior cardiac surgery, hemopericardium, or pericarditis (n = 6); or planned left ventricular assist device (LVAD) implantation at time of SurgAbl (n = 2). Cryoablation guided by real-time EAM was performed in all. Goals of clinical VT noninducibility or core isolation were achieved in 100%. VT burden was significantly reduced, from median 15 to 0 events in the month pre- and post-SurgAbl (P = .01). One patient underwent orthotopic heart transplantation for recurrent VT storm 2 weeks post-SurgAbl. Over mean follow-up of 3.4 ± 1.7 years, VT storm-free survival was achieved in 6 (75%); all continued AADs, although at lower dose. CONCLUSION: Surgical mapping and ablation of refractory VT with use of contemporary EAM is feasible and effective, particularly among patients with contraindication to percutaneous epicardial access or with another indication for cardiac surgery.

Use and Outcomes of Dual Chamber or Cardiac Resynchronization Therapy Defibrillators Among Older Patients Requiring Ventricular Pacing in the National Cardiovascular Data Registry Implantable Cardioverter Defibrillator Registry.

Importance: Frequent right ventricular (RV) pacing can cause and exacerbate heart failure. Cardiac resynchronization therapy (CRT) has been shown to be associated with improved outcomes among patients with reduced left ventricular ejection fraction who need frequent RV pacing, but the patterns of use of CRT vs dual chamber (DC) devices and the associated outcomes among these patients in clinical practice is not known. Objective: To assess outcomes, variability in use of device type, and trends in use of device type over time among patients undergoing implantable cardioverter defibrillator (ICD) implantation who were likely to require frequent RV pacing but who did not have a class I indication for CRT. Design, Setting, and Participants: This retrospective cohort study used the National Cardiovascular Data Registry (NCDR) ICD Registry. A total of 3100 Medicare beneficiaries undergoing first-time implantation of CRT defibrillator (CRT-D) or DC-ICD from 2010 to 2016 who had a class I or II guideline ventricular bradycardia pacing indication but not a class I indication for CRT were included. Data were analyzed from August 2018 to October 2019. Exposures: Implantation of a CRT-D or DC-ICD. Main Outcomes and Measures: All-cause mortality, heart failure hospitalization, and complications were ascertained from Medicare claims data. Multivariable Cox proportional hazards models and Fine-Gray models were used to evaluate 1-year mortality and heart failure hospitalization, respectively. Multivariable logistic regression was used to evaluate 30-day and 90-day complications. All models accounted for clustering. The median odds ratio (MOR) was used to assess variability and represents the odds that a randomly selected patient receiving CRT-D at a hospital with high implant rates would receive CRT-D if they had been treated at a hospital with low CRT-D implant rates. Results: A total of 3100 individuals were included. The mean (SD) age was 76.3 (6.4) years, and 2500 (80.6%) were men. The 1698 patients (54.7%) receiving CRT-D were more likely than those receiving DC-ICD to have third-degree atrioventricular block (828 [48.8%] vs 432 [30.8%]; P < .001), nonischemic cardiomyopathy (508 [29.9%] vs 255 [18.2%]; P < .001), and prior heart failure hospitalizations (703 [41.4%] vs 421 [30.0%]; P < .001). Following adjustment, CRT-D was associated with lower 1-year mortality (hazard ratio [HR], 0.70; 95% CI, 0.57-0.87; P = .001) and heart failure hospitalization (subdistribution HR, 0.77; 95% CI, 0.61-0.97; P = .02) and no difference in complications compared with DC-ICD. Hospital variation in use of CRT was present (MOR, 2.00), and the use of CRT in this cohort was higher over time (654 of 1351 [48.4%] in 2010 vs 362 of 594 [60.9%] in 2016; P < .001). Conclusions and Relevance: In this cohort study of older patients in contemporary practice undergoing ICD implantation with a bradycardia pacing indication but without a class I indication for CRT, CRT-D was associated with better outcomes compared with DC devices. Variability in use of device type was observed, and the rate of CRT implantation increased over time.

Use of cell phone adapters is associated with reduction in disparities in remote monitoring of cardiac implantable electronic devices.

BACKGROUND: Remote monitoring (RM) of cardiac implantable electronic devices (CIEDs) is standard of care. However, it is underutilized. In July 2012, our institution began providing cell phone adapters (CPAs) to patients free of charge following CIED implantation to improve remote transmission (RT) adherence. METHODS: Patients in our institution's RM database from January 1, 2010, thru June 30, 2015, were retrospectively reviewed. There were 2157 eligible patients. Remote transmission proportion (RTP) and time to transmission (TT) were compared pre- and post-implementation of free CPA. Chi-squared analysis and Kruskal-Wallis tests were performed to compare RTP and TT. RESULTS: There was a significant increase in RTP (134 [18.4%] vs 99 [54.7%]; p < 0.001) and decrease in median TT in days (189[110-279] vs 58 [10-149]; p < 0.001) after CPAs were provided to patients. Caucasian patients were more likely than African Americans and Hispanics to use RM prior to CPAs (p = 0.04). After the implementation of CPAs, there was a significant increase in RTP for all racial groups (< 0.001) with no difference in RTP among racial groups (p = 0.18). The RTP for urban residents was significantly greater than non-urban residents with CPAs (p = 0.008). Patients greater than 70 years of age were significantly less likely to participate in RT before and after CPAs were provided (p = 0.03, p = 0.01, respectively). CONCLUSIONS: CPAs significantly improve RTP and reduce median TT for all patients regardless of race, geographic residence, and age (> 70 years old to lesser extent). Broad institution of CPAs following ICD implantation could potentially reduce disparity in RTP and deserves more study.

Uncovering a unique path: Antidromic AVRT utilizing a left anteroseptal Mahaim-like accessory pathway.

A 40-year-old man presented to our emergency department 2 hours after onset of shortness of breath, palpitations, and presyncope secondary to an adenosine-responsive wide complex tachycardia. Electrophysiology study was diagnostic for antidromic atrioventricular (AV) reentrant tachycardia utilizing a muscular connection from the anterior interventricular vein to the left ventricle with Mahaim-like properties, successfully treated with ablation in the distal coronary sinus (CS) system. This case highlights accessory pathways (a) with unique features (i.e., Mahaim-like characteristics) and (b) involving musculature from the distal CS system, thereby limiting the value of endocardial ablation for durable treatment. Importantly, the coronary venous system is an accessible vascular network for evaluation and catheter ablation of such arrhythmias.

Continuous ablation improves lesion maturation compared with intermittent ablation strategies.

BACKGROUND: Interrupted ablation is increasingly proposed as part of high-power short-duration radiofrequency ablation (RFA) strategies and may also result from loss of contact from respiratory patterns or cardiac motion. To study the extent that ablation interruption affects lesions. METHODS: In ex vivo and in vivo experiments, lesion characteristics and tissue temperatures were compared between continuous (group 1) and interrupted (groups 2 and 3) RFA with equal total ablation duration and contact force. Extended duration ablation lesions were also characterized from 1 to 5 minutes. RESULTS: In the ex vivo study, continuous RFA (group 1) produced larger total lesion volumes compared with each interrupted ablation lesion group (273.8 ± 36.5 vs 205.1 ± 34.2 vs 174.3 ± 32.3 mm3 , all P < .001). Peak temperatures for group 1 were higher at 3 and 5 mm than groups 2 and 3. In vivo, continuous ablation resulted in larger lesions, greater lesion depths, and higher tissue temperatures. Longer ablation durations created larger lesion volumes and increased lesion depths. However, after 3 minutes of ablation, the rate of lesion volume, and depth formation decreased. CONCLUSIONS: Continuous RFA delivery resulted in larger and deeper lesions with higher tissue temperatures compared with interrupted ablation. This study may have implications for high-power short duration ablation strategies, motivates strategies to reduce variations in ablation delivery, and provides an upper limit for ablation duration beyond which power delivery has diminishing returns.

Impact of epicardial adipose tissue and catheter ablation strategy on biophysical parameters and ablation lesion characteristics.

BACKGROUND: Epicardial adipose (EA) tissue may limit effective radiofrequency ablation (RFA). OBJECTIVES: We sought to evaluate the lesion formation of different ablation strategies on ventricular myocardium with overlying EA. METHODS: Bovine myocardium with EA was placed in a circulating saline bath in an ex vivo model. Open-irrigated (OI) RFA was performed, parallel to the myocardium, over fat at 50 W for variable RF durations, variable contact force, catheter configurations (unipolar RF vs bipolar RF), and catheter irrigants (normal saline vs half-normal saline). Ablation was also performed with a needle-tipped ablation catheter (NTAC), perpendicular to the myocardium. RESULTS: Increasingly thick EA attenuated lesion size regardless of ablation strategy. RF applied with longer durations and increasing CF produced larger lesion volumes and deeper lesions with ablation over EA more than 3 mm but was unable to produce measurable lesions when EA less than 3 mm. Similarly, ablation with half normal saline irrigant created slightly deeper lesions than bipolar RF and unipolar RF with normal saline as EA thickness increased, but was unable to produce measurable lesions when EA more than 3 mm. Of all ablation strategies, only NTAC produced effective lesion volumes when ablating over thick (>3 mm) EA. CONCLUSIONS: While EA attenuates lesion depth and size, relatively larger, and deeper lesions can be achieved with longer RFA duration, higher CF, half normal saline irrigant, and, to a greater extent, by utilizing bipolar RF or NTAC, but only over thin adipose (<3 mm). Of those catheters/strategies tested, only NTAC was able to effectively deliver RF over thick (>3 mm) EA with this model.

Analysis of Temporal Trends and Variation in the Use of Defibrillation Testing in Contemporary Practice.

Importance: Defibrillation testing (DFT) is performed during implantable cardioverter-defibrillator (ICD) implantation to assess the capacity of the device to detect and terminate ventricular arrhythmias. However, DFT can result in complications and omission of its use has been shown to be safe. Objective: To describe temporal trends and variation in the use of DFT in contemporary practice in the United States. Design, Setting, and Participants: This multicenter cross-sectional study used data from the National Cardiovascular Data Registry ICD Registry. A total of 499 211 patients from 1794 different facilities undergoing first-time ICD implantation from April 2010 to December 2015 were included. Data analysis was performed from May 20, 2015, to August 15, 2019. Exposure: Defibrillation testing was assessed using the National Cardiovascular Data Registry ICD Registry. Main Outcomes and Measures: Defibrillation testing rates and median odds ratios (MORs) were assessed over time. The MOR represents the odds that a randomly selected patient receiving testing at a hospital with high testing rates would be tested compared with if he or she had received care at a hospital with low testing rates. Results: Of the 499 211 patients from 1794 different facilities included in this analysis, the mean (SD) age of the population was 65.5 (13.4) years and 356 681 patients (71.4%) were men. The use of DFT declined from 71.6% in the first calendar quarter of 2010 to 36.4% in the fourth quarter of 2015 (P < .001). Patients undergoing DFT were more likely than those without testing to have ischemic heart disease (170 569 [58.1%] vs 116 295 [56.6%]), ventricular tachycardia (91 500 [31.2%] vs 58 949 [28.7%]), and less advanced heart failure (New York Heart Association class I and II, 153 188 [52.2%] vs 91 215 [44.4%]) (P < .001 for all). The MOR for the use of defibrillation testing was 3.78 (95% CI, 3.54-4.03) in 2010, increasing to 6.05 (95% CI, 5.61-6.52) in 2015, indicating that by 2015 a randomly selected patient receiving testing at a hospital with high testing rates would have a 6-fold higher odds of being tested than if they had received care at a hospital with low testing rates. Conclusions and Relevance: Defibrillation testing at the time of ICD placement in the United States may have declined over time; however, institutional variation in its use appears to be marked and increased. This variability in the reduced use of defibrillation testing could reflect differences in individual or institutional cultures of practice.

Follow-Up After Catheter Ablation of Papillary Muscles and Valve Cusps.

OBJECTIVES: The goal of this study was to determine the impact of catheter ablation in the region of papillary muscles (PMs) and valvular cusps (VC) on mitral, tricuspid, or aortic valve function. BACKGROUND: Ventricular arrhythmias arising from PMs and VCs often require extensive catheter ablation. Little is known regarding the risk of valve dysfunction after radiofrequency catheter ablation of such arrhythmias. METHODS: A retrospective analysis was completed for 149 PM and VC VT/premature ventricular contraction (PVC) ablations from 2008 to 2018 at our institution. Patient and procedural details were collected for VT and PVC ablation cases involving PMs and VCs with available echocardiographic data pre-ablation and post-ablation (within 6 months). Degree of valvular regurgitation (VR) was graded from 0 (none) to 4 (severe), and significant valvular dysfunction was defined as a 2+ change in VR. RESULTS: Of 149 radiofrequency catheter ablation cases, there were 84 (56%) aortic valve cusp ablations, 60 (40%) left ventricular PM ablations, and 5 (3%) right ventricular PM ablations. There were no statistically significant differences between pre-ablation and post-ablation VR severity (p = 0.33). No patients had a 2+ grade change in VR severity when pre-ablation and post-ablation echocardiograms were compared. There were no significant sequelae requiring intervention in the post-ablation period. On follow-up of 36 ± 9 months, for those with a change in VR, the severity had improved to baseline or remained stable. CONCLUSIONS: Despite often-times extensive ablation on and around valvular networks, risk of longstanding or permanent valvular dysfunction after VT/PVC ablation is rare.

Bipolar radiofrequency ablation creates different lesion characteristics compared to simultaneous unipolar ablation.

INTRODUCTION: Both bipolar and simultaneous radiofrequency ablation (bRFA, simRFA) have been used to treat thick midmyocardial substrate as well as during circular, multipolar ablation between shorter distances. OBJECTIVES: We sought to evaluate the biophysical parameters of simRFA, sequential unipolar RFA (seqRFA), and bRFA. METHODS: Bovine myocardium was placed in a circulating saline bath. To simulate thick substrate conditions, two open irrigated ablation catheters were oriented across from each other, with myocardium in between. Thermocouples were placed in the center, ±2 mm, of the myocardium. Unipolar ablations were performed sequentially or simultaneously at 50 W for 60 seconds and compared to bRFA using the same settings. In addition, to simulate multipolar ablation, two open irrigated ablation catheters were oriented on the same side and perpendicular to myocardium at 1, 2, and 4 mm spacing. SimRFA were performed at 15 and 25 W for 60 seconds and compared to bRFA. RESULTS: For thicker tissue, simRFA produced similar lesion volume and depth compared to bRFA but with a lesion geometry similar to seqRFA. Unlike seqRFA and simRFA, bRFA had a necrotic core spanning the myocardium. Core depths, volumes, and temperatures were significantly greater for bRFA lesions compared to simRFA or seqRFA (Figure, P < .001). Similar results were consistent for bRFA and simRFA at shorter spacings. CONCLUSIONS: BRFA has greater core lesion temperatures, corresponding to a denser and larger necrotic core, than either simRFA or seqRFA. This may have implications for considering the optimal strategy for deep midmyocardial substrates or during multipolar ablation.

Electrophysiologic testing for diagnostic evaluation and risk stratification in patients with suspected cardiac sarcoidosis with preserved left and right ventricular systolic function.

INTRODUCTION: While cardiac sarcoidosis (CS) carries a risk of ventricular arrhythmias (VAs) and sudden cardiac death (SCD), risk stratification of patients with CS and preserved left ventricular/right ventricular (LV/RV) systolic function remains challenging. We sought to evaluate the role of electrophysiologic testing and programmed electrical stimulation of the ventricle (EPS) in patients with suspected CS with preserved ventricular function. METHODS: One hundred twenty consecutive patients with biopsy-proven extracardiac sarcoidosis and preserved LV/RV systolic function underwent EPS. All patients had either probable CS defined by an abnormal cardiac positron emission tomography or cardiac magnetic resonance imaging, or possible CS with normal advanced imaging but abnormal echocardiogram (ECG), SAECG, Holter, or clinical factors. Patients were followed for 4.5 ± 2.6 years for SCD and VAs. RESULTS: Seven of 120 patients (6%) had inducible ventricular tachycardia (VT) with EPS and received an implantable cardioverter defibrillator (ICD). Three patients (43%) with positive EPS later had ICD therapies for VAs. Kaplan-Meier analysis stratified by EPS demonstrated a significant difference in freedom from VAs and SCD (P = 0.009), though this finding was driven entirely by patients within the cohort with probable CS (P = 0.018, n = 69). One patient with possible CS and negative EPS had unrecognized progression of the disease and unexplained death with evidence of CS at autopsy. CONCLUSIONS: EPS is useful in the risk stratification of patients with probable CS with preserved LV and RV function. A positive EPS was associated with VAs. While a negative EPS appeared to confer low risk, close follow-up is needed as EPS cannot predict fatal VAs related to new cardiac involvement or disease progression.

Use of Cardiac Resynchronization Therapy Defibrillator in US Hospitals.

Importance: Cardiac resynchronization therapy (CRT) provides significant reduction in morbidity and mortality in select patients with left ventricular systolic dysfunction and specific parameters of electrocardiographic evidence of dyssynchrony. Relative to the 2012 American College of Cardiology/American Heart Association/Heart Rhythm Society guideline update for patient selection, little is known about the contemporary use of CRT in the United States. Objective: To describe the use of CRT defibrillator (CRT-D) in the period around guideline revision. Design, Setting, and Participants: All patients undergoing new CRT-D implantations in the National Cardiovascular Data Registry for implantable cardioverter-defibrillators from January 1, 2012, to December 31, 2015, at 1710 participating hospitals were identified for this population-based study. Rates of CRT-D implantation that were concordant and discordant with the 2012 American College of Cardiology/American Heart Association/Heart Rhythm Society update of the 2008 guidelines for device-based therapy were determined. Analysis began in January 2012. Main Outcomes and Measures: Increase in guideline-concordant CRT-D implantation. Results: Among 135 253 patients undergoing initial CRT-D implantation, 88 923 were included in the study cohort, of which 73 859 implants (83.1%) were guideline concordant. The proportion of guideline-concordant devices increased from 81.2% (16 710 of 20 481) in 2012 to 84.2% (20 515 of 24 356) in 2015 (P for trend < .001). Significant clustering was noted with 33% (565 of 1710) of hospitals accounting for greater than 70% (10 545 of 15 065) of guideline-discordant CRT-D implants. Conduction abnormalities, in particular, underlying right bundle branch block (3597 [23.9%] vs 7425 [10.1%]; P < .001) and nonspecific intraventricular conduction delay (3341 [22.2%] vs 4769 [6.5%]; P < .001) were more common in those who received guideline-discordant devices. Conclusions and Relevance: Rates of guideline-concordant CRT-D implantation increased during the study. The major fraction of guideline-discordant implants were clustered at a minority of hospitals. Conduction abnormalities, particularly non-left bundle branch block and nonspecific intraventricular conduction delay, correlated with guideline-discordant implants indicating continued opportunity for dissemination and understanding of guideline updates.

Ambulatory Rhythm Monitoring to Detect Late High-Grade Atrioventricular Block Following Transcatheter Aortic Valve Replacement.

BACKGROUND: High-grade atrioventricular block (H-AVB) is a well-described in-hospital complication of transcatheter aortic valve replacement (TAVR). Delayed high-grade atrioventricular block (DH-AVB) has not been systematically studied among outpatients post-TAVR, using latest-generation TAVR technology and in the early post-TAVR discharge era. OBJECTIVES: The purpose of this study was to assess utility of ambulatory event monitoring (AEM) in identifying post-TAVR DH-AVB and associated risk factors. METHODS: Patients without pre-existing pacing device undergoing TAVR at the University of Colorado Hospital from October 2016 to March 2018, and who did not require permanent pacemaker implantation pre-discharge, were discharged with 30-day AEM to assess for DH-AVB (≥2 days post-TAVR). Clinical and follow-up data were collected and compared among those without incident H-AVB. RESULTS: Among 150 consecutive TAVR patients without a prior pacing device, 18 (12%) developed H-AVB necessitating permanent pacemaker <2 days post-TAVR, 1 died pre-discharge, and 13 declined AEM; 118 had 30-day AEM data. DH-AVB occurred in 12 (10% of AEM patients, 8% of total cohort) a median of 6 days (range 3 to 24 days) post-TAVR. DH-AVB versus non-AVB patients were more likely to have hypertension and right bundle branch block (RBBB). Sensitivity and specificity of RBBB in predicting DH-AVB was 27% and 94%, respectively. CONCLUSIONS: DH-AVB is an underappreciated complication of TAVR among patients without pre-procedure pacing devices, occurring at rates similar to in-hospital, acute post-TAVR H-AVB. RBBB is a risk factor for DH-AVB but has poor sensitivity, and other predictors remain unclear. In this single-center analysis, AEM was helpful in expeditious identification and treatment of 10% of post-TAVR outpatients. Prospective study is needed to clarify incidence, risk factors, and patient selection for outpatient monitoring.

Esophageal position, measured luminal temperatures, and risk of atrioesophageal fistula with atrial fibrillation ablation.

BACKGROUND: Despite improvement in catheter ablation for atrial fibrillation (AF), ability to recognize and prevent esophageal injury remains challenging. We hypothesized that esophageal course may impact esophageal heating, as measured through ablation, and thereby, risk of injury. METHODS: We evaluated all patients undergoing first-time AF ablation with preprocedural computed tomography (CT) imaging from 2014 to 2016 at our institution, focusing on esophageal position at the left atrial (LA)/pulmonary vein junction. Esophageal luminal temperatures (ELTs) were analyzed by esophageal course. In exploratory work by investigation of published reports of atrioesophageal fistula (AEF), we evaluated for a relationship between esophageal course and risk of AEF. RESULTS: Of 68 patients, 48.5% had midline, 36.8% leftward, and 14.7% rightward esophageal positions. Of 20 patients (29% of cohort) with esophageal confinement-defined as a midline or leftward position relative to the LA, vertebrae, and aorta, with luminal distortion-14 had leftward position. No significant differences in patient or procedure characteristics were noted between confinement and nonconfinement cohorts. The average peak ELT was significantly higher in those with confinement (36.9°C vs 36.2°C, P < 0.05) and confinement with a left-sided esophagus (37.1°C vs 36.2°C, P < 0.05). There was a significant correlation between esophageal confinement and risk of AEF (odds ratio [OR]: 2.7, 95% confidence interval [CI]: 1.2-6.2, P < 0.01). CONCLUSION: Approximately one-third of patients undergoing AF ablation display leftward esophageal course along the ablation zone on preprocedure CT imaging, with a significant portion exhibiting esophageal confinement. In those with confinement, higher peak ELTs are noted with ablation. Esophageal confinement may be a risk factor for development of AEF.

Use of Tissue Electric and Ultrasound Characteristics to Predict and Prevent Steam-Generated Cavitation During High-Power Radiofrequency Ablation.

OBJECTIVES: Given a paucity of data, the aim of this study was to define predictors of steam pops (SPs) during open-irrigated radiofrequency ablation (RFA). BACKGROUND: SPs during RFA can lead to dire consequences, including perforation and stroke. METHODS: In an ex vivo bovine myocardium model, open-irrigated RFA was applied at 50 W for 60 s; intracardiac echocardiographic images for RFA with and without SPs was compared. Using an in vivo porcine model, open-irrigated RFA was applied at 50 W for 60 s, and RFA parameters of SPs were analyzed. A retrospective analysis was performed of recorded SPs during clinical ablation procedures over a 1-year period. RESULTS: For RFA SPs, there was 32% greater intracardiac echocardiographic tissue echogenicity than for RFA without SPs (p < 0.001). In addition, RFA SPs had more rapid increases of tissue echogenicity, particularly in the last 5 s before SPs. Compared with RFA without SPs, RFA SPs had larger impedance reductions (33.0 ± 16.0 Ω vs. 23.0 ± 10.8 Ω; p = 0.032). SPs were also associated with more rapid initial impedance reduction (1.40 Ω/s vs. 0.38 Ω/s for RFA without SPs; p = 0.001). Clinical SPs during ablation procedures had a significantly faster impedance reduction during the first 5 s of ablation compared with matched control ablations (15.7 ± 6.7 Ω vs. 8.1 ± 4.7 Ω; p < 0.0001). CONCLUSIONS: Certain echocardiographic and biophysical parameters during open-irrigated RFA are associated with increased SP risks. These include greater tissue echogenicity, larger total impedance reduction, rapid rate of initial impedance reduction, and rapid increase in tissue echogenicity.

Longer Duration Versus Increasing Power During Radiofrequency Ablation Yields Different Ablation Lesion Characteristics.

OBJECTIVES: The goal of this study was to characterize differences in ablation lesions with varying radiofrequency ablation (RFA) power and time. BACKGROUND: Increasing power delivery or prolonging duration can improve the efficacy of RFA. However, the extent to which ablation lesion characteristics change, based on varying degrees of power and duration, is unknown. METHODS: An ex vivo model consisting of viable bovine myocardium in a circulating warmed saline bath was used. An open irrigated RFA catheter was positioned with 10 g of force in the perpendicular position, and RFA was delivered at powers of 20, 30, 40, and 50 W and for various time intervals, up to a total of 90 s, at each power. An in vivo porcine thigh preparation model was used to perform RFA at 50 W for 5 s and 20 W for 30 s. Lesion volumes were analyzed. RESULTS: Greater power delivery and longer radiofrequency time increased ablation lesion size. However, compared with a proportional change in radiofrequency duration, the same proportional increase in power produced a significantly larger lesion volume (p < 0.01). For in vivo models, 50 W/5 s ablation lesions yielded similar volumes but significantly less depth than 20 W/30 s ablation lesions. Peak temperatures were not significantly different at 2 and 4 mm with 50 W/5 s versus 20 W/30 s. CONCLUSIONS: Varying power and duration will confer different ablation lesion characteristics that can be tailored according to the substrate/anatomy that is being ablated. This phenomenon has important implications during catheter ablation.

Repeat ablation of refractory ventricular arrhythmias in patients with nonischemic cardiomyopathy: Impact of midmyocardial substrate and role of adjunctive ablation techniques.

INTRODUCTION: Multiple ablations are often necessary to manage ventricular arrhythmias (VAs) in nonischemic cardiomyopathy (NICM) patients. We assessed characteristics and outcomes and role of adjunctive, nonstandard ablation in repeat VA ablation (RAbl) in NICM. METHODS AND RESULTS: Consecutive NICM patients undergoing RAbl were analyzed, with characteristics of the last VA ablations compared between those undergoing 1 versus multiple-repeat ablations (1-RAbl vs. >1RAbl), and between those with or without midmyocardial substrate (MMS). VA-free survival was compared. Eighty-eight patients underwent 124 RAbl, 26 with > 1RAbl, and 26 with MMS. 1-RAbl and > 1-RAbl groups were similar in age (57 ± 16 vs. 57 ± 17 years; P = 0.92), males (76% vs. 69%; P = 0.60), LVEF (40 ± 17% vs. 40 ± 18%; P = 0.96), and amiodarone use (31% vs. 46%, P = 0.22). One-year VA freedom between 1-RAbl vs. > 1RAbl was similar (82% vs. 80%; P = 0.81); adjunctive ablation was utilized more in >1RAbl (31% vs. 11%, P = 0.02), and complication rates were higher (27% vs. 7%, P = 0.01), most due to septal substrate and anticipated heart block. >1-RAbl patients had more MMS (62% vs. 16%, P < 0.01). Although MMS was associated with worse VA-free survival after 1-RAbl (43% vs. 69%, P = 0.01), when >1RAbl was performed, more often with nonstandard ablation, VA-free survival was comparable to non-MMS patients (85% vs. 81%; P = 0.69). More RAbls were required in MMS versus non-MMS patients (2.00 ± 0.98 vs. 1.16 ± 0.37; P < 0.001). CONCLUSION: For NICM patients with recurrent, refractory VAs despite previous ablation, effective arrhythmia control can safely be achieved with subsequent ablation, although >1 repeat procedure with adjunctive ablation is often required, especially with MMS.