Identification of Human Ventricular Tachycardia Demarcated by Fixed Lines of Conduction Block in a 3-Dimensional Hyperboloid Circuit.

BACKGROUND: The circuit boundaries for reentrant ventricular tachycardia (VT) have been historically conceptualized within a 2-dimensional (2D) construct, with their fixed or functional nature unresolved. This study aimed to examine the correlation between localized lines of conduction block (LOB) evident during baseline rhythm with lateral isthmus boundaries that 3-dimensionally constrain the VT isthmus as a hyperboloid structure. METHODS: A total of 175 VT activation maps were correlated with isochronal late activation maps during baseline rhythm in 106 patients who underwent catheter ablation for scar-related VT from 3 centers (42% nonischemic cardiomyopathy). An overt LOB was defined by a deceleration zone with split potentials (≥20 ms isoelectric segment) during baseline rhythm. A novel application of pacing within deceleration zone (≥600 ms) was implemented to unmask a concealed LOB not evident during baseline rhythm. LOB identified during baseline rhythm or pacing were correlated with isthmus boundaries during VT. RESULTS: Among 202 deceleration zones analyzed during baseline rhythm, an overt LOB was evident in 47%. When differential pacing was performed in 38 deceleration zones without overt LOB, an underlying concealed LOB was exposed in 84%. In 152 VT activation maps (2D=53, 3-dimensional [3D]=99), 69% of lateral boundaries colocalized with an LOB in 2D activation patterns, and the depth boundary during 3D VT colocalized with an LOB in 79%. In VT circuits with isthmus regions that colocalized with a U-shaped LOB (n=28), the boundary invariably served as both lateral boundaries in 2D and 3D. Overall, 74% of isthmus boundaries were identifiable as fixed LOB during baseline rhythm or differential pacing. CONCLUSIONS: The majority of VT circuit boundaries can be identified as fixed LOB from intrinsic or paced activation during sinus rhythm. Analysis of activation while pacing within the scar substrate is a novel technique that may unmask concealed LOB, previously interpreted to be functional in nature. An LOB from the perspective of a myocardial surface is frequently associated with intramural conduction, supporting the existence of a 3D hyperboloid VT circuit structure. Catheter ablation may be simplified to targeting both sides around an identified LOB during sinus rhythm.

Circuit Determinants of Ventricular Tachycardia Cycle Length: Characterization of Fast and Unstable Human Ventricular Tachycardia.

BACKGROUND: Fast ventricular tachycardias (VTs) have historically been attributed to shorter path lengths with smaller reentrant circuit dimensions in animal models. The relationship between the dimensions of the reentrant VT circuit and tachycardia cycle length (TCL) has not been examined in humans. This study aimed to analyze the determinants of the rate of human VT with comparison of circuit dimensions and conduction velocity (CV) across a wide range of both stable and unstable VTs delineated by high-resolution mapping. METHODS: Fifty-four VTs with complete circuit delineation (>90% TCL) by high-resolution multielectrode mapping were analyzed in 49 patients (men, 88%; age, 65 years [58-71 years]; nonischemic, 47%). Fast VT was defined as TCL <333 milliseconds (rate >180 bpm). Unstable VT was defined by hemodynamic deterioration with an intrinsic mean arterial pressure <60 mm Hg during a sustained episode. RESULTS: The median TCL of VT was 365 milliseconds (306-443 milliseconds), and 24 fast VTs were characterized. A wide range of CVs was observed within the entrance (0.03-0.55 m/s), common pathway (0.03-0.77 m/s), exit (0.03-0.53 m/s), and outer loop (0.17-1.13 m/s). There were no significant differences in the median dimensions of the isthmus and path length between fast and slow VTs and between unstable and stable VTs. The outer loop CV was the only circuit component that correlated with TCL in both ischemic cardiomyopathy (r=-0.5, P=0.006) and nonischemic cardiomyopathy (r=-0.45, P=0.028). The duration of the longest diastolic electrogram was inversely correlated with the dimensions of common pathway (length: r=-0.46, P=0.001, width: r=-0.3, P=0.047) and predictive of rapid VT termination by a single radiofrequency application (r=-0.41, P=0.023). CONCLUSIONS: Because of a wide spectrum of CV observed within the reentrant path during human VT, the dimensions of the circuit were not predictive of VT cycle length. For the first time, we demonstrate that the CV of the outer loop, rather than isthmus, is the principal determinant of the rate of VT. The size of the circuit was similar between fast and slow VTs and between unstable and stable VTs. Long, continuous electrograms were indicative of spatially confined isthmus dimensions, confirmed by rapid termination of VT during radiofrequency delivery.

Atypical pathogens associated with cardiac implantable electronic device infections.

BACKGROUND: Cardiovascular implantable electronic device (CIED) infections are associated with significant morbidity and mortality making the identification of the causative organism critical. The vast majority of CIED infections are caused by Staphylococcal species. CIED infections associated with atypical pathogens are rare and have not been systematically investigated. The objective of this study is to characterize the clinical course, management and outcome in patients with CIED infection secondary to atypical pathogens. METHODS: Medical records of all patients who underwent CIED system extraction at the University of Chicago Medical Center between January 2010 and November 2020 were retrospectively reviewed to identify patients with CIED infection. Demographic, clinical, infection-related and outcome data were collected. CIED infections were divided into typical and atypical groups based on the pathogens isolated. RESULTS: Among 356 CIED extraction procedures, 130 (37%) were performed for CIED infection. Atypical pathogens were found in 5.4% (n = 7) and included Pantoea species (n = 2), Kocuria species (n = 1), Cutibacterium acnes (n = 1), Corynebacterium tuberculostearicum (n = 1), Corynebacterium striatum (n = 1), Stenotrophomonas maltophilia (n = 1), and Pseudozyma ahidis (n = 1). All patients with atypical CIED infections were successfully treated with total system removal and tailored antibiotic therapy. There were no infection-related deaths. CONCLUSIONS: CIED infections with atypical pathogens were rare and associated with good outcome if diagnosed early and treated with total system removal and tailored antimicrobial therapy. Atypical pathogens cultured from blood, tissue or hardware in patients with CIED infection should be considered pathogens and not contaminants.

Late presentation of recurrent syncope after permanent pacemaker implantation due to Lead-Header malapposition.

Permanent pacemaker (PPM) malfunction due to electrical connection problems such as a loose set screw or lead-header malapposition is extremely rare. We present a patient with complete heart block (CHB) who had PPM malfunction and recurrent syncope, late (14 months) after initial implantation, which was caused by the ventricular lead pin disengagement from the header resulting in oversensing due to noise, pacing inhibition and recurrent syncope. PPM due to lead-header malapposition this late after device implantation has previously not been reported.

Targeted Ablation of Ventricular Tachycardia Guided by Wavefront Discontinuities During Sinus Rhythm: A New Functional Substrate Mapping Strategy.

BACKGROUND: Accurate and expedited identification of scar regions most prone to reentry is needed to guide ventricular tachycardia (VT) ablation. We aimed to prospectively assess outcomes of VT ablation guided primarily by the targeting of deceleration zones (DZ) identified by propagational analysis of ventricular activation during sinus rhythm. METHODS: Patients with scar-related VT were prospectively enrolled in the University of Chicago VT Ablation Registry between 2016 and 2018. Isochronal late activation maps annotated to the latest local electrogram deflection were created with high-density multielectrode mapping catheters. Targeted ablation of DZ (>3 isochrones within 1cm radius) was performed, prioritizing later activated regions with maximal isochronal crowding. When possible, activation mapping of VT was performed, and successful ablation sites were compared with DZ locations for mechanistic correlation. Patients were prospectively followed for VT recurrence and mortality. RESULTS: One hundred twenty patients (median age 65 years [59-71], 15% female, 50% nonischemic, median ejection fraction 31%) underwent 144 ablation procedures for scar-related VT. 57% of patients had previous ablation and epicardial access was employed in 59% of cases. High-density mapping during baseline rhythm was performed (2518 points [1615-3752] endocardial, 5049±2580 points epicardial) and identified an average of 2±1 DZ, which colocalized to successful termination sites in 95% of cases. The median total radiofrequency application duration was 29 min (21-38 min) to target DZ, representing ablation of 18% of the low-voltage area. At 12±10 months, 70% freedom from VT recurrence (80% in ischemic cardiomyopathy and 63% in nonischemic cardiomyopathy) was achieved. The overall survival rate was 87%. CONCLUSIONS: A novel voltage-independent high-density mapping display can identify the functional substrate for VT during sinus rhythm and guide targeted ablation, obviating the need for extensive radiofrequency delivery. Regions with isochronal crowding during the baseline rhythm were predictive of VT termination sites, providing mechanistic evidence that deceleration zones are highly arrhythmogenic, functioning as niduses for reentry.

Intracardiac Delineation of Septal Conduction in Left Bundle-Branch Block Patterns.

BACKGROUND: Septal activation in patients with left bundle-branch block (LBBB) patterns has not been described previously. We performed detailed intracardiac mapping of left septal conduction to assess for the presence and level of complete conduction block (CCB) in the His-Purkinje system. Response to His bundle pacing was assessed in patients with and without CCB in the left bundle. METHODS: Left septal mapping was performed with a linear multielectrode catheter in consecutive patients with LBBB pattern referred for device implantation (n=38) or substrate mapping (n=47). QRS width, His duration, His-ventricular (HV) intervals, and septal conduction patterns were analyzed. The site of CCB was localized to the level of the left-sided His fibers (left intrahisian) or left bundle branch. Patients with ventricular activation preceded by Purkinje potentials were categorized as having intact Purkinje activation. RESULTS: A total of 88 left septal conduction recordings were analyzed in 85 patients: 72 LBBB block pattern and 16 controls (narrow QRS, n=11; right bundle-branch block, n=5). Among patients with LBB block pattern, CCB within the proximal left conduction system was observed in 64% (n=46) and intact Purkinje activation in the remaining 36% (n=26). Intact Purkinje activation was observed in all controls. The site of block in patients with CCB was at the level of the left His bundle in 72% and in the proximal left bundle branch in 28%. His bundle pacing corrected wide QRS in 54% of all patients with LBBB pattern and 85% of those with CCB (94% left intrahisian, 62% proximal left bundle-branch). No patients with intact Purkinje activation demonstrated correction of QRS with His bundle pacing. CCB showed better predictive value (positive predictive value 85%, negative predictive value 100%, sensitivity 100%) than surface ECG criteria for correction with His bundle pacing. CONCLUSIONS: Heterogeneous septal conduction was observed in patients with surface LBBB pattern, ranging from no discrete block to CCB. When block was present, we observed pathology localized within the left-sided His fibers (left intrahisian block), which was most amenable to corrective His bundle pacing by recruitment of latent Purkinje fibers. ECG criteria for LBBB incompletely predicted CCB, and intracardiac data might be useful in refining patient selection for resynchronization therapy.

Ventricular arrhythmia suppression with ivabradine in a patient with catecholaminergic polymorphic ventricular tachycardia refractory to nadolol, flecainide, and sympathectomy.

Conventional treatment strategies for catecholaminergic polymorphic ventricular tachycardia (CPVT) include avoidance of strenuous exercise and competitive sports, drugs such as ß-blockers and flecainide and, cervical sympathectomy. An implantable cardioverter-defibrillator (ICD) has been utilized if the response to these strategies is inadequate; however, ICD use in CPVT patients, in addition to usual complications, is associated with an increased risk of life-threatening electrical storm. Ivabradine is a selective inhibitor of hyperpolarization-activated cyclic nucleotide-gated potassium channel 4 generated funny current (If ), which has been shown to be efficacious in suppression of inappropriate sinus tachycardia, junctional tachycardia, atrial tachycardia, and ventricular ectopy in humans. We report an 18-year-old male with a severe CPVT phenotype refractory to flecainide, nadolol, and sympathectomy who exhibited suppression of ventricular arrhythmias after initiation of ivabradine. These findings are of importance as ivabradine could be an important add-on therapy in CPVT patients who are drug refractory or are unable to continue conventional therapies at the recommended doses.

Single-center experience of the FIRM technique to ablate paroxysmal and persistent atrial fibrillation.

INTRODUCTION: Focal impulse and rotor modulation (FIRM)-guided ablation has had mixed results of published success, and most studies have had a follow-up for a year or less. We aimed to study a consecutive group of patients followed for at least 1.5 years, subgrouped into those with an initial FIRM ablation and those with a previous, failed ablation who now received a FIRM guided one, to evaluate for success in each group and factors that might affect success. METHODS: Of 181 patients, 167 were available for analysis. Group 1 (n = 122) had a first or primary ablation (paroxysmal atrial fibrillation [PAF] 51; persistent atrial fibrillation [PeAF] 71) and group 2 (n = 45) had a redo ablation (PAF 18; PeAF 27). All patients were done under general anesthesia. FIRM mapping was done in the right atrium first and then the left, and only rotors consistently seen on multiple epochs were ablated, using 15 to 30 W. Rotor ablation was discontinued when remapping showed elimination of rotational activity at the site. Wide area catheter ablation was done for pulmonary vein isolation (PVI). Routine follow-up was at 3, 6, and 12 months of the first year, with a Holter monitor at 6 months, and then every 6 months thereafter. Event recorders were given to patients with potential arrhythmic symptoms. RESULTS: Mean follow-up was 16 months. Nearly 40% of patients had obstructive sleep apnea; mean body mass index was 32; and average left atrial size was 39.7 mm and 46.2 mm for PAF and PeAF patients, respectively. Freedom from atrial arrhythmia recurrence was: in group 1 patients, 82.4% for PAF and 67.6% for PeAF patients; in group 2 patients, 83.3% for PAF, but only 40.7% for PeAF patients. Comparing outcomes for the first 10 patients studied to the next 20 or more done by three operators showed no difference, suggesting no learning curve affecting the ablation results. Furthermore, the univariate analysis did not show any demographic factor to have an independent significance for ablation success or failure. Spontaneous termination during rotor ablation occurred in 76.8% of PAF and 27.6% of PeAF patients but did not affect the long-term outcomes for maintenance of sinus rhythm. CONCLUSIONS: FIRM-guided atrial ablation plus PVI in our patient population resulted in good success from a recurrence of atrial arrhythmias in patients undergoing an initial ablation procedure. For those with persistent AF undergoing a second procedure now using FIRM guidance plus PVI, the results are lower. Further research is needed to define better the appropriate population for FIRM-guided ablation and the degree of ablation needed for success in these patients.

A large deletion in RYR2 exon 3 is associated with nadolol and flecainide refractory catecholaminergic polymorphic ventricular tachycardia.

We report a 17-year-old boy with a large RYR2 exon 3 deletion who has a severe catecholaminergic polymorphic ventricular tachycardia (CPVT) phenotype characterized by refractoriness to both nadolol and flecainide which has previously not been reported in this subgroup of CPVT patients. Treatment options in a patient like ours are therefore limited and sympathectomy and implantable cardioverter-defibrillator implantation should be considered early in the treatment course as was done in this patient. In contrast to other CPVT patients who do not usually have structural cardiac abnormalities, these patients are at a high risk of developing left ventricular noncompaction or dilated cardiomyopathy and therefore might benefit from cardiac imaging at regular intervals.

Impact of high-grade atrioventricular block and cumulative frequent pacing on atrial arrhythmias.

BACKGROUND: The relationship between high-grade atrioventricular block (HGAVB) with cumulative frequent pacing and risk of atrial arrhythmias (AAs) has not been well characterized. We hypothesized HGAVB and pacing may have significant impact on incidence and prevalence of AAs by modulating atrial substrate. OBJECTIVE: To determine impact of HGAVB and pacing on AAs including atrial fibrillation (AF), atrial flutter (AFL), and atrial tachycardia (AT). METHODS: All consecutive patients who underwent dual-chamber pacemaker implantation for HGAVB from 2005 to 2011 at the University of Chicago were included. AAs and percent of pacing were detected through device interrogation. Patients' data were collected from electronic medical records and clinic visits. RESULTS: A total of 166 patients (mean age 71 ± 15 years; 54% female, 56% African American) were studied. AF was documented in 27% of patients before pacemaker implantation. During a mean 5.8 ± 2.2 years of follow-up, 47% had device-detected AF, 10% AFL, and 26% AT. New-onset AF was documented in 40 of the 122 patients without prior AF (33%). Continuous (≥ 99%) right ventricular pacing was associated with significantly decreased AF prevalence (34% vs 59%, P = 0.005), and correlated with lower incidence (26% vs 41%, P = 0.22). Pacing suppressed AF in 14% of patients with baseline AF; those patients had lower atrial pacing (3.2% vs 45%, P < 0.0001). Left atrial dilation was the only independent predictor of AF with frequent pacing (P = 0.009). CONCLUSIONS: HGAVB is associated with high incidence and prevalence of AAs with and without pacing. Cumulative frequent (≥99%) ventricular pacing reduces risk of AF in patients with HGAVB.

Impact of race and gender on clinical outcomes of catheter ablation in patients with atrial fibrillation.

BACKGROUND: Radiofrequency catheter ablation (CA) is an effective treatment of drug-refractory atrial fibrillation (AF). However, the efficacy of CA by race and gender has not been well characterized. We sought to determine the impact of ethnicity and gender on clinical outcome following CA in patients with AF. METHODS: Patients who underwent CA for AF from September 2013 to April 2016 were included in this study. Patients were identified retrospectively and followed prospectively. RESULTS: A total of 118 patients (15.3% black and 78.8% white, 33% female) comprised the cohort, with mean age at ablation 63.4 ± 10.4 years. Black patients were older at time of the procedure (65.4 vs 63.4 years old) and had more prevalent comorbidities, including hypertension (77.8% vs 63.4%), diabetes (33.3% vs 15.0%), chronic kidney disease (22.2% vs 7.5%), and lower left ventricular ejection fraction (51.8% vs 56.2%). Blacks also had significantly larger left atrial size (P  =  0.03). Late recurrence of AF was similar between blacks and whites (33.3% vs 34.4%, P  =  1) as well as between women and men (28.2% vs 36.7%, P  =  0.41). Early recurrence was predictive of late recurrence in men (P < 0.001) but not in women (P  =  0.48). Enlarged left atrium and early recurrence of AF were significant predictors for late recurrence of AF in the cohort. CONCLUSIONS: CA for AF is equally effective in black patients despite more prevalent comorbidity and increased left atrial size. Early recurrence of AF after CA was not predictive of late recurrence of AF in women but was in men.

A Revised Definition of Left Bundle Branch Block Using Time to Notch in Lead I.

Importance: Current left bundle branch block (LBBB) criteria are based on animal experiments or mathematical models of cardiac tissue conduction and may misclassify patients. Improved criteria would impact referral decisions and device type for cardiac resynchronization therapy. Objective: To develop a simple new criterion for LBBB based on electrophysiological studies of human patients, and then to validate this criterion in an independent population. Design, Setting, and Participants: In this diagnostic study, the derivation cohort was from a single-center, prospective study of patients undergoing electrophysiological study from March 2016 through November 2019. The validation cohort was assembled by retrospectively reviewing medical records for patients from the same center who underwent transcatheter aortic valve replacement (TAVR) from October 2015 through May 2022. Exposures: Patients were classified as having LBBB or intraventricular conduction delay (IVCD) as assessed by intracardiac recording. Main Outcomes and Measures: Sensitivity and specificity of the electrocardiography (ECG) criteria assessed in patients with LBBB or IVCD. Results: A total of 75 patients (median [IQR] age, 63 [53-70.5] years; 21 [28.0%] female) with baseline LBBB on 12-lead ECG underwent intracardiac recording of the left ventricular septum: 48 demonstrated complete conduction block (CCB) and 27 demonstrated intact Purkinje activation (IPA). Analysis of surface ECGs revealed that late notches in the QRS complexes of lateral leads were associated with CCB (40 of 48 patients [83.3%] with CCB vs 13 of 27 patients [48.1%] with IPA had a notch or slur in lead I; P = .003). Receiver operating characteristic curves for all septal and lateral leads were constructed, and lead I displayed the best performance with a time to notch longer than 75 milliseconds. Used in conjunction with the criteria for LBBB from the American College of Cardiology/American Heart Association/Heart Rhythm Society, this criterion had a sensitivity of 71% (95% CI, 56%-83%) and specificity of 74% (95% CI, 54%-89%) in the derivation population, contrasting with a sensitivity of 96% (95% CI, 86%-99%) and specificity of 33% (95% CI, 17%-54%) for the Strauss criteria. In an independent validation cohort of 46 patients (median [IQR] age, 78.5 [70-84] years; 21 [45.7%] female) undergoing TAVR with interval development of new LBBB, the time-to-notch criterion demonstrated a sensitivity of 87% (95% CI, 74%-95%). In the subset of 10 patients with preprocedural IVCD, the criterion correctly distinguished IVCD from LBBB in all cases. Application of the Strauss criteria performed similarly in the validation cohort. Conclusions and Relevance: The findings suggest that time to notch longer than 75 milliseconds in lead I is a simple ECG criterion that, when used in conjunction with standard LBBB criteria, may improve specificity for identifying patients with LBBB from conduction block. This may help inform patient selection for cardiac resynchronization or conduction system pacing.

Vasovagal Responses to Human Monomorphic Ventricular Tachycardia: Hemodynamic Implications From Sinus Rate Analysis.

BACKGROUND: Factors determining hemodynamic stability during human ventricular tachycardia (VT) are incompletely understood. OBJECTIVES: The purposes of this study were to characterize sinus rate (SR) responses during monomorphic VT in association with hemodynamic stability and to prospectively assess the effects of vagolytic therapy on VT tolerance. METHODS: This is a retrospective analysis of patients undergoing scar-related VT ablation. Vasovagal responses were evaluated by analyzing sinus cycle length before VT induction and during VT. SR responses were classified into 3 groups: increasing (≥5 beats/min, sympathetic), decreasing (≥5 beats/min, vagal), and unchanged, with the latter 2 categorized as inappropriate SR. In a prospective cohort (n = 30) that exhibited a failure to increase SR, atropine was administered to improve hemodynamic tolerance to VT. RESULTS: In 150 patients, 261 VT episodes were analyzed (29% untolerated, 71% tolerated) with median VT duration 1.6 minutes. A total of 52% of VT episodes were associated with a sympathetic response, 31% had unchanged SR, and 17% of VTs exhibited a vagal response. A significantly higher prevalence of inappropriate SR responses was observed during untolerated VT (sustained VT requiring cardioversion within 150 seconds) compared with tolerated VT (84% vs 34%; P < 0.001). Untolerated VT was significantly different between groups: 9% (sympathetic), 82% (vagal), and 32% (unchanged) (P < 0.001). Atropine administration improved hemodynamic tolerance to VT in 70%. CONCLUSIONS: Nearly one-half of VT episodes are associated with failure to augment SR, indicative of an under-recognized pathophysiological vasovagal response to VT. Inappropriate SR responses were more predictive of hemodynamic instability than VT rate and ejection fraction. Vagolytic therapy may be a novel method to augment blood pressure during VT.

Oseltamivir overuse at a Chicago hospital during the 2009 influenza pandemic and the poor predictive value of influenza-like illness criteria.

We report on the overuse of oseltamivir at Rush University Medical Center, Chicago during the 2009 H1N1 influenza pandemic. Of 210 patients with suspected influenza who underwent respiratory virus reverse transcription polymerase chain reaction (RT-PCR) testing, 113 (54%) received empiric oseltamivir therapy. However, only 50 treated patients (44%) had laboratory confirmed 2009 H1N1. Factors associated with oseltamivir use included a younger median age (including age < 5 y), subjective fever, cough, rhinorrhea, myalgias, higher median temperature, and fulfilment of the US Centers For Disease Control and Prevention (CDC) influenza-like illness (ILI) criteria. However, on multivariate analysis, only subjective fever (p = 0.006, odds ratio (OR) 3.1, 95% confidence interval (CI) 1.4-6.7) and fulfilment of CDC ILI criteria (p = 0.001, OR 3.6, 95% CI 1.7-7.5) were significantly associated with the receipt of oseltamivir. The CDC ILI criteria had a poor positive predictive value of 43% (95% CI 33.3-53.3) for 2009 H1N1. While the ILI criteria are a useful epidemiologic tool, it is too imprecise for direct patient care.

Empiric ablation of polymorphic ventricular tachycardia/fibrillation in the absence of a mappable trigger: Prospective feasibility and efficacy of pacemap matching to defibrillator electrograms.

BACKGROUND: Catheter ablation strategies for ventricular fibrillation (VF) and polymorphic ventricular tachycardia (PMVT) are not established when spontaneous triggers are rare or absent. OBJECTIVE: The purpose of this study was to report the feasibility and efficacy of a novel empiric ablation strategy of pacemapping to stored implantable cardioverter-defibrillator (ICD) template electrograms (SITE) of the clinical premature ventricular contraction (PVC) trigger. METHODS: Fifteen patients with drug-refractory VF/PMVT receiving defibrillator shocks without identifiable and mappable PVC triggers were prospectively analyzed. The protocol incorporated systematic pacemapping from known arrhythmogenic sites (moderator band/right ventricular [RV] papillary muscles, left conduction system/Purkinje network, outflow tracts) with real-time comparison between the paced ICD electrogram (EGM) morphology and SITE. RESULTS: Regions within the left Purkinje network yielded the best pacemap match for the SITE of the clinical PVC trigger in 55% of ablation targets (left posterior fascicle 6, left septal fascicle 1, left anterior fascicle 5), followed by the RV moderator band region in 14% (n = 3), RV papillary muscles in 13% (n = 3), periaortic region in 14% (n = 3), and left ventricular anterolateral papillary muscle in 4% (n = 1). Freedom from ICD therapies off antiarrhythmic drug (AAD) was 64% at 6 months and 48% at 12 months. Shock burden was reduced from 4 (2-6) to 0 (0-1) (P = .001), and use of AADs was reduced from 2 (1-2) to 0 (0-1) (P = .001). CONCLUSION: In the absence of a mappable trigger, an empiric strategy of interrogating the Purkinje network, papillary muscles, and outflow tract regions by pacemap matching with SITE of the clinical PVC is feasible to guide ablation. A significant reduction in VF/PMVT therapy burden and AAD utilization was observed after a single procedure.

Population-Level Impact of the Guidelines Update on Patient Selection and Outcomes After Cardiac Resynchronization Therapy.

OBJECTIVES: This study sought to analyze the impact of the American College of Cardiology, American Heart Association, and Heart Rhythm Society (ACC/AHA/HRS) guidelines for cardiac resynchronization therapy with defibrillator (CRT-D) update on utilization and efficacy of CRT-D. BACKGROUND: In September 2012, the ACC/AHA/HRS guidelines for CRT-D were modified to include left bundle branch block (LBBB) as a Class I indication. METHODS: The IBM Watson MarketScan Database was queried between January 1, 2003, and December 31, 2018, for CRT-D implants or upgrades. The primary outcome was heart failure (HF) hospitalization following left ventricular lead implant. Secondary outcomes included all-cause mortality and device-related lead revision. RESULTS: A total of 27,238 patients were analyzed: 18,384 pre-update and 8,854 post-update. Mean age was 69 ± 11 years, 73% men, and 98% with history of HF hospitalization. The proportion of patients with LBBB increased from 29% to 55% (P < 0.001) after the update. Patients receiving CRT-D post-update demonstrated a greater prevalence of comorbidities, including atrial fibrillation (47% vs 40%; P < 0.001), diabetes mellitus (45% vs 39%; P < 0.001), chronic kidney disease (24% vs 15%; P < 0.001), and HF hospitalization in the year before CRT-D (40% vs 37%; P < 0.001). Despite greater baseline comorbidities, HF hospitalization significantly declined post-update (HR: 0.89; P < 0.001). Multivariate predictors of reduced HF hospitalization included angiotensin receptor neprilysin inhibitor prescription (HR: 0.48; P < 0.001) and presence of LBBB (HR: 0.71; P < 0.001). All-cause mortality was not significantly different between the 2 groups, and fewer lead revisions were noted post-update (0.6% vs 1.7%; P < 0.001). CONCLUSIONS: The revised 2012 guidelines led to an increased proportion of LBBB patients receiving CRT-D at the population-level. This change was associated with reduced HF hospitalization, despite broadening therapy to patients with more comorbid conditions.

Patient Profiles in the Utilization of the CanGaroo® Envelope.

Background The CanGaroo® Envelope (Aziyo Biologics, Silver Spring, MD) is intended to securely hold a cardiovascular implantable electronic device (CIED) to create a stable environment when implanted in the body. Data on the utilization of this newly available product are limited. Objective In this study, our objective was to describe the specific profiles of patients who may benefit from the use of the CanGaroo® Envelope at the time of CIED implantation. Methods  The utilization of the CanGaroo® Envelope was assessed from January 2019 to October 2019 among a series of patients who were either undergoing de-novo CIED implantation or replacement. Results Among a total of 50 patients, the CanGaroo® Envelope was utilized in 15 (30%). Three distinct patient profiles were identified: profile 1: elderly patients with poor tissue turgor at risk of wound dehiscence or erosion; profile 2: patients with a history of previous device infection; and profile 3: patients at high risk of device infection having one or more of the following risk factors - chronic kidney disease, immunocompromised state, or diabetes mellitus. At a mean follow-up of 18 ±3 months, no CIED pocket erosion, dehiscence, or infection was noted. Conclusions Three distinct profiles of patients who could potentially benefit from the use of the CanGaroo® Envelope were identified by the implanting physicians. Long-term follow-up data, including infection and wound dehiscence rates, are necessary to further analyze the optimal utilization of the device.

Double loop ventricular tachycardia activation patterns with single loop mechanisms: Asymmetric entrainment responses during "pseudo-figure-of-eight" reentry.

BACKGROUND: The classical paradigm of scar-related reentrant ventricular tachycardia (VT) features a circuit with a double loop figure-of-eight (F8) activation pattern. OBJECTIVE: The purpose of this study was to interrogate VT circuits with F8 activation patterns by entrainment mapping to differentiate an active loop from a passive loop. METHODS: Sixty VT circuits with >90% of tachycardia cycle length delineated in high resolution were retrospectively analyzed in 55 patients (nonischemic 49%). A pseudo-F8 VT circuit was defined as a double loop activation pattern driven by a single loop mechanism with a passive loop that yields a long postpacing interval (postpacing interval - tachycardia cycle length ≥ 30 ms). RESULTS: Single loop activation patterns were observed in 33% (n = 20). Of 40 circuits with F8 patterns by activation mapping, 20 were studied with entrainment mapping, where a passive loop was identified by a long postpacing interval in 50%. In 6 circuits where entrainment mapping was performed from both outer loop regions, all demonstrated asymmetric responses to entrainment, confirming a single loop mechanism. Entrainment from both lateral margins of the common pathway (n = 7) demonstrated an asymmetric response in 29%. In all pseudo-F8 circuits (n = 10), the shorter loop functioned as the active loop and ablation targeting the active loop side of the isthmus resulted in VT termination with a single radiofrequency application. CONCLUSION: In a selected cohort, single loop mechanisms are more prevalent than double loop reentry in reentrant human VT. Half of VT circuits with double loop activation patterns can be demonstrated to be sustained by a single active loop mechanism by entrainment mapping. Ablation targeting the shorter active loop resulted in rapid termination during radiofrequency application.

Impact of physiological pacing on functional mitral regurgitation in systolic dysfunction: Initial echocardiographic remodeling findings after His bundle pacing.

BACKGROUND: Although His bundle pacing (HBP) has been shown to improve left ventricular ejection fraction (LVEF), its impact on mitral regurgitation (MR) remains uncertain. OBJECTIVES: The aim of this study was to evaluate change in functional MR after HBP in patients with left ventricular (LV) systolic dysfunction. METHODS: Paired echocardiograms were retrospectively assessed in patients with reduced LVEF (<50%) undergoing HBP for pacing or resynchronization. The primary outcomes assessed were change in MR, LVEF, LV volumes, and valve geometry pre- and post-HBP. MR reduction was characterized as a decline in ≥1 MR grade post-HBP in patients with ≥grade 3 MR at baseline. RESULTS: Thirty patients were analyzed: age 68 ± 15 years, 73% male, LVEF 32% ± 10%, 38% coronary artery disease, 33% history of atrial fibrillation. Baseline QRS was 162 ± 31 ms: 33% left bundle branch block, 37% right bundle branch block, 17% paced, and 13% narrow QRS. Significant reductions in LV end-systolic volume (122 mL [73-152 mL] to 89 mL [71-122 mL], P = .006) and increase in LV ejection fraction (31% [25%-37%] to 39% [30%-49%], P < .001) were observed after HBP. Ten patients had grade 3 or 4 MR at baseline, with reduction in MR observed in 7. In patients with at least grade 3 MR at baseline, reduction in LV volumes, improved mitral valve geometry, and greater LV contractility were associated with MR reduction. Greater reduction in paced QRS width was present in MR responders compared to non-MR responders (-40% vs -25%, P = .04). CONCLUSIONS: In this initial detailed echocardiographic analysis in patients with LV systolic dysfunction, HBP reduced functional MR through favorable ventricular remodeling.