Septal Venous Channel Perforation during Left Bundle Branch Area Pacing: A Prospective Study.

OBJECTIVES: To characterize the diagnosis, frequency, and procedural implications of septal venous channel perforation during left bundle branch area pacing (LBBAP). METHODS: All consecutive patients undergoing LBBAP over an 8-month period were prospectively studied. During lead placement, obligatory septal contrast injection was performed twice, at initiation (implant entry zone) and completion (fixation zone). An intuitive fluoroscopic schema using orthogonal views (LAO/RAO) and familiar landmarks is described. Using this, we resolved zonal distribution (I-VI) of lead position on the ventricular septum and its angulation (post-fixation angle θ). Subjects with/without septal venous channel perforation were compared. RESULTS: Sixty-one-patients [Male 57.3%, Median Age (IQR) 69.5(62.5-74.5) years] were enrolled. Septal venous channel perforation was observed in 8 (13.1%) patients [Male 28.5%, Median Age (IQR) 64(50-75) years]. They had higher frequency of, i) right-sided-implant (25% vs. 1.9%, p = 0.04), ii) fixation in zone III at the mid-superior septum (75% vs 28.3%, p = 0.04), iii) steeper angle of fixation- median θ (IQR) [19(10-30)° vs. 5(4-19)°, p = 0.01), and iv) longer median penetrated-lead-length (IQR) [13(10-14.8) vs. 10(8.5-12.5)mm, p = 0.03]. Coronary sinus drainage of contrast was noted in 5 (62.5%) patients. Abnormal impedance drops during implantation (12.5% vs. 5.7%, p = NS) were not significantly different. CONCLUSION: When evaluated systematically, septal venous channel perforation may be encountered commonly after LBBAP. The fiducial reference framework described using fluoroscopic imaging identified salient associated findings. This may be addressed with lead repositioning to a more inferior location and are not associated with adverse consequence acutely or in early follow-up.

Inadvertent septal perforation during conduction system pacing device implant: a case report.

Background: There has been recent growing interest in the use of conduction system pacing (CSP) for both bradycardia and heart failure indications. There remains a paucity of data, however, regarding complications related to the intraventricular septum associated with CSP implant and the management of these events. Case summary: We present a case of a patient with non-ischemic dilated cardiomyopathy presenting for cardiac resynchronization therapy in whom left bundle branch area pacing was complicated with interventricular septal perforation and managed intra-procedurally with repositioning of the lead to provide His bundle pacing (HBP) for QRS correction of underlying left bundle branch block. Post-procedure echocardiography did not show persistent ventricular septal defect. Left ventricular ejection fraction improved from 13% four months before implant to 30% at 32 months post-implant. Corrective HBP pacing thresholds showed a rise at 3-year follow-up. Discussion: Interventricular septal perforation during CSP is a possible complication during lead fixation. Pre-operative septal assessment with imaging can be helpful to provide important septal anatomical features. Septal perforation can be managed appropriately with lead repositioning intra-procedurally and close follow-up.

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.

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.

Postapproval Study of a Subcutaneous Implantable Cardioverter-Defibrillator System.

BACKGROUND: The subcutaneous implantable cardioverter-defibrillator (S-ICD) was developed to avoid complications related to transvenous implantable cardioverter-defibrillator (TV-ICD) leads. Device safety and efficacy were demonstrated previously with atypical clinical patients or limited follow-up. OBJECTIVES: The S-ICD PAS (Subcutaneous Implantable Cardioverter-Defibrillator System Post Approval Study) is a real-world, multicenter, registry of U.S. centers that was designed to assess long-term S-ICD safety and efficacy in a diverse group of patients and implantation centers. METHODS: Patients were enrolled in 86 U.S. centers with standard S-ICD indications and were observed for up to 5 years. Efficacy endpoints were first and final shock efficacy. Safety endpoints were complications directly related to the S-ICD system or implantation procedure. Endpoints were assessed using prespecified performance goals. RESULTS: A total of 1,643 patients were prospectively enrolled, with a median follow-up of 4.2 years. All prespecified safety and efficacy endpoint goals were met. Shock efficacy rates for discrete episodes of ventricular tachycardia or ventricular fibrillation were 98.4%, and they did not differ significantly across follow-up years (P = 0.68). S-ICD-related and electrode-related complication-free rates were 93.4% and 99.3%, respectively. Only 1.6% of patients had their devices replaced by a TV-ICD for a pacing need. Cumulative all-cause mortality was 21.7%. CONCLUSIONS: In the largest prospective study of the S-ICD to date, all study endpoints were met, despite a cohort with more comorbidities than in most previous trials. Complication rates were low and shock efficacy was high. These results demonstrate the 5-year S-ICD safety and efficacy for a large, diverse cohort of S-ICD recipients. (Subcutaneous Implantable Cardioverter-Defibrillator [S-ICD] System Post Approval Study [PAS]; NCT01736618).

Left Bundle Branch Block: Characterization, Definitions, and Recent Insights into Conduction System Physiology.

Left bundle branch block (LBBB) is not just a simple electrocardiogram alteration. The intricacies of this general terminology go beyond simple conduction block. This review puts together current knowledge on the historical concept of LBBB, clinical significance, and recent insights into the pathophysiology of human LBBB. LBBB is an entity that affects patient diagnosis (primary conduction disease, secondary to underlying pathology or iatrogenic), treatment (cardiac resynchronization therapy or conduction system pacing for heart failure), and prognosis. Recruiting the left bundle branch with conduction system pacing depends on the complex interaction between anatomy, site of pathophysiology, and delivery tools.

Predicting Malignant Ventricular Arrhythmias Using Real-Time Remote Monitoring.

BACKGROUND: Although implantable cardioverter-defibrillator (ICD) therapies are associated with increased morbidity and mortality, the prediction of malignant ventricular arrhythmias has remained elusive. OBJECTIVES: The purpose of this study was to evaluate whether daily remote-monitoring data may predict appropriate ICD therapies for ventricular tachycardia or ventricular fibrillation. METHODS: This was a post hoc analysis of IMPACT (Randomized trial of atrial arrhythmia monitoring to guide anticoagulation in patients with implanted defibrillator and cardiac resynchronization devices), a multicenter, randomized, controlled trial of 2,718 patients evaluating atrial tachyarrhythmias and anticoagulation for patients with heart failure and ICD or cardiac resynchronization therapy with defibrillator devices. All device therapies were adjudicated as either appropriate (to treat ventricular tachycardia or ventricular fibrillation) or inappropriate (all others). Remote monitoring data in the 30 days before device therapy were utilized to develop separate multivariable logistic regression and neural network models to predict appropriate device therapies. RESULTS: A total of 59,807 device transmissions were available for 2,413 patients (age 64 ± 11 years, 26% women, 64% ICD). Appropriate device therapies (141 shocks, 10 antitachycardia pacing) were delivered to 151 patients. Logistic regression identified shock lead impedance and ventricular ectopy as significantly associated with increased risk of appropriate device therapy (sensitivity 39%, specificity 91%, AUC: 0.72). Neural network modeling yielded significantly better (P < 0.01 for comparison) predictive performance (sensitivity 54%, specificity 96%, AUC: 0.90), and also identified patterns of change in atrial lead impedance, mean heart rate, and patient activity as predictors of appropriate therapies. CONCLUSIONS: Daily remote monitoring data may be utilized to predict malignant ventricular arrhythmias in the 30 days before device therapies. Neural networks complement and enhance conventional approaches to risk stratification.

Impact of race on outcomes from catheter ablation of ventricular tachycardia in structural heart disease: A prospective registry from south metropolitan Chicago.

Background: Whether racial disparities in outcomes are present after catheter ablation for scar-related ventricular tachycardia (VT) is not known. Objective: The purpose of this study was to examine whether racial differences exist in outcomes for patients undergoing VT ablation. Methods: From March 2016 through April 2021, consecutive patients undergoing catheter ablation for scar-related VT at the University of Chicago were prospectively enrolled. The primary outcome was VT recurrence, with secondary outcome of mortality alone and composite endpoint of left ventricular assist device placement, heart transplant, or mortality. Results: A total of 258 patients were analyzed: 58 (22%) self-identified as Black, and 113 (44%) had ischemic cardiomyopathy. Black patients had significantly higher rates of hypertension (HTN), chronic kidney disease (CKD), and VT storm at presentation. At 7 months, Black patients experienced higher rates of VT recurrence (P = .009). However, after multivariable adjustment, there were no observed differences in VT recurrence (adjusted hazard ratio [aHR] 1.65; 95% confidence interval [CI] 0.91-2.97; P = .10), all-cause mortality (aHR 0.49; 95% CI 0.21-1.17; P = .11), or composite events (aHR 0.76; 95% CI 0.37-1.54; P = .44) between Black and non-Black patients. Conclusion: In this diverse prospective registry of patients undergoing catheter ablation for scar-related VT, Black patients experienced higher rates of VT recurrence compared to non-Black patients. When adjusted for highly prevalent HTN, CKD, and VT storm, Black patients had comparable outcomes as non-Black patients.

Cardiac resynchronization considerations in left bundle branch block.

Cardiac resynchronization therapy (CRT) via biventricular pacing (BiVP) is an established treatment for patients with left ventricular systolic heart failure and intraventricular conduction delay resulting in wide QRS. Seminal trials demonstrating mortality benefit from CRT were conducted in patients with wide left bundle branch block (LBBB) pattern on electrocardiogram (ECG) and evidence of clinical heart failure. The presence of conduction block was assumed to correlate with commonly applied criteria for LBBB. More recent data has challenged this assertion, revealing that LBBB pattern may include distinct underlying pathophysiology, including patients with complete conduction block, either at the left-sided His fibers or the proximal left bundle, intact Purkinje activation with wide LBBB-like QRS, and patients demonstrating both proximal block and distal delay. Currently, BiVP-CRT is indicated for all QRS duration ≥150 ms and may be considered for BBB patterns from 130 to 149 ms with robust clinical data to support its use. Despite this, however, there remains a significant number of non-responders to BVP. Conduction system pacing (CSP) has emerged as an alternative approach to deliver CRT and correct QRS in patients with conduction block. Newer hybrid approaches which combine CSP and traditional BiVP-CRT and may hold promise for patients with IP or mixed-level block. As various approaches to CRT continue to be studied, physiologic phenotyping of the LBBB pattern remains an important consideration.

Left bundle branch area pacing in patients with heart failure and right bundle branch block: Results from International LBBAP Collaborative-Study Group.

Background: Cardiac resynchronization therapy (CRT) using biventricular pacing has limited efficacy in patients with heart failure (HF) and right bundle branch block (RBBB). Left bundle branch area pacing (LBBAP) is a novel physiologic pacing option. Objective: The aim of the study was to assess the feasibility and outcomes of LBBAP in HF patients with RBBB and reduced left ventricular systolic function, and indication for CRT or ventricular pacing. Methods: LBBAP was attempted in patients with left ventricular ejection fraction (LVEF) <50%, RBBB, HF, and indications for CRT or ventricular pacing. Procedural, pacing, and electrocardiographic parameters; clinical response (no HF hospitalization and improvement in NYHA class); and echocardiographic response (≥5% increase in ejection fraction) to LBBAP were assessed. Results: LBBAP was attempted in 121 patients and successful in 107 (88%). Patient characteristics included age 74 ± 12 years, female 25%, ischemic cardiomyopathy 49%, and ejection fraction 35% ± 9%. QRS axis at baseline was normal in 24%, left axis 63%, right axis 13%. LBBAP threshold and R-wave amplitudes were 0.8 ± 0.3 V @ 0.5 ms and 10 ± 9 mV at implant and remained stable during mean follow-up of 13 ± 8 months. LBBAP resulted in narrowing of QRS duration (156 ± 20 ms to 150 ± 24 ms (P = .01) with R-wave peak times in V6 of 85 ± 16 ms. LVEF improved from 35% ± 9% to 43% ± 12% (P < .01). Clinical and echocardiographic response was observed in 60% and 61% of patients, respectively. Female sex and reduction in QRS duration with LBBAP were predictive of echocardiographic response and super-response. Conclusion: LBBAP is a feasible alternative to deliver CRT or physiologic ventricular pacing in patients with RBBB, HF, and LV dysfunction.

Device-related complications in subcutaneous versus transvenous ICD: a secondary analysis of the PRAETORIAN trial.

BACKGROUND: The subcutaneous implantable cardioverter-defibrillator (S-ICD) is developed to overcome lead-related complications and systemic infections, inherent to transvenous ICD (TV-ICD) therapy. The PRAETORIAN trial demonstrated that the S-ICD is non-inferior to the TV-ICD with regard to the combined primary endpoint of inappropriate shocks and complications. This prespecified secondary analysis evaluates all complications in the PRAETORIAN trial. METHODS AND RESULTS: The PRAETORIAN trial is an international, multicentre, randomized trial in which 849 patients with an indication for ICD therapy were randomized to receive an S- ICD (N = 426) or TV-ICD (N = 423) and followed for a median of 49 months. Endpoints were device-related complications, lead-related complications, systemic infections, and the need for invasive interventions. Thirty-six device-related complications occurred in 31 patients in the S-ICD group of which bleedings were the most frequent. In the TV-ICD group, 49 complications occurred in 44 patients of which lead dysfunction was most frequent (HR: 0.69; P = 0.11). In both groups, half of all complications were within 30 days after implantation. Lead-related complications and systemic infections occurred significantly less in the S-ICD group compared with the TV-ICD group (P < 0.001, P = 0.03, respectively). Significantly more complications required invasive interventions in the TV-ICD group compared with the S-ICD group (8.3% vs. 4.3%, HR: 0.59; P = 0.047). CONCLUSION: This secondary analysis shows that lead-related complications and systemic infections are more prevalent in the TV-ICD group compared with the S-ICD group. In addition, complications in the TV-ICD group were more severe as they required significantly more invasive interventions. This data contributes to shared decision-making in clinical practice.

What Intracardiac Tracings Have Taught Us About Left Bundle Branch Block.

Current electrocardiogram (ECG) criteria for left bundle branch block (LBBB) are largely based on early work in animal models or on mathematical models of cardiac activation. The resulting criteria have modest specificity, and up to one-third of patients who meet current ECG criteria for LBBB may have intact conduction through their His-Purkinje systems. Intracardiac tracings offer the ability to accurately discriminate between LBBB and other causes of delayed activation, which may facilitate the development of more accurate ECG criteria. Assessing these distinctions are particularly salient to applications for conduction system pacing.

Physiologic Pacing Targeting the His Bundle and Left Bundle Branch: a Review of the Literature.

PURPOSE OF REVIEW: Conduction system pacing (CSP) has emerged as a means to preserve or restore physiological ventricular activation via pacing at the His bundle or at more distal targets in the conduction system, including the left bundle branch area. This review examines strengths, weaknesses, and clinical applications of CSP performed via these approaches. RECENT FINDINGS: His bundle pacing (HBP) has been successfully utilized for standard bradyarrhythmia indications and for QRS correction among patients receiving devices for cardiac resynchronization therapy (CRT). Limitations of HBP pacing have included implant complexity and rising pacing thresholds over time. Left bundle branch area pacing (LBBAP) appears to deliver similar physiological benefits with shorter implant times and more stable thresholds. More recently, hybrid systems utilizing HBP or LBBAP in combination with left ventricular leads have been used to treat heart failure (HF) patients, and may be useful in multilevel or mixed conduction blocks. There is growing interest in CSP for bradycardia and HF indications, although high quality data with randomized controlled trials are needed to help guide future treatment paradigms.

Influence of Capture Selectivity and Left Intrahisian Block on QRS Characteristics During Left Bundle Branch Pacing.

OBJECTIVES: This study sought to examine QRS and intracardiac characteristics during selective (S) and nonselective (NS) left bundle branch pacing (LBBP) from direct left septal recordings. BACKGROUND: Criteria for S-LBBP and NS-LBBP have not been validated with intracardiac mapping. METHODS: Pacing was performed from multielectrode Purkinje recordings below the left-sided His. S-LBBP and NS-LBBP were performed in patients with narrow QRS (n = 9), right bundle branch block (n = 3), intraventricular conduction delay (n = 5), and left bundle branch block (n = 10). QRS duration was measured from stimulus onset (QRSst) and from the intrinsicoid deflection of the R-wave in V1-V2 (QRSid) to QRS end. Retrograde left bundle branch conduction was assessed by stimulus-to-retrograde His intervals. RESULTS: Among 27 patients analyzed, 20 demonstrated both NS- and S-LBBP and were studied in paired comparisons. NS-LBBP resulted in narrower QRS compared to S-LBBP (QRSst: 163 ms [interquartile range (IQR): 144-179 ms] vs 181 ms [IQR: 173-203 ms]; P < 0.001; QRSid: 125 ms [IQR: 117-142 ms] vs 150 ms [IQR: 135-157 ms]; P < 0.001). Left ventricular activation time was also significantly shorter for NS-LBBP compared to S-LBBP (88 ms [IQR: 75-111 ms] vs 97 ms [IQR: 82-123 ms]; P = 0.019). Left intrahisian block was bidirectional in 10 patients with long retrograde stimulus-to-His intervals. QRSst duration was significantly longer in patients with complete conduction block compared to those with intact Purkinje activation during NS-LBBP (181 ms [IQR: 162-195 ms] vs 157 ms [IQR: 139-168 ms]; P = 0.022). CONCLUSIONS: In contrast to His-bundle pacing, S-LBBP predominantly yields a wide QRS as a result of delayed RBB synchronization, whereas NS-LBBP results in shorter QRS duration because of recruitment of the basal right ventricular septum. A wider-paced morphology of LBBP was noted in patients with complete conduction block caused by bidirectional left intrahisian block. Achievement of narrow QRS during LBBP is predicated upon capture nonselectivity or programmed atrioventricular fusion, rather than intrinsic physiologic synchrony from left bundle branch stimulation.

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.

Bradyarrhythmias and Physiologic Pacing in the ICU.

Bradyarrhythmias represent a common pathology in the intensive care unit (ICU) with etiologies of varying severity. Treatment has often been focused on correcting underlying causes and may require pacing for urgent hemodynamic support. In recent years, there has been interest in physiologic pacing modalities which avoid the dyssynchrony from right ventricular (RV) only pacing. Cardiac resynchronization therapy (CRT) through biventricular pacing is a well-established device-based electrical therapy in patients with wide QRS and heart failure. Recently, it has been shown that biventricular pacing may also be pursued for hemodynamic rescue in the ICU setting. Efforts to re-engage the conduction system with His bundle pacing or further downstream have also emerged as alternative means to deliver resynchronization, with early applications in the ICU now being reported. The goal of the review is to examine bradyarrhythmia causes and management in the ICU as well as investigate new approaches in physiologic pacing and their potential roles in critically ill patients.

Implantation of cardiac electronic devices in active COVID-19 patients: Results from an international survey.

BACKGROUND: Cardiac implantable electronic device (CIED) implantation rates as well as the clinical and procedural characteristics and outcomes in patients with known active coronavirus disease 2019 (COVID-19) are unknown. OBJECTIVE: The purpose of this study was to gather information regarding CIED procedures during active COVID-19, performed with personal protective equipment, based on an international survey. METHODS: Fifty-three centers from 13 countries across 4 continents provided information on 166 patients with known active COVID-19 who underwent a CIED procedure. RESULTS: The CIED procedure rate in 133,655 hospitalized COVID-19 patients ranged from 0 to 16.2 per 1000 patients (P <.001). Most devices were implanted due to high-degree/complete atrioventricular block (112 [67.5%]) or sick sinus syndrome (31 [18.7%]). Of the 166 patients in the study survey, the 30-day complication rate was 13.9% and the 180-day mortality rate was 9.6%. One patient had a fatal outcome as a direct result of the procedure. Differences in patient and procedural characteristics and outcomes were found between Europe and North America. An older population (76.6 vs 66 years; P <.001) with a nonsignificant higher complication rate (16.5% vs 7.7%; P = .2) was observed in Europe vs North America, whereas higher rates of critically ill patients (33.3% vs 3.3%; P <.001) and mortality (26.9% vs 5%; P = .002) were observed in North America vs Europe. CONCLUSION: CIED procedure rates during known active COVID-19 disease varied greatly, from 0 to 16.2 per 1000 hospitalized COVID-19 patients worldwide. Patients with active COVID-19 infection who underwent CIED implantation had high complication and mortality rates. Operators should take these risks into consideration before proceeding with CIED implantation in active COVID-19 patients.