A Modular Communicative Leadless Pacing-Defibrillator System.

BACKGROUND: The subcutaneous implantable cardioverter-defibrillator (ICD) is associated with fewer lead-related complications than a transvenous ICD; however, the subcutaneous ICD cannot provide bradycardia and antitachycardia pacing. Whether a modular pacing-defibrillator system comprising a leadless pacemaker in wireless communication with a subcutaneous ICD to provide antitachycardia and bradycardia pacing is safe remains unknown. METHODS: We conducted a multinational, single-group study that enrolled patients at risk for sudden death from ventricular arrhythmias and followed them for 6 months after implantation of a modular pacemaker-defibrillator system. The safety end point was freedom from leadless pacemaker-related major complications, evaluated against a performance goal of 86%. The two primary performance end points were successful communication between the pacemaker and the ICD (performance goal, 88%) and a pacing threshold of up to 2.0 V at a 0.4-msec pulse width (performance goal, 80%). RESULTS: We enrolled 293 patients, 162 of whom were in the 6-month end-point cohort and 151 of whom completed the 6-month follow-up period. The mean age of the patients was 60 years, 16.7% were women, and the mean (±SD) left ventricular ejection fraction was 33.1±12.6%. The percentage of patients who were free from leadless pacemaker-related major complications was 97.5%, which exceeded the prespecified performance goal. Wireless-device communication was successful in 98.8% of communication tests, which exceeded the prespecified goal. Of 151 patients, 147 (97.4%) had pacing thresholds of 2.0 V or less, which exceeded the prespecified goal. The percentage of episodes of arrhythmia that were successfully terminated by antitachycardia pacing was 61.3%, and there were no episodes for which antitachycardia pacing was not delivered owing to communication failure. Of 162 patients, 8 died (4.9%); none of the deaths were deemed to be related to arrhythmias or the implantation procedure. CONCLUSIONS: The leadless pacemaker in wireless communication with a subcutaneous ICD exceeded performance goals for freedom from major complications related to the leadless pacemaker, for communication between the leadless pacemaker and subcutaneous ICD, and for the percentage of patients with a pacing threshold up to 2.0 V at a 0.4-msec pulse width at 6 months. (Funded by Boston Scientific; MODULAR ATP ClinicalTrials.gov NCT04798768.).

Machine Learning for Prediction of Ventricular Arrhythmia Episodes from Intracardiac Electrograms of Automatic Implantable Cardioverter-Defibrillators.

BACKGROUND: Despite the implantable cardioverter defibrillator's (ICD) effectiveness in saving patients with life-threatening ventricular arrhythmias (VAs), the temporal occurrence of VA following ICD implantation is unpredictable. OBJECTIVE: Apply machine learning (ML) to intracardiac electrograms (IEGMs) recorded by ICDs as a unique biomarker for predicting impending VAs. METHODS: The study included 13,516 patients who received BIOTRONIK ICDs and enrolled in the CERTITUDE registry between 01/01/2010 to 12/31/2020. Database extraction included IEGMs from standard quarterly transmissions and VA event episodes. The processed IEGM data were pulled from device transmissions stored in a centralized Home Monitoring Service Center and reformatted into an analyzable format. Long- (baseline or first scheduled remote recording), mid-(scheduled remote recording every 90 days), or short-range predictions (IEGM within 5 seconds before the VA onset) were used to determine whether ML-processed IEGMs predicted impending VA events. Convolutional neural network classifiers using ResNet architecture were employed. RESULTS: Of 13,516 patients (male 72%, age 67.5 ± 11.9 years), 301,647 IEGM recordings were collected; 27,845 episodes of sustained VT/VF were observed in 4,467 patients (33.0%). Neural networks based on CNN using ResNet-like architectures on far-field IEGMs yielded an AUC of 0.83 with a 95% confidence interval of [0.79, 0.87] in the short-term, while the long- and mid-range analyses had minimal predictive value for VA events. CONCLUSION: In this study, applying ML to ICD-acquired IEGMs predicted impending VT/VF events seconds before they occurred, whereas mid- to long-term predictions were not successful. This could have important implications for future device therapies.

Cardiac Resynchronization Therapy for Patients With Mild to Moderately Reduced Ejection Fraction and Left Bundle Branch Block.

BACKGROUND: It is unknown whether cardiac resynchronization therapy (CRT) would improve or halt the progression of heart failure (HF) in patients with mild to moderately reduced ejection fraction (HFmmrEF) and left bundle branch block (LBBB). OBJECTIVE: This study aimed to investigate the outcomes of CRT in patients with HFmmrEF and left ventricular conduction delay. METHODS: A prospective, randomized clinical trial sponsored by the National Heart, Lung, and Blood Institute included 76 patients who met the study inclusion criteria (left ventricular ejection fraction [LVEF] of 36%-50% and LBBB). Patients received CRT-pacemaker and were randomized to CRT-OFF (right ventricular pacing 40 beats/min) or CRT-ON (biventricular pacing 60-150 beats/min). At a 6-month follow-up, pacing programming was changed to the opposite settings. New York Heart Association class, N-terminal pro-brain natriuretic peptide levels, and echocardiographic variables were collected at baseline, 6 months, and 12 months. The primary study end point was the left ventricular end-systolic volume (LVESV) change from baseline, and the primary randomized comparison was the comparison of 6-month to 12-month changes between randomized groups. RESULTS: The mean age of the patients was 68.4 ± 9.8 years (male, 71%). Baseline characteristics were similar between the 2 randomized groups (all P > .05). In patients randomized to CRT-OFF first, then CRT-ON, LVESV was reduced from baseline only after CRT-ON (baseline, 116.1 ± 36.5 mL; CRT-ON, 87.6 ± 26.0 mL; P < .0001). The randomized analysis of LVEF showed a significantly better change from 6 to 12 months in the OFF-ON group (P = .003). LVEF was improved by CRT (baseline, 41.3% ±.7%; CRT-ON, 46.0% ± 8.0%; P = .002). In patients randomized to CRT-ON first, then CRT-OFF, LVESV was reduced after both CRT-ON and CRT-OFF (baseline, 109.8 ± 23.5 mL; CRT-ON, 91.7 ± 30.5 mL [P < .0001]; CRT-OFF, 99.3 ± 28.9 mL [P = .012]). However, the LVESV reduction effect became smaller between CRT-ON and CRT-OFF (P = .027). LVEF improved after both CRT-ON and CRT-OFF (baseline, 42.7% ± 4.3%; CRT-ON, 48.5% ± 8.6% [P < .001]; CRT-OFF, 45.9% ± 7.7% [P = .025]). CONCLUSION: CRT for patients with HFmmrEF significantly improves LVEF and ventricular remodeling after 6 months of CRT. The study provides novel evidence that early CRT benefits patients with HFmmrEF with LBBB.

Trends in the 30-year span of noninfectious cardiovascular implantable electronic device complications in Olmsted County.

Background: Cardiac implantable electronic devices (CIEDs), such as permanent pacemakers, implantable cardioverter-defibrillators, and cardiac resynchronization therapy devices, alleviate morbidity and mortality in various diseases. There is a paucity of real-world data on CIED complications and trends. Objectives: We sought to describe trends in noninfectious CIED complications over the past 3 decades in Olmsted County. Methods: The Rochester Epidemiology Project is a medical records linkage system comprising records of over 500,000 residents of Olmsted County from 1966 to present. CIED implantations between 1988 and 2018 were determined. Trends in noninfectious complications within 30 days of implantation were analyzed. Results: A total of 157 (6.2%) of 2536 patients who received CIED experienced device complications. A total of 2.7% of the implants had major complications requiring intervention. Lead dislodgement was the most common (2.8%), followed by hematoma (1.7%). Complications went up from 1988 to 2005, and then showed a downtrend until 2018, driven by a decline in hematomas in the last decade (P < .01). Those with complications were more likely to have prosthetic valves. Obesity appeared to have a protective effect in a multivariate regression model. The mean Charlson comorbidity index has trended up over the 30 years. Conclusion: Our study describes a real-world trend of CIED complications over 3 decades. Lead dislodgements and hematomas were the most common complications. Complications have declined over the last decade due to safer practices and a better understanding of anticoagulant management.

Electrical storm after left ventricular assist device (LVAD) implantation.

INTRODUCTION: Ventricular tachycardia storm or electrical storm (ES) is a common complication following left ventricular assist device (LVAD) implantation. The factors contributing to ES and outcomes are less studied. The study aimed to determine the factors associated with ES and the probability of survival in patients undergoing LVAD in three tertiary centers over a span of 15 years. METHODS: We performed a retrospective cohort study on all patients who underwent LVAD implantation at the Mayo Clinic (Rochester, Phoenix, and Jacksonville) from January 1, 2006 to December 31, 2020. ES was defined as ≥3 episodes of sustained ventricular tachycardia over a period of 24 h with no identifiable reversible cause. Detailed chart reviews of the electronic health records within the Mayo Clinic and outside medical records were performed. RESULTS: A total of 883 patients who underwent LVAD implantation were included in our study. ES occurred in 7% (n = 61) of patients with a median of 13 days (interquartile range [IQR]: 5-297 days) following surgery. We found 57% of patients (n = 35) developed ES within 30 days, while 43% (n = 26) patients developed ES at a median of 545  (IQR 152-1032) days after surgery. Following ES, 26% of patients died within 1 year. Patients with ES had a significant association with a history of ventricular arrhythmias and implantable cardioverter defibrillator (ICD) shocks before the procedure. ES was significantly associated with reduced survival compared to patients without ES (hazards ratio [HR]: 1.92, 95% CI: 1.39-2.64, p < .001). CONCLUSION: Following LVAD implantation, the rate of ES was 7% with majority of ES occurring within 30 days of LVAD. Risk factors for ES included pre-implant history of ventricular arrhythmias and ICD shock. ES was significantly associated with reduced survival compared to patients without ES.

Left bundle branch pacing vs ventricular septal pacing for cardiac resynchronization therapy.

Background: The outcomes of left bundle branch pacing (LBBP) and left ventricular septal pacing (LVSP) in patients with heart failure remain to be learned. Objective: The objective of this study was to assess the echocardiographic and clinical outcomes of LBBP, LVSP, and deep septal pacing (DSP). Methods: This retrospective study included patients who met the criteria for cardiac resynchronization therapy (CRT) and underwent attempted LBBP in 5 Mayo centers. Clinical, electrocardiographic, and echocardiographic data were collected at baseline and follow-up. Results: A total of 91 consecutive patients were included in the study. A total of 52 patients had LBBP, 25 had LVSP, and 14 had DSP. The median follow-up duration was 307 (interquartile range 208, 508) days. There was significant left ventricular ejection fraction (LVEF) improvement in the LBBP and LVSP groups (from 35.9 ± 8.5% to 46.9 ± 10.0%, P < .001 in the LBBP group; from 33.1 ± 7.5% to 41.8 ± 10.8%, P < .001 in the LVSP group) but not in the DSP group. A unipolar paced right bundle branch block morphology during the procedure in lead V1 was associated with higher odds of CRT response. There was no significant difference in heart failure hospitalization and all-cause deaths between the LBBP and LVSP groups. The rate of heart failure hospitalization and all-cause deaths were increased in the DSP group compared with the LBBP group (hazard ratio 5.10, 95% confidence interval 1.14-22.78, P = .033; and hazard ratio 7.83, 95% confidence interval 1.38-44.32, P = .020, respectively). Conclusion: In patients undergoing CRT, LVSP had comparable CRT outcomes compared with LBBP.

Leadless pacemakers at 5-year follow-up: the Micra transcatheter pacing system post-approval registry.

BACKGROUND AND AIMS: Prior reports have demonstrated a favourable safety and efficacy profile of the Micra leadless pacemaker over mid-term follow-up; however, long-term outcomes in real-world clinical practice remain unknown. Updated performance of the Micra VR leadless pacemaker through five years from the worldwide post-approval registry (PAR) was assessed. METHODS: All Micra PAR patients undergoing implant attempts were included. Endpoints included system- or procedure-related major complications and system revision rate for any cause through 60 months post-implant. Rates were compared through 36 months post-implant to a reference dataset of 2667 transvenous pacemaker patients using Fine-Gray competing risk models. RESULTS: 1809 patients were enrolled between July 2015 and March 2018 and underwent implant attempts from 179 centres in 23 countries with a median follow-up period of 51.1 months (IQR: 21.6-64.2). The major complication rate at 60 months was 4.5% [95% confidence interval (CI): 3.6%-5.5%] and was 4.1% at 36 months, which was significantly lower than the 8.5% rate observed for transvenous systems (HR: .47, 95% CI: .36-.61; P < .001). The all-cause system revision rate at 60 months was 4.9% (95% CI: 3.9%-6.1%). System revisions among Micra patients were mostly for device upgrades (41.2%) or elevated thresholds (30.6%). There were no Micra removals due to infection noted over the duration of follow-up. At 36 months, the system revision rate was significantly lower with Micra vs. transvenous systems (3.2% vs. 6.6%, P < .001). CONCLUSIONS: Long-term outcomes with the Micra leadless pacemaker continue to demonstrate low rates of major complications and system revisions and an extremely low incidence of infection.

Long-term outcomes with abandoning versus extracting sterile leads: A 10-year population-based study.

BACKGROUND: Long-term outcomes of sterile lead management strategies of lead abandonment (LA) or transvenous lead extraction (TLE) remain unclear. METHODS: We performed a retrospective study of a population residing in southeastern Minnesota with follow-up at the Mayo Clinic and its health systems. Patients who underwent LA or TLE of sterile leads from January 1, 2000, to January 1, 2011, and had follow-up for at least 10 years or until their death were included. RESULTS: A total of 172 patients were included in the study with 153 patients who underwent LA and 19 who underwent TLE for sterile leads. Indications for subsequent lead extraction arose in 9.1% (n = 14) of patients with initial LA and 5.3% (n = 1) in patients with initial TLE, after an average of 7 years. Moreover, 28.6% of patients in the LA cohort who required subsequent extraction did not proceed with the extraction, and among those who proceeded, 60% had clinical success and 40% had a clinical failure. Subsequent device upgrades or revisions were performed in 18.3% of patients in the LA group and 31.6% in the TLE group, with no significant differences in procedural challenges (5.2% vs. 5.3%). There was no difference in 10-year survival probability among the LA group and the TLE group (p = .64). CONCLUSION: An initial lead abandonment strategy was associated with more complicated subsequent extraction procedures compared to patients with an initial transvenous lead extraction strategy. However, there was no difference in 10-year survival probability between both lead management approaches.

Impact of infective versus sterile transvenous lead removal on 30-day outcomes in cardiac implantable electronic devices.

BACKGROUND: Transvenous lead removal (TLR) is associated with increased mortality and morbidity. This study sought to evaluate the impact of TLR on in-hospital mortality and outcomes in patients with and without CIED infection. METHODS: From January 1, 2017, to December 31, 2020, we utilized the nationally representative, all-payer, Nationwide Readmissions Database to assess patients who underwent TLR. We categorized TLR as indicated for infection, if the patient had a diagnosis of bacteremia, sepsis, or endocarditis during the initial admission. Conversely, if none of these conditions were present, TLR was considered sterile. The impact of infective vs sterile indications of TLR on mortality and major adverse events was studied. RESULTS: Out of the total 25,144 patients who underwent TLR, 14,030 (55.8%) received TLR based on sterile indications, while 11,114 (44.2%) received TLR due to device infection, with 40.5% having systemic infection and 59.5% having isolated pocket infection. TLR due to infective indications was associated with a significant in-hospital mortality (5.59% vs 1.13%; OR = 5.16; 95% CI 4.33-6.16; p < 0.001). Moreover, when compared with sterile indications, TLR performed due to device infection was associated with a considerable risk of thromboembolic events including pulmonary embolism and stroke (OR = 3.80; 95% CI 3.23-4.47, p < 0.001). However, there was no significant difference in the conversion to open heart surgery (1.72% vs. 1.47%, p < 0.111), and infection was not an independent predictor of cardiac (OR = 1.12; 95% CI 0.97-1.29) or vascular complications (OR = 1.12; 95% CI 0.73-1.72) between the two groups. CONCLUSION: Higher in-hospital mortality and rates of thromboembolic events associated with TLR resulting from infective indications may warrant further pursuing this diagnosis in patients.

Incidence and Outcomes of New-Onset Right Bundle Branch Block Following Transcatheter Aortic Valve Replacement.

BACKGROUND: The incidence and prognosis of right bundle branch block (RBBB) following transcatheter aortic valve replacement (TAVR) are unknown. Hence, we sought to characterize the incidence of post-TAVR RBBB and determine associated risks of permanent pacemaker (PPM) implantation and mortality. METHODS: All patients 18 years and above without preexisting RBBB or PPM who underwent TAVR at US Mayo Clinic sites and Mayo Clinic Health Systems from June 2010 to May 2021 were evaluated. Post-TAVR RBBB was defined as new-onset RBBB in the postimplantation period. The risks of PPM implantation (within 90 days) and mortality following TAVR were compared for patients with and without post-TAVR RBBB using Kaplan-Meier analysis and Cox proportional hazards modeling. The risks of PPM implantation (within 90 days) and mortality following TAVR were compared for patients with and without post-TAVR RBBB using Kaplan-Meier analysis and Cox proportional hazards modeling. RESULTS: Of 1992 patients, 15 (0.75%) experienced new RBBB post-TAVR. There was a higher degree of valve oversizing among patients with new RBBB post-TAVR versus those without (17.9% versus 10.0%; P=0.034). Ten patients (66.7%) with post-TAVR RBBB experienced high-grade atrioventricular block and underwent PPM implantation (median 1 day; Q1, 0.2 and Q3, 4), compared with 268/1977 (13.6%) without RBBB. Following propensity score adjustment for covariates (age, sex, balloon-expandable valve, annulus diameter, and valve oversizing), post-TAVR RBBB was significantly associated with PPM implantation (hazard ratio, 8.36 [95% CI, 4.19-16.7]; P<0.001). No statistically significant increase in mortality was seen with post-TAVR RBBB (hazard ratio, 0.83 [95% CI, 0.33-2.11]; P=0.69), adjusting for age and sex. CONCLUSIONS: Although infrequent, post-TAVR RBBB was associated with elevated PPM implantation risk. The mechanisms for its development and its clinical prognosis require further study.

2023 HRS/APHRS/LAHRS guideline on cardiac physiologic pacing for the avoidance and mitigation of heart failure.

Cardiac physiologic pacing (CPP), encompassing cardiac resynchronization therapy (CRT) and conduction system pacing (CSP), has emerged as a pacing therapy strategy that may mitigate or prevent the development of heart failure (HF) in patients with ventricular dyssynchrony or pacing-induced cardiomyopathy. This clinical practice guideline is intended to provide guidance on indications for CRT for HF therapy and CPP in patients with pacemaker indications or HF, patient selection, pre-procedure evaluation and preparation, implant procedure management, follow-up evaluation and optimization of CPP response, and use in pediatric populations. Gaps in knowledge, pointing to new directions for future research, are also identified.

Cardiac Resynchronisation with Conduction System Pacing.

To date, biventricular pacing (BiVP) has been the standard pacing modality for cardiac resynchronisation therapy. However, it is non-physiological, with the activation spreading between the left ventricular epicardium and right ventricular endocardium. Up to one-third of patients with heart failure who are eligible for cardiac resynchronisation therapy do not derive benefit from BiVP. Conduction system pacing (CSP), which includes His bundle pacing and left bundle branch area pacing, has emerged as an alternative to BiVP for cardiac resynchronisation. There is mounting evidence supporting the benefits of CSP in achieving synchronous ventricular activation and repolarisation. The aim of this review is to summarise the current options and outcomes of CSP when used for cardiac resynchronisation in patients with heart failure.