Initial heart rate score predicts new-onset atrial tachyarrhythmias in pacemaker patients.

AIMS: Heart rate score (HRSc), the per cent of atrial paced and sensed event in the largest 10 b.p.m. rate histogram bin of a pacemaker, predicts survival in patients with cardiac devices. No correlation between HRSc and development of atrial fibrillation (AF) has been reported. In this study, we evaluated the relationship between pacemaker post-implantation HRSc and the incidence of newly developed atrial tachyarrhythmias (ATAs). METHODS AND RESULTS: Patients with dual-chamber pacemakers, implanted 2013-17, with the LATITUDE remote monitoring data with ≥600 000 beats of histogram data collected at baseline were included (N = 34 543). Heart rate score was determined from the initial 3-month post-implantation histogram data. Patients were excluded if they had ATAs, defined as atrial high-rate episodes >5 min or >1% of right atrial beats >170 b.p.m. during the initial 3 months post-implantation. New ATAs, after the baseline period, were defined by each of the following: >1, >10, or >25% of atrial beats >170 b.p.m. or atrial tachycardia response (ATR) events >24 h. Patients were followed a median of 2.8 (1.0-4.0) years. The incidence of ATAs increased in proportion to HRSc (log-rank P-value <0.001), and the initial HRSc ≥70% was associated with increased ATAs by all definitions. Patients with initial HRSc ≥70% were older, had a higher percentage of right atrium pacing (%RA pacing), had a lower percentage of right ventricular pacing (%RV pacing), and were more likely programmed with rate-response vs. subjects with HRSc <70%. Initial HRSc (hazard ratio: 1.07, 95% confidence interval: 1.05-1.09; P < 0.0001) independently predicted ATAs after adjusting for age, gender, %RV pacing, and rate-response programming. The %RA pacing and initial HRSc were correlated. CONCLUSION: Heart rate score independently predicts any subsequent duration of ATAs in pacemaker patients.

Preliminary results from the LUX-Dx insertable cardiac monitor remote programming and performance (LUX-Dx PERFORM) study.

Despite the wide adoption of insertable cardiac monitors (ICMs), high false-positive rates, suboptimal signal quality, limited ability to detect atrial flutter, and lack of remote programming remain challenging. The LUX-Dx PERFORM study was designed to evaluate novel technologies engineered to address these issues. Here, we present preliminary results from the trial focusing on the safety of ICM insertion, remote monitoring rates, and the feasibility of remote programming. LUX-Dx PERFORM is a multicenter, prospective, single-arm, post-market, observational study with planned enrollment of up to 827 patients from 35 sites in North America. A preliminary cohort consisting of the first 369 patients who were enrolled between March and October 2021 was selected for analysis. Three hundred sixty-three (363) patients had ICM insertions across inpatient and outpatient settings. The mean time followed was 103.4 ± 61.8 days per patient. The total infection rate was 0.8% (3/363). Interim results show high levels of remote monitoring with a median 94% of days with data transmission (interquartile range: 82-99). Thirteen (13) in-clinic and 24 remote programming sessions were reported in 34 subjects. Reprogramming examples are presented to highlight signal quality, the ability to detect atrial flutter, and the positive impact of remote programming on patient management. Interim results from LUX-Dx PERFORM study demonstrate the safety of insertion, high data transmission rates, the ability to detect atrial flutter, and the feasibility of remote programming to optimize arrhythmia detection and improve clinical workflow. Future results from LUX-Dx PERFORM will further characterize improvements in signal quality and arrhythmia detection.

Lower rate limit for pacing by cardiac resynchronization defibrillators: Should lower rate programming be reconsidered?

BACKGROUND: No real-world large database associates lower rate limit (LRL) programming and survival of subjects with cardiac resynchronization therapy-defibrillators (CRT-Ds). OBJECTIVE: The purpose of this study was to test the hypothesis that lower LRL programming is independently associated with survival, and that LRL and heart rate score (HrSc) are associated. METHODS: All dual-chamber CRT-D devices in the Remote Patient Monitoring (RPM) ALTITUDE database (2006-2011) were queried. Baseline HrSc was defined as the percentage of all atrial sensed and paced beats in the tallest 10-beat histogram bin postimplant. LRL was assessed during repeated RPM uploads. Using a Cox model multivariable analysis, relationships between LRL, survival, HrSc, and other variables were evaluated. Survival was determined by query of death indices. RESULTS: Data analyzed included 61,881 subjects (mean follow-up 2.9 years). LRL ranged from 40 to 85 bpm. Baseline lower LRL was associated with younger age, less atrial fibrillation, female sex, and lower HrSc (P <.001 for all covariates). Lower LRL was associated with improved survival, with LRL 40 associated with the largest survival benefit. This was significant for all 3 HrSc subgroups (P <.001). An interaction between HrSc and LRL was observed, with the largest survival difference between HrSc groups observed at LRL-40 (P <.001). CONCLUSION: LRL programming and HrSc were associated, and lower values of both were associated with improved survival in a large database of CRT-D subjects. Relationships between survival, LRL programming, and HrSc merit further study.

A novel adaptive insertable cardiac monitor algorithm improves the detection of atrial fibrillation and atrial tachycardia in silico.

INTRODUCTION: Insertable cardiac monitors (ICMs) provide a minimally invasive method of continuous monitoring for abnormal heart rhythms. While the benefits of ICMs are clear, current algorithm performance can be improved. The objective of this study is to assess the performance of a novel adaptive atrial fibrillation (AF) detection algorithm and separately programmable atrial tachycardia (AT) algorithm. METHODS: A dual-stage detect-and-verify AF algorithm and separately programmable AT algorithm were developed. Sensitivity and PPV across a range of settings were determined in silico by comparison with an adjudicated Holter data set (n = 1966 with 229 patient days). Finally, the ability to improve performance through simulated remote programming was assessed. RESULTS: The dual-stage algorithm detected AF in all true AF patients (76/76) resulting in a patient-level sensitivity of 100%. Episode-level sensitivity and PPV ranged from 97.6% to 100% and 79.1% to 98.5%, respectively. Thirty-six false-positive episodes were observed and 32 (88.9%) of these were corrected with programming changes. Decoupling of AF and AT durations improved PPV from a range of 10%-22% to a range of 95%-100%. CONCLUSIONS: AF and AT algorithms were designed with novel features including an adaptive morphology assessment for AF detection and separately programmable durations for AT detection. In silico performance yielded improved PPVs while maintaining high sensitivity across a range of settings. Importantly, programming changes that may be made remotely with this system reduced false positives. These algorithms allow clinicians to individualize arrhythmia detection settings thereby improving data management and reducing clinic burden.

Heart rate score, a measure related to chronotropic incompetence in pacemaker patients.

BACKGROUND: Heart rate score (HrSc) ≥70% in cardiac resynchronization therapy defibrillator and implantable cardioverter-defibrillator subjects predicts 5-year mortality risk. A high HrSc suggests few sensed cardiac cycles above the programmed lower rate. OBJECTIVE: To determine if HrSc is related to chronotropic incompetence (CI) in pacemaker (PM) subjects. METHODS: HrSc is the percentage of all atrial-paced and sensed events in the single tallest 10 beats/min histogram bin programmed to DDD 60/min. The prospective LIFE study of PM subjects examined multiple treadmill-based measures of CI. The 1-month postimplant DDD 60/min PM rate histogram prior to treadmill was retrospectively analyzed for HrSc. Measures of CI were applied to submaximal treadmill data in the DDD mode. HrSc was compared to these CI measures and to clinical indications for PM. RESULTS: The 1-month histogram demonstrated HrSc ≥70% in 43% of subjects. HrSc ≥70% correlated with a clinical diagnosis of sick sinus syndrome (P < .001). CI was present in 34%-88% of subjects by treadmill-based measures. Agreement between treadmill-based measures for CI was poor and varied from 39% to 83%. HrSc ≥70%, as a measure of CI, was most highly correlated with unpaced heart rate <70% of age-predicted maximum heart rate (67%) (odds ratio 3.7, P < .001). CONCLUSIONS: HrSc ≥70% correlates with treadmill measures of CI and clinical sick sinus syndrome. HrSc ≥70% is a measure of CI in PM subjects that is inexpensive, repeatable, and quantitative.

Heart rate score predicts mortality independent of shocks in ICD and CRT-D patients.

BACKGROUND: Heart Rate Score (HrSc), a novel index found to predict mortality in patients with implantable defibrillator (ICD) and cardiac resynchronization defibrillator (CRT-D) devices, is associated with mortality in ICD and CRT-D recipients when HrSc is ≥ 70%. Implantable defibrillator shocks have also been associated with increased mortality in ICD and CRT-D recipients. The objective of this study was to evaluate the relationships between HrSc, shocks, and mortality in ICD and CRT-D patients. METHODS: HrSc was calculated from atrial sensed and paced rate histograms collected from the 2006-2011 ALTITUDE remote interrogation database. Shocks were determined in the first year of follow-up. Mortality was assessed over the next 4 years by the Social Security Death Index. Four multivariable models were run: ICD and CRT-D, shock and no shock, with mortality as the outcome and HrS as predictor. RESULTS: Data from 49,358 ICD and 55,953 CRT-D patients were divided into HrSc: ≥ 70%, 30-69%, and < 30%. Shock rates differed between HrSc groups (p < 0.001) for ICD and CRT-D patients. However, the lowest mortality risk HrSc (< 30%) had the highest shock rate. Both highest HrSc (> 70%; p < 0.001) and shocks (p < 0.001) predicted mortality during follow-up. Mortality was unrelated to interactions between HrSc and shocks in ICD patients (p = 0.275) or CRT-D patients (p < 0.079). Comparing HrSc ≥ 70% to HrSc < 30%, HrSc ≥ 70% predicted mortality in CRT-D (HR 1.40; 95% CI 1.29-1.52) and ICD (HR 1.23; 95% CI 1.11-1.36) patients regardless of shocks (P < 0.001 for both). CONCLUSIONS: Patients with ICDs or CRT-Ds having the lowest mortality risk HrSc had the highest shock rate. Shocks and HrSc appear to complement each other as predictors of mortality.

Addition of minute ventilation to rate-response pacing improves heart rate score more than accelerometer alone.

BACKGROUND: Heart rate score (HRSc) ≥70%, a novel parameter, predicts risk of mortality in patients with implantable cardioverter-defibrillators and identifies patients who have survival benefit with DDDR vs DDD pacing. OBJECTIVE: The purpose of this study was to determine if DDDR pacing lowers HRSc, and a blended sensor with minute ventilation (MV) and accelerometer (XL) improves HRSc more than accelerometer (XL) alone in patients requiring pacemakers (PMs). METHODS: HRSc, the percentage of all beats in the tallest 10-beat/min device histogram bin, was calculated. Data from the Limiting Chronotropic Incompetence for Pacemaker Recipients Study, a prospective randomized trial of PM patients, comparing XL to blended-sensor (XL + MV) rate-responsive pacing, were analyzed retrospectively for HRSc changes from baseline. The relationship of patient activity (sensor-detected from device memory) to HRSc was examined. RESULTS: Of the 501 randomized patients, 215 (43%) patients had HRSc ≥70% during DDD pacing at baseline. In these patients, HRSc decreased after DDDR programming by 14.2%, while it increased by 0.4% in those with baseline HRSc <70% (n = 286) (HRSc ≥70% vs HRSc <70%; P < .01). No differences were detected between the 2 randomized sensor-based groups at baseline. Blended-sensor (MV + XL) programming reduced HRSc more than the XL sensor alone (MV + XL: 18% vs XL: 10%; P < .001). No correlation was observed between patient activity and HRSc (correlation = -0.14; P = .07). CONCLUSION: HRSc improved (reduced) with rate-response (DDDR) programming in PM patients with high HRSc during DDD pacing. Blended sensors (MV + XL) improved HRSc more than XL alone. HRSc does not correlate with patient activity levels, suggesting that other patient factors determine this parameter. This programming approach needs to be investigated prospectively in a PM outcomes trial.

A Device Histogram-Based Simple Predictor of Mortality Risk in ICD and CRT-D Patients: The Heart Rate Score.

BACKGROUND: We hypothesized that survival in implantable cardioverter defibrillator (ICD) and cardiac resynchronization therapy defibrillator (CRT-D) patients is predicted by baseline Heart Rate Score. METHODS: Heart Rate Score is determined from the atrial paced and sensed histogram of a DDD ICD or CRT-D, and defined as percent of beats in the histogram in the tallest 10 beats/min range bin. It was calculated at initial remote monitoring for patients enrolled in LATITUDE® without persistent atrial fibrillation, and with pulse generators implanted in 2006-2011. Univariate, multivariate, and Kaplan-Meier analyses determined the impact of Heart Rate Score on survival. RESULTS: Of 57,893 ICDs and 67,929 CRT-Ds followed for 2.4 ± 1.5 years, each 10% increase in Heart Rate Score was associated with decreased survival (CRT-D hazard ratio [HR] 1.07 95%, confidence interval 1.06-1.07, P < 0.0001; ICD HR 1.05, 95% confidence interval 1.04-1.06, P < 0.0001). Multivariate analysis showed survival decreased with increasing age, atrial fibrillation, presence of a shock in first-year follow-up, and increasing programmed lower pacing rate in ICD and CRT-D patients. Increased percent right ventricular pacing predicted mortality in ICD patients, while male gender and lower percent left ventricular pacing predicted mortality in CRT patients. Heart Rate Score predicted survival independent of those variables. Heart Rate Score correlates with heart rate variability (standard deviation of average R-R intervals [SDANN]) when both are obtainable, but SDANN was only present in 6% of patients with Heart Rate Score >70%. CONCLUSION: A simple device histogram measure, Heart Rate Score, predicts survival in ICD and CRT-D patients independent of the available variables, and even when SDANN is unavailable.

Survival After Rate-Responsive Programming in Patients With Cardiac Resynchronization Therapy-Defibrillator Implants Is Associated With a Novel Parameter: The Heart Rate Score.

BACKGROUND: Rate-responsive pacing (DDDR) versus nonrate-responsive pacing (DDD) has shown no survival benefit for patients undergoing cardiac resynchronization therapy defibrillator (CRT-D) implants. The heart rate score (HRSc), an indicator of heart rate variation, may predict survival. We hypothesized that high-risk HRSc CRT-D patients will have improved survival with DDDR versus DDD alone. METHODS AND RESULTS: All CRT-D patients in LATITUDE remote monitoring (2006-2011), programmed DDD, had HRSc calculated at first data upload after implant (median 1.4 months). Patients subsequently reprogrammed to DDDR 7.6 median months later were compared with a propensity-matched DDD group and followed for 21.4 median months by remote monitoring. Data were adjusted for age, sex, lower rate limit, percent atrial pacing, percent biventricular pacing, and implant year. The social security death index was used to identify deaths. Remote monitoring provided programming and histogram data. DDDR programming in CRT-D patients was associated with improved survival (adjusted hazard ratio =0.77; P<0.001). However, only those with baseline HRSc ≥70% (2308/6164) had improved HRSc with DDDR (from 88±9% to 78±15%; P<0.001) and improved survival (hazard ratio =0.74; P<0.001). Patients with a high baseline HRSc and significant improvement over time were more likely to survive (hazard ratio =0.63; P=0.006). For patients with HRSc <70%, DDDR reprogramming increased the HRSc from 46±11% to 50±15% (P<0.001); survival did not change. The HRSc did not change with DDD pacing over time. CONCLUSIONS: In CRT-D patients with HRSc ≥70%, DDDR reprogramming improved the HRSc and was associated with survival. Patients with lower HRSc had no change in survival with DDDR programming.

Noise, artifact, and oversensing related inappropriate ICD shock evaluation: ALTITUDE noise study.

BACKGROUND: Approximately 12-21% of implantable cardioverter defibrillator (ICD) patients receive inappropriate shocks. We sought to determine the incidence and causes of noise/artifact and oversensing (NAO) resulting in ICD shocks. METHODS: A random sample of 2,000 patients who received ICD and cardiac resynchronization therapy defibrillator shocks and were followed by a remote monitoring system was included. Seven electrophysiologists analyzed stored electrograms from the 5,279 shock episodes. Episodes were adjudicated as appropriate or inappropriate shocks. RESULTS: Of the 5,248 shock episodes with complete adjudication, 1,570 (30%) were judged to be inappropriate shocks. Of these 1,570, 134 (8.5%) were a result of NAO. The 134 NAO episodes were determined to be due to external noise in 76 (57%), lead connector-related in 37 (28%), muscle noise in 11 (8%), oversensing of atrium in seven (5%), T-wave oversensing in two (2%), and other noise in one (1%). The ICD shock itself resulted in a marked decrease in the level of noise in 60 of 134 (45%) NAO episodes, and the magnitude of this effect varied with the type of NAO (58% for external noise, 35% for muscle, 27% for lead/connector, and 0% for oversensing; P = 0.03). There was no significant difference in NAO likelihood based on type of lead (integrated bipolar 89/1,802 vs dedicated bipolar 9/140, P = 0.67). CONCLUSIONS: External noise and lead/connector noise were the primary causes, while T-wave oversensing was the least common cause of NAO resulting in ICD shock. Noise/artifact decreased immediately after a shock in nearly half of episodes. The specific ICD lead type did not impact the likelihood of NAO.

Arrhythmia rate distribution and tachyarrhythmia therapy in an ICD population: results from the INTRINSIC RV trial.

BACKGROUND: Appropriate implantable cardioverter-defibrillator (ICD) therapy for ventricular tachycardia (VT) or ventricular fibrillation (VF) depends, in part, on the programming of tachycardia zones. OBJECTIVE: We assessed events treated with ICD shocks or antitachycardia pacing (ATP) in the Inhibition of Unnecessary RV Pacing with AV Search Hysteresis in ICDs (INTRINSIC RV) trial. METHODS: ATP and shock episodes from 1530 patients with dual-chamber ICDs were analyzed. RESULTS: For episodes in which electrograms were stored and adjudicated, ATP was delivered for 763 episodes (182 patients), shock-only was delivered for 300 episodes (146 patients), and shock following ATP was delivered for 81 episodes (56 patients). ATP was delivered appropriately for 507 episodes (130 patients), with 93% success, and inappropriately for 256 episodes (89 patients). For ATP episodes, appropriate (VT: 170 ± 28 bpm) and inappropriate (not VT: 165 ± 21 bpm) rates did not differ (P = .16). When the initial therapy was shock, onset rates were higher for appropriate therapy than for inappropriate therapy (224 ± 46 bpm vs 187 ± 31 bpm; P <.001). Inappropriate ATP was more likely to be followed by a shock (odds ratio 2.49; 95% confidence interval 1.56-3.97; P <.001). Fifty-eight percent (225 of 381) of shocked episodes had rates <200 bpm. For episodes between 200 and 250 bpm, 20% (23 of 113) were polymorphic VT or VF, 59% were monomorphic VT, 19% were supraventricular, and <1% was artifact. For episodes >250 bpm, 37% were VF, 28% polymorphic VT, 23% monomorphic VT, 7% supraventricular, and 5% artifact. CONCLUSIONS: In a general ICD population, ATP treated VT effectively or obviated the need for shock. Most ventricular arrhythmias <250 bpm were not VF. Proper zone programming may identify and treat VT without shock.