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.

The Use of Electrocardiogram Smartwatches in Patients with Cardiac Implantable Electrical Devices.

Unlimited access to ECGs using an over-the-counter smartwatch constitutes a real revolution for our discipline, and the application is rapidly expanding to include patients with cardiac implantable electronic devices (CIEDs) such as pacemakers (PMs) and implantable cardioverter defibrillators (ICDs). CIEDs require periodic evaluation and adjustment by healthcare professionals. In addition, implanted patients often present with symptoms that may be related to their PMs or ICDs. An ECG smartwatch could reveal information about device functioning, confirm normal device function, or aid in the case of device troubleshooting. In this review, we delve into the available evidence surrounding smartwatches with ECG registration and their integration into the care of patients with implanted pacemakers and ICDs. We explore safety considerations and the benefits and limitations associated with these wearables, drawing on relevant studies and case series from our own experience. By analyzing the current landscape of this emerging technology, we aim to provide a comprehensive overview that facilitates informed decision-making for both healthcare professionals and patients.

Feasibility and Diagnostic Value of Recording Smartwatch Electrocardiograms in Neonates and Children.

OBJECTIVE: The objective of this study was to evaluate the agreement of smartwatch-derived single-lead electrocardiogram (ECG) recordings with 12-lead ECGs for diagnosing electrocardiographic abnormalities. STUDY DESIGN: A 12-lead ECG and an ECG using Apple Watch were obtained in 110 children (aged 1 week to 16 years) with normal (n = 75) or abnormal (n = 35) 12-lead ECGs (atrioventricular block [7], supraventricular tachycardia [SVT] {5}, bundle branch block [12], ventricular preexcitation [6], long QT [5]). In children aged <6 years, the ECG recording was performed with the active participation of an adult who applied the neonate or child's finger to the crown of the watch. In older children, tracings were obtained after brief teaching without adult guidance. All 12-lead ECGs were independently evaluated by 2 blinded cardiologists. Apple Watch ECGs were independently evaluated by another blinded cardiologist. RESULTS: In 109 children (99.1%), the smartwatch tracing was of sufficient quality for evaluation. Smartwatch tracings were 84% sensitive and 100% specific for the detection of an abnormal ECG. All 75 normal tracings were correctly identified. Of the 35 children with abnormalities on 12-lead ECGs, 5 (14%) were missed, most often because of baseline wander and artifacts. Rhythm disorders (atrioventricular block or SVT) and bundle branch blocks were correctly detected in most cases (11 of 12 and 11 of 12, respectively); preexcitation and long QT was detected in 4 of 6 and 4 of 5, respectively. CONCLUSION: Smartwatch ECGs recorded with parental assistance in children aged up to 6 years and independently in older children have the potential to detect clinically relevant conditions.

Implantation of a leadless pacemaker in young adults.

AIMS: Leadless pacing has emerged as an alternative to conventional transvenous pacemakers to mitigate the risks of pocket- and lead-related complications but its use remains controversial in young adults mostly because experience in this patient population is limited. We sought to examine the feasibility and safety of implanting leadless single chamber pacemakers in young adults. METHODS: This multicenter, retrospective, observational study sought to evaluate the safety, efficacy, and electrical performance of the Micra VR Transcatheter Pacemaker System (Medtronic) in patients between 18 and 40 years who underwent implantation of a leadless pacemaker for any indication at the university medical centers of Bordeaux, Clermont-Ferrand, Toulouse, and Tours (France), between 2015 and 2021. The primary safety endpoint was freedom from system-related or procedure-related major complications at 6 months. The primary efficacy endpoint was the combination of a low (≤2 V) and stable (increase within 1.5 V) pacing capture threshold at 6 months. RESULTS: Leadless pacemaker implantation was successful in all 35 patients. At 6 months, safety endpoint was met for 35 (100%) and efficacy endpoint for 34 (97%) patients. During a follow-up of 26 ± 15 months (range: 6-60 months), Safety endpoint remained 100% and efficacy endpoint was 94%. Leadless pacemaker retrieval was not required in any patient. Approximately one-third of patients (n = 13, 37%) had >40% ventricular pacing burdens at 1 year, including all 10 patients with a complete AV block but also 3 patients with normal AV conduction during implantation. One patient reported symptoms of pacemaker syndrome which was confirmed using Holter recording and successfully treated using reprogramming. CONCLUSION: In this observational study, leadless pacemakers demonstrated favorable short- and intermediate-term safety and effectiveness in young adults.

Advanced Imaging Integration for Catheter Ablation of Ventricular Tachycardia.

PURPOSE OF REVIEW: Imaging plays a crucial role in the therapy of ventricular tachycardia (VT). We offer an overview of the different methods and provide information on their use in a clinical setting. RECENT FINDINGS: The use of imaging in VT has progressed recently. Intracardiac echography facilitates catheter navigation and the targeting of moving intracardiac structures. Integration of pre-procedural CT or MRI allows for targeting the VT substrate, with major expected impact on VT ablation efficacy and efficiency. Advances in computational modeling may further enhance the performance of imaging, giving access to pre-operative simulation of VT. These advances in non-invasive diagnosis are increasingly being coupled with non-invasive approaches for therapy delivery. This review highlights the latest research on the use of imaging in VT procedures. Image-based strategies are progressively shifting from using images as an adjunct tool to electrophysiological techniques, to an integration of imaging as a central element of the treatment strategy.

Purkinje network and myocardial substrate at the onset of human ventricular fibrillation: implications for catheter ablation.

AIMS: Mapping data of human ventricular fibrillation (VF) are limited. We performed detailed mapping of the activities underlying the onset of VF and targeted ablation in patients with structural cardiac abnormalities. METHODS AND RESULTS: We evaluated 54 patients (50 ± 16 years) with VF in the setting of ischaemic (n = 15), hypertrophic (n = 8) or dilated cardiomyopathy (n = 12), or Brugada syndrome (n = 19). Ventricular fibrillation was mapped using body-surface mapping to identify driver (reentrant and focal) areas and invasive Purkinje mapping. Purkinje drivers were defined as Purkinje activities faster than the local ventricular rate. Structural substrate was delineated by electrogram criteria and by imaging. Catheter ablation was performed in 41 patients with recurrent VF. Sixty-one episodes of spontaneous (n = 10) or induced (n = 51) VF were mapped. Ventricular fibrillation was organized for the initial 5.0 ± 3.4 s, exhibiting large wavefronts with similar cycle lengths (CLs) across both ventricles (197 ± 23 vs. 196 ± 22 ms, P = 0.9). Most drivers (81%) originated from areas associated with the structural substrate. The Purkinje system was implicated as a trigger or driver in 43% of patients with cardiomyopathy. The transition to disorganized VF was associated with the acceleration of initial reentrant activities (CL shortening from 187 ± 17 to 175 ± 20 ms, P < 0.001), then spatial dissemination of drivers. Purkinje and substrate ablation resulted in the reduction of VF recurrences from a pre-procedural median of seven episodes [interquartile range (IQR) 4-16] to 0 episode (IQR 0-2) (P < 0.001) at 56 ± 30 months. CONCLUSIONS: The onset of human VF is sustained by activities originating from Purkinje and structural substrate, before spreading throughout the ventricles to establish disorganized VF. Targeted ablation results in effective reduction of VF burden. KEY QUESTION: The initial phase of human ventricular fibrillation (VF) is critical as it involves the primary activities leading to sustained VF and arrhythmic sudden death. The origin of such activities is unknown. KEY FINDING: Body-surface mapping shows that most drivers (≈80%) during the initial VF phase originate from electrophysiologically defined structural substrates. Repetitive Purkinje activities can be elicited by programmed stimulation and are implicated as drivers in 37% of cardiomyopathy patients. TAKE-HOME MESSAGE: The onset of human VF is mostly associated with activities from the Purkinje network and structural substrate, before spreading throughout the ventricles to establish sustained VF. Targeted ablation reduces or eliminates VF recurrence.

Using a Smartwatch to Record Precordial Electrocardiograms: A Validation Study.

Smartwatches that support the recording of a single-lead electrocardiogram (ECG) are increasingly being used beyond the wrist, by placement on the ankle and on the chest. However, the reliability of frontal and precordial ECGs other than lead I is unknown. This clinical validation study assessed the reliability of an Apple Watch (AW) to obtain conventional frontal and precordial leads as compared to standard 12-lead ECGs in both subjects without known cardiac anomalies and patients with underlying heart disease. In 200 subjects (67% with ECG anomalies), a standard 12-lead ECG was performed, followed by AW recordings of the standard Einthoven leads (leads I, II, and III) and precordial leads V1, V3, and V6. Seven parameters (P, QRS, ST, and T-wave amplitudes, PR, QRS, and QT intervals) were compared through a Bland-Altman analysis, including the bias, absolute offset, and 95% limits of agreement. AW-ECGs recorded on the wrist but also beyond the wrist had similar durations and amplitudes compared to standard 12-lead ECGs. Significantly greater amplitudes were measured by the AW for R-waves in precordial leads V1, V3, and V6 (+0.094 mV, +0.149 mV, +0.129 mV, respectively, all p < 0.001), indicating a positive bias for the AW. AW can be used to record frontal, and precordial ECG leads, paving the way for broader clinical applications.

Improving Automatic Smartwatch Electrocardiogram Diagnosis of Atrial Fibrillation by Identifying Regularity within Irregularity.

Smartwatches equipped with automatic atrial fibrillation (AF) detection through electrocardiogram (ECG) recording are increasingly prevalent. We have recently reported the limitations of the Apple Watch (AW) in correctly diagnosing AF. In this study, we aim to apply a data science approach to a large dataset of smartwatch ECGs in order to deliver an improved algorithm. We included 723 patients (579 patients for algorithm development and 144 patients for validation) who underwent ECG recording with an AW and a 12-lead ECG (21% had AF and 24% had no ECG abnormalities). Similar to the existing algorithm, we first screened for AF by detecting irregularities in ventricular intervals. However, as opposed to the existing algorithm, we included all ECGs (not applying quality or heart rate exclusion criteria) but we excluded ECGs in which we identified regular patterns within the irregular rhythms by screening for interval clusters. This "irregularly irregular" approach resulted in a significant improvement in accuracy compared to the existing AW algorithm (sensitivity of 90% versus 83%, specificity of 92% versus 79%, p < 0.01). Identifying regularity within irregular rhythms is an accurate yet inclusive method to detect AF using a smartwatch ECG.

Using a smartwatch electrocardiogram to detect abnormalities associated with sudden cardiac arrest in young adults.

AIMS: Smartwatch electrocardiograms (ECGs) could facilitate the detection of sudden cardiac arrest (SCA)-associated abnormalities. We evaluated the feasibility of using smartwatch-derived ECGs for detecting SCA-associated abnormalities in young adults and its agreement with 12-lead ECGs. METHODS AND RESULTS: Twelve-lead and Apple Watch ECGs were registered in 155 healthy volunteers and 67 patients aged 18-45 years with diagnosis and ECG signs of long-QT syndrome (n = 10), Brugada syndrome (n = 12), ventricular pre-excitation (n = 19), hypertrophic cardiomyopathy (HCM, n = 13), and arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVC/D, n = 13). Cardiologists separately analysed 12-lead ECGs and the smartwatch ECGs taken from the left wrist (AW-I) and then from chest positions V1, V3, and V6 (AW-4). Compared with AW-I, AW-4 improved the classification of ECGs as 'abnormal', increasing the sensitivity from 64% to 89% (P < 0.01). Pre-excitation was detected in most cases using AW-I (sensitivity 89%) and in all cases using AW-4 (sensitivity 100%, P = 0.48 compared with AW-I, specificity 100% for both). Brugada was missed using AW-I but was detected in 11/12 patients using AW-4 (sensitivity 92%, specificity 100%, P = 0.003). Long QT was detected in 8/10 cases using AW-I (sensitivity 80%, specificity 100%) and in 9 patients using AW-4 (sensitivity 90%, specificity 100%, P > 0.99). Hypertrophic cardiomyopathy was correctly suspected using AW-I and AW-4 (sensitivity 92% and 85%, specificity 85%, and 100%, P > 0.99). AW-I was mostly (62%) considered normal in ARVC/D whereas AW-4 was useful in suspecting ARVC/D (100% sensitivity, 99% specificity, P = 0.004). CONCLUSIONS: Detection of SCA-associated ECG abnormalities (pre-excitation, Brugada patterns, long QT, and signs suggestive of HCM and ARVC/D) is possible with an ECG smartwatch.

Pacing therapy for atrioventricular dromotropathy: a combined computational-experimental-clinical study.

AIMS: Investigate haemodynamic effects, and their mechanisms, of restoring atrioventricular (AV)-coupling using pacemaker therapy in normal and failing hearts in a combined computational-experimental-clinical study. METHODS AND RESULTS: Computer simulations were performed in the CircAdapt model of the normal and failing human heart and circulation. Experiments were performed in a porcine model of AV dromotropathy. In a proof-of-principle clinical study, left ventricular (LV) pressure and volume were measured in 22 heart failure (HF) patients (LV ejection fraction <35%) with prolonged PR interval (>230 ms) and narrow or non-left bundle branch block QRS complex. Computer simulations and animal studies in normal hearts showed that restoring of AV-coupling with unchanged ventricular activation sequence significantly increased LV filling, mean arterial pressure, and cardiac output by 10-15%. In computer simulations of failing hearts and in HF patients, reducing PR interval by biventricular (BiV) pacing (patients: from 300 ± 61 to 137 ± 30 ms) resulted in significant increases in LV stroke volume and stroke work (patients: 34 ± 40% and 26 ± 31%, respectively). However, worsening of ventricular dyssynchrony by using right ventricular (RV) pacing abrogated the benefit of restoring AV-coupling. In model simulations, animals and patients, the increase of LV filling and associated improvement of LV pump function coincided with both larger mitral inflow (E- and A-wave area) and reduction of diastolic mitral regurgitation. CONCLUSION: Restoration of AV-coupling by BiV pacing in normal and failing hearts with prolonged AV conduction leads to considerable haemodynamic improvement. These results indicate that BiV or physiological pacing, but not RV pacing, may improve cardiac function in patients with HF and prolonged PR interval.

Using a smartwatch to record an electrocardiogram in the pediatric population.

The accuracy of smartwatch ECG recordings in adults has been demonstrated primarily in the automated diagnosis of atrial fibrillation. While the detection of atrial fibrillation is a priority among adults given the arrhythmia's prevalence and actionable ramifications, the potential value of smartwatch ECG recordings in children differs considerably. In this case series, we will describe some examples of smartwatch ECGs recorded in children, highlighting the feasibility and potential indications of this technology in the pediatric population.

Long-Term Follow-Up of Patients With Tetralogy of Fallot and Implantable Cardioverter Defibrillator: The DAI-T4F Nationwide Registry.

BACKGROUND: Tetralogy of Fallot (TOF) is the most common cyanotic congenital heart disease, and sudden cardiac death represents an important mode of death in these patients. Data evaluating the implantable cardioverter defibrillator (ICD) in this patient population remain scarce. METHODS: A Nationwide French Registry including all patients with tetralogy of Fallot with an ICD was initiated in 2010 by the French Institute of Health and Medical Research. The primary time to event end point was the time from ICD implantation to first appropriate ICD therapy. Secondary outcomes included ICD-related complications, heart transplantation, and death. Clinical events were centrally adjudicated by a blinded committee. RESULTS: A total of 165 patients (mean age, 42.2±13.3 years, 70.1% males) were included from 40 centers, including 104 (63.0%) in secondary prevention. During a median (interquartile range) follow-up of 6.8 (2.5-11.4) years, 78 (47.3%) patients received at least 1 appropriate ICD therapy. The annual incidence of the primary outcome was 10.5% (7.1% and 12.5% in primary and secondary prevention, respectively; P=0.03). Overall, 71 (43.0%) patients presented with at least 1 ICD complication, including inappropriate shocks in 42 (25.5%) patients and lead dysfunction in 36 (21.8%) patients. Among 61 (37.0%) patients in primary prevention, the annual rate of appropriate ICD therapies was 4.1%, 5.3%, 9.5%, and 13.3% in patients with, respectively, 0, 1, 2, or ≥3 guidelines-recommended risk factors. QRS fragmentation was the only independent predictor of appropriate ICD therapies (hazard ratio, 3.47 [95% CI, 1.19-10.11]), and its integration in a model with current criteria increased the 5-year time-dependent area under the curve from 0.68 to 0.81 (P=0.006). Patients with congestive heart failure or reduced left ventricular ejection fraction had a higher risk of nonarrhythmic death or heart transplantation (hazard ratio, 11.01 [95% CI, 2.96-40.95]). CONCLUSIONS: Patients with tetralogy of Fallot and an ICD experience high rates of appropriate therapies, including those implanted in primary prevention. The considerable long-term burden of ICD-related complications, however, underlines the need for careful candidate selection. A combination of easy-to-use criteria including QRS fragmentation might improve risk stratification. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT03837574.

His bundle pacing for newly acquired pacing needs in patients implanted with a subcutaneous implantable cardioverter defibrillator: A feasibility study based on the automated screening score and clinical cases.

INTRODUCTION: Management of subcutaneous implantable cardioverter defibrillator (S-ICD) patients with newly acquired pacing needs remains problematic. His bundle pacing (HBP) allows for cardiac pacing without significant changes in the QRS morphology. We hypothesized that HBP does not alter S-ICD sensing and functions. METHODS: Twenty consecutive patients were implanted with a HB pacemaker. Among them, 17 demonstrated successful His recruitment and were prospectively screened with the automated screening tool (AST). Results of screenings performed immediately after implant and during follow-up, during intrinsic rhythm and while pacing from all available pacing configurations, were compared using the AST score. Positive-screening tests were defined by greater than or equal to 1 positive vector. RESULTS: Among the 17 patients successfully implanted (male: 41%; mean age: 73), 13 presented an indication of ventricular pacing and four of cardiac resynchronization. Absolute AST scores during both HBP (all configurations) and intrinsic rhythm were similar (p: NS). Due to left bundle branch block correction, HBP resulted in higher number of positive vectors (AST ≥ 100). AST scores were higher during HBP when compared with right ventricular pacing (RVP) (primary vector: 272 [16; 648] vs 4.6 [0.8; 16.2]; P = .003; secondary vector: 569 [183; 1186] vs 1.5 [0.7; 8.3]; P < .0001; alternate vector: 44 [2;125] vs 4.8 [0.9; 9.3]; P = .02) and resulted in a much higher number of positive vectors. Up to 90% of the patients had a positive-screening test during HBP. This passing rate was higher when compared RVP (17%; P < .0001). CONCLUSION: HBP restores normal intrinsic conduction and minimally modifies the surface electrocardiograph and subcutaneous electrograms. When ventricular pacing is needed, HBP might represent an ideal pacing option for patients implanted with a S-ICD.

Electrogram morphology discriminators in implantable cardioverter defibrillators: A comparative evaluation.

BACKGROUND: Morphology algorithms are currently recommended as a standalone discriminator in single-chamber implantable cardioverter defibrillators (ICDs). However, these proprietary algorithms differ in both design and nominal programming. OBJECTIVE: To compare three different algorithms with nominal versus advanced programming in their ability to discriminate between ventricular (VT) and supraventricular tachycardia (SVT). METHODS: In nine European centers, VT and SVTs were collected from Abbott, Boston Scientific, and Medtronic dual- and triple-chamber ICDs via their respective remote monitoring portals. Percentage morphology matches were recorded for selected episodes which were classified as VT or SVT by means of atrioventricular comparison. The sensitivity and related specificity of each manufacturer discriminator was determined at various values of template match percentage from receiving operating characteristics (ROC) curve analysis. RESULTS: A total of 534 episodes were retained for the analysis. In ROC analyses, Abbott Far Field MD (area under the curve [AUC]: 0.91; P < .001) and Boston Scientific RhythmID (AUC: 0.95; P < .001) show higher AUC than Medtronic Wavelet (AUC: 0.81; P < .001) when tested for their ability to discriminate VT from SVT. At nominal % match threshold all devices provided high sensitivity in VT identification, (91%, 100%, and 90%, respectively, for Abbott, Boston Scientific, and Medtronic) but contrasted specificities in SVT discrimination (85%, 41%, and 62%, respectively). Abbott and Medtronic's nominal thresholds were similar to the optimal thresholds. Optimization of the % match threshold improved the Boston Scientific specificity to 79% without compromising the sensitivity. CONCLUSION: Proprietary morphology discriminators show important differences in their ability to discriminate SVT. How much this impact the overall discrimination process remains to be investigated.

Feasibility of His-bundle pacing in patients with conduction disorders following transcatheter aortic valve replacement.

BACKGROUND: Conduction disorders requiring permanent pacemaker implantation occur frequently after transcatheter aortic valve replacement (TAVR). This multicenter study explored the feasibility and safety of His bundle pacing (HBP) in TAVR patients with a pacemaker indication to correct a TAVR-induced left bundle branch block (LBBB). METHODS: Patients qualifying for a permanent pacemaker implant after TAVR were planned for HBP implant. HBP was performed using the Select Secure (3830; Medtronic) pacing lead, delivered through a fixed curve or deflectable sheath (C315HIS or C304; Medtronic). Successful HBP was defined as selective or nonselective HBP, irrespective of LBB recruitment. Successful LBBB correction was defined as selective or nonselective HBP resulting in paced QRS morphology similar to pre-TAVR QRS and paced QRS duration (QRSd) less than 120 milliseconds with thresholds less than 3.0 V at 1.0-millisecond pulse width. RESULTS: The study enrolled 16 patients requiring a permanent pacemaker after TAVR (age 85 ± 4 years, 31% female, all LBBB; QRSd: 161 ± 14 milliseconds). Capture of the His bundle was achieved in 13 of 16 (81%) patients. HBP with LBBB correction was achieved in 11 of 16 (69%) and QRSd narrowed from 162 ± 14 to 99 ± 13 milliseconds and 134 ± 7 milliseconds during S-HBP and NS-HBP, respectively (P = .005). At implantation, mean threshold for LBBB correction was 1.9 ± 1.1 V at 1.0 millisecond. Thresholds remained stable at 11 ± 4 months follow-up (1.8 ± 0.9 V at 1.0 millisecond, P = .231 for comparison with implant thresholds). During HBP implant, one temporary complete atrioventricular block occurred. CONCLUSION: Permanent HBP is feasible in the majority of patients with TAVR requiring a permanent pacemaker with the potential to correct a TAVR-induced LBBB with acceptable pacing thresholds.

Impact of paced left ventricular dyssynchrony on left ventricular reverse remodeling after cardiac resynchronization therapy.

INTRODUCTION: We investigated whether pacing-induced electrical dyssynchrony at the time of cardiac resynchronization therapy (CRT) device implantation was associated with chronic CRT response. METHODS AND RESULTS: We included a total of 69 consecutive heart failure patients who received a CRT device. Left (LVp-RVs) and right (RVp-LVs) pacing-induced interlead delays were measured intraoperatively and used to determine if there was paced left ventricular (LV) dyssynchrony, defined as present when LVp-RVs is larger than RVp-LVs. CRT response was defined as a reduction in LV end-systolic volume ≥15%, 6 months after implantation. Paced left ventricular dyssynchrony (PLVD) was associated with ischemic cardiomyopathy (ICM) (χ2 : 8; P = .005) but not with QRS morphology nor with pacing lead positions. In a univariate analysis, PLVD (odds ratio [OR], 6.53; 95% confidence interval [CI], 2.2-18.9; P = .001), atypical left bundle branch block (LBBB) (OR, 3.3; 95% CI, 1.2-9.4; P = .022), and ICM (OR, 5.2; 95% CI, 1.6-17; P = .006) were associated with nonresponse. In a multivariate analysis, both PLVD (OR, 9.74; 95% CI, 2.8-33.9; P < .0001) and atypical LBBB (OR, 5.6; 95% CI, 1.5-20.3; P = .009) were independently associated with nonresponse. Adding PLVD to a model based on QRS morphology provided a significant and meaningful incremental value to predict LV reverse remodeling after CRT (χ2 to enter: 8; P < .005). Computer simulations corroborate these findings by showing that, while intrinsic electrical dyssynchrony is a prerequisite, the level of pacing-induced dyssynchrony modulates acute CRT response. CONCLUSION: In addition to the intrinsic electrical substrate, PLVD is strongly associated with less LV reverse remodeling, demonstrating that measuring the electrical substrate during pacing has additional value for prediction of CRT response in an already well-selected patient population.

Causes of impaired biventricular pacing in cardiac resynchronization devices with left ventricular sensing.

BACKGROUND: Loss of biventricular stimulation can result in nonresponse to cardiac resynchronization therapy (CRT). Problems associated with the left ventricular (LV) lead and LV sensing can be challenging to detect and their incidence is unclear. The purpose of this study was to investigate mechanisms of loss of biventricular pacing due to LV lead- and LV sensing-associated problems. METHODS: In this bicentric study, CRT patients were surveilled using a novel remote monitoring algorithm from Biotronik (Germany) that registers LV electrograms (EGMs) during intermittent loss of resynchronization. The episodes were analyzed to assess the mechanisms of resynchronization interruptions. RESULTS: We analyzed 582 EGMs from 61 patients. During a median follow-up of 6 months, 59% of the patients had such episodes. The majority of the episodes (61%) were related to inappropriate inhibition of LV pacing, mostly due to upper rate lock-in caused by LV sensing (58%). In contrast, 8% of episodes showed intermittent loss of LV capture, which was identified thanks to LV sensing. The remaining 31% of episodes were due to physiological reasons for resynchronization interruptions (eg, supraventricular tachycardia [18%], premature beats [8%], and others [5%]). Patients with CRT interruption episodes had lower resynchronization rates (median: 98.5% vs 100%, P = .044). CONCLUSIONS: Inadequate programming (active LV sensing with T-wave protection) is the main cause of impaired resynchronization in devices with LV sensing. In general, we recommend the deactivation of the LV T-wave protection function.

Should we still monitor QTc duration in frail older patients on low-dose haloperidol? A prospective observational cohort study.

BACKGROUND: Haloperidol at high dosage is associated with QTc prolongation and polymorphic ventricular arrhythmia but the effects of low-dose haloperidol remain unknown. OBJECTIVE: To evaluate the effects of low-dose haloperidol on QTc-duration in frail hospitalized elderly patients with delirium. METHODS: A prospective observational study including hospitalized patients aged ≥70 years with Groningen Frailty Index-score > 3. We included 150 patients who received haloperidol and 150 age- and frailty-matched control patients. Serial ECG recordings were performed at hospital admission and during hospitalization. QT-interval was corrected according to Framingham (QTc). Patients were grouped according to baseline QTc in normal (nQTc), borderline (bQTc) or abnormal (aQTc). Primary outcome was change in QTc-duration between first and second ECG. Potentially dangerous QTc was defined as QTc >500 ms or an increase of >50 ms. RESULTS: Patients in the haloperidol group (48% male, mean age 85y, nQT n = 98, bQT n = 31, aQT n = 20) received an average dose of 1.5 mg haloperidol per 24 hours. QTc decreased in patients with borderline (mean - 15 ± 29 ms, P < 0.05) or abnormal (-19 ± 27 ms, P < 0.05) QTc at baseline, no patients developed dangerous QTc-duration. In the control group (41% male, mean age 84y, nQT n = 99 bQT n = 29, aQT n = 22) QTc decreased to a similar extent (bQT -7 ± 16 ms, aQTc -23 ± 20 ms). CONCLUSION: A trend to QTc shortening was seen, especially in patients with borderline or abnormal QTc at baseline, regardless of haloperidol use. These findings suggest that ECG monitoring of frail elderly patients who receive low-dose haloperidol, may not be necessary.

Left ventricular sensing in cardiac resynchronization devices-opportunities and pitfalls for device programming.

INTRODUCTION: Some cardiac resynchronization therapy (CRT) device manufacturers (Biotronik, Germany; Boston Scientific, United States) have implemented left ventricular (LV) sensing functionality to prevent pacing into the vulnerable phase. Physicians are only partially aware of programming pitfalls related to LV sensing and general programming advice is lacking. METHODS AND RESULTS: We provide an illustrative case-series-based review of the variety of potential problems with LV sensing. LV sensing may inappropriately impair CRT delivery due to LV-sensing issues or improper device programming. This can cause beat-wise loss of resynchronization but also ongoing desynchronization. On the other hand, LV sensing provides additional diagnostic information, which may reveal intermittent problems of the LV lead such as capture loss. We summarize the available evidence to provide manufacturer-specific recommendations on device programming and troubleshooting for daily clinical practice. CONCLUSION: CRT devices with LV sensing may suffer from impaired resynchronization due to programming pitfalls. If LV sensing is active (nominal setting in Biotronik and Boston Scientific devices), careful lookout for related problems and resynchronization percentage is required. Optimization is mandatory and even deactivation of LV sensing may have to be considered.

Reducing right ventricular pacing burden: algorithms, benefits, and risks.

Algorithms designed to reduce the burden of right ventricular pacing are widely available in modern implantable pacing devices. To ensure safe and optimal utilization, understanding the properties of these algorithms as well as their possible unfavourable effects is essential. In this review, we discuss in detail the technical and clinical aspects of rhythm management algorithms and update on their significant recent modifications. In addition, we highlight possible adverse phenomena that may be induced by these different pacing algorithms intended to minimize pacing.