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Background: The impact of left bundle branch area pacing (LBBAP) on right ventricular (RV) function and tricuspid regurgitation (TR) remains unclear., Objective: We aimed to assess the long-term effects of LBBAP on RV performance and on TR., Methods: RV function was evaluated using RV free wall strain, tricuspid annular plane systolic excursion, fractional area changing, and systolic velocity of the lateral tricuspid annulus. The presence of reverse septal flash (RSF) and basal bulge (BB) was used to assess RV motion pattern. The distance between the lead entry site on the interventricular septum and the septal leaflet of the tricuspid annulus (lead-TV distance) was measured., Results: The analysis included 122 subjects [62 men (50.8%); mean age 76.5 ± 11.4 years] with a median follow-up of 21 months (18-24.5 months). During follow-up, RV free wall strain improved significantly (15.2 ± 5.8 vs 16.4 ± 5.5; P < .001) while tricuspid annular plane systolic excursion, systolic, and fractional area changing remained unchanged. Left ventricular ejection fraction was an independent predictor of improved RV function (B = 3.51; 95% confidence interval 1.39-8.9; P = .01). With LBBAP, RSF disappeared in 22 of 23 patients (96%) and BB in 15 of 22 patients (68%) in whom RSF and BB were present at baseline, respectively. RV function improvement was significantly higher when RSF was present at baseline (14 patients vs 11 patients; P = .02). At follow-up, no significant deterioration in TR occurred for the overall group. However, a lead-TV distance of <24.5 mm was associated with TR progression., Conclusion: LBBAP has a favorable impact on RV function. A basal LBBAP position is associated with worsening TR., Competing Interests: Disclosures Dr Burri has received institutional research and fellowship support and speaker fees from and serves on the advisory boards of Abbott, Biotronik, Boston Scientific, Medtronic, and MicroPort. Drs Jastrzębski and Moskal have received speaker and consultancy fees from Medtronic and Biotronik. The rest of the authors report no conflicts of interest., (Copyright © 2024 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Targets for right-sided conduction system pacing (CSP) include His bundle and right bundle branch. Electrocardiographic patterns, diagnostic criteria, and outcomes of right bundle branch pacing (RBBP) are not known., Objective: Our aims were to delineate electrocardiographic and electrophysiological characteristics of RBBP and to compare outcomes between RBBP and His bundle pacing (HBP)., Methods: Patients with confirmed right CSP were divided according to the conduction system potential to QRS complex interval at the pacing lead implantation site. Six hypothesized RBBP criteria as well as pacing parameters, echocardiographic outcomes, and all-cause mortality were analyzed., Results: All analyzed criteria discriminated between HBP and RBBP: double QRS complex transition during the threshold test, selective paced QRS complex different from conducted QRS complex, stimulus to selective-QRS complex > potential-QRS complex, small increase in V 6 R-wave peak time (V 6 RWPT) during QRS complex transition, equal capture thresholds of CSP and myocardium, and stimulus-V 6 RWPT > potential-V 6 RWPT (adopted as the diagnostic standard). According to the last criterion, RBBP was observed in 19.2% of patients (64 of 326) who had been targeted for HBP, present mainly among patients with potential to QRS complex interval <35 ms (90.6% [48 of 53]) and occasionally among the remaining patients (5.6% [16 of 273]). RBBP was characterized by longer QRS complex (by 10.5 ms), longer V 6 RWPT (by 11.6 ms), and better sensing (by 2.6 mV) compared with HBP. During a median follow-up duration of 29 months, no differences in capture threshold, echocardiographic outcomes, or mortality were found., Conclusion: RBBP has distinct features that separate it from HBP and is observed in approximately a fifth of patients in whom HBP is intended., (Copyright © 2023 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Pacing at sites of longest interventricular delay has been associated with greater reverse remodeling in cardiac resynchronization therapy (CRT). However, the effects of pacing at such sites on clinical outcomes is less well studied., Objective: The purpose of this study was to assess the association between interventricular delay and clinical outcomes in CRT patients implanted with quadripolar left ventricular (LV) leads., Methods: RALLY-X4 was a registry study of the Acuity X4 quadripolar LV leads. Interventricular delay was measured during unpaced basal rhythm from the right ventricular (RV) lead to the LV lead electrode (E1 to E4) chosen for CRT pacing. Patients were stratified by median RV-LV delay (80 ms) into short and long delay groups; they also were analyzed by multivariable modeling. The primary composite outcome measure was all-cause mortality and heart failure hospitalization (HFH) at 18 months., Results: A total of 581 patients had complete RV-LV delay data. Mean LV ejection fraction was 27%, and 73% had typical left bundle branch block. Predictors of long RV-LV delay included female sex, left bundle branch block, and QRS duration >150 ms. Survival free of the primary outcome at 18-month follow-up was 87% in the long activation delay group compared with 77% in the short delay group (P = .0042). Multivariate analysis showed that RV-LV delay was an independent predictor of survival free of HFH (P = .028)., Conclusion: Among CRT patients with quadripolar LV pacing leads, longer baseline interventricular activation delay was significantly associated with the composite endpoint of all-cause mortality and HFH., (Copyright © 2022 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Patients with atrial fibrillation (AF) often have sleep apnea (SA), but diagnosis of SA with polysomnography is costly. SA monitoring is a pacemaker feature that measures respiratory disturbance index, the sum of abnormal respiratory events divided by sleep duration., Objective: The purpose of this study was to evaluate the incidence and severity of SA and its association with AF in an unselected population fitted with pacemakers., Methods: RESPIRE (REgistry of Sleep APnea monItoring and Atrial Fibrillation in pacemakeR patients) was a multicenter, international, observational, open-label study following adult subjects for 18 months after implantation with an SA monitoring-enabled dual-chamber pacemaker. Severe SA was defined as average respiratory disturbance index ≥20 from implantation to follow-up visit. The first co-primary end point was the difference in significant AF (cumulative AF episodes lasting ≥24 hours over 2 consecutive days) between subjects with severe and those nonsevere SA at 12 months in the full analysis set (N = 553). The second co-primary end point was the rate of major serious adverse events at 18 months in the modified intention-to-treat set (N = 1024)., Results: Severe SA was detected in 31.1% (172 of 553). A higher incidence of significant AF was reported in patients with severe SA than in patients with nonsevere SA (25.0% vs 13.9%; difference 11.1%; 95% confidence interval 3.7%-18.4%; P = .002). Significant AF increased with time in both groups, but at a faster rate in the severe SA group. No intergroup difference in the overall rate of major serious adverse events was observed (P = .065)., Conclusion: SA screening over 12 months identified severe SA in almost one-third of unselected patients fitted with pacemakers. Severe SA was associated with a higher incidence of significant AF., (Copyright © 2019 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Programming of His-bundle pacing may be challenging because current implantable pulse generators are not specifically designed for this pacing modality., Objective: The purpose of this study was to evaluate electrical parameters in order to propose preset programming options with different configurations., Methods: Data were collected from 50 patients with His pacing leads connected to various ports (atrial, right ventricular, or left ventricular) of pacemakers and defibrillators during a detailed device interrogation, which included capture thresholds with various pacing vectors, measurement of timing intervals, and performance of automatic threshold algorithms., Results: His-bundle pacing thresholds were significantly lower during unipolar pacing compared to bipolar and extended bipolar polarities. However, current drain was offset due to lower impedance. The His pace-right ventricular sensed intervals were measured at 40-150 ms (mean 85 ± 25 ms), with the longest delays in patients with uncorrected right bundle branch block and selective His capture. This has implications for ventricular safety pacing windows (which were inactivated without evidence of crosstalk) and delays to minimize unnecessary ventricular backup pacing (which was also affected by refractory periods). The measured intervals also impacted the performance of automatic threshold algorithms, which performed differently depending on which port the His lead was connected to and did not distinguish between His and myocardial capture., Conclusion: Our report provides data that could serve to configure automated programming settings to simplify management of His-bundle pacing., (Copyright © 2019 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Patients with atrial flutter who are implanted with a pacemaker (PM) or implantable cardioverter-defibrillator (ICD) present with the opportunity to perform a noninvasive pacing study (NIPS) using the right atrial pacing lead to differentiate right from left atrial flutter., Objectives: The purpose of this study was to study the feasibility and accuracy of NIPS to distinguish right from left atrial flutter., Methods: We enrolled consecutive patients scheduled for an electrophysiological study or ablation procedure who were in atrial flutter and who were implanted with a PM or ICD with a functional atrial lead in the right atrial appendage. Flutter tachycardia cycle lengths (TCLs) and postpacing intervals (PPIs) were measured noninvasively via the device during the procedure., Results: A total of 48 (67%) patients were studied. Right atrial flutter was present in 32 patients (of whom 29 had typical cavotricuspid isthmus-dependent flutter) and 16 (33%) patients had left atrial flutter. A PPI-TCL interval of >100 ms was 100% specific and 81% sensitive to identify left atrial flutter, with an overall accuracy of 94% and a c statistic of 0.94 (95% confidence interval 0.87-1.00). A PPI-TCL interval of ≤100 ms had a positive predictive value of 86% for diagnosing typical flutter., Conclusion: NIPS via PMs and ICDs with a PPI-TCL interval of >100 ms can reliably identify left atrial flutter (although we have only validated this cutoff for leads implanted in the right atrial appendage). This simple maneuver may allow planning for left-sided access and may avoid an unnecessary invasive electrophysiological study if left atrial flutter ablation is not to be considered., (Copyright © 2015 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Far-field extra-pulmonary vein (PV) potentials originating from the left atrial appendage and adjacent left atrium have been identified within the left PVs, but no systematic study of extra-PV potentials within the right superior PV (RSPV) has been described., Objectives: The purpose of this study was to prospectively analyze extra-PV contributions to RSPV potentials., Methods: In a consecutive, prospective series of 114 patients (96 men and 18 women; 56 +/- 10 years) undergoing electrophysiologically guided ostial PV isolation, residual potentials recorded with a circular mapping catheter in the RSPV after ostial isolation were analyzed. Their extra-PV origin was validated by mapping a site with identical timing (in sinus rhythm or atrial fibrillation) within the adjacent superior vena cava (SVC) where, in sinus rhythm, local pacing (until threshold amplitude) concealed the residual potential within the stimulus artifact because of very short activation timing. The timing of residual potentials with respect to surface ECG P-wave onset was measured and compared with the earliest timing of ablated RSPV potentials., Results: Residual low-amplitude (mean 0.29 +/- 0.17 mV, range 0.07-0.65 mV) extra-PV potentials were recorded from the anterior and superior aspect of the RSPV in 3.6 +/- 1 bipoles in 26 (23%) patients (all men, 51 +/- 10 years) with a timing from sinus P-wave onset of 17 +/- 12 ms (range 0-40 ms) vs 52 +/- 9 ms (range 35-70 ms) for the earliest RSPV potential (P <.001, t-test). Extra-PV potentials all originated from the posterior aspect of the SVC. The SVC potential was identified during ongoing atrial fibrillation in eight patients and later confirmed in sinus rhythm. An extra-PV potential of SVC origin could be identified by timing earlier than 30 ms from onset of the sinus P wave, with sensitivity of 92%, specificity 100%, positive predictive value 100%, and negative predictive value 89%., Conclusion: Extra-PV potentials of right-sided SVC origin were recorded within the RSPV in 23% of patients and can be identified with high sensitivity and specificity by a timing within 30 ms of sinus P-wave onset. Recognizing these potentials can avoid unnecessary additional ablation and possibly PV stenosis or phrenic paralysis.

Echocardiography has been the focus of growing interest for improving patient selection for cardiac resynchronization therapy in order to reduce the number of nonresponders. Various techniques have been described for assessing dyssynchrony, using standard echocardiography (pulsed-wave Doppler and M-mode echocardiography), tissue Doppler imaging, and other imaging modes such as three-dimensional echocardiography. This article provides an overview of the technical and practical aspects of these different techniques and discusses the current evidence for optimizing patient selection by echocardiography.

Background: Biventricular pacemakers are usually programmed with the default setting of synchronous biventricular pacing, although the ventricles may be paced sequentially. Whether this parameter is important for optimizing resynchronization therapy is not clear., Objectives: The purpose of this study was to investigate whether sequential pacing acutely improves left ventricular ejection fraction (LVEF) and dyssynchrony and to assess the feasibility of nuclear ventriculography for device optimization., Methods: Twenty-seven patients implanted with a biventricular pacemaker or implantable cardioverter-defibrillator for heart failure were studied. LVEF was measured using planar radionuclide ventriculography during simultaneous biventricular pacing and during sequential pacing at four different interventricular intervals ranging from LV-40 (preexciting the left ventricle by 40 ms) to LV+40 (preexciting the right ventricle). Interventricular and intraventricular dyssynchrony were analyzed by phase analysis at each setting., Results: There was great heterogeneity in individual response to VV interval programming. Twenty-four of 27 patients (89%) had significant changes (both favorable and unfavorable) in LVEF at different interventricular delays, with variations of up to 10% in absolute terms. Simultaneous biventricular pacing yielded maximal LVEF in 9 of 27 patients (33%), with a relative increase in LVEF of 18 +/- 14% by optimized sequential pacing in the remaining patients. Interventricular dyssynchrony varied significantly, with least dyssynchrony at the LV-20 setting (P = .024). There were no significant differences in intraventricular dyssynchrony at the different settings., Conclusion: Programming VV intervals has considerable impact on LVEF. However, there is a great degree of variation between patients in response to these settings, requiring individual assessment for device optimization.

Objectives: To quantify and study the distribution of innervation of the left atrium and the pulmonary veins in humans., Background: Damage to cardiac nerves has been hypothesized as the explanation for successful radiofrequency ablation of atrial fibrillation., Methods: From January 2003 to September 2003, histologic and quantitative studies of innervation of the left atrium and the pulmonary veins was performed in 43 consecutive necropsied adult hearts (30 men and 3 women; mean age 45.5 +/- 12.4 years). The left atrium was sectioned in 1-cm slices from left to right, with the plane of section perpendicular to the long axis of the heart. Sections of the pulmonary veins at their ostia and sections 1 cm away of this structure also were obtained. Nerve fiber density was counted manually for each case and expressed as the mean number per slice., Results: Numerous epicardial nerve fibers and ganglia having distinct patterns of distribution in the left atrium were found. Nerve density was significantly higher at the ostia of the four pulmonary veins than in their distal part (7.1 +/- 2.1 vs 5.2 +/- 1.3 for left upper pulmonary vein; 6.3 +/- 1.5 vs 5.2 +/- 1.7 for right upper pulmonary vein; 7.4 +/- 2 vs 5.9 +/- 2 for left lower pulmonary vein; 6.7 +/- 1.8 vs 3.9 +/- 1.3 for right lower pulmonary vein). The left superior vein was significantly more innervated than the right inferior vein (12.3 +/- 3 vs 10.6 +/- 1.4). Gradients of innervation were found from right to left (9.8 +/- 4.6 vs 18.5 +/- 6.6, P < .05) and from the front to the rear of the atrium (17.2 +/- 6.4 vs 20.7 +/- 6.5, P < .05). The same heterogeneous distribution was observed at the myocardial level but with thinner nerve fibers, making quantification difficult. Only very thin nerve fibers were present in the endocardium., Conclusions: The human left atrium exhibits several gradients of innervation at discrete sites. These findings may have clinical implications for radiofrequency ablation of atrial fibrillation.