Difference In QRS Duration Research Articles

Time-dependent activation and repolarization changes following left bundle branch area pacing versus conventional biventricular pacing in patients with dyssynchronous heart failure

Abstract Background Cardiac Resynchronization Therapy (CRT) is the standard treatment for patients with dyssynchronous heart failure. Despite the effectiveness of conventional biventricular pacing (BiVP), 6-16% of patients develop ventricular tachyarrhythmias (VTAs) within a year of implantation. The relationship between BiVP and the development of VTAs is still under debate. During BiVP, the left-sided epicardium-to-endocardium activation creates a non-physiological activation and hence a non-physiological repolarization, which might trigger VTAs. A novel alternative treatment option to BiVP that on the contrary induces a left ventricular endocardium-to-epicardium activation, is left bundle branch area pacing (LBBAP). We hypothesized that LBBAP leads to a more homogenous repolarization than conventional BiVP. Purpose To compare time-dependent activation and repolarization changes in patients with dyssynchronous heart failure receiving LBBAP versus BiVP. Methods Patients eligible for CRT who underwent LBBAP (n=21) or BiVP (n=94) were retrospectively included. Standard 12-lead electrocardiograms obtained prior to implantation [baseline], shortly following implantation (0-2 days, [acute phase]), and after prolonged pacing during follow-up (31-180 days, [chronic phase]) were analyzed. QRS duration and QRS area were calculated through reconstruction of the vectorcardiogram and further analyzed together with corrected QT (QTc) and corrected Tpeak-Tend (Tp-e,c) intervals using a semi-automatic approach in MATLAB. Differences between LBBAP and BiVP patients were determined using the Mann-Whitney U-test. Time-dependent changes within groups were determined using the Wilcoxon signed-rank tests. Significance was defined as a p-value ≤0.05. Results (see figure): Compared to baseline, QRS duration and QRS area decreased significantly during the acute phase (both p < 0.01) and stabilized during chronic pacing for both BiVP and LBBAP patients. Differences in QRS duration or QRS area between LBBAP and BiVP were not significant at any of the time points. In the acute phase, BiVP resulted in a temporary and significant prolongation of both QTc and Tp-e,c compared to baseline (both p < 0.01). However, there was a subsequent shortening observed between the acute and chronic phases for both QTc and Tp-e,c (both p < 0.01). Compared to baseline, LBBAP acutely shortened Tp-e,c (p = 0.02) and tended to shorten QTc. During chronic pacing, LBBAP shortened QTc and Tp-e,c compared to baseline (p = 0.01 and p < 0.01). The decreases in QTc and Tp-e,c were larger in LBBAP than in BiVP patients in the acute and chronic pacing phase (all p <0.01). Conclusion CRT induces activation changes in both BiVP and LBBAP patients to a comparable extent. While BiVP leads to an acute increase in repolarization dispersions, LBBAP reduces markers of repolarization dispersion compared to baseline. The diminished dispersion of repolarization might contribute to an antiarrhythmic effect with LBBAP.

Endocardial pacing compared to epicardial left ventricle pacing and right ventricle pacing: A single-center long-term experience in a pediatric population

Background and aimsPediatric pacing is usually performed as epicardial pacing in small children in need of pacemaker therapy. Epicardial pacing compared with transvenous pacing for pediatric complete atrioventricular block (CAVB) has different strengths and weaknesses. The epicardial left ventricular wall position of the lead has been considered superior, in terms of contraction pattern, compared to a transvenous right ventricular stimulation. We aimed to compare QRS duration and cardiac function before and after the switch from epicardial to transvenous pacing in a pediatric population. MethodsPediatric patients with congenital or acquired CAVB, who underwent a switch from epicardial-to transvenous pacing at our center from 2005 to 2021, were identified through the national ICD- and Pacemaker Registry. Data regarding clinical status, ECG, and echocardiography before and after the switch and at last follow-up were collected. ResultsWe included 15 children. The median age at the switch was 6.7 (4.4–11.7) years with a median weight of 21 (15–39) Kg. The median QRS duration with the transvenous systems was 136 (128–152) ms vs. a QRS duration during epicardial stimulation of 150 (144–170) ms with a median difference in QRS duration of 14 (6–20) ms. Children with a post-surgical AV block had a broader QRS duration, both with epicardial and endocardial stimulation. Before the switch, there was one patient with impaired left ventricular function (LVF) but with normal left ventricular end-diastolic diameters. After the switch, one patient developed symptomatic LV dysfunction with the recovery of LVF at the last follow-up after being implanted with a cardiac resynchronization therapy device. ConclusionsOur report of pediatric patients after switching from epicardial to transvenous pacing shows how transvenous pacing is not inferior to epicardial pacing in terms of QRS duration and no significant deterioration of cardiac function was detectable.

Left ventricular anterolateral site is the preferable left ventricular lead position for an upgrade to biventricular pacing

Abstract Background Cardiac resynchronization therapy (CRT) is a well-established treatment for symptomatic heart failure with electrical dyssynchrony. The LV lead position in patients with left bundle branch block is usually recommended at the LV posterolateral to the lateral site, which is the latest electrical activation site. In contrast, the preferable LV lead position in patients who plan to upgrade from conventional RV apical pacing to CRT remains unclear. Purpose This study aimed to identify the preferable LV lead position for upgrading to CRT from conventional RV apical pacing. Methods An electrophysiological study was performed on patients who underwent ablation for atrial fibrillation. The electrode catheters were positioned at the RV apex, LV anterolateral, and LV posterolateral sites via the coronary sinus branches. During RV apical pacing, the activation time from the RV apex to the LV anterolateral and posterolateral sites was measured, and the activation time ratio to QRS duration was calculated. Biventricular pacing from both the RV apex and LV anterolateral or LV posterolateral sites was performed, and the difference in QRS duration and LV dP/dt compared to only the RV apical pacing state was measured. Results We enrolled 37 patients who exhibited anterolateral and posterolateral LV coronary sinus branches. During RV apical pacing, the average activation time ratio to QRS duration was higher at the LV anterolateral site than at the LV posterolateral site (0.89±0.07 vs. 0.71±0.11, P <0.001). The shortening ratio of QRS duration during biventricular pacing compared to baseline RV apical pacing was greater at LV anterolateral site than at the LV posterolateral site (45.7±18.0% vs. 32.0±17.6%, P <0.001). The improvement ratio of LV dP/dt during biventricular pacing was also better from the LV anterolateral site than from the LV posterolateral site (12.7±8.9% vs. 3.7±8.2%, P <0.001). Conclusion LV lead position in patients who plan to upgrade to CRT from conventional RV apical pacing is preferably at the LV anterolateral site.

A Comparative Assessment of Myocardial Work Performance during Spontaneous Rhythm, His Bundle Pacing, and Left Bundle Branch Area Pacing: Insights from the EMPATHY Study.

Physiological pacing has gained significant interest due to its potential to achieve optimal hemodynamic response. This study aimed to assess left ventricular performance in terms of electrical parameters, specifically QRS duration and mechanical performance, evaluated as myocardial work. We compared His Bundle Pacing (HBP) and Left Bundle Branch Area Pacing (LBBAP) to evaluate their effects. Twenty-four patients with class I or IIa indications for pacing were enrolled in this study, with twelve patients undergoing HBP implantation and another twelve undergoing LBBAP implantation. A comprehensive analysis of myocardial work was conducted. Our findings indicate that there were no major differences in terms of spontaneous and HBP activation in myocardial work, except for global wasted work (217 mmHg% vs. 283 mmHg%; p 0.016) and global work efficiency (87 mmHg% vs. 82 mmHg%; p 0.049). No significant differences were observed in myocardial work between spontaneous activation and LBBAP. Similarly, no significant differences in myocardial work were found between HBP and LBBAP. Both pacing modalities provide physiological ventricular activation without significant differences when compared to each other. Moreover, there were no significant differences in QRS duration between HBP and LBBAP. However, LBBAP demonstrated advantages in terms of feasibility, as it achieved better lead electrical parameters compared to HBP (threshold@0.4 ms 0.6 V vs. 1 V; p = 0.045-sensing 9.4 mV vs. 2.4 mV; p < 0.001). Additionally, LBBAP required less fluoroscopy time (6 min vs. 13 min; p = 0.010) and procedural time (81 min vs. 125 min; p = 0.004) compared to HBP.

Comparison of electrocardiographic parameters between left bundle optimized cardiac resynchronization therapy (LOT-CRT) and left bundle branch pacing-cardiac resynchronization therapy (LBBP-CRT).

In patients undergoing cardiac resynchronization therapy using left bundle branch area pacing (LBBP-CRT), the addition of a coronary sinus lead, that is, Left bundle optimized CRT (LOT-CRT) might confer additional benefits. To compare the electrocardiographic characteristics between LBBP-CRT and LOT-CRT MATERIALS AND METHODS: Patients with non-ischemic cardiomyopathy (NICMP) and left bundle branch block (LBBB) with left ventricular ejection fraction<35% who underwent implantation of an atrial lead, a left bundle lead, and a coronary sinus lead were included in this prospective study. Digital 12-lead electrocardiograms were recorded in three pacing modes-AAI, DDD with pacing from the LBB lead (LBBP-CRT), and DDD with pacing from both left bundle and coronary sinus leads (LOT-CRT). QRS duration (QRSd), QRS area, QT interval, and T peak-T end (TpTe) intervals were compared. Among 24 patients, QRSd reduced from 167±21.2ms to 134.5±23.6ms with LBBP-CRT (p<.001) and 129.5±18.6ms with LOT-CRT (p<.001) without a significant difference between LBBP-CRT and LOT-CRT (p=.15). Patients with QRS duration with LBBP-CRT>131ms showed a significant reduction in QRSd with LOT-CRT (p=.03). QT interval was reduced with both modes of CRT. LOT-CRT was associated with a greater reduction in QRS area (p=.001), TpTe interval (p=.03), and TpTe/QT ratio (p=.013) compared to LBBP-CRT. In patients with NICMP and LBBB, there was no significant difference in QRSd with LOT-CRT compared to LBBP-CRT. However, in patients with QRSd>131ms after LBBP-CRT, LOT-CRT resulted in a significantly narrower QRS.

Preferred left ventricular lead position for upgrade from right ventricular pacing to cardiac resynchronization therapy.

Cardiac resynchronization therapy (CRT) is well-established for treating symptomatic heart failure with electrical dyssynchrony. The left ventricular (LV) lead position is recommended at LV posterolateral to lateral sites in patients with left bundle branch block; however, its preferred region remains unclear in patients being upgraded from right ventricular (RV) apical pacing to CRT. This study aimed to identify the preferred LV lead position for upgrading conventional RV apical pacing to CRT. We used electrode catheters positioned at the RV apex and LV anterolateral and posterolateral sites via the coronary sinus (CS) branches to measure the ratio of activation time to QRS duration from the RV apex to the LV anterolateral and posterolateral sites during RV apical pacing. Simultaneous biventricular pacing was performed at the RV apex and each LV site, and the differences in QRS duration and LV dP/dtmax from those of RV apical pacing were measured. Thirty-seven patients with anterolateral and posterolateral LV CS branches were included. During RV apical pacing, the average ratio of activation time to QRS duration was higher at the LV anterolateral site than at the LV posterolateral site (0.90 ± 0.06 vs. 0.71 ± 0.11, p < .001). The decreasing ratio of QRS duration and the increasing ratio of LV dP/dtmax were higher at the LV anterolateral site than at the posterolateral site (45.7 ± 18.0% vs. 32.0 ± 17.6%, p < .001; 12.7 ± 2.9% vs. 3.7 ± 8.2%, p < .001, respectively) during biventricular pacing compared with RV apical pacing. The LV anterolateral site is the preferred LV lead position in patients being upgraded from conventional RV apical pacing to CRT.

Initial studies on the implanting sites of high and low ventricular septa using leadless cardiac pacemakers.

To study the safety and electrical characteristics of various implanting sites of the Micra pacemaker. A total of 15 patients from Beijing Anzhen Hospital, Capital Medical University, were included, who were implanted with Micra leadless pacemakers and allocated to either the high ventricular septum group (eight patients) or the low ventricular septum group (seven patients) based on their individual patient factors and clinical conditions. The baseline of the patients, the implanting area, the electrocardiogram change after implantation, the implantation data, the threshold, R wave, impedance, and the date of the 1-month follow-up were then analyzed. With all of the data, the characteristics of different implantation sites of the Micra pacemaker were determined. Overall, the thresholds were low at implantation and remained stable over the 1-, 3-, 6-month, 1-, 2-, 3-, and 4-year follow-ups. On comparing the two groups, there was no difference in QRS duration at pacing (140.00 [40.00] ms vs. 179.00 [50.00] ms), threshold at implantation (0.38 [0.22] mV vs. 0.63 [1.00] mV), R wave at implantation ([10.85 ± 4.71] V vs. [7.26 ± 2.98] V), or impedance at implantation ([906.25 ± 162.39] Ω vs. [750.00 ± 173.40] Ω). While the difference in QRS duration between the two groups was not significant, the QRS duration of the high ventricular septum group exhibited a reduced tendency compared with that of the low ventricular group. The corrected QT interval during pacing exhibited a significant difference (440.00 [80.00] ms vs. 520.00 [100.00] ms; p < .05). For the 1-, 3-, 6-month, 1-, 2-, 3-, and 4-year follow-ups, there was no difference between the threshold of the high ventricular septum group and that of the low ventricular septum group (p > .05). High ventricular septum pacing appears to be a safe site for implantation of the Micra pacemaker. It could entail a shorter QRS duration at pacing and could be more physiological than low ventricular septum pacing.

Cardiac digital twins of the adult population: linking electrophysiological functions to anatomy

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): This project is supported by the Wellcome Trust and EPSRC Centre for Medical Engineering. Background QRS duration derived from 12-lead ECGs provides an estimate of the ventricular depolarization time and is an important metric to assess cardiac function. The QRS duration is determined in part by the combination of heart size and conduction velocity (CV). Differences in QRS duration in terms of gender, body mass index (BMI) and age have been well-documented, however, the relative impact of concurrent changes in heart size and CV on QRS duration is poorly understood. Cardiac digital twins, as in-silico replicas, provide a non-invasive physics and physiology-constrained framework to separate the impact of CV and heart anatomy on the QRS duration across populations. Purpose This study aims to identify the impact of CV and heart size on differences in QRS duration and quantify their difference in the general population in different groups of gender, BMI and age. Methods Patient-specific biventricular models (n=400) were constructed using long- and short-axis cardiac magnetic resonance (CMR) images from patients without self-reported cardiovascular diseases in the UK Biobank. Cardiac electrophysiology was simulated using a physiological-detailed model that includes fiber orientation, anisotropic conductivity, the His-Purkinje system activation, and fast endocardial conductivity[1]. 12-lead ECGs were reconstructed from the simulations and the QRS duration was computed based on corresponding vectorcardiogram (VCG) reconstructed from ECG data [2]. We calibrated patient-specific CVs to match the clinically measured QRS duration in ECGs at rest and then compare the heart size, QRS duration and estimated CVs for different patient groups. Results QRS duration was approx. 7% longer in males than females (median: 90ms vs 84ms, P&amp;lt;0.001). Consistent with a longer QRS duration in males had larger hearts (male: 165.5 mL vs 123 mL, P&amp;lt;0.001), while the median CVs were the same between genders (both: 0.594 m/s). QRS duration was longer for obese (BMI≥30) and overweight group compared to healthy (BMI&amp;lt;25) groups (88ms and 86 ms vs 84 ms, P=0.05 and 0.3). Again, the change in QRS duration with BMI was reflected with a corresponding increase in heart size (healthy: 127 mL, overweight: 147.6 mL, obese:160 mL), while CV remained unchanged (healthy: 0.58 m/s vs overweight and obese: 0.594 m/s, P=0.051 and 0.32). There was no significant difference in QRS duration, CV or myocardial volume for different age groups (medians: 86-88 ms and 0.573-0.594 m/s and 138.7-143 mL). Conclusions QRS duration is shorter in females and individuals with healthy weights. Most of the change in QRS duration can be explained by heart size, with the estimated CV remaining consistent across groups.

Left bundle branch area pacing results in more physiological ventricular activation than biventricular pacing in patients with left bundle branch block heart failure.

Biventricular pacing (Biv) and left bundle branch area pacing (LBBAP) are methods of cardiac resynchronization therapy (CRT). Currently, little is known about how they differ in terms of ventricular activation. This study compared ventricular activation patterns in left bundle branch block (LBBB) heart failure patients using an ultra-high-frequency electrocardiography (UHF-ECG). This was a retrospective analysis including 80 CRT patients from two centres. UHF-ECG data were obtained during LBBB, LBBAP, and Biv. Left bundle branch area pacing patients were divided into non-selective left bundle branch pacing (NSLBBP) or left ventricular septal pacing (LVSP) and into groups with V6 R-wave peak times (V6RWPT) < 90 ms and ≥ 90 ms. Calculated parameters were: e-DYS (time difference between the first and last activation in V1-V8 leads) and Vdmean (average of V1-V8 local depolarization durations). In LBBB patients (n = 80) indicated for CRT, spontaneous rhythms were compared with Biv (39) and LBBAP rhythms (64). Although both Biv and LBBAP significantly reduced QRS duration (QRSd) compared with LBBB (from 172 to 148 and 152 ms, respectively, both P < 0.001), the difference between them was not significant (P = 0.2). Left bundle branch area pacing led to shorter e-DYS (24 ms) than Biv (33 ms; P = 0.008) and shorter Vdmean (53 vs. 59 ms; P = 0.003). No differences in QRSd, e-DYS, or Vdmean were found between NSLBBP, LVSP, and LBBAP with paced V6RWPTs < 90 and ≥ 90 ms. Both Biv CRT and LBBAP significantly reduce ventricular dyssynchrony in CRT patients with LBBB. Left bundle branch area pacing is associated with more physiological ventricular activation.

Electrophysiologic effects of left bundle branch area pacing: comparing left ventricular septal pacing and left bundle branch pacing

Abstract Funding Acknowledgements Type of funding sources: Private company. Main funding source(s): Medtronic Background Left bundle branch area pacing(LBBAP) has been introduced as a more physiological pacing alternative to anti-bradycardia pacing and as an alternative to biventricular pacing in cardiac resynchronization therapy (CRT). LBBAP is the common denominator of left ventricular septal pacing(LVSP) and left bundle branch pacing(LBBP). In LVSP, there is only capture of the myocardium on the left side of the interventricular septum, whereas in LBBP there is additional capture of the left bundle branch(LBB) and subsequent Purkinje fibers. Purpose To investigate the electrophysiological differences between LBBP and LVSP. Methods Patients with a permanent pacemaker indication due to bradycardia or heart failure according to current guidelines were included and underwent LBBAP implantation. At baseline and during implantation, electrical activation parameters were recorded pacing at different sites (Right ventricle, LVSP and LBBP), using the standard 12-lead ECG and the ECG BELT. Electrophysiologic measures included: QRS duration, QRSarea calculated from the vectorcardiogram after conversion from the ECG using the Kors matrix, and standard deviation of activation time(SDAT) measured through the ECG BELT. Both QRS area and SDAT are known markers of ventricular dyssynchrony. Results 28 patients (17 male), with an age of 67±7 yrs underwent LBBAP. 21(75%) had a pacing indication for bradycardia with a baseline narrow QRS and 7(25%) for heart failure with a baseline LBBB. In 17 patients (61%) LBB capture was achieved. The remaining patients were treated with LVSP. In patients with baseline narrow QRS, both LVSP and LBBP showed a significant increase in QRS duration(p&amp;lt;0.001, p&amp;lt;0.001 resp.), without a significant difference in QRS duration between LVSP and LBBP(fig. 1 A). There was no significant difference in SDAT between LVSP and LBBP compared to baseline narrow QRS, and a significant SDAT reduction in patients with underlying LBBB (p=0.005, p&amp;lt;0.001 resp.) Furthermore, there was no significant SDAT difference between LVSP and LBBP(fig. 1 B). LVSP showed a small but significant increase in QRSarea compared to baseline narrow QRS (p=0.011) where LBBP showed no difference compared to baseline narrow QRS. Compared to baseline LBBB both LVSP and LBBP showed a significant QRSarea reduction (p=0.003, p&amp;lt;0.001 resp.). Moreover, there was a small but significant reduction in QRSarea when LBBP was achieved over LVSP(p=0.044) (fig. 1 C). Conclusion LVSP and LBBP showed a similar effect on ventricular synchrony in terms of SDAT, with levels of synchrony comparable to normal physiologic activation. Left bundle branch capture resulted in a small, but significant improvement in QRSarea over LVSP. Fig. 1 Relative changes in QRS duration(A), SDAT (B) and QRS area (C) compared to baseline narrow QRS (bradypacing) and baseline heart failure with LBBB. *p&amp;lt;0.05 compared to baseline, **p&amp;lt;0.05 for bradypacing and heart failure with LBBB combined.

Prediction of response to cardiac resynchronization therapy using cardiac magnetic resonance imaging in non-ischemic dilated cardiomyopathy

Abstract Background Cardiac resynchronization therapy (CRT) is a well-established therapy for symptomatic heart failure with reduced ejection fraction, but the response is different for individuals. Although many modalities have been conducted to predict CRT response, cardiac magnetic resonance (CMR) to predict CRT response has still insufficient usefulness. Purpose We determine whether the parameters including late gadolinium enhancement (LGE) identified in CMR could act as predictors of CRT response. Methods We retrospectively investigated 124 patients with non-ischemic dilated cardiomyopathy who underwent CMR before CRT implantation between Jan 2010 and July 2021 in a single center. CRT response was defined as a decrease in left ventricular end-systolic volume (LVESV) &amp;gt;15% on echocardiography after at least 3 months after CRT implantation. Results Among the study population (mean age 65.7±11.2 years, mean EF 25±6.5%, 50% of female), 85 (69%) patients were defined as CRT responder. The CRT responders had more left bundle branch block (LBBB) compared with non-responders [79 (92.9%) vs. 23 (59.0%), p&amp;lt;0.001], but there was a no difference of QRS duration (158.7 vs 165.0ms, p=0.054) between two groups. CMR analysis showed that there were no significant differences in the left ventricular (LV) chamber volume and LV ejection fraction between CRT-responder and non-responder. However, the right ventricular (RV) chamber volume was smaller (RV end-diastolic volume index, 86.3 vs 103.5 ml/m2, p=0.039; RV end-systolic volume index, 49.3 vs 68.5 ml/m2, p=0.013) and the RV ejection fraction (RVEF) was higher (46.9 vs 37.6%, p=0.002) in CRT-responders compared with non-responders. The LGE on CMR was more shown in non-responders than in CRT-responders [33 (84.6%) vs 45 (52.9%), p&amp;lt;0.001]. In CMR parameters, RV dysfunction (RVEF &amp;lt;45%) [Odds ratio (OR), 0.21 (0.05–0.93), p=0.045] and LGE [OR, 0.21 (0.05–0.58), p=0.01] were significantly associated with poor CRT response. Conclusions The presence of LGE and RV dysfunction on CMR were associated with poor CRT response in patients with non-ischemic dilated cardiomyopathy. Further investigation with CMR for pre-CRT patients is needed to support these results. Funding Acknowledgement Type of funding sources: None.

Determinants of the time-to-peak left ventricular dP/dt (Td) and QRS duration with different fusion strategies in cardiac resynchronization therapy.

BackgroundCardiac resynchronization therapy (CRT) is helpful in selected patients; however, responder rates rarely exceed 70%. Optimization of CRT may therefore benefit a large number of patients. Time-to-peak dP/dt (Td) is a novel marker of myocardial synergy that reflects the degree of myocardial dyssynchrony with the potential to guide and optimize treatment with CRT. Optimal electrical activation is a prerequisite for CRT to be effective. Electrical activation can be altered by changing the electrical wave-front fusion resulting from pacing to optimize resynchronization. We designed this study to understand the acute effects of different electrical wave-front fusion strategies and LV pre-/postexcitation on Td and QRS duration (QRSd). A better understanding of measuring and optimizing resynchronization can help improve the benefits of CRT.MethodsTd and QRSd were measured in 19 patients undergoing a CRT implantation. Two biventricular pacing groups were compared: pacing the left ventricle (LV) with fusion with intrinsic right ventricular activation (FUSION group) and pacing the LV and right ventricle (RV) at short atrioventricular delay (STANDARD group) to avoid fusion with intrinsic RV activation. A quadripolar LV lead enabled pacing from widely separated electrodes; distal (DIST), proximal (PROX) and both electrodes combined (multipoint pacing, MPP). The LV was stimulated relative in time to RV activation (either RV pace-onset or QRS-onset), with the LV stimulated prior to (PRE), simultaneous with (SIM) or after (POST) RV activation. In addition, we analyzed the interactions of the two groups (FUSION/STANDARD) with three different electrode configurations (DIST, PROX, MPP), each paced with three different degrees of LV pre-/postexcitation (PRE, SIM, POST) in a statistical model.ResultsWe found that FUSION provided shorter Td and QRSd than STANDARD, MPP provided shorter Td and QRSd than DIST and PROX, and SIM provided both the shortest QRSd and Td compared to PRE and POST. The interaction analysis revealed that pacing MPP with fusion with intrinsic RV activation simultaneous with the onset of the QRS complex (MPP*FUSION*SIM) shortened QRSd and Td the most compared to all other modes and configurations. The difference in QRSd and Td from their respective references were significantly correlated (β = 1, R = 0.9, p < 0.01).ConclusionPacing modes and electrode configurations designed to optimize electrical wave-front fusion (intrinsic RV activation, LV multipoint pacing and simultaneous RV and LV activation) shorten QRSd and Td the most. As demonstrated in this study, electrical and mechanical measures of resynchronization are highly correlated. Therefore, Td can potentially serve as a marker for CRT optimization.

Comparison between his-bundle pacing and biventricular pacing as cardiac resynchronization therapy for heart failure patients: a systematic review and meta-analysis

Abstract Funding Acknowledgements Type of funding sources: None. Background Cardiac resynchronization therapy (CRT) has demonstrated significant improvements in cardiovascular outcomes of selected heart failure patients. However, conventional biventricular CRT implantation can be challenging due to unfavorable coronary sinus anatomy, leads to lead instability, poor capture, and insufficient cardiac resynchronization. His-bundle pacing has gained interest as alternative strategy for patients underwent biventricular CRT implantation when coronary sinus lead implantation is unsuccesful or in non-responder cases. Purpose This study aims to compare the efficacy of his-bundle pacing and biventricular pacing in improving electrocardiographic, echocardiographic, and clinical parameters of heart failure patients that required resynchronization therapy. Methods A search for eligible studies was conducted until August 2021 on three databases (PubMed, ScienceDirect, ProQuest). Included studies were evaluated for risk of bias. Our primary outcomes of interest were mean difference in QRS duration, left ventricular ejection fraction (LVEF), and change in systolic blood pressure (SBP). We also investigated left ventricular activation time, left ventricular dyssynchrony index, left ventricular end-systolic volume (LVESV), New York Heart Association (NYHA) functional class, 6-minute walk test, quality of life, heart failure hospitalization and cardiovascular or all cause death. Review Manager (RevMan) 5.4 was utilized to compute mean differences. Results We identified five studies from 2010 to 2019, involving 95 heart failure patients underwent CRT implantation. Pooled analysis showed that his-bundle pacing resulted in significant narrowing of QRS duration compared to biventricular pacing [Mean Difference -23.17 ms (95% CI -36.10, -10.24; p=0.0004; I2=0.63)]. Left ventricular activation time and left ventricular dyssynchrony index were significantly improved in his bundle pacing. There were no significant differences of changes in LVEF, LVESV, and SBP. Clinical parameters such as NYHA functional class, 6-minute walk test, and quality of life were significantly improved in both pacing modality. No significant difference in heart failure hospitalization and cardiovascular or all cause mortality. Conclusion His-bundle pacing delivers better decrease of QRS duration, also reduction in left ventricular activation time and left ventricular dyssynchrony index compared to biventricular pacing. These suggests that his-bundle pacing is a reasonable alternative option for cardiac resynchronization therapy.

Determinants of LV dP/dtmax and QRS duration with different fusion strategies in cardiac resynchronisation therapy

BackgroundWe designed this study to assess the acute effects of different fusion strategies and left ventricular (LV) pre-excitation/post-excitation on LV dP/dtmax and QRS duration (QRSd).MethodsWe measured LV dP/dtmax and QRSd...

R/S Ratio in Lead III Predicts Successful Ablation of Ventricular Arrhythmias Originating in Para-Hisian Region

The aim of this study was to investigate the electrocardiographic characteristics of ventricular arrhythmias (VAs) originating near the His bundle (HB) and use the R/S ratio in lead III (RIII/SIII ratio) to predict successful ablation of para-Hisian VAs. Catheter ablation for idiopathic VAs near the HB is often challenging, and data are limited. The present study included 134 consecutive patients undergoing catheter ablation of para-Hisian VAs. The electrocardiographic characteristics in these patients were retrospectively evaluated with successful ablation and failed ablation. Successful ablation was achieved in 115 (85.8%) of the 134 patients. There was no significant difference in QRS duration between the successful and the failed ablation groups. The ablation success rate was significantly lower for para-Hisian VAs with a predominantly positive R wave in lead III than those with a predominantly negative S wave in lead III. The significant factor associated with successful ablation was the RIII/SIII ratio. The RIII/SIII ratio≤1.1 predicted the successful ablation of para-Hisian VAs with high sensitivity (80.9%) and specificity (94.7%). The RIII/SIII ratio of >1.2 had high sensitivity (100.0%) and specificity (82.8%) to predict the distance<5mm from the site of origin of para-Hisian VAs to the site recording the largest HB potential. The RIII/SIII ratio was a helpful predictor of the successful ablation of VAs originating in the vicinity of the HB. This may be useful for planning ablation of para-Hisian VAs and minimizing the risk of inadvertent atrioventricular block.

Not the pacing site but the underlying structural heart disease is a reason for wider QRS duration during right ventricular pacing

Abstract Background Right ventricular (RV) pacing causes changes of the electrical and mechanical activation pattern of the heart. QRS duration is reported to be a useful surrogate marker of electrical dyssynchrony, and wider QRS duration during RV pacing indicates poor prognosis. However, the mechanism of widening QRS duration during RV pacing remains to be elucidated. Methods A total of 211 patients who underwent catheter ablation for supraventricular tachyarrhythmias and have no bundle-branch-block on ECG were enrolled. During electrophysiological study, 3-dimensional mapping for QRS duration during RV pacing from RV outflow to RV apex was created, and the difference of QRS duration between RV outflow and RV apex was calculated. The relationship between QRS duration during RV pacing and patients' baseline characteristics including echocardiography data was analyzed. Results QRS duration at baseline, during RV pacing from RV outflow, and RV apex were 85.0±7.5msec, 156.2±16.1msec, and 163.7±17.1msec, respectively. The difference of QRS duration between RV outflow and RV apex among patients was only 12.5±10.4msec. The logistic multivariable regression analysis showed baseline QRS duration (odds ratio (OR) 1.24, 95% CI 1.15 to 1.34, p&amp;lt;0.01), interventricular septum thickness (OR 1.35, 95% CI 1.05 to 1.73, p=0.018), and E/e' (OR 1.23, 95% CI 1.12 to 1.36, p&amp;lt;0.01) were significant predictors for QRS duration over 160msec during RV apical pacing. Conclusions QRS duration during RV pacing depends largely not on the pacing site, but on the underlying structural heart disease. QRS duration mapping during RV pacing Funding Acknowledgement Type of funding source: None

His bundle pacing to avoid electrical dyssynchrony with traditional right ventricular pacing: Importance of heart size

BackgroundHis Bundle Pacing (HBP) is attracting interest as an alternative to traditional right ventricular pacing (RVP) because it avoids electrical dyssynchrony induced by RVP. This study aims to evaluate the effect of heart size on benefit from HBP compared to RVP in terms of achieving electrical synchrony. MethodsFifty-nine patients with HBP and a RVP back-up lead underwent pre-implantation echocardiography to measure left ventricular end-diastolic volume (LVEDV). Electrical benefit from HBP was calculated as the difference in QRS duration (QRSd) between RVP and HPB. ResultsLVEDV was significantly correlated with RVP QRSd (R = 0.53; p < 0.001). In contrast, LVEDV was unrelated to HBP QRSd (R = 0.16; p = 0.24). Electrical benefit of HBP over RVP was directly related with LVEDV (R = 0.43; p = 0.001). In addition, electrical benefit of HBP was larger for patients with LVEDV above median (99 mL) than below (49 ± 27 ms vs. 34 ± 19 ms, p = 0.014). ConclusionsThis study is the first to demonstrate that patients with larger LV size may benefit most from HBP as a replacement of traditional RVP to avoid electrical dyssynchrony. Our results indicate that LV size impacts QRSd during RVP with slow cell-to-cell conduction, whereas it does not affect electrical synchrony during HBP with fast His-Purkinje conduction.

Natural History and Clinical Significance of Isolated Complete Left Bundle Brunch Block without Associated Structural Heart Disease

Left bundle branch block (LBBB), which is associated with underlying cardiac disease, is believed to play a role in the pathogenesis of cardiomyopathy through delays in interventricular conduction, leading to dyssynchrony. However, this has not been established in previous studies. It is unclear whether LBBB indicates clinically advanced cardiac disease or is an independent factor responsible for increased mortality and the development of heart failure. We investigated the natural history of isolated LBBB without any associated structural heart disease in order to determine its clinical significance.We performed a retrospective chart review on consecutive patients who fulfilled the 12-lead electrocardiographic (ECG) criteria for complete LBBB and had a normal echocardiogram with no evidence of structural heart disease and left or right ventricular systolic dysfunction within three months of the initial ECG between January 1, 2000 and December 31, 2009. We excluded patients with documented coronary artery disease (CAD) at any time, any structural heart disease, or cardiac devices. We evaluated the primary endpoints of mortality and incidence of cardiomyopathy, as well as any heart failure hospitalizations over a 1- and 10-year period.We identified 2522 eligible patients. The mean follow-up duration was 8.4±3.2 years. The one-year mortality rate was 7.8%, with a 10-year mortality rate of 22.0%. The incidence of cardiomyopathy over one year was 3.2% and over 10 years was 9.1%. There was no significant difference in QRS duration between patients who were alive and those that were deceased at 10 years (141+/-18 vs. 141+/-17 ms; p=0.951) and patients with and without cardiomyopathy at 10 years (142±17 vs. 141±17 ms; p=0.532).Isolated LBBB occurring without structural heart disease, ventricular dysfunction, or CAD is associated with a low mortality rate and incidence of cardiomyopathy.

P6552Is it possible to recognize free-wall implantation of leadless pacemakers from an ECG?

Abstract Background Leadless pacemaker (Micra, Medtronic, US) is a effective treatment for bradycardia and eliminates any malfunctions related to intravenous leads. However, some cases exhibit pericardial effusion, presumably associated to device implantation to right ventricular free-wall. Objectives The present study was carried out to find ECG features during ventricular pacing by Micra, which enabled to distinguish free-wall implantation from septal implantation without imaging modalities. Methods Consecutive 21 patients who received implantation of Micra in our facility were enrolled. Location of device in the right ventricle was evaluated using echocardiography or computed tomography in order to determine whether the device was implanted on the septum or the freewall. The difference of 12-lead ECG during ventricular pacing from Micra were analyzed between the septum group and the free wall group. Results According to the imaging investigation, body of Micra was clearly identifiable in 17 patients. The locations of device were classified into septum in 11 patients, free-wall in 4 patients, and indeterminate but apex in 2 patients. Further analysis regarding ECG was performed exclusively between the septum group and the free-wall group. In lead V1, peak deflection index (PDI) was significantly larger in free-wall group than septum group (0.64±0.06 vs. 0.45±0.10, P=0.005), whereas there was no difference of QRS duration, transitional zone and QRS pattern. PDI of V1 and Location of LPM Conclusion PDI of V1 could be useful to predict implantation of Micra to free-wall and may potentially stratify the risk of postprocedural pericardial effusion.

P597Clinical and prognostic correlates of volume/time curve at cardiac magnetic resonance in patients with non-ischemic heart failure and left bundle branch block

Abstract Background In patients with non-ischaemic systolic heart failure (HF) and left bundle branch block (LBBB), the systolic phase of the left ventricular (LV) volume/time (V/t) curve at cardiac magnetic resonance (CMR) can display a wide or a narrow pattern (WP/NP). The clinical and prognostic significance of these patterns are currently unknown. Methods Consecutive patients with systolic non-ischaemic HF (LV ejection fraction &lt;50%) and LBBB were enrolled. They underwent a baseline evaluation including CMR, and were periodically re-evaluated during follow-up. The endpoint was a composite of cardiovascular death, heart failure (HF)-related event, and ventricular arrhythmias requiring defibrillator shock. Results Out of 101 patients (mean age 64±11 years, males 50%), NP was found in 29 and WP in 72, with no difference in QRS duration. Patients with WP had worse clinical presentation and greater LV volumes, but similar LGE prevalence, extent or distribution. The WP subgroup displayed a greater maximal dyssynchrony time, expressed both as absolute duration (192±80 vs. 143±65 ms, P&lt;0.001), and as percentage of the RR interval (25±11% vs. 8±4%, p&lt;0.001). Even the systolic dyssynchrony index was higher in patients with WP (13±4 vs. 7±3%, p&lt;0.001). The contractility index was lower in patients with the WP (2.6±1.2 vs 3.2±1.7, p&lt;0.05). Over a median follow-up duration of 44 months (interquartile interval 23–59), only WP (p=0.029) and NT-proBNP (p=0.004) demonstrated an independent prognostic value for cardiac events. Conclusions In patients with non-ischaemic systolic HF and LBBB, the WP of V/t curves identifies a subgroup of patients with greater LV dyssynchrony, worse clinical conditions and prognosis.