The association between paced left ventricular activation time and cardiac reverse remodeling in heart failure patients with left bundle branch block.

INTRODUCTION: The association between paced LVAT and cardiac structure and function at baseline, as well as whether longer LVAT is associated with worse cardiac reverse remodeling in patients with heart failure (HF) and left bundle branch block (LBBB) has not been well investigated. The purpose of this study is to investigate the association between paced LVAT and baseline echocardiographic parameters and cardiac reverse remodeling at follow-up. METHODS: Patients with HF and LBBB receiving successful left bundle branch pacing (LBBP) from June 2018 to April 2023 were enrolled and grouped based on paced LVAT. NT-proBNP and echocardiographic parameters were recorded during routine follow-up. The relationships between paced LVAT and echocardiographic parameters at baseline and follow-up were analyzed. RESULTS: Eighty-three patients were enrolled (48 males, aged 65 ± 9.8, mean LVEF 32.1 ± 7.5%, mean LVEDD 63.0 ± 8.5 mm, median NT-proBNP 1057[513-3158] pg/mL). The paced QRSd was significantly decreased (177 ± 17.9 vs. 134 ± 18.5, p < .001) and median paced LVAT was 80[72-88] ms. After a median follow-up of 12[9-29] months, LVEF increased to 52.1 ± 11.2%, LVEDD decreased to 52.6 ± 8.8 mm, and NT-proBNP decreased to 215[73-532]pg/mL. Patients were grouped based on paced LVAT: LVAT < 80 ms (n = 39); 80 ≤ LVAT < 90 ms (n = 24); LVAT ≥ 90 ms (n = 20). Patients with longer LVAT had larger LVEDD and lower LVEF (LVEDDbaseline: p < .001; LVEFbaseline: p = .001). The difference in LVEF6M was statistically significant among groups (p < .001) and patients with longer LVAT had lower LVEF6M, while the difference in LVEF1Y was not seen (p = .090). There was no significant correlation between ΔLVEF6M-baseline, ΔLVEF1Y-6M and LVAT respectively (ΔLVEF6M-baseline: p = .261, r = -.126; ΔLVEF1Y-6M: p = .085, r = .218). CONCLUSION: Long paced LVAT was associated with worse echocardiographic parameters at baseline, but did not affect the cardiac reverse remodeling in patients with HF and LBBB. Those with longer LVAT required longer time to recover.

Pilot study to evaluate left-to-right ventricular offset in biventricular pacing-comparison of electrocardiographic imaging and ECG.

INTRODUCTION: Biventricular pacing (BiVp) improves outcomes in systolic heart failure patients with electrical dyssynchrony. BiVp is delivered from epicardial left ventricular (LV) and endocardial right ventricular (RV) electrodes. Acute electrical activation changes with different LV-RV stimulation offsets can help guide individually optimized BiVp programming. We sought to study the BiVp ventricular activation with different LV-RV offsets and compare with 12-lead ECG. METHODS: In five patients with BiVp (63 ± 17-year-old, 80% male, LV ejection fraction 27 ± 6%), we evaluated acute ventricular epicardial activation, varying LV-RV offsets in 20 ms increments from -40 to 80 ms, using electrocardiographic imaging (ECGI) to obtain absolute ventricular electrical uncoupling (VEUabs, absolute difference in average LV and average RV activation time) and total activation time (TAT). For each patient, we calculated the correlation between ECGI and corresponding ECG (3D-QRS-area and QRS duration) with different LV-RV offsets. RESULTS: The LV-RV offset to attain minimum VEUabs in individual patients ranged 20-60 ms. In all patients, a larger LV-RV offset was required to achieve minimum VEUabs (36 ± 17 ms) or 3D-QRS-area (40 ± 14 ms) than that for minimum TAT (-4 ± 9 ms) or QRS duration (-8 ± 11 ms). In individual patients, 3D-QRS-area correlated with VEUabs (r 0.65 ± 0.24) and QRS duration correlated with TAT (r 0.95 ± 0.02). Minimum VEUabs and minimum 3D-QRS-area were obtained by LV-RV offset within 20 ms of each other in all five patients. CONCLUSIONS: LV-RV electrical uncoupling, as assessed by ECGI, can be minimized by optimizing LV-RV stimulation offset. 3D-QRS-area is a surrogate to identify LV-RV offset that minimizes LV-RV uncoupling.

Near-field detection and peak frequency metric for substrate and activation mapping of ventricular tachycardias in two- and three-dimensional circuits.

AIMS: Successful ventricular arrhythmia (VA) ablation requires identification of functionally critical sites during contact mapping. Estimation of the peak frequency (PF) component of the electrogram (EGM) may improve correct near-field (NF) annotation to identify circuit segments on the mapped surface. In turn, assessment of NF and far-field (FF) EGMs may delineate the three-dimensional path of a ventricular tachycardia (VT) circuit. METHODS AND RESULTS: A proprietary NF detection algorithm was applied retrospectively to scar-related re-entry VT maps and compared with manually reviewed maps employing first deflection (FDcorr) for VT activation maps and last deflection (LD) for substrate maps. Ventricular tachycardia isthmus location and characteristics mapped with FDcorr vs. NF were compared. Omnipolar low-voltage areas, late activating areas, and deceleration zones (DZ) in LD vs. NF substrate maps were compared. On substrate maps, PF estimation was compared between isthmus and bystander sites. Activation mapping with entrainment and/or VT termination with radiofrequency (RF) ablation confirmed critical sites. Eighteen patients with high-density VT activation and substrate maps (55.6% ischaemic) were included. Near-field detection correctly located critical parts of the circuit in 77.7% of the cases compared with manually reviewed VT maps as reference. In substrate maps, NF detection identified deceleration zones in 88.8% of cases, which overlapped with FDcorr VT isthmus in 72.2% compared with 83.3% overlap of DZ assessed by LD. Applied to substrate maps, PF as a stand-alone feature did not differentiate VT isthmus sites from low-voltage bystander sites. Omnipolar voltage was significantly higher at isthmus sites with longer EGM durations compared with low-voltage bystander sites. CONCLUSION: The NF algorithm may enable rapid high-density activation mapping of VT circuits in the NF of the mapped surface. Integrated assessment and combined analysis of NF and FF EGM-components could support characterization of three-dimensional VT circuits with intramural segments. For scar-related substrate mapping, PF as a stand-alone EGM feature did not enable the differentiation of functionally critical sites of the dominant VT from low-voltage bystander sites in this cohort.

Excellent coagulation performance of polysilicate aluminum ferric for treating oily wastewater from Daqing gasfield: Responses to polymer properties and coagulation mechanism.

The polysilicate aluminum ferric (PSAF) was synthesized via copolymerization of polysilicic acid (PSi), AlCl3 and FeCl3 for treating oily wastewater from Daqing gas field. This study investigated the effects of key preparation factors such as the degree of PSi's preactivation and the ratio of (Fe + Al)/Si and Al/Fe on both polymerization and coagulation performance exhibited by PSAF. To determine the optimal timing for introducing Al3+ and Fe3+, zeta potential, viscosity and particle size were investigated. Additionally, infrared spectroscopy, X-ray powder diffraction, polarizing microscopy and scanning electron microscope analysis were employed to investigate the structure and morphology of PSAF. The results indicate that under conditions characterized by a SiO2 mass fraction of 2.5% and pH = 4.5, an optimal timing for introducing Al3+ and Fe3+ is at 100 min when PSi exhibits moderate polymerization along with sufficient stability. When considering molar ratios such as (Al + Fe)/Si being 6:4 and Al/Fe being 5:5, respectively, PSAF falls within a "stable zone" enabling storage period up to 32 days. Moreover, Jar test results demonstrate that at a dosage of 200 mg/L PSAF for oily wastewater treatment in gas fields could reach the maximum turbidity removal efficiency up to 99.5% while oil removal efficiency reach 88.6% without pH adjustment. The copolymerization facilitates the formation of larger PSAF aggregates with positive potential, thereby augmenting the coagulants' adsorption bridging and charge neutralization capabilities. As a result, PSAF has great potential as a practical coagulant for treating oil-containing wastewater in industrial settings.

Insight of electrocardiographic and electrophysiological parameters on the left ventricular function in patients with ventricular arrhythmia from left ventricular summit.

INTRODUCTION: Ventricular arrhythmia (VA) commonly originate from the left ventricular summit (LVS) and results in left ventricular (LV) dysfunction in some patients; however, factors related to LV cardiomyopathy have not been well elucidated. Therefore, this study aimed to investigate the risk factors for LV cardiomyopathy and the outcomes of patients with LVS VA. METHODS: Between 2013 and 2018, a total of 139 patients (60.7% men; mean age 53.2 ± 13.9 years old) underwent catheter ablation for LVS VA in two centers. Detailed patient demographics, electrocardiograms, electrophysiological characteristics, and clinical outcomes were analyzed. LV cardiomyopathy was defined as left ventricular ejection fraction (LVEF) <50%. RESULTS: Acute procedural success was achieved in 92.8% of patients. There were 40 patients (28.8%) with LV cardiomyopathy, and the mean LVEF improved from 37.5 ± 9.3% to 48.5 ± 10.2% after ablation (p < .001). After multivariate analysis, the independent factors of LV dysfunction were wider QRS duration (QRSd) of the VA (odds ratio [OR] 1.02; 95% confidence interval [CI]: 1.00-1.04; p = .046) and the absolute earliest activation time discrepancy (AEAD) between epicardium and endocardium (OR 1.05; 95% CI: 1.00-1.09; p = .048). After ablation, the LV function was completely recovered in 20 patients (50%). The factors for LV dysfunction without recovery included wider premature ventricular complex (PVC) QRSd (OR 1.09; 95% CI: 1.02-1.17; p = .012) and poorer LVEF (OR 0.85; 95% CI: 0.74-0.97; p = .020). CONCLUSION: In patients with VA from the LVS, PVC QRSd and AEAD are factors associated with deteriorating LV systolic function. Catheter ablation can reverse LV remodeling. Narrower QRSd and better LVEF are associated with better recovery of LV function after ablation.

Electromechanical factors associated with favourable outcome in cardiac resynchronization therapy.

AIMS: Electromechanical coupling in patients receiving cardiac resynchronization therapy (CRT) is not fully understood. Our aim was to determine the best combination of electrical and mechanical substrates associated with effective CRT. METHODS AND RESULTS: Sixty-two patients were prospectively enrolled from two centres. Patients underwent 12-lead electrocardiogram (ECG), cardiovascular magnetic resonance (CMR), echocardiography, and anatomo-electromechanical mapping (AEMM). Remodelling was measured as the end-systolic volume (ΔESV) decrease at 6 months. CRT was defined effective with ΔESV ≤ -15%. QRS duration (QRSd) was measured from ECG. Area strain was obtained from AEMM and used to derive systolic stretch index (SSI) and total left-ventricular mechanical time. Total left-ventricular activation time (TLVAT) and transeptal time (TST) were derived from AEMM and ECG. Scar was measured from CMR. Significant correlations were observed between ΔESV and TST [rho = 0.42; responder: 50 (20-58) vs. non-responder: 33 (8-44) ms], TLVAT [-0.68; 81 (73-97) vs. 112 (96-127) ms], scar [-0.27; 0.0 (0.0-1.2) vs. 8.7 (0.0-19.1)%], and SSI [0.41; 10.7 (7.1-16.8) vs. 4.2 (2.9-5.5)], but not QRSd [-0.13; 155 (140-176) vs. 167 (155-177) ms]. TLVAT and SSI were highly accurate in identifying CRT response [area under the curve (AUC) > 0.80], followed by scar (AUC > 0.70). Total left-ventricular activation time (odds ratio = 0.91), scar (0.94), and SSI (1.29) were independent factors associated with effective CRT. Subjects with SSI >7.9% and TLVAT <91 ms all responded to CRT with a median ΔESV ≈ -50%, while low SSI and prolonged TLVAT were more common in non-responders (ΔESV ≈ -5%). CONCLUSION: Electromechanical measurements are better associated with CRT response than conventional ECG variables. The absence of scar combined with high SSI and low TLVAT ensures effectiveness of CRT.

Comparisons of electrophysiological characteristics, pacing parameters and mid- to long-term effects in right ventricular septal pacing, right ventricular apical pacing and left bundle branch area pacing.

BACKGROUND: As a near-physiological pacing innovation, left bundle branch area pacing (LBBAP) has drawn much attention recently. This study was aimed to investigate the electrophysiological characteristics, unipolar/bipolar pacing parameters and mid- to long-term effects and safety of three different pacing methods and identify possible predictors of adverse left ventricular remodeling. METHODS: Ninety-two patients were divided into the LBBAP group, right ventricular septal pacing (RVSP) group and right ventricular apical pacing (RVAP) group. Baseline information, electrophysiological, pacing and echocardiographic parameters were collected. RESULTS: The three pacing methods were performed with a similar high success rate. The paced QRSd was significantly different among the LBBAP, RVSP and RVAP groups (105.93 ± 15.85 ms vs. 143.63 ± 14.71 ms vs. 155.39 ± 14.17 ms, p < 0.01). The stimulus to left ventricular activation time (Sti-LVAT) was the shortest in the LBBAP group, followed by the RVSP and RVAP groups (72.80 ± 12.07 ms vs. 86.29 ± 8.71 ms vs. 94.14 ± 10.14 ms, p < 0.001). LBBAP had a significantly lower tip impedance during the procedure and 3-month follow up as compared to RVSP and RVAP (p < 0.001). Higher bipolar captured thresholds were observed in LBBAP during the procedure (p < 0.001). Compared to the baseline values, there was a greater reduction in left ventricular end-diastolic dimension (LVEDD) in the LBBAP group (p = 0.046) and a significant enlargement in LVEDD in the RVAP group (p = 0.008). Multiple regression analysis revealed that the Sti-LVAT was a significant predictor of LVEDD at 12 months post-procedure. At the 24-h post-procedure, significant elevations were observed in the cTnI levels in LBBAP (p < 0.001) and RVSP (p < 0.05). More transient RBB injury was observed in LBBAP. But no significant difference was found in cardiac composite endpoints among three groups (p > 0.05). CONCLUSIONS: LBBAP demonstrated a stable captured threshold, a low tip impedance and a high R-wave amplitude during the 12-month follow-up. Left ventricular remodeling was improved at 12 months post-procedure through LBBAP. The Sti-LVAT was a significant predictor of left ventricular remodeling. LBBAP demonstrated its feasibility, effectiveness, safety and some beneficial electrophysiological characteristics during this mid- to long-term follow-up, which should be confirmed by further studies.

Spatiotemporal approximation of cardiac activation and recovery isochrones.

BACKGROUND: The sequence of myocardial activation and recovery can be studied in detail by invasive catheter recordings of cardiac electrograms (EGMs), or noninvasive inverse reconstructions thereof with electrocardiographic imaging (ECGI). Local activation and recovery times are obtained from a unipolar EGM by the moment of maximum downslope of the QRS complex or maximum upslope of the T wave, respectively. However, both invasive and noninvasive recordings of intracardiac EGMs may suffer from noise and fractionation, making reliable detection of these deflections nontrivial. METHODS: Here, we introduce a novel method that benefits from the spatial coupling of these processes, and incorporate not only the temporal EGM deflection, but also the spatial gradients. We validated this approach in computer simulations, in animal data with ECGI and invasive electrode recordings, and illustrated its use in a clinical case. RESULTS: In the simulated data, the spatiotemporal approach was able to incorporate spatial information to better select the correct deflection in artificially fractionated EGMs and outperformed the traditional temporal-only method. In experimental data, the accuracy of time estimation from ECGI compared to invasive recordings significantly increased from R = 0.73 (activation) and R = 0.58 (recovery) with the temporal-only method to R = 0.79 (activation) and R = 0.72 (recovery) with the novel approach. Localization of the pacing origin of paced beats improved significantly from 36 mm mean error with the temporal-only approach to 23 mm with the spatiotemporal approach. CONCLUSION: The spatiotemporal method to compute activation and recovery times from EGMs outperformed the traditional temporal-only approach in which spatial information was not taken into account.

Successful Ablation of a Biatrial Tachycardia from the Superior Vena Cava after a Senning Operation for Complete Transposition of the Great Arteries.

The Senning operation used to be widely performed for an intracardiac repair in a complete transposition of the great arteries. During the long-term follow-up, supraventricular tachycardia (SVT) is often observed because of the complex suture lines. The typical mechanism of a Senning-related SVT is cavo-tricuspid isthmus-dependent atrial flutter. On rare occasions, complex SVTs (e.g., biatrial tachycardia (BiAT)) whose diagnosis and treatment are challenging, may occur. We report a rare case of a BiAT following a Senning operation that was successfully ablated from the superior vena cava, and the local activation time histogram module (CARTO3 V7 module [Biosense Webster, Irvine, CA, USA]) was crucial for analyzing the complex circuit.

Cardiac cycle time-corrected electromechanical activation time greater than 15% is an independent risk factor for major adverse cardiovascular events in chronic heart failure outpatients.

Objectives: This study aimed to investigate the predictive value of cardiac cycle time-corrected electromechanical activation time (EMATc) for major adverse cardiovascular events (MACEs) in outpatients with chronic heart failure (CHF) in comparison with other clinic indexes. Methods: This prospective observational study at Beijing Anzhen Hospital from January 01, 2015 to January 01 2018 enrolled 120 CHF patients who were admitted for acute onset of CHF and followed up after discharge for 616.5 days (range: 202.75-875.25 days). Based on the different endpoints, cardiogenic death, all-cause death, and HF-related readmission, patients were assigned to the following groups: cardiogenic death and non-cardiogenic death groups, all-cause death and survival groups, and HF readmission and non-readmission groups. EMATc and other clinic indexes were measured and compared between these groups. Cox regression analysis was used to identify independent risk factors for MACEs. Results: The hazard ratio for EMATc>15% for cardiogenic death was 3.493 (P=0.046), suggesting that an EMATc>15% was an independent risk factor for cardiogenic death in CHF patients. The hazard ratios for B-type natriuretic peptide (BNP) >400 ng/L for all-cause death and CHF readmission were 3.810 (P=0.008) and 2.764 (P=0.031), respectively. Thus, BNP >400 ng/L was an independent risk factor for all-cause death and readmission for CHF. EF<40% was not found to be a significant risk factor for MACEs. Conclusions: BNP level can predict the risk for poor prognosis in CHF patients. EMATc>15% is an independent risk factor for cardiogenic death and should be considered as a supplement to serum BNP level and other clinical indexes for predicting cardiogenic death in CHF outpatients.

The P wave dispersion-one pixel, one millisecond.

The electrophysiological activity of the heart is recorded and presented in form of electrocardiogram (ECG). In 1998 the concept of P wave dispersion as the risk factor for atrial fibrillation (AF) recurrence was introduced. It was calculated as the difference between the longest and the shortest P wave. The aim of our study is to prove that the P wave dispersion is an artifact of low accuracy in P wave measurement. The study included 186 patients (78M 108F) aged 59.7 ± 12.9 years, undergoing various electrophysiological procedures. The P wave was measured twice: first, at the paper speed of 50 mm/s, enhancement 8× (standard - imprecise) and the second time at 200 mm/s, 64-256× (precise). The imprecise measurement method resulted in different duration of all P wave parameters in comparison with precise measurement. The difference between Δ P max and Δ P min indicated a higher value for the latter parameter. It was indicated that the imprecise P wave dispersion value correlated most significantly with the maximal P wave duration, which was measured in a similar way. In contrast with the imprecise measurement method, the minimal and maximal durations of the P waves, being measured accurately, were almost identical. Using precise methodology, the P wave dispersion reaches negligible values and tends to zero. The measurements of the P wave have to be precise to assure the highest scientific and medical sincerity. The highest clinical value is related to the P wave duration.

A pilot study to determine if left ventricular activation time is a useful parameter for left bundle branch capture: Validated by ventricular mechanical synchrony with SPECT imaging.

BACKGROUND: Left bundle branch (LBB) pacing has emerged as a novel pacing modality. Left ventricular activation time (LVAT) was reported to be associated with the activation via LBB, but the value of LVAT for determining LBB pacing was unknown. We conducted a pilot study to determine if LVAT could define LBB capture by validating left ventricular (LV) mechanical synchrony. METHODS: We analyzed LVAT in 68 bradycardia-indicated patients who received LBB pacing. LVAT was measured from the stimulus to R-wave peak in lead V5 and V6. LV mechanical synchrony assessed by SPECT MPI was compared according to the value of LVAT and the presence of LBB potential. RESULTS: The mean LVAT was 75.4 ± 12.7 ms. LBB potential was recorded in 47 patients (69.1%). Patients with LVAT < 76 ms had better LV mechanical synchrony than those with LVAT ≥ 76 ms. Patients with LVAT < 76 ms or LBB potential had better mechanical synchrony than those with LVAT ≥ 76 ms and no potential. LVAT < 76 ms could predict the normal synchrony with a sensitivity of 88.9% and a specificity of 87.5%. CONCLUSION: A short LVAT indicated favorable mechanical synchrony in SPECT imaging. LVAT < 76 ms might be a practical parameter for defining LBB capture.

Effects of genetic background, sex, and age on murine atrial electrophysiology.

AIMS: Genetically altered mice are powerful models to investigate mechanisms of atrial arrhythmias, but normal ranges for murine atrial electrophysiology have not been robustly characterized. METHODS AND RESULTS: We analyzed results from 221 electrophysiological (EP) studies in isolated, Langendorff-perfused hearts of wildtype mice (114 female, 107 male) from 2.5 to 17.7 months (mean 7 months) with different genetic backgrounds (C57BL/6, FVB/N, MF1, 129/Sv, Swiss agouti). Left atrial monophasic action potential duration (LA-APD), interatrial activation time (IA-AT), and atrial effective refractory period (ERP) were summarized at different pacing cycle lengths (PCLs). Factors influencing atrial electrophysiology including genetic background, sex, and age were determined. LA-APD70 was 18 ± 0.5 ms, atrial ERP was 27 ± 0.8 ms, and IA-AT was 17 ± 0.5 ms at 100 ms PCL. LA-APD was longer with longer PCL (+17% from 80 to 120 ms PCL for APD70), while IA-AT decreased (-7% from 80 to 120 ms PCL). Female sex was associated with longer ERP (+14% vs. males). Genetic background influenced atrial electrophysiology: LA-APD70 (-20% vs. average) and atrial ERP (-25% vs. average) were shorter in Swiss agouti background compared to others. LA-APD70 (+25% vs. average) and IA-AT (+44% vs. average) were longer in 129/Sv mice. Atrial ERP was longer in FVB/N (+34% vs. average) and in younger experimental groups below 6 months of age. CONCLUSION: This work defines normal ranges for murine atrial EP parameters. Genetic background has a profound effect on these parameters, at least of the magnitude as those of sex and age. These results can inform the experimental design and interpretation of murine atrial electrophysiology.

MANual vs. automatIC local activation time annotation for guiding Premature Ventricular Complex ablation procedures (MANIaC-PVC study).

AIMS: To assess potential benefits of a local activation time (LAT) automatic acquisition protocol using wavefront annotation plus an ECG pattern matching algorithm [automatic (AUT)-arm] during premature ventricular complex (PVC) ablation procedures. METHODS AND RESULTS: Prospective, randomized, controlled, and international multicentre study (NCT03340922). One hundred consecutive patients with indication for PVC ablation were enrolled and randomized to AUT (n = 50) or manual (MAN, n = 50) annotation protocols using the CARTO3 navigation system. The primary endpoint was mapping success. Clinical success was defined as a PVC-burden reduction of ≥80% in the 24-h Holter within 6 months after the procedure. Mean age was 56 ± 14 years, 54% men. The mean baseline PVC burden was 25 ± 13%, and mean left ventricular ejection fraction (LVEF) 55 ± 11%. Baseline characteristics were similar between the groups. The most frequent PVC-site of origin were right ventricular outflow tract (41%), LV (25%), and left ventricular outflow tract (17%), without differences between groups. Radiofrequency (RF) time and number of RF applications were similar for both groups. Mapping and procedure times were significantly shorter in the AUT-arm (25.5 ± 14.3 vs. 32.8 ± 12.6 min, P = 0.009; and 54.8 ± 24.8 vs. 67.4 ± 25.2, P = 0.014, respectively), while more mapping points were acquired [136 (94-222) AUT vs. 79 (52-111) MAN; P < 0.001]. Mapping and clinical success were similar in both groups. There were no procedure-related complications. CONCLUSION: The use of a complete automatic protocol for LAT annotation during PVC ablation procedures allows to achieve similar clinical endpoints with higher procedural efficiency when compared with conventional, manual annotation carried out by expert operators.

Electrophysiological Insights into Three Modalities of Left Bundle Branch Area Pacing in Patients Indicated for Pacing Therapy.

Left bundle branch pacing (LBBP) has been adopted as a new pacing therapy whether in routine pacing or patients with heart failure, but the criteria for a completely captured LBBP are too complicated and have a low success rate in routine clinical practice.Consecutive patients with pacing therapy indications were enrolled. Left bundle branch area pacing (LBBAP) was conducted, and the presence of LBB potential, paced QRS duration, stimulus to left ventricular activation time (Stim-LVAT), and LBB potential to left ventricular activation time (LBB po-LVAT) were determined and utilized to characterize LBBAP modalities. Pacing parameters and safety were assessed at 6-month follow-up. LBBAP succeeded in 95.6% of patients (103/106) who completed the 6-month follow-up. Complete LBBP was achieved in 21 (20%) patients, characterized with a short Stim-LVAT equal to LBB po-LVAT. Incomplete LBBP was achieved in 58 (56%) patients with a short Stim-LVAT equal to LBB po-LVAT at a high pacing output and a relatively longer Stim-LVAT at a low pacing output. Deep septal pacing (DSP) characterized with no LBB potential and a longer Stim-LVAT (83.3 ± 7.7 ms) than that in LBBP (71.37 ± 7.1 ms, P < 0.01 versus DSP) was observed in 24 (23%) patients. Complete LBBP had a longer total procedure time and longer fluoroscopic time than the other two groups.This study describes the similarities and differences in electrophysiological characteristics and the possible mechanisms of the different types of LBBAP, classified into 3 modalities in routine clinical practice, each with narrow paced QRS duration and stable parameters, indicating LBBAP can be a near-physiological pacing modality.

Potential Linkage between High Normalized Electromechanical Activation Time (EMAT), an Early Systolic Time Interval Abnormality with Metabolic Syndrome.

BACKGROUND: High electromechanical activation time (EMAT) is associated with paroxysmal atrial fibrillation and heart failure. Little is known about the association between EMAT and metabolic syndrome (MetS), a precursor of cardiovascular disease. OBJECTIVES: To explore the association between EMAT and MetS. METHODS: A total of 429 male volunteers were divided into MetS (n = 135, age 60.3 ± 3.7 years) and non-MetS (n = 294, age 58.1 ± 26.6 years) groups in this cross-sectional study. A complete medical history, fasting blood analysis and phonoelectrocardiographic parameters were recorded. EMAT was defined as the time from the onset of Q- wave to the peak first heart sound (Q-S1 interval), and this interval divided by the R-R interval for heart rate correction was calculated as normalized EMAT (nEMAT). RESULTS: The subjects with MetS had a significantly higher rate of positive nEMAT (nEMAT ≥ 15%: 6.7% vs. 2%, p = 0.015), higher heart rate (HR, 71.9 ± 12.0 vs. 69.2 ± 11.1 bpm, p = 0.022) but shorter left ventricular ejection time (LVST = 312.4 ± 33.5 vs. 319.8 ± 31.8 msec, p = 0.029). However, the normalized LVST (nLVST) was not significantly different after adjusting for HR. In multivariate analysis, nEMAT was significantly associated with MetS (odds ratio = 3.43, 95% confidence interval = 1.195-9.837, p = 0.022). CONCLUSIONS: Positive nEMAT, a prolonged early phase of contraction, was significantly associated with MetS in males. High nEMAT may be an earlier sign of cardiac function abnormality in MetS.

Gaussian process manifold interpolation for probabilistic atrial activation maps and uncertain conduction velocity.

In patients with atrial fibrillation, local activation time (LAT) maps are routinely used for characterizing patient pathophysiology. The gradient of LAT maps can be used to calculate conduction velocity (CV), which directly relates to material conductivity and may provide an important measure of atrial substrate properties. Including uncertainty in CV calculations would help with interpreting the reliability of these measurements. Here, we build upon a recent insight into reduced-rank Gaussian processes (GPs) to perform probabilistic interpolation of uncertain LAT directly on human atrial manifolds. Our Gaussian process manifold interpolation (GPMI) method accounts for the topology of the atrium, and allows for calculation of statistics for predicted CV. We demonstrate our method on two clinical cases, and perform validation against a simulated ground truth. CV uncertainty depends on data density, wave propagation direction and CV magnitude. GPMI is suitable for probabilistic interpolation of other uncertain quantities on non-Euclidean manifolds. This article is part of the theme issue 'Uncertainty quantification in cardiac and cardiovascular modelling and simulation'.

Evidence of reverse electrical remodelling by non-invasive electrocardiographic imaging to assess acute and chronic changes in bulk ventricular activation following cardiac resynchronisation therapy.

INTRODUCTION: Cardiac resynchronisation therapy (CRT) corrects electrical dyssynchrony. However, the temporal changes in the electrical timing according to substrate are unclear. We used electrocardiographic imaging (ECGi) for serial non-invasive assessment of the underlying electrical substrate and its response to resynchronisation. MATERIAL AND METHODS: ECGi activation maps were constructed 1 day and 6 months post CRT implant. ECGi maps were analysed offline to determine the total ventricular activation time (TVaT) and the time for the bulk of ventricular activation (10th to 90th percentile activation; VaT10-90 Index). Statistical analysis was performed using repeated measures ANOVA with post-hoc pairwise comparisons using paired t-tests. The % relative change within each time point was also calculated and compared between the two time points. RESULTS: Eleven CRT patients were studied. Both total and bulk ventricular activation significantly decreased with CRT turned ON at day 1. Intrinsic (CRT OFF) TVaT and VaT10-90 Index at day 1 were 143 ± 23 and 84 ± 20 ms, respectively, and they significantly decreased post CRT to 115 ± 26 ms (P < 0.001) and 49 ± 17 ms (P < 0.05), respectively. The relative change at day 1 was also statistically significant for TVaT (19 ± 12%, P < 0.001) and VaT10-90 Index (39 ± 25%, P < 0.001). After 6 months, the relative decrease in TVaT with CRT ON remained stable (19% vs. 18% at day 1 and 6 months, respectively) whereas reduction the in VaT10-90 Index was decreased 39% vs. 26% at day 1 and 6 months, respectively. In non-ischaemic patients both total and bulk activation times reduced following CRT. Volumetric responders exhibited an electrical remodelling for bulk activation not apparent in Non-responders, after 6 months of CRT ON. CONCLUSIONS: Intrinsic bulk myocardium activation becomes more rapid and synchronous with CRT. The bulk activation time is more susceptible to improvement by CRT in ischaemic patients and volumetric responders. These observations are consistent with CRT causing reverse electrophysiological remodelling in the bulk myocardium, but not in late-activating ischaemic or fibrotic regions.

Identifying the most important ECG predictors of reduced ejection fraction in patients with suspected acute coronary syndrome.

BACKGROUND: Non-invasive screening tools of cardiac function can play a significant role in the initial triage of patients with suspected acute coronary syndrome. Numerous ECG features have been previously linked with cardiac contractility in the general population. We sought to identify ECG features that are most predictive for real-time screening of reduced left ventricular ejection fraction (LVEF) in the acute care setting. METHODS: We performed a secondary analysis of a prospective, observational cohort study of patients evaluated for suspected acute coronary syndrome. We included consecutive patients in whom an echocardiogram was performed during indexed encounter. We evaluated 554 automated 12-lead ECG features in multivariate linear regression for predicting LVEF. We then used regression trees to identify the most important predictive ECG features. RESULTS: Our final sample included 297 patients (aged 63 ± 15, 45% females). The mean LVEF was 57% ± 13 (IQR 50%-65%). In multivariate analysis, depolarization dispersion in the horizontal plane; global repolarization dispersion; and abnormal temporal indices in inferolateral leads were all independent predictors of LVEF (R2 = 0.452, F = 6.679, p < 0.001). Horizontal QRS axis deviation and prolonged ventricular activation time in left ventricular apex were the most important determinants of reduced LVEF, while global QRS duration was of less importance. CONCLUSIONS: Poor R wave progression in precordial leads with dominant QS pattern in V3 is the most predictive feature of reduced LVEF in suspected ACS. This feature constitutes a simple visual marker to aid clinicians in identifying those with impaired cardiac function.

Bayesian accrual modeling and prediction in multicenter clinical trials with varying center activation times.

Investigators who manage multicenter clinical trials need to pay careful attention to patterns of subject accrual, and the prediction of activation time for pending centers is potentially crucial for subject accrual prediction. We propose a Bayesian hierarchical model to predict subject accrual for multicenter clinical trials in which center activation times vary. We define center activation time as the time at which a center can begin enrolling patients in the trial. The difference in activation times between centers is assumed to follow an exponential distribution, and the model of subject accrual integrates prior information for the study with actual enrollment progress. We apply our proposed Bayesian multicenter accrual model to two multicenter clinical studies. The first is the PAIN-CONTRoLS study, a multicenter clinical trial with a goal of activating 40 centers and enrolling 400 patients within 104 weeks. The second is the HOBIT trial, a multicenter clinical trial with a goal of activating 14 centers and enrolling 200 subjects within 36 months. In summary, the Bayesian multicenter accrual model provides a prediction of subject accrual while accounting for both center- and individual patient-level variation.