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.

Pacemaker-Related Factors and Outcomes of Fontan Patients　- Impact of Paced QRS Duration.

BACKGROUND: Permanent pacemaker (PPM) implantation has been identified as a risk factor for morbidity and mortality after Fontan operation. This study investigated the factors associated with outcomes in patients with Fontan physiology who underwent PPM implantation. METHODS AND RESULTS: We retrospectively reviewed 508 patients who underwent Fontan surgery at Asan Medical Center between September 1992 and August 2022. Of these patients, 37 (7.3%) received PPM implantation. Five patients were excluded, leaving 32 patients, of whom 11 were categorized into the poor outcome group. Poor outcomes comprised death, heart transplantation, and "Fontan failure". Clinical, Fontan procedure-related, and PPM-related factors were compared between the poor and good outcome groups. Ventricular morphology, Fontan procedure-associated factors, pacing mode, high ventricular pacing rate, and time from first arrhythmia to PPM implantation did not differ significantly between the 2 groups. However, the poor outcome group exhibited a significantly longer mean paced QRS duration (P=0.044). Receiver operating characteristic curve analysis revealed a paced QRS duration cut-off value of 153 ms with an area under the curve of 0.73 (P=0.035). CONCLUSIONS: A longer paced QRS duration was associated with poor outcomes, indicating its potential to predict adverse outcomes among Fontan patients.

Assessment of QRS duration and presence of fragmented QRS in patients with celiac disease.

Background: Celiac Disease (CD) is characterized by small intestine involvement. However, cardiac manifestations may also be seen in the clinical course. The significance of the QRS prolongation and the presence of QRS fragmentation (fQRS) has been previously studied in many chronic inflammatory disorders as an independent predictor of cardiac manifestations. The study aimed to evaluate the QRS duration and presence of fQRS in patients with CD. Methods: 164 patients with CD and 162 healthy controls were included in the present study. QRS duration and presence of fQRS were calculated from the 12-lead electrocardiogram and compared between groups. The association between these parameters and disease duration was also evaluated. Results: QRS duration was found to be higher in the CD group compared to the control group (83 (76.8-93) vs. 91 (84-94), p<0.001). The presence of fQRS was demonstrated to be higher in the CD group (n=68 (41.5%) vs n=42 (25.9%), p=0.003). Notably, QRS duration was positively correlated with disease duration (Spearman's Rho= 0.47, p<0.001). In addition, disease duration was significantly higher in the fQRS (+) group (60 (23,5-144) vs. 28,5 (15-71,5), p=0.002). Conclusion: This study revealed that QRS prolongation and the presence of fQRS were higher in patients with CD. The presence of these findings may be an indicator of early subclinical cardiac involvement, especially in those with long disease duration. Thus, patients with these ECG findings can be considered for further cardiac evaluation.

Evaluation of QRS duration and presence of fragmented QRS in patients with inflammatory bowel disease.

Background: Inflammatory Bowel Disease (IBD) is mostly characterized by gastrointestinal tract involvement, however can also be accompanied with cardiac manifestations. QRS prolongation and the presence of QRS fragmentation (fQRS) have been previously evaluated in many chronic inflammatory diseases, as an independent predictor of cardiac events. In this study, we aimed to evaluate the QRS duration and fQRS in patients with IBD. Methods: The presented study was designed as a single-center retrospective cohort study. The study population consisted of 217 patients with IBD and 195 healthy controls. QRS duration and presence of fQRS were evaluated using a 12-lead electrocardiogram. These parameters were compared between groups. Results: QRS duration was demonstrated to be higher in the IBD group compared to the control group (92 (86-98) vs. 82 (75-90), p<0.001). The presence of fQRS was significantly higher in the IBD group (n=101 (47%) vs n=59 (30%), p=0.006). In addition, a positive correlation was demonstrated between QRS duration and disease duration (Spearman's Rho= 0.4, p<0.001). Notably, disease and QRS duration were significantly higher in the fQRS (+) group (102 (56.5-154) vs. 55 (24.3-118.3), <0.001; 94 (86-100) vs. 92 (84-96), 0.016; respectively). Conclusion: Our results demonstrated that QRS prolongation and the presence of fQRS (+) were more common in IBD patients, and associated with longer disease duration. These findings may indicate subclinical cardiac involvement in IBD. Therefore, IBD patients, especially those with long-standing disease, should be followed more closely in terms of cardiac manifestations.

Clinical significance of R-wave amplitude in lead V1 and inferobasal myocardial infarction in patients with inferior wall myocardial infarction.

OBJECTIVE: To assess electrocardiogram (ECG) for risk stratification in inferior ST-elevation myocardial infarction (STEMI) patients within 24 h. METHODS: Three hundred thirty-four patients were divided into four ECG-based groups: Group A: R V1 <0.3 mV with ST-segment elevation (ST↑) V7-V9, Group B: R V1 <0.3 mV without ST↑ V7-V9, Group C: R V1 ≥0.3 mV with ST↑ V7-V9, and Group D: R V1 ≥0.3 mV without ST↑ V7-V9. RESULTS: Group A demonstrated the longest QRS duration, followed by Groups B, C, and D. ECG signs for right ventricle (RV) infarction were more common in Groups A and B (p < .01). ST elevation in V6, indicative of left ventricle (LV) lateral injury, was more higher in Group C than in Group A, while the ∑ST↑ V3R + V4R + V5R, representing RV infarction, showed the opposite trend (p < .05). The estimated LV infarct size from ECG was similar between Groups A and C, yet Group A had higher creatine kinase MB isoform (CK-MB; p < .05). Cardiac troponin I (cTNI) was higher in Groups A and C than in B and D (p < .05 and p = .16, respectively). NT-proBNP decreased across groups (p = .20), with the highest left ventricular ejection fraction (LVEF) observed in Group D (p < .05). Group A notably demonstrated more cardiac dysfunction within 4 h post-onset. CONCLUSIONS: For inferior STEMI patients, concurrent R V1 <0.3 mV with ST↑ V7-V9 suggests prolonged ventricular activation and notable myocardial damage. RV infarction's dominance over LV lateral injury might explain these observations.

Can the efficacy of a medical treatment be predicted based on the type of idiopathic premature ventricular contraction?

BACKGROUND: Premature ventricular contractions (PVCs) are common arrhythmias with diverse clinical implications. This retrospective study aimed to evaluate the efficacy of medical treatments using various clinical, imaging, and electrocardiographic parameters in patients with idiopathic PVCs. METHODS: A total of 1051 patients with idiopathic PVCs were retrospectively analyzed. Patients were categorized into three groups based on treatment response: beta-blocker (BB) responders (479 patients), calcium-channel blocker (CCB) responders (335 patients), and class 1c antiarrhythmic (AA) responders (237 patients). Clinical, imaging, and electrocardiographic data were collected and analyzed to assess the factors influencing treatment response. RESULTS: Age, left ventricular ejection fraction (LVEF), PVC QRS duration, CI variability, and multiple PVC morphologies were identified as significant factors affecting treatment response. Older age and lower LVEF were associated with better response to BB treatment, whereas CCB responders showed narrower QRS complexes. BB responders also exhibited higher CI variability, possibly linked to automaticity mechanisms. Moreover, the BB responder group had a higher frequency of multiple PVC morphologies. CONCLUSION: These findings emphasize the importance of tailored treatment approaches based on individual patient characteristics.

Evaluation of electrocardiographic criteria for predicting left ventricular hypertrophy and dilation in presence of left bundle branch block.

BACKGROUND: The utility of standard published electrocardiographic (ECG) criteria for left ventricular hypertrophy (LVH) in patients with left bundle branch block (LBBB) is not established. We have previously shown that in ECGs demonstrating LBBB, QRS duration outperforms vectorcardiographic X, Y, Z lead and root-mean-squared (3D) amplitudes and voltage-time-integrals in diagnosing LVH and dilation. We sought to evaluate diagnostic yields of published LVH criteria versus QRS duration for ECG based diagnosis of LVH and dilation in presence of LBBB. METHODS: We included adult patients with typical LBBB having ECG and transthoracic echocardiogram performed within 3 months of each other in 2010-2020. We obtained area under receiver-operator characteristic curve (AUC) for QRS duration and each of the published ECG LVH criteria to predict increased LV mass indexed (↑LVMi, women >95 g/m2, men >115 g/m2) and LV end diastolic volume indexed (↑LVEDVi, women >61 mL/m2, men >74 mL/m2). RESULTS: Among 413 adults (53 % women, age 73 ± 12 yr) with LBBB, the traditional LVH criteria performed poorly to detect ↑LVMi or ↑LVEDVi. Cornell voltage-duration product had the highest AUCs (↑LVMi 0.634, ↑LVEDVi 0.580). QRS duration had a higher AUC for diagnosing ↑LVMi (women 0.657, men 0.703) and ↑LVEDVi (women 0.668, men 0.699) compared to any other criteria. CONCLUSIONS: In patients with LBBB, prolonged QRS duration (women ≥150 ms, men ≥160 ms) is a superior predictor of LVH and dilation than traditional ECG-based LVH criteria.

Electrocardiographic Z-axis QRS-T voltage-time-integral in patients with typical right bundle branch block - Correlation with echocardiographic right ventricular size and function.

BACKGROUND: Right bundle branch block (RBBB) can be benign or associated with right ventricular (RV) functional and structural abnormalities. Our aim was to evaluate QRS-T voltage-time-integral (VTI) compared to QRS duration and lead V1 R' as markers for RV abnormalities. METHODS: We included adults with an ECG demonstrating RBBB and echocardiogram obtained within 3 months of each other, between 2010 and 2020. VTIQRS and VTIQRST were obtained for 12 standard ECG leads, reconstructed vectorcardiographic X, Y, Z leads and root-mean-squared (3D) ECG. Age, sex and BSA-adjusted linear regressions were used to assess associations of QRS duration, amplitudes, VTIs and lead V1 R' duration/VTI with echocardiographic tricuspid annular plane systolic excursion (TAPSE), RV tissue Doppler imaging S', basal and mid diameter, and systolic pressure (RVSP). RESULTS: Among 782 patients (33% women, age 71 ± 14 years) with RBBB, R' duration in lead V1 was modestly associated with RV S', RV diameters and RVSP (all p ≤ 0.03). QRS duration was more strongly associated with RV diameters (both p < 0.0001). AmplitudeQRS-Z was modestly correlated with all 5 RV echocardiographic variables (all p ≤ 0.02). VTIR'-V1 was more strongly associated with TAPSE, RV S' and RVSP (all p ≤ 0.0003). VTIQRS-Z and VTIQRST-Z were among the strongest correlates of the 5 RV variables (all p < 0.0001). VTIQRST-Z.√BSA cutoff of ≥62 µVsm had sensitivity 62.7% and specificity 65.7% for predicting ≥3 of 5 abnormal RV variables (AUC 0.66; men 0.71, women 0.60). CONCLUSION: In patients with RBBB, VTIQRST-Z is a stronger predictor of RV dysfunction and adverse remodeling than QRS duration and lead V1 R'.

Is left bundle branch pacing (LBBP) associated with better depolarization and repolarization kinetics than right ventricular mid septal pacing (RVSP)? - Comparison of frontal QRS -T angle in patients with LBBP, RVSP and normal ventricular conduction.

AIMS: To assess the frontal QRS- T angle (f QRS- T angle) in patients with left bundle branch pacing (LBBP) as compared to right ventricular mid septal pacing (RVSP) implanted for symptomatic high degree atrioventricular (AV) block and to compare with control subjects with normal ventricular conduction (CSNVC) METHODS: A total of one-fifty subjects were chosen (50 patients with LBBP, 50 patients with RVSP and 50 CSNVC). The indication for pacemaker implantation was symptomatic high degree AV block. Baseline clinical and electrocardiogram (ECG) parameters like QRS duration (QRSD), QRS axis and f QRS-T angle and Ejection Fraction (EF) were assessed. f QRS-T angle was measured as the difference between the computerised mean frontal QRS and T wave axes in the limb leads. If the difference between the QRS axis and T-wave axis exceeds 180°, then the resultant QRS-T angle would be calculated as 360° minus the absolute angle to obtain a value between 0° and 180°. Baseline, immediate post procedural and 6 month follow up (f/u) ECGs and EF were chosen for the analysis. RESULTS: Patients who underwent LBBP had significantly shorter paced QRSD than patients who had undergone RVSP (112 ± 12 ms vs 146 ± 13 ms; 95 % confidence interval (CI): 43, -31; p<0.001). There was no significant difference in the QRSD before and after LBBP. The QRSD before and after pacing in RVSP was 111 ± 27 ms and 146 ± 13 ms; 95 % CI: 43, -28; p < 0.001. The QRSD in control patients with NVC was 82.94 ± 9.59 ms. RVSP was associated with wider f QRS-T angle when compared with LBBP (103 ± 53° vs 82 ± 43°; 95 % CI: 39, -1.0; p = 0.037). The baseline and immediate post procedure f QRS-T angle in LBBP was 70 ± 48° and 82 ± 43°; 95 % CI: 31, 5.3; p = 0.2. At 6 months f/u, the f QRS-T angle was 61 ± 43°; 95 % CI: 8.5, 35; p=0.002. The baseline and immediate post procedure f QRS-T angle in RVSP was 67 ± 51° and 103 ± 53°; 95 % CI: 54, -17; p < 0.001. At 6 months f/u, the f QRS-T angle in RVSP group was 87 ± 58°; 95 % CI: 2.6, 29; p = 0.020. The f QRS T angle in control patients with NVC was 24 ± 16°. When subgroup analysis was done the difference in the f QRS-T angle was significant between RVSP and LBBP groups only in patients who had wide QRS escape. The mean LVEF at 6-month follow-up in LBBP vs RVSP was 61 ± 3.7 % vs 57.1 ± 7.8 %; 95 % CI:1.48, 6.32, p = 0.002. In the RVSP group, three patients developed pacing induced cardiomyopathy (PIC) whereas no patients in the LBBP group developed PIC at 6-month follow-up; p=0.021. One patient with PIC had deterioration of functional status with new onset HF symptoms. The patient symptoms improved with medical therapy and needed no hospitalisation. The patient declined further interventions including upgradation to CRT or LBB pacing. No deaths or ventricular arrhythmias were observed during the study period. CONCLUSION: LBBP is associated with narrower f QRS-T angle as compared to RVSP both at post implant period and at 6 month f/u period. These findings might be due to the more physiological depolarization and repolarization kinetics associated with LBBP. RVSP was associated with 6 % incidence of PIC. Hence wide f QRS-T angle might be a predictor of PIC.

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.

Bilateral septal pacing in combination with coronary venous pacing for cardiac resynchronization therapy.

BACKGROUND: Conventional right ventricular pacing combined with coronary venous pacing (CVP) is a mainstay for cardiac resynchronization therapy (CRT). However, QRS duration of conventional CRT may be frequently more than 130 ms. This study aimed to evaluate the effectiveness of QRS narrowing by bilateral septal pacing (BSP) in combination with CVP for CRT (BSP-CRT). METHODS: Fourteen patients with QRS > 130 ms of conventional CRT after failure of physiological conduction system pacing were enrolled. Electrophysiologic characteristics were compared among different modes of CRT during procedure. BSP which was defined as capture of both sides of interventricular septum manifested as shortened R wave peak time without a right bundle branch block QRS pattern. RESULTS: BSP-CRT were successfully achieved in 85.7% (12/14) patients. QRS duration at baseline was 185 ± 13 ms and significantly narrowed to 156 ± 9 ms during conventional CRT (n = 14, P < .001), to 143 ± 7 ms during left ventricular septal pacing (LVSP) in combination with CVP for CRT (LVSP-CRT) (n = 9, P < .001), and further to 122 ± 10 ms during BSP-CRT (n = 12, P < .001). Notably, among 7 patients in whom both LVSP and BSP were achieved, BSP-CRT outperformed LVSP-CRT at QRS narrowing by 16% (P < .001). At 3-month follow-up, left ventricular ejection fraction improved from 29 ± 6% to 41 ± 8% (P < .001). CONCLUSIONS: BSP-CRT resulted in superior acute electrical synchronization to conventional CRT and might be considered as an alternative to conventional CRT with QRS more than 130 ms.

QRS axis and polarity in the inferior leads during left bundle branch pacing: Novel criteria in the search for better results.

BACKGROUND: Left bundle branch pacing (LBBP) may be achieved in various anatomical sites within the interventricular septum (IVS), thus influencing paced QRS duration (QRSd).The purpose of this study was to determine whether paced QRS axis (QRSâ) and predominant polarity in inferior leads could be associated with a shorter paced QRSd. METHODS: We analyzed paced QRSd, QRSâ, polarity in inferior leads, and IVS thickness in patients referred for LBBP. Three paced morphology patterns in the inferior leads were considered: All positive (P), all negative (N) and intermediate (combination of isoelectric, positive, and negative complexes, (I). Patients were divided into two groups according to a paced QRSd < 120 or ≥ 120 ms. RESULTS: A total of 125 patients were included (age 76 ± 10 years, 46% female). Mean baseline QRSâ was 8 ± 37°. Paced QRSd was significantly shorter as compared to baseline (120 ± 10 vs. 127 ± 33 ms; p = .017) and significantly different according to paced QRS morphology pattern in the inferior leads (P 49%, 119 ± 9; N 30%, 126 ± 12; I 21%; 113 ± 10 ms; p < .001) or paced QRSâ (Normal 59%, 116 ± 1; Right 6%, 129 ± 1; Left 35%, 124 ± 11 ms; p < .001). On multivariate analysis, a QRSâ > -30°(OR 5.79 [2.40-13.93; 95% CI] p = .001), an Intermediate pattern in inferior leads (OR 3.00 [1.67-8.43; 95% CI] p = .037), and an IVS thickness ≤ 10 mm (OR 2.59 [1.10-6.10; 95% CI]; p = .029) were significantly associated with a paced QRSd < 120 ms. CONCLUSIONS: During LBBP, a QRSâ > -30° and intermediate final polarity in inferior leads are associated with a shorter paced QRSd.

Electrocardiographic prediction of left ventricular hypertrophy in women and men with left bundle branch block - Comparison of QRS duration, amplitude and voltage-time-integral.

BACKGROUND: Standard ECG criteria for left ventricular (LV) hypertrophy rely on QRS amplitudes. However, in the setting of left bundle branch block (LBBB), ECG correlates of LV hypertrophy are not well established. We sought to evaluate quantitative ECG predictors of LV hypertrophy in the presence of LBBB. METHODS: We included adult patients with typical LBBB having ECG and transthoracic echocardiogram performed within 3 months of each other in 2010-2020. Orthogonal X, Y, Z leads were reconstructed from digital 12­lead ECGs using Kors's matrix. In addition to QRS duration, we evaluated QRS amplitudes and voltage-time-integrals (VTIs) from all 12 leads, X, Y, Z leads and 3D (root-mean-squared) ECG. We used age, sex and BSA-adjusted linear regressions to predict echocardiographic LV calculations (mass, end-diastolic and end-systolic volumes, ejection fraction) from ECG, and separately generated ROC curves for predicting echocardiographic abnormalities. RESULTS: We included 413 patients (53% women, age 73 ± 12 years). All 4 echocardiographic LV calculations were most strongly correlated with QRS duration (all p < 0.00001). In women, QRS duration ≥ 150 ms had sensitivity/specificity 56.3%/64.4% for increased LV mass and 62.7%/67.8% for increased LV end-diastolic volume. In men, QRS duration ≥ 160 ms had a sensitivity/specificity 63.1%/72.1% for increased LV mass and 58.3%/74.5% for increased LV end-diastolic volume. QRS duration was best able to discriminate eccentric hypertrophy (area under ROC curve 0.701) and increased LV end-diastolic volume (0.681). CONCLUSIONS: In patients with LBBB, QRS duration (≥ 150 in women and ≥ 160 in men) is a superior predictor of LV remodeling esp. eccentric hypertrophy and dilation.

QRS Duration After Pulmonary Valve Replacement in Adults with Repaired Tetralogy of Fallot: Association with Ventricular Arrhythmia and Correlation with Right Ventricular Size.

The aim of this study is to analyze the relationship between QRS duration after pulmonary valve replacement (PVR) and ventricular arrhythmias (VA) in patients with repaired tetralogy of Fallot (ToF). ToF patients may face complications such as heart failure and VA after primary repair, often mitigated by PVR. Prior studies have shown a decrease in QRS duration and right ventricular (RV) size following PVR. It remains unclear whether a lack of QRS duration reduction identifies patients at risk of VA. We retrospectively identified adult patients with repaired ToF who underwent surgical or transcatheter PVR. EKG data (pre-PVR, 30 days to 1-year post-PVR, and closest to CMR) was collected. The primary endpoint was sustained ventricular tachycardia (VT), ICD shock for sustained VT, or inducible VT on EP study. 85 patients were included (median follow-up 3.6 years; median age 34 years; 51% females). The primary outcome was noted in 8 patients. Mean QRS duration decreased by 5 ms following PVR (p = 0.0001). Increased age at PVR, QRS ≥ 180 ms post-PVR, no reduction in QRS after PVR, and a history of VT were associated with higher risk of the primary endpoint. The change in QRS was linearly correlated with the change in RVEDVi (R = 0.66). Adults with repaired ToF experience a reduction in QRS duration post-PVR that correlates with the change of the RV size. Patients with QRS ≥ 180 ms post-PVR, no reduction in QRS, increased age at repair, and a history of VT are at risk for recurrent VT and warrant closer monitoring/ICD consideration.

Association between electrical and mechanical remodeling after cardiac resynchronization therapy: systematic review and meta-analysis of observational studies.

Cardiac resynchronization therapy (CRT) may improve not only impaired left ventricular contractility but can also induce reverse remodeling of native conduction system. Measurement of intrinsic QRS complex width during follow-up is the simplest method to assess reverse electrical remodeling (RER). We aimed to provide a literature review and meta-analysis on incidence and impact of RER and its association with mechanical remodeling. A systematic review and random-effect meta-analysis of studies reporting data on RER was performed. A total of 16 studies were included in this meta-analysis with 930 patients undergoing CRT (mean age 64.0 years, 64.1% males). The weighted mean incidence of RER was 42%. Reverse mechanical remodeling assessed by echocardiography was more frequently observed in patients with RER compared to patients without RER (75.7% vs. 46.6%; odds ratio [OR] 3.7, 95% confidence interval [CI] 2.24-6.09, p < 0.01). Mechanical responders had a mean iQRS shortening of 7.7 ms, while mechanical non-responders experienced a mean widening of iQRS by 5.2 ms (p < 0.01). Clinical improvement was more frequent in patients with RER vs. patients without RER (82.9% vs. 49.0%; OR 5.26; 95% CI 2.92-9.48; p < 0.01). No significant difference in all-cause mortality between patients with and without RER was found. Mean difference between baseline intrinsic QRS and post-implantation paced QRS was significant in patients with later RER (21.2 ms, 95% CI 9.4-32.9, p < 0.01), but not in patients without RER (6.6 ms, 95% CI -2.2-15.4, p = 0.14). Gender, initial left bundle block morphology and heart failure etiology were found not to be predictive for RER. Our meta-analysis demonstrates that shortening of iQRS duration is a common finding during follow-up of patients undergoing CRT and is associated with mechanical reverse remodeling and clinical improvement. Clinical Trial Registration: Prospero Database-CRD42021253336.

Improved risk-stratification in heart failure patients with mid-range to severe abnormalities of QRS duration and systolic function using mechanical dyssynchrony assessed by myocardial perfusion-gated SPECT.

BACKGROUND: The use of left ventricular mechanical dyssynchrony (LVMD), which has been reported to be responsible for unfavorable outcomes, might improve conventional risk-stratification by clinical indices including QRS duration (QRSd) and systolic dysfunction in patients with heart failure (HF). METHODS AND RESULTS: Following measurements of 12-lead QRSd and left ventricular ejection fraction (LVEF), three-dimensional (3-D) LVMD was evaluated as a standard deviation (phase SD) of regional mechanical systolic phase angles by gated myocardial perfusion imaging in 829 HF patients. Patients were followed up for a mean period of 37 months with a primary endpoint of lethal cardiac events (CEs). In an overall multivariate Cox proportional hazards model, phase SDs were identified as significant prognostic determinants independently. The patients were divided into 4 groups by combining with the cut-off values of LVEF (35% and 50%) and QRSd (130 ms and 150 ms). The groups with lower LVEF and prolonged QRSd more frequently had CEs than did the other groups. Patient groups with LVEF < 35% and with 35% ≦ LVEF < 50% were differentiated into low-risk and high-risk categories by using an optimal phase SD cut-off value of both QRSd thresholds. CONCLUSIONS: 3-D LVMD can risk-stratify HF patients with mid-range as well as severe abnormalities of QRSd and systolic dysfunction.

QRS area as a predictor of cardiac resynchronization therapy response: A systematic review and meta-analysis.

BACKGROUND: QRS area, a three-dimensional QRS complex, is a novel vectorcardiography method of measuring the magnitude of electrical forces in the heart. Hypothetically, a greater QRS area denotes higher dyssynchrony and indicates potential benefits from cardiac resynchronization therapy (CRT). Previous studies suggest a positive correlation between QRS area and the degree of response to CRT, but its clinical use remains unclear. We performed a meta-analysis of the relationship between QRS area and survival benefit following CRT. METHODS: We comprehensively searched the MEDLINE, EMBASE, and Cochrane databases from inception to August 2021. We included studies with prospective and retrospective cohort designs that reported QRS area before CRT and total mortality. Data from each study were analyzed using a random-effects model. The results were reported as a hazard ratio (HR) and 95% confidence intervals. RESULTS: Five observational studies including 4931 patients were identified. The cut-off values between large and small QRS areas ranged from 102 to 116 µVs. Our analysis showed a larger QRS area was statistically associated with increased 5-year survival in patients implanted with CRT (HR pooled 0.48, 95% CI 0.46-0.51, I2  = 54%, p < .0001). Greater QRS area reduction (pre- and post-implantation) were associated with a lower total mortality rate (HR pooled 0.45, 95% CI 0.38-0.52, I2  = 0%, p < .0001). CONCLUSION: Larger pre-implantation QRS area was associated with increased survival after CRT. QRS area reduction following CRT implantation was also associated with lower mortality. QRS area may potentially become an additional selection criterion for CRT implantations.

Subtle QRS changes are associated with reduced ejection fraction, diastolic dysfunction, and heart failure development and therapy responsiveness: Applications for artificial intelligence to ECG.

BACKGROUND: Since the last century, the electrocardiogram (ECG) remains the non-invasive test, that is, most easily accessible, feasible, and inexpensive for cardiology assessment. In past years, many novel ECG indexes and patterns have been published that allow for a more advanced evaluation of what is currently being done, especially based on subtle QRS changes and patterns. OBJECTIVE: The objective of the study was to provide an update on the evidence and clinical applications of these ECG subtle QRS changes and patterns associated with heart disease. METHODS: Through the literature review, we will highlight the subtle QRS changes and patterns associated with heart disease, mainly focusing on QRS duration, voltage, morphology, axis, and QT interval. RESULTS: Small increases in QRS duration are associated with a reduction in left ventricular ejection fraction (EF), increased cardiac chamber dimensions, and risk for incident heart failure (HF). Moreover, fragmentation of the QRS complex is associated with myocardial fibrosis and is a substrate for developing arrhythmic events. Besides, low amplitude QRS voltage is associated with congestive HF, and an increase in the voltage of the QRS complexes is associated with the effectiveness of diuresis treatment. Furthermore, small increases in QT interval are associated with diastolic dysfunction due to impaired sarcoplasmic reticulum calcium handling as occurs in myocardial ischemia, hypertension, or diabetes. On the other hand, in patients with left ventricular dysfunction, the QRS area is associated with clinical and echocardiographic response to cardiac resynchronization therapy regardless of the type of bundle branch block. In addition, subtle ECG changes and patterns in the left bundle branch block are associated with concomitant right ventricular dilation, mostly based on the QRS axis and voltage. Notwithstanding, to identify these subtle changes in QRS require exact manual measurements that can take time. In this regard, applying artificial intelligence (AI) to the ECG can make a quicker and more complete assessment, as well as provide a low cost when applied to large populations. CONCLUSION: We provided an update on the evidence and clinical applications of these subtle QRS changes and patterns associated with diastolic dysfunction, reduced EF, and HF development and therapy responsiveness, as well as their applications for AI to ECG.

Periodic breathing in patients with stable obstructive sleep apnea on long-term continuous positive airway pressure treatment: a retrospective study using CPAP remote monitoring data.

PURPOSE: The purpose of this study was to investigate the rate of periodic breathing (PB) and factors associated with the emergence or persistence of PB in patients with obstructive sleep apnea (OSA) by continuous positive airway pressure (CPAP) remote monitoring data. METHODS: This was a retrospective cohort study on 775 patients who had used the same model CPAP machine for at least 1 year as of September 1, 2020. The data were analyzed online using the dedicated analysis system. Using exporter software, average apnea/hypopnea index (AHI), average central apnea index (CAI), and average the rate of PB time (PB%) were cited. RESULTS: Among 618 patients analyzed (age 61.7 ± 12.2 years, male 89%, BMI 27.2 ± 4.9), the average duration of CPAP use was 7.5 ± 4.0 years. The median PB% in stable patients was low at 0.32%, and only 149 patients (24%) had a PB% above 1%. Multiple regression analysis of factors for the development of PB showed that the most important factor was atrial fibrillation (Af) with a coefficient of 0.693 (95% CI; 0.536 to 0.851), followed by QRS duration with a coefficient of 0.445 (95% CI; 0.304 to 0.586), followed by history of heart failure, male sex, comorbid hypertension, obesity, and age. The average PB% for paroxysmal Af was significantly lower than that for persistent and permanent Af. CONCLUSIONS: The median PB% in stable patients on CPAP treatment was low at 0.32%, with only 24% of patients having PB% ≥ 1%. Persistent Af and an increase in QRS duration were found to be important predictors of increased PB%. CLINICAL TRIAL REGISTRATION: UMIN000042555 2021/01/01.

Uneven vectorial projection is the best explanation for QRS dispersion, not the asynchronic ventricular activation.

BACKGROUND: It is believed that QRS dispersion (QRSd) is caused by asynchrony of ventricular activation, but there are no studies that prove it. OBJECTIVES: To determine the mechanism that best explains QRSd in surface electrocardiogram (ECG). METHODS: Cross-sectional study in 95 consecutive patients (median age: 31.0 years [25-52], female sex: 66.3%) with atrioventricular nodal reentrant tachycardia. All 12 ECG leads were recorded at once, simultaneously with the intracardiac recordings. QRSd was quantified as the difference between maximum (QRSmax) and minimum QRS duration (QRSmin). QRS was measured firstly at a calibration of 20 mm/mV and a sweep speed of 50 mm/s, enhancement 10× (basic measurement [BM]), and after at sweep speed of 150 mm/s, enhancement 80 - 160×. The interventricular dyssynchrony (IVD) was also quantified. RESULTS: QRSmax increased from BM (98 ms [91-103]) to 80× (102 ms [99-108]; p = 0.029) and 160× (104 ms [101.5-110]; p = 0.027). QRSmin, almost equaled the duration of QRSmax at 160× (103 ms [100-108]). With BM, QRSd was 26 ms [22-35] and was reduced 26-fold (p < 0.001) by magnifying the QRS at 160× (1 ms [0-3]). IVD was weakly correlated with QRSd (r = 0.234, p = 0.023), but strongly with the total QRS at 160× (r = 0.676, p < 0.001). CONCLUSION: When QRS complex is narrow, the best explanation for the origin of QRSd on the surface ECG is the unequal projection of the ventricular depolarization vector in the different axis of the leads.