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.

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.

Characteristics and proposed mechanisms of QRS morphology observed during the left bundle branch pacing procedure.

BACKGROUND: In performing left bundle branch pacing (LBBP), various QRS morphologies are observed as the lead penetrates the ventricular septum (VS). This study aimed to evaluate these characteristics and infer the mechanism underlying each QRS morphology. METHODS: In 19 patients who met the strict criteria for LBB capture, we classified the QRS morphologies observed during the LBBP procedure into seven patterns, the first five of which were determined by the depth of penetration: right ventricular septal pacing (RVSP), intraventricular septal pacing (IVSP1 and IVSP2), endocardial side of left ventricular septal pacing (LVSeP), nonselective LBBP (NS-LBBP), selective LBBP (S-LBBP), and NS-LBBP with anodal capture. The parameters of the QRS morphologies in these seven patterns were evaluated. RESULTS: Among the first five patterns, stimulus-QRSend duration (s-QRSend) was the narrowest in IVSP1 rather than in NS-LBBP, and stimulus-to-peak of R wave in V6 (s-LVAT) was significantly shortened in two steps, from RVSP to IVSP1 (96 ± 11; 82 ± 8 ms, p < .01) and from LVSeP to NS-LBBP (76 ± 7; 60 ± 4 ms, p < .01). The late-R duration in V1 was significantly prolonged in the order of LVSeP, NS-LBBP, and S-LBBP (45 ± 7; 53 ± 10; 71 ± 15 ms, respectively, p < .01). CONCLUSIONS: s-QRSend was the narrowest in IVSP1 rather than in NS-LBBP among the QRS morphologies observed during lead penetration through the VS. The prolonged late-R duration in V1 and abrupt shortening of the s-LVAT in V6 may help determine LBB capture during lead penetration.

The Influence of Right Ventricular Pacing Location, Pacing Burden and Paced QRS Duration to Subclinical Left Ventricular Systolic Dysfunction as Shown by Global Longitudinal Strain Echocardiography.

BACKGROUND: Prolonged pacing of the right ventricle (RV) is associated with left ventricular (LV) systolic dysfunction. Several studies have shown that the RV pacing location, pacing burden (percentage), and paced QRS duration may affect LV systolic function. Subclinical LV dysfunction may occur early after implantation of a permanent pacemaker (PPM). Therefore, this study aims to detect early subclinical LV systolic dysfunction measured by global longitudinal strain (GLS) using speckle tracking echocardiography (STE) at one month after PPM implantation. METHODS: A single-center, prospective cohort study was conducted, and all patients indicated for PPM implantation with preserved LV systolic function were included. Data of RV pacing location (RV apical vs right ventricular outflow tract (RVOT), pacing burden (percentage) (≤40% vs >40%), and paced QRS duration (≤150 ms and >150 ms) were obtained. The change of GLS was also measured before and one month after PPM implantation (delta GLS). RESULTS: 37 patients were enrolled in this study, which demonstrated significant difference between GLS before (-20.30 SD 3.38) and after (-16.93 SD 3.47) PPM implantation (p=<0.001). There were no significant difference in delta GLS either between patients with RV pacing location on RV apical vs RVOT ((2.30 (0.00-10.50) vs 2.95(0.10-8.30), p=0.648) or between patient with paced QRS duration ≤150ms vs >150ms ((1.70 (0.30-8.30) vs 3.45 (0.0-10.5)), p=0.266). Meanwhile, there was a significant difference of delta GLS between patients with pacing burden ≤40% vs >40% (Mean 1.92 SD 1.37 vs 3.98 SD 3.04), p=0.007). Further analysis found that pacing burden only affected the delta GLS in group with apical RV pacing (≤40% (1.58 SD 0.59) vs > 40% (4.67 SD 3.47), p = 0.008) and did not affect the delta GLS in group with RVOT pacing (≤40% (2.32 SD 1.98) vs > 40% (3.29 SD 2.48), p = 0.446). CONCLUSION: The pacing parameter, particularly pacing burden > 40% may induce the subclinical LV systolic dysfunction after one month of pacemaker implantation as shown by decline of GLS,  especially when the RV pacing location was placed on apical.

New ECG markers for predicting long-term mortality and morbidity in patients receiving cardiac resynchronization therapy.

We investigated prognostic value of four recently proposed ECG markers in patients with cardiac resynchronization therapy (CRT): 1./ pathological preimplantation QRS axis, 2./ increase in QRS amplitude in V3 during biventricular pacing, 3./ negative QRS in V1/V2 during left ventricular (LV)-only pacing, 4./ longer QRS duration during LV-only pacing. A longitudinal cohort study was performed (n = 552). RESULTS: During the 9-year observation period the primary endpoint (death from any cause or urgent heart transplantation) was met in 232 patients. The secondary endpoint of survival free of heart failure hospitalization was met in 292 patients. Long LV-paced QRS and pathological axis predicted unfavorable prognosis in Kaplan-Meier analysis. In multivariable Cox model (functional class, LV ejection fraction, LV end-diastolic dimension, permanent atrial fibrillation, age, gender, heart failure etiology, creatinine level, diabetes mellitus), LV-paced QRS duration remained a significant determinant of both endpoints. The other studied ECG markers lacked independent prognostic value.

Paced QRS duration and myocardial scar amount: predictors of long-term outcome of right ventricular apical pacing.

Long-term right ventricular apical pacing (RVAP) is reportedly associated with heart failure (HF) development. However, the predictors of pacing-induced HF (PHF) remained unclear. We retrospectively enrolled 234 patients without structural heart disease who underwent a permanent pacemaker implantation with RVAP between 1982 and 2004. RVAP-induced HF was defined as left ventricular ejection fraction decrease >5 % with HF symptom without other HF development etiology. The QRS duration of a paced beat (pQRSd) and myocardial scar score were analyzed from each patient's 12-lead ECG. During a mean 15.6 years (range 3.3-30.0 years), 48 patients (20.5 %) patients developed RVAP-induced HF. The PHF group patients had a longer pQRSd (192.4 ± 13.5 vs. 175.7 ± 14.7 ms in non-PHF patients, p < 0.001) and a higher myocardial scar score (5.2 ± 1.9 vs. 2.7 ± 1.9, respectively p < 0.001). In multivariate Cox regression analysis, old age at implantation [Hazard ratio (HR) 1.62, 95 % confidential interval (CI) 1.22-2.16, p = 0.001], a longer pQRSd (HR 1.54, 95 % CI 1.15-2.05, p = 0.003), a higher myocardial scar score (HR 1.23, 95 % CI 1.03-1.49, p = 0.037), and a higher percentage of ventricular pacing (HR 1.31, 95 % CI 1.01-1.49, p = 0.010) were independent predictors of PHF. Based on the results of the receiver-operating characteristic (ROC) curve, the pQRSd cutoff was 185 ms (AUC 0.79, sensitivity 66.7 %, specificity 76.3 %) and myocardial scar score cutoff value was 4 (AUC 0.81, sensitivity 81.3 %, specificity 66.1 %). The pQRSd was positively correlated with scar score (r = 0.70, p < 0.001). pQRSd ≥185 ms and/or myocardial scar score ≥4 might be independent long-term prognostic markers of PHF.

Paced QRS duration predicts left ventricular function in patients with permanent pacemakers - One-year follow-up study using equilibrium radionuclide angiography (ERNA).

Permanent pacing, being non physiological, often results in ventricular dysfunction over time. Narrower paced QRS duration from pacing the right ventricular outflow tract septum, might result in relatively preserved ventricular function over long term follow up.

Clinical outcomes of left bundle branch pacing compared to right ventricular apical pacing in patients with atrioventricular block.

BACKGROUND: Left bundle branch pacing (LBBP) can produce near normalization of QRS duration. This has recently emerged as alternative technique to right ventricular pacing and His bundle pacing. HYPOTHESIS: The purpose of this study is to evaluate clinical outcomes of LBBP compared to right ventricular apical pacing (RVAP). METHODS: A total of 70 AVB patients with indications for ventricular pacing were retrospectively studied. LBBP was attempted in 33 patients, classified as LBBP group. The other patients were classified as RVAP group. Pacing parameters, electrocardiogram and echocardiogram characteristics, heart failure hospitalization (HFH), and atrial fibrillation (AF) were evaluated perioperatively and at follow-ups. Patients were followed in the device clinic for a minimum of 12 months and up to 24 months at a 3-6 monthly interval. RESULTS: LBBP was successful in 29 of 33(87.9%) patients while all 37 of the remaining patients successfully underwent RVAP. Paced QRS duration was significantly narrower in the LBBP group compare to RVAP(110.75 ± 6.77 ms vs. 154.29 ± 6.96 ms, p = .000) at implantation, and the difference persisted during follow-ups. Pacing thresholds (at implantation: 0.68 ± 0.22 V in the LBBP group and 0.73 ± 0.23 V in the RVAP group, p = .620) remained low and stable during follow-ups. The cardiac function in the LBBP group remained stable during follow-ups (LVEF%:55.08 ± 4.32 pre-operation and 54.17 ± 4.34 at the end of follow-up, p = .609), and better than RVAP group (LVEF%: 54.17 ± 4.34 vs. 50.14 ± 2.14, p = .005). Less HFH was observed in the LBBP group (2/29,6.89%) compared to RVAP group (10/37,27.03%). CONCLUSIONS: The present investigation demonstrates the safety and feasibility of LBBP that produces narrower paced QRS duration than RVAP. LBBP is associated with reduction in the occurrence of pacing-induced left ventricular dysfunction and HFH compared to RVAP in patients requiring permanent pacemakers.