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Introduction: Right ventricular (RV) pacing sometimes causes left ventricular (LV) systolic dysfunction, also known as pacing‐induced cardiomyopathy (PICM). However, the association between specifically paced QRS morphology and PICM development has not been elucidated. This study aimed to investigate the association between paced QRS mimicking a complete left bundle branch block (CLBBB) and PICM development. Methods: We retrospectively screened 2009 patients who underwent pacemaker implantation from 2010 to 2020 in seven institutions. Patients who received pacemakers for an advanced atrioventricular block or bradycardia with atrial fibrillation, baseline LV ejection fraction (LVEF) ≥ 50%, and echocardiogram recorded at least 6 months postimplantation were included. The paced QRS recorded immediately after implantation was analyzed. A CLBBB‐like paced QRS was defined as meeting the CLBBB criteria of the American Heart Association/American College of Cardiology Foundation/Heart Rhythm Society in 2009. PICM was defined as a ≥10% LVEF decrease, resulting in an LVEF of <50%. Results: Among the 270 patients analyzed, PICM was observed in 38. Baseline LVEF was lower in patients with PICM, and CLBBB‐like paced QRS was frequently observed in PICM. Multivariate analysis revealed that low baseline LVEF (odds ratio [OR]: 0.93 per 1% increase, 95% confidence interval [CI]: 0.89–0.98, p = 0.006) and CLBBB‐like paced QRS (OR: 2.69, 95% CI: 1.25–5.76, p = 0.011) were significantly associated with PICM development. Conclusion: CLBBB‐like paced QRS may be a novel risk factor for PICM. RV pacing, which causes CLBBB‐like QRS morphology, may need to be avoided, and patients with CLBBB‐like paced QRS should be followed‐up carefully. [ABSTRACT FROM AUTHOR]

Purpose: Prolonged QRS duration is the main selection criterion for cardiac resynchronization therapy (CRT) which ameliorates left ventricular mechanical dyssynchrony (MD). However, consequences of post-CRT QRS prolongation and residual MD have been poorly evaluated. We aimed to define the predictors of persistent MD and hypothesized that CRT-induced QRS change (ΔQRS) might have an impact on residual MD after CRT.Methods: A total of 80 patients receiving CRT were included in the study. ΔQRS was calculated as the difference between the baseline and paced QRS intervals. Residual MD was assessed early after device implantation with a longitudinal dyssynchrony index (Yu index). Significant MD was defined as a Yu index ≥ 33 msec. Two groups were created based on residual MD and compared according to clinical, electrocardiographic and echocardiographic features.Results: Patients with persistent MD had longer paced QRS durations (182.5 ± 16.2 vs. 165.4 ± 22.5 msec, p = 0.03) and were less likely to have left ventricular (LV) leads located in the posterolateral vein (53 % vs. 85 %, p = 0.002). The linear correlation between the ΔQRS and the Yu index values was modest (Spearman's rho = -0.341, p = 0.002); additionally, a prolonged QRS was strongly associated with MD after CRT (p = 0.00008). Both LV lead localization and CRT-induced QRS prolongation emerged as the significant predictors of persistent MD. A biventricularly paced QRS more than 10 msec longer than the pre-paced QRS width was predictive of persistent MD after CRT (sensitivity = 80 %, specificity = 62 %).Conclusions: ΔQRS was found to be associated with residual MD after CRT. Ten milliseconds of QRS prolongation predicted persistent MD after CRT. [ABSTRACT FROM AUTHOR]

Left bundle branch block (LBBB) is known to impair the mechanical function of the left ventricle. For a better understanding of the impact of LBBB on the structure and function of the heart and how this influences the management and outcome in patients with heart failure, we reviewed the most pertinent articles published from 1950 to 2007. Epidemiological studies identified LBBB as an independent risk factor for cardiac mortality. It is not only the morphology or duration of QRS but also the underlying myocardial pathology, ejection fraction or New York Heart Association class that may determine the clinical implications of LBBB. Data indicate that LBBB inversely affects the perfusion, systolic, diastolic performance and hemodynamics of the heart. However, there is no solid evidence answering the question of whether LBBB is a predictor, cause or consequence of myocardial dysfunction. Further studies are warranted for better understanding of these relationships, as this will allow better selection of patients and optimal time for resynchronization therapy in patients with LBBB. [ABSTRACT FROM AUTHOR]

A 52-year-old man was implanted with a Gemini pacemaker for complete heart block which developed suddenly three months after coronary reconstruction and endocardial resection to treat chronic recurrent ventricular tachycardia. Pacemaker alternans, which is a rare phenomenon, occurred two days after pacemaker implantation and then disappeared 24 hours later. The patient was followed for a two-month period during which the pacemaker system functioned normally. Many of the possible mechanisms which may produce pacemaker alternans were explored. Our findings are presented in this report. [ABSTRACT FROM AUTHOR]