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Ivcd symptoms5/2/2023 However, QRS morphology and QRS duration are not perfect indicators of electrical dyssynchrony, which is the cause of the not negligible non-response rate to CRT and the missed CRT implantation in a significant number of patients who have the appropriate substrate for CRT. The current guidelines recommend the determination of QRS morphology and QRS duration and the measurement of left ventricular ejection fraction for patient selection for CRT. The main determinant of CRT outcome is the presence or absence of significant ventricular dyssynchrony and the ability of the applied CRT technique to eliminate it. However, the non-response rate to CRT is still 20%-40%, which can be decreased by better patient selection. The annual incidence of new‐onset LBBB was around 2.5%, and associated with a higher risk of adverse outcomes, highlighting the importance of repeat ECG review.Ĭardiac resynchronization therapy (CRT) is an evidence-based effective therapy of symptomatic heart failure with reduced ejection fraction refractory to optimal medical treatment associated with intraventricular conduction disturbance, that results in electrical dyssynchrony and further deterioration of systolic ventricular function. In patients with HFrEF, a wide QRS was associated with worse clinical outcomes irrespective of morphology. Incident LBBB occurred in 495 (6.3%) patients (2.4 per 100 py) and was associated with a higher risk of the primary composite outcome HR 1.42 (1.12, 1.82). A total of 1,234 (15.6%) patients developed new‐onset QRS‐widening ≥130 ms (6.1 per 100 py). During a median follow‐up of 2.5 years, the risk of the primary composite endpoint was higher among those with a wide QRS, irrespective of morphology: hazard ratios (95% CI) LBBB 1.36 (1.23, 1.50), RBBB 1.54 (1.31, 1.79), nonspecific IVCD 1.65 (1.40, 1.94) and QRS 110‐129 ms 1.35 (95% CI 1.23, 1.47), compared with QRS duration <110 ms. Risk of the primary composite outcome of cardiovascular death or HF hospitalization and all‐cause mortality were estimated by use of Cox regression according to baseline QRS duration and morphology in 11,861 patients without an intracardiac device. We addressed these questions in the PARADIGM‐HF and ATMOSPHERE trials. The importance of intraventricular conduction delay (IVCD), incidence of new IVCD and its relationship to outcomes in heart failure and reduced ejection fraction (HFrEF) is not well studied.
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