Atypical left bundle branch morphology defined as QS or rS in lead V1, broad R waves in lead I, and aVL but with QS or rS in V5-V6 is associated with favorable echocardiographic response to CRT and displays similar survival rates to typical LBBB patients.Ītypical left bundle branch block Cardiac resynchronization therapy Heart failure Left bundle branch block. This subgroup of IVCD should be considered for CRT. Patients with ALBBB may have a favorable echocardiographic response to CRT and display similar survival rates to typical LBBB. Cumulative 2-year survival was 88% in ALBBB, 86% in TLBBB, and 76% in OIVCD (p value = 0.011). Both right (RBBB) and left bundle branch blocks (LBBB) are associated with adverse outcome in subjects with overt cardiovascular disease (CV Wang et al., 2008 Zhang et al., 2012 ). ![]() A multivariable model showed a lower likelihood of echocardiographic response in OIVCD and a similar likelihood in ALBBBB compared to TLBBB. The clinical significance of various intraventricular conduction delays (IVCD) depends on the type of the conduction disorder and on the studied patient population. 75% and 72%, respectively, p = 0.01 for both comparisons). Rates of echocardiographic response were lower among those with OIVCD compared to those with LBBB and ALBBB (50% vs. Endpoints were 2 years mortality and echocardiographic response, defined as a decrease of ≥ 10% in indexed LVESV or an increase of ≥ 5% in left ventricular ejection fraction at 1 year of follow-up.īaseline clinical characteristics were similar among all the three groups. ![]() ECGs were classified into the following three groups: (a) typical LBBB (TLBBB) according to accepted guidelines (n = 67) (b) IVCD with LBBB pattern criteria in V1, 1, and aVL but with QS or rS in V5-V6 which we defined as atypical LBBB (ALBBB) (n = 74) and (c) all other IVCD (OIVCD) patterns (n = 98). However, IVCD pattern is heterogeneous, and it is possible that QRS patterns may also respond to CRT.Ĭonsecutive baseline ECGs of 239 patients implanted between 20 with CRT were analyzed. Response to cardiac resynchronization therapy (CRT) is well-established in patients with typical left bundle branch block (LBBB) but modest or even negative in those with intraventricular conduction delay (IVCD).
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