The aim of this study was to determine if way of defining LBBB influences the response of the CRT therapy.
Patients and methods: We prospectively enrolled 111 patients (62,5% male) with heart failure in whom CRT (81,1% CRT-P, 18,9% CRT-D) was implanted. Patients with LBBB were divided in two groups: conventional LBBB - QRS=120ms, QS or rS in V1, broad R in D1, aVL, V5, V6, and absent Q in V5, V6; Strauss LBBB- QRS =130ms in female, QRS=140ms in male, QS or rS in V, midQRS notch in at least two of D1, aVL, Va, V2, V5, V6 after first 40 ms. After mean follow up of 35,4± 13,9 months, 71,2% were defined as responders (NYHA class improvement, at least 10% increase in EF), versus 28,8% non-responders. In the group with Strauss-LBBB morphology responder rate was 82,6%, compared to 71,1% in conventional LBBB morphology, and poor response in non-LBBB morphology of 46,7%, and 25% in narrow QRS (p<0.01). And more than that 58,3% of the patients defined as super-responders come from the Strauss-LBBB group. In patients with LBBB morphology, the presence of Strauss LBBB criteria is strong predictor of better response to CRT.