Role of electrocardiographic and echocardiographic types of left bundle branch block in prediction of response to cardiac resynchronization therapy

AIM: To assess the value of the complex analysis of electrocardiographic (ECG) variants and echocardiographic (echo) manifestation of left bundle branch block (LBBB) in predicting the success of cardiac resynchronization therapy (CRT). MATERIALS AND METHODS: The study included 39 patients (mean age 61.49±9.0 years) on sinus rhythm with LBBB, QRS duration ≥130 ms, left ventricular ejection fraction (LVEF) ≤35%, heart failure (HF) NYHA II-IV despite optimal pharmacological therapy during 3 month. All patients had undergone CRT-D implantation. Depending on presence or absence of ECG-criteria, proposed by D.G. Strauss et al., patients were divided into 2 groups: 1 group - strict LBBB, proposed by D.G. Strauss et al. (n=29) and 2 group - other patients (n=10). In addition to standard echocardiography, global longitudinal 2-dimensional strain (GLS) and LBBB contraction pattern have been performed initially and in 6 months after implantation. Response to CRT was defined as decrease in LV end-systolic volume by >15% after 6 months of follow-up. RESULTS: Typical LBBB echo contraction pattern was detected in 25 patients (64% of all included). These patients had more pronounced longitudinal dissynchrony and a more expressed global longitudinal strain before CPT-D implantation (p<0.05). 27 patients (69% of all included) were included in the "response" group, the remaining 12 patients (31% of all included) - the "non-response" group. In the "response" group the morphology of the QRS complex was significantly more likely to meet the criteria, proposed by D.G. Strauss et al., than other variants (23 vs. 6, respectively, p=0.02), and the echo contraction pattern of this patients more often corresponded to "typical" LBBB (24 vs. 1, p=0.001). All patients, who had the ECG criteria, proposed by D.G. Strauss et al., and echo "typical" LBBB contraction pattern, responded on CPT. Moreover, the proportion of these patients in the "response" group was rather high - 81.5% (22 of 27 patients). CONCLUSION: ECG criteria LBBB, proposed by D.G. Strauss et al., identify patients with delayed transseptal interventricular conduction due to complete LBBB, what is a good target for CPT. Evaluation of the echo contraction pattern based on the definition of longitudinal myocardial deformation by means of a two-dimensional strand technology allows predicting the success of CPT in patients with LBBB. Patients with «typical» LBBB contraction pattern show more pronounced global longitudinal strain and larger longitudinal dissynchrony compared with other patients, and it explains their better response to CPT. Complex analysis of strict LBBB ECG criteria and echo contraction pattern are promising parameters in predicting beneficial response to CRT in patients with HF.