What is the lowest value of left ventricular baseline ejection fraction that predicts response to cardiac resynchronization therapy?

Background: Cardiac resynchronization therapy (CRT) is an effective treatment option for patients with refractory heart failure. However, many patients do not respond to therapy. Although it has been thought that there was no relation between response to CRT and baseline ejection fraction (EF), the response rate of patients with different baseline LVEF to CRT has not been evaluated in severe left ventricular systolic dysfunction. We aimed to investigate any difference in response to CRT between the severe heart failure patients with different baseline LVEF. Material/Methods: In this study, 141 consecutive patients (mean age 59 +/- 13 years; 89 men) with severe heart failure and complete LBBB were included. Patients were divided into 3 groups according to their baseline LVEF: 5-15%, Group 1; 15-25%, Group 2, and 25-35%, Group 3. NYHA functional class, LVEF, LV volumes, and diameters were assessed at baseline and after 6 months of CRT. A response to CRT was defined as a decrease in LVSVi (left ventricular end-systolic volume index) >= 10% on echocardiography at 6 months. Results: After 6 months, a significant increase of EF and a significant decrease of LVESVi and LVEDVi after 6 months of CRT were observed in all groups. Although the magnitude of improvement in EF was biggest in the first group, the percentage of decrease in LVESVi and LVEDVi was similar between the groups. The improvement in NYHA functional class was similar in all EF subgroups. At 6-month follow-up, 100 (71%) patients showed a reduction of >10% in LVESVi (mean reduction: -15.5 +/- 26.1 ml/m(2)) and were therefore classified as responders to CRT. Response rate to CRT was similar in all groups. It was 67%, 75%, and 70% in Group 1, 2, and 3, respectively, at 6-month follow-up (p>0.05). There was no statistically significant relation between the response rate to CRT and baseline LVEF, showing that the CRT has beneficial effects even in patients with very low LVEF. Conclusions: It seems there is no lower limit for baseline LVEF to predict non-response to CRT in eligible patients according to current guidelines.