Clinical Research Directory

Inclusion Criteria: * Patient must indicate acceptance to participate in the study by signing an informed consent document. * Patient must be ≥ 18 years of age. * Left bundle branch block, QRS ≥130 and LVEF \<=35%. No indication of stimulation for AV block. * Non-left bundle branch block, QRS ≥150 and LVEF \<=35%. * Resynchronization therapy indication for ventricular dysfunction (LVEF \<40%) and indication of cardiac pacing for AV block. * LVEF \<=35% in NYHA class III or IV, atrial fibrillation and intrinsic QRS \>=130 ms, provided a strategy to ensure biventricular capture is in place. Exclusion Criteria: * Myocardial infarction, unstable angina or cardiac revascularization during the previous 3 months. * Pregnancy. * Participating currently in a clinical investigation that includes an active treatment.