Latin America Cardiac Resynchronization Therapy Study

The purpose of this study is to provide local evidence regarding Cardiac Resynchronization Therapy (CRT), in both pacing and defibrillation devices across Latin America. The primary objective will focus on changes in left ventricular heart size and function measurements in subjects receiving CRT therapy. The following additional parameters will also be collected: * Data on referral patterns in Latin America; * Data on device implant (including delivery system, device information, and lead information); * Clinical data on subject outcomes and changes (improved, unchanged, or worsened) in heart failure status as assessed by heart failure (HF) hospitalizations, New York Heart Association (NYHA) class, mortality, and Quality of Life (QOL) measured by the Patient Global Assessment;

Inclusion Criteria: Implant of new CRT-D or CRT-P device (first-time implant), ACC/AHA/HRS/ESC guidelines for implant, NYHA Class II, III or IV, QRS duration \>120 ms, LVEF \< 35%, Receiving optimal medical/drug therapy, Able to give written informed consent, Are \> 21 years of age, Must be able to return for follow-up visits as required, Are not pregnant or do not plan to get pregnant within the next 6 months, Have no physical limitations to perform Echo studies Exclusion Criteria: Previous or existing CRT system implanted, Unwilling or unable to comply with specified follow-up schedule, Enrolled or intending to participate in another device study during the course of this study that requires specific treatment or device programming, Medical condition that may limit life expectancy to \< 6 months