The HF-HRV Registry

Inclusion Criteria: * Patients receiving their first CRT-D * Patients who sign and date a Patient Informed Consent prior to device implant * Patients who are available and willing to attend follow-up visits at the study center in which they were enrolled Exclusion Criteria: * Patients who are anticipated to receive pacing modes other than DDD or VDD (i.e., chronic atrial fibrillation patients are excluded), or patients who are anticipated to receive adaptive rate therapy * Patients who are younger than 18 years of age * Patients whose life expectancy is less than six-months due to other medical conditions * Patients with or who are likely to receive a tricuspid or other valve prosthesis * Patients who are currently enrolled in another investigational study that would directly impact the treatment or outcome of the current study * Women who are pregnant