|Inclusion Criteria||Exclusion Criteria|
|Previous diagnosis of chronic heart failure||Major cardiovascular event within 6 weeks before enrollment|
|Cardiac resynchronization therapy device implanted at least 6 months before enrollment||Uncontrolled hypertension|
|History of symptomatic congestive heart failure (NYHA functional class II–IV)||Inability to walk on treadmill|
|Prior ejection fraction <40% or documented moderate to severely impaired systolic dysfunction|
|Stable medical therapy for heart failure|
|>90% biventricular pacing|
NYHA = New York Heart Association.