Association between resting heart rate, chronotropic index, and long-term outcomes in patients with heart failure...

Area of Science:

• Cardiology
• Clinical Medicine
• Exercise Physiology

Background:

• Heart failure (HF) management involves optimizing medical therapy, including beta-blocker use.
• Assessing heart rate reserve during exercise is crucial for evaluating cardiovascular health.
• The chronotropic index (CI) quantifies heart rate reserve, reflecting the heart's ability to increase rate during exertion.

Purpose of the Study:

• To investigate the association between chronotropic index (CI) and clinical outcomes in chronic heart failure (HF) patients receiving optimal beta-blocker therapy.
• To determine if resting heart rate (HR) or CI predicts adverse events in this patient population.

Main Methods:

• A sub-study of 1118 HF patients from the HF-ACTION trial with reduced ejection fraction (<35%) was analyzed.
• Patients in sinus rhythm, on beta-blockers, and who exerted maximal effort during exercise testing were included.
• Cox proportional hazards models assessed the relationship between CI and outcomes, with CI calculated using standard and HF-specific equations.

Main Results:

• Neither resting HR nor CI, as continuous variables, were associated with the primary outcome of all-cause mortality or hospitalization.
• A decrease in CI below 0.6 was linked to a 17% increased risk of all-cause mortality (HR 1.17) and a 13% increased risk of cardiovascular mortality or HF hospitalization (HR 1.13).
• Approximately 60% of patients exhibited a CI below 0.6, but CI did not remain significant when dichotomized at 0.62.

Conclusions:

• In optimally treated HF patients on beta-blockers, a chronotropic index below 0.6 is associated with adverse clinical outcomes.
• Achieving an optimal heart rate response to exercise may represent a potential therapeutic target in heart failure management.