Prevalence and management of chronotropic incompetence in heart failure.

Although chronotropic incompetence (CI) has been shown to have important prognostic value in asymptomatic and coronary artery disease populations, much less attention has been given to the prevalence and impact of CI in heart failure. There is considerable variability in the reported prevalence of chronotropic impairment (25%-70%) in the heart failure literature, likely due to a lack of a standardized definition and/or differing assessment methodologies. Although the exact prevalence of CI is debatable and the precise pathophysiologic mechanisms involved remain uncertain, there is unambiguous evidence indicating that chronotropic impairment contributes significantly to the myriad of cardiovascular, neuromuscular, pulmonary, and neurohormonal maladaptations known to negatively impact the physical functional and quality of life of most heart failure patients. Specifically, an inappropriate chronotropic response to exercise can decrease peak exercise oxygen uptake by as much as 15% to 20%. Therapeutic interventions to improve chronotropic function, including endurance exercise training and rate-adaptive pacing, although promising, still warrant further investigation.