Chronotropic Incompetence

Chronotropic incompetence (CI), the inability of the heart rate to increase appropriately in response to an increase in activity or metabolic demand,^1,2  occurs because of altered balance between the sympathetic and parasympathetic branches of the autonomic nervous system.^3,4  Chronotropic incompetence is common in various types of cardiac disease including sick sinus syndrome, atrioventricular (AV) block, coronary artery disease, and heart failure^5,6  and is also seen in patients with no structural heart disease.^7–9  Chronotropic incompetence first appeared in the literature in 1975 when a high rate of cardiac events was observed in those with a decreased heart rate (HR) response during treadmill exercise test.¹⁰ 

Although often not recognized, CI is frequently present in heart failure, which is a common reason for hospital admission and a common comorbid condition in patients admitted for noncardiac reasons. Implantable cardiac devices may...