Chronotropic incompetence: a proposal for definition and diagnosis.

Between 1958 and 1960 Astrand documented the normal heart rate response to exercise in healthy individuals and noted that the maximum heart rate decreased with age.' 2 A reduced cardiac chronotropic response to isoprenaline has been reported in elderly subjects and alterations in catecholamineadrenergic receptor interactions may be responsible for this change of cardiovascular regulation in the elderly.35 In addition the parasympathetic innervation of the sinus node is currently under investigation.6 Over the years it has also been recognised that an inadequate chronotropic response (chronotropic incompetence) at maximal exercise is common in patients with cardiac disease78 and much interest has centred on the pathophysiological mechanism(s) involved in chronotropic incompetence.910 Despite this, no universally accepted definition of chronotropic incompetence exists and the criteria for its diagnosis are not defined. However, a precise diagnosis of this condition is of clinical importance. First, adaptive-rate pacing may be beneficial in patients who clearly demonstrate chronotropic incompetence."'''4 Secondly, chronotropic incompetence has also been documented in patients with chronic heart failure and may contribute to the impairment of physical capacity seen in these patients.7 '5