Circadian variations in total ischaemic burden and ischaemic threshold.

Myocardial ischaemia in daily life varies according to a circadian rhythm and is induced by many factors, including both increased myocardial oxygen demand and changes in coronary tone. In most patients, ischaemia is induced by a combination of different contributing factors, although the relative contribution of each mechanism varies from patient to patient. Moreover, in the same individual, various episodes may be due to different mechanisms. The relative contributions of increased myocardial oxygen demand and decreased ischaemic threshold to the development of ischaemia in daily life can be assessed by continuous ambulatory ECG monitoring which may help to optimize medical anti-ischaemic therapy.