The effect on the heart of hypoxaemia in patients with severe coronary artery disease.

The aim of the study was to examine the effect of spontaneous nocturnal hypoxaemia on myocardial ischaemia in patients with severe coronary artery disease. This was a prospective study of continuously measured oxygen saturation and ECG overnight in patients prior to coronary artery bypass graft surgery. Fifteen patients with angiographically proved coronary artery disease were studied between October 1992 and September 1993. All patients had episodes of hypoxaemia with oxygen saturation < 94% and eight of the 15 patients had episodes where oxygen saturation < 85%. An episode was defined as a period of hypoxaemia not less than 2.5 min in duration, the longest total duration of hypoxaemia in one patient being 355 min. Twelve of the 15 patients showed a drop in ST segment of 1 mm or more lasting from 5-700 min. The hypoxaemic and ischaemic episodes apparently occurred at random. No causal relationship could be shown between hypoxaemia and ischaemia.