OBJECTIVE To evaluate the incidence of sleep apnoea in acute and chronic coronary syndromes.

DESIGN Analysis of sleep and breathing characteristics in a polysomnographic study.

SETTING Cardiology department in tertiary referral centre.

PATIENTS 23 patients were studied soon after acute myocardial infarction (group 1), 22 after clinical stabilisation of unstable angina (group 2), and 22 who had stable angina (group 3). Conditions liable to cause sleep apnoea, such as obesity, chronic obstructive pulmonary disease, neurological disorders, or the use of benzodiazepines, were exclusion criteria.

MAIN OUTCOME MEASURES Sleep apnoea and hypopnoea, oxygen saturation, and sleep indices evaluated soon after clinical stabilisation in groups 1 and 2 and also in group 3.

RESULTS Sleep apnoea, mainly of the central type, was equally present in groups 1 and 2 (mean (SD) apnoea-hypopnoea index: 11.10 (19.42) and 14.79 (20.52), respectively) and more severe than in group 3 (2.82 (6.43), p < 0.01). Total time spent at Sao ₂ < 90%, although significantly greater in group 1 and 2 (0.89 (2.4), 1.42 (3.23) min) than in group 3 (0.01 (0.05) min, p < 0.05), was clinically irrelevant. More arousals per hour of sleep (p < 0.05) were detected in group 1 (5.15 (3.71)) and group 2 (5.31 (2.14)) than in group 3 (2.83 (1.51)).

CONCLUSIONS Sleep apnoea, chiefly of the central type, not only characterises acute myocardial infarction, as found by others, but also unstable angina studied after recent stabilisation. Patient selection by exclusion of other causes of breathing disorders shows that coronary disease related apnoea is absent in the chronic coronary syndrome. In acute syndromes the lack of clinically significant apnoea related oxygen desaturation, together with the low associated incidence of major ischaemic and arrhythmic events, suggests that sleep apnoea is benign in these circumstances, despite a worsening of sleep quality.