REPETITIVE NOCTURNAL ARTERIAL OXYGEN DESATURATION AND SILENT-MYOCARDIAL-ISCHEMIA IN PATIENTS PRESENTING FOR VASCULAR-SURGERY

Objective: To determine whether nocturnal respiratory abnormality (cyc lic oxygen desaturation and tachycardia) is associated with nocturnal myocardial ischemia in older individuals with ischemic heart disease. Design: Non-invasive monitoring on a single occasion. Setting: Tertiar y care referral hospital. Patients: Thirty four consecutive older (68. 5 +/- 6 yrs) patients referred for elective abdominal or carotid recon structive vascular surgery. Results: Seven patients (21%) had moderate ly severe nocturnal respiratory abnormality, defined by more than 50 d ips in arterial oxygen saturation and increases in heart rate during t he night. Two of these seven had clinical risk factors for ischemic he art disease and had nocturnal myocardial ischemia. Ten patients (29%) developed ischemia at some time during the study, of whom seven hand k nown ischemic heart disease, hypertension, and/or angina. Those with i ncreased nocturnal ischemia showed very low frequency (1-2 cycles per minute) cyclic heart rate oscillations and repetitive nocturnal episod es of arterial oxygen desaturation, similar to patients with sleep apn ea. Conclusion: Repetitive nocturnal cyclic arterial desaturation and cyclic increases in heart rate are associated with nocturnal myocardia l ischemia in individuals with clinical risk factors for ischemic hear t disease. Further investigation in a large patient sample utilizing n on-invasive monitoring of saturation, heart rate, and blood pressure m ay provide definitive evidence regarding causation of some of the noct urnal myocardial ischemia occurring in older individuals with vascular disease.