Repetitive nocturnal arterial oxygen desaturation and silent myocardial ischemia in patients presenting for vascular surgery.

OBJECTIVE: To determine whether nocturnal respiratory abnormality (cyclic 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: Tertiary care referral hospital. PATIENTS: Thirty four consecutive older (68.5 +/- 6 yrs) patients referred for elective abdominal or carotid reconstructive vascular surgery.
RESULTS: Seven patients (21%) had moderately severe nocturnal respiratory abnormality, defined by more than 50 dips in arterial oxygen saturation and increases in heart rate during the night. Two of these seven had clinical risk factors for ischemic heart disease and had nocturnal myocardial ischemia. Ten patients (29%) developed ischemia at some time during the study, of whom seven hand known ischemic heart disease, hypertension, and/or angina. Those with increased nocturnal ischemia showed very low frequency (1-2 cycles per minute) cyclic heart rate oscillations and repetitive nocturnal episodes of arterial oxygen desaturation, similar to patients with sleep apnea.
CONCLUSION: Repetitive nocturnal cyclic arterial desaturation and cyclic increases in heart rate are associated with nocturnal myocardial ischemia in individuals with clinical risk factors for ischemic heart disease. Further investigation in a large patient sample utilizing non-invasive monitoring of saturation, heart rate, and blood pressure may provide definitive evidence regarding causation of some of the nocturnal myocardial ischemia occurring in older individuals with vascular disease.