[Myocardial infarction and nocturnal hypoxaemia].

Introduction: There is an increased risk of cardiovascular morbidity and mortality in patients with nocturnal intermittent hypoxaemia.
Objective: The aim of this study was to evalute the influence of nocturnal hypoxaemia on ventricular arrhythmias and myocardial ischaemia in patients with myocardial infarction (MI).
Method: We studied 77 patients (55.8 +/- 7.9 years) with MI free of complications, chronic pulmonary diseases, abnormal awake blood gases tension. All patients underwent overnight pulse oximetry and 24-hour electrocardiography. Patients were divided into two groups according to nocturnal hypoxaemia. Total number of ventricular premature complex (VPC); maximal VPC/h; incidence of VPC Lown class > 2 and occurrence of ST-segment depression were analysed for nocturnal (10 PM to 6 AM), daytime (6 AM to 22 PM) periods and for the entire 24 hours.
Results: Both groups were similar in age, gender, standard risk factors, myocardial infarction size and did not differ in VPC during the analysed periods. The number of nocturnal maximal VPC/h was insignificantly greater in group 1 (with hypoxaemia) compared to group 2 (without hypoxaemia), (p = 0.084). Maximal VPC/h did not differ significantly either for daytime or for 24 hours among the groups. Nocturnal VPC Lown > 2 were significantly more frequent in group 1 (25% vs 0%, p = 0.002). The incidence of VPC Lown > 2 was similar during the daytime, and during 24 hrs in both groups. Occurrence of ST-segment depression did not differ between groups 1 and 2.
Conclusion: Nocturnal hypoxaemia was associated with complex nocturnal ventricular arrhythmias in patients with MI.