ABSTRACT
OBJECTIVES: The purpose of this study was to investigate the association of central sleep apnea (CSA) and baroreflex sensitivity (BRS) after acute myocardial infarction. BACKGROUND: Both, CSA and blunted BRS have been shown to be independent predictors for cardiovascular mortality in patients with heart failure. But in contrast to BRS, which has been extensively studied in the setting of AMI, the incidence of CSA in patients recovering from AMI is thus far unknown. As previous reports suggested a potential role of sleep apnoea in augmenting reflex autonomic modulation, we hypothesized that there is a strong interrelation between CSA and BRS. METHODS: Seventeen male patients in the subacute phase of a first uncomplicated ST-segment elevation AMI and eight healthy male controls without evidence of coronary artery disease underwent polysomnography with simultaneous beat-to-beat ECG- and blood-pressure recordings. Sleep stage specific spontaneous BRS was calculated from blood pressure and RR-interval fluctuations by using the time domain sequential technique. RESULTS: AMI patients revealed to have a higher incidence and longer duration of central apnoeas in all sleep stages, light sleep, deep sleep and dream sleep. There were no significant sleep stage specific differences regarding BRS between groups, however, AMI patients with central sleep apnea exhibited blunted BRS which was inversely correlated to incidences of central apnea in all sleep stages. CONCLUSIONS: Our findings suggest a direct relationship between impaired BRS and repetitive occurrence of CSA by inverse correlation in all sleep stages in the subacute phase of AMI. Thus, reflex cardiac autonomic nervous control, being represented by the BRS, may be the link between CSA and prognosis.
Subject(s)
Baroreflex , Myocardial Infarction/complications , Oxygen/blood , Sleep Apnea, Central/complications , Adult , Aged , Blood Gas Analysis , Blood Pressure Determination , Case-Control Studies , Chi-Square Distribution , Electrocardiography , Humans , Male , Middle Aged , Myocardial Infarction/diagnosis , Oxygen Consumption/physiology , Polysomnography , Probability , Reference Values , Sensitivity and Specificity , Severity of Illness Index , Sleep Apnea, Central/diagnosis , Stroke Volume/physiologyABSTRACT
BACKGROUND: Ventricular arrhythmias after myocardial infarction (MI) are often nocturnal. However, the arrhythmogenic effects of sleep after MI are unknown. We examined the effects of sleep stages on QT dynamicity and tested the hypothesis of a differential effect of sleep stage on the QT/RR relationship after recent MI, versus in healthy controls (HC). METHODS: Polysomnography and electrocardiograms were simultaneously recorded in 21 men in the subacute phase of a first uncomplicated MI, and in 10 age-matched, male HC. QT dynamicity (QT/RR slope) and parameters of QT interval were measured during wakefulness, stages 1-4 of nonrapid eye movement (non-REM) sleep, and REM sleep. RESULTS: Mean QT and RR intervals increased through all sleep stages in both MI survivors and HC. The Bazett-corrected QT interval remained stable from wakefulness throughout all sleep stages. QT/RR slopes remained stable from wakefulness to stage 3 in both groups. However, unlike in MI survivors, the QT/RR slopes decreased and remained significantly lower during deep sleep and REM sleep in HC. CONCLUSION: An abnormal QT/RR relationship in deep sleep and REM sleep was observed after a recent MI, reflecting an insufficient shortening of ventricular repolarization with increasing heart rates, which might have important implications in the nocturnal distribution of ventricular arrhythmias after MI.
