Heart rate nonlinear dynamics during sudden hypoxia at 8230 m simulated altitude.

Objective: Acute hypobaric hypoxia is associated with autonomic changes that bring a global reduction of linear heart rate variability (HRV). Although changes in nonlinear HRV can be associated with physiologic stress and are relevant predictors of fatal arrhythmias in ischemic heart disease, to what extent these components vary in sudden hypobaric hypoxia is not known.

Methods: Twelve military pilots were supplemented with increasing concentrations of oxygen during decompression to 8230 m in a hypobaric chamber.

Nonlinear analysis of heart rate variability within independent frequency components during the sleep-wake cycle.

Heart rate variability (HRV) is a complex signal that results from the contribution of different sources of oscillation related to the autonomic nervous system activity. Although linear analysis of HRV has been applied to sleep studies, the nonlinear dynamics of HRV underlying frequency components during sleep is less known. We conducted a study to evaluate nonlinear HRV within independent frequency components in wake status, slow-wave sleep (SWS, stages III or IV of non-rapid eye movement sleep), and rapid-eye-movement sleep (REM).

Nonlinear analysis of heart rate variability in patients with eating disorders.

Patients with anorexia nervosa or bulimia nervosa often have signs of autonomic dysfunction potentially deleterious to the heart. The aim of this study was to ascertain the nonlinear properties of heart rate variability in patients with eating disorders. A group of 33 women with eating disorders (14 anorexia, 19 bulimia) and 19 healthy controls were included in the study.

Circadian analysis of myocardial infarction incidence in an Argentine and Uruguayan population.

Background: The occurrence of variations in the spectrum of cardiovascular disease between different regions of the world and ethnic groups have been the subject of great interest. This study report the 24-h variation of myocardial infarction (MI) occurrence in patients recruited from CCU located in Argentina and Uruguay.

Method: A cohort of 1063 patients admitted to the CCU within 24 h of the onset of symptoms of an acute MI was examined.

Wavelet transform shows age-related changes of heart rate variability within independent frequency components.

Reduction in overall heart rate variability (HRV) associated with aging is determined by a decreased amplitude of heart rate oscillations at all frequency levels, including high frequency (HF) oscillations attributed to respiratory sinus arrhythmia, low frequency (LF) oscillations attributed to Meyer waves and very low frequency (VLF) oscillations of an uncertain origin, presumably linked among others to thermoregulation. However, no studies were conducted to determine whether heart rate oscillations at independent frequency levels show themselves reduced HRV. Wavelet transform was applied to filter specific frequency components of HRV in a sample of younger (21-34 years old) and older (68-85 years old) healthy subjects.

Circadian periodicity of heart rate variability in hospitalized angor patients.

The relationship between unstable angor (angina) and circadian periodicity of heart rate variability (HRV) was explored in a group of patients hospitalized in a coronary care unit (CCU). Patients were classified as normal (whose symptoms had non-cardiovascular origin, n=8), moderate angor (n=13) and severe angor (n=11). A fourth group of ambulatory healthy volunteers (n=12) was included.

Worsening of depressive symptoms 6 months after an acute coronary event in older adults is associated with impairment of cardiac autonomic function.

Background: Depression increases mortality of coronary patients, and autonomic dysfunction has been proposed as an explanation for this association.

Methods: In a sample of 38 adults > or = 60 years with myocardial infarction or unstable angina, we studied depression (presence of a major depressive episode and 21-item Hamilton depression score) and heart rate variability (HRV) of 550 normal beats shortly after admission to the coronary care unit (CCU). Thirty patients were alive at 6 months and were studied at that time as well.

Relation of depression to heart rate nonlinear dynamics in patients > or =60 years of age with recent unstable angina pectoris or acute myocardial infarction.

Depression is common among older patients and it has been related to a worsened coronary prognosis. The basis for this association is controversial. The aim of this study was to ascertain whether patients with a recent acute coronary event show depression-related changes of heart rate variability (HRV) nonlinear dynamics.

Cardiac parasympathetic dysfunction related to depression in older adults with acute coronary syndromes.

Objective: To determine whether depression is associated with cardiac autonomic alterations in elderly patients with recent acute coronary syndromes (ACSs).

Methods: Cross-sectional study on the association between a major depressive episode or isolated depressive symptoms (21-item Hamilton depression score) and heart rate variability abnormalities in 56 adults (31 women, 55%) 60 years of age and older with a recent (24-72 h) myocardial infarction (MI) or unstable angina (UA).

Results: Spectral and nonspectral parameters of respiratory sinus arrhythmia, indicative of parasympathetic activity on the heart, were decreased in patients with depression (high-frequency heart rate variability [log ms(2)] 2.