Ten normal male volunteers received either TOO mg alprenolol or placebo in a double-blind randomized trial. Ninety minutes later they performed a standardized Valsalva manoeuvre 40: mmHg airway pressure for 12 seconds. Beat-to-beat measurements were made of heart rate, left ventricular ejection time (LVET), ejection time index (ETI), and' corrected ejection time' (LVET/Vye). After placebo, hear...

Background: Cardiac conduction disorders are rare syndromes in neonates and children. According to the literature atrial septal defect, especially ostium secundum type, is associated with atrioventricular (AV) block. Wenckebach conduction heart block is very rare in a neonate; however, there is a dearth of research on the prevalence of this type of heart block regarding the neonates and pediatr...

The current study applies a neurophysiological model based on the Polyvagal Theory (Porges, 1995) to interpret fetal heart rate patterns. Beat-to-beat heart rate data from 7 fetuses monitored during the first and second stages of labor were analyzed. Transitory heart rate accelerations and reduced beat-to-beat variability reliably preceded heart rate decelerations. The data are interpreted with...

Although the influence of the Valsalva maneuver on the heart and circulatory system has been investigated, the mechanism of intrathoracic pressure influencing cardiovascular function is unclear. To test our hypothesis that the interaction between the anatomy-determined partially-intrathoracic system and the fully-intrathoracic system might explain those issues and help to disclose the mechanism...

Enhanced hydration increases the human cardiovascular reactivity to mental stress. If reduced water intake has the opposite effect, this would suggest controlling for water deprivation when studying such responses. Blood pressure, heart rate and parasympathetically dominated beat-to-beat heart rate fluctuations were assessed during resting baseline and mental stress. Two challenging cognitive-m...

The human heartbeat series is more variable and, hence, more complex in healthy subjects than in congestive heart failure (CHF) patients. However, little is known about the complexity of the heart rate variations on a beat-to-beat basis. We present an analysis based on symbolic dynamics that focuses on the dynamic features of such beat-to-beat variations on a small time scale. The sequence of a...

Cardioventilatory coupling is an entrainment phenomena, distinct from respiratory sinus arrhythmia, whereby heart and breathing rhythms show temporal coherence. Coupling is commonly observed during rest, sleep and anaesthesia. Five graphical methods, each with different underlying mechanistic assumptions, have been suggested for studying this entrainment relationship: (a) time relationship betw...