In the modern conception of the physiology of the heart beat, two contributions have played perhaps the most import!ant part. The first of these is the proof that the activity of the heart may be analyzed into a number of different physiological properties or functions. The more important of these are automaticity, conductivity and contractility; properties too well recognized today to require ...

Heart rate variability (HRV) is commonly used to assess autonomic functions and responses to environmental stimuli. It is usually derived from electrocardiographic signals; however, in the last few years, photoplethysmography has been successfully used to evaluate beat-to-beat time intervals and to assess changes in the human heart rate under several conditions. The present work describes a sim...

INTRODUCTION Heart rate turbulence is a powerful de novo risk predictor for patients surviving acute myocardial infarction. However, little is known about its underlying physiologic mechanism. METHODS AND RESULTS Hypothesizing that heart rate turbulence is barorceptor reflex related, we studied heart rate and blood pressure fluctuations at rest and after systematically introduced ventricular ...

The present study was designed to determine gestational age in Kari ewes measuring of non-conventional foetal growth parameters i.e., Abdominal Circumference (AC), Foetal Heart Beat Rate (FHBR) and Femur Length (FL).The experiment conducted at different gestational age in Kari sheep with a B-mode ultrasonograph and a 3.5 MHz transducer. The ewes were scanned in dorsal recumbency over a restrain...

The aim of this study was to determine the contribution of NO to arterial pressure and heart rate variability in normotensive rats subjected to high sodium intake. Arterial pressure, heart rate, and arterial pressure and heart rate variability, baroreflex sensitivity, and pressure responsiveness were measured in male Wistar rats treated for 6 weeks (control and high sodium [1%] intake groups), ...

BACKGROUND The goal of the present study was to determine the predictive value of beat-to-beat QT variability in heart failure patients across the continuum of left ventricular dysfunction. METHODS AND RESULTS Beat-to-beat QT variability index (QTVI), log-transformed heart rate variance, normalized QT variance, and coherence between heart rate variability and QT variability have been measured...

BACKGROUND AND PURPOSE The present study was undertaken to investigate an effect of dofetilide, a potent arrhythmic blocker of the voltage-gated K(+) channel, hERG, on cardiac autonomic control. Combined with effects on ardiomyocytes, these properties could influence its arrhythmic potency. EXPERIMENTAL APPROACH The short-term variability of beat-to-beat QT interval (STVQT ), induced by dofet...

The asymmetry in heart rate variability is a visibly obvious phenomenon in the Poincaré plot of normal sinus rhythm. It shows the unevenness in the distribution of points above and below the line of identity, which indicates instantaneous changes in the beat to beat heart rate. The major limitation of the existing asymmetry definition is that it considers only the instantaneous changes in the b...