Cardiac cycle

About: Cardiac cycle is a research topic. Over the lifetime, 3290 publications have been published within this topic receiving 96159 citations.

A Review Paper on Analysis ofElectrocardiograph (ECG) Signal for theDetection of Arrhythmia Abnormalities

Abstract: ECG conveys information regarding the electrical function of the heart, by altering the shape of its constituent waves, namely the P, QRS, and T waves. ECG Feature Extraction plays a significant role in diagnosing most of the cardiac diseases. One cardiac cycle in an ECG signal consists of the P-QRS-T waves. This feature extraction scheme determines the amplitudes and interval in the ECG signal for subsequent analysis. The amplitude and interval of P-QRS-T segment determine the function of heart. Cardiac Arrhythmia shows a condition of abnormal electrical activity in the heart which is a threat to humans. The aim of this paper presents analyses cardiac disease in Electrocardiogram (ECG) Signals for Cardiac Arrhythmia using analysis of resulting ECG normal & abnormal wave forms. This paper presents a method to analyze electrocardiogram (ECG) signal, extract the features, for the classification of heart beats according to different arrhythmia. Cardiac arrhythmia which are found are Tachycardia, Bradycardia, Supra ventricular Tachycardia, Incomplete Bundle Branch Block, Bundle Branch Block, Ventricular Tachycardia, hence abnormalities of heart may cause sudden cardiac arrest or cause damage of heart. The early detection of arrhythmia is very important for the cardiac patients. Electrocardiogram (ECG) feature extraction system has been developed and evaluated based on the multi-resolution wavelet transform.

Blood pressures and heart rate during larval development in the anuran amphibian Xenopus laevis

Abstract: Heart rate and blood pressure were measured in lightly anesthetized developing Xenopus laevis from hatching (body mass approximately 3 mg) to the end of metamorphosis (< or = 1 g). Blood pressures in the conus arteriosus, truncus arteriosus, and ventricle were measured by a servo-null micropressure system. Heart rate was determined from blood pressure recordings, and cardiac cycles were videotaped through a dissecting microscope. Heart rate varied from 50 to 150 beats/min and showed a negative correlation with body mass, with a slope less than predicted from allometric equations based on adult vertebrates. Mean truncus pressures showed a positive correlation with body mass, increasing from 4 mmHg in a 25-mg larva to 9 mmHg in a 1-g larva. The pressure waveform during ventricular systole was similar in all developmental stages examined, whereas those in conus and truncus varied with development. Conus pressures differed distinctly from truncus pressure during diastole in all larvae examined, suggesting the existence of functional valves between conus and truncus as early as stage 46 of the Nieuwkoop-Faber larval staging system. Although the developmental patterns of heart rate and blood pressure in X. laevis showed significant correlation with body mass, body mass explained less than one-half of the variation in these variables. Therefore developmental factors other than body mass, such as changes in heart mass and the addition of new resistance vessels, may influence heart rate and blood pressure during development in X. laevis.

Accurate quantitation of regurgitant volume with MRI in patients selected for mitral valve repair

Abstract: Objective: Echocardiography, the currently preferred diagnostic approach for mitral valve regurgitation, cannot accurately quantify the amount of regurgitation. Flow quantification with MRI is possible, but the conventional method (1-directional velocity-encoding) acquires the flow at a fixed location during the cardiac cycle, which is not necessarily the location of the mitral valve during the whole cycle. In this study, the exact flow through the mitral valve was quantified with a 3-directional velocity-encoded MRI approach. Methods: Ten patients with severe mitral valve regurgitation (class 3‐4Cwith echocardiography) resulting from systolic restrictive motion of both leaflets (Carpentier IIIb) which were selected for valve repair and 10 healthy volunteers without cardiac valvular disease confirmed with echocardiography were included in this study. The intraventricular flow was sampled with a radial stack of six acquisition planes parallel to the long-axis of the left ventricle. Three-directional velocityencoded MRI was performed resulting in the intra-ventricular flow velocity vector field for 30 phases during the cardiac cycle. The position of the mitral valvular plane in this vector field was indicated manually for each phase. Velocity values perpendicular to this plane determined the flow through the mitral valve. Both the 3-directional encoded mitral valve flow and the 1-directional encoded mitral valve flow were compared with the flow determined with MRI at the ascending aorta. Results: One-directional velocity-encoded MRI showed a mean overestimation (P!0.01) of 25 ml/cycle compared to the aortic flow. Correlation was very poor (rPZ0.15, PZ0.68). The 3-directional velocity-encoded MRI on the other hand, showed no over/underestimation and a good correlation (rPZ0.91, P!0.01 for volunteers, rPZ0.90, P!0.01 for patients). The regurgitant flow fractions were between 3 and 30%. Conclusion: With 3-directional velocity-encoded MRI, measurement of the flow through the mitral valve is accurate and reproducible. This is a valuable tool for diagnosing and absolute quantification of regurgitant volume. q 2004 Elsevier B.V. All rights reserved.

Dynamic three-dimensional color Doppler ultrasound of human fetal intracardiac flow.

Abstract: Objectives To develop dynamic three-dimensional ultrasound techniques for prenatal imaging of the intracardiovascular flow as well as the cardiovascular structure to address difficulties in assessing the spatially complex hemodynamics and morphology of the fetal heart. Methods Gray-scale and color (velocity) Doppler echocardiography were performed on 12 fetuses to provide serial anatomical and rheological tomograms which were spatially registered in three dimensions. Using a second ultrasound machine simultaneously, spectral Doppler ultrasound was performed to record umbilical arterial waveforms, thus providing the temporal (fourth) dimension in terms of the cardiac cycle and facilitating removal of motion artifacts. Results Acquisitions were successful in eight of 15 attempts. Imaging of the flow of blood in four dimensions was achieved in six of the eight datasets. In one case with complex cardiac malformations, three-dimensional reconstructions at systole and diastole offered dynamic diagnostic views not appreciated on the cross-sectional images. Conclusions Our novel technique has made possible the prenatal visualization of the spatial distribution and true direction of intracardiac flow of blood in four dimensions in the absence of motion artifacts. The technique suggests that diagnosis of cardiac malformations can be made on the basis of morphological and hemodynamic changes throughout the entire cardiac cycle, offering unique and significant information complementary to conventional techniques. Further work to integrate the several non-purpose-built machines into a single system will improve the rate of acquisition of data, and may provide a new means of imaging and modeling structure and hemodynamics, not only for the fetal heart but for many other moving body parts.

Magnetic resonance imaging analysis of cardiac cycle events in diabetic rats: the effect of angiotensin‐converting enzyme inhibition

Abstract: Non-invasive magnetic resonance imaging (MRI) was used to characterize changes in left and right ventricular cardiac cycles following induction of experimental, streptozotocin (STZ)-induced, diabetes in male Wistar rats at different ages. The effects of the angiotensin-converting enzyme (ACE) inhibitor captopril upon such chronic physiological changes were then evaluated, also for the first time. Diabetes was induced at the age of 7 weeks in two experimental groups, of which one group was subsequently maintained on captopril (2 g l−1)-containing drinking water, and at 10 and 13 weeks in two further groups. The fifth group provided age-matched controls. All groups (each n = 4 animals) were scanned consistently at 16 weeks, in parallel with timings used in earlier studies that employed this experimental model. Cine magnetic resonance (MR) image acquisition provided transverse sections through both ventricles at twelve time points covering systole and most of diastole. These yielded reconstructions of cardiac anatomy used to derive critical functional indices and their dependence upon time following the triggering electrocardiographic R waves. The left and right ventricular end-diastolic (EDV), end-systolic (ESV) and stroke volumes (SV), and ejection fractions (EF) calculated from each, control and experimental, group showed matching values. This confirmed a necessary condition requiring balanced right and left ventricular outputs and further suggested that STZ-induced diabetes produced physiological changes in both ventricles. Absolute left and right ventricular SVs were significantly altered in all diabetic animals; EDVs and EFs significantly altered in animals diabetic from 7 and 10 but not 13 weeks. When normalized to body weight, left and right ventricular SVs had significantly altered in animals diabetic from 7 and 10 weeks but not 13 weeks. Normalized left ventricular EDVs were also significantly altered in animals diabetic from 7 and 10 weeks. However, normalized right ventricular EDVs were significantly altered only in animals made diabetic from 7 weeks. Diabetic hearts showed major kinetic changes in left and right ventricular contraction (ejection) and relaxation (filling). Both the initial rates of volume change (dV/dt) in both ventricles and the plots of dV/dt values through the cardiac cycle demonstrated more gradual developments of tension during systole and relaxation during diastole. Estimates of the derived left ventricular performance parameters of cardiac output, cardiac power output and stroke work in control animals were comparable with human values when normalized to both body (or cardiac) weight and heart rate. All deteriorated with diabetes. Comparisons of experimental groups diabetic from 7 weeks demonstrated that captopril treatment relieved the alterations in critical volumes, dependence of SV upon EDV, kinetics of systolic contraction and diastolic relaxation and in the derived indicators of ventricular performance. This study represents the first demonstration using non-invasive MRI of early, chronic changes in diastolic filling and systolic ejection in both the left and the right ventricles and of their amelioration by ACE inhibition following STZ-induction of diabetes in intact experimental animals.