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Cardiac cycle

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


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Journal ArticleDOI
01 Mar 1970-Thorax
TL;DR: It is imperative to measure both right and left atrial pressures if post-operative management after cardiac valve surgery is to be effective and there has been no instance of pulmonary oedema or postperfusion syndrome in practice since its introduction.
Abstract: Left and right atrial pressures were monitored in 100 patients undergoing open heart surgery for acquired valvular disease of the heart at St. Thomas' Hospital. The right atrial pressure bore no constant relationship to the left atrial pressure in 61% of the patients and there was no reliable way of deducing left atrial pressure from the right. We believe that it is imperative to measure both right and left atrial pressures if post-operative management after cardiac valve surgery is to be effective. There has been no instance of pulmonary oedema or postperfusion syndrome in our practice since its introduction.

28 citations

Journal ArticleDOI
TL;DR: The pressure-volume model is an educational tool that can be used to demonstrate isolated changes in preload, afterload, inotropy, and lusitropy and their interaction.
Abstract: Left ventricular diastolic function plays an important role in cardiac physiology. Lusitropy, the ability of the cardiac myocytes to relax, is affected by both biochemical events within the myocyte and biomechanical events in the left ventricle. β-Adrenergic stimulation alters diastole by enhancing the phosphorylation of phospholamban, a substrate within the myocyte that increases the uptake of calcium ions into the sarcoplasmic reticulum, increasing the rate of relaxation. Troponin I, a regulatory protein involved in the coupling of excitation to contraction, is vital to maintaining the diastolic state; depletion of troponin I can produce diastolic dysfunction. Other biochemical events, such as defects in the voltage-sensitive release mechanism or in inositol triphosphate calcium release channels, have also been implicated in altering diastolic tone. Extracellular collagen determines myocardial stiffness; impaired glucose tolerance can induce an increase in collagen cross-linking and lead to higher end-diastolic pressures. The passive properties of the left ventricle are most accurately measured during the diastasis and atrial contraction phases of diastole. These phases of the cardiac cycle are the least affected by volume status, afterload, inherent viscoelasticity, and the inotropic state of the myocardium. Diastolic abnormalities can be conceptualized by using pressure-volume loops that illustrate myocardial work and both diastolic and systolic pressure-volume relationships. The pressure-volume model is an educational tool that can be used to demonstrate isolated changes in preload, afterload, inotropy, and lusitropy and their interaction. (American Journal of Critical Care. 2004;13:394-405)

28 citations

Journal ArticleDOI
TL;DR: Experiments using a prone biopsy table show the almost complete elimination of tissue motion due to cardiac systole, suggesting that the use of the table eliminates this motion, thus allowing for high-resolution blood velocity estimates.
Abstract: A high-resolution study of breast tissue motion during cardiac systole and respiration is presented. An experimental system was designed to achieve a velocity resolution on the order of 1 mm/s with high spatial resolution. The peak velocity of tissue motion estimated during cardiac systole ranged from 0.2 mm/s to 5.6 mm/s among the subjects studied. It is shown that motion due to the cardiac cycle is less significant when the subject is positioned on the side rather than supine. The mean tissue velocity among subjects in the supine position is 2.88 mm/s and drops to 0.81 mm/s for the side position, with a corresponding spatial displacement of 0.095 mm, dropping to 0.027 mm. The velocity profiles indicate that 100 ms is required for the entire ribcage contraction-relaxation process to occur. Experiments using a prone biopsy table show the almost complete elimination of tissue motion due to cardiac systole, suggesting that the use of the table eliminates this motion, thus allowing for high-resolution blood velocity estimates. Features resulting from respiratory motion are also presented. We found this motion to be of a much longer time duration, and of a much higher magnitude, with velocities as high as 29 mm/s. The implications of the study on the high-resolution estimation of blood velocity and high-resolution breast imaging are discussed.

28 citations

Journal ArticleDOI
TL;DR: This study was undertaken to assess the suitability for intraoperative pulmonary vein flow measurements in 15 patients undergoing coronary artery bypass grafting using two‐dimensional color Doppler transesophageal echocardiography.
Abstract: This study was undertaken to assess the suitability for intraoperative pulmonary vein flow measurements in 15 patients undergoing coronary artery bypass grafting. Using two-dimensional color Doppler transesophageal echocardiography, all four pulmonary veins--right upper and lower and left upper and lower pulmonary veins were easily visualized. Pulmonary vein flow was pulsatile. J wave occurred in the ventricular systole with relaxation of the left atrium and K wave in the ventricular diastole with relaxation of the left ventricle. There were differences in suitability for flow measurements among four pulmonary veins: (1) consistent visualization; (2) stable visualization throughout measurement; (3) minimal angle between ultrasonic beam and pulmonary vein course; and (4) minimal shift of sampling volume during measurement. The left pulmonary veins were suitable for flow velocity measurement by transesophageal echocardiography. The left lower pulmonary vein was stable for visualization once it was visualized although the angle was occasionally large. The left upper pulmonary vein was consistently visualized although the angle was occasionally large. On the other hand, the right pulmonary veins were unsuitable for flow measurement. Since sampling volume shifted in the direction of the long axis by the average of 5 to 6 mm during cardiac cycle, it should be positioned inside of the pulmonary vein at about 5 mm from the orifice of the left atrium.

28 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202377
2022178
202169
202068
201979
201876