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Venous flow is pulsatile
Published in Dinker B. Rai, Mechanical Function of the Atrial Diastole, 2022
This author has convincingly proved that both systole and diastole are equally active phases of the cardiac cycle and contribute equally to the function of the heart. This is because during both phases there are chemical, physical, and electrical changes taking place at the cellular level. This author has experimentally proved both contraction and dilatation of cardiac muscle as active phenomena and both are not the resting phase of the cardiac cycle. At the present time we can say if at all the heart rests, then it is for a moment during the intervals between the systole and diastole. This resting is in the sense that consumption of energy is lowest by the heart in that intermediate phase.
A Review of Automatic Cardiac Segmentation using Deep Learning and Deformable Models
Published in Kayvan Najarian, Delaram Kahrobaei, Enrique Domínguez, Reza Soroushmehr, Artificial Intelligence in Healthcare and Medicine, 2022
Behnam Rahmatikaregar, Shahram Shirani, Zahra Keshavarz-Motamed
The cardiac cycle is defined as a sequence of alternating contractions and relaxations of the atria and ventricles in order to pump blood throughout the body. This cycle starts at the beginning of one heartbeat and ends at the start of the next. Each cardiac cycle has a diastolic phase (also called diastole) and a systolic phase (also called systole). Diastole occurs when the heart muscles relax, and the chambers are able to fill with blood. Systole occurs when the ventricles contract, pushing blood out of the right and left ventricles into the lungs and the rest of the body, respectively. Since manual delineation of ventricle contours in all cardiac phases is not possible, physicians focus only on end-diastole and end-systole phases for assessment of the cardiovascular system.
Mechanical Events of the Cardiac Cycle
Published in Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal, Principles of Physiology for the Anaesthetist, 2020
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal
The cardiac cycle comprises two phases defined by ventricular muscle mechanical activity: systole (contraction) and diastole (relaxation). During systole, ventricles contract, AV valves close (first heart sound) and intraventricular pressure rises until aortic and pulmonary valves open (isovolumetric ventricular contraction); ventricular ejection of blood then takes place (stroke volume). During diastole, the ventricles relax, aortic and pulmonary valves close (second heart sound), intraventricular pressure falls until the AV valves open (isovolumetric ventricular relaxation) and ventricles then fill with blood again. Atrial contraction completes ventricular filling before the onset of the next ventricular systole.
Neighbourhood deprivation in childhood and adulthood and risk of arterial stiffness: the Cardiovascular Risk in Young Finns study
Published in Blood Pressure, 2023
Erika Kähönen, Satu Korpimäki, Markus Juonala, Mika Kähönen, Terho Lehtimäki, Nina Hutri-Kähönen, Olli T. Raitakari, Mika Kivimäki, Jussi Vahtera
Measurements of arterial PWV were performed in 2007 with a whole-body impedance cardiography device (CircMonR, JR Medical Ltd, Tallinn, Estonia). The method includes whole-body impedance cardiography, distal impedance plethysmography, and an ECG channel. Standard electrodes were placed on the body surface: for the whole-body impedance measurement a pair of current electrodes on the wrist and ankles, and a pair of voltage electrodes 5 cm proximal to the aforementioned current electrodes, and for the distal impedance plethysmography measurement the active electrode on the lateral side of the knee joint and reference electrode about 20 cm distal to it on the calf. The method registers continuous changes in body electrical impedance during a cardiac cycle. The whole-body impedance decreases when the pulse pressure wave enters the aortic arch and popliteal artery impedance decreases when the pulse pressure wave later enters the lower limb. The aortic-popliteal PWV can be calculated by the CircMonR device software from the pulse transit time and the approximate distance between the aortic arch and the popliteal artery. The measurement method and its validation procedure have been introduced in detail earlier (Aatola et al. 2010; Kööbi et al. 2003). This method has been detected to have good repeatability and reproducibility values and measurements have excellent correlation (r = 0.82) with tonometric PWV method measurements (Tahvanainen et al. 2009; Wilenius et al. 2016).
Complications associated with myocardial bridging in four children without underlying cardiac disease: a case series
Published in Paediatrics and International Child Health, 2021
Federica Brancato, Donato Rigante, Marco Piastra, Alessandro Gambacorta, Claudia Aurilia, Gabriella De Rosa
One of the most important triggers of symptomatic MB is intense physical activity which through tachycardia and increased contractility can facilitate myocardial ischaemia. During tachycardia, systole occupies a greater proportion of the cardiac cycle because of shortening of the diastolic filling period. Other pathophysiological factors that might reveal or exacerbate MB are age, left ventricular hypertrophy and coronary atherosclerosis, since all of these may worsen the supply-demand mismatch imposed by the bridge, reducing the coronary reserve [15]. Symptomatic patients may also present with clinical manifestations of myocardial ischaemia such as acute coronary syndrome, coronary spasm, exercise-induced dysrhythmias, myocardial stunning, transient ventricular dysfunction and syncope [15]. Only patients with symptomatic MB or those with objective signs of ischaemia require treatment. In most cases, beta-blockers, ivabradine and calcium channel blockers are effective in reducing symptoms [15]. In adults, myotomy, coronary artery by-pass surgery and stenting may be used to improve symptoms in patients with MB who are refractory to medical therapy [2,20,22,23]. MB is diagnosed by coronary or CT angiography, but it is sometimes established intra-operatively or at post-mortem examination. Another relevant diagnostic test is the stress ECG: the main objective of stress testing for myocardial ischaemia is to demonstrate the mismatch between myocardial oxygen demand and myocardial perfusion [22].
The evolution of long-term pediatric ventricular assistance devices: a critical review
Published in Expert Review of Medical Devices, 2021
Louis Marcel, Mathieu Specklin, Smaine Kouidri
At first, designers’ objective was to replicate the native cardiac cycle using a diaphragm or pusher plate delivering pulsatile flow through unidirectional and artificial heart valves. Figure 6 shows the mechanical structure of these devices. Thanks to a flexible diaphragm whose vertical displacement is imposed by the pusher plate, the blood is compressed in the pumping chamber until the pressure is superior to the one in the outflow. At this moment, the outflow valve opens and the blood is re-injected in the aorta. Pressure decreases as the pusher plate comes back down. Pressure value becomes inferior than the inflow resulting in the opening of the inflow valve and the pumping chambers is filled back with blood. The devices was filled during diastole and communicate the energy to the fluid by ejecting it during systole, this is a device working in co-pulsation [56]. These pumps were reported by Frazier et al. as similar in operation as the human heart thanks to the pulsatile outflow generated [57]. This pump generation was also characterized by their large dimensions and heavy external driving units, limiting the patient’s mobility. Unfortunately, the technology was not very reliable on the long term as most of them presented global pump dysfunction leading to right heart failure, renal dysfunction and neurologic adverse events after a year of support according to clinicians. These drawbacks and the lack of reliability in the technology led to the development of devices based on a rotating impeller [58].