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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
TL;DR: This study evaluates a simple noninvasive method using accelerometers attached to the skin to measure cardiac time intervals in biventricularly paced patients.
Abstract: Introduction: Changes due to biventricular pacing have been documented by shortening of QRS duration and echocardiography. Compared to normal ventricular activation, the presence of left bundle branch block (LBBB) results in a significant change in cardiac cycle time intervals. Some of these have been used to quantify the underlying cardiac dyssynchrony, assess the effects of biventricular pacing, and guide programming of ventricular pacing devices. This study evaluates a simple noninvasive method using accelerometers attached to the skin to measure cardiac time intervals in biventricularly paced patients. Methods: Ten patients with biventricular pacemakers previously implanted for congestive heart failure were paced in the AAI mode, then in atrioventricular (AV) sequential mode from the right and left ventricles followed by biventricular pacing. Simultaneous recordings were obtained by 2D, Doppler echocardiography as well as by accelerometers. Similar recordings were obtained from 10 gender, aged matched, normal controls during sinus rhythm. Results: Compared to normals, heart failure patients paced in AAI mode had prolonged isovolumetric contraction time (IVCT), shorter ventricular ejection time (LVET), and prolonged isovolumetric relaxation (IVRT). With biventricular pacing the IVCT decreased, but the LVET and IVRT did not change significantly. There was excellent correlation between the echo and accelerometer-measured intervals. Conclusions: Shortening of the IVCT measured by an accelerometer is a consistent time interval change due to biventricular pacing that probably reflects more rapid acceleration of left ventricular ejection. The accelerometer may be useful to assess immediate efficacy of biventricular pacing during device implantation and optimize programmable time intervals such as AV and interventricular (VV) delays. (PACE 2007; 30:1476‐1481)

36 citations

Patent
18 Mar 2005
TL;DR: A noninvasive or minimally invasive treatment of infarct areas of the heart with High Intensity Focused Ultrasound (HIFU) emitted without respect to the timing or phase of the cardiac cycle, intended to remodel cardiac tissue by inducing angiogenesis and/or the formation of myocytes to improve cardiac function as mentioned in this paper.
Abstract: A noninvasive or minimally invasive treatment of infarct areas of the heart with High Intensity Focused Ultrasound (HIFU) emitted without respect to the timing or phase of the cardiac cycle, intended to remodel cardiac tissue by inducing angiogenesis and/or the formation of myocytes to improve cardiac function.

36 citations

Journal ArticleDOI
TL;DR: It is shown that an isolated change in left atrial compliance alters predictably reservoir function and the pattern of pulmonary venous flow, which helps to provide motivation for a more complete evaluation of the atrial cycle.
Abstract: The principal function of the left atrium is to modulate left ventricular (LV) filling and cardiovascular performance through reservoir, conduit, and booster pump functions; the latter is often (mistakenly) regarded synonymously with atrial function, and in contrast to the reservoir and conduit phases, has been studied extensively. Typically, the importance of atrial contraction has been estimated by measurements of cardiac output and end-diastolic volumes both with and without effective atrial systole, by relative LV filling using Doppler transmitral velocimetry (E/A ratios) or radionuclide angiography, or by atrial shortening using 2D echocardiography, angiography, and sonomicrometry. Despite considerable investigation, the magnitude and relative importance of the atrial contribution to LV filling and cardiac output remain controversial and provide motivation for a more complete evaluation of the atrial cycle. In this regard, nearly half of the LV stroke volume and its associated energy is stored in the left atrium during ventricular systole, which acts as a ventricular restoring force during the ensuing ventricular diastole.1 This reservoir function of the left atrium is governed by atrial compliance, which is most rigorously measured by mathematically fitting atrial pressure and volume data during ventricular systole. A number of studies have shown, however, that the proportion of left atrial inflow during ventricular systole with Doppler pulmonary venous flow (ie, S/D ratios) can estimate relative reservoir function. Thus, we showed that an isolated change in left atrial compliance alters predictably reservoir function and the pattern of pulmonary venous flow.2 Decreased atrial compliance is associated with greater phasic atrial pressures but a lower mean level of atrial pressure during ventricular filling, and as a result, a smaller end-diastolic volume and decreased venous return.3 In contrast, increased atrial compliance increases early LV filling and atrial systolic shortening.4 See p 387 Pressure-strain analysis in the intact dog …

36 citations

Journal ArticleDOI
TL;DR: An updated version of this previous closed-loop CVS model that includes the progressive opening of the mitral valve is described, and is defined over the full cardiac cycle, providing a foundation for clinical validation and the study of valvular dysfunction in vivo.
Abstract: Background: Valve dysfunction is a common cardiovascular pathology. Despite significant clinical research, there is little formal study of how valve dysfunction affects overall circulatory dynamics. Validated models would offer the ability to better understand these dynamics and thus optimize diagnosis, as well as surgical and other interventions. Methods: A cardiovascular and circulatory system (CVS) model has already been validated in silico, and in several animal model studies. It accounts for valve dynamics using Heaviside functions to simulate a physiologically accurate “open on pressure, close on flow” law. However, it does not consider real-time valve opening dynamics and therefore does not fully capture valve dysfunction, particularly where the dysfunction involves partial closure. This research describes an updated version of this previous closed-loop CVS model that includes the progressive opening of the mitral valve, and is defined over the full cardiac cycle. Results: Simulations of the cardiovascular system with healthy mitral valve are performed, and, the global hemodynamic behaviour is studied compared with previously validated results. The error between resulting pressure-volume (PV) loops of already validated CVS model and the new CVS model that includes the progressive opening of the mitral valve is assessed and remains within typical measurement error and variability. Simulations of ischemic mitral insufficiency are also performed. Pressure-Volume loops, transmitral flow evolution and mitral valve aperture area evolution follow reported measurements in shape, amplitude and trends. Conclusions: The resulting cardiovascular system model including mitral valve dynamics provides a foundation for clinical validation and the study of valvular dysfunction in vivo. The overall models and results could readily be generalised to other cardiac valves.

36 citations

Posted Content
TL;DR: Three-dimensional data gives the experimental evidence of the reorganization of the flow in a single vortex persisting until the end of the diastole, which seems to optimize the cardiac function since it directs velocity towards the aortic valve just before the systole and minimizes the fraction of blood residing within the ventricle for more cycles.
Abstract: The laboratory models of the human heart left ventricle developed in the last decades gave a valuable contribution to the comprehension of the role of the fluid dynamics in the cardiac function and to support the interpretation of the data obtained in vivo. Nevertheless, some questions are still open and new ones stem from the continuous improvements in the diagnostic imaging techniques. Many of these unresolved issues are related to the three-dimensional structure of the left-ventricular flow during the cardiac cycle. In this paper we investigated in detail this aspect using a laboratory model. The ventricle was simulated by a flexible sack varying its volume in time according to a physiologically shaped law. Velocities measured during several cycles on series of parallel planes, taken from two orthogonal points of view, were combined together in order to reconstruct the phase averaged, three-dimensional velocity field. During the diastole, three main steps are recognized in the evolution of the vortical structures: i) straight propagation in the direction of the long axis of a vortex-ring originated from the mitral orifice; ii) asymmetric development of the vortex-ring on an inclined plane; iii) single vortex formation. The analysis of three-dimensional data gives the experimental evidence of the reorganization of the flow in a single vortex persisting until the end of the diastole. This flow pattern seems to optimize the cardiac function since it directs velocity towards the aortic valve just before the systole and minimizes the fraction of blood residing within the ventricle for more cycles.

36 citations


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