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Showing papers on "Cardiac cycle published in 2011"


Journal ArticleDOI
01 Dec 2011-Heart
TL;DR: The pathophysiology ofleft atrial mechanical function is described and both conventional and new echocardiographic parameters used to evaluate left atrial function are discussed, which have a central role in maintaining optimal cardiac output despite impaired LV relaxation and reduced LV compliance.
Abstract: This article describes the pathophysiology of left atrial mechanical function and discusses both conventional and new echocardiographic parameters used to evaluate left atrial function. The evidence regarding the clinical usefulness of left atrial function assessment is also presented. Atrial function, in a close interdependence with left ventricular (LV) function, plays a key role in maintaining an optimal cardiac performance. The left atrium (LA) modulates LV filling through its reservoir, conduit, and booster pump function, whereas LV function influences LA function throughout the cardiac cycle. The LA can act to increase LA pressure (in significant atrial disease) and can react to increased LV filling pressure (in significant ventricular disease). LA remodelling is related to LV remodellingw1 and LA function has a central role in maintaining optimal cardiac output despite impaired LV relaxation and reduced LV compliance.1 Understanding how each component of LA function is influenced by LV performance, and how each LA phasic function contributes to maintain an optimal stroke volume in normal and diseased hearts, is important for interpreting data derived from quantification of LA function. During LV systole and isovolumic relaxation, the LA functions as a reservoir, receiving blood from the pulmonary veins and storing energy in the form of pressure. This atrial function is modulated by LV contraction, through the descent of the LV base during systole, by right ventricular systolic pressure transmitted through the pulmonary circulation, and by LA properties (ie, relaxation and chamber stiffness).w2 During early …

200 citations


Journal ArticleDOI
TL;DR: This paper presents a methodology to construct finite element electromechanical models of ventricular contraction with anatomically accurate ventricular geometry based on magnetic resonance and diffusion tensor magnetic resonance imaging of the heart.
Abstract: Current multi-scale computational models of ventricular electromechanics describe the full process of cardiac contraction on both the micro- and macro- scales including: the depolarization of cardiac cells, the release of calcium from intracellular stores, tension generation by cardiac myofilaments, and mechanical contraction of the whole heart. Such models are used to reveal basic mechanisms of cardiac contraction as well as the mechanisms of cardiac dysfunction in disease conditions. In this paper, we present a methodology to construct finite element electromechanical models of ventricular contraction with anatomically accurate ventricular geometry based on magnetic resonance and diffusion tensor magnetic resonance imaging of the heart. The electromechanical model couples detailed representations of the cardiac cell membrane, cardiac myofilament dynamics, electrical impulse propagation, ventricular contraction, and circulation to simulate the electrical and mechanical activity of the ventricles. The utility of the model is demonstrated in an example simulation of contraction during sinus rhythm using a model of the normal canine ventricles.

154 citations


Journal ArticleDOI
TL;DR: A cardiac cycle consists of systolic (contraction) and diastolic (relaxation and filling) phases that are linked closely together for optimal function of the heart.
Abstract: A cardiac cycle consists of systolic (contraction) and diastolic (relaxation and filling) phases that are linked closely together for optimal function of the heart. Normal diastolic function allows adequate filling of the heart without an excessive increase in diastolic filling pressure both in the resting state and with stress or exertion.1 The diastolic phase is remarkably well designed to ensure that the ventricle is optimally filled for a given clinical condition.2 Basically, at the end of systole, left ventricular (LV) relaxation begins as an initial diastolic process, and LV pressure falls rapidly as the LV expands. This relaxation phase is accompanied by active movement of the mitral annulus away from the apex. The velocity of LV dilatation and mitral annular movement during early diastole correlates well with how fast the LV fills and relaxes, respectively.3,4 Myocardial relaxation continues during early diastole to reach the minimal LV diastolic pressure, which helps with “sucking” or “pulling” the blood actively into the LV (Figure 1, online-only Data Supplement Video 1A). The minimal LV diastolic pressure or completion of relaxation normally occurs by 3.5 times the value of tau—the time constant of relaxation (normal <45 ms)—after the mitral opening.5 LV pressure then rises to be equilibrated with left atrial (LA) pressure, at which time the early diastolic filling decelerates to close the mitral valve until the time of atrial contraction when LA pressure increases to initiate the late filling to complete diastole (Figure 1, online-only Data Supplement Video 1B). Figure 1. Top, Schematic diagram of mitral inflow and mitral medial annulus velocities from normal to progressive stages of diastolic dysfunction. Mitral inflow E is sensitive to preload, becoming higher with shorter deceleration time (time from the peak to the baseline) as diastolic function becomes worse with increasing filling …

141 citations


Journal ArticleDOI
TL;DR: The authors' method seems suitable for implementing detailed patient-specific MV FEMs to simulate different scenarios of clinical interest, and to reduce its computational time and to expand the range of modeled surgical procedures.
Abstract: We aim at testing the possibility to build patient-specific structural finite element models (FEMs) of the mitral valve (MV) from cardiac magnetic resonance (CMR) imaging and to use them to predict the outcome of mitral annuloplasty procedures. MV FEMs were built for one healthy subject and for one patient with ischemic mitral regurgitation. On both subjects, CMR imaging of 18 long-axis planes was performed with a temporal resolution of 55 time-frames per cardiac cycle. Three-dimensional MV annulus geometry, leaflets surface and PM position were manually obtained using custom software. Hyperelastic anisotropic mechanical properties were assigned to MV tissues. A physiological pressure load was applied to the leaflets to simulate valve closure until peak systole. For the pathological model only, a further simulation was run, simulating undersized rigid annuloplasty before valve closure. Closure dynamics, leaflets stresses and tensions in the subvalvular apparatus in the healthy MV were consistent with previous computational and experimental data. The regurgitant valve model captured with good approximation the real size and position of regurgitant areas at peak systole, and highlighted abnormal tensions in the annular region and sub-valvular apparatus. The simulation of undersized rigid annuloplasty showed the restoration of MV continence and normal tensions in the subvalvular apparatus and at the annulus. Our method seems suitable for implementing detailed patient-specific MV FEMs to simulate different scenarios of clinical interest. Further work is mandatory to test the method more deeply, to reduce its computational time and to expand the range of modeled surgical procedures.

98 citations


Journal ArticleDOI
TL;DR: There is a complex and heterogeneous pattern of expression of ion and gap junction channels and Ca(2+)-handling proteins in the human atrioventricular conduction axis that explains the function of this crucial pathway.

95 citations


Journal ArticleDOI
TL;DR: This study demonstrated a significant individual dynamic change in the dimensions of the aortic root, independent of gender, age, height and weight, which is highly unpredictable.
Abstract: Cardiac pulsatility and aortic compliance may result in aortic area and diameter changes throughout the cardiac cycle in the entire aorta. Until this moment these dynamic changes could never be established in the aortic root (aortic annulus, sinuses of Valsalva and sinotubular junction). The aim of this study was to visualize and characterize the changes in aortic root dimensions during systole and diastole with ECG-gated multidetector row computed tomography (MDCT). MDCT scans of subjects without aortic root disease were analyzed. Retrospectively, ECG-gated reconstructions at each 10% of the cardiac cycle were made and analyzed during systole (30–40%) and diastole (70–75%). Axial planes were reconstructed at three different levels of the aortic root. At each level the maximal and its perpendicular luminal dimension were measured. The mean dimensions of the total study group (n = 108, mean age 56 ± 13 years) do not show any significant difference between systole and diastole. The individual dimensions vary up to 5 mm. However, the differences range between minus 5 mm (diastolic dimension is greater than systolic dimensions) and 5 mm (vice versa). This variability is independent of gender, age, height and weight. This study demonstrated a significant individual dynamic change in the dimensions of the aortic root. These results are highly unpredictable. Most of the healthy subjects have larger systolic dimensions, however, some do have larger diastolic dimensions.

89 citations


Reference EntryDOI
TL;DR: Electrocardiography (ECG) is the "gold standard" using either hard wire or telemetry transmission, and heart rate is measured or monitored from the frequency of the arterial pressure pulse or cardiac contraction, or by pulse oximetry.
Abstract: The majority of current cardiovascular research involves studies in genetically engineered mouse models. The measurement of heart rate is central to understanding cardiovascular control under normal conditions, with altered autonomic tone, superimposed stress or disease states, both in wild type mice as well as those with altered genes. Electrocardiography (ECG) is the "gold standard" using either hard wire or telemetry transmission. In addition, heart rate is measured or monitored from the frequency of the arterial pressure pulse or cardiac contraction, or by pulse oximetry. For each of these techniques, discussions of materials and methods, as well as advantages and limitations are covered. However, only the direct ECG monitoring will determine not only the precise heart rates but also whether the cardiac rhythm is normal or not.

87 citations


Patent
25 Apr 2011
TL;DR: In this article, various techniques for measuring cardiac cycle length and pressure metrics based on pulmonary artery pressures are described, including identifying a point within a derivative signal of a cardiovascular pressure signal without reference to electrical activity of a heart, initiating a time window from the identified point in the derivative signal, and determining at least one of a systolic pressure or diastolic pressure based on the identified points.
Abstract: Various techniques for measuring cardiac cycle length and pressure metrics based on pulmonary artery pressures are described. One example method described includes identifying a point within a derivative signal of a cardiovascular pressure signal without reference to electrical activity of a heart, initiating a time window from the identified point in the derivative signal, identifying a point within the cardiovascular signal within the time window, and determining at least one of a systolic pressure or diastolic pressure based on the identified point.

68 citations


Journal ArticleDOI
TL;DR: The combined dynamic and imaging data show the developing structural capacity to accommodate increasing flow and the mechanotransducing networks that organize to effectively facilitate formation of the trabeculated four-chambered heart.
Abstract: Analyses of form-function relationships during heart looping are directly related to technological advances. Recent advances in four-dimensional optical coherence tomography (OCT) permit observations of cardiac dynamics at high-speed acquisition rates and high resolution. Real-time observation of the avian stage 13 looping heart reveals that interactions between the endocardial and myocardial compartments are more complex than previously depicted. Here we applied four-dimensional OCT to elucidate the relationships of the endocardium, myocardium, and cardiac jelly compartments in a single cardiac cycle during looping. Six cardiac levels along the longitudinal heart tube were each analyzed at 15 time points from diastole to systole. Using image analyses, the organization of mechanotransducing molecules, fibronectin, tenascin C, α-tubulin, and nonmuscle myosin II was correlated with specific cardiac regions defined by OCT data. Optical coherence microscopy helped to visualize details of cardiac architectural development in the embryonic mouse heart. Throughout the cardiac cycle, the endocardium was consistently oriented between the midline of the ventral floor of the foregut and the outer curvature of the myocardial wall, with multiple endocardial folds allowing high-volume capacities during filling. The cardiac area fractional shortening is much higher than previously published. The in vivo profile captured by OCT revealed an interaction of the looping heart with the extra-embryonic splanchnopleural membrane providing outside-in information. In summary, the combined dynamic and imaging data show the developing structural capacity to accommodate increasing flow and the mechanotransducing networks that organize to effectively facilitate formation of the trabeculated four-chambered heart.

62 citations


Book ChapterDOI
18 Sep 2011
TL;DR: A method is presented such that a detailed, patient-specific annulus and leaflets are tracked throughout mitral valve closure, resulting in a detailed coaptation region.
Abstract: Segmenting the mitral valve during closure and throughout a cardiac cycle from four dimensional ultrasound (4DUS) is important for creation and validation of mechanical models and for improved visualization and understanding of mitral valve behavior. Current methods of segmenting the valve from 4DUS either require extensive user interaction and initialization, do not maintain the valve geometry across a cardiac cycle, or are incapable of producing a detailed coaptation line and surface. We present a method of segmenting the mitral valve annulus and leaflets from 4DUS such that a detailed, patient-specific annulus and leaflets are tracked throughout mitral valve closure, resulting in a detailed coaptation region. The method requires only the selection of two frames from a sequence indicating the start and end of valve closure and a single point near a closed valve. The annulus and leaflets are first found through direct segmentation in the appropriate frames and then by tracking the known geometry to the remaining frames. We compared the automatically segmented meshes to expert manual tracings for both a normal and diseased mitral valve, and found an average difference of 0.59 ± 0.49mm, which is on the order of the spatial resolution of the ultrasound volumes (0.5-1.0mm/voxel).

56 citations


Journal ArticleDOI
TL;DR: 4DCT imaging data suggest high variability in RVOT/PA dynamics and significant errors in deformation measurements if 3D analysis is not carried out, which play an important role for the development of novel percutaneous approaches to pulmonary valve intervention.
Abstract: Objective To characterise 3D deformations of the right ventricular outflow tract (RVOT)/ pulmonary arteries (PAs) during the cardiac cycle and estimate the errors of conventional 2D assessments.

Journal ArticleDOI
TL;DR: In conclusion, counterpulse mode of rotary LVADs can enhance myocardial perfusion and this novel drive mode can provide great benefits to the patients with end-stage heart failure, especially those with ischemic etiology.
Abstract: The effect of rotary left ventricular assist devices (LVADs) on myocardial perfusion has yet to be clearly elucidated, and several studies have shown decreased coronary flow under rotary LVAD support. We have developed a novel pump controller that can change its rotational speed (RS) in synchronization with the native cardiac cycle. The aim of our study was to evaluate the effect of counterpulse mode, which increases the RS in diastole, during coronary perfusion. Experiments were performed on ten adult goats. The EVAHEART LVAD was installed by the left ventricular uptake and the descending aortic return. Ascending aortic flow, pump flow, and coronary flow of the left main trunk were monitored. Coronary flow was compared under four conditions: circuit-clamp, continuous mode (constant pump speed), counterpulse mode (increased pump speed in diastole), and copulse mode (increased pump speed in systole). There were no significant baseline changes between these groups. In counterpulse mode, coronary flow increased significantly compared with that in continuous mode. The waveform analysis clearly revealed that counterpulse mode mainly resulted in increased diastolic coronary flow. In conclusion, counterpulse mode of rotary LVADs can enhance myocardial perfusion. This novel drive mode can provide great benefits to the patients with end-stage heart failure, especially those with ischemic etiology.

Journal ArticleDOI
TL;DR: The self‐gated IntraGateFLASH method is suitable for routine use in cardiac MRI in mice with myocardial infarcts as well as in control mice, and obviates the need for electrocardiogram triggering and respiratory gating.
Abstract: Measurement of cardiac function is often performed in mice after, for example, a myocardial infarction. Cardiac MRI is often used because it is noninvasive and provides high temporal and spatial resolution for the left and right ventricle. In animal cardiac MRI, the quality of the required electrocardiogram signal is variable and sometimes deteriorates over time, especially with infarcted hearts or cardiac hypertrophy. Therefore, we compared the self-gated IntraGateFLASH method with a prospectively triggered FLASH (fast low-angle shot) method in mice with myocardial infarcts (n = 16) and in control mice (n = 21). Mice with a myocardial infarct and control mice were imaged in a vertical 9.4-T MR system. Images of contiguous 1-mm slices were acquired from apex to base with prospective and self-gated methods. Data were processed to calculate cardiac function parameters for the left and right ventricle. The signal-to-noise and contrast-to-noise ratios were calculated in mid-ventricular slices. The signal-to-noise and contrast-to-noise ratios of the self-gated data were higher than those of the prospectively gated data. Differences between the two gating methods in the cardiac function parameters for both left and right ventricle (e.g. end-diastolic volumes) did not exceed the inter-observer variability in control or myocardial infarcted mice. Both methods gave comparable results with regard to the cardiac function parameters in both healthy control mice and mice with myocardial infarcts. Moreover, the self-gated method provided better signal-to-noise and contrast-to-noise ratios when the acquisition time was equal. In conclusion, the self-gated method is suitable for routine use in cardiac MRI in mice with myocardial infarcts as well as in control mice, and obviates the need for electrocardiogram triggering and respiratory gating. In both gating methods, more than 10 frames per cardiac cycle are recommended. Copyright © 2010 John Wiley & Sons, Ltd.

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.

Journal ArticleDOI
TL;DR: The concept of LV twisting and untwisting closely linking LV systolic and diastolic function may carry potential diagnostic and therapeutic importance for the management of critically ill patients.
Abstract: To describe the mechanics and possible clinical importance of left ventricular (LV) rotation, exemplify techniques to quantify LV rotation and illustrate the temporal relationship of cardiac pressures, electrocardiogram and LV rotation. Review of the literature combined with selected examples of echocardiographic measurements. Rotation of the left ventricle around its longitudinal axis is an important but thus far neglected aspect of the cardiac cycle. LV rotation during systole maximizes intracavitary pressures, increases stroke volume, and minimizes myocardial oxygen demand. Shearing and restoring forces accumulated during systolic twisting are released during early diastole and result in diastolic LV untwisting or recoil promoting early LV filling. LV twist and untwist are disturbed in a number of cardiac diseases and can be influenced by several therapeutic interventions by altering preload, afterload, contractility, heart rate, and/or sympathetic tone. The concept of LV twisting and untwisting closely linking LV systolic and diastolic function may carry potential diagnostic and therapeutic importance for the management of critically ill patients. Future clinical studies need to address the feasibility of assessing LV twist and untwist as well as the relevance of its therapeutic modulation in critically ill patients.

Journal ArticleDOI
TL;DR: The cycle of Ca2+ fluxes during the normal heartbeat is reviewed, which underlie the coupling between excitation and contraction (ECC) and permit a highly synchronized action of cardiac sarcomeres.
Abstract: The macroscopic hallmarks of the normal heartbeat are rapid onset of contraction and rapid relaxation and an inotropic response to both increased end diastolic volume and increased heart rate. At the microscopic level, the calcium ion (Ca2+) plays a crucial role in normal cardiac contraction. This paper reviews the cycle of Ca2+ fluxes during the normal heartbeat, which underlie the coupling between excitation and contraction (ECC) and permit a highly synchronized action of cardiac sarcomeres. Length dependence of the response of the regulatory sarcomeric proteins mediates the Frank–Starling Law of the heart. However, Ca2+ transport may go astray in heart disease and both jeopardize the exquisite mechanism of systole and diastole and triggering arrhythmias. The interplay between weakened and strong segments in nonuniform cardiac muscle may further lead to mechanoelectric feedback—or reverse excitation contraction coupling (RECC) mediating an early diastolic Ca2+ transient caused by the rapid force decrease during the relaxation phase. These rapid force changes in nonuniform muscle may cause arrhythmogenic Ca2+ waves to propagate by activation of neighbouring SR by diffusing Ca2+ ions.

Journal ArticleDOI
TL;DR: It is concluded that anatomical shift of the leading pacemaker in the rabbit heart could be achieved through gradient of expression of β1-adrenergic receptors and I(K,ACh).

Journal ArticleDOI
TL;DR: Cardiac wall strains display significant temporal, regional, and transmural variations of active fiber contraction and are of particular clinical significance when characterizing stages of left ventricular remodeling, but also of engineering relevance when designing new biomaterials of similar structure and function.
Abstract: Progressive alterations in cardiac wall strains are a classic hallmark of chronic heart failure. Accordingly, the objectives of this study are to establish a baseline characterization of cardiac strains throughout the cardiac cycle, to quantify temporal, regional, and transmural variations of active fiber contraction, and to identify pathways of mechanical activation in the healthy beating heart. To this end, we insert two sets of twelve radiopaque beads into the heart muscle of nine sheep; one in the anterior-basal and one in the lateral-equatorial left ventricular wall. During three consecutive heartbeats, we record the bead coordinates via biplane videofluoroscopy. From the resulting four-dimensional data sets, we calculate the temporally and transmurally varying Green-Lagrange strains in the anterior and lateral wall. To quantify active contraction, we project the strains onto the local muscle fiber directions. We observe that mechanical activation is initiated at the endocardium slightly after end diastole and progresses transmurally outward, reaching the epicardium slightly before end systole. Accordingly, fibers near the outer wall are in contraction for approximately half of the cardiac cycle while fibers near the inner wall are in contraction almost throughout the entire cardiac cycle. In summary, cardiac wall strains display significant temporal, regional, and transmural variations. Quantifying wall strain profiles might be of particular clinical significance when characterizing stages of left ventricular remodeling, but also of engineering relevance when designing new biomaterials of similar structure and function.

Book ChapterDOI
18 Sep 2011
TL;DR: This paper simulates and visualize blood flow through the human heart, using the reconstructed 4D motion of the endocardial surface of the left ventricle as boundary conditions and uses the simulation results to compare the blood flow within one healthy heart and two diseased hearts.
Abstract: In this paper, we present a method to simulate and visualize blood flow through the human heart, using the reconstructed 4D motion of the endocardial surface of the left ventricle as boundary conditions. The reconstruction captures the motion of the full 3D surfaces of the complex features, such as the papillary muscles and the ventricular trabeculae. We use visualizations of the flow field to view the interactions between the blood and the trabeculae in far more detail than has been achieved previously, which promises to give a better understanding of cardiac flow. Finally, we use our simulation results to compare the blood flow within one healthy heart and two diseased hearts.

Patent
26 Apr 2011
TL;DR: In this article, a system and method for generating a stimulation energy to provide His-bundle stimulation for a cardiac cycle, receiving electrical information from the heart over at least a portion of the cardiac cycle was discussed.
Abstract: This document discusses, among other things, a system and method for generating a stimulation energy to provide His-bundle stimulation for a cardiac cycle, receiving electrical information from the heart over at least a portion of the cardiac cycle, determining a characteristic of at least a portion of the received electrical information for the cardiac cycle, and classifying the cardiac cycle using the determined characteristic.

Patent
22 Dec 2011
TL;DR: In this paper, a parameter processor calculates a contraction status parameter value based on the at least one sensor signal, which represents an elongation of the ventricle following onset of ventricular activation during a cardiac cycle.
Abstract: An implantable medical device receives at least one sensor signal representing inter-movement between a basal region of a heart ventricle and a ventricle apex during at least a portion of a systolic phase of a cardiac cycle. A parameter processor calculates a contraction status parameter value based on the at least one sensor signal. This contraction status parameter value represents an elongation of the ventricle following onset of ventricular activation during a cardiac cycle. The contraction status parameter value is stored in a memory as a diagnostic parameter representing a current contraction status of a subject's heart.

Journal ArticleDOI
TL;DR: A novel ARF-based imaging technique, the displacement ratio rate (DRR) method, was developed to rank the relative stiffnesses of dynamically varying tissue, and results predicted a similar cyclic stiffness variation to that offered by velocimetry while being insensitive to variations in applied radiation force.
Abstract: A noninvasive method of characterizing myocardial stiffness could have significant implications in diagnosing cardiac disease. Acoustic radiation force (ARF)–driven techniques have demonstrated their ability to discern elastic properties of soft tissue. For the purpose of myocardial elasticity imaging, a novel ARF-based imaging technique, the displacement ratio rate (DRR) method, was developed to rank the relative stiffnesses of dynamically varying tissue. The basis and performance of this technique was demonstrated through numerical and phantom imaging results. This new method requires a relatively small temporal (<1 ms) and spatial (tenths of mm2) sampling window and appears to be independent of applied ARF magnitude. The DRR method was implemented in two in vivo canine studies, during which data were acquired through the full cardiac cycle by imaging directly on the exposed epicardium. These data were then compared with results obtained by acoustic radiation force impulse (ARFI) imaging and shear wave velocimetry, with the latter being used as the gold standard. Through the cardiac cycle, velocimetry results portray a range of shear wave velocities from 0.76–1.97 m/s, with the highest velocities observed during systole and the lowest observed during diastole. If a basic shear wave elasticity model is assumed, such a velocity result would suggest a period of increased stiffness during systole (when compared with diastole). Despite drawbacks of the DRR method (i.e., sensitivity to noise and limited stiffness range), its results predicted a similar cyclic stiffness variation to that offered by velocimetry while being insensitive to variations in applied radiation force.

Journal ArticleDOI
01 Mar 2011-Europace
TL;DR: A high concordance was found between sonR and the cardiac ultrasound in the timings of aortic and mitral valve closures and in the estimation of systolic and diastolic intervals durations, suggesting that sonR could be used to monitor cardiac function and adaptively optimize CRT systems.
Abstract: AIMS: Optimization of cardiac resynchronization therapy (CRT) requires the gathering of cardiac functional information. An accurate timing of the phases of the cardiac cycle is key in the optimization process. METHODS AND RESULTS: We compared Doppler echocardiography to an automated system, based on the recording of sonR (formerly endocardial acceleration), in the detection of mitral and aortic valves closures and measurements of the duration of systole and diastole. We prospectively studied, under various conditions of cardiac stimulation, 75 recipients of CRT systems (69% men), whose mean age was 72 ± 9.2 years, left ventricular ejection fraction 35 ± 11%, baseline QRS duration 154 ± 29 ms, and New York Heart Association functional class 3.0 ± 0.7. We simultaneously recorded (i) sonR, detected by a non-invasive piezoelectric micro-accelerometer sensor clipped onto an electrode located in the parasternal region, (b) electrocardiogram, and (c) Doppler audio signals, using a multichannel data acquisition and analysis system. The correlation between timing of mitral and aortic valve closure by sonR vs. Doppler signals was examined by linear regression analysis. Correlation coefficients and the average absolute error were calculated. A concordance in the timing of the mitral (r = 0.86, error = 9.7 ms) and aortic (r = 0.93, error = 9.7 ms) valves closure was observed between the two methods in 94% of patients. Similarly, sonR and the Doppler-derived measurements of systolic (r = 0.85, error = 13.4 ms) and diastolic (r = 0.99, error = 12 ms) interval durations were concordant in 80% of patients. CONCLUSION: A high concordance was found between sonR and the cardiac ultrasound in the timings of aortic and mitral valve closures and in the estimation of systolic and diastolic intervals durations. These observations suggest that sonR could be used to monitor cardiac function and adaptively optimize CRT systems.

Book ChapterDOI
25 May 2011
TL;DR: This reconstruction framework captures the motion of the full 3D surfaces of the complex anatomical features, such as the papillary muscles and the ventricular trabeculae, for the first time, which allows us to quantitatively investigate their possible functional significance in health and disease.
Abstract: Recent developments on the 320 multi-detector CT technologies have made the volumetric acquisition of 4D high resolution cardiac images in a single heart beat possible. In this paper, we present a framework that uses these data to reconstruct the 4D motion of the endocardial surface of the left ventricle (LV) for a full cardiac cycle. This reconstruction framework captures the motion of the full 3D surfaces of the complex anatomical features, such as the papillary muscles and the ventricular trabeculae, for the first time, which allows us to quantitatively investigate their possible functional significance in health and disease.

Journal ArticleDOI
TL;DR: In this paper, an elastic 3D image registration of dynamic volume sequences with variable contrast is introduced to improve quantification of myocardial perfusion parameters on a per voxel basis.
Abstract: Large area detector computed tomography systems with fast rotating gantries enable volumetric dynamic cardiac perfusion studies. Prospectively, ECG-triggered acquisitions limit the data acquisition to a predefined cardiac phase and thereby reduce x-ray dose and limit motion artefacts. Even in the case of highly accurate prospective triggering and stable heart rate, spatial misalignment of the cardiac volumes acquired and reconstructed per cardiac cycle may occur due to small motion pattern variations from cycle to cycle. These misalignments reduce the accuracy of the quantitative analysis of myocardial perfusion parameters on a per voxel basis. An image-based solution to this problem is elastic 3D image registration of dynamic volume sequences with variable contrast, as it is introduced in this contribution. After circular cone-beam CT reconstruction of cardiac volumes covering large areas of the myocardial tissue, the complete series is aligned with respect to a chosen reference volume. The results of the registration process and the perfusion analysis with and without registration are evaluated quantitatively in this paper. The spatial alignment leads to improved quantification of myocardial perfusion for three different pig data sets.

Patent
Shantanu Sarkar1
17 Mar 2011
TL;DR: In this paper, a medical device performs a method for determining a cardiac event by obtaining a signal comprising cardiac cycle length information in a patient and determining cardiac cycle lengths during an established time interval.
Abstract: A medical device performs a method for determining a cardiac event by obtaining a signal comprising cardiac cycle length information in a patient and determining cardiac cycle lengths during an established time interval. Noise is detected during the time interval and a cardiac cycle length corresponding to a time of the detected noise is rejected. Cycle length differences are determined from the cycle lengths not rejected during the time interval. The cardiac event is determined in response to the cycle length differences.

Journal ArticleDOI
TL;DR: In this article, the authors showed that CT can show detailed anatomy of the coronary sinus, including muscle connections and sinus function; compared with the normal group, the atrial fibrillation group showed no difference in muscle connections.
Abstract: Our study demonstrates that CT can show detailed anatomy of the coronary sinus, including muscle connections and coronary sinus function; compared with the normal group, the atrial fibrillation group showed no difference in muscle connections, although none of the patients with atrial fibrillation demonstrated coronary sinus contraction at atrial systole.

Journal ArticleDOI
TL;DR: A procedure is presented to generate a comprehensive computational model of the left atrium, including physiological loads, boundary conditions (pericardium, pulmonary veins and mitral valve annulus movement) and mechanical properties based on planar biaxial experiments, able to accurately reproduce the in vivo dynamics of theleft atrium during the passive portion of the cardiac cycle.

Journal ArticleDOI
TL;DR: This paper presents a patient specific deformable heart model that involves the known electrical and mechanical properties of the cardiac cells and tissue and enables the adjustment of deformable model parameters in real-time.

01 Jan 2011
TL;DR: An algorithm has been developed to preprocess and to automatically determine the R-R interval of ECG signal based on Discrete Wavelet Transformation (DWT) and the accuracy of the analysis can be increased and the analysis time can be reduced.
Abstract: Detection of QRS-complexes takes an important role in the analysis of ECG signal, based on which the number of heart beats and an irregularity of a heart beat through R-R interval can be determined. Since an ECG may be of different lengths and as being a non-stationary signal, the irregularity may not be periodic instead it can be shown up at any interval of the signal, it is difficult for physician to analyze ECG manually. In the present study an algorithm has been developed to preprocess and to automatically determine the R-R interval of ECG signal based on Discrete Wavelet Transformation (DWT). The developed algorithm initially performs preprocessing of a signal in order to remove Baseline Drift (De-trending) and noise (De-noising) from the signal and then it uses the preprocessed signal for finding R-R interval of the ECG signal automatically. By using developed algorithm, the accuracy of the analysis can be increased and the analysis time can be reduced. Keywords-ECG, QRS-complex, R-R interval, DWT, Baseline Drift, De-noising. I. INTRODUCTION The Electrocardiogram (ECG or EKG) is a graphic record of the direction and magnitude of electrical activity of the heart that is generated by depolarization and repolarization of the atria and ventricles (1). Depolarization occurs when the cardiac cell, which are electrically polarized, lose their internal negativity. The spread of depolarization travels from cell to cell, producing a wave of depolarization across the entire heart. This wave represents a flow of electricity that can be detected by electrodes placed on the surface of the body. Once depolarization is completed the cardiac cells are restored to their resting potential, a process called repolarization. This flow of energy takes in the form of ECG wave and is composed of P wave followed by QRS complex followed by T wave followed by U wave per cardiac cycle which is shown in Fig. 1. The P wave is a small low-voltage deflection away from the baseline caused by the depolarization of the atria prior to atria contraction. QRS-complex is the largest-amplitude portion of the ECG, caused by currents generated when the ventricles depolarize prior to their contraction. The T-wave is the result of ventricular repolarization and finally the small U wave although not always visible, is considered to be a representation of the Papillary Muscle or Purkinje Fibers. Generally, the condition of a heart can be determined by extracting features (2) from the ECG signal. These features include the amplitudes of the waves and the intervals between them. A normal ECG signal has the following amplitudes values: P-wave 0.25 mV, R-wave 1.6mV, Q-wave 25% of the R-wave, T-wave 0.1 to 0.5 mV; the time interval values: PR-interval 0.12-0.2s, QRS complex 0.04 to 0.12s, QT interval <0.42s and the heart rate of 60-100 beats/min (3). Any change in the above said values indicates the abnormality of the heart. Vanisree K et al. / International Journal on Computer Science and Engineering (IJCSE)