Showing papers on "Cardiac cycle published in 2019"
TL;DR: An automated computer aided diagnostic (CAD) system that can expedite the process of arrhythmia diagnosis, as an aid to clinicians to provide appropriate and timely intervention to patients is developed.
106 citations
TL;DR: In patients with atrial fibrillation and absent LA contraction, the normal predominantly “atriogenic” annular dynamics become “ventriculogenic.”
Abstract: Background Patients with atrial fibrillation (AF) and left atrial (LA) enlargement may develop functional, normal leaflet motion mitral regurgitation (MR) without left ventricular (LV) remodeling. Mitral annular dynamics and LV mechanics are important for preserving normal mitral valve function. The aim of this study was to assess the annular and LV dynamics in patients with AF and functional MR. Methods Twenty-one patients with AF with moderate or more MR (AFMR+ group), 46 matched patients with AF with no or mild MR (AFMR− group), and 19 normal patients were retrospectively studied. Mitral annular dynamics were quantitatively assessed using three-dimensional echocardiography. Systolic LV global longitudinal strain (GLS), global circumferential strain, and LA strain were measured using two-dimensional speckle-tracking echocardiography. Results The normal annulus displayed presystolic followed by systolic contraction and increase in saddle shape (P .05 vs normal). In contrast, systolic and total annular dynamics during the cardiac cycle were preserved in AFMR− patients (P > .10 vs normal) but impaired in AFMR+ patients (P Conclusions In patients with AF and absent LA contraction, the normal predominantly “atriogenic” annular dynamics become “ventriculogenic.” Isolated LA enlargement is insufficient to cause important MR without coexisting abnormal LV mechanics and annular dynamics during systole. “Atrial” functional MR may not be purely an atrial disorder.
50 citations
TL;DR: The tricuspid annulus in patients with HLHS with a Fontan circulation changes in shape significantly throughout the cardiac cycle but remains relatively planar, and these findings may inform annuloplasty methods and subvalvular interventions in these complex patients.
Abstract: Background Tricuspid regurgitation (TR) is a significant contributor to morbidity and mortality in patients with hypoplastic left heart syndrome. The goal of this study was to characterize the dynamic annular motion of the tricuspid valve in patients with HLHS with a Fontan circulation and assess the relation to tricuspid valve function. Methods Tricuspid annuli of 48 patients with HLHS with a Fontan circulation were modeled at end-diastole, mid-systole, end-systole, and mid-diastole using transthoracic three-dimensional echocardiography and custom code in 3D Slicer. The angle of the anterior papillary muscle (APM) relative to the annular plane in each systolic phase was also measured. Results Imaging was performed 5.0 years (interquartile range, 2–11 years) after Fontan operation. The tricuspid annulus varies in shape significantly throughout the cardiac cycle, changing in sphericity (P Conclusions The tricuspid annulus in patients with HLHS with a Fontan circulation changes in shape significantly throughout the cardiac cycle but remains relatively planar. Increased change in septolateral diameter and decreased APM angle are strongly associated with the presence of TR. These findings may inform annuloplasty methods and subvalvular interventions in these complex patients.
30 citations
TL;DR: Interactions between cardiac activity and conscious somatosensory perception are demonstrated, which highlights the importance of internal bodily states for sensory processing beyond the auditory and visual domain.
Abstract: Fluctuations in the heart's activity can modulate the access of external stimuli to consciousness. The link between perceptual awareness and cardiac signals has been investigated mainly in the visual and auditory domain. Here, we investigated whether the phase of the cardiac cycle and the prestimulus heart rate influence conscious somatosensory perception. We also tested how conscious detection of somatosensory stimuli affects the heart rate. Electrocardiograms (ECG) of 33 healthy volunteers were recorded while applying near-threshold electrical pulses at a fixed intensity to the left index finger. Conscious detection was not uniformly distributed across the cardiac cycle but significantly higher in diastole than in systole. We found no evidence that the heart rate before a stimulus influenced its detection, but hits (correctly detected somatosensory stimuli) led to a more pronounced cardiac deceleration than misses. Our findings demonstrate interactions between cardiac activity and conscious somatosensory perception, which highlights the importance of internal bodily states for sensory processing beyond the auditory and visual domain.
27 citations
TL;DR: In this article, the authors found a significant coupling of saccades, subsequent fixations, and blinks with the phase of the cardiac cycle, which has been reported as the period of maximal effect of the baroreceptors9 activity upon cognition.
Abstract: Recent research has demonstrated that perception and reasoning vary according to the phase of internal bodily signals such as heartbeat. This has been shown by locking the presentation of sensory events to distinct phases of the cardiac cycle. However, task-relevant information is not usually encountered in such a phase-locked manner nor passively accessed, but rather actively sampled at one9s own pace. Moreover, if the phase of the cardiac cycle is an important modulator of perception and cognition, as previously proposed, then the way in which we actively sample the world should be similarly modulated by the phase of the cardiac cycle. Here we tested this by coregistration of eye movements and heartbeat signals while participants freely compared differences between two visual arrays. Across three different analyses, we found a significant coupling of saccades, subsequent fixations, and blinks with the cardiac cycle. More eye movements were generated during the systolic phase of the cardiac cycle, which has been reported as the period of maximal effect of the baroreceptors9 activity upon cognition. Conversely, more fixations were found during the diastole phase (quiescent baroreceptors). Lastly, more blinks were generated in the later period of the cardiac cycle. These results suggest that interoceptive and exteroceptive processing do adjust to each other; in our case, by sampling the outer environment during quiescent periods of the inner organism.
24 citations
TL;DR: The 3D microstructure of the LV is described, in vivo and ex vivo cardiac MR diffusion acquisition and postprocessing techniques are explained, as well as clinical applications to date.
Abstract: The 3D microarchitecture of the cardiac muscle underlies the mechanical and electrical properties of the heart. Cardiomyocytes are arranged helically through the depth of the wall, and their shortening leads to macroscopic torsion, twist, and shortening during cardiac contraction. Furthermore, cardiomyocytes are organized in sheetlets separated by shear layers, which reorientate, slip, and shear during macroscopic left ventricle (LV) wall thickening. Cardiac diffusion provides a means for noninvasive interrogation of the 3D microarchitecture of the myocardium. The fundamental principle of MR diffusion is that an MRI signal is attenuated by the self-diffusion of water in the presence of large diffusion-encoding gradients. Since water molecules are constrained by the boundaries in biological tissue (cell membranes, collagen layers, etc.), depicting their diffusion behavior elucidates the shape of the myocardial microarchitecture they are embedded in. Cardiac diffusion therefore provides a noninvasive means to understand not only the dynamic changes in cardiac microstructure of healthy myocardium during cardiac contraction but also the pathophysiological changes in the presence of disease. This unique and innovative technology offers tremendous potential to enable improved clinical diagnosis through novel microstructural and functional assessment. in vivo cardiac diffusion methods are immediately translatable to patients, opening new avenues for diagnostic investigation and treatment evaluation in a range of clinically important cardiac pathologies. This review article describes the 3D microstructure of the LV, explains in vivo and ex vivo cardiac MR diffusion acquisition and postprocessing techniques, as well as clinical applications to date. Level of Evidence: 1 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2019. J. Magn. Reson. Imaging 2020;52:348-368.
24 citations
TL;DR: High-frame-rate Doppler echocardiography enabled us to retrieve time-resolved dynamics of the myocardium and vortex flow within the same cardiac cycle, and could be of clinical relevance for early diagnosis of filling impairment.
Abstract: Echocardiography is widely used to provide critical left ventricular indices describing myocardial motion and blood inflow velocity. Tissue motion and blood flow are strongly connected and interdependent in the ventricle. During cardiac relaxation, rapid filling leads to the formation of a vortical blood flow pattern. In this paper, we introduce a high-frame-rate method to track vortex dynamics alongside myocardium motion, in a single heartbeat. Cardiac triplex imaging (B-mode + tissue Doppler + color Doppler) was obtained by insonating the left ventricle with diverging waves. We used coherent compounding with integrated motion compensation to obtain high-quality B-mode images. Tissue Doppler was retrieved and the septal and lateral velocities of the mitral annulus were deduced. A rate of ~80 triplex images/s was obtained. Vortex dynamics was analyzed by Doppler vortography. Blood vortex signature maps were used to track the vortex and compute core vorticities. The sequence was implemented in a Verasonics scanner with a 2.5-MHz phased array and tested in vivo in 12 healthy volunteers. Two main peaks appeared on the vorticity curves. These peaks were synchronized with the mitral inflow velocities with a small delay. We observed a relationship between the tissue and vortex waveforms, though also with a delay, which denoted the lag between the wall and the flow motion. Clinical diastolic indices combining basal and mitral inflow velocities (E/A ratio and E/ $e^\prime $ ratio) were determined and compared with those measured using a conventional ultrasound scanner; a good correlation was obtained ( $r^{2} = 0.96$ ). High-frame-rate Doppler echocardiography enabled us to retrieve time-resolved dynamics of the myocardium and vortex flow within the same cardiac cycle. Coupling wall-flow analysis could be of clinical relevance for early diagnosis of filling impairment.
20 citations
TL;DR: In 62 patients with pulmonary arterial hypertension, timing of maximal backflow in the vena cava was in late diastole, during the right atrial contraction, and the amount of backflow was associated with right ventricular stiffness.
Abstract: Vena cava backflow is a well-recognised clinical hallmark of right ventricular failure in pulmonary arterial hypertension (PAH). Backflow may result from tricuspid regurgitation during right ventricular systole or from impaired right ventricular diastolic filling during atrial contraction. Our aim was to quantify the forward and backward flow in the vena cava and to establish the main cause in PAH.In 62 PAH patients, cardiac magnetic resonance measurements provided volumetric flows (mL·s-1) in the superior and inferior vena cava; time integration of flow gave volume. The "backward fraction" was defined as the ratio of the backward and forward volumes in the vena cava, expressed as a percentage. Time of maximum vena cava backflow was expressed as a percentage of the cardiac cycle. Right ventricular volumes and aortic stroke volume were determined. Right heart catheterisation gave right ventricular and right atrial pressures. Right ventricular end-diastolic stiffness was determined with the single-beat method.The median (interquartile range) backward fraction was 12% (3-24%) and it was >20% in 21 patients. Maximum backflow occurred at near 90% of the cardiac cycle, coinciding with atrial contraction. The backward fraction was associated with maximal right atrial pressure (Spearman's r=0.77), right ventricular end-diastolic stiffness (r=0.65) and right ventricular end-diastolic pressure (r=0.77), and was negatively associated with stroke volume (r= -0.61) (all p<0.001).Significant backward flow in the vena cava was observed in a large group of PAH patients and occurred mostly during atrial contraction as a consequence of impaired right ventricular filling due to right ventricular diastolic stiffness. The backward flow due to tricuspid regurgitation was of significance in only a small minority of patients.
15 citations
TL;DR: It is concluded that the tomographic particle imaging velocimetry setup provides a useful ground truth measurement of flow features and allows a comparison of the effects of different valve types on left ventricular flow patterns.
15 citations
TL;DR: The entire myocardium rearranges through the cardiac cycle with the change in the orientation of the aggregations of cardiomyocytes being the predominant mediator of myocardial wall thickening.
Abstract: The three-dimensional rearrangement of the right ventricular (RV) myocardium during cardiac deformation is unknown. Previous in-vivo studies have shown that myocardial left ventricular (LV) deformation is driven by rearrangement of aggregations of cardiomyocytes that can be characterised by changes in the so-called E3-angle. Ex-vivo imaging offers superior spatial resolution compared with in-vivo measurements, and can thus provide novel insight into the deformation of the myocardial microstructure in both ventricles. This study sought to describe the dynamic changes of the orientations of the cardiomyocytes in both ventricles brought upon by cardiac contraction, with particular interest in the thin-walled RV, which has not previously been described in terms of its micro-architecture. The hearts of 14 healthy 20 kg swine were excised and preserved in either a relaxed state or a contracted state. Myocardial architecture was assessed and compared between the two contractional states by quantification of the helical, transmural and E3-angles of the cardiomyocytes using high-resolution diffusion tensor imaging. The differences between the two states of contraction were most pronounced in the endocardium where the E3-angle decreased from 78.6° to 24.8° in the LV and from 82.6° to 68.6° in the RV. No significant change in neither the helical nor the transmural angle was found in the cardiomyocytes of the RV. In the endocardium of the LV, however, the helical angle increased from 35.4° to 47.8° and the transmural angle increased from 3.1° to 10.4°. The entire myocardium rearranges through the cardiac cycle with the change in the orientation of the aggregations of cardiomyocytes being the predominant mediator of myocardial wall thickening. Interestingly, differences also exist between the RV and LV, which helps in the explanation of the different physiological capabilities of the ventricles.
14 citations
TL;DR: The potential of 3D-DIC to perform dynamic measurement of displacement and strain during heart deformations is demonstrated and supports future applications of this method in ex vivo beating heart platforms, which replicate more fully the complex contraction of the heart.
TL;DR: The principal structure of the aortic root is highlighted and the role played by the sinuses of Valsalva in regulating the blood flow exiting the ventricle underline the concept that "form follows function" and emphasizes the importance of a good anatomical reconstruction for an optimal and long-lasting valve function.
Abstract: The aortic root is an important anatomical structure positioned at the center of the heart, making it critical to the functioning of the major cardiac chambers. Deep knowledge of the anatomical "surroundings" of the aortic root is crucial for surgeon attempting to spare or repair a leaking aortic valve. In fact, root dissection is a necessary step to "skeletonize" the aortic valve, allowing the surgeon to work on the critical components of its structure, namely the aorto-ventricular junction, the virtual basal ring (VBR) and the sino-tubular junction (STJ). These three components, along with the insertion of the leaflet to the aortic wall, form the skeleton of the aortic valve that is essential in guaranteeing valve competence. A good anatomical proportion between the various component of the skeleton of the aortic valve need to be verified, or re-established in order to set the basis for an optimal aortic valve repair. Once the skeleton of the heart has been correctly addressed, the condition of the valve leaflets need to be considered. Excess of leaflet tissue is treated by leaflet plication or resection and lack of leaflet tissue is addressed by tissue extension with autologous or heterologous materials. In the present manuscript, we highlight the principal structure of the aortic root and describe in detail each anatomical component. This basic anatomical knowledge is also important for a through understanding of the normal function of the valve and root structure during the cardiac cycle. The close boundaries existing between the left ventricular cavity and the aorta are important in explaining the sophisticated function of opening and closing of the aortic valve. Similarly, the role played by the sinuses of Valsalva in regulating the blood flow exiting the ventricle underline the concept that "form follows function" and emphasizes the importance of a good anatomical reconstruction for an optimal and long-lasting valve function.
TL;DR: In this article, the mitral valve is modeled and simulated using a design-based methodology, and the model geometry and the forces that are needed to support a given load are derived.
Abstract: This work is concerned with modeling and simulation of the mitral valve, one of the four valves in the human heart. The valve is composed of leaflets, the free edges of which are supported by a system of chordae, which themselves are anchored to the papillary muscles inside the left ventricle. First, we examine valve anatomy and present the results of original dissections. These display the gross anatomy and information on fiber structure of the mitral valve. Next, we build a model valve following a design-based methodology, meaning that we derive the model geometry and the forces that are needed to support a given load and construct the model accordingly. We incorporate information from the dissections to specify the fiber topology of this model. We assume the valve achieves mechanical equilibrium while supporting a static pressure load. The solution to the resulting differential equations determines the pressurized configuration of the valve model. To complete the model, we then specify a constitutive law based on a stress-strain relation consistent with experimental data that achieves the necessary forces computed in previous steps. Finally, using the immersed boundary method, we simulate the model valve in fluid in a computer test chamber. The model opens easily and closes without leak when driven by physiological pressures over multiple beats. Further, its closure is robust to driving pressures that lack atrial systole or are much lower or higher than normal.
TL;DR: Doppler tissue imaging is necessary as a surrogate of ventricular relaxation to further determine the stages of diastolic dysfunction in patients with preserved ejection fraction, and the mitral flow velocity curves are representative of the relative driving pressure between left atrium and left ventricle and allow one to grade the progression of diastsolic dysfunction which occurs in disease states.
TL;DR: The study aimed to characterize the geometry of the aortic root pre‐ and post‐transcatheter aortsic valve replacement (TAVR) and investigate differences in pre- and post-TAVR anatomy.
Abstract: Purpose The study aimed to characterize the geometry of the aortic root pre- and post-transcatheter aortic valve replacement (TAVR) and investigate differences in pre- and post-TAVR anatomy. Background A greater understanding of how aortic root geometry changes after TAVR is needed to facilitate further investigation into the hemodynamic profiles of the post-TAVR aortic root. Methods Anatomical measurements were conducted on de-identified, retrospective post-TAVR 4DCT scans of 109 patients with aortic stenosis obtained from the RESOLVE study. The diameter of the aortic root was measured at the level of the annulus, left ventricular outflow tract (LVOT), sinus of Valsalva, sinotubular junction (STJ) and ascending aorta. The heights of the STJ and coronary arteries were also measured. Results All aortic root dimensions were normally distributed across the cohort and changed significantly between pre- and post-TAVR conditions (P 0.95, P Conclusions There are significant differences between pre- and post-TAVR as well as peak systolic and end diastolic aortic root anatomy. Appropriate anatomical dimensions should be selected for benchtop testing as the geometry varies greatly throughout the cardiac cycle.
TL;DR: Patients with primary aldosteronism, especially APA, had impairedleft atrial deformation mechanics and increased left atrial stiffness, providing a promising insight into early detection of subclinical left atrian dysfunction by strain echocardiography.
Abstract: BACKGROUND We investigated the left atrial myocardial deformation in patients with primary aldosteronism using the speckle-tracking echocardiographic (STE) strain imaging technique. METHODS Our study included 107 primary aldosteronism patients [52 aldosterone-producing adenoma (APA) and 55 idiopathic hyperaldosteronism (IHA)] and 50 primary hypertensive patients. We performed conventional echocardiography to measure left atrial volume and ejection fraction, and STE to estimate left atrial myocardial deformation including peak velocity, strain and strain rate and calculate the ratio of E/e' to left atrial strain during left ventricular systole as the left atrial stiffness index. RESULTS Patients with APA, compared with those with IHA and primary hypertension had a significantly (P < 0.001) lower serum potassium concentration and higher 24-h urinary aldosterone excretion and plasma aldosterone-to-renin ratio. Patients with APA had a significantly (P < 0.01) larger maximal, precontraction, and minimal left atrial volumes and lower total, active and passive left atrial emptying fractions than those with IHA and primary hypertension. Among the three groups, patients with APA showed lowest left atrial velocity, strain, and strain rate during ventricular systole, early diastole and late diastole (P < 0.05) and highest left atrial stiffness index (P < 0.001). In unadjusted analysis, the left atrial strain, strain rate and stiffness index were significantly (P < 0.05) associated with plasma aldosterone concentration and urinary aldosterone excretion. After adjustment for various confounding factors, these associations remained statistically significant for urinary aldosterone excretion (P < 0.05) but not plasma aldosterone concentration (P ≥ 0.05). CONCLUSION Patients with primary aldosteronism, especially APA, had impaired left atrial deformation mechanics and increased left atrial stiffness, providing a promising insight into early detection of subclinical left atrial dysfunction by strain echocardiography.
TL;DR: The findings provide new insight about the effect of fluid dynamics on LV TE risk, and suggest that the bioprosthesis valve in the mitral position minimizes this risk by producing more physiological flow patterns in patients with diluted cardiomyopathy.
Abstract: Dilated cardiomyopathy produces abnormal left ventricular (LV) blood flow patterns that are linked with thromboembolism (TE). We hypothesized that implantation of mechanical heart valves non-trivially influences TE risk in these patients, exacerbating abnormal LV flow dynamics. The goal of this study was to assess how mitral valve design impacts flow and hemodynamic factors associated with TE. The mid-plane velocity field of a silicone dilated LV model was measured in a mock cardiovascular loop for three different mitral prostheses, two with multiple orientations, and used to characterize LV vortex properties through the cardiac cycle. Blood residence time and a platelet shear activation potential index (SAP) based on the cumulative exposure to shear were also computed. The porcine bioprosthesis (BP) and the bileaflet valve in the anti-anatomical (BL-AA) position produced the most natural flow patterns. The bileaflet valves experienced large shear in the valve hinges and recirculating shear-activated flow, especially in the anatomical (BL-A) and 45-degree (BL-45) positions, thus exhibited high SAP. The tilting disk valve in the septal orientation (TD-S) produced a complete reversal of flow and vortex properties, impairing LV washout and retaining shear-activated fluid, leading to the highest residence time and SAP. In contrast, the tilting disk valve in the free-wall position (TD-F) exhibited mid-range values for residence time and SAP. Hence, the thrombogenic potential of different MHV models and configurations can be collectively ranked from lowest to highest as: BP, BL-AA, TD-F, BL-A, BL-45, and TD-S. These findings provide new insight about the effect of fluid dynamics on LV TE risk, and suggest that the bioprosthesis valve in the mitral position minimizes this risk by producing more physiological flow patterns in patients with dilated cardiomyopathy.
TL;DR: Parameter dependencies found in the current study indicate that the hematocrit is influential when conducting patient-specific modelling of prosthetic heart valves.
TL;DR: This work proposes a novel approach for the identification of the anterior mitral valve leaflet in all frames, which requires a single user-specified point on the posterior wall of the aorta as input, in the first frame.
Abstract: Rheumatic heart disease can result from repeated episodes of acute rheumatic fever, which damages the heart valves and reduces their functionality. Early manifestations of heart valve damage are visible in echocardiography in the form of valve thickening, shape changing and mobility reduction. The quantification of these features is important for a precise diagnosis and it is the main motivation for this work. The first step to make this quantification is to accurately identify and track the anterior mitral leaflet throughout the cardiac cycle. An accurate segmentation and tracking with minimum user interaction is still an open problem in literature due to low image quality, speckle noise, signal dropout and nonrigid deformations. In this work, we propose a novel approach for the identification of the anterior mitral valve leaflet in all frames. The method requires a single user-specified point on the posterior wall of the aorta as input, in the first frame. The echocardiography videos are converted into a new image space, the Virtual M-mode, which samples the original echocardiography image over automatically estimated scanning lines. This new image space not only provides the motion pattern of the posterior wall of the aorta, the anterior wall of the aorta and the posterior wall of the left atrium, but also provides the location of the structures in each frame. The location information is then used to initialize the localized active contours, followed by segmenting the anterior mitral leaflet. Results shown that the new image space has robustly identified the anterior mitral valve leaflet, without any failure. The median modified Hausdorff distance error of the proposed method was 2.3 mm, with a recall of 0.94.
01 Oct 2019
TL;DR: The main function of the left atrium is to connect the pulmonary circulation with the corresponding ventricle, acting as a reservoir, during atrial filling, and when the mitral valve is closed, as a booster, when the atrial contraction ensues, but especiallyacting as a conduit, during diastasis.
Abstract: The main function of the left atrium is to connect the pulmonary circulation with the corresponding ventricle, acting as a reservoir, during atrial filling, when the mitral valve is closed, as a booster, when the atrial contraction ensues, but especially acting as a conduit, during diastasis. Accordingly, the atrial cavity has, in the past, been assigned the minimalistic role of a ‘transit chamber’, devoted exclusively to collecting and redirecting the reflux blood from the pulmonary district towards the systemic circulation. It would be wrong, however, to deduce from this ‘pipeline’ function that the left atrium is a passive player in the complex scenario of the cardiac activity.
Left atrial cavity, in fact, is intimately related to ventricular function throughout the whole cardiac cycle.1 During ventricular systole, longitudinal fibre shortening forces the descent of the cardiac base, contributing to atrial filling from the pulmonary veins2 while, during diastole, the atrium passively and actively contributes to ventricular filling. Since the cavity, during early and mid-diastole, is directly exposed to the ventricular pressure through the open mitral valve, the atrial emptying pattern is obviously strongly influenced by the left heart diastolic properties.3
Atrial function can be best described by the relation between pressure and volume.4 Gathering this information, however, implies the use of a high-fidelity pressure catheter in the atrial chamber, a manoeuvre that is not performed routinely nowadays in clinical practice. A more simplistic way to describe atrial function is to rely on the atrial volume curve, which can easily be obtained nowdays using three-dimensional (3D) echocardiography.5
It must be emphasised, however, that the atrial volume curve does not provide an exact measure of the amount of blood entering the left ventricle from the atrium during diastole. In the phase of passive atrial emptying and atrial diastasis, …
TL;DR: The basic anatomical structure of the heart valves, age-related changes of valve morphometry, heart valve diseases, and general treatment of valvular diseases in humans are reviewed.
Abstract: Cardiac valves are highly complex structures optimizing their function during the cardiac cycle. They open and close directed by blood flow under different pressure conditions in the dynamic environment in the heart. It is acknowledged that the aging process affects the structure and functions of the heart valves. With regard to morphometry, age-related changes of the heart valve can be found in valve circumference, thickness of the leaflet, luminal area at the sinotubular junction, valve diameter, orifice area, and leaflet size in circumferential and radial direction. In addition, there are differences between male and female hearts in some features. Moreover, there are studies the qualitative and quantitative assessment of histological compositions, echocardiography study to investigate the annular circumference and diameter in the human heart valves related with age. Studies into the detailed anatomy of the changes in heart valves with age are important and the correlation between valve morphology and age may be used as an age indicator. This study reviews the basic anatomical structure of the heart valves, age-related changes of valve morphometry, heart valve diseases, and general treatment of valvular diseases in humans. Detailed knowledge of the anatomical features of the morphology of the human heart valve is useful for any treatments of valve pathology.
TL;DR: A four-chamber cardiac model utilizing cubic-Hermite elements and simulated a full cardiac cycle by coupling the 3D finite element model with a lumped circulation model, observing a 20% reduction in acute work done by the heart immediately after myocardial infarction.
TL;DR: Patients with heart failure show myocardial, valvular, and electrical dysfunction, which results in enlarged cardiac chambers and increased intracardiac volume and pressure, so vortex flow analysis-guided treatment in heart failure might be a novel option for cardiac physicians.
TL;DR: The region where the vascular lumen meets the surrounding endothelium cell layer, hence the interface region between haemodynamics and cell tissue, is denoted by the near-wall region in the present work, and simple yet effective numerical recipes to analyse theNear-wall flow field are outlined.
Abstract: The region where the vascular lumen meets the surrounding endothelium cell layer, hence the interface region between haemodynamics and cell tissue, is of primary importance in the physiological functions of the cardiovascular system. The functions include mass transport to/from the blood and tissue, and signalling via mechanotransduction, which are primary functions of the cardiovascular system and abnormalities in these functions are known to affect disease formation and vascular remodelling. This region is denoted by the near-wall region in the present work, and we outline simple yet effective numerical recipes to analyse the near-wall flow field. Computational haemodynamics solutions are presented for six patient specific cerebral aneurysms, at three instances in the cardiac cycle: peak systole, end systole (taken as dicrotic notch) and end diastole. A sensitivity study, based on Newtonian and non-Newtonian rheological models, and different flow rate profiles, is effected for a selection of aneurysm cases. The near-wall flow field is described by the wall shear stress (WSS) and the divergence of wall shear stress (WSSdiv), as descriptors of tangential and normal velocity components, respectively, as well as the wall shear stress critical points. Relations between near-wall and free-stream flow fields are discussed.
TL;DR: An adapted fuzzy membership-based c-means pixel clustering and connected regions component labeling is used for automatic segmentation of the left and right ventricular endocardial volumes, making it much more efficient than deformable methods, which need several iterations for the evolution of the snake or contour.
Abstract: A rapid method for left and right ventricular endocardial volume segmentation and clinical cardiac parameter calculation from MRI images of cardiac patients is presented. The clinical motivation is providing cardiologists a tool for assessing the cardiac function in a patient through the left ventricular endocardial volume’s ejection fraction. A new method combining adapted fuzzy membership-based c-means pixel clustering and connected regions component labeling is used for automatic segmentation of the left and right ventricular endocardial volumes. This proposed pixel clustering with labeling approach avoids manual initialization or user intervention and does not require specifying the region of interest. This method fully automatically extracts the left and right ventricular endocardial volumes and avoids manual tracing on all MRI image frames in the complete cardiac cycle from systole to diastole. The average computational processing time per frame is 0.6 s, making it much more efficient than deformable methods, which need several iterations for the evolution of the snake or contour. Accuracy of the automated method presented herein was validated against manual tracing-based extraction, performed with the guidance of cardiac experts, on several MRI frames. Dice coefficients between the proposed automatic versus manual traced ventricular endocardial volume segmentations were observed to be 0.9781 ± 0.0070 (for left ventricular endocardial volume) and 0.9819 ± 0.0058 (for right ventricular endocardial volume), and the Pearson correlation coefficients were observed to be 0.9655 ± 0.0206 (for left ventricular endocardial volume) and 0.9870 ± 0.0131 (for right ventricular endocardial volume).
TL;DR: The proposed ePTFE bi-leaflet valve design for aortic valve replacement (AVR) exhibited better structural and hemodynamic performances, which improved valve competency and provides a viable option for the future clinical applications.
Abstract: The expanded polytetrafluoroethylene (ePTFE) heart valve can serve as a viable option for prosthetic aortic valve. In this study, an ePTFE bi-leaflet valve design for aortic valve replacement (AVR) is presented, and the performance of the proposed valve was assessed numerically and experimentally. The valve was designed using CAE software. The dynamic behavior of the newly designed bi-leaflet valve under time-varying physiological pressure loading was first investigated by using commercial finite element code. Then, in-vitro tests were performed to validate the simulation and to assess the hemodynamic performance of the proposed design. A tri-leaflet ePTFE valve was tested in-vitro under the same conditions as a reference. The maximum leaflet coaptation area of the bi-leaflet valve during diastole was 216.3 mm2. When fully closed, no leakage gap was observed and the free edges of the molded valve formed S-shaped lines. The maximum Von Mises stress during a full cardiac cycle was 4.20 MPa. The dynamic performance of the bi-leaflet valve was validated by the in-vitro test under physiological aortic pressure pulse. The effective orifice area (EOA), mean pressure gradient, regurgitant volume, leakage volume and energy loss of the proposed valve were 3.14 cm2, 8.74 mmHg, 5.93 ml/beat, 1.55 ml/beat and 98.99 mJ, respectively. This study reports a novel bi-leaflet valve design for AVR. The performance of the proposed valve was numerically and experimentally assessed. Compared with the reference valve, the proposed design exhibited better structural and hemodynamic performances, which improved valve competency. Moreover, the performance of the bi-leaflet design is comparable to commercialized valves available on the market. The results of the present study provide a viable option for the future clinical applications.
TL;DR: Examining the perception of near-threshold electrical pulses across the entire cardiac cycle shows that conscious somatosensory perception is enhanced during the late phase of the cardiac cycle and associated with a more pronounced cardiac deceleration and this strengthens the evidence that the physiological state of the body influences how the authors perceive the world.
Abstract: Fluctuations in the heart’s activity can modulate the access of external stimuli to consciousness. The link between perceptual awareness and cardiac signals has been investigated mainly in the visual and auditory domain. We here investigated whether the phase of the cardiac cycle and the pre-stimulus heart rate influence conscious somatosensory perception. We also tested how conscious detection of somatosensory stimuli affects the heart rate. Electrocardiograms (ECG) of 33 healthy volunteers were recorded while applying near-threshold electrical pulses at a fixed intensity to the left index finger. Conscious detection was not uniformly distributed across the cardiac cycle but significantly higher in diastole than in systole. We found no evidence that the heart rate before a stimulus influenced its detection but hits (correctly detected somatosensory stimuli) led to a more pronounced cardiac deceleration than misses. Our findings demonstrate interactions between cardiac activity and conscious somatosensory perception, which highlights the importance of internal bodily states for sensory processing beyond the auditory and visual domain. Impact Statement It is highly debated to what extent cardiac activity modulates the access of external stimuli to consciousness. The evidence is inconsistent across sensory modalities and previous research focused at specific intervals within the cardiac cycle. Here, we examined the perception of near-threshold electrical pulses across the entire cardiac cycle. Our results show that conscious somatosensory perception is enhanced during the late phase of the cardiac cycle (at diastole) and associated with a more pronounced cardiac deceleration (as compared to non-detected stimuli). This strengthens the evidence that the physiological state of the body influences how we perceive the world.
20 Jul 2019
TL;DR: The Heart Left Ventricle is modelised using a set of recursive spherical harmonics to define a global deformation of the anatomical structure between systole and diastole phases by applying Recursive Spherical Harmonics.
Abstract: In this paper, the Heart Left Ventricle is modelised using a set of recursive spherical harmonics. We model the left ventricle in a compact and relevant way and secondly, it permits to define a global deformation of the anatomical structure between systole and diastole phases by applying Recursive Spherical Harmonics are applied on three left ventricle meshes acquired from cardiac pet scan to analyze their deformation during the cardiac cycle, evaluate cardiac global function and diagnose ventricular diseases. Experimental results proved the efficiency and accuracy of the present method compared to classical spherical harmonics modeling in terms of necessary number of coefficients and running time.
TL;DR: Two quasistatic finite element simulations of the left ventricle to investigate the mechanical effect of intra‐myocardial injection of biomaterials showed cardiomyocyte stress attenuation, offering an explanation for the mechanical reinforcement benefit associated with injection.
Abstract: Myocardial infarction, or heart attack, is the leading cause of mortality globally. Although the treatment of myocardial infarct has improved significantly, scar tissue that persists can often lead to increased stress and adverse remodeling of surrounding tissue and ultimately to heart failure. Intra-myocardial injection of biomaterials represents a potential treatment to attenuate remodeling, mitigate degeneration, and reverse the disease process in the tissue. In vivo experiments on animal models have shown functional benefits of this therapeutic strategy. However, a poor understanding of the optimal injection pattern, volume, and material properties has acted as a barrier to its widespread clinical adoption. In this study, we developed two quasistatic finite element simulations of the left ventricle to investigate the mechanical effect of intra-myocardial injection. The first model employed an idealized left ventricular geometry with rule-based cardiomyocyte orientation. The second model employed a subject-specific left ventricular geometry with cardiomyocyte orientation from diffusion tensor magnetic resonance imaging. Both models predicted cardiac parameters including ejection fraction, systolic wall thickening, and ventricular twist that matched experimentally reported values. All injection simulations showed cardiomyocyte stress attenuation, offering an explanation for the mechanical reinforcement benefit associated with injection. The study also enabled a comparison of injection location and the corresponding effect on cardiac performance at different stages of the cardiac cycle. While the idealized model has lower fidelity, it predicts cardiac function and differentiates the effects of injection location. Both models represent versatile in silico tools to guide optimal strategy in terms of injection number, volume, site, and material properties.
TL;DR: The present study was performed to evaluate the precision of MR thermometry without RF heating in patients exhibiting cardiac arrhythmia in a clinical setting and relied on quantification of changes in temperature measurements caused by noise and physiological motion.
Abstract: BACKGROUND:
Magnetic resonance (MR) thermometry allows visualization of lesion formation in real-time during cardiac radiofrequency (RF) ablation. The present study was performed to evaluate the precision of MR thermometry without RF heating in patients exhibiting cardiac arrhythmia in a clinical setting. The evaluation relied on quantification of changes in temperature measurements caused by noise and physiological motion.
METHODS:
Fourteen patients referred for cardiovascular magnetic resonance imaging underwent an extra sequence to test the temperature mapping stability during free-breathing acquisition. Phase images were acquired using a multi-slice, cardiac-triggered, single-shot echo planar imaging sequence. Temperature maps were calculated and displayed in real-time while the electrocardiogram (ECG) was recorded. The precision of temperature measurement was assessed by measuring the temporal standard deviation and temporal mean of consecutive temperature maps over a period of three minutes. The cardiac cycle was analyzed from ECG recordings to quantify the impact of arrhythmia events on the precision of temperature measurement. Finally, two retrospective strategies were tested to remove acquisition dynamics related either to arrhythmia events or sudden breathing motion.
RESULTS:
ECG synchronization allowed categorization of inter-beat intervals (RR) into distinct beat morphologies. Five patients were in stable sinus rhythm, while nine patients showed irregular RR intervals due to ectopic beats. An average temporal standard deviation of temperature of 1.6°C was observed in patients under sinus rhythm with a frame rate corresponding to the heart rate of the patient. The temporal standard deviation rose to 2.5°C in patients with arrhythmia. The retrospective rejection strategies increased the temperature precision measurement while maintaining a sufficient frame rate.
CONCLUSIONS:
Our results indicated that real-time cardiac MR thermometry shows good precision in patients under clinical conditions, even in the presence of arrhythmia. By providing real-time visualization of temperature distribution within the myocardium during RF delivery, MR thermometry could prevent insufficient or excessive heating and thus improve safety and efficacy.