CFD simulation of flow through heart: a perspective review

The heart is an organ which pumps blood around the body by contraction of muscular wall. There is a coupled system in the heart containing the motion of wall and the motion of blood fluid; both motions must be computed simultaneously, which make biological computational fluid dynamics (CFD) difficult. The wall of the heart is not rigid and hence proper boundary conditions are essential for CFD modelling. Fluid-wall interaction is very important for real CFD modelling. There are many assumptions for CFD simulation of the heart that make it far from a real model. A realistic fluid-structure interaction modelling the structure by the finite element method and the fluid flow by CFD use more realistic coupling algorithms. This type of method is very powerful to solve the complex properties of the cardiac structure and the sensitive interaction of fluid and structure. The final goal of heart modelling is to simulate the total heart function by integrating cardiac anatomy, electrical activation, mechanics, metabolism and fluid mechanics together, as in the computational framework.     

Estimation of independent and dependent components of non-invasive EMG using fast ICA: validation in recognising complex gestures

The identification of a number of active muscles during complex actions is the useful information to identify different gestures. Biosignals such as surface electromyogram (sEMG) are a result of the summation of electrical activity of a number of sources. The complexity of the anatomy and actions makes it difficult in identifying the number of active sources from the multiple channel recordings. This paper addresses two applications of independent component analysis (ICA) on sEMG: the first one is to evaluate the use of ICA for the separation of bioelectric signals when the number of active sources may not be known. The second application is to identify complex hand gestures using decomposed sEMG. The theoretical analysis and experimental results demonstrate that the ICA is suitable for the separation of myoelectric signals. The results identify the usage of ICA for identifying complex gestures.     

Estimation of independent and dependent components of non-invasive EMG using fast ICA: validation in recognising complex gestures

The identification of a number of active muscles during complex actions is the useful information to identify different gestures. Biosignals such as surface electromyogram (sEMG) are a result of the summation of electrical activity of a number of sources. The complexity of the anatomy and actions makes it difficult in identifying the number of active sources from the multiple channel recordings. This paper addresses two applications of independent component analysis (ICA) on sEMG: the first one is to evaluate the use of ICA for the separation of bioelectric signals when the number of active sources may not be known. The second application is to identify complex hand gestures using decomposed sEMG. The theoretical analysis and experimental results demonstrate that the ICA is suitable for the separation of myoelectric signals. The results identify the usage of ICA for identifying complex gestures.     

Structural and congenital heart disease interventions: the role of three-dimensional printing

Advances in catheter-based interventions in structural and congenital heart disease have mandated an increased demand for three-dimensional (3D) visualisation of complex cardiac anatomy. Despite progress in 3D imaging modalities, the pre- and periprocedural visualisation of spatial anatomy is relegated to two-dimensional flat screen representations. 3D printing is an evolving technology based on the concept of additive manufacturing, where computerised digital surface renders are converted into physical models. Printed models replicate complex structures in tangible forms that cardiovascular physicians and surgeons can use for education, preprocedural planning and device testing. In this review we discuss the different steps of the 3D printing process, which include image acquisition, segmentation, printing methods and materials. We also examine the expanded applications of 3D printing in the catheter-based treatment of adult patients with structural and congenital heart disease while highlighting the current limitations of this technology in terms of segmentation, model accuracy and dynamic capabilities. Furthermore, we provide information on the resources needed to establish a hospital-based 3D printing laboratory.     

Le compte des mouvements actifs du foetus: peut-il être utile.

In most cases a count of the active movements of the fetus by the mother is a good index of fetal activity. The information provided compares favourably with that furnished by analysis of the fetal heart rate and hormone levels in the mother''s plasma. Counting the fetal movements every day for 1 or 2 hours starting at the 24th to 26th week of pregnancy is a simple, inexpensive and noninvasive method that could be used as and screening test for fetal distress. More complex and costly investigations necessitating hospitalization could then be reserved for patients noting an abnormal count. However, this scheme demands intelligence and motivation of the mother, and one must expect a certain rate of refusal or dropout.     

Isolation of Fetal ECG Signals from Abdominal ECG Using Wavelet Analysis

ObjectiveMonitoring the heartbeat of the fetus during pregnancy is a vital part in determining their health. Current fetal heart monitoring techniques lack the accuracy in fetal heart rate monitoring and features acquisition, resulting in diagnostic medical issues. The demand for a reliable method of non-invasive fetal heart monitoring is of high importance.MethodElectrocardiogram (ECG) is a method of monitoring the electrical activity produced by the heart. The extraction of the fetal ECG (FECG) from the abdominal ECG (AECG) is challenging since both ECGs of the mother and the baby share similar frequency components, adding to the fact that the signals are corrupted by white noise. This paper presents a method of FECG extraction by eliminating all other signals using AECG. The algorithm is based on attenuating the maternal ECG (MECG) by filtering and wavelet analysis to find the locations of the FECG, and thus isolating them based on their locations. Two signals of AECG collected at different locations on the abdomens are used. The ECG data used contains MECG of a power of five to ten times that of the FECG.ResultsThe FECG signals were successfully isolated from the AECG using the proposed method through which the QRS complex of the heartbeat was conserved, and heart rate was calculated. The fetal heart rate was 135 bpm and the instantaneous heart rate was 131.58 bpm. The heart rate of the mother was at 90 bpm with an instantaneous heart rate of 81.9 bpm.ConclusionThe proposed method is promising for FECG extraction since it relies on filtering and wavelet analysis of two abdominal signals for the algorithm. The method implemented is easily adjusted based on the power levels of signals, giving it great ease of adaptation to changing signals in different biosignals applications.     

Comparison of m-mode echocardiographic left ventricular mass measured using digital and strip chart readings: The Atherosclerosis Risk in Communities (ARIC) study

In contrast with transthoracic echocardiography, transesophageal echocardiography provides a sure way to make the diagnosis of sinus venosus atrial septal defect; on the other hand this abnormality is more complex than that seen with the secundum atrial septal defect, and inexperienced operators may fail to recognize properly the defect. In front of a high reported sensitivity using transesophageal echocardiography, specificity is difficult to assess, due to possible underreporting of diagnostic errors. We describe a false positive diagnosis of sinus venosus atrial septal defect, in the setting of enlarged right chambers of the heart because of pressure overload. Modified anatomy of the heart, together with the presence of a prominent linear structure(probably Eustachian Valve) and an incomplete examination in this case made image interpretation very prone to misinterpretation. In this anatomical setting transesophageal longitudinal "bicaval" view may be sub-optimal for examining the atrial septum, potentially showing false images that need to be known for correct image interpretation. Nonetheless, a scan plane taken more accurately at the superior level would have demonstrated/excluded the pathognomonic feature of sinus venosus atrial septal defect in the high atrial septum, between the fatty limbus and the inferior aspect of the right pulmonary artery; moreover TEE allows morphological information about the posterior structures of the heart that need to be investigated in detail for a complete diagnosis.     

Medial canthal reconstruction using a medially based upper eyelid myocutaneous flap

Periorbital reconstruction following skin cancer ablation represents a challenging problem. A thorough understanding of the complex periorbital anatomy is necessary to preserve lid function and protect the ocular surface. The medial canthal region represents the most difficult periorbital zone to reconstruct. This area has a complex anatomy involving both the medial canthus itself and the lacrimal apparatus. The authors present their experience with a versatile technique for reconstruction of the medial canthal periorbital region, namely, a medially based upper eyelid myocutaneous flap. In the 10 patients in whom this procedure was used, there was one partial and no complete flap losses. The authors believe that the medially based upper lid myocutaneous flap offers an excellent solution to the difficult problem of medial canthal periorbital reconstruction.     

A new technique for the identification of respiratory sinus arrhythmia in utero

Fetal heart rate (FHR) monitoring forms the basis of routine fetal assessment, particularly short-term variability in the interbeat interval which can be difficult to interpret. Respiratory sinus arrhythmia (RSA), the change in heart rate in response to breathing, contributes to short-term variability, and the presence of RSA in utero may reflect the functional integrity of the central nervous system. This paper describes the use of Doppler ultrasound to derive the required measures of fetal heart rate and fetal breathing movements and spectral analysis to identify RSA. Cases are presented to illustrate the results obtained both in the presence and absence of RSA.     

颅内海绵窦脑膜瘤的临床研究进展

海绵窦脑膜瘤虽多为良性肿瘤,但由于其解剖位置的特殊性,往往可累及颈内动脉、Ⅲ~Ⅵ对颅神经甚至垂体等重要结构,表现出类似恶性肿瘤的生物学行为。由于其毗邻颅内重要结构,手术全切难度高。近年来,随着CT、MR等现代影像技术的发展及广泛应用,以及对海绵窦解剖的认识、显微外科和颅底外科技术的发展,海绵窦脑膜瘤在术前诊断、评估及手术治疗等方面已取得了长足进步。然而,由于此区解剖复杂,手术难度大,在治疗方法上还存在一定的争议。我们对海绵窦脑膜瘤目前诊断及治疗策略的进展进行简要概述。     

Transvenous pacing in complex post-operative congenital heart disease guided by angiography: A case report

Transvenous pacing in patients with postoperative complex congenital heart disease (CHD) can be challenging and pose technical challenges to lead placement because of the complex anatomy, distortions produced by the surgical procedures, and the altered relationship of cardiac chambers. We describe the utility of angiography for transvenous dual chamber pacemaker implantation in a post-operative complex congenital heart disease.     

Fatty acid and glucose oxidation by cultured rat heart cells

Monolayer cultures of fetal rat myocardial cells can be utilized to examine substrate preferences and interactions. The specific activity of glucose oxidation by myocardial cell cultures was high in sparse cultures but decreased with increased cell density. In contrast, palmitate oxidation was independent of initial cell density. Palmitate inhibited glucose oxidation by 50% in rat heart cultures. Glucose had only a slight sparing effect on palmitate oxidation. This suggests that fetal and newborn rat myocardial cells in culture preferentially oxidize palmitate similar to adult heart. The sparing effect of palmitate on glucose oxidation is accounted for by inhibition of the glycolytic-aerobic pathway and not by inhibition of the pentose phosphate pathway. Data on oxidation of ¹⁴C-pyruvate specifically labelled suggest that palmitate or a product of its oxidation such as acetyl-CoA may be acting directly to inhibit the pyruvate dehydrogenase complex. Palmitate oxidation per mg of cell protein was constant from 15 days gestational age to 2 days postnatal age. The observed differences between cultured cells and the intact heart may relate to decreased aerobic metabolism in monolayer cell culture and suggest that the increase in fatty acid oxidation observed in vivo is controlled by the oxygen environment of the cell. These studies show that heart cells in monolayer culture can be utilized to obtain metabolic information similar to an adult organ perfusion model.     

Ontogeny of pyruvate dehydrogenase complex and key enzymes involved in glycolysis and tricarboxylic acid cycle in rabbit fetal lung, heart, and liver

The metabolic pathways by which the glycogen is utilized by fetal tissues is not well established. In the present study the ontogeny of seven key enzymes involved in glycolysis and the tricarboxylic acid cycle has been established for rabbit fetal lung, heart, and liver. In the fetal lung the activities of phosphofructokinase, pyruvate kinase, lactic dehydrogenase, citrate synthase, and malate dehydrogenase increase from day 21 to 25. Thereafter the levels either drop to day 19 levels or do not change. The isocitrate dehydrogenase activity continues to increase from day 19 of gestation to maximum level on day 31 of gestation. In fetal heart the pattern of activity is similar, but in fetal liver most of the enzymes reach maximum levels earlier and, with the exception of pyruvate kinase, do not show a significant fall in activity near term. The pattern of development of pyruvate dehydrogenase complex is different; maximum activity is observed on day 27 in fetal lung and heart and on day 21 in fetal liver. These results indicate that all three fetal tissues can oxidize glucose. Also, the accumulation of glycogen, particularly in fetal lung, appears to ensure that at specific times during gestation adequate quantities of energy (ATP) and substrates, required for surfactant phospholipid synthesis, are available independent of maternal supply of glucose or during brief episodes of hypoxia.     

Quantifying the Interactions between Maternal and Fetal Heart Rates by Transfer Entropy

Evidence of the short term relationship between maternal and fetal heart rates has been found in previous studies. However there is still limited knowledge about underlying mechanisms and patterns of the coupling throughout gestation. In this study, Transfer Entropy (TE) was used to quantify directed interactions between maternal and fetal heart rates at various time delays and gestational ages. Experimental results using maternal and fetal electrocardiograms showed significant coupling for 63 out of 65 fetuses, by statistically validating against surrogate pairs. Analysis of TE showed a decrease in transfer of information from fetus to the mother with gestational age, alongside the maturation of the fetus. On the other hand, maternal to fetal TE was significantly greater in mid (26–31 weeks) and late (32–41 weeks) gestation compared to early (16–25 weeks) gestation (Mann Whitney Wilcoxon (MWW) p<0.05). TE further increased from mid to late, for the fetuses with RMSSD of fetal heart rate being larger than 4 msec in the late gestation. This difference was not observed for the fetuses with smaller RMSSD, which could be associated with the quiet sleep state. Delay in the information transfer from mother to fetus significantly decreased (p = 0.03) from mid to late gestation, implying a decrease in fetal response time. These changes occur concomitant with the maturation of the fetal sensory and autonomic nervous systems with advancing gestational age. The effect of maternal respiratory rate derived from maternal ECG was also investigated and no significant relationship was found between breathing rate and TE at any lag. In conclusion, the application of TE with delays revealed detailed information on the fetal-maternal heart rate coupling strength and latency throughout gestation, which could provide novel clinical markers of fetal development and well-being.     

Computer analysis of antepartum fetal heart rate: 1. Baseline determination

A consequent and reproducible determination of baseline is an essential prerequisite for objective interpretation of fetal heart rate. A fully automated off-line method of baseline determination has been developed and tested on 50 normal antepartum fetal heart rate recordings of two hours duration. The method is constructed around two functional units, a digital filter and a trim function, which interact in an iterative process. The results were evaluated in comparison with automated baseline determination according to Dawes and coworkers. A panel of 3 experts agreed that in 14 of the 50 recordings (28%), the new developed procedure resulted in a substantially better baseline fit. In the remaining 34 recordings (72%), baseline fit from both methods was judged as equivalent. The described procedure of baseline determination provides a solid base for automated detection of accelerations and decelerations in fetal heart rate recordings. It enables the study of the relation between the fetal heart rate pattern and fetal movements. Finally, it provides an objective tool for analysis of variables within the fetal heart rate with the highest predictive value with respect to fetal outcome.     

Is fetal heart rate monitoring sufficiently sensitive to detect changes during labour?

Although fetal monitoring is a common clinical procedure, there is little quantitative evidence that it can detect changes occurring during labour. We present quantitative data comparing the first and second stage of labour, from 21 labours resulting in a normal fetal outcome. A range of fetal heart rate variables was calculated from the output of a fetal heart rate monitor. Significant changes were detected in baseline fetal heart rate (P < 0.005), heart rate variability (P < 0.05), number of dips (P < 0.01).and their depth (P < 0.01). The results encourage confidence in the sensitivity of fetal monitoring for the detection of changes in a number of fetal heart rate variables during the course of labour.     

Transcatheter leadless permanent pacemaker in complex congenital heart disease with interrupted inferior vena cava: A challenging implantation

31 years lady with complete atrioventricular canal defect, large primum atrial septal defect (ASD), inlet ventricular septal defect (VSD) and Eisenmenger syndrome, presented with atrial flutter and complete heart block. She was not suitable for corrective cardiac surgery and not yet indicated for heart-lung transplantation. She was advised single chamber permanent pacemaker and eventually Micra VR transcatheter leadless pacemaker was finalised for her. Transcatheter leadless pacemaker was deployed in her RV septum despite some unforeseen technical problems. This patient had intrahepatic interruption of IVC with Azygous continuation draining into SVC but this altered venovascular course was detected only fluoroscopically midway during the pacemaker implantation procedure and this was not detected in the preprocedural transthoracic echocardiography. This abnormal venous course was clearly demonstrated in the cardiac CT which was performed only after completion of the pacemaker implantation procedure in this patient. The technical challenges encountered mainly were mostly during the manipulation of the 27F delivery catheter of Micra through this altered cardiovascular anatomy via transfemoral approach and also due to the presence of septal defects. Thus, transcatheter leadless permanent pacemaker was implanted successfully through transfemoral access in this complex congenital heart disease with interrupted IVC and azygous continuation. Besides transthoracic echocardiography, it may be better to perform transesophageal echocardiography or even preferably radiological imaging like cardiac CT or MRI prior to transcatheter leadless pacemaker implantation in patients with complex congenital heart disease to understand the cardiovascular anatomy and plan the procedure.     

Cardiac ultrasonography in structural abnormalities and arrhythmias. Recognition and treatment.

Fetal cardiac ultrasonography has become an important tool in the evaluation of fetuses at risk for cardiac anomalies. It can both guide prenatal treatment and assist the management and timing of delivery. We recommend that a fetal echocardiogram be done when there is a family history of congenital heart disease; maternal disease that may affect the fetus; a history of maternal drug use, either therapeutic or illegal; evidence of other fetal abnormalities; or evidence of fetal hydrops. The optimal timing of evaluation is 18 to 22 weeks'' gestation. An entire range of structural cardiac defects can be visualized prenatally, including atrioventricular septal defect, ventricular septal defect, cardiomyopathy, ventricular outlet obstruction, and complex cardiac defects. The outcome for a fetus with a recognized abnormality is unfavourable, with less than 50% surviving the neonatal period. Fetal cardiac arrhythmias are also a common occurrence, 15% in the series described here. Premature atrial or ventricular contractions are most commonly seen and usually require no treatment. Supraventricular tachycardia can result in hydrops and require in utero treatment to prevent fetal demise. Complete heart block, particularly in association with structural heart disease, has a poor prognosis for fetal survival.