Deep learning segmentation and quantification method for assessing epicardial adipose tissue in CT calcium score scans

Epicardial adipose tissue volume (EAT) has been linked to coronary artery disease and the risk of major adverse cardiac events. As manual quantification of EAT is time-consuming, requires specialized training, and is prone to human error, we developed a deep learning method (DeepFat) for the automatic assessment of EAT on non-contrast low-dose CT calcium score images. Our DeepFat intuitively segmented the tissue enclosed by the pericardial sac on axial slices, using two preprocessing steps. First, we applied a HU-attention-window with a window/level 350/40-HU to draw attention to the sac and reduce numerical errors. Second, we applied a novel look ahead slab-of-slices with bisection ("bisect") in which we split the heart into halves and sequenced the lower half from bottom-to-middle and the upper half from top-to-middle, thereby presenting an always increasing curvature of the sac to the network. EAT volume was obtained by thresholding voxels within the sac in the fat window (- 190/- 30-HU). Compared to manual segmentation, our algorithm gave excellent results with volume Dice = 88.52% ± 3.3, slice Dice = 87.70% ± 7.5, EAT error = 0.5% ± 8.1, and R = 98.52% (p < 0.001). HU-attention-window and bisect improved Dice volume scores by 0.49% and 3.2% absolute, respectively. Variability between analysts was comparable to variability with DeepFat. Results compared favorably to those of previous publications.

Hemopericardium in the acute clinical setting: Are we ready for a tailored management approach on the basis of MDCT findings?

The clinical spectrum of pericardial effusions varies from innocuous serous fluid to life-threatening hemopericardium. A misdiagnosis may be made by similar clinical presentation of acute chest pain/hypotension. Echocardiography is the first-line test for diagnosis of pericardial effusion and its etiology, but sometimes there are different drawbacks to the correct cardiovascular ultrasound diagnosis. Radiologists are reporting an increasing amount of thoracic Multidetector CT examinations at the emergency department. Multidetector CT has now become an established and complementary method for cardiac imaging, and diseases of the pericardium can now be quickly identified with increasing certainty. The aim of this review is to discuss the hemopericardium key Multidetector CT features in acute clinical setting which indicate the need to proceed with predominantly medical or surgical treatment, however, being able to identify forms of bleeding pericardial effusion for which only "a watch and wait strategy" and/or deferred treatment is indicated. In the emergency care setting, radiologists must be aware of different findings of hemopericardium in order to address a tailored and timely management approach.

Percutaneous Epicardial Ablation of Atrial Fibrillation

The observations afforded by epicardial mapping have not only increased the appreciation of distinct epicardial structures in the left atrium but also underscore the need to address the substrate transmurally. Although epicardial access and ablation have attendant risks, comparative studies with hybrid surgical approaches are lacking. In the search to find unifying mechanisms of atrial fibrillation, a conceptual shift that emphasizes the substrate in 3 dimensions, with the epicardium distinct from the endocardium, holds promise for future investigation and evolving therapeutic tools.

Anatomically correct assessment of the orientation of the cardiomyocytes using diffusion tensor imaging

Diffusion tensor imaging has been used for assessing the orientation of cardiac myocytes for decades. Striking methodological differences exist between studies when quantifying these orientations. This limits the comparability between studies, and impedes collaboration and the drawing of appropriate physiological conclusions. We have sought to elucidate these differences, permitting us to propose a standardised "tool set" that might better establish consensus in future studies. We fixed hearts from seven 25 kg pigs in formalin, and scanned them using diffusion tensor imaging. Using various angle definitions as found in literature, we assessed the orientations of cardiomyocytes, comparing them in terms of helical and intrusion angles, along with the orientation of their aggregations. The difference between assessment of the helical angle with and without relation to the epicardial curvature was 25.2° (SD: 7.9) at the base, 5.8° (1.9) at the equatorial level, and 28.0° (7.0) at the apex, ANOVA P = 0.001. In comparable fashion, the intrusion angle differed by 25.9° (12.9), 7.6° (0.98) and 17.5° (4.7), P = 0.01, and the angle of the aggregates (E3-angle) differed by 25.0° (13.5) at the base, 9.4° (1.7) at the equator, and 23.1° (6.2) apically, P = 0.003. When assessing 14 definitions used in literature to calculate the orientation of aggregates, only 4 rendered identical results. The findings show that any attempt to use projection of eigenvectors introduces considerable bias. The epicardial curvature of the ventricular cone needs to be taken into account when seeking to provide accurate quantification of the orientation of the aggregated cardiomyocytes, especially in the apical and basal regions. This means that projection of eigenvectors should be avoided prior to quantifying myocyte orientation, especially when assessing radial orientation. Based on our results, we suggest appropriate methods for valid assessment of myocyte orientation using diffusion tensor imaging.

Structure and Rheological Properties of Bovine Aortic Heart Valve and Pericardium Tissue: Implications in Bioprosthetic and Tissue-Engineered Heart Valves

Heart valve (HV) diseases are among the leading causes of cardiac failure and deaths. Of the various HV diseases, damaged HV leaflets are among the primary culprits. In many cases, impaired HV restoration is not always possible, and the replacement of valves becomes necessary. Bioprosthetic HVs have been used for the replacement of the diseased valves, which is obtained from the sources of bovine and porcine origin, while tissue-engineered heart valves (TEHV) have emerged as a promising future solution. The bioprosthetic valves are prone to become calcified, and thus they last for only ten to fifteen years. The adequate understanding of the correlations between the biomechanics and rheological properties of native HV tissues can enable us to improve the durability of the bioprosthetic HV as well as help in the development of tissue-engineered heart valves (TEHV). In this study, the structural and rheological properties of native bovine aortic HV and pericardium tissues were investigated. The microstructures of the tissues were investigated using scanning electron microscopy, while the rheological properties were studied using oscillatory shear measurement and creep test. The reported results provide significant insights into the correlations between the microstructure and viscoelastic properties of the bovine aortic HV and pericardium tissues.

Association between epicardial fat thickness and cognitive function in elderly. A preliminary study

BACKGROUND

Recent studies suggested that the visceral fat could exert a predictive role in the pathogenesis of dementia. The aims of the present study were to evaluate: i) possible differences between groups with different epicardial adipose tissue (EAT) thickness on the included variables; ii) the possible predictive role of the EAT levels on cognitive functioning.

METHODS

65 community-dwelling subjects were enrolled and divided into two groups: EAT < 7 mm (n = 36); EAT > 7 mm (n = 29). The metabolic profile was assessed through the evaluation of the biochemical parameters whereas the EAT thickness was measured through the transthoracic echocardiography. The Mini Mental State Examination (MMSE) was also administered.

RESULTS

The two EAT groups reported several significant differences, included on the MMSE scores. The multiple linear regression analysis showed that the EAT thickness levels and the hypertension had a predictive effect on the MMSE scores.

CONCLUSIONS

These preliminary findings support the association between EAT thickness levels and cognitive impairment.

Microstructural alterations owing to handling of bovine pericardium to manufacture bioprosthetic heart valves: A potential risk for cusp dehiscence

INTRODUCTION

Cross-linking and anti-calcification of prosthetic heart valves have been continuously improved to prevent degeneration and calcification. However, non-calcific structural deteriorations such as cuspal dehiscences along the stent still require further analysis.

MATERIAL AND METHOD

Based upon the previous analysis of an explanted valve after 7 years, a fresh commercial aortic valve was embedded in poly(methyl methacrylate) (PMMA) and cut into slices to ensure the detailed observation of the assembly and material structures. A pericardial patch embossed to provide the adequate shape of the cusps was investigated after paraffin embedding and appropriate staining. The microstructural damages that occurred during manufacturing process were identified and evaluated by light microscopy, polarized microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM).

RESULTS

The wavy collagen bundles, the key structure of the pericardium patch, were damaged to a great extent at suture sites along the stent and in the compressed areas around the stent post. The fixation of the embossed pericardium patch along the plots of the stent aggravated the microstructural modifications. The damages mainly appeared as the elimination of collagen bundle waviness and delamination between the bundles.

CONCLUSION

Considering the modes of failure of the explant, the damages to the collagen bundles may identify the vulnerable sites that play an important role in the cusp dehiscence of heart valve implants. Such information is important to the manufacturers. Recommendations to prevent in vivo cusp dehiscence can therefore be formulated.

Automated quantification of epicardial adipose tissue in cardiac magnetic resonance imaging

Cardiovascular disease is one of the leading causes of death worldwide. Epicardial adipose tissue (EAT) has emerged as an independent predictor of high cardiometabolic risk. Cardiovascular MRI has proven to be a feasible and reproducible method to assess EAT quantitatively. We present a novel approach for the automated quantification of EAT using "a priori" anatomical information. We extracted a region of interest (ROI) in the end-diastolic heart phase followed by a GVF-snake algorithm to smooth it. For the EAT and endocardial boundary detection, a Law's texture filter is applied. Left and right ventricle are localized using spatial prior information. Then, thresholding is applied to quantify the cardiac muscle. For the EAT, it is differentiated from the paracardial fat by K-cosine curvature analysis. Results for 10 morbidly obese patients show no significant differences between manual and automatic quantification with a remarkable time and effort saving between them.

[Numerical Simulation of Propagation of Electric Excitation in the Heart Wall Taking into Account Its Fibrous-Laminar Structure]

The propagation of excitation wave in the inhomogeneous anisotropic finite element model of cardiac muscle is investigated. In this model, the inhomogeneity stands for the rotation of anisotropy axes through the wall thickness and results from a fibrous-laminar structure of the cardiac muscle tissue. Conductivity of the cardiac muscle is described using a monodomain model and the Aliev-Panfilov equations are used as the relationships between the transmembrane current and transmembrane potential. Numerical simulation is performed by applying the splitting algorithm, in which the partial differential solution to the nonlinear boundary value problem is reduced to a sequence of simple ordinary differential equations and linear partial differential equations. The simulation is carried out for a rectangular block of the cardiac tissue, the minimal size of which is considered to be the thickness of the heart wall. Two types of distribution of the fiber orientation angle are discussed. The first case corresponds 'to the left ventricle of a dog. The endocardium and epicardium fibers are generally oriented in the meridional direction. The angle of fiber orientation varies smoothly through the wall thickness making a half-turn. A circular layer, in which the fibers are oriented in the circumferential direction locates deep in the cardiac wall. The results of calculations show that for this case the wave form strongly depends on a place of initial excitation. For the endocardial and epicardial initial excitation one can see the earlier wave front propagation in the endocardium and epicardium, respectively. At the intramural initial excitation the simultaneous wave front propagation in the endocardium and epicardium occurs, but there is a wave front lag in the middle of the wall. The second case refers to the right ventricle of a swine, in which the endocardium and epicardium fibers are typically oriented in the circumferential direction, whereas the subepicardium fibers undergo an abrupt change in the angle of orientation. For this case the dependence of the wave front on the location of initial excitation is weak. One can see the earlier wave front propagation in the middle of the wall. However, the wave front formation rate is different: with highest velocity for intramural initial excitation and with lowest one during excitation on the endocardial surface.

Optimal iodine staining of cardiac tissue for X-ray computed tomography

X-ray computed tomography (XCT) has been shown to be an effective imaging technique for a variety of materials. Due to the relatively low differential attenuation of X-rays in biological tissue, a high density contrast agent is often required to obtain optimal contrast. The contrast agent, iodine potassium iodide (), has been used in several biological studies to augment the use of XCT scanning. Recently was used in XCT scans of animal hearts to study cardiac structure and to generate 3D anatomical computer models. However, to date there has been no thorough study into the optimal use of as a contrast agent in cardiac muscle with respect to the staining times required, which has been shown to impact significantly upon the quality of results. In this study we address this issue by systematically scanning samples at various stages of the staining process. To achieve this, mouse hearts were stained for up to 58 hours and scanned at regular intervals of 6–7 hours throughout this process. Optimal staining was found to depend upon the thickness of the tissue; a simple empirical exponential relationship was derived to allow calculation of the required staining time for cardiac samples of an arbitrary size.

Three-dimensional microvasculature in rat and human hearts using a non-injection Ca2+-ATPase method on thick and ultra-thick sections

Currently there are no methods available for staining rat and human myocardial microvasculature on thick sections that would allow for specific staining and differentiation of arterioles, venules, and capillaries. A non-injection technique is described that allows for labeling of the microvascular bed (MVB) in formalin-fixed pieces of the myocardium from humans and the white rat Rattus norvegicus, as well as human full-mount pericardium. Vessel staining is based on the activity of phosphatases (ATPases) and the precipitation of the released phosphate with calcium ions at high pH (pH 10.5-11.5). The resulting precipitate subsequently is converted to black or brown lead sulfide. The specificity of this reaction to vessels of the MVB allows arterioles, venules, capillaries, and pre- and postcapillaries to be clearly visualized in thick (60-100 µm) and ultra-thick (300-500 µm) sections against an unstained background of muscle and connective tissue. In addition, smooth muscle cells of arterioles are also stained allowing for differentiation between arteriolar and venular beds. These observations have not been reported in rat or human myocardium using other methods. This procedure should benefit studies of coronary microcirculation in experimental and pathological conditions, as well as in pharmacological investigations.

Electrical wave propagation in an anisotropic model of the left ventricle based on analytical description of cardiac architecture

We develop a numerical approach based on our recent analytical model of fiber structure in the left ventricle of the human heart. A special curvilinear coordinate system is proposed to analytically include realistic ventricular shape and myofiber directions. With this anatomical model, electrophysiological simulations can be performed on a rectangular coordinate grid. We apply our method to study the effect of fiber rotation and electrical anisotropy of cardiac tissue (i.e., the ratio of the conductivity coefficients along and across the myocardial fibers) on wave propagation using the ten Tusscher–Panfilov (2006) ionic model for human ventricular cells. We show that fiber rotation increases the speed of cardiac activation and attenuates the effects of anisotropy. Our results show that the fiber rotation in the heart is an important factor underlying cardiac excitation. We also study scroll wave dynamics in our model and show the drift of a scroll wave filament whose velocity depends non-monotonically on the fiber rotation angle; the period of scroll wave rotation decreases with an increase of the fiber rotation angle; an increase in anisotropy may cause the breakup of a scroll wave, similar to the mother rotor mechanism of ventricular fibrillation.

Epicardial adipose tissue in endocrine and metabolic diseases

Epicardial adipose tissue has recently emerged as new risk factor and active player in metabolic and cardiovascular diseases. Albeit its physiological and pathological roles are not completely understood, a body of evidence indicates that epicardial adipose tissue is a fat depot with peculiar and unique features. Epicardial fat is able to synthesize, produce, and secrete bioactive molecules which are then transported into the adjacent myocardium through vasocrine and/or paracrine pathways. Based on these evidences, epicardial adipose tissue can be considered an endocrine organ. Epicardial fat is also thought to provide direct heating to the myocardium and protect the heart during unfavorable hemodynamic conditions, such as ischemia or hypoxia. Epicardial fat has been suggested to play an independent role in the development and progression of obesity- and diabetes-related cardiac abnormalities. Clinically, the thickness of epicardial fat can be easily and accurately measured. Epicardial fat thickness can serve as marker of visceral adiposity and visceral fat changes during weight loss interventions and treatments with drugs targeting the fat. The potential of modulating the epicardial fat with targeted pharmacological agents can open new avenues in the pharmacotherapy of endocrine and metabolic diseases. This review article will provide Endocrine's reader with a focus on epicardial adipose tissue in endocrinology. Novel, established, but also speculative findings on epicardial fat will be discussed from the unexplored perspective of both clinical and basic Endocrinologist.

Distribution and morphology of calcitonin gene-related peptide and substance P immunoreactive axons in the whole-mount atria of mice

The murine model has been used to investigate the role of cardiac sensory axons in various disease states. However, the distribution and morphological structures of cardiac nociceptive axons in normal murine tissues have not yet been well characterized. In this study, whole-mount atria from FVB mice were processed with calcitonin gene-related peptide (CGRP) and substance P (SP) primary antibodies followed by secondary antibodies, and then examined using confocal microscopy. We found: 1) Large CGRP-IR axon bundles entered the atria with the major veins, and these large bundles bifurcated into small bundles and single axons that formed terminal end-nets and free endings in the epicardium. Varicose CGRP-IR axons had close contacts with muscle fibers, and some CGRP-IR axons formed varicosities around principle neurons (PNs) within intrinsic cardiac ganglia (ICGs). 2) SP-IR axons also were found in the same regions of the atria, attached to veins, and within cardiac ganglia. Similar to CGRP-IR axons, these SP-IR axons formed terminal end-nets and free endings in the atrial epicardium and myocardium. Within ICGs, SP-IR axons formed varicose endings around PNs. However, SP-IR nerve fibers were less abundant than CGRP-IR fibers in the atria. 3) None of the PNs were CGRP-IR or SP-IR. 4) CGRP-IR and SP-IR often colocalized in terminal varicosities around PNs. Collectively, our data document the distribution pattern and morphology of CGRP-IR and SP-IR axons and terminals in different regions of the atria. This knowledge provides useful information for CGRP-IR and SP-IR axons that can be referred to in future studies of pathological remodeling.

Determinants of intrathoracic adipose tissue volume and associations with cardiovascular disease risk factors in Amish

BACKGROUND AND AIM

Hypothesizing that intrathoracic fat might exert local effects on the coronary vasculature, we assessed the association of intrathoracic fat volume and its two subcomponents with coronary artery calcification (CAC) in 909 relatively healthy Amish adults.

METHODS AND RESULTS

Intrathoracic fat, which is comprised of fat between the surface of the heart and the visceral epicardium (epicardial fat) and fat around the heart but outside of the fibrous pericardium (pericardial fat), was measured from electron beam CT scans. We examined the association between intrathoracic fat volume and cardiovascular disease risk factors in multivariate regression model. Fat volume in the epicardial and pericardial compartments were highly correlated with each other and with body mass index. Neither CAC extent nor CAC presence (Agatston score > 0) was associated with increased intrathoracic fat volume in sex-stratified models adjusting for age (p > 0.10). Intrathoracic fat volume was significantly correlated with higher systolic/diastolic blood pressure, pulse pressure, fasting glucose, insulin, triglyceride and lower high-density lipoprotein cholesterol in sex-stratified models adjusting for age (p < 0.05). However, associations were attenuated after further adjustment for body mass index.

CONCLUSIONS

These data do not provide support for a significant role for intrathoracic fat in the development of CAC.

Cardiovascular magnetic resonance of total and atrial pericardial adipose tissue: a validation study and development of a 3 dimensional pericardial adipose tissue model

BACKGROUND

Recently pericardial adipose tissue (PAT) has been shown to be an independent predictor of atrial fibrillation (AF). Atrial PAT may influence underlying atrial musculature creating a substrate for AF. This study sought to validate the assessment of total and atrial PAT by standard cardiovascular magnetic resonance (CMR) measures and describe and validate a three dimensional atrial PAT model.

METHODS

10 merino cross sheep underwent CMR using a 1.5 Tesla system (Siemens, Sonata, Erlangen, Germany). Atrial and ventricular short axis (SA) images were acquired, using ECG -gated steady state free precession sequences. In order to quantify total volume of adipose tissue, a three dimensional model was constructed from consecutive end-diastolic images using semi-automated software. Regions of adipose tissue were marked in each slice followed by linear interpolation of pixel intensities in spaces between consecutive image slices. Total volume of adipose tissue was calculated as a total volume of the three dimensional model and the mass estimated from volume measurements. The sheep were euthanized and pericardial adipose tissue was removed and weighed for comparison to the corresponding CMR measurements.

RESULTS

All CMR adipose tissue estimates significantly correlated with autopsy measurements (ICC > 0.80; p < 0.03). Intra- observer reliability in CMR measures was high, with 95% levels of agreement within 5.5% (ICC = 0.995) for total fat mass and its individual atrial (95% CI ± 8.3%, ICC = 0.993) and ventricular components (95% CI ± 6.6%, ICC = 0.989). Inter- observer 95% limits of agreement were within ± 10.7% (ICC = 0.979), 7.4% (ICC = 0.991) and 7.2% (ICC = 0.991) for atrial, ventricular and total pericardial adipose tissue, respectively.

CONCLUSION

This study validates the use of a semi-automated three dimensional atrial PAT model utilizing standard (clinical) CMR sequences for accurate and reproducible assessment of atrial PAT. The measurement of local cardiac fat stores via this methodology could provide a sensitive tool to examine the regional effect of fat deposition on atrial substrate which potentially may influence AF ablation strategies in obese patients.

Cardiac right ventricular segmentation via point correspondence

This study presents an approach to the segmentation of the right ventricle (RV) from a sequence of cardiac magnetic resonance (MR) images. Automatic delineation of the RV is difficult because of its complex morphology, thin and ill-defined borders, and the photometric similarities between the connected cardiac regions such as papillary muscles and heart wall. Further, geometric/photometric models are hard to build from a finite training set because of the significant differences in size, shape, and intensity between subjects. In this study, we propose to use a non-rigid registration method developed recently to obtain the point correspondence in a sequence of cine MR images. Given the segmentation on the first frame, the proposed method segments both endocardial and epicardial borders of the RV using the obtained point correspondence, and relaxes the need of a training set. The proposed method is evaluated quantitatively on common data set by comparison with manual segmentation, which demonstrated competitive results in comparison with recent methods.

The Popeye domain containing 2 (popdc2) gene in zebrafish is required for heart and skeletal muscle development

The Popeye domain containing (Popdc) genes encode a family of transmembrane proteins with an evolutionary conserved Popeye domain. These genes are abundantly expressed in striated muscle tissue, however their function is not well understood. In this study we have investigated the role of the popdc2 gene in zebrafish. Popdc2 transcripts were detected in the embryonic myocardium and transiently in the craniofacial and tail musculature. Morpholino oligonucleotide-mediated knockdown of popdc2 resulted in aberrant development of skeletal muscle and heart. Muscle segments in the trunk were irregularly shaped and craniofacial muscles were severely reduced or even missing. In the heart, pericardial edema was prevalent in the morphants and heart chambers were elongated and looping was abnormal. These pathologies in muscle and heart were alleviated after reducing the morpholino concentration. However the heart still was abnormal displaying cardiac arrhythmia at later stages of development. Optical recordings of cardiac contractility revealed irregular ventricular contractions with a 2:1, or 3:1 atrial/ventricular conduction ratio, which caused a significant reduction in heart frequency. Recordings of calcium transients with high spatiotemporal resolution using a transgenic calcium indicator line (Tg(cmlc2:gCaMP)(s878)) and SPIM microscopy confirmed the presence of a severe arrhythmia phenotype. Our results identify popdc2 as a gene important for striated muscle differentiation and cardiac morphogenesis. In addition it is required for the development of the cardiac conduction system.

Concomitant evaluation of flow-mediated vasodilation and epicardial fat thickness in idiopathic deep venous thrombosis

Flow mediated vasodilation (FMD) evaluates the endothelium-dependent vasodilation, is a reliable marker of arterial endothelial dysfunction and is related to coronary artery disease. Visceral fat predicts an unfavorable cardiovascular and metabolic risk profile in humans and echocardiographic assessment of epicardial fat (EF) is a reliable marker of visceral adiposity. We measured the FMD and EF thickness in 77 subjects, 38 without idiopathic deep vein thrombosis (DVT) (mean age 65.95 ± 16.29 years) and 39 with idiopathic DVT (mean age 65.49 ± 17.22 years). The purpose of this work is to investigate the presence of statistical association between FMD and DVT and between EF thickness and DVT. Furthermore, to account for possible atherosclerosis risk factor unbalances, comparison between FMD and DVT (and between EF and DVT) was assessed using a multivariate logistic regression model which included the following covariates: FMD, EF, age, sex, smoking and the presence of obesity. Subjects without DVT showed significant lower values of EF thickness (9.07 ± 1.89 mm vs 12.32 ± 1.73 mm, p=0.005) and borderline-significant greater values of FMD (9.01 ± 2.77 percent vs 7.47 ± 5.37 percent, p=0.058) as compared to those with DVT. In conclusion, the data presented indicate that subjects affected by spontaneous deep vein thrombosis may have an impaired endothelium-dependent vasodilation, a marker of arterial endothelial dysfunction related to coronary artery disease, and an increased epicardial adipose tissue, a marker of cardiometabolic risk.

Simultaneous optical mapping of transmembrane potential and wall motion in isolated, perfused whole hearts

Optical mapping of cardiac propagation has traditionally been hampered by motion artifact, chiefly due to changes in photodetector-to-tissue registration as the heart moves. We have developed an optical mapping technique to simultaneously record electrical waves and mechanical contraction in isolated hearts. This allows removal of motion artifact from transmembrane potential (V(m)) recordings without the use of electromechanical uncoupling agents and allows the interplay of electrical and mechanical events to be studied at the whole organ level. Hearts are stained with the voltage-sensitive dye di-4-ANEPPS and ring-shaped markers are attached to the epicardium. Fluorescence, elicited on alternate frames by 450 and 505 nm light-emitting diodes, is recorded at 700 frames∕ per second by a camera fitted with a 605 ± 25 nm emission filter. Marker positions are tracked in software. A signal, consisting of the temporally interlaced 450 and 505 nm fluorescence, is collected from the pixels enclosed by each moving ring. After deinterlacing, the 505 nm signal consists of V(m) with motion artifact, while the 450 nm signal is minimally voltage-sensitive and contains primarily artifacts. The ratio of the two signals estimates V(m). Deformation of the tissue enclosed by each set of 3 rings is quantified using homogeneous finite strain.

Ethnic differences in the relationship between pericardial adipose tissue and coronary artery calcified plaque: African-American-diabetes heart study

BACKGROUND

Calcified atherosclerotic plaque (CP) is less prevalent and less severe in African-Americans (AA), relative to European Americans (EA). Because pericardial adipose tissue (PAT) is associated with CP in the neighboring coronary arteries, we explored ethnic-specific relationships between PAT and CP.

METHODS

PAT volume and coronary and aortic CP were measured in 561 EA and 575 AA subjects with type 2 diabetes using single and multidetector computed tomography. Generalized estimating equations with exchangeable correlation and the sandwich estimator of the variance were used to test for associations between PAT and CP.

RESULTS

Mean (sd) ages of AA and EA participants were 56.7 (9.5) and 62.0 (8.9) yr, respectively; diabetes duration was 10.5 (8.1) and 10.1 (7.3) yr; and PAT volume was 86.9 (38.6) and 131.7 (55.3) cm3/45 mm. In AA and EA participants, respectively, mean (sd) coronary CP mass scores were 803 (1,889) and 1,465 (2,847) mg calcium; and aortic CP, 5,407 (10,651) and 10,090 (15,087) mg calcium. Adjusting for age, gender, body mass index, blood pressure, height, smoking, lipid-lowering medications, C-reactive protein, albuminuria, high-density lipoprotein-cholesterol, and triglycerides, parameter estimates for the relationship between PAT and log(coronary CP+1) were 0.012 in AA (P<0.0001) and 0.003 (P=0.24) in EA, with a significant ethnic difference (P=0.019). No significant relationships or ethnic differences were observed between PAT and aortic CP (P=0.24, fully adjusted model).

CONCLUSIONS

Pericardial adiposity is strongly associated with coronary atherosclerosis in AA with type 2 diabetes. Novel cardiovascular disease risk factors such as PAT may contribute to ethnic disparities in susceptibility to development of coronary atherosclerosis.

Effect of Ischemic Preconditioning Based on Different Epicardial Branching Patterns of the Left Coronary Artery in the Rabbit Heart

The aim of this study was to characterize the effect of increasing numbers of preconditioning cycles on the different branching patterns (bifurcation/trifurcation) of the coronary artery in the rabbit heart. Fifty-six NZW rabbits were assigned to a bifurcation group and subjected to 0, 1, 3, 5, or 7 (B0, B1, B3, B5, or B7 subgroup, respectively) cycles of preconditioning (PC) (5 min of regional ischemia plus 10 min of reperfusion/cycle) and this was followed by 45 min of sustained ischemia and 72 h of reperfusion; 16 rabbits were assigned to a trifurcation group and subjected to 0, 1, 3, or 5 (T0, T1, T3, or T5 subgroup, respectively) cycles of PC. The ratio of necrotic zone (NZ) to ischemic zone (IZ) was calculated. The bifurcation group showed higher mortality (28.6%) than the trifurcation group (0%). The volume of the ischemic zone (expressed as a percentage of volume of the left ventricle) and the volume of the necrotic zone were larger in the bifurcation group than in the trifurcation group. The ratio of the necrotic zone to the ischemic zone was significantly lower in the B5 and B7 subgroups than in the B0, B1, and B3 subgroups. In the trifurcation group, the ratio of the necrotic zone to the ischemic zone showed a diminishing tendency in the subgroups as the PC cycle number increased, but without statistical significance. Thus, in the trifurcation pattern of the rabbit coronary artery there could be little effect on preconditioning, but in the bifurcation pattern the number of preconditioning is recommended to be 5 to 7 cycles. In this regard, different branching patterns of the epicardial branching of the rabbit coronary artery should be considered when interpreting experimental results on ischemic preconditioning.

Validation of cardiovascular magnetic resonance assessment of pericardial adipose tissue volume

BACKGROUND

Pericardial adipose tissue (PAT) has been shown to be an independent predictor of coronary artery disease. To date its assessment has been restricted to the use of surrogate echocardiographic indices such as measurement of epicardial fat thickness over the right ventricular free wall, which have limitations. Cardiovascular magnetic resonance (CMR) offers the potential to non-invasively assess total PAT, however like other imaging modalities, CMR has not yet been validated for this purpose. Thus, we sought to describe a novel technique for assessing total PAT with validation in an ovine model.

METHODS

11 merino sheep were studied. A standard clinical series of ventricular short axis CMR images (1.5T Siemens Sonata) were obtained during mechanical ventilation breath-holds. Beginning at the mitral annulus, consecutive end-diastolic ventricular images were used to determine the area and volume of epicardial, paracardial and pericardial adipose tissue. In addition adipose thickness was measured at the right ventricular free wall. Following euthanasia, the paracardial adipose tissue was removed from the ventricle and weighed to allow comparison with corresponding CMR measurements.

RESULTS

There was a strong correlation between CMR-derived paracardial adipose tissue volume and ex vivo paracardial mass (R2 = 0.89, p < 0.001). In contrast, CMR measurements of corresponding RV free wall paracardial adipose thickness did not correlate with ex vivo paracardial mass (R2 = 0.003, p = 0.878).

CONCLUSION

In this ovine model, CMR-derived paracardial adipose tissue volume, but not the corresponding and conventional measure of paracardial adipose thickness over the RV free wall, accurately reflected paracardial adipose tissue mass. This study validates for the first time, the use of clinically utilised CMR sequences for the accurate and reproducible assessment of pericardial adiposity. Furthermore this non-invasive modality does not use ionising radiation and therefore is ideally suited for future studies of PAT and its role in cardiovascular risk prediction and disease in clinical practice.

Epicardial catheter ablation of atrial fibrillation

Catheter ablation for atrial fibrillation, while superior to medical therapy alone, carries significant risk of complications and limited efficacy. Surgical therapy for atrial fibrillation, including the maze procedure, seems to be more effective but is also more invasive than percutaneous approaches. In this review, we outline the rationale for a percutaneous catheter-based epicardial ablation strategy. Operators considering such a procedure should have a detailed understanding of the anatomy of the pericardial space, which is reviewed in this manuscript. Also, technology used in epicardial ablation and special challenges of epicardial ablation are discussed. Finally, some preliminary work on epicardial ablation of atrial fibrillation is reviewed before concluding with some possibilities for future research in the area.

Epicardial fat thickness: relationship with plasma visfatin and plasminogen activator inhibitor-1 levels in visceral obesity

BACKGROUND AND AIM

Epicardial fat (EF), a true visceral adipose tissue (VAT) deposited around the heart, is considered as possible cardiovascular risk indicator, in view of its ability to produce and release several inflammatory adipo-cytokines. It is still not known whether increased cardiac adiposity is related to increased inflammatory adipo-cytokines in obesity. The aim of this study was to evaluate whether echocardiographic EF thickness, an indicator of cardiac adiposity, is related to circulating levels of inflammatory adipo-cytokines such as visfatin and plasminogen activator inhibitor-1 (PAI-1) in visceral obesity.

METHODS AND RESULTS

EF thickness (measured by echocardiography), visfatin, PAI-1 antigen and some inflammatory markers were studied in 42 women, 27 of them severely obese (OB) (BMI 43.5+/-4.8 kg/m(2)) but with no apparent complications, and 15 normal-weight controls. Abdominal VAT in the OB was assessed by computed tomography. OB had thicker EF and higher visfatin and PAI-1 antigen concentrations than controls (P<0.0001). EF thickness, log-visfatin and log-PAI-1 antigen concentrations directly correlated with VAT (P<0.0001). Log-visfatin and log-PAI-1 antigen were correlated with EF thickness even after adjusting for indices of fat distribution (P<0.01 and P<0.001 respectively). Moreover, when dividing OB on the basis of median EF thickness, women with greater EF thickness had more VAT and higher adipo-cytokine concentrations and inflammatory markers.

CONCLUSIONS

This study suggests that EF thickness, an indicator of cardiac adiposity, may be significantly related to inflammatory adipo-cytokines in visceral-obese patients. This suggests EF might be used as an easy and reliable marker of visceral adiposity and inflammation and as a cardiovascular risk indicator.

MR imaging of the pericardium

Imaging of the pericardium requires understanding of anatomy and the normal and abnormal physiology of the pericardium. MR imaging is well-suited for answering clinical questions regarding suspected pericardial disease. Pericardial diseases that may be effectively imaged with MR imaging include pericarditis, pericardial effusion, cardiac-pericardial tamponade, constrictive pericarditis, pericardial cysts, absence of the pericardium, and pericardial masses. Although benign and malignant primary tumors of the pericardium may be occasionally encountered, the most common etiology of a pericardial mass is metastatic disease.

Combination of short- and longaxis MR image sequences for the 3D segmentation of the left ventricle

Segmentation of the left ventricle (LV) is required to quantify LV remodeling after myocardial infarction. Therefore spatiotemporal Cine MR sequences including longaxis and shortaxis images are acquired. In this paper a new segmentation method for fast and robust segmentation of the left ventricle in 4D MR images is presented. The new approach considers the position of the mitral valve and the apex as well as the longaxis contours to generate a 3D LV surface model. The segmentation result can be checked and adjusted in the shortaxis images. Finally quantitative parameters were extracted. For evaluation the LV was segmented in eight datasets of the same subject by two medical experts using a contour drawing tool and the new segmentation tool. The results of both methods were compared concerning robustness and interaction time and intra- and interobserver differences. The presented segmentation method proved to be fast and robust and the intra- and interobserver differences are decreased significantly.

The carina is not a landmark for central venous catheter placement in neonates

BACKGROUND

Cardiac tamponade is rare but one of the most serious complications in relation to central venous catheters (CVC). The tip of the CVC should be placed outside the pericardium to avoid tamponade. In adults, the carina is always located above the pericardium; therefore, the carina is a reliable landmark for CVC placement. We examined whether the carina could also be an adequate landmark for CVC placement in neonates.

METHODS

The study was conducted using nine fresh neonatal cadavers. The longitudinal distance between the carina and the pericardium as it transverses the superior vena cava (the pericardial reflection: PR) was measured.

RESULTS

The median postconceptional age (gestational age in weeks + weeks after delivery) at autopsy was 35 (range: 23-42) weeks. The PR was located at a distance of 4 mm above to 5 mm below the carina. Unlike in adults, the position of the PR varies in relation to the carina in neonates. In seven of the nine subjects, the location of the PR was above the carina.

CONCLUSIONS

In neonates, the carina is not always located above the pericardium, as it is in adults; therefore, the carina is not an appropriate landmark for CVC placement.

Activation pattern of the avian left ventricle during ventricular pacing

OBJECTIVE

This study was planned to investigate ventricular myocardial excitation in birds in which Purkinje fibres penetrate into the ventricular wall and reach the epicardium to advance our knowledge about the evolution of the ventricular activation process in vertebrates.

METHODS

A depolarization pattern of the left ventricular free wall in seven open-chest laying hens was mapped by 14 seven-electrode plunge needles under ventricular pacing from different sites.

RESULTS

Duration of activation of the left ventricular free wall is significantly increased during ventricular ectopic excitation as compared with sinus rhythm. Its lowest increase occurs during subendocardial pacing of the middle part of the left ventricle, but its greatest increase is observed during subepicardial pacing of the left ventricular base. Multifocality and mosaicity of depolarization of the left ventricular myocardium are expressed in a considerably less degree during ventricular pacing in comparison with sinus rhythm.

CONCLUSION

Ectopic excitation of avian heart ventricles occurs mostly due to successive spreading of the activation wave from a pacing site during both ipsi- and contraventricular pacing. During ipsiventricular pacing at least, ectopic excitation of the heart ventricles with the "rich" Purkinje network behaves like one of the mammalian ventricles with the subendocardial Purkinje network.

The ligament of Marshall as a parasympathetic conduit

The objective of the study was to investigate the morphology, distribution, and electrophysiological profile of the autonomic fibers that innervate the ligament of Marshall (LOM). Gross anatomical dissections were performed in 10 dogs. Sections of the left vagus nerve, left stellate ganglion, and the LOM were immunostained to identify adrenergic and cholinergic nerves. Hearts were also stained for acetylcholinesterase to identify epicardial cholinergic nerves. In vivo electrophysiological studies were performed in another 10 dogs before and after LOM ablation. The anatomical examination revealed that the LOM is innervated by a branch of the left vagus. Immunohistochemistry confirmed that these nerve bundles are predominantly cholinergic (cholinergic-to-adrenergic ratio of 12.6 +/- 3.9:1). Cholinergic nerves originating in the LOM were found to innervate surrounding left atrial structures, including the pulmonary veins, left atrial appendage, coronary sinus, and posterior left atrial fat pad. Ablation of the LOM significantly attenuated effective refractory period shortening at distant sites, such as pulmonary veins and left atrial appendage, in response to vagal stimulation (vagal-induced ERP decrease in the left atrium: baseline vs. postablation = 17 vs. 4%; P = 0.0056). In conclusion, the LOM contains a predominance of cholinergic nerve fibers. Cholinergic fibers arising from the LOM innervate surrounding structures and contribute to the electrophysiological profile of the left atrium. These findings may provide a basis for the role of the LOM in the genesis and maintenance of atrial fibrillation.

High-riding superior pericardial recess: temporal change can help distinguish from mediastinal pathology

A high-riding superior pericardial recess is an infrequently encountered normal variant which may mimic mediastinal pathology. We present a patient in whom a high-riding superior pericardial recess could confidently be diagnosed on a neck CT due to its change in size and shape demonstrated on a chest CT which was done 4 minutes later.

Equine pericardium for dural grafts: clinical results in 200 patients

AIM

Serous sheets are currently used in Neurosurgery as dural substitute. The aim of this study is to demonstrate that the horse pericardium, which has the essential charasteristics of reabsorbable membranes and moreover is BSE-free, is an excellent dural substitute.

METHODS

200 patients, 53 suffering from cranial traumatic conditions and 97 from cranial and craniospinal neoplastic pathologies, underwent a surgical procedure with the application of horse pericardium as a dural prosthesis.

RESULTS

The follow-up controls of the patients included a neurosurgical visit and advanced diagnostic imaging (CT or MR). In the first 3 cases, an accumulation of CSF occurred under the surgical edge. Lumbar 7-days drainage was required in just one case. The use of Zero 5 suture seems to have obviated this problem, as it was never observed again in subsequent cases. The diagnostic imaging showed no alterated images and no clinical-neurological sequelae regarding the prosthesis in question were recorded.

CONCLUSIONS

The Audiomesh Neuro prosthesis has all the characteristics of reabsorbable membranes: they are free from antigenic effects and do not produce any toxic catabolites. The membrane proved to be resistant to surgical suture, impermeable to CSF and is transparent. Yet the suture must be carried out carefully through a small non-traumatic needle. Audiomesh Neuro does not adhere to the underlying cerebral cortex and does not cause any clinical evidence or radiological artifacts.

Spatial heterogeneity of the restitution portrait in rabbit epicardium

Spatial heterogeneity of repolarization can provide a substrate for reentry to occur in myocardium. This heterogeneity may result from spatial differences in action potential duration (APD) restitution. The restitution portrait (RP) measures many aspects of rate-dependent restitution: the dynamic restitution curve (RC), S1-S2 RC, and short-term memory response. We used the RP to characterize epicardial patterns of spatial heterogeneity of restitution that were repeatable across animals. New Zealand White rabbit ventricles were paced from the epicardial apex, midventricle, or base, and optical action potentials were recorded from the same three regions. A perturbed downsweep pacing protocol was applied that measured the RP over a range of cycle lengths from 1,000 to 140 ms. The time constant of short-term memory measured close to the stimulus was dependent on location. In the midventricle the mean time constant was 19.1 +/- 1.1 s, but it was 39% longer at the apex (P < 0.01) and 23% longer at the base (P = 0.03). The S1-S2 RC slope was dependent on pacing site (P = 0.015), with steeper slope when pacing from the apex than from the base. There were no significant repeatable spatial patterns in steady-state APD at all cycle lengths or in dynamic RC slope. These results indicate that transient patterns of epicardial heterogeneity of APD may occur after a change in pacing rate. Thus it may affect cardiac electrical stability at the onset of a tachycardia or during a series of ectopic beats. Differences in restitution with respect to pacing site suggest that vulnerability may be affected by the location of reentry or ectopic foci.

The anatomy of the tendon of the infundibulum revisited

The heart is a muscular organ supported by collagenous tissue. The collagenous tissue is condensed in certain areas to form a supporting framework, often called the fibrous skeleton. The so-called tendon of the infundibulum has previously been described as part of this skeleton, but its structure and incidence remain ill defined. The tendon was initially described as a strip of fibrous tissue running between the aortic root and the pulmonary trunk. Since information on its structure is vague, we sought to evaluate its existence in 100 formalin-fixed adult human hearts obtained from subjects ranging in age from 22 to 86 years, in 20 hearts from infants and children aged from 2 months to 6 years at the time of their death and in 10 cattle hearts. We used classical macroscopic anatomical techniques to demonstrate all the possible connections between the sinuses of the aorta and the pulmonary trunk. We then supplemented the macroscopic techniques with serial transverse histological sections taken through the vascular roots, staining the sections with the haematoxylin-eosin, van Gieson, Masson trichrome and orcein staining methods. Fascial bands surrounded by connective tissue were observed in all hearts. In 80 adult hearts and in 16 neonatal hearts we found fascial bands or strips, which connected the aortic and pulmonary roots. Only in two hearts, however, were we able to identify tendon-like structures, and histology revealed that these were formed by tightly packed collagen fibres intermingled with fat, most likely due to advanced age. Thus in those cases where a "tendon" was present it was no more than condensed fascial bands joining together the apposing sinuses of the arterial trunks. In our opinion, therefore, accounts in the literature describing the "tendon of the infundibulum" as a tendinous structure connecting the aortic and pulmonary roots do not accurately represent this anatomical structure.

Evolutionary and comparative anatomical investigations of the autonomic cardiac nervous system in the African cercopithecidae

The purpose of this study was to clarify the general architecture and morphological variations of the autonomic cardiac nervous system (ACNS) in the African Cercopithecidae (Old World monkeys), and to discuss the evolutionary changes between this system in African/Asian Cercopithecidae and humans. A detailed macroscopic comparative morphological investigation of the ACNS was performed by examining the left and right sides of 11 African cercopithecid specimens, including some previously unreported species (Abyssinian colobus, Angola pied colobus, Savanna monkey, and lesser white-nosed guenon). The common characteristics of the ACNS in the African Cercopithecidae are described in detail. Consequently, homologies of the ACNS between Asian (macaques) and African Cercopithecidae, and differences between the Asian/African Cercopithecidae and humans, were found. In particular, differences in the sympathetic (cardiac) systems of the Cercopithecidae and humans were recognized, despite the similar morphology of the parasympathetic vagal (cardiac) system. These differences include the composition of the cervicothoracic ganglion, the lower positions of the middle cervical and cervicothoracic ganglia, and the narrow range for the origin of the cardiac nerves in the Cercopithecidae, compared with that in humans. In conclusion, these findings are considered with regard to the morphology of the last common ancestors of the Cercopithecidae.

Applicability of the Single Equivalent Moving Dipole Model in an Infinite Homogeneous Medium to Identify Cardiac Electrical Sources: A Computer Simulation Study in a Realistic Anatomic Geometry Torso Model

We have previously proposed an inverse algorithm for fitting potentials due to an arbitrary bio-electrical source to a single equivalent moving dipole (SEMD) model. The algorithm achieves fast identification of the SEMD parameters by employing a SEMD model embedded in an infinite homogeneous volume conductor. However, this may lead to systematic error in the identification of the SEMD parameters. In this paper, we investigate the accuracy of the algorithm in a realistic anatomic geometry torso model (forward problem). Specifically, we investigate the effect of measurement noise, dipole position and electrode configuration in the accuracy of the algorithm. The boundary element method was used to calculate the forward potential distribution at multiple electrode positions on the body surface due to a point dipole in the heart. We have found that the position and not the number of electrodes as well as the site of the origin of the arrhythmia in the heart have a significant effect on the accuracy of the inverse algorithm, while the measurement noise does not. Finally, we have shown that the inverse algorithm preserves the topology of the source distribution in the heart, thus potentially allowing the cardiac electrophysiologist to efficiently and accurately guide the tip of the catheter to the ablation site.

Myocardial triglyceride content and epicardial fat mass in human obesity: relationship to left ventricular function and serum free fatty acid levels

CONTEXT AND OBJECTIVE

Ectopic fat accumulation within and around the myocardial wall has been implicated in the pathogenesis of heart disease in obesity. We evaluated myocardial and epicardial fat, left ventricular (LV) function, and metabolic risk factors in nine (five lean, four moderately obese) men.

METHODS

Myocardial fat percent was quantified in the septum by proton magnetic resonance spectroscopy. Reproducibility was assessed by triplicate systolic and diastolic measurements. LV parameters and epicardial fat were determined by magnetic resonance imaging. Waist-to-hip ratio and liver enzymes (alanine transaminase) were used as surrogate markers of visceral and liver fat contents.

RESULTS

Myocardial fat (2.1 +/- 0.5 vs. 0.8 +/- 0.1, P = 0.03) and epicardial fat (120 +/- 33 vs. 55 +/- 12 g, P = 0.08) were higher in obese than lean subjects. Individuals with above-median alanine transaminase values had a 4-fold elevation in myocardial fat. The coefficient of variation of repeated myocardial fat percent determinations was 17 +/- 3 and 23 +/- 3% in systole and diastole, respectively. Myocardial fat was correlated with free fatty acid (FFA) levels (r = 0.76; P = 0.017), epicardial fat (r = 0.69; P = 0.042), and waist-to-hip ratio (r = 0.70; P = 0.035), and it showed a tendency to associate positively with LV work. Epicardial fat was associated with peripheral vascular resistance (positively) and the cardiac index (negatively). FFA levels were significantly correlated with LV mass (r = 0.72; P = 0.030) and forward work (r = 0.74; P = 0.023).

CONCLUSIONS/INTERPRETATION

The accumulation of triglyceride in and around the myocardium of moderately obese individuals is significant, and it is related to FFA exposure, generalized ectopic fat excess, and peripheral vascular resistance. These changes precede LV overload and hypertrophy.

Identification of elastic fibers and lamellae in porcine pericardium and aorta by confocal, fluorescence and polarized light microscopy

Pericardial connective tissue has been used to construct bioprostheses to repair various types of injuries, including aortic wall repairs. The arrangement and the distribution of elastic and collagen staple fibers are related directly to the biomechanical properties of the tissue and thus determine the choice tissue for the construction of bioprostheses. Although elastic fibers can be visualized using several histochemical methods, the specificity and mechanism of binding involved remain to be clarified. In this work, we compared the elastic net of the porcine pericardial matrix with that of the aortic wall using 1-anilino-8-naphthalene sulfonate (ANS) and dansyl chloride (DCl) as fluorescent probes and the permanganate-bisulfite-toluidine (PBT) method. Polarized light and fluorescence microscopy were simultaneously used to analyze the tissues. Some samples also were examined using confocal microscopy. Aorta and pericardium treated with ANS and DCl showed elastic fibers and lamellae with an intense blue fluorescence. When stained with the PBT method, the aortic elastic lamellae were clearly metachromatic and, under polarized light, they showed a greenish birefringence. DCl provided clearer fluorescent labelling of elastic fibers when examined using confocal microscopy.

Location and variability of epicardiac ganglia in human fetuses

The aim of the study was to determine the morphology of epicardiac ganglia in human fetuses at different stages of their development as these ganglia are considered to be of a pivotal clinical importance. Twenty-one fetal hearts were investigated applying a technique of histochemistry for acetylcholinesterase to visualize the epicardiac neural ganglionated plexus with its subsequent stereoscopic examination on total organs. In all of the examined fetuses, epicardiac neural plexus with numerous ganglia was well recognizable and could be clearly differentiated into seven ganglionated subplexuses, topography and structural organization of which were typical for hearts of adult human. The largest ganglion number comprising 77% of all counted ganglia was identified on the dorsal atrial surface. Fetal epicardiac plexus in gestation period of 15-40 weeks contained 929 +/- 62 ganglia, but ganglion amount did vary substantially from heart to heart. In conclusion, this study implies that the human fetal epicardiac ganglia occupy their definitive location already at gestation period from 15 weeks and their number as well as distribution on heart surface presumably is not age dependent.

Implication of the anatomy of the pericardial reflection on positioning of central venous catheters

OBJECTIVE

Central venous catheterization is associated with a significant incidence of complications (5%-20%). The incidence of perforation is approximately 0.25% to 0.4%. To prevent cardiac tamponade associated with a high risk of death, Food and Drug Administration guidelines state that the tip of a central venous catheter (CVC) should not be placed in, or allowed to migrate into, the heart. Therefore, in order to prevent cardiac tamponade, a catheter should be placed above the pericardial reflection. Thus, the intrapericardial length of the superior vena cava (SVC) was studied. Neither the pericardial reflection nor the exact entrance to the right atrium (RA) can be identified by chest x-ray. The goal of this study was to evaluate the variability of the intrapericardial section in relation to the SVC.

DESIGN

Observational study.

INTERVENTIONS

The absolute length of the SVC, the upper edge of the pericardial reflection on the SVC, and the lateral and the medial intrapericardial sections of the SVC were recorded and statistically analyzed.

SETTING

Medical school: dissecting room at the Department of Anatomy.

STUDY POPULATION

Eighteen formalin-preserved adult cadavers.

MEASUREMENTS AND MAIN RESULTS

The median lengths measured were as follows: total SVC, 61 mm; intrapericardial section of the medial SVC, 32.5 mm; and lateral SVC, 20.5 mm. The intrapericardial section was related to the total length of the SVC on both sides (Spearman rank order, p < 0.05). The median difference of the SVC covered with pericardium between the lateral and medial side was 11 mm (range, 5-21). In 15 of 18 cadavers, the pericardial reflection ran within the medial third of the SVC. The lower third of the SVC was regularly covered by the pericardium. The duplication of the pericardium crossed the SVC in the medial third at a diagonal to horizontal angle.

CONCLUSIONS

Catheters ending below the pericardial reflection, hence positioned in the caudal third of the SVC, are likely to run along the long axis of the vein and the risk for perforation is minimized. Therefore, the authors recommend placing all catheters below the pericardial reflection. According to the present data, CVCs placed approximately 30 mm above the RA border, thus complying with the Food and Drug Administration guidelines, still may have their tips positioned below the pericardial reflection. In this position, pericardial tamponade still may occur. Perforation above the pericardial reflection will result in a hemo- or hydrothorax/mediastinum. A bedside method to determine the position of the CVC with respect to the pericardial reflection (eg, electrocardiographic guidance) should be used.

Relationship of pulmonary vein flow to left ventricular short-axis epicardial displacement in diastole: model-based prediction with in vivo validation

Previous studies in healthy humans have established that the (approximately 850 ml) volume enclosed by the pericardial sac is nearly constant over the cardiac cycle, exhibiting a transient approximately 5% decrease (approximately 40 ml) from end diastole to end systole. This volume decrease manifests as a "crescent" at the ventricular free wall level when short-axis MRI images of the epicardial surface acquired at end systole and end diastole are superimposed. On the basis of the (near) constant-volume property of the four-chambered heart, the volume decrease ("crescent effect") must be restored during subsequent early diastolic filling via the left atrial conduit volume. Therefore, volume conservation-based modeling predicts that pulmonary venous (PV) Doppler D-wave volume must be causally related to the radial displacement of the epicardium (Delta) (i.e., magnitude of "crescent effect" in the radial direction). We measured Delta from M-mode echocardiographic images and measured D-wave velocity-time integral (VTI) from Doppler PV flow of the right superior PV in 11 subjects with catheterization-determined normal physiology. In accordance with model prediction, high correlation was observed between Delta and D-wave VTI (r=0.86) and early D-wave VTI measured to peak D-wave velocity (r=0.84). Furthermore, selected subjects with various pathological conditions had values of Delta that differed significantly. These observations demonstrate the volume conservation-based causal relationship between radial pericardial displacement of the left ventricle and the PV D-wave-generated filling volume in healthy subjects as well as the potential role of the M-mode echo-derived radial epicardial displacement index Delta as a regional (radial) parameter of diastolic function.

Histochemical study of cardiac mast cells degranulation and collagen deposition: interaction with the cathecolaminergic system in the rat

Although their role in the cardiovascular system is still largely unknown, mast cells are present in the myocardium of both experimental animals and humans. Interestingly, cathecolaminergic nerve fibres and mast cells are often described in close morphological and functional interactions in various organs. In the present study we investigated the effects of chronic interference with beta-adrenergic receptors (via either sympathectomy or beta-blockade) on cardiac mast cell morphology/activation and on interstitial collagen deposition. In rats subjected to chemical sympathectomizy with the neurotoxin 6-hydroxydopamine (6-OHDA) we observed a significant increase of mast cell density, and in particular of degranulating mast cells, suggesting a close relationship between the cardiac catecholaminergic system and mast cell activation. In parallel, chronic 6-OHDA treatment was associated with increased collagen deposition. The influence of the beta-adrenergic receptor component was investigated in rats subjected to chronic propranolol administration, that caused a further significant increase in mast cell activation associated with a lower extent of collagen deposition when compared to chemical sympathectomy. These data are the first demonstration of a close relationship between rat cardiac mast cell activation and the catecholaminergic system, with a complex interplay with cardiac collagen deposition. Specifically, abrogation of the cardiac sympathetic efferent drive by chemical sympathectomy causes mast cell activation and interstitial fibrosis, possibly due to the local effects of the neurotoxin 6-hydroxydopamine. In contrast, beta-adrenergic blockade is associated with enhanced mast cell degranulation and a lower extent of collagen deposition in the normal myocardium. In conclusion, cardiac mast cell activation is influenced by beta-adrenergic influences.

Endocardium and epicardium contour modeling based on Markov Random Fields and active contours

A segmentation application prototype of the volume of the left ventricle for Magnetic Resonance Imaging is being developed. The foundation for this work is given by modeling possible radial deformations of the epicardium and endocardium contours by means of a Markov Random Field over which the most probable configuration is estimated. The field makes use of a Bayesian approach based on a priori terms which impose smoothness along the coupled contours and likelihood terms which gather information provided by the images about the areas where the contours are supposed to be. The parameters of the field are estimated on a supervised basis.

Computed tomography and magnetic resonance imaging of the pericardium: anatomy and pathology

The purpose of this article is to review the characteristics of computed tomography (CT) and magnetic resonance imaging (MRI) of the pericardium and pericardial diseases. Because patients with pericardial diseases usually present with nonspecific symptoms, these diseases may not be detected until they have reached an advanced stage. It is therefore important to distinguish between normal pericardial structure and disease. Multiplanar reconstruction images of CT and MRI are useful for evaluating faint changes of the pericardium. The specific pericardial diseases described in this article include pericardial cyst, constrictive pericarditis, pericarditis with radiation pericarditis, postoperative pericardial hematoma, and cardiac tamponade due to a paracardiac mass (lymphoma).

Anatomic Relations Between the Esophagus and Left Atrium and Relevance for Ablation of Atrial Fibrillation

Background— Esophageal injury is a potential complication after intraoperative or percutaneous transcatheter ablation of the posterior aspect of the left atrium. Understanding the spatial relations between the esophagus and the left atrium is essential to reduce risks.

Methods and Results— We examined by gross dissection the course of the esophagus in 15 cadavers. We measured the minimal distance of the esophageal wall to the endocardium of the left atrium with histological studies in 12 specimens. To measure the transmural thickness of the atrial wall, we sectioned another 30 human heart specimens in the sagittal plane at 3 different regions of the left atrium. The esophagus follows a variable course along the posterior aspect of the left atrium; its wall was <5 mm from the endocardium in 40% of specimens. The posterior left atrial wall has a variable thickness, being thickest adjacent to the coronary sinus and thinnest more superiorly. Behind is a layer of fibrous pericardium and fibrofatty tissue of irregular thickness that contains esophageal arteries of 0.4±0.2-mm external diameters.

Conclusions— The nonuniform thickness of the posterior left atrial wall and the variable fibrofatty layer between the wall and the esophagus are risk factors that must be considered during ablation procedure. Esophageal arteries and vagus nerve plexus on the anterior surface of the esophagus may be affected by ablative procedures.