Creation of ventricular septal defects on the beating heart in a new pig model

Background/ Aims: So far, surgical and interventional therapies for muscular ventricular septal defects ( mVSDs) beyond the moderator band have had their limitations. Thus, alternative therapeutic strategies should be developed. We present a new animal model for the evaluation of such strategies. Methods: In a pig model ( n = 9), anterolateral thoracotomy was performed for exposure of the left ventricle. mVSDs were created under two- and three- dimensional echocardiography with a 7.5- mm sharp punch instrument, which was forwarded via a left ventricular puncture without extracorporeal circulation. Results: Creation of mVSDs was successful in all animals ( n = 9) confirmed by echocardiography, hemodynamic measurements and autopsy. The defects were located in the midmuscular ( n = 4), apical ( n = 1), inlet ( n = 2) and anterior part ( n = 2) of the muscular septum. All animals were hemodynamically stable for further procedures. The diameter and shunt volume of the mVSDs were 4.8 - 7.3 mm ( mean: 5.9 mm) and 12.9 - 41.3% ( mean: 22.1%), respectively. Autopsy confirmed in all animals the creation of a substantial defect. Conclusion: The described new technique for creation of an mVSD on the beating heart in a pig model is suitable for the evaluation of new therapeutic strategies for mVSD closure. Copyright (C) 2008 S. Karger AG, Basel

Types of directed triple systems

We introduce three types of directed triple systems. Two of these, Mendelsohn directed triple systems and Latin directed triple systems, have previously appeared in the literature but we prove further results about them. The third type, which we call skewed directed triple systems, is new and we determine the existence spectrum to be v ≡ 1 (mod 3), v ≠ 7, except possibly for v = 22, as well as giving enumeration results for small orders

Narrative review of Ebstein's anomaly beyond childhood: imaging, surgery, and future perspectives

Ebstein's anomaly is a rare congenital heart disease with malformation of the tricuspid valve and myopathy of the right ventricle. The septal and inferior leaflets adhere to the endocardium due to failure of delamination. This leads to apical displacement of their hinge points with a shift of the functional tricuspid valve annulus towards the right ventricular outflow tract with a possibly restrictive orifice. Frequently, a coaptation gap yields tricuspid valve regurgitation and over time the "atrialized" portion of the right ventricle may dilate. The highly variable anatomy determines the clinical presentation ranging from asymptomatic to very severe with need for early operation. Echocardiography and magnetic resonance imaging are the most important diagnostic modalities to assess the tricuspid valve as well as ventricular morphology and function. While medical management of asymptomatic patients can be effective for many years, surgical intervention is indicated before development of significant right ventricular dilatation or dysfunction. Onset of symptoms and arrhythmias are further indications for surgery. Modified cone reconstruction of the tricuspid valve is the state-of-the-art approach yielding the best results for most patients. Alternative procedures for select cases include tricuspid valve replacement and bidirectional cavopulmonary shunt depending on patient age and other individual characteristics. Long-term survival after surgery is favorable but rehospitalization and reoperation remain significant issues. Further studies are warranted to identify the optimal surgical strategy and timing before adverse right ventricular remodeling occurs. It is this article's objective to provide a comprehensive review of current literature and an overview on the management of Ebstein's Anomaly. It focuses on imaging, cardiac surgery, and outcome. Additionally, a brief insight into arrhythmias and their management is given. The "future perspectives" summarize open questions and fields of future research.Thoracic Surger

Paediatric and adult congenital cardiology education and training in Europe

Background: Limited data exist on training of European paediatric and adult congenital cardiologists. Methods: A structured and approved questionnaire was circulated to national delegates of Association for European Paediatric and Congenital Cardiology in 33 European countries. Results: Delegates from 30 countries (91%) responded. Paediatric cardiology was not recognised as a distinct speciality by the respective ministry of Health in seven countries (23%). Twenty countries (67%) have formally accredited paediatric cardiology training programmes, seven (23%) have substantial informal (not accredited or certified) training, and three (10%) have very limited or no programme. Twenty-two countries have a curriculum. Twelve countries have a national training director. There was one paediatric cardiology centre per 2.66 million population (range 0.87-9.64 million), one cardiac surgical centre per 4.73 million population (range 1.63-10.72 million), and one training centre per 4.29 million population (range 1.63-10.72 million population). The median number of paediatric cardiology fellows per training programme was 4 (range 1-17), and duration of training was 3 years (range 2-5 years). An exit examination in paediatric cardiology was conducted in 16 countries (53%) and certification provided by 20 countries (67%). Paediatric cardiologist number is affected by gross domestic product (R-2 = 0.41). Conclusion: Training varies markedly across European countries. Although formal fellowship programmes exist in many countries, several countries have informal training or no training. Only a minority of countries provide both exit examination and certification. Harmonisation of training and standardisation of exit examination and certification could reduce variation in training thereby promoting high-quality care by European congenital cardiologists.Developmen

Triple systems and binary operations

It is well known that given a Steiner triple system (STS) one can define a binary operation ∗ upon its base set by assigning x∗x=x for all x and x∗y=z, where z is the third point in the block containing the pair {x,y}. The same can be done for Mendelsohn triple systems (MTSs) as well as hybrid triple systems (HTSs), where (x,y) is considered to be ordered. In the case of STSs and MTSs, the operation is a quasigroup, however this is not necessarily the case for HTSs. In this paper we study the binary operation induced by HTSs. It turns out that each such operation ∗ satisfies γ∈ {x*(x*y), (x*y)*x} and γ∈ {(y*x)*x, x*(y*x)} for all x and y from the base set. We call every binary operation that fulfils this condition hybridly symmetric. Not all idempotent hybridly symmetric operations can be obtained from HTSs. We show that these operations correspond to decompositions of a complete digraph into certain digraphs on three vertices. However, an idempotent hybridly symmetric quasigroup always comes from an HTS. The corresponding HTS is then called a latin HTS (LHTS). The core of this paper is the characterization of LHTSs and the description of their existence spectrum

The centre of a Steiner loop and the maxi-Pasch problem

summary:A binary operation ``$\cdot$'' which satisfies the identities $x\cdot e = x$, $x \cdot x = e$, $(x \cdot y) \cdot x = y$ and $x \cdot y = y \cdot x$ is called a Steiner loop. This paper revisits the proof of the necessary and sufficient conditions for the existence of a Steiner loop of order $n$ with centre of order $m$ and discusses the connection of this problem to the question of the maximum number of Pasch configurations which can occur in a Steiner triple system (STS) of a given order. An STS which attains this maximum for a given order is said to be {\it maxi-Pasch}. We show that loop factorization preserves the maxi-Pasch property and find that the Steiner loops of all currently known maxi-Pasch Steiner triple systems have centre of maximum possible order

Antiflexible Latin directed triple systems

summary:It is well known that given a Steiner triple system one can define a quasigroup operation $\cdot$ upon its base set by assigning $x \cdot x = x$ for all $x$ and $x \cdot y = z$, where $z$ is the third point in the block containing the pair $\{x,y\}$. The same can be done for Mendelsohn triple systems, where $(x,y)$ is considered to be ordered. But this is not necessarily the case for directed triple systems. However there do exist directed triple systems, which induce a quasigroup under this operation and these are called Latin directed triple systems. The quasigroups associated with Steiner and Mendelsohn triple systems satisfy the flexible law $y \cdot (x \cdot y) = (y \cdot x) \cdot y$ but those associated with Latin directed triple systems need not. In this paper we study the Latin directed triple systems where the flexible identity holds for the least possible number of ordered pairs $(x, y)$. We describe their geometry, present a surprisingly simple cyclic construction and prove that they exist if and only if the order $n$ is $n\equiv 0$ or $1\pmod{3}$ and $n\geq 13$

On quasigroups satisfying Stein's third law

A quasigroup (Q, ·) of order v satisfies Stein’s third law if (y ·x) ·(x ·y) =x holds for all x, y ∈Q. Let the quasigroup contain n idempotent elements. We construct such quasigroups with (v, n) ∈\{(20, 0), (24, 0), (28, 0), (36, 0)\}, thus completing the existence spectrum of quasigroups satisfying Stein’s third law with no idempotents. We also construct previously unknown quasigroups with (v, n) ∈\{(17, 11), (21, 3), (21, 7), (24, 4), (25, 7), (25, 19)\} and provide an enumeration for all v ≤9

Quadratical quasigroups and Mendelsohn designs

Let the product of points A and B be the vertex C of the right isosceles triangle for which AB is the base, and ABC is oriented anticlockwise. This yields a quasigroup that satisfies laws (xu) (vy) = (xv)(uy), (xy)(yx) = y and xx = x. Such quasigroups are called quadratical. Quasigroups that satisfy only the latter two laws are equivalent to perfect Mendelsohn designs of length four (PMD(v,4)). This paper examines various algebraic identities induced by PMD(v,4), classifies finite quadratical quasigroups, and shows how the square structure of quadratical quasigroups is associated with toroidal grids