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Biomedical subjects

R H Anderson

Publications and source records attributed to R H Anderson.

At least 73 records · Page 4Linked to original sources
PubMed2000

A multifilamented electrode in the middle cardiac vein reduces energy requirements for defibrillation in the pig.

OBJECTIVE: To compare the defibrillation efficacy of a novel lead system placed in the middle cardiac vein with a conventional non-thoracotomy lead system. METHODS: In eight pigs (weighing 35-71 kg), an electrode was advanced transvenously to the right ventricular apex (RV), with the proximal electrode in the superior caval vein (SCV). Middle cardiac vein (MCV) angiography was used to delineate the anatomy before a three electrode system (length 2 x 25 mm + 1 x 50 mm) was positioned in the vein. An active housing (AH) electrode was implanted in the left pectoral region. Ventricular fibrillation was induced and biphasic shocks were delivered by an external defibrillator. The defibrillation threshold was measured and the electrode configurations randomised to: RV-->AH, RV+MCV-->AH, MCV-->AH, and RV-->SCV+AH. RESULTS: For these configurations, mean (SD) defibrillation thresholds were 27.3 (9.6) J, 11.9 (2.9) J, 15.2 (4.3) J, and 21.8 (9.3) J, respectively. Both electrode configurations incorporating the MCV had defibrillation thresholds that were significantly less than those observed with the RV-->AH (p < 0.001) and RV-->SCV+AH (p < 0.05) configurations. Necropsy dissection showed that the MCV drained into the coronary sinus at a location close to its orifice (mean distance = 2.7 (2.2) mm). The MCV bifurcated into two main branches that drained the right and left ventricles, the left branch being the dominant vessel in the majority (6/7) of cases. CONCLUSIONS: Placement of specialised defibrillation electrodes within the middle cardiac vein provides more effective defibrillation than a conventional tight ventricular lead.

Analysis of Variance↗
PubMed2000

Adolescents' use of tobacco, health locus of control, and self-monitoring.

This study examined the association of the traits, health locus of control, and self-monitoring with adolescents' tobacco uptake. Participants were 112 rural adolescents (12 to 19 years old, M = 15.3). Of that sample, 33% used tobacco. Tobacco users were found to score lower on the dimension of Internality and higher on the dimension of Chance, as compared with nonusers of tobacco, indicating a more external Health Locus of Control. In addition, tobacco users were lower self-monitors than were nonusers. These results suggest that adolescents who use tobacco feel less in control of their lives in relation to nonusers, believe that chance plays a larger role in their health, and believe they may be unable to monitor and adapt their communication to achieve positive outcomes.

Adolescent↗
PubMed1999

Living anatomy of the atrioventricular junctions. A guide to electrophysiologic mapping. A Consensus Statement from the Cardiac Nomenclature Study Group, Working Group of Arrhythmias, European Society of Cardiology, and the Task Force on Cardiac Nomenclature from NASPE.

Current nomenclature for the atrioventricular (AV) junctions derives from a surgically distorted view, placing the valvar rings and the triangle of Koch in a single plane with antero-posterior and right-left lateral coordinates. Within this convention, the aorta is considered to occupy an anterior position, although the mouth of the coronary sinus is shown as being posterior. Although this nomenclature has served its purpose for the description and treatment of arrhythmias dependent on accessory pathways and atrioventricular nodal reentry, it is less than satisfactory for the description of atrial and ventricular mapping. To correct these deficiencies, a consensus document has been prepared by experts from the Working Group of Arrhythmias of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology. It proposes a new anatomically sound nomenclature that will be applicable to all chambers of the heart. In this report, we discuss its value for description of the AV junctions, establishing the principles of this new nomenclature.

Atrioventricular Node↗
PubMed1999

Angiographic anatomy of the inferior right atrial isthmus in patients with and without history of common atrial flutter.

BACKGROUND: Although most ablative procedures undertaken for common atrial flutter target the inferior right atrial isthmus, comparative studies of the morphology of this area are lacking. Our study examines its angiographic anatomy, making correlations with postmortem specimens, to provide a better understanding of the anatomic substrate of this arrhythmia. METHODS AND RESULTS: The gross morphological features and dimensions of the area between the orifice of the inferior caval vein and the attachment of the septal leaflet of the tricuspid valve were determined from angiograms made in 23 patients with documented atrial flutter and 30 control subjects. For comparison, we studied 20 normal heart specimens. When viewed in right anterior oblique projection, 2 morphologically distinct areas were identified. In the specimens, the inferior isthmus measured a mean length of 30+/-4 mm, not significantly different from the dimensions obtained from angiograms of control subjects. The mean length of the isthmus, however, was greater in patients with common atrial flutter than those without (37+/-8 versus 28+/-6 mm). Patients with atrial flutter and structural heart disease had an even longer isthmus than those with flutter alone (39. 6+/-8 versus 33+/-7 mm). Compared with those without flutter, the atrial diameter was also larger in patients with flutter (57.6+/-9 versus 48.5+/-6 mm). Reevaluation carried out at follow-up 10+/-2 months after ablation did not show any reduction in atrial size, although contractility improved. CONCLUSIONS: The inferior isthmus and right atrium in patients with common atrial flutter were significantly larger than those in a control population.

Adult↗
PubMed1999

Mechanisms of deficient cardiac septation in the mouse with trisomy 16.

It used to be thought that the atrioventricular septum was predominantly the product of the atrioventricular endocardial cushions. In a previous study, we have shown that multiple developmental primordia are of importance in its formation. With this in mind, we have evaluated cardiac morphogenesis in the mouse with trisomy 16, an animal model with a high incidence of atrioventricular septal defects. Normal and trisomic fetuses from an Rb(11.16)2H/Rb(16.17)7Bnr x C57BL/6J cross were collected on days 10 to 15 of gestation and examined by scanning electron microscopy and histological serial sectioning. No evidence was found to suggest that atrioventricular septal defect could be explained simply on the basis of "failure of fusion" between the atrioventricular endocardial cushions. Rather, our findings supported two other developmental elements as being important in the genesis of atrioventricular septal defect. The first is an alteration in the configuration of the heart tube, with inadequate remodeling of the inner heart curvature. This resulted in the failure of the atrioventricular junction to expand to the right, with subsequent malalignment of the atrioventricular endocardial cushions with the proximal outflow cushions. The second is a variability in the connection of the primary atrial cardiac segment to the body of the embryo, the so-called dorsal mesocardium, which influences its relationship to the extracardiac mediastinal mesoderm. There appeared little difference in the connection between normal and trisomic embryos at the stage of 20 to 25 somites, but the area subsequently showed marked changes. In most trisomic embryos, the connection with the mediastinal mesoderm of the body was over a larger area than seen in normal embryos. As this area of attachment encloses the pulmonary pit, the entry point of the pulmonary vein, this gives potential for variation in the connection of the pulmonary vein. In addition, in the majority of trisomic embryos, the right pulmonary ridge (the spina vestibuli) did not accumulate extracardiac mesoderm, nor did it undergo the pronounced forward growth seen in normal embryos of equivalent stages. Consequently, the trisomic embryos show incomplete formation of both the atrial and the atrioventricular septal structures.

Animals↗
PubMed1999

Distribution of the Purkinje fibres in the sheep heart.

The aim of the present study was to advance our knowledge regarding the anatomy of the purkinje fibres from their origin, at the bundle branches, till their termination within the myocardium. Indian ink injections of the purkinje fibres were carried out in the left ventricle of 25 fresh sheep hearts and in the right ventricle of 20 hearts. Numerous samples were taken from the walls and papillary muscles of the two ventricles for histological analysis and determination of the mode of termination of the fibres. The ventricular conduction system could be injected as far proximally as the bundle branches, thus illustrating the bifascicular nature of the left bundle branch, with numerous interfascicular communications. The purkinje fibres were observed to form an extensive subendocardial network, forming a polygonal arrangement in the left ventricle with a characteristic pattern around the papillary muscles. Deep myocardial branches took origin from this network which penetrated the ventricular wall to reach the epicardium. Histological analysis demonstrated the characteristic features of the purkinje cells, and confirmed the presence ofa perifascicular sheath of connective tissue which surrounded the purkinje fibres until their transition with working cardiomyocytes. The perifascicular connective tissue sheath is important in organising the contraction of the myocardium by preventing lateral spread of conduction and by permitting transmission of the impulse only at the termination of the purkinje fibre. The sheath may also protect the fibres from the stresses and strains originating from contraction of the surrounding myocardium.

Animals↗
PubMed1999

Clinical anatomy of the atrial septum with reference to its developmental components.

Knowledge of development is of crucial importance and can help clarify mechanisms of maldevelopment, but it must be properly validated. Concepts of development must be consistent with the anatomy seen in postnatal life. Such consistency is not always achieved. We have reviewed new and old accounts of cardiac embryology with regard to the definitive structure of the atrial septum. The key to understanding is to distinguish between folds of the atrial wall and true interatrial partitions. The flap valve of the oval foramen, and its inferior rim, are true septal structures, whereas the other rims, particularly the antero-superior rim, are infoldings enclosing extracardiac fat. During embryonic life, the systemic venous tributaries must achieve entrance only to the right side of the primary atrium. Development of the pulmonary venous component is a late event, with the canalizing vein using the dorsal mesocardium to gain access to the left side of the atrium. Once the systemic venous tributaries have achieved their rightward shift, the primary septum, together with the mesenchymal cap, grows between the systemic and pulmonary venous orifices. Closure of the primary foramen is achieved by fusion of the mesenchymal cap of the primary septum with the atrioventricular endocardial cushions and the vestibular spine (an additional mesenchymal structure carried on the right side of the pulmonary venous orifice). The superior margin of the newly formed secondary foramen is produced by an infolding of the atrial walls. Historically these mechanisms received appropriate recognition, but not all receive their proper due in current writings.

Endocardium↗
PubMed1999

Ventricular morphology and coronary arterial anatomy in hearts with isometric atrial appendages.

BACKGROUND: Knowledge of the precise anatomy can be advantageous when striving to improve surgical results in patients with visceral heterotaxy. METHODS: We studied the ventricular mass, and its coronary arterial supply, in 125 specimens with isomeric right and 58 with isomeric left appendages. RESULTS: The situation in which each atrium connected to its own ventricle was the most common arrangement in hearts with isomeric left appendages. The pattern with both atriums connecting to the same ventricle was more frequently seen in those with isomeric right appendages. Concordant ventriculoarterial connections were seen in only 4% of cases with isomeric right appendages, but were seen in 45% of those with isomeric left appendages. Abnormal patterns in branching of the coronary arteries were commonly associated with abnormal ventricular architecture. The morphologically right or left ventricular arteries were frequently lacking in those hearts with a dominant ventricle and a rudimentary and incomplete ventricle. A solitary coronary artery was seen in 13%. CONCLUSIONS: Recognition of these abnormalities is of clinical importance if optimal surgical strategies are to be established for patients with visceral heterotaxy.

Coronary Vessels↗
PubMed1999

Management of ventricular septal defect: a survey of practice in the United Kingdom.

BACKGROUND: A survey of pediatric cardiac surgeons was performed to establish current opinions in the United Kingdom concerning closure of ventricular septal defect. METHODS: Questionnaires were sent to 14 pediatric cardiac centers in 1995 (16 surgeons, 100% response), and again in 1997 (20 surgeons, 100% response). RESULTS: Results are presented for 1997, with findings from 1995 shown in parentheses. Eleven (6) surgeons used bypass exclusively, 9 (10) sometimes used circulatory arrest. Operative techniques were similar, although the material used for the patch varied. Multiple defects were approached via the transatrial route by 18 (15), right ventriculotomy by 11 (7) and left ventriculotomy by 7 (6). The juxta-arterial defect was approached via the transpulmonary route by 16 (13), a combination by 9 (11), transatrial by 10 (6), and transventricular by 9 (5). The most common indications for pulmonary arterial banding were "Swiss cheese" defect for 13 (13), and functionally single ventricle for 5 (6). Ventricular septal defect associated with coarctation was repaired in two stages by 13 (10), a single stage by 5 (3), or either by 1 (3). CONCLUSIONS: Pediatric cardiac surgeons in the United Kingdom demonstrate a uniform, evidence-based approach to the management of ventricular septal defect.

Aortic Coarctation↗
PubMed1999

Common arterial trunk associated with double aortic arch.

The combination of common arterial trunk associated with double aortic arch is very rare. We are aware of only four cases ever reported in English literature. We add two cases of this entity and comment on the morphological aspects, the clinical impact of the combined lesions, and their diagnostic and therapeutic implications.

Aorta, Thoracic↗
PubMed1999

The nature of the obstructive muscular bundles in double-chambered right ventricle.

OBJECTIVE: Our goal was to establish the morphologic nature of the obstructive muscular lesions in double-chambered right ventricle. METHODS: We based our morphologic observations on 10 normal hearts and on the surgical findings in 26 patients, aged 0.5 to 24 years, with a mean of 6.9 years (SD 5.8 years). In the normal hearts, we measured the distance from the pulmonary valve to the apex of the right ventricle and from the takeoff of the moderator band to the ventricular apex. From angiograms available in 20 patients, using the frontal view, we then measured the distance from the pulmonary valve to the apex of the right ventricle and from the midpoint of the obstructive lesion to the apex of the right ventricle. This permitted calculations of multiple ratios. RESULTS: In the 10 normal hearts, the moderator band took origin at a mean ratio of 0.48 (SD 0.16) of the ventricular length. On the basis of the angiographic findings, we identified 2 basic forms of double-chambered right ventricle. In 9 patients, the obstructive muscular shelf was positioned low and diagonally across the apical component, with a mean ratio of 0.38 relative to the ventricular length (SD 0.02). In the other 11 patients, the obstructive shelf was high and horizontal, with a mean ratio of 0.27 (SD 0.02). The difference was statistically significant (P =.001). Surgical repair was performed successfully in all 26 patients through a right ventriculotomy. CONCLUSIONS: Double-chambered right ventricle is the consequence of a high or low muscular division of the apical component of the right ventricle. The abnormal muscular bundle probably represents accentuated septoparietal trabeculations, rather than always being an abnormal moderator band.

Adolescent↗
PubMed1999

Morphologic spectrum of Ebstein's malformation: revisitation relative to surgical repair.

OBJECTIVE: Our aim was to elucidate the morphologic spectrum of Ebstein's malformation of the tricuspid valve with regard to diagnosis and the feasibility of surgical repair, in the light of the currently favored reconstructive techniques. METHODS: We examined 23 autopsied hearts. Taking the displacement of the septal and mural leaflets of the abnormal tricuspid valve as our diagnostic criterion, we focused subsequently on the location of the distorted valvular orifice and the attachment and formation of the anterosuperior leaflet. We also assessed the dimensions of the components of the right ventricle relative to the plane of the displaced valvular orifice. RESULTS: In all hearts, the septal and mural leaflets were hinged at various points within the inlet of the right ventricle. In many cases, however, these leaflets were virtually absent. The plane of the effective tricuspid valvular orifice was displaced anterosuperiorly to varying degrees. In the most severe forms, the valvular mechanism took the form of a 1-leaflet valve. The length of the functional right ventricle when compared with the left ventricle ranged proportionally from 0.6 to 1. 1 (mean, 0.9). CONCLUSIONS: Ebstein's malformation is much more than simple "downward displacement" of the leaflets. In essence, the valvular orifice is formed within the ventricular cavity at the junction of the atrialized inlet and functional ventricular components. When surgical intervention becomes necessary, it is essential to make a detailed assessment of both valvular and ventricular abnormalities.

Adolescent↗