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Biomedical subjects

Robert H Anderson

Publications and source records attributed to Robert H Anderson.

At least 37 records · Page 2Linked to original sources
PubMed2006

The diverse cardiac morphology seen in hearts with isomerism of the atrial appendages with reference to the disposition of the specialised conduction system.

Congenital cardiac malformations which include isomerism of the atrial appendages are amongst the most challenging of problems for diagnosis and also for medical and surgical management. The nomenclature for pathological description is controversial, but difficulties can be overcome by the use of a segmental approach. Such an approach sets out the morphology and the topology of the chambers of the heart, together with the types and modes of the atrioventricular, ventriculo-arterial, and venous connections. We have applied this method to a study of 35 hearts known to have isomerism of the atrial appendages. We have already published accounts of 27 of these cases, but these were reviewed for this study in the light of our increased awareness of the implications of isomerism, and 8 new cases were added. After examining, or re-examining, the morphology of every heart in detail, we grouped them together according to their ventricular topology and modes of atrioventricular connection. Then we studied the course of the specialised conduction system, by the use of the light microscope, first in each individual case, and then together in their groups. We conclude that the pathways for atrioventricular conduction in hearts with isomerism of the atrial appendages are conditioned both by ventricular topology, and by the atrioventricular connections. Based on our experience, we have been able to establish guidelines that direct the clinician to the likely location of the conduction tissues.

Atrial Appendage↗
PubMed2005

Left ventricular non-compaction: insights from cardiovascular magnetic resonance imaging.

OBJECTIVES: We aimed to test the diagnostic accuracy of cardiovascular magnetic resonance (CMR) imaging in distinguishing pathological left ventricular non-compaction (LVNC) from lesser degrees of trabecular layering seen in healthy volunteers and, in those with cardiomyopathies and concentric left ventricular hypertrophy, potential differential diagnoses. We hypothesized that pathological trabeculation could be distinguished by determining the ratio of non-compacted to compacted myocardium (NC/C ratio). BACKGROUND: Left ventricular non-compaction is characterized by a non-compacted myocardial layer in the left ventricle. Cardiovascular magnetic resonance images this layer with unprecedented quality, particularly in the ventricular apex, where echocardiography has inherent difficulties. METHODS: We analyzed magnetic resonance cine images, using the 17-segment model in 45 healthy volunteers, 25 athletes, 39 patients with hypertrophic cardiomyopathy and 14 with dilated cardiomyopathy, 17 with hypertensive heart disease, and 30 with aortic stenosis, as well as images from 7 patients previously diagnosed with LVNC whose diagnoses were supported by additional features. RESULTS: Areas of non-compaction were common and occurred more frequently in all groups studied in apical and lateral, rather than in basal or septal, segments. A NC/C ratio of >2.3 in diastole distinguished pathological non-compaction, with values for sensitivity, specificity, and positive and negative predictions of 86%, 99%, 75%, and 99%, respectively. CONCLUSIONS: Left ventricular non-compaction is diagnosed accurately with CMR using the NC/C ratio in diastole.

Adolescent↗
PubMed2005

Ventricular myocardial architecture as visualised in postmortem swine hearts using magnetic resonance diffusion tensor imaging.

OBJECTIVE: The three-dimensional arrangement of the ventricular myocardial architecture remains controversial, in part because histological assessment is difficult to achieve, while anatomic dissections are, of necessity, destructive. In this study, we describe how the use of magnetic resonance diffusion tensor imaging has permitted us to reconstruct with precision the architecture of the ventricular myocardial fibres in the post-mortem swine heart. METHODS AND RESULTS: We obtained diffusion-weighted spin-echo measurements of autopsied porcine hearts using a whole body MR system. We calculated the diffusion tensor and the corresponding eigenvectors on a voxel-by-voxel basis. This permitted us to colour code the fibres, and reconstruct them by connecting voxels in direction of the largest eigenvector. Such reconstructions show that, in the middle layer of the left ventricle, most of the fibres have a circular orientation, albeit that a far from negligible component runs in a transverse direction. With increasing distance from the epicardium, the orientation of the fibres shows a continuous change in angulation with respect to an axis normal to the epicardium. CONCLUSION: Our data presented here supports the concept that the ventricular mass is arranged as a complex three-dimensional mesh of tangential and intruding fibres. The data offers no support for the concept of a "unique myocardial band". The method has the potential to detecting deviations from this basic normal architecture, being capable of reconstructing the ventricular mass so as to assess the spatial coordinates of any single fibre strand. The technique, therefore, has major potential clinical applications in the setting of the failing or malformed heart, potentially being able to identify either systematic or regional disarray of the myocardial fibres.

Animals↗
PubMed2005

Anomalous origin of the right pulmonary artery from the ascending aorta with fibrous continuity to the pulmonary trunk.

A 1-month-old patient was brought to our institution with clinical signs of pulmonary hypertension. Cross-sectional echocardiography suggested a diagnosis of aortopulmonary window. At the time of surgery, we found that the right pulmonary artery was arising anomalously from the left side of the ascending aorta, but was also connected to the pulmonary trunk by a fibrous cord. We reimplanted the right pulmonary artery into the pulmonary trunk, closing the resultant opening in the ascending aorta by direct suture. The postoperative course was uneventful. On follow-up, the patient is asymptomatic without medication.

Electrocardiography↗
PubMed2005

Development of the atrioventricular valves: clinicomorphological correlations.

The atrioventricular valves are formed from a complex arrangement of an annulus and leaflets, supported by a subvalvar apparatus that is composed of tendinous cords and papillary muscles. Although much has been said and written about their development, the exact nature of the process has yet to be fully elucidated. We believe that this is vital, since unraveling this complex process holds the key to the understanding of many of the congenital malformations that may afflict the valves.

Heart Valve Prosthesis↗
PubMed2005

The architecture of the ventricular mass and its functional implications for organ-preserving surgery.

It has generally been accepted that the myocardial fibres within the ventricular mass are arranged in syncytial fashion, precluding the identification of discrete and isolated muscular pathways. Recently, however, an entire hypothesis for surgical treatment has been proposed on the basis of the existence of a 'ventricular myocardial band', suggesting that this arrangement in itself points to detrimental results following partial ventriculectomy. In this review, we re-state the evidence supporting the accepted concept of the ventricular mass being made up of an undefined number of wedge-shaped functional units, each of them exerting its individually programmed contribution to the global activity of the ventricular walls. The wedge-shaped units consist of bundles of individual fibres which are arranged tangentially. An important subset of fibres intrudes into the ventricular wall, thus creating oblique pathways. Their angle of intrusion varies, and can be measured at up to 30 degrees . The steeper the angle of their intrusion, the more efficiently do the fibres counteract the systolic mural thickening. The network of supporting connective tissue, nonetheless, provides the necessary steep angulation towards the endocardium. This fibrous matrix serves as continuous chain for the transmission of forces, including that in the direction from the epicardium towards the endocardium, resulting in a dilating force. We have shown, using needle force probes, that in the hypertrophic heart the dynamic equilibrium of dilating and constricting forces acts at elevated diastolic and systolic levels, because the obliquity of the fibres increases due to the thickening of the wall, and there is a concomitant increase in connective tissue, causing an increase in the forces opposing systolic mural thickening. Then, in a vicious cycle, both populations of myocardial fibres stimulate each other to hypertrophy. Eventually, coronary perfusion becomes critically impaired, with still further deposition of connective tissue. Ultimately, the vector of the dilating force comes to dominate the constricting force, and the ventricle dilates. In this setting, partial left ventriculectomy remains a functionally sound intervention, since it is capable of improving global ventricular function by improving the geometrical state of the remaining anatomic myocardial units.

Biomechanical Phenomena↗
PubMed2005

The anatomical arrangement of the myocardial cells making up the ventricular mass.

The architectural arrangement of the myocytes within the ventricular mass remains a highly contentious topic. It has recently been suggested by several distinguished surgeons that the overall myocardial structure is disposed in the form of a 'ventricular myocardial band'. There are, however, major anatomic deficiencies in this hypothesis, because the heart is formed on the basis of a modified blood vessel, rather than a collection of discrete muscular entities resembling the skeletal musculature. There is ample alternative evidence, nonetheless, already existing to provide a suitable explanation for the 'forceful reciprocal twisting' of the ventricular mass that is seen by cardiac surgeons during operative procedures. We provide here, therefore, a review of the anatomical studies we have performed separately and conjointly over a period of nearly 30 years. As before, we show that there is no anatomic evidence to support the concept of the 'ventricular myocardial band'. The overall arrangement is for the myocytes to be supported as the muscular components of a continuous and complex mass, the supporting collagenous fibrous matrix possessing epimysial, perimysial, and endomysial components. It had already been discussed at length during the previous century why there was no anatomic evidence to support the existence of separate 'muscles' within the ventricular continuum. There are no fibrous sheaths within the ventricular walls that permit the myofibres to be dissected on the basis of muscle bundles having a discrete origin and insertion, as is the case with the arrangement of the skeletal muscles. We have never sought ourselves, however, to deny the central helical nature of the overall architecture of the ventricular walls. The anatomic evidence supporting an overall helical nature for the ventricular myocardium has existed for over 150 years. All the available evidence, nonetheless, shows that these helical patterns are to be found throughout the walls, and in no way constitute a unique myocardial band.

Collagen↗