Numerical analysis of blood flow in the heart

Through cardiac looping during embryonic development, paths of flow through the mature heart have direction changes and asymmetries whose topology and functional significance remain relatively unexplored. Here we show, using magnetic resonance velocity mapping, the asymmetric redirection of streaming blood in atrial and ventricular cavities of the adult human heart, with sinuous, chirally asymmetric paths of flow through the whole. On the basis of mapped flow fields and drawings that illustrate spatial relations between flow paths, we propose that asymmetries and curvatures of the looped heart have potential fluidic and dynamic advantages. Patterns of atrial filling seem to be asymmetric in a manner that allows the momentum of inflowing streams to be redirected towards atrio-ventricular valves, and the change in direction at ventricular level is such that recoil away from ejected blood is in a direction that can enhance rather than inhibit ventriculo-atrial coupling. Chiral asymmetry might help to minimize dissipative interaction between entering, recirculating and outflowing streams. These factors might combine to allow a reciprocating, sling-like, 'morphodynamic' mode of action to come into effect when heart rate and output increase during exercise.

Asymmetric redirection of flow through the heart

This paper reviews clinical and basic science research reports and is directed toward an understanding of visceral pain, with emphasis on studies related to spinal processing. Four main types of visceral stimuli have been employed in experimental studies of visceral nociception: (1) electrical, (2) mechanical, (3) ischemic, and (4) chemical. Studies of visceral pain are discussed in relation to the use and 'adequacy' of these stimuli and the responses produced (e.g., behavioral, pseudoaffective, neuronal, etc.). We propose a definition of an adequate noxious visceral stimulus and speculate on spinal mechanisms of visceral pain.

Visceral pain: a review of experimental studies.

Background Recent advances in three-dimensional (3D) echocardiography allow us to address uniquely 3D scientific questions, such as the mechanism of functional mitral regurgitation (MR) in patients with left ventricular (LV) dysfunction and its relation to the 3D geometry of mitral leaflet attachments. Competing hypotheses include global LV dysfunction with inadequate leaflet closing force versus geometric distortion of the mitral apparatus by LV dilatation, which increases leaflet tethering and restricts closure. Because geometric changes generally accompany dysfunction, these possibilities have been difficult to separate. Methods and Results We created a model of global LV dysfunction by esmolol and phenylephrine infusion in six dogs, initially with LV expansion limited by increasing pericardial restraint and then with the pericardium opened. The mid-systolic 3D relations of the papillary muscle (PM) tips and mitral valve were reconstructed. Despite severe LV dysfunction (ejection fraction, 18±6%), only...

Insights From Three-Dimensional Echocardiography Into the Mechanism of Functional Mitral Regurgitation Direct In Vivo Demonstration of Altered Leaflet Tethering Geometry

Phase Transformations in Solids

257. Geometrical isomerism of azo-compounds

Flow patterns within the cardiac ventricles during diastolic filling have been studied in dogs and sheep by cineradiography with fine stream dye injection, and by endoscopic cinephotography. The results show that stable flow patterns occur with little evidence of gross mixing or lateral dispersion. The major flow patterns are expanding vortex systems behind the cusps of the mitral and tricuspid valves. These vortex systems appear important in normal valve dynamics.

Pattern of blood flow within the heart: a stable system.

The effects on competence of the mitral valve and the rate of development of isometric tension within the left ventricle have been studied by comparing dogs in which a papillary muscle was inactivated by ethanol injection with control dogs in which a similar injection was made into the lateral wall of the left ventricle Immediately after the alcohol injection into papillary muscle three dogs out of eleven developed mitral incompetence This does not appear consistent with the theory that papillary muscle contraction is essential for valve competence during ventricular contraction Three months after the injection nine dogs survived in each group Mitral valve dysfunction was present in five experimental, but in only one control dog and there was a trend to less efficient isometric contraction of the left ventricle in the experimental group Possible reasons for these findings are discussed and a predominant role for the papillary muscles during the isometric rather than the ejection phase of ventricular systole supported

https://physoc.onlinelibrary.wiley.com/doi/pdf/10.1113/expphysiol.1965.sp001766

The effect of papillary muscle damage on atrioventricular valve function in the left heart.

The afferent and efferent limbs of the bladder viscero-vascular reflex have been studied in cats under chloralose anaesthesia. The maximum change in arterial blood pressure in response to applied tension was obtained from the region of the trigone and bladder neck; lesser responses were obtained from all other regions of the bladder. The response to rapid bladder filling was little affectecd by hypogastric nerve section. Although it was much reduced after section of sacral posterior roots, it was not abolished until higher posterior roots had also been cut, sometimes Up to T 10.



In the presence of an intact nervous system, during the early stages of slow bladder filling hind limb vasoconstriction occurred, but there was compensatory limb vasodilation and bradycardia so that no change in blood pressure occurred. Later in the course of filling changes in blood pressure occurred and were associated with vasoconstriction in fore as well as hind limbs and subsequently tachycardia. Occasionally with extreme distension cardiac arrhythmias, such as ventricular or nodlal extra systoles, appeared. There was less compensation when filling was faster, and no compensation after baroreceptor denervation. Cardiac denervation abolished the changes in heart rate, but the circulatory changes in the limbs were unaffected.



It is concluded that bladder viscero-vascular reflexes are initiated mainly by tension changes in the region of the trigone and bladder neck; the afferent path can be either the hypogastric or pelvic splanchnic nerves, although the predominant route is the latter; and in the presence of intact baroreceptor reflexes, changes in the circulation occur early and before any alteration in the arterial blood pressure.

Duncan Taylor

Papers

257. Geometrical isomerism of azo-compounds

Pattern of blood flow within the heart: a stable system.

The effect of papillary muscle damage on atrioventricular valve function in the left heart.

Afferent pathways and efferent mechanisms in the bladder viscero-vascular reflex.

855. The chemical action of ultrasonic waves