Computed ventricular acoustic frequency

A mathematical model of the left ventricle is constructed. This model is a spherical thinwalled chamber with a radius and wall density approximately that of the left ventricle and enclosing a fluid whose pressure is that noted when heart sounds occur. The solution for the natural frequency of vibration is of the same value as that noted physiologically. Substitution of the values for the right ventricle yields similar results. The lowest natural frequencies of the idealized cardiac chamber possessing physical properties similar to a real cardiac chamber are of the same order of magnitude as the lowest significant observed cardiac frequencies. Such observation reinforces the likelihood that cardiac sounds are generated by the vibrating cardiac walls.     

Mutation of weak atrium/atrial myosin heavy chain disrupts atrial function and influences ventricular morphogenesis in zebrafish

The embryonic vertebrate heart is composed of two major chambers, a ventricle and an atrium, each of which has a characteristic size, shape and functional capacity that contributes to efficient circulation. Chamber-specific gene expression programs are likely to regulate key aspects of chamber formation. Here, we demonstrate that epigenetic factors also have a significant influence on chamber morphogenesis. Specifically, we show that an atrium-specific contractility defect has a profound impact on ventricular development. We find that the zebrafish locus weak atrium encodes an atrium-specific myosin heavy chain that is required for atrial myofibrillar organization and contraction. Despite their atrial defects, weak atrium mutants can maintain circulation through ventricular contraction. However, the weak atrium mutant ventricle becomes unusually compact, exhibiting a thickened myocardial wall, a narrow lumen and changes in myocardial gene expression. As weak atrium/atrial myosin heavy chain is expressed only in the atrium, the ventricular phenotypes in weak atrium mutants represent a secondary response to atrial dysfunction. Thus, not only is cardiac form essential for cardiac function, but there also exists a reciprocal relationship in which function can influence form. These findings are relevant to our understanding of congenital defects in cardiac chamber morphogenesis.     

The Anatomy of the Circulatory System in the Arminid Nudibranch Armina maculata Rafinesque, 1814 (Gastropoda: Opisthobranchia)

In Armina maculata the heart lies anteriorly and has a large muscular ventricle and a delicate auricle running obliquely to the antero-posterior axis. The auriculoventricular valve and the aortic valve are disposed at the anterior end of the auricle and ventricle respectively. The aortic trunk is located just anterior to the ventricle and gives off several arteries, which extend through the whole body. The main arteries are: the cephalic artery (to the buccal apparatus); the posterior artery (to the notum, digestive glands, ovotestis and renal chamber); the pedal artery (to the foot); and the genital arteries (supplying the different organs of the reproductive system). These data are compared with those of other arminacean species.     

Factors influencing the diastolic pressure-volume relation of the cardiac ventricles

The diastolic pressure-volume relationship of either ventricle is a direct measure of the properties of its chamber. While this relation is, to a large extent, determined by the myocardium and its mechanical properties, there are a number of physiological factors that are also capable of influencing the diastolic pressure-volume-relation. This review examines our current understanding of the importance of a number of these factors with respect to the diastolic properties of the chamber. The factors discussed are heart rate, arterial pressure, coronary perfusion pressure, the pericardium, and the mechanical interplay between ventricles. The influence of heart rate, arterial pressure, and coronary perfusion pressure can be considered as minor provided they remain within their normal physiological range. On the other hand, the diastolic pressure-volume relation is highly dependent on the volume in the other ventricle, particularly in the presence of the pericardium. An awareness and understanding of the interrelationship between these factors and the diastolic pressure-volume relation is essential when evaluating the properties of the chamber and when such pressure-volume data are used to estimate the mechanical properties of the myocardium.     

Functional modulation of cardiac form through regionally confined cell shape changes

Developing organs acquire a specific three-dimensional form that ensures their normal function. Cardiac function, for example, depends upon properly shaped chambers that emerge from a primitive heart tube. The cellular mechanisms that control chamber shape are not yet understood. Here, we demonstrate that chamber morphology develops via changes in cell morphology, and we determine key regulatory influences on this process. Focusing on the development of the ventricular chamber in zebrafish, we show that cardiomyocyte cell shape changes underlie the formation of characteristic chamber curvatures. In particular, cardiomyocyte elongation occurs within a confined area that forms the ventricular outer curvature. Because cardiac contractility and blood flow begin before chambers emerge, cardiac function has the potential to influence chamber curvature formation. Employing zebrafish mutants with functional deficiencies, we find that blood flow and contractility independently regulate cell shape changes in the emerging ventricle. Reduction of circulation limits the extent of cardiomyocyte elongation; in contrast, disruption of sarcomere formation releases limitations on cardiomyocyte dimensions. Thus, the acquisition of normal cardiomyocyte morphology requires a balance between extrinsic and intrinsic physical forces. Together, these data establish regionally confined cell shape change as a cellular mechanism for chamber emergence and as a link in the relationship between form and function during organ morphogenesis.     

Systolic pressure gradients between the wall of the left ventricle, the left ventricular chamber, and the aorta during positive inotropic states: implications for left ventricular efficiency

To study systolic pressure gradients developed between the left ventricular wall, its chamber, and the aortic root, in one group of dogs left ventricle ventral wall intramyocardial pressure, left ventricular outflow tract pressure, and aorta pressure were compared with aortic flow as well as left ventricular dimension changes during control conditions as well as during positive intropic states induced by isoproterenol, stellate ganglion stimulation, and noradrenaline. In another group of dogs systolic pressures in the ventral wall of the left ventricle, the main portion of the left ventricular chamber, and the aorta were compared with aortic flow during similar interventions, before and after the administration of phentolamine. Pressure gradients between the wall of the left ventricle and the outflow tract of the left ventricle were minimal during control states, but during the three positive inotropic states were increased significantly. In contrast, pressure gradients between the outflow tract of the left ventricle and the aortic root were insignificant during positive inotropic states; those between the wall and main portion of the chamber were only significantly different during left stellate ganglion stimulation. The data derived from these experiments indicate that useful peak power output of the left ventricle (systolic aortic pressure X flow) is unchanged following isoproterenol infusion, but is increased by stellate ganglion stimulation and noradrenaline. The useful peak power output index (an index of left ventricular efficiency derived by dividing useful peak power output by peak intramyocardial pressure) was reduced more by isoproterenol than the other two interventions.(ABSTRACT TRUNCATED AT 250 WORDS)     

Right bundle branch block pattern during right ventricular permanent pacing: Is it safe or not?

The present case report describes a patient with dual chamber pacemaker whose surface ECG demonstrated paced right bundle branch block pattern suggesting a malpositioned ventricular lead in the left ventricle. However, diagnostic work-up revealed that the lead was appropriately located in the right ventricular apex. Diagnostic maneuvers and clues for differentiating safe right bundle branch block pattern during permanent pacing are thoroughly revisited and discussed within the article.     

Optimization of the method of x-ray contrast left ventriculography

The authors propose their modification of the method of left ventriculography (VG) (substitution of direct VG for iv VG with an injection of a contrast medium into the right atrial chamber in combination with continuous monitoring of pressure in the LV chamber). Altogether 23 patients with a doubtful diagnosis of CHD were investigated by coronography, direct VG and iv biventriculography. All images of the left ventricle were subjected to computerized multiframe analysis. A conclusion is that the modified method is more preferable than direct VG.     

Anatomic features of the base of hearts with a solitary ventricle

Twenty-eight preparations of hearts having three chambers with two atria have been investigated. The age of the deceased was from several hours up to 21 years. Absence of the interventricular septum results in a complex rearrangement of the vessels in the basis cordis. Only in three cases the aorta and the pulmonary trunk situated typically, in others there was a complete transposition. Since the only ventricle, as a rule, is accompanied with a presence of a small chamber--"emissary", the topography of the vessels is mainly determined by the latter. The "emissary" is situated either along the right or left contour of the base of the common ventricle, its dimensions are variable. When the "emissary" is situated along the anterior-right contour of the basis cordis, as a rule, the aorta takes origin from the latter, its bulb is situated ventrally, initial parts of the venous arteries are visible. The cuspides of the aortal valve sag into the "emissary" lumen. When the aorta is situated normally, it can get off the cavity of the common ventricle, or the "emissary". The state of the children is determined first of all by the character of the pulmonary circulation. If there is no stenosis in the pulmonary trunk and it takes its origin from the common ventricle, or from the "emissary" of a great size, the prognosis is more favourable. Cases of early death among the children are connected with small size of the "emissary" chamber and a small diameter of the pulmonary trunk.(ABSTRACT TRUNCATED AT 250 WORDS)     

Microphotometric determination of structure-bound oxidoreductase activities avoiding nothing-dehydrogenase artefacts: succinate dehydrogenase

 A tetrazolium-based microphotometric method has been devised for the determination of structure-bound dehydrogenase activities with correction for nothing-dehydrogenase artefacts. The method is based on the microphotometric recording of maximum reaction rates in a simple incubation chamber and consists of two successive measurements on the same section, the first in the absence and the second in the presence of the substrate. Following the first measurement, the substrate-free medium is quickly exchanged with the substrate-containing medium and a second measurement is taken. Subtraction of the first from the second reaction rate yields the enzyme activity corrected for nothing-dehydrogenase. Measurements of succinate dehydrogenase (SDH) in skeletal muscle fibres, liver, cardiac atrium and ventricle demonstrate the feasibility of the method. Measurements on the extensor digitorum longus muscle of rat reveal a range of up to fivefold differences in SDH activity within the fibre population of this muscle. Accepted: 11 April 1997     

A Three-Dimensional Analytical (Rheological) Model of the Human Left Ventricle in Passive-Active States: Nontraumatic Determination of the In Vivo Values of the Rheological Parameters

In this paper a three-dimensional continuum model of a mammalian left ventricle is formulated. The stresses in the model satisfy the conditions of zero stress on the outer (epicardial surface-representing) boundary. The strains of the model are obtained from the actual dynamic geometry measurements (obtained from cineangiocardiography). Since the left ventricular muscle is incompressible, the dilatational strain is zero and hence the (three-dimensional) deviatric stress components are related to the corresponding strain components by Maxwell and Voigt rheological model analogues of one-dimensional systems; the parameters of the model are series and parallel elastic (SE, PE) elements and the contractile element (CE) (representing the sarcomere). The incorporation of the rheological features of the cardiac muscle into the three-dimensional constitutive equations (for the three-dimensional continuum model of the left ventricle) is a feature of this paper. A procedure is presented to determine the parameters of the constitutive equations (i.e., the SE, PE, and the parameters of the force-velocity relation for the CE) for the left ventricle of a subject from data on the dimensions and chamber pressure of the left ventricle. The values of these parameters characterize the rheology of the left ventricular muscle of the subject. In order to demonstrate clinical application of the analyses, in vivo data of the subjects' left ventricular pressure and dimensions are obtained, and the analyses are applied to the data to determine (for each subject) the values and characteristics of the elastic elements and CEs.     

Dynamics of the mass of the right ventricle of the heart and concentration of RNA in it during the process of "reverse" development of hypertrophy]

Experiments were conducted on male rats, 250-300 g in weight. Adaptation to high altitude hypoxia was created by placing the animals daily for 5 hours, into an altitude chamber, at an "altitude" of 6000 m. The degree of hypertrophy of the right ventricle and its RNA content was studied after 20 days of adaptation, as well as 2, 10, 20 and 40 days after cessation of hypoxia. Twenty days after the beginning of adaptation the muscle mass of the right ventricle the RNA concentration and amount in it was found to increase considerably. After cessation of hypoxia half of the acquired increase in the ventricle muscle mass was lost in 10 days, and half of the acquired increase in the RNA--as soon as in 2 days. Forty days after cessation of hypoxia the right ventricle mass and its RNA content in the adapted animals did not differ from the same indices in control rats.     

Performance of the isolated and perfused working heart of the teleostConger conger: study of the inotropic effect of prostacyclin

Summary An in vitro preparation of the heart of the teleostConger conger, isolated without the pericardium, was set up. The procedure allowed subambient pressures to develop in the perfusion chamber during contraction, mimicking the in vivo situation with the pericardium intact. The ventricle produced a cardiac output of about 15 ml·min^-1·kg wet body weight^-1 at subambient input pressure, and was able to double the stroke work with an increase of preload up to about 0.2 kPa. Using this preparation it was found that prostacyclin has a positive inotropic effect on the atrium and ventricle, but it does not affect the heart rate. Semilogarithmic doseresponse curves of prostacyclin on the atrium are reported, showing a threshold concentration of about 10^-9 M. The isolated and perfusedConger conger heart provides a useful model for a detailed analysis of the action of prostacyclin on myocardial contractility.     

Regional stress in a noncircular cylinder.

Several mathematical formulas are presented for estimating regional average circumferential stress and shear stress in a thick-wall, noncircular cylinder with a plane of symmetry. The formulas require images of exterior and interior chamber silhouettes plus surface pressures. The formulas are primarily intended for application to the left ventricle in the short axis plane near the base (where the meridional radius of curvature is normally much larger than the circumferential radius of curvature) and to blood vessels. The formulas predict stresses in a variety of chambers to within 3% of finite element values determined from a large-scale structural analysis computer program called ANSYS.     

Optical chamber system designed for microscopic observation of living cells under extremely high hydrostatic pressure

A novel pressure chamber system has been developed for the study of living cells under conditions of extremely high hydrostatic pressure up to 100 MPa (1 atm = 0.101325 MPa). The temperature in the chamber is thermostatically controlled in the range from 2 degrees to 80 degrees C. Two high-pressure pumps are employed for continuous perfusion of the chamber with culture medium and a chemical solution under high hydrostatic pressure conditions. The chamber has a 2-mm-thick glass window 2 mm in diameter, with a minimum working distance of 3.8 mm. The chamber system is designed to be adaptable to a variety of microscopic and imaging techniques. Using this chamber system, we successfully carried out real-time observations of elongated Escherichia coli and rounded HeLa cells under pressure.     

Simulation of Left Atrial Function Using a Multi-Scale Model of the Cardiovascular System

During a full cardiac cycle, the left atrium successively behaves as a reservoir, a conduit and a pump. This complex behavior makes it unrealistic to apply the time-varying elastance theory to characterize the left atrium, first, because this theory has known limitations, and second, because it is still uncertain whether the load independence hypothesis holds. In this study, we aim to bypass this uncertainty by relying on another kind of mathematical model of the cardiac chambers. In the present work, we describe both the left atrium and the left ventricle with a multi-scale model. The multi-scale property of this model comes from the fact that pressure inside a cardiac chamber is derived from a model of the sarcomere behavior. Macroscopic model parameters are identified from reference dog hemodynamic data. The multi-scale model of the cardiovascular system including the left atrium is then simulated to show that the physiological roles of the left atrium are correctly reproduced. This include a biphasic pressure wave and an eight-shaped pressure-volume loop. We also test the validity of our model in non basal conditions by reproducing a preload reduction experiment by inferior vena cava occlusion with the model. We compute the variation of eight indices before and after this experiment and obtain the same variation as experimentally observed for seven out of the eight indices. In summary, the multi-scale mathematical model presented in this work is able to correctly account for the three roles of the left atrium and also exhibits a realistic left atrial pressure-volume loop. Furthermore, the model has been previously presented and validated for the left ventricle. This makes it a proper alternative to the time-varying elastance theory if the focus is set on precisely representing the left atrial and left ventricular behaviors.